Why I hate the space shuttle
Gary Coffman
> Personally, I think that more attempts to make the results (primarily
>the hi-res color pictures, of course) of Viking/Voyager available to everyone
>at low cost would do a great deal to stir up interest. Do you really think
>that watching a few astronauts recover a satellite excites the public as
>much as looking as superdetailed pictures of Saturn's rings? I don't.
I do. The public likes pictures from space, but only if there is a
human they can relate to in the foreground. Otherwise, most think
the slick network graphics are better than the box brownie pictures.
Those interest mainly the astronomer wannabes, and they aren't
representative of the general public.
Gary
--
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Gary Coffman
>In article <1993Jul30.1...@aio.jsc.nasa.gov> m...@superman.jsc.nasa.gov writes:
>
>>Don't let anyone kid you, military flying is still quite dangerous
>
>It is indeed. On the other hand, civil airliners are safer than cars.
>Our dangerous launchers are built like fighters so maybe we would do
>better if we built our spacecraft like civil aircraft instead of like
>fighters.
You mean with *big* wings instead of being a brick with a rocket on
it's tail?
George William Herbert
>a...@iti.org (Allen W. Sherzer) writes:
>>m...@superman.jsc.nasa.gov writes:
>>
>>>Don't let anyone kid you, military flying is still quite dangerous
>>
>>It is indeed. On the other hand, civil airliners are safer than cars.
>>Our dangerous launchers are built like fighters so maybe we would do
>>better if we built our spacecraft like civil aircraft instead of like
>>fighters.
>
>You mean with *big* wings instead of being a brick with a rocket on
>it's tail?
No, with large enough margins that it can be designed by a team
of say twenty instead of two to twenty thousand, and simple enough
that normal industrial procedure training will suffice for the (small)
ground crew at launch site unless something breaks, in which
case you replace the item and ship it off to specialty shop for repair.
-george william herbert
Retro Aerospace
Gary Coffman
Ok, that was meant as a jab, partially in fun, at Allen's VTOL mania.
But let's examine *margins*. SSTO has the lowest margin of any launcher.
In fact, some still question whether it's reached breakeven. We'll know
if and when DC-Y reaches orbit with *any* residual payload capacity.
By contrast, large cargo aircraft operate with payload masses near
the unladen mass of the aircraft. That's margin. Margin can be traded
for redundancy, reserve, and all the other good things that make
a vehicle reliable.
George William Herbert
>>>You mean with *big* wings instead of being a brick with a rocket on
>>>it's tail?
>>
>>No, with large enough margins that it can be designed by a team
>>of say twenty instead of two to twenty thousand, and simple enough
>>that normal industrial procedure training will suffice for the (small)
>>ground crew at launch site unless something breaks, in which
>>case you replace the item and ship it off to specialty shop for repair.
>
>Ok, that was meant as a jab, partially in fun, at Allen's VTOL mania.
>But let's examine *margins*. SSTO has the lowest margin of any launcher.
>In fact, some still question whether it's reached breakeven. We'll know
>if and when DC-Y reaches orbit with *any* residual payload capacity.
>By contrast, large cargo aircraft operate with payload masses near
>the unladen mass of the aircraft. That's margin. Margin can be traded
>for redundancy, reserve, and all the other good things that make
>a vehicle reliable.
Yes, but they're not designing it with a team of twenty.
They're asking for billions (if I recall) in development cost.
I was talking about a whole different environment, the Big Dumb
environment.
DC will, I believe, end up with positive paylod. Why? I see really big
margins right now in their structures when I talk to MacDac people
about it. Remember that they're designing this thing for lots of
flights, and that means keeping an eye on long-term fatigue properties
and adjusting stress downwards correspondingly. If they limit the
flights per airframe to 100 (from say 500-1000) that reduces the
limiting stresses by a laaarge margin, and you can just reuse the flight
systems on the next airframe (or design them to 100 flights).
Plus, last I saw, they had a margin of roughly half the described
payload or something like 15% of the dry mass. Which is pretty
hefty, if you ask me.
The one thing that won't be cheap is doing development right to
realize the promise that the concept seems to hold. But it won't
be as expensive as Shuttle was, either to develop or to fly,
and is in my humble but quotable opinion less of a technical risk
today than Shuttle was in 1970-72.
The only question is wether they can get someone to pay the initial
up-front costs to design the thing and work the kinks out. Big Dumb
vehicles (at least should) have an advantage here, with massive margins
and low initial design and qualification costs. Though it may turn
out to be competition for what I'm trying to do, I support DC because
it may turn out to be a better way of doing business. I hope that
they find someone to pay for developing it and that it works.
Paul Dietz
>>Ok, that was meant as a jab, partially in fun, at Allen's VTOL mania.
>>But let's examine *margins*. SSTO has the lowest margin of any launcher.
>
>DC will, I believe, end up with positive paylod. Why? I see really big
>margins right now in their structures when I talk to MacDac people
>about it.
...
>Plus, last I saw, they had a margin of roughly half the described
>payload or something like 15% of the dry mass. Which is pretty
>hefty, if you ask me.
...
One additional consideration (which has been mentioned here before, by
Bruce Dunn, I think). If this SSTO concept fails to have enough
payload, it can be augmented with a first stage. This adds the cost
of mating a new stage on each flight and restricts the launch sites,
but should not double the complexity of the vehicle. The upper stage
already has to have the ability to start in flight.
Even a fairly modest first stage could greatly increase the payload,
even if the SSTO does meet design goals. Assuming the payload in the
SSTO is 30% of the total burnout mass, if one adds a first stage that
enables one to double the burnout mass then the payload increases by
more than a factor of four.
Doubling the burnout mass would involve a first stage reaching perhaps
2.5 km/s. This can be easily achieved with a LOX/hydrocarbon stage of
modest performance (say, the ever-popular :-) ballistic
sea-recoverable first stage). This first stage can have larger
margins and more conservative design than the upper stage, so it
should be easier to design and build (its propellants would also be
cheaper).
Paul F. Dietz
di...@cs.rochester.edu
Henry Spencer
>>Our dangerous launchers are built like fighters so maybe we would do
>>better if we built our spacecraft like civil aircraft instead of like
>>fighters.
>
>You mean with *big* wings instead of being a brick with a rocket on
>it's tail?
No, with enough engines that they can survive loss of 1/2 of them instead
of only 1/4 like a 747. (1/2 is nominally survivable on a 747, but note
what happened in Amsterdam.)
There are airliners that don't have big wings. (Hint: Chinook.)
--
Altruism is a fine motive, but if you | Henry Spencer @ U of Toronto Zoology
want results, greed works much better. | he...@zoo.toronto.edu utzoo!henry
Bruce Hoult
> One additional consideration (which has been mentioned here before, by
> Bruce Dunn, I think). If this SSTO concept fails to have enough
> payload, it can be augmented with a first stage. This adds the cost
> of mating a new stage on each flight and restricts the launch sites,
> but should not double the complexity of the vehicle. The upper stage
> already has to have the ability to start in flight.
You *really* don't want to do that as part of normal operations, but I
suppose it could be a useful capability if one prospective payload in a
hundred is three times as heavy as you normally take but will fit inside
the ship -- much as JATO units are used to let C-130's lift heavy loads
from short strips. You sure don't want to have to use them every takeoff.
Dave Tholen
> No, with enough engines that they can survive loss of 1/2 of them instead
> of only 1/4 like a 747. (1/2 is nominally survivable on a 747, but note
> what happened in Amsterdam.)
When United 811 ripped open out of Honolulu a few years back, both starboard
engines were damaged, and the jet landed safely on just the two port engines.
Must have been some torque for the pilots to fight.
And I recall reading about a United trans-Pacific flight to Tokyo even
longer ago that had first one engine shut down, then a second, and I believe
a third, though I recall a second engine was restarted for landing, but it
may have been flying on one engine there for a while. Does somebody have a
better memory than me about this incident, and if true, what was determined
to be the cause?
Both 747s, by the way.
Steinn Sigurdsson
Henry Spencer writes:
> No, with enough engines that they can survive loss of 1/2 of them instead
> of only 1/4 like a 747. (1/2 is nominally survivable on a 747, but note
> what happened in Amsterdam.)
...
And I recall reading about a United trans-Pacific flight to Tokyo even
longer ago that had first one engine shut down, then a second, and I believe
a third, though I recall a second engine was restarted for landing, but it
may have been flying on one engine there for a while. Does somebody have a
better memory than me about this incident, and if true, what was determined
to be the cause?
That sounds like the one that flew into the Pinatubo plume?
There was at least one 747 on a trans-Pacific flight that lost
three engines when it ran into the plume and made it out
with one restart.
Both 747s, by the way.
| Steinn Sigurdsson |I saw two shooting stars last night |
| Lick Observatory |I wished on them but they were only satellites |
| ste...@lick.ucsc.edu |Is it wrong to wish on space hardware? |
| "standard disclaimer" |I wish, I wish, I wish you'd care - B.B. 1983 |
George William Herbert
>That sounds like the one that flew into the Pinatubo plume?
>There was at least one 747 on a trans-Pacific flight that lost
>three engines when it ran into the plume and made it out
>with one restart.
One 747 that hit the Pinatubo plume lost all four engines for some
time (got them lit at 9,000 ft or something, after gliding down
from 40,000). Numerous 747s have had engine failures (my father
was in one that had it's #3 engine's hot section blow up shortly
after takeoff, it was exciting and he has some neat photos of the
plane circling and dumping fuel...). I've seen a few cases where
engines fell off cleanly.
I can think of two large planes that crashed as a result of a
single engine failure&seperation: the 747 in Europe and the
DC-10 which had a motor fall off in (Detroit? Chicago?).
I can think of numerous other examples where failures, including
multiple or total failures, were survived. Like the DC-10
which had all three engines oil pump seals incorrectly
installed and limped back into Miami with one smoking engine
and two dead engines (incorrectly reported earlier in this
thread as a 747).
Henry's just being a curmdugeon. 8-) While it's possible for
a single engine failure to cause an airliner to crash, it
nearly never happens. Airliners lose engines in flight
on a daily basis. I'll settle for launch vehicles that
have equivalent redundancy.
Henry Spencer
>Henry's just being a curmdugeon. 8-) While it's possible for
>a single engine failure to cause an airliner to crash, it
I'll admit to having been a bit grumpy when I posted that... :-)
Note, though, a more general point: when an airliner loses *all* its
engines, it better get at least one of them relit, or it's going to
crash unless the gods are really smiling. When you're out over the
Pacific at night and run into a Pinatubo ash cloud, the engines are
at least as important as the wings -- without engines, wings just
postpone the inevitable briefly.
Sure, in particularly favorable conditions -- nearby long hard-surface
runway, pilot who flies gliders as a hobby -- an airliner can survive
an unpowered landing. And in particularly unfavorable conditions, even
having two or three surviving engines won't help enough. But in the
average situation, one engine out is okay and all engines out is lethal,
wings or no wings.
George William Herbert
>I'll admit to having been a bit grumpy when I posted that... :-)
>
>Note, though, a more general point: when an airliner loses *all* its
>engines, it better get at least one of them relit, or it's going to
>crash unless the gods are really smiling. When you're out over the
>Pacific at night and run into a Pinatubo ash cloud, the engines are
>at least as important as the wings -- without engines, wings just
>postpone the inevitable briefly.
True. However, all-engine failures are pretty rare in both planes
and rockets. Offhand, I remember that one 747 in the ash cloud,
(very nearly) the DC-10 with the oil leaks in all 3 engines, the
(727?) from columbia that ran out of fuel and crashed in NY, and the
Canadair 767 which suffered from metric-conversion induced fuel
starvation but lucked out and landed intact on a racetrack. 8-)
>Sure, in particularly favorable conditions -- nearby long hard-surface
>runway, pilot who flies gliders as a hobby -- an airliner can survive
>an unpowered landing. And in particularly unfavorable conditions, even
>having two or three surviving engines won't help enough. But in the
>average situation, one engine out is okay and all engines out is lethal,
>wings or no wings.
Of the four cases I can recall, three landed intact, two of them
at airfields. This is reasonably good odds.
Of course, in rockets the equivalent failure modes would have been
2/4 crashes; the Pinatubo cloud 747 and the DC-10 analog situations
are survivable, but any rocket is gonna come down hard if you run out
of fuel, no matter what's underneath you or what hobbies you have.
An analogous situation would be non-restartable failures in all motors.
Still pretty good odds. Assuming you have restart capability in your
motors, and that they're seperated enough that a catastropic 1-engine
failure doesn't cascade, you can make a pretty safe rocket.
Pat
then a loss of control event.
Even if you are 1,000 miles off shore, you can arrange a decent
ditch into the water and radio for Emergency assistance on the way down.
I don't think i'd want to float for 12 hours waiting for pick up but
it will happen sometime.
to someone else i hope.
Loss of control events are usually so sudden, that little can be
done to mitigate the situation, like the two DC-10's that lost their
tail section hydraulics to a cargo hatch failure, or
the 747 that lost it's left side controls to a lightning strike.
(it was an Iran Air jet in the 70's).
pat
PS a rocket losing power on descent phase, may still be able to
arrange some sort of reasonable water ditch.
--
I don't care if it's true. If it sounds good, I will
publish it. Frank Bates Publisher Frank Magazine.
Gary Coffman
>There are airliners that don't have big wings. (Hint: Chinook.)
I thought those big things on top that go round and round were called
rotary wings.
Steve Derry
: In <CBBHC...@zoo.toronto.edu> he...@zoo.toronto.edu (Henry Spencer) writes:
: >
: >Note, though, a more general point: when an airliner loses *all* its
: >engines, it better get at least one of them relit, or it's going to
: >crash unless the gods are really smiling. When you're out over the
: >Pacific at night and run into a Pinatubo ash cloud, the engines are
: >at least as important as the wings -- without engines, wings just
: >postpone the inevitable briefly.
: True. However, all-engine failures are pretty rare in both planes
: and rockets. Offhand, I remember that one 747 in the ash cloud,
: (very nearly) the DC-10 with the oil leaks in all 3 engines, the
: (727?) from columbia that ran out of fuel and crashed in NY, and the
: Canadair 767 which suffered from metric-conversion induced fuel
: starvation but lucked out and landed intact on a racetrack. 8-)
There was also a Boeing 737 that lost both engines in a hailstorm at 16,000
feet while approaching New Orleans (I believe it was 1987). After several
unsuccessful restart attempts, the crew prepared to ditch in the Intracoastal
Waterway. At that point the crew noticed an abandoned grass landing strip
and successfully landed there, without casualties to the passengers or the
aircraft.
: >Sure, in particularly favorable conditions -- nearby long hard-surface
: >runway, pilot who flies gliders as a hobby -- an airliner can survive
: >an unpowered landing. And in particularly unfavorable conditions, even
: >having two or three surviving engines won't help enough. But in the
: >average situation, one engine out is okay and all engines out is lethal,
: >wings or no wings.
But having wings can give you more flexibility in working the conditions to
your advantage, as in the case above. Of course, rocket engines would not
have been vulnerable to hail ingestion.
--
Steve Derry
<s.d....@larc.nasa.gov>
Henry Spencer
>Even if you are 1,000 miles off shore, you can arrange a decent
>ditch into the water and radio for Emergency assistance on the way down.
Assuming you've got good weather and relatively calm seas, that is.
In the best of conditions, ditching is a desperate-emergency procedure
involving substantial risk of a crash. Do it at night in bad weather
into high seas, and the chances of surviving it approach zero.
>I don't think i'd want to float for 12 hours waiting for pick up but
>it will happen sometime.
At 1000 miles out, 12 hours is very optimistic, unless there is shipping
nearby. 1000 miles is 2-3 days' steaming for all but the fastest ships.
Henry Spencer
>>There are airliners that don't have big wings. (Hint: Chinook.)
>
>I thought those big things on top that go round and round were called
>rotary wings.
They aren't big by wing standards.
Dan Newman
>In article <CB9n5...@zoo.toronto.edu> he...@zoo.toronto.edu (Henry Spencer) w
>rites:
>>There are airliners that don't have big wings. (Hint: Chinook.)
>
>I thought those big things on top that go round and round were called
>rotary wings.
>
be the most expensive aircraft it ever operated, had to keep about half
its fleet in storage because it couldn't keep up the supply of spares
and highly trained technicians, and in general had life cycle costs
orders of magnitude greater than the initial purchase price indicated.
If this is meant to exemplify DC-X's future, MD should stop work now.
Dan Newman d...@aero.ae.su.OZ.AU
Department of Aeronautical Engineering Ph : 61 2 692 2347
University of Sydney Fax: 61 2 692 4841
Sydney NSW 2006
AUSTRALIA
S.H.
>>>There are airliners that don't have big wings. (Hint: Chinook.)
>>I thought those big things on top that go round and round were called
>>rotary wings.
>Bad choice of flight vehicle. The RAAF found its Chinooks (C models) to
>be the most expensive aircraft it ever operated, had to keep about half
>its fleet in storage because it couldn't keep up the supply of spares
>and highly trained technicians, and in general had life cycle costs
>orders of magnitude greater than the initial purchase price indicated.
It was because highly trained technicians simply did not do any better
job than technicians who had min experience but can adapitively learn to
perform well. Quite often, many experts did their work to *demonstrate*
their techniques instead of solving problem.
>If this is meant to exemplify DC-X's future, MD should stop work now.
What is MD ?
There must be lots of gain back for them if they did not stop.
>Dan Newman d...@aero.ae.su.OZ.AU
>Sydney NSW 2006
Gary Coffman
>In article <1993Aug6.1...@ke4zv.uucp> ga...@ke4zv.UUCP (Gary Coffman) writes:
>>>There are airliners that don't have big wings. (Hint: Chinook.)
>>
>>I thought those big things on top that go round and round were called
>>rotary wings.
>
>They aren't big by wing standards.
The true determinant of wing size is swept area. Since the rotary
wing travels faster than the vehicle, it's swept area is bigger than
a fixed wing. So these *are* big by wing standards.
Gary Coffman
>In article <23sasq$p...@agate.berkeley.edu> g...@soda.berkeley.edu (George William Herbert) writes:
>>Henry's just being a curmdugeon. 8-) While it's possible for
>>a single engine failure to cause an airliner to crash, it
>>nearly never happens...
>
>I'll admit to having been a bit grumpy when I posted that... :-)
>
>Note, though, a more general point: when an airliner loses *all* its
>engines, it better get at least one of them relit, or it's going to
>crash unless the gods are really smiling. When you're out over the
>Pacific at night and run into a Pinatubo ash cloud, the engines are
>at least as important as the wings -- without engines, wings just
>postpone the inevitable briefly.
>
>Sure, in particularly favorable conditions -- nearby long hard-surface
>runway, pilot who flies gliders as a hobby -- an airliner can survive
>an unpowered landing. And in particularly unfavorable conditions, even
>having two or three surviving engines won't help enough. But in the
>average situation, one engine out is okay and all engines out is lethal,
>wings or no wings.
Actually, on the basis that any landing you can walk, or swim, away
from being a good one, winged vehicles have a real edge over rocks,
err rockets. With all engines out, many aircraft can ditch successfully,
and most can touch down on any spot of fairly level ground. The *plane*
may sustain major damage, but as long as the contents survive, that's
relatively unimportant. Three of four loss of power incidents with
general aviation aircraft in Georgia in the last month have resulted
in no fatalities. The one exception was in a thunderstorm the pilot
should have avoided. In fact, engine out procedures are a required part
of pilot training. When flying VFR, a pilot should always have an
emergency landing site in mind within his gliding range.
Pat
Pre shuttle, all US manned spacecraft seemed to do a nice
un powered water ditch, with only the notable loss of one capsule.
the soviets doa nice unpowered land ditch. wings don't seem
that vital for spacecraft.
h.hil...@genie.geis.com
> George William Herbert <g...@soda.berkeley.edu>
writes:
> True. However, all-engine failures are pretty rare in both planes
> and rockets. Offhand, I remember that one 747 in the ash cloud,
> (very nearly) the DC-10 with the oil leaks in all 3 engines, the
> (727?) from columbia that ran out of fuel and crashed in NY, and the
> Canadair 767 which suffered from metric-conversion induced fuel
> starvation but lucked out and landed intact on a racetrack. 8-)
engine failures of the 20th century, but I am quite sure there have
been at least two caused by volcanic ash clouds (one in Alaska). I
have no recollection of it being a DC-10 in which the mechanic
erroneously assumed that the drain plugs came with "o" rings
installed (I would have guessed B-727, it is for sure that there were
three engines, so it could have been a L-1011, but DC-10 does not
compute.)
Some others, there was one, 727 this time for sure, enroute from
Florida to NYC in which the flight engineer noticed that the engines
were not doing well, and turned on heaters and that did them all in
(low NPSP as we say in the biz). There was a Delta flight, I don't
remember the type, which had just taken off from LAX when the
pilot, for some reason difficult to imagine, got the wrong switch, and
shut down all engines. There was one that really was a DC-10 in
which a shattered compressor disk chopped all three hydraulic
systems at a point where they were all in a knot, resulting in a corn
field landing (Iowa?) and, there was a relatively recent incident in
Great Britain, a B-737, in which the crew noticed that one engine was
in trouble, but the pilot apparently got confused about "left looking
forward" or "left looking aft" (maybe "port" and "starboard" were not
such dumb ideas) and cut the wrong one. Then there were multiple
recent 747's in which the separation of one engine caused damage to
a second one.
I am not sure what the message in all this is, relative to rocket
safety, but something that is common to many of them is that in
airplanes, the engines all have a common mode failure at the "top
level" in the form of the crew.
The volcanic ash is somewhat of a special case, I think.
And, the one DC-10 is the only airplane that I can think of in which
there was a direct and prompt cause and effect relationship between
the failure of one engine, and the loss of more than one safety critical
system. (Sometimes there is a "delayed and/or indirect" relationship,
i. e. fire, or loss of thrust causing ground contact.)
> but any rocket is gonna come down hard if you run out
> of fuel, no matter what's underneath you or what hobbies you have.
Rocket engines are something that I know more about, in my spare
moments, I am constructing the "Ultimate Data Base" which has
everything known about every rocket engine failure. Desk top size.
In discussing fuel depletion, one should remember that rockets
seldom have seldom had intermediate landing points available, and
no airplane is likely to make its intended destination if it
unexpectedly runs out of fuel, either. Unexpected propellant
depletion, is, perhaps unexpectedly, not all that rare as a failure
mode in rockets, and perhaps more expectedly, if you run out of
propellant when you didn't expect too, it is often hard to figure out
why.
I think that consideration of the effects of propellant depletion (we
rocket people do not like to say "fuel" which gets complicated) makes
a very interesting, and important, point, about engine reliability in
the two cases.
There is no question that rocket engines fail more often, and there is
also no question that they fail more often fail spectacularly than do
aircraft engines (per "equivalent flight"). There is a lot of question as
to why, and whether there "should" but this difference.
In the case of propellant depletion, early Rocketdyne engines (of the
type used on Thor, Atlas, Jupiter, etc.) had a "design feature" that in
that eventuality, they didn't "wimp out" and quit running, as you
might expect your automobile engine or an airplane engine to do,
but, rather, they shattered the turbine disk, which threw large
chunks, sometimes through propellant tanks, etc.
In many comparable situations, I have heard comments of "So what?'
If you miss the target, everything else is the same." I have also heard
comments along the lines that "It is easy to explain a spectacular
explosion to the 'higher up's' than an engine that 'wimps out'."
I don't know that either idea had anything to do with this particular
failure mode, but after the first Thor ran out of propellant less than
a second before expected cutoff, and became a fireball rather than a
just having a slightly short range, a redesign was made that caused
the engine to "degrade gracefully." I don't think even one failure like
that of an airplane engine would have been necessary to have made
the point.
The idea of engine failures that only cause the loss of thrust, and
ones that cause the loss of other engines, or other stuff, has been
called "correlation" in the engine trade (I assume that is just an
euphemism, the idea being how many times engine two goes when
engine one does, and is therefore "correlated.") Other people have
tried to talk about "catastrophic" engine failures. That doesn't work
at all. For most rockets in the "historical data base" there was no
engine out capability, and therefore every failure was "catastrophic."
(And, there is, conceptually, some vehicle, somewhere, that could
withstand any loss of a single engine, no matter what it did.)
Correlation is very difficult to deal with, as it is a "rare" event, that
only happens after another "rare" event, the fact that the engine
stops running to begin with. And, hopefully, it never happens the
same way twice, since all known correlation modes get fixed.
Estimates for rocket engines run as high as 35 percent of all failures,
but 5 percent is more reasonable, in my opinion, and has been
discussed as a design goal for future engines. Aircraft engines have
rates much less than one percent.
> Still pretty good odds. Assuming you have restart capability in
> 1-engine failure doesn't cascade, you can make a pretty safe
rocket.
number of things that one can do to make them safer. engine
separation is one of them.
However, it is not at all clear that having a restart capability helps, it
seems that it could make things a lot worse. Another chance for the
engine to make like a bomb, after having already "dodged the bullet"
the first time.
Good idea or not, it is certainly novel, I have never heard it even
discussed, seriously, in the course of the Shuttle design, and many
subsequent studies. The only thing remotely similar is that on the
Centaur, there was an automatic sequence, even before the first of
the recent start failures, to try starting twice.
I am not sure if the effect is greater with rockets that with airplanes
or not, but certainly, the number of engines that one needs to
perform the intended mission decreases rapidly with time, and
restart wouldn't be very helpful, even if it could be accomplished.
Also, rocket engines tend to not be as easy to start, even the first
time, as airbreathers, and a restart capability could result in greater
complexity.
One question I alluded to, and didn't answer is "Are rocket engines
inherently less reliable, or inherently more destructive in failure
than airbreathers?" That is very controversial, but my own opinion is
not inherently, except for the oxidizer pump, and oxidizer pump
failures are a very small proportion of total engine failures and
confined to "primitive, early rocket engine designs."
In various earlier messages on this topic, the relative merits of
engines and wings, or the contribution of wings to safety were
discussed. This is a complex subject, but, to make a vast
oversimplification, wings have nothing to do with safety, engines do.
Wings may have something to do with operations cost, but, only at
high flight rates, and may have something to do with various other
capabilities/desirements.
Henry Spencer
>However, it is not at all clear that having a restart capability helps, it
>seems that it could make things a lot worse. Another chance for the
>...The only thing remotely similar is that on the
>Centaur, there was an automatic sequence, even before the first of
>the recent start failures, to try starting twice.
The Centaur people may have been influenced by having an engine that
appears to be exceptionally reluctant to fail catastrophically. I've
been told that since a couple of incidents in early development -- which
were traced to a test-stand interaction -- there have been zero cases
of catastrophic failure of an RL10. (Does your database back this up?)
--
"Every time I inspect the mechanism | Henry Spencer @ U of Toronto Zoology
closely, more pieces fall off." | he...@zoo.toronto.edu utzoo!henry
hvanderbilt on BIX
For what it's worth, the airliner that lost all three engines due to a
maintenance problem then barely limped back to land on one engine was
an L-1011, flying out of Florida (Miami?) and headed out over the Atlantic.
A mechanic had reinstalled oil sump drain plugs on all three engines
without bothering with O-ring seals. This case was a factor in what I
believe is a requirement that airlines doing two-engine overwater flights
have separate mechanics working on each engine, lest a single mechanic
pull the same bonehead mistake on both engines.
Matthew DeLuca
>Pre shuttle, all US manned spacecraft seemed to do a nice
>un powered water ditch, with only the notable loss of one capsule.
Argh, talk about misuse of the language.
U.S. capsules did not ditch, they were designed to splash down in the ocean.
Almost by definition, ditching is an unplanned act.
>wings don't seem that vital for spacecraft.
No, but they are certainly desirable. They make landing a lot easier and
a true winged spacecraft (NASP) has wonderful engine-out abort modes. Loss
of power on ascent for normal rockets is almost certainly a fatality, as is
loss of power on descent for something like DC-X.
--
Matthew DeLuca
Georgia Institute of Technology "Never fight a land war in Asia."
Office of Information Technology
mat...@prism.gatech.edu - MacArthur
Allen W. Sherzer
>U.S. capsules did not ditch,
Except for (Armstrong's?) Gemini flight.
>>wings don't seem that vital for spacecraft.
>No, but they are certainly desirable. They make landing a lot easier and
>a true winged spacecraft (NASP) has wonderful engine-out abort modes.
DC and most (all?) proposed SSTO's have engine out abort modes. DC can
land with only one of eight engines working. If all engines do fail (pretty
unlikely) then there is another mode: just fall. At engine start DC is less
then 20,000 feet high and going only a couple of hundred MPH. Landing base
first will cause the H tank to crumple absorbing most of the impact so
such a landing could be survivable. You could also stick on a parachute
if you wanted.
Now if you happen to come down in an area where there is several thousand
feet of clear and unobstructed space, you should be able to land. If not,
you may well survive the landing but you will be killed in the fire.
Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | Mortiki: "What do we do after we do it?" |
| a...@iti.org | Man with no name: "Ya live with it." |
+----------------------8 DAYS TO FIRST FLIGHT OF DCX------------------------+
Greg Moore
>a true winged spacecraft (NASP) has wonderful engine-out abort modes. Loss
>of power on ascent for normal rockets is almost certainly a fatality, as is
>loss of power on descent for something like DC-X.
You may want to tell the Russians that Soyuz doesn't have good
abort modes. Of course they might disagree. :-)
Gary Coffman
>un powered water ditch, with only the notable loss of one capsule.
>
>the soviets doa nice unpowered land ditch. wings don't seem
>that vital for spacecraft.
Just *big* parachutes. Of course all you're bringing back is that
little tiny thing at the nose of that great big rocket. The rest
gets strewn over the landscape on the way up. If you want a *reusable*
space*ship* rather than a throwaway capsule, the size of the parachute
gets out of hand. Then you need wings, or powered descent. If you're
content to throw away several tens of millions of dollars worth of
dumb booster on each flight, throwaway capsules are fine for spam
in a can transport. But if you need to carry other things, and have
room to work, and bring things back when you're done, then capsules
aren't so great because now you also have to have $100 billion dollar
space stations and another family of big dumb boosters for cargo and
construction that cost $200+ million per flight in order to do more
than play taxicab.
Henry Spencer
>
>No, but they are certainly desirable. They make landing a lot easier and
Assuming it's very close to a long hard-surface runway. Landing a NASP is
not going to be like landing a Cessna or a 767; almost certainly, like the
shuttle orbiter, it will be too fragile to ditch or belly-land safely.
(Its mass-ratio problems are *worse* than those of a rocket, because its
engines are much heavier and it has a lot of extra dead weight -- like
those wings -- to haul into orbit.)
>Loss
>of power on ascent for normal rockets is almost certainly a fatality...
If you mean *total* loss of power, perhaps... but the same is true of
winged vehicles. There are regions of the shuttle ascent trajectory
where a multiple engine failure is 100% fatal, utterly unsurvivable,
because the available reentry trajectories are too steep for the orbiter's
structure and thermal protection. And there's still that nasty problem
of finding a runway...
If you mean partial loss of power... sorry, wrong, rockets -- even manned
ones -- have lost engines on the way up and survived it. The old designs
typically couldn't lose one at liftoff and survive, as witness the last
Ariane failure, but this is an explicit design criterion for both DC and
recent expendable-launcher studies like NLS.
>as is
>loss of power on descent for something like DC-X.
Allen has already answered this one: normal losses of power, involving
only some engines, are eminently survivable for a VTOL SSTO (which has
far more thrust than it needs, coming down nearly empty), and there is
some possibility that even a total power loss will be a survivable crash.
Pat
prime stages.
Allen W. Sherzer
>>Loss
>>of power on ascent for normal rockets is almost certainly a fatality...
>If you mean *total* loss of power, perhaps...
BTW, if you don't include the escape rocket as total power loss, then Soyuz
has shown that catostrophic failure of an ELV is survivable.
Paul Dietz
>little tiny thing at the nose of that great big rocket. The rest
>gets strewn over the landscape on the way up. If you want a *reusable*
>space*ship* rather than a throwaway capsule, the size of the parachute
>gets out of hand. Then you need wings, or powered descent.
Truax would disagree. Tests during the SEALAR program showed that
simple booster stages can be recovered intact after dropping into
the water at 100 ft/s. You don't need an enormous parachute
to slow a booster stage to this speed.
Paul
Matthew DeLuca
>If all engines do fail (pretty
>unlikely) then there is another mode: just fall. At engine start DC is less
>then 20,000 feet high and going only a couple of hundred MPH. Landing base
>first will cause the H tank to crumple absorbing most of the impact so
>such a landing could be survivable.
Dropping from 20,000 feet at 200 mph is going to be almost certainly fatal.
Crushable structures are nice, but I really don't think there's any way on
earth that a vehicle with the weight margins of an SSTO is going to have a
fuel tank capable of absorbing that kind of an impact.
Not to mention, of course, the lovely explosion afterwards.
George William Herbert
Matthew DeLuca <mat...@phantom.gatech.edu> wrote:
>Dropping from 20,000 feet at 200 mph is going to be almost certainly fatal.
>Crushable structures are nice, but I really don't think there's any way on
>earth that a vehicle with the weight margins of an SSTO is going to have a
>fuel tank capable of absorbing that kind of an impact.
>
>Not to mention, of course, the lovely explosion afterwards.
Well, if impact speed is 200ish MPH then we can see that existing
Indy car and Formula 1 and Stock Car and GT race cars all meet
the "survive the impact" criterion for the crews.
The explosion is another issue. That can be avoided with a little
Halon (and I think the Ozone layer will begrudge you a bit of
damage in this case...).
Allen W. Sherzer
>Dropping from 20,000 feet at 200 mph is going to be almost certainly fatal.
Actually, your dropping about 150 miles, but distance doesn't matter,
terminal velocity does. As to survivability, Indy race car drivers survive
impacts at similar speed with much less protection. Humans can survive
very high levels of acceleration for very short periods of time.
>Crushable structures are nice, but I really don't think there's any way on
>earth that a vehicle with the weight margins of an SSTO is going to have a
>fuel tank capable of absorbing that kind of an impact.
Doesn't need to, just some of it. A well designed seat can take care of
the rest.
>Not to mention, of course, the lovely explosion afterwards.
Hydrogen is much less explosive then whatever fuel your airliner is burning.
Most fatalities from airliner crashes happen from their lovely explosion
afterwards (although nither explodes). So this is a common threat to
safety and applies at least as much to airliners.
Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | Mortiki: "What do we do after we do it?" |
| a...@iti.org | Man with no name: "Ya live with it." |
+----------------------7 DAYS TO FIRST FLIGHT OF DCX------------------------+
Pat
>
>Hydrogen is much less explosive then whatever fuel your airliner is burning.
>Most fatalities from airliner crashes happen from their lovely explosion
>afterwards (although nither explodes). So this is a common threat to
>safety and applies at least as much to airliners.
ACtually alan, very few airline passenger fatalities are caused by "explosion"
injuries. they are either blunt force impact injuries from the crash,
or smoke inhalation casualties as teh plastics in the cabin burn
releasing cyanide gas.
there have been numerous cases of the plane making an acceptable
touchdown while significant passenger casualties are taken
before they can un-ass the aircract.
The problem is severe enough that the FAA has a mojor plastics
reduction and flamability control program in the passenger
sections now.
pat
11086
>In article <24hlgs...@phantom.gatech.edu> mat...@phantom.gatech.edu (Matthew DeLuca) writes:
>
>>Dropping from 20,000 feet at 200 mph is going to be almost certainly fatal.
>
>Actually, your dropping about 150 miles, but distance doesn't matter,
>terminal velocity does. As to survivability, Indy race car drivers survive
>impacts at similar speed with much less protection. Humans can survive
>very high levels of acceleration for very short periods of time.
Since I've seen this twice now...remember that Indy cars very rarely hit
the wall head on at 200 mph. The safety modifications to the Indianapolis
track this year (removal of the inner lane that let them cut the corners
more tightly) were both to slow the cars down and to make them hit the
wall at an even greater angle (more glancing) in the event of a
crash/spin. I doubt anyone would survive a straight-on crash into a wall
at 200 mph (independent of the orientation of car at impact).
----------
My opinions are my own
Jim West
Associate Professor
Electrical and Computer Engineering
Oklahoma State University
jw...@jwest.ecen.okstate.edu
Allen W. Sherzer
>>Most fatalities from airliner crashes happen from their lovely explosion
>>afterwards (although nither explodes). So this is a common threat to
^^^^^^^^^^^^^^^^^^^^^^^^
>ACtually alan, very few airline passenger fatalities are caused by "explosion"
I know (see statement underlined above. I was quoting Mat's statement to show
that danger from burning fuel isn't unique to SSTO.
Allen W. Sherzer
>Since I've seen this twice now...remember that Indy cars very rarely hit
>the wall head on at 200 mph.
Nither would an SSTO.
Steinn Sigurdsson
In article <1993Aug14.1...@osuunx.ucc.okstate.edu> u10...@unx.ucc.okstate.edu (11086) writes:
>Since I've seen this twice now...remember that Indy cars very rarely hit
>the wall head on at 200 mph.
Nither would an SSTO.
??? Engine out, coming down, how do you avoid head-on?
Tilt the Earth? ;-)
I presume you do not intend all engine-outs to happen
in narrow, high valleys, so I presume you're saying the
SSTO will typically come in obliquely for the last 20k ft,
not straight?
BTW, isn't this all a bit silly. There is no requirment that
all conceivable emergencies within operating range be survivable.
If you're driving down (certain stretches of) the PCH and lose
both brakes and steering your survival chances are close enough
to zero as not to matter - and this is certainly within normal
operating range of cars. You deal with it and die.
| Steinn Sigurdsson |I saw two shooting stars last night |
| Lick Observatory |I wished on them but they were only satellites |
| ste...@lick.ucsc.edu |Is it wrong to wish on space hardware? |
| "standard disclaimer" |I wish, I wish, I wish you'd care - B.B. 1983 |
Gary Coffman
>>If all engines do fail (pretty
>>unlikely) then there is another mode: just fall. At engine start DC is less
>>then 20,000 feet high and going only a couple of hundred MPH. Landing base
>>first will cause the H tank to crumple absorbing most of the impact so
>>such a landing could be survivable.
>
>Dropping from 20,000 feet at 200 mph is going to be almost certainly fatal.
>Crushable structures are nice, but I really don't think there's any way on
>earth that a vehicle with the weight margins of an SSTO is going to have a
>fuel tank capable of absorbing that kind of an impact.
>
>Not to mention, of course, the lovely explosion afterwards.
The most likely failure, IMHO, would be a turbopump explosion with
high speed shrapnel severing feed lines to the other engines/pumps,
and likely perforating the hydrogen tank as well. Thus it would already
be burning/exploding on the way down.
Gary
--
Gary Coffman KE4ZV |"If 10% is good enough | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems | for Jesus, it's good | uunet!rsiatl!ke4zv!gary
534 Shannon Way | enough for Uncle Sam."| emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244 | -Ray Stevens |
Gary Coffman
>In article <24hlgs...@phantom.gatech.edu>,
>Matthew DeLuca <mat...@phantom.gatech.edu> wrote:
>>Dropping from 20,000 feet at 200 mph is going to be almost certainly fatal.
>>Crushable structures are nice, but I really don't think there's any way on
>>earth that a vehicle with the weight margins of an SSTO is going to have a
>>fuel tank capable of absorbing that kind of an impact.
>>
>>Not to mention, of course, the lovely explosion afterwards.
>
>Well, if impact speed is 200ish MPH then we can see that existing
>Indy car and Formula 1 and Stock Car and GT race cars all meet
>the "survive the impact" criterion for the crews.
George, have you ever inspected an Indy car or Stock Car carefully.
I have, I've raced stock cars. Almost all their mass, aside from
the engine and drivetrain, is devoted to maintaining integrity during
a crash, even the engine is used as a load bearing member. *And* almost
all crashes are either with other cars going about the same speed and
direction, or glancing strikes to crash barrier walls. Drive any
racecar into an unyielding head on barrier at 200 MPH and I can
almost guarantee 100% fatalities. A NASCAR racer carries 350 lbs
of fuel in a 4000 lb car. I don't think that describes an SSTO
very well.
>The explosion is another issue. That can be avoided with a little
>Halon (and I think the Ozone layer will begrudge you a bit of
>damage in this case...).
I wouldn't be so sure of that either. Halon systems on racecars
can handle fires from oil or fuel line ruptures, but don't have
a chance in hell of dealing with a ruptured fuel cell. That's
why the fuel cells are so big and heavy, so they *won't* rupture
in a crash. You can't do that with the SSTO's tankage.
Pat
armor provide reasonable lightweight control of shrapnel from
any particular engine?
I am pretty sure, modern Turbo-jets are now being provided with
kevlar windings to reduce collateral damage from turbine disk failure,
a rather similiar case. I don't think the weight penalty is that great,
cuz kevlar makes wonderful human type body armor.
George William Herbert
Gary Coffman <ga...@ke4zv.UUCP> wrote:
>George, have you ever inspected an Indy car or Stock Car carefully.
>I have, I've raced stock cars. Almost all their mass, aside from
>the engine and drivetrain, is devoted to maintaining integrity during
, even the engine is used as a load bearing member. *And* almost
>all crashes are either with other cars going about the same speed and
>direction, or glancing strikes to crash barrier walls. Drive any
>racecar into an unyielding head on barrier at 200 MPH and I can
>almost guarantee 100% fatalities. A NASCAR racer carries 350 lbs
>of fuel in a 4000 lb car. I don't think that describes an SSTO
>very well.
Gary,
SSTO is among the most survivable in a crash vehicles I can think of.
Why? Presuming it's going backwards, with the people at the top,
like it's supposed to be (all bets off otherwise), you will have 20
meters of crush zone to absorb energy before the pilot reaches ground
level. 200 mph is what, 100ish meters per second? That's about 0.4
second of decelleration, or an average of 250 m/s^2 decelleration
or 25 Gs. People survive 100 G impacts quite easily, in properly
designed seats they're well strapped into. We're talking about
1/4 of that average force. 100 MPH into a wall with 1 meter
of crush space (Average race car) is about 100 G's, and I've met
many people who survived 100 MPH headon impacts with walls. Dad
used to race cars, though he never really crashed one (he went off
the track once, though...). 200 MPH into a wall in the same
crush space is 400 G's, but we're not talking about one meter
of crush space. We have a whole rocket stage under you to absorb
the energy.
>I wouldn't be so sure of that either. Halon systems on racecars
>can handle fires from oil or fuel line ruptures, but don't have
>a chance in hell of dealing with a ruptured fuel cell. That's
>why the fuel cells are so big and heavy, so they *won't* rupture
>in a crash. You can't do that with the SSTO's tankage.
You don't have to; identify the parts of the vehicle likely to
start fires (engine compartment, maybe APU spaces) and halon
them. Dump the LOX if you can before you impact; without that,
LH2 is pretty safe in a fire, as it evaporates and goes UP
and doesn't burn that hot even if a fire does start.
Henry Spencer
>The most likely failure, IMHO, would be a turbopump explosion with
>high speed shrapnel severing feed lines to the other engines/pumps,
Such failures are extremely rare, barring cases like those Henry Hillbrath
has mentioned, where overly-stupid designs make no attempt to shut down in
the face of conditions that clearly make continued operation unsafe.
No RL10 has ever failed in such a way.
Indeed, no operational Western liquid-hydrogen engine has ever had such a
failure. (I won't be surprised if it happens to an SSME eventually,
but we're clearly talking about a very rare failure mode.)
This is far from "the most likely failure". It's not quite in the same
category as being hit by a meteorite during ascent, but it's close.
Josh Hopkins
>Gary,
>SSTO is among the most survivable in a crash vehicles I can think of.
>Why? Presuming it's going backwards, with the people at the top,
>like it's supposed to be (all bets off otherwise) ...
[Stuff deleted]
While putting the people on top does make sense, its not clear that that's
the way things will actually turn out. CERV and SASSTO did it that way but
more recent designs like Pheonix and Delta Clipper have put the passengers in
the middle. It's not obvious to me that we can expect a conventional VTOL SSTO
which has managed to loose all of its engines will be coming down base first.
I'm especially skeptical if we're talking about the Delta Clipper, which
certainly doesn't re-enter base first.
On the other hand, what's the big deal? The ones we build in the next twenty
years won't be the 747s of space. They'll be early models, the things we learn
from. They'll carry more cargo than passengers. Is it a big deal if they
can't survive every imaginable failure?
--
Josh Hopkins jbh5...@uxa.cso.uiuc.edu
"Americans always do the right thing, once they have
exhausted all other possibilities"
- W. Churchill
George William Herbert
Josh Hopkins <jbh5...@uxa.cso.uiuc.edu> wrote:
>g...@soda.berkeley.edu (George William Herbert) writes:
>>SSTO is among the most survivable in a crash vehicles I can think of.
>>Why? Presuming it's going backwards, with the people at the top,
>>like it's supposed to be (all bets off otherwise) ...
>
>[Stuff deleted]
>
>While putting the people on top does make sense, its not clear that that's
>the way things will actually turn out. CERV and SASSTO did it that way but
>more recent designs like Pheonix and Delta Clipper have put the passengers in
>the middle. It's not obvious to me that we can expect a conventional VTOL SSTO
>which has managed to loose all of its engines will be coming down base first.
>I'm especially skeptical if we're talking about the Delta Clipper, which
>certainly doesn't re-enter base first.
Yes, and they're also 35-45 meters tall, with the people about 20 meters up.
Which is why I used the 20 meter crunch space figure. Also why I suggested
dumping the LOX supply; it's (at least was in one configuration) up at
the nose, and having LOX spill down into the cabin post-crash is ...
not my idea of enhanced survivability characteristics.
You're right about directionality. All I can reply with is, "Parachutes".
If you know you're going down the wrong way, jump out at 20,000 feet.
200 knots is plenty slow enough for a jump.
>On the other hand, what's the big deal? The ones we build in the next twenty
>years won't be the 747s of space. They'll be early models, the things we learn
>from. They'll carry more cargo than passengers. Is it a big deal if they
>can't survive every imaginable failure?
Nothing can survive every imaginable failure. However, there are dozens of
cheap and easy things that can be done in early concept definition
and detail engineering which eliminate many failure modes and enhance
survivability of other failure modes. Designing the tanks under the
cabin to crunch and absorb energy so crew survive an impact is one
of those; it should be possible without adversely impacting the rest
of the design. If all the engines fail at once on decent, after
flipover (for whatever reason), then that's gonna be a life-saver,
and all it takes is a little more structural modeling.
That won't save you from a multiple engine failure shortly after takeoff,
or a large meteorite impact in orbit, or a software bug that causes control
loss or motors which blow up and take out their neighbors and the
tank above them. It will save you from certain failures during decent
where you land hard but in the right direction, which could be caused by
any number of system failures or fuel exhaustion or... and since all it
will really "cost" is a few engineer-years, why not?
Allen W. Sherzer
>content to throw away several tens of millions of dollars worth of
>dumb booster on each flight, throwaway capsules are fine for spam
>in a can transport. But if you need to carry other things, and have
>room to work, and bring things back when you're done, then capsules
>aren't so great because now you also have to have $100 billion dollar
>space stations and
Any yet the Russians can provide better services faster and for
a fraction of the cost in spite of the fact that they use the technology
you claim won't work.
>another family of big dumb boosters for cargo and
>construction that cost $200+ million per flight in order to do more
>than play taxicab.
Compared to our 'reusable' vehicle which costs about three times as much.
allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | Mortiki: "What do we do after we do it?" |
| a...@iti.org | Man with no name: "Ya live with it." |
+----------------------5 DAYS TO FIRST FLIGHT OF DCX------------------------+
John F. Woods
>The most likely failure, IMHO, would be a turbopump explosion with
>high speed shrapnel severing feed lines to the other engines/pumps,
>and likely perforating the hydrogen tank as well. Thus it would already
>be burning/exploding on the way down.
Which, of course, airplanes have been wont to do from time to time as well.
A winged glider, of course, doesn't have this problem, but as has been observed
before, a big HEAVY glider is extremely sensitive to mispredictions of weather
conditions -- remember the Shuttle that came down in the underrun area just
before the landing strip because weather forecasters missed on the air density
by just a tiny amount. Just a tiny bit larger of a misforecast, and the
Shuttle would have landed on random terrain (which voids the warranty).
Matthew DeLuca
>Any yet the Russians can provide better services faster and for
>a fraction of the cost in spite of the fact that they use the technology
>you claim won't work.
You mean those guys who charged the French $17,000/kg on the way up, and
$51,000/kg on the way down, with a 200kg limit?
George William Herbert
Matthew DeLuca <mat...@phantom.gatech.edu> wrote:
>You mean those guys who charged the French $17,000/kg on the way up, and
>$51,000/kg on the way down, with a 200kg limit?
That's not fair, Matthew. The Russians only did this because they
need money bad, and the French had effectively deep pockets, and
the Russians were able to put the screws on a bit to up their profits
for the whole endeavour. If you buy and launch a Kvant module,
and buy loaded Progress flights, the $/kg will be much more reasonable.
The French got caught out on contractual holes.
Doug Mohney
>You don't have to; identify the parts of the vehicle likely to
>start fires (engine compartment, maybe APU spaces) and halon
>them.
You start sucking away at mass margins and pretty soon you'll not have much
cargo to take up... It'd be interesting to look at crash survivability tho'.
>Dump the LOX if you can before you impact;
Ok, if you can't do that, you're screwed. That's simple enough.
>LH2 is pretty safe in a fire, as it evaporates and goes UP
>and doesn't burn that hot even if a fire does start.
Yah, but the problem is that upon impact, crew cabin on top of DC is still
going to get a bit toasty. If the cabin structure is maintained AND the
bulkhead (?) between the cabin and the PAYLOAD compartment is relatively fire
resistant, you might be able to ride the fire out. IF the payload compartment
is empty, then you get bonus points.
If there's returning cargo stuck in the payload compartment, all bets are off
depending on what it is and the physics/engineering between the deformation of
the bottom of the payload compartment and the fuel tanks and engines....
which come to think of it, will probably get shoved up into the tankage and
possibly penetrating the payload compartment...
Gary, can you do a rough computer simulation on this? It'd be an interesting
hack just to see how some of the mechanical deformations come out. I bet
MacDac could really provide better insight...
January 1993 - John Scully embraces Bill Clinton.
July 1993 - Apple Computer lays off 2500 workers, posts $188
million dollar loss.
-- > SYS...@CADLAB.ENG.UMD.EDU < --
Matthew DeLuca
>In article <24oso5...@phantom.gatech.edu>,
>Matthew DeLuca <mat...@phantom.gatech.edu> wrote:
>>You mean those guys who charged the French $17,000/kg on the way up, and
>>$51,000/kg on the way down, with a 200kg limit?
>That's not fair, Matthew. The Russians only did this because they
>need money bad, and the French had effectively deep pockets, and
>the Russians were able to put the screws on a bit to up their profits
>for the whole endeavour.
It's not as unfair as you think; Allen's claim was better price *and*
service, if I recall correctly. They came out inferior on both.
>If you buy and launch a Kvant module,
>and buy loaded Progress flights, the $/kg will be much more reasonable.
>The French got caught out on contractual holes.
Sure...but who wants a Kvant module? Service implies giving the customer
what he wants, at a price he can afford. I bet the French could have
leased a GAS can or gotten locker space on board Spacehab for far less.
The one thing the Russians do have is on-time performance; they generally
launch when they say they will. If your payload is time-critical, go with
them, but that's about the only reason I can come up with.
George William Herbert
Matthew DeLuca <mat...@phantom.gatech.edu> wrote:
>It's not as unfair as you think; Allen's claim was better price *and*
>service, if I recall correctly. They came out inferior on both.
>Sure...but who wants a Kvant module? Service implies giving the customer
>what he wants, at a price he can afford. I bet the French could have
>leased a GAS can or gotten locker space on board Spacehab for far less.
>
>The one thing the Russians do have is on-time performance; they generally
>launch when they say they will. If your payload is time-critical, go with
>them, but that's about the only reason I can come up with.
...or put their hardware in a Progress, and bought a Progress mission
to fly while their astronaut was there, etc. I get the impression that
the majority of the "item overcharges" were due to last minute things
that weren't well negotiated beforehand. Like I said, if you send
the Russians an exact list of what you want to fly and how and
it's complete from stage one, then you should get good returns.
The people I know who've flown things on Mir had these results.
Sounds like someone somewhere screwed up on the French mission
and bucks were thrown at the problem to correct it.
[note: I don't know much more than anyone else does about the
details of the French contract, trade mags for the most part...
I'm guessing based on the way it was reported]
George William Herbert
Doug Mohney <sys...@king.eng.umd.edu> wrote:
>Gary, can you do a rough computer simulation on this? It'd be an interesting
>hack just to see how some of the mechanical deformations come out. I bet
>MacDac could really provide better insight...
Energy-absorbtion characteristics of composite structures vary so widely
based on construction and materials details that not knowing the exact
materials and layup makes modeling pretty hard. With a metal structure,
it's a snap, but composites aren't nearly so easy. I think asking
MacDac is the right solution, if they're not too busy.
I won't stop Gary from trying to model it, though. He may well know
more about doing deformation modeling than I do (wouldn't be too
hard, I've never actually done any crash modeling). 8-)
Allen W. Sherzer
>It's not as unfair as you think; Allen's claim was better price *and*
>service, if I recall correctly. They came out inferior on both.
I think you recall incorrectly but you tell me. For their $52 million
this is what the French could have:
Option A: Backward Russian Tech Option B: Latest US Technology
1. 220 pound payload for 30 days 1. About 3.5 days on Shuttle
2. 440 pound payload for 135 days
3. 22 pounds for each astronaut
4. 330 hours of Cosmonaut time
5. Two or more ESA astronauts for 165 days
So if it was your money, which would you pick?
Now it is true that extra services are much more, but that is to be
expected. The French are asking for space on demand which means that Russian
payloads and experiments don't fly. The French must therefore not only pay
for the cost of their payloads but also for the Russian experiments which
don't fly.
Allen
Allen W. Sherzer
>to fly while their astronaut was there, etc. I get the impression that
>the majority of the "item overcharges" were due to last minute things
>that weren't well negotiated beforehand.
From my readings of the stories, there is no 'overcharges'. If the French
planned their payloads carefully they won't need anything beyond what
they got for their $52M. The large extra costs are simply because if the
French use more facilities then Russian experiments don't fly. There's
nothing wrong with making the French pick up those extra costs.
Pat
Doug,
try to understand that Cryogenic fuels don't burn in
any way like the hydrocarbon fuels you see in day to day life.
cryo fuels burn like volatile vapors. a large puff along the
mix boundary, rapidly expanding and gone. the real trick according
to Henry Hilbraith is keeping the LOX from binding wiht terrestrial
hydro-carbons, then it becomes very problematic.
Kerosene, napalm, gasoline tend to adhere and burn, LH tends to move
off.
pat
Allen W. Sherzer
>Option A: Backward Russian Tech Option B: Latest US Technology
>1. 220 pound payload for 30 days 1. About 3.5 days on Shuttle
^^^^^^^^^^^^^^^^^^^^^^^^^^
BTW, that's 3.5 person days, not 3.5 days of Shuttle time. It's less than
10% of a flight.
Matthew DeLuca
>>It's not as unfair as you think; Allen's claim was better price *and*
>>service, if I recall correctly. They came out inferior on both.
>I think you recall incorrectly but you tell me. For their $52 million
>this is what the French could have:
>Option A: Backward Russian Tech Option B: Latest US Technology
>1. 220 pound payload for 30 days 1. About 3.5 days on Shuttle
>2. 440 pound payload for 135 days
>3. 22 pounds for each astronaut
>4. 330 hours of Cosmonaut time
>5. Two or more ESA astronauts for 165 days
Could have? I am referring to what they *did* have. Unless I am grossly
mistaken, none of the above has happened. What exactly are you referring to?
And as for 'extra services' costing more; I don't regard getting your
payload down as an 'extra service'. Then again, little details like that
*are* included in the U.S. price.
Oh, what is that 3.5 days above, anyway? There hasn't been a mission that
short in the last ten years.
Matthew DeLuca
>In article <1993Aug17.0...@iti.org> a...@iti.org (Allen W. Sherzer) writes:
>
>>Option A: Backward Russian Tech Option B: Latest US Technology
>>1. 220 pound payload for 30 days 1. About 3.5 days on Shuttle
>BTW, that's 3.5 person days, not 3.5 days of Shuttle time. It's less than
>10% of a flight.
Oh, let me guess: you divided $52 million by $500 million to get your
above '10%' figure?
No wonder so few people give your numbers any credit; that's pathetic.
Gary Coffman
>In article <1993Aug15....@ke4zv.uucp> ga...@ke4zv.UUCP (Gary Coffman) writes:
>>The most likely failure, IMHO, would be a turbopump explosion with
>>high speed shrapnel severing feed lines to the other engines/pumps,
>>and likely perforating the hydrogen tank as well...
>
>Such failures are extremely rare, barring cases like those Henry Hillbrath
>has mentioned, where overly-stupid designs make no attempt to shut down in
>the face of conditions that clearly make continued operation unsafe.
>
>No RL10 has ever failed in such a way.
No RL10 has failed this way, but no RL10 has been called upon to
launch 50 times a year with minimal ramp maintenance either. Jet
aircraft turbine explosions are relatively rare too, but given
the number of flight hours, they do happen fairly regularly. A
turbopump is under much more stress.
h.hil...@genie.geis.com
> Matthew DeLuca <mat...@oit.gatech.edu>
Writes:
> Loss of power on ascent for normal rockets is almost certainly a
fatality, as is loss of power on descent for something like DC-X.
I will let the DC people argue their own case, I do not fancy the idea
of "backing into" a busted engine, myself. And, I don't know just
what these "normal rockets" are, but my experience with a lot of
abnormal ones has convinced me that in most cases, if one has an
engine out capability, one is in very good shape if one just isolates
the failed engine and "puts the pedal to the metal" "aborting to
orbit." It was a folk myth in my youth in the swamps of Georgia that
one could determine the evolutionary affiliations of creepy crawly
things, like snakes and turtles say, by threatening them and seeing
which way they crawled, toward or away from the water. Airplanes
and space vehicles almost always are better off flying than landing.
There is nothing scarier than sitting on a load of propellant with a
busted engine which is spilling out its guts and there is nothing you
can do but wait for it to go off under you.
From the historical records, most propulsion system failures are not
"bomb like," and most catastrophes have happened because there
was not enough thrust and the vehicle ran into the ground. (I have
had some experience with real bombs. Rocket engines are lousy
bombs. Solids are better, but still lousy.) One vehicles catastrophe is
another vehicles minor hiccup. If there is no engine out capability,
every failure is a catastrophe.
When I began work on the Atlas program (several lifetimes ago)
every young engineer was told, as a point of pride, the basic program
philosophy: "Everything on an Atlas rocket HAS to work, if you find
something that does not HAVE to work, take it off." Every failure was
a catastrophe, and frequently what would have otherwise have been
a minor anomaly in the post flight evaluation took out the whole
darn vehicle and sometimes the ground facility, too. That was the
WRONG philosophy, even for an ICBM certainly for a launch vehicle,
and the Atlas still suffers from it, despite years of trying to get that
concept back out of the system.
Of the failures where engines actually did "bomb like things" the
most common problems were things to do with gears and oil, which
"modern" engines do not have. Very few turbopumps have failed in
flight due to causes other than lube oil related ones. No propellant
lubricated bearing has ever caused a flight failure (the SSME, J-2, H-
1, F-1 etc. have all propellant lubricated bearings.)
The next most common "bomb like things" were leaks, which are
mitigated by the space environment (and are the reason I don't like
"backing down" on a sick engine. Static or captive tests, or refused
liftoffs, are MUCH more dangerous than flights, from a propulsion
standpoint.)
Then you are down to the "onesees - twosees" like combustion
instability, which has questionable as a potential "bomb like thing"
and which again, "modern" engines don't have (not even ancient ones
that have been "modernized") and LOX pump "explosions," likewise.
BTW, two U. S. manned launches had a "loss of thrust" in liquid
propulsion systems, which not only did not result in fatalities, but in
one case, was so little noticed and commented on that I doubt if
anyone but "Henrys" know about it. (I sure hope one of the other
ones does, or I will have to look it up! It didn't even make my
database, yet. The other manned failure was on a Shuttle flight, 51-F
12 July 1985, due to a bad temperature sensor.) There was also one
on an unmanned Saturn I, with no adverse results. SA-6, 28 May
1964. and on two stages of an unmanned Saturn V, SA-502, 4 April
1968 (a total of three engine shutdowns.)
h.hil...@genie.geis.com
> hvanderbilt on BIX <hvand...@BIX.com>
> For what it's worth, the airliner that lost all three engines due to a
maintenance problem then barely limped back to land on one engine
was an L-1011,
Thanks, I was pretty sure it wasn't a DC-10.
> A mechanic had reinstalled oil sump drain plugs on all three
engines without bothering with O-ring seals.
That really sounds stupid, and I thought so at the time, but I read
the accident report, and the interview with the mechanic that did the
installation. It wasn't nearly so simple as it sounds, as in some cases
it was the practice of that airline to include seals as a part of the unit
being installed (this would have been easy to do on the plug, as the
"o" ring fit in a groove, where it would have been easy to install it.)
He was, I think, given the plugs and told to install them, and
therefore didn't have to confront the issue of whether he had all the
parts he was to install, or not. The mechanic was still responsible, of
course, but I think one can see that his action wasn't totally
inexplicable, and that the problem was, at least partly, a design one,
and a system one. (Designers should, in my opinion, ALWAYS think
that there was a way a better design could have avoided the
problem, and I usually do. Not all designers do that, though.)
We had a similar problem on one of my programs, with a valve we
used for flow control. It had an orifice installed inside the valve, but
one had to read the drawings very carefully to see that when one
replaced the valve one had to get the orifice out of the old valve and
install it in the new one, and sure enough, that came very close to
biting us, eventually. Better practice is to have the orifice out where
it can be seen, and the seal could have either really been a part of
the plug, or the plug could have been designed to make the fact that
the seal was missing more obvious.
Hard to imagine that the plug would leak that darn fast, anyway,
even with no seals.
Paul Dietz
> launch 50 times a year with minimal ramp maintenance either. Jet
> aircraft turbine explosions are relatively rare too, but given
> the number of flight hours, they do happen fairly regularly. A
> turbopump is under much more stress.
In one respect the jet engine turbine is in a much more severe
environment. Recall that the RL-10 is an expander cycle engine, in
which hydrogen gas warmed by passage through regenerative cooling
channels drives the turbine. The turbine temperature is only ~100 C.
Paul F. Dietz
di...@cs.rochester.edu
Gary Coffman
>Any yet the Russians can provide better services faster and for
>a fraction of the cost in spite of the fact that they use the technology
>you claim won't work.
Didn't claim it won't work, claimed it was inefficient. There's little
evidence that the Russians provide *better* services, and of course
they're doing it with $40 a month workers, something we don't have.
Besides, I thought you were backing DC because it *doesn't* throw
away 90% of it's structure on each flight.
>>another family of big dumb boosters for cargo and
>>construction that cost $200+ million per flight in order to do more
>>than play taxicab.
>
>Compared to our 'reusable' vehicle which costs about three times as much.
Yeah, but it doesn't also require another different launcher to carry
the experimenters up, and it doesn't require a space station for them
to do the experiments in. When you price all that out, *using US labor
costs*, the Russian way suddenly doesn't look so cheap. Comparing $40
a month to $40 an hour makes a big difference.
h.hil...@genie.geis.com
> Henry Spencer <he...@zoo.toronto.edu>
writes:
> The Centaur people may have been influenced by having an
> engine that appears to be exceptionally reluctant to fail
> catastrophically.
You phase that carefully, "influenced," and correctly so. Even if one
participates in the decision, one can never really say, for certain, why
something is "designed the way it is." (Or as we use to say in the old
days, some things you can draw, and release, and the parts get built,
and it lasts for ever, any you can imagine that no one else ever knew,
or cared. Other things, you couldn't even have on your drafting table,
or now, your CAD terminal, with out every one in the darn plant
telling you that it wouldn't work. You might imagine that you knew
exactly why a part was the way it was, but you couldn't know why it
survived the review process.)
But, I think that we can be very sure that catastrophic failure
potential had nothing to do with it, whatever.
If you car (if you have a car) had a chance of 999 out of a 1000 of
starting when you turned the switch, but had a five percent chance
of exploding if it didn't start, and you turned the switch twice, you
would probably think awfully hard about trying the second time. You
might even be a bit nervous the first time!
But, if you are a Centaur, and either engine doesn't start the first
time, your chances of winding up in "The Dreaded Earth Intersecting
Orbit" are unity unless you do something. If there is one chance in a
million of success on the second try, then it makes sense to try it.
Even if all the other chances are "catastrophic." Not doing anything is
guaranteed catastrophic.
There remains the question, is the engine "exceptionally reluctant to
fail catastrophically." And, I suspect, no reflection on you, that your
question reflects some of the hype that has been circulated relative
to the engine design. The manufacturer of the RL-10 (I remember
their name, but won't mention it, I have some good friends there, as
at all the engine companies) is understandably quite proud of the
performance of their engine, and until the recent failure of two of
them in Centaur flights described it as something approaching a
magic engine that could never fail, catastrophically or not.
A few years ago, in response to the assertion that "all engines are
not created equally" by one of their reliability expert, I did the
standard naive statistical stuff, and concluded they were right. There
is an engine that is distinctly worse than the rest (I won't mention
which it is either) but the RL-10, at that time, was not significantly
different than the SSME, F-1, H-1 and numerous other engines,
there just was not enough data. It may now be worse.
That is on reliability. To answer the question about reluctance to fail
catastrophically, one has to analyze the failures. The number of trials
has not even been enough to demonstrate that the reliability is
higher or lower, it is obviously absurd to try to prove anything about
failures that haven't happened not being catastrophic.
> I've been told that since a couple of incidents in early development
-- which were traced to a test-stand interaction
Early RL-10 testing was done horizontally and with an "ejector" to
allow the engine to run at sea level conditions. The ejector was pre-
evacuated with a vacuum system, but was self pumped during the
run.
For some reason, probably one of those "warm fuzzy feeling" for high
level managers type things, it was decided that before the RL-10 was
flown in the Centaur, it should be tested in a "dual vertical" stand.
What either "dual" or "vertical" really had to do with the flight
condition, I don't know, but it seemed more reasonable at the time (I
was working for Convair while this was going on, in a group that did
all propulsion, Centaur and otherwise, although I mainly worked
Atlas.)
Well, the first time they tried the dual vertical test, the test stand
tried to go into orbit, sans engines. The engine supplier asserted
that this was a random occurrence, rebuilt the stand, and tried again,
same result. After that, they opened up quite a lot, and let Convair
look at the test data for the first time. We were not impressed, they
were stuck in the airplane engine data world, and the test stand
disappeared between data samples.
Eventually, it was found that there was a long and poorly repeatable
ignition delay, in fact, the engine would have never ignited at all,
except for a leak in the injector that had not been previously
identified .
The long delay allowed the dual ejector configuration to accumulate
a considerable amount of unburned propellant which caused one of
the engines to light off rather suddenly, and from the wrong end.
This was purely a test stand configuration problem and would never
have happened in flight. On the other hand, as a result of the failure,
we got a great deal more insight in the engine suppliers knowledge,
or lack of it, of how the engine really worked. Since then, I have
gotten a lot more. Until recently, the RL-10 was a very lucky engine,
but it has never been a magic one, and isn't now.
> -- there have been zero cases of catastrophic failure of an RL10.
(Does your database back this up?)
Well, first, I should have said that my database only has valid data
for flight failures. Engine tests and static vehicle tests results are
very hard to get, and hard to "scope." (were they truly "accountable?"
were they truly "equivalent flight failures?") There have only been
the two recent RL 10 flight failures, both of which were "wimp out"
failures to start. (I guess if they put the Centaur and General
Dynamics, out of business, they will be judged to have been
"catastrophic" enough.)
I have also been told that there were never any "catastrophic"
failures of the RL-10 in engine tests, also, but that is very hard to
even define. For example, the two I described, which were definitely
catastrophic, were not included, "not engine failures" I suppose. I
would like to know how many others were not reported, for what
ever reason. But, on the other hand, there is some vehicle
(conceptually) that will survive any engine failure, so the whole idea
of "catastrophic" failure for a undefined vehicle is invalid.
Where the RL-10 people really went off the deep end was in
extrapolating from the RL-10 to the idea that all expander cycle
engines would have similar "graceful degradation" characteristics. I
worked very closely with them, the only vehicle contractor that did,
on the STME program, to try to make sure that the expander cycle
got a fair evaluation. I have always been a proponent of the "graceful
degradation" idea, and at first, I thought that might be a
discriminator.
Engines typically have several hundred potential failure modes and
in most of them the expander cycle had exactly the SAME mode, and
potential for "catastrophic" failure as the baseline GG cycle did. For
other modes, the expander was better in some modes and the GG
better in others.
Most of the modes result in "non catastrophes." Much of the historical
record is misleading on this, for various reasons, including the fact
that failure result was not considered in the original design of most
of the engines and vehicles that make up the data base. Hopefully, no
one does that any more.
One loses creditability when one tries to argue that no liquid rocket
propulsion system failure could be catastrophic, as it is obvious that
some have been. But, I will, and have, argued, that there are no
inherently un-survivable liquid rocket propulsion system failures
that SHOULD be considered to be applicable to future design. And, of
the very few modes engine failure modes that could cause "bomb
like behavior" most are shared by all engine cycles.
All have LOX pumps, all LOX pumps can explode (very low
probability). All have rotating shafts with disks on them, all can over
speed and shatter disks (also low probability). Some argue that an
expander is MORE likely to do that than other cycles.
The only modes in which the expander could claim that it is had
much advantage in "graceful degradation" were the chamber burn
through modes. Those are the modes for which it inherently had
lower margins than the GG cycle did. In other words, it was going to
have a lot more graceful failures because it was going to have lot of
failures in modes there the GG was never going to fail.
Specifically, the there is no reason to design the GG cycle engine with
low margins on chamber burn-through, is doesn't buy you anything.
The expander has to get all its drive energy through the chamber
wall and the lower the burn-though margin the higher the
performance.
Other margins, like those on bearings, rotors, etc. would be selected
to be exactly the same for both designs.
Every engine is a special case. The RL-10 is the only expander that
has ever made it to production. But it has a lot of other unique
circumstances too. It has unusually high margins for a rocket engine,
for various historical reasons. The manufacturer has claimed that its
thrust level can be doubled with no difficulty. If other engines were
always run at half power, they would have reduced catastrophic
failures too. There are also failure modes that affect booster engines
that do not exist for engines, like the RL-10, that only operate in
space, Every RL-10 that ever flew could have had propellant leaks
that would have caused vehicle failure in the atmosphere, for
example, and no one would have ever noticed.
Not everyone remembers that in the early days of the Space Shuttle,
it was those same RL-10 people that were arguing that staged
combustion, the SSME cycle, was the only way to go for booster
engines (they had the only staged combustion cycle engine program
going at the time). But, they didn't get the contract. They now argue
that expanders are inherently better than staged combustion. They
may have been wrong both times, but they were not right, both
times.
My feeling, and this is based on a lot of thought, is that the SSME is
the very minimum performance that should be considered for any
future vehicle, and that a new engine must have better performance
and better operability, both, or it is a "non starter." And, for those
that think that we should go back to a more robust, but lower
performance engine, please tell me where there is a parallel for that
in airplanes, automobiles, etc. in which engine performance is not
nearly so critical from an economic standpoint as it is in space
vehicles.
Boosters, and especially SSTO's are at least as performance critical as
air superiority fighters. People that say give back a few seconds of
Isp so that the engine is more robust are the same ones that were
telling Spitfire and Mustang pilots that if they didn't use such high
boosts when running from FW 190's they would get longer engine
life. It isn't cost effective to derate transport engines, much less
fighter engines. And gravity is every bit as tough an opponent as an
enemy fighter.
h.hil...@genie.geis.com
a common mode failure of airplane engines. Someone asked me in
e-mail what the heck that meant.
Literally, it is "Net Positive Suction Pressure," but the explanation of
what that is, and why it is a critical parameter for pumps is a long
one and one that we propulsion types would just as soon keep in the
fraternity.
Suffice it to say that it is an inside joke, that someone had an NPSP
problem, thought it as icing, and turned on the heaters. If you don't
get it, it isn't funny, no matter how much it is explained, on the
contrary, it just gets more tedious.
Hugh Emberson
Jim> Since I've seen this twice now...remember that Indy cars very rarely hit
Jim> the wall head on at 200 mph. The safety modifications to the Indianapolis
[...]
Remember that not all Indy car races are on oval tracks.
In the Italian grand prix (Formula 1) a couple or four years ago,
Gerhard Berger (sp?) drove his Ferrari into a wall at ~200 mph. He
survived and is still racing. Actually he didn't drive it into a
wall, the steering rod broke.
Hugh
--
Hugh Emberson
hu...@cosc.canterbury.ac.nz
Allen W. Sherzer
>>Option A: Backward Russian Tech Option B: Latest US Technology
>>1. 220 pound payload for 30 days 1. About 3.5 days on Shuttle
>>2. 440 pound payload for 135 days
>>3. 22 pounds for each astronaut
>>4. 330 hours of Cosmonaut time
>>5. Two or more ESA astronauts for 165 days
>Could have? I am referring to what they *did* have. Unless I am grossly
>mistaken, none of the above has happened. What exactly are you referring to?
Don't quibble and answer the question: if it where YOUR money, which
option would you sign up for?
>And as for 'extra services' costing more; I don't regard getting your
>payload down as an 'extra service'.
Nither do the Russians. Return space for the base experiments is included.
If the French budget their weight carefully, they need pay no more.
allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | Mortiki: "What do we do after we do it?" |
| a...@iti.org | Man with no name: "Ya live with it." |
+----------------------4 DAYS TO FIRST FLIGHT OF DCX------------------------+
Allen W. Sherzer
>>>1. 220 pound payload for 30 days 1. About 3.5 days on Shuttle
>>BTW, that's 3.5 person days, not 3.5 days of Shuttle time. It's less than
>>10% of a flight.
>Oh, let me guess: you divided $52 million by $500 million to get your
>above '10%' figure?
Yep, and a rough estimate of person days in space. All in all, for $52M
you can buy 160 or so days on Mir or less than 10% of a Shuttle flight.
If you don't like the methods I used, then substitute your own and
justify it. But don't call it patethic until you do.
Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | Mortiki: "What do we do after we do it?" |
| a...@iti.org | Man with no name: "Ya live with it." |
+----------------------4 DAYS TO FIRST FLIGHT OF DCX------------------------+
yancy l shirley
Alot of Indy car crashes occurs at 200 mph +. Indy cars spend the entire
month of MAY at Indianapolis... practicing, qualifying.. etc. Even with
new USAC (Untited States Auto Club) restrictions that were designed to slow
the cars down... Mario Andretti was able to average 227+ !! EVERY YEAR
someone has a head on collision... usually resulting in foot and ankle injuries
(just last year: Jeff Andretti, Nelson Piquet, and Mario Andretti). This year
the chassis was increased in length and strength... the result was no feet
injuries at INDY!
I haven't been following the entirety of this debate... but i wanted this matter
cleared up. Just ask Jim Crawford, Nelson Piquet, A.J. Foyt, or Jeff Andretti
if Indy cars rarely hit the wall head on over 200 mph... (better yet, just watch
any of them try to walk through the pit area). Two drivers have lost their lives
at INDY in the last ten years.. even with saftey modifications... its still a VERY
DANGEROUS SPORT. Even though its a morbid topic and something I rather not see,
it is part of the sport. When drivers enter a left hand corner , baked at 13 deg,
at 236+ mph (A.J. Foyt this year), then the impact is going to be VERY hard.
Yancy Shirley
yshi...@gas.uug.arizona.edu
Matthew DeLuca
>>Oh, let me guess: you divided $52 million by $500 million to get your
>>above '10%' figure?
>Yep, and a rough estimate of person days in space. All in all, for $52M
>you can buy 160 or so days on Mir or less than 10% of a Shuttle flight.
>If you don't like the methods I used, then substitute your own and
>justify it. But don't call it patethic until you do.
Okay. Allen, if the French fly a payload on the Shuttle for $52 million,
and the flight is 10 days in duration, do you think they turn it off after
a single day? Your dollar division is hopelessly simplistic, which is why
I called it pathetic.
Matthew DeLuca
>>Could have? I am referring to what they *did* have. Unless I am grossly
>>mistaken, none of the above has happened. What exactly are you referring to?
>Don't quibble and answer the question: if it where YOUR money, which
>option would you sign up for?
Don't quibble? You quote meaningless numbers and things that haven't happened
and may never happen, and wonder why I question you?
>>And as for 'extra services' costing more; I don't regard getting your
>>payload down as an 'extra service'.
>Nither do the Russians. Return space for the base experiments is included.
>If the French budget their weight carefully, they need pay no more.
So what was the $51,000/kg for, then? Was it for extra above some base
value? If so, how much?
Allen W. Sherzer
>>Don't quibble and answer the question: if it where YOUR money, which
>>option would you sign up for?
>Don't quibble? You quote meaningless numbers
Your quibbling because you don't want to answer. No court in the world would
consider the contract signed between France and Russia meaningless.
Are you saying that these mission's won't fly? Then just why is the French
government contracting for them?
Now answer the question: if it where your money, which would you choose?
>>>And as for 'extra services' costing more; I don't regard getting your
>>>payload down as an 'extra service'.
>>Nither do the Russians. Return space for the base experiments is included.
>>If the French budget their weight carefully, they need pay no more.
>So what was the $51,000/kg for, then? Was it for extra above some base
>value?
Yep.
>If so, how much?
If you mean how much do they get to return, I don't know. If you mean
how much extra can they return, as much as they are willing to pay
for.
Allen
Allen W. Sherzer
>Okay. Allen, if the French fly a payload on the Shuttle for $52 million,
>and the flight is 10 days in duration, do you think they turn it off after
>a single day? Your dollar division is hopelessly simplistic, which is why
>I called it pathetic.
Huh? What does that have to do with anything? but if you don't like it,
fine. We know what we get for $52M with the Russians. But please fix my
errors and tell me just how much of a $600M Shuttle flight should somebody
get for $52M? According to my calculator that come to about 8.5% of the flight.
I welcome your documented correction of my error.
allen
hvanderbilt on BIX
>
>My feeling, and this is based on a lot of thought, is that the SSME is
>the very minimum performance that should be considered for any
>future vehicle, and that a new engine must have better performance
>and better operability, both, or it is a "non starter." And, for those
>that think that we should go back to a more robust, but lower
>performance engine, please tell me where there is a parallel for that
>in airplanes, automobiles, etc. in which engine performance is not
>nearly so critical from an economic standpoint as it is in space
>vehicles.
>
>Boosters, and especially SSTO's are at least as performance critical as
>air superiority fighters. People that say give back a few seconds of
>Isp so that the engine is more robust are the same ones that were
>telling Spitfire and Mustang pilots that if they didn't use such high
>boosts when running from FW 190's they would get longer engine
>life. It isn't cost effective to derate transport engines, much less
>fighter engines. And gravity is every bit as tough an opponent as an
>enemy fighter.
>
Required engine performance for a useful SSTO is another one of those
areas where reasonable people can differ. The tradeoff for engine
performance is of course mass ratio; lower engine performance means
you need ship+payload to be a smaller fraction of the gross liftoff
weight. Some people think they can build a useful (at least for proof-
of-concept purposes) reusable SSTO at slightly lower ship+payload
mass fraction than SSME performance would allow.
Some people think they can build useful SSTO's at a *lot* lower mass
fraction than SSME's would allow, but then they're looking at much
higher density propellants than LOX/LH, which allows them to assume
lighter tanks and higher thrust-to-weight engines to make up for the
lower Isp. Life is just full of interesting tradeoffs -- the main
point is that we seem to have a reasonable range of tradeoffs based
on reasonable assumptions about engine performance and structure weights
that allow for a reasonable chance of positive payload to orbit SSTO's.
All other things being equal, of course, higher engine performance is a
great boon to anyone designing an SSTO, allowing less toil, tears, sweat,
and money to be spent on shaving vehicle dry weight.
Henry Vanderbilt hvand...@bix.com
Doug Mohney
>to Henry Hilbraith is keeping the LOX from binding wiht terrestrial
>hydro-carbons, then it becomes very problematic.
LOX makes lots of things burn well.
It'll all depend on how much LOX is left. You also have to remember that
the cabin will be somewhere on top of the cracked LH tankage, conveniently
BBQing away...
Of course, that assumes a perfect landing tail-down and perfect crunch...
it's hard to say how much control you'd have augering in since you now have no
(zip) engine power. Tilt the thing off its normal vertical landing and who
knows what might happen.
Further, you get into some interesting factors like will I be lucky enough
to fall on water, soft ground, hard ground, houses, concrete, the LOX storage
facility...
I suppose it would be fun to take the DC-X and crash it on a concrete surface
just to see what would happen after all the other tests are run...
January 1993 - John Scully embraces Bill Clinton.
July 1993 - Apple Computer lays off 2500 workers, posts $188
million dollar loss.
-- > SYS...@CADLAB.ENG.UMD.EDU < --
Doug Mohney
>In article <24pff8...@phantom.gatech.edu> mat...@phantom.gatech.edu (Matthew DeLuca) writes:
>>Oh, let me guess: you divided $52 million by $500 million to get your
>>above '10%' figure?
>Yep, and a rough estimate of person days in space. All in all, for $52M
>you can buy 160 or so days on Mir or less than 10% of a Shuttle flight.
>
>If you don't like the methods I used, then substitute your own and
>justify it. But don't call it patethic until you do.
Matt, remember, you are supposed to scribble on the back of better envelope
than he does, preferably one of those fancy jobs rather than a standard
white one....
After all skeptics aren't permitted off-the-cuff statements until we use
calculators in more creative ways.
Gary Coffman
It's easiest if we figure a crash just after takeoff with the tankage
full. Then all we have to know is the hoop strength of the tankage
since the fuel is incompressable and is going to rupture the tankage.
The remaining strength of the tank after spliting is so little as
to be not worth considering by comparison.
Modelling the nearly empty tank is a bit harder since it mostly
contains compressible gas. It's a big gas shock until it ruptures.
In either case, after rupture, likely a lengthwise split, the
tank structural strength will be very little, basically just the
bending resistance of sheet material. If we could vent the tank
to prevent rupture, then we could model it as a hollow column
in compression. But if the crash forces are asymetric, it'll
buckle quickly and lose most of it's column strength.
The parameter we need to know is the PSI limit of the tankage,
and an estimate of the mass of remaining fuel. Almost all the
energy absorbed is going to go into propelling fuel in lateral
directions.
Ideal crush structures are vented honeycombs. They are stable
against symetric and asymetric forces and crush at a rate
proportional to the elongation stress on the cell walls. A
skeleton version of the honeycomb is the space frame used
in race cars. There, tubes in tension determine the rate
of collapse of the structure.
Herman Rubin
>>>>1. 220 pound payload for 30 days 1. About 3.5 days on Shuttle
>>>BTW, that's 3.5 person days, not 3.5 days of Shuttle time. It's less than
>>>10% of a flight.
>>Oh, let me guess: you divided $52 million by $500 million to get your
>>above '10%' figure?
>Yep, and a rough estimate of person days in space. All in all, for $52M
>you can buy 160 or so days on Mir or less than 10% of a Shuttle flight.
Person days are far from the whole story. Would we send someone to
just spend 160 or so days doing nothing? We know that people in good
condition can spend such a period of time in space without overly
drastic consequences. I can think of meaningful experiments to perform
requiring merely time, but I doubt that they will be done in the near
future.
--
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: (317)494-6054
hru...@snap.stat.purdue.edu (Internet, bitnet)
{purdue,pur-ee}!snap.stat!hrubin(UUCP)
Gary Coffman
>In article <1993Aug15....@ke4zv.uucp>,
>Gary Coffman <ga...@ke4zv.UUCP> wrote:
>>George, have you ever inspected an Indy car or Stock Car carefully.
>>I have, I've raced stock cars. Almost all their mass, aside from
>>the engine and drivetrain, is devoted to maintaining integrity during
>>a crash [...]
>, even the engine is used as a load bearing member. *And* almost
>>all crashes are either with other cars going about the same speed and
>>direction, or glancing strikes to crash barrier walls. Drive any
>>racecar into an unyielding head on barrier at 200 MPH and I can
>>almost guarantee 100% fatalities. A NASCAR racer carries 350 lbs
>>of fuel in a 4000 lb car. I don't think that describes an SSTO
>>very well.
>
>Gary,
>SSTO is among the most survivable in a crash vehicles I can think of.
>Why? Presuming it's going backwards, with the people at the top,
>like it's supposed to be (all bets off otherwise), you will have 20
>meters of crush zone to absorb energy before the pilot reaches ground
>level. 200 mph is what, 100ish meters per second? That's about 0.4
>second of decelleration, or an average of 250 m/s^2 decelleration
>or 25 Gs. People survive 100 G impacts quite easily, in properly
>designed seats they're well strapped into. We're talking about
>1/4 of that average force. 100 MPH into a wall with 1 meter
>of crush space (Average race car) is about 100 G's, and I've met
>many people who survived 100 MPH headon impacts with walls. Dad
>used to race cars, though he never really crashed one (he went off
>the track once, though...). 200 MPH into a wall in the same
>crush space is 400 G's, but we're not talking about one meter
>of crush space. We have a whole rocket stage under you to absorb
>the energy.
You're assuming the tanks will crush like the designed spaceframes
of racecars. Unless they are a lot heavier than they need to be,
they won't. Once the hoop stress factor is exceeded, they'll rupture,
likely by spliting down the side, and fold up like old newspaper.
>>I wouldn't be so sure of that either. Halon systems on racecars
>>can handle fires from oil or fuel line ruptures, but don't have
>>a chance in hell of dealing with a ruptured fuel cell. That's
>>why the fuel cells are so big and heavy, so they *won't* rupture
>>in a crash. You can't do that with the SSTO's tankage.
>
>You don't have to; identify the parts of the vehicle likely to
>start fires (engine compartment, maybe APU spaces) and halon
>them. Dump the LOX if you can before you impact; without that,
>LH2 is pretty safe in a fire, as it evaporates and goes UP
>and doesn't burn that hot even if a fire does start.
Anything, including a spark from a tearing tank, can ignite the
LH2. The flamefront will be confined to an expanding spherical
wavefront where air and hydrogen mix at the limits of flammability.
But since the tanks will rupture from mechanical stress, that
cloud is going to develop very quickly as the fuel is sprayed
out under high pressure. It would be somewhat akin to a FAE
munition. It would be even more so it the spark is delayed
by a fractional second, say from the electronics crushing in the
passenger compartment, to allow better premixing.
Pat
For what it's worth, the Liberty SHips used far lower performance engines
then the conventional ships of the time.
they used steam engines rather then low pressure turbines.
Also, the conversion from tubes - germanium to silicon were
all initially lower performance then the preceding technology.
Keith Mancus
>In article <24oso5...@phantom.gatech.edu>,
>Matthew DeLuca <mat...@phantom.gatech.edu> wrote:
>>You mean those guys who charged the French $17,000/kg on the way up, and
>>$51,000/kg on the way down, with a 200kg limit?
>That's not fair, Matthew. The Russians only did this because they
>need money bad, and the French had effectively deep pockets, and
>the Russians were able to put the screws on a bit to up their profits
>for the whole endeavour. If you buy and launch a Kvant module,
In other words, the Russians are getting to be pretty good capitalists. :-)
--
The opinions expressed are not necessarily those of the University of
North Carolina at Chapel Hill, the Campus Office for Information
Technology, or the Experimental Bulletin Board Service.
internet: laUNChpad.unc.edu or 152.2.22.80
Matthew DeLuca
>In article <24q8rg...@phantom.gatech.edu> mat...@phantom.gatech.edu (Matthew DeLuca) writes:
>>Don't quibble? You quote meaningless numbers
>Are you saying that these mission's won't fly? Then just why is the French
>government contracting for them?
Good question. I wonder how much the French have budgeted for 'extra'
fees likely to be imposed by the Russians.
I'm going to make a prediction, that in each flight in this contract there
will be some signifigant (millions of dollars) fees added on, and that the
French will pay so as not to invalidate the investment they have already
made. We'll judge the value of this contract after they actually fly.
>Now answer the question: if it where your money, which would you choose?
Depends on what I was trying to do. Of course, the proper way to evaluate
the choice between the U.S. and the Russians is to decide what my goal is,
and then ask each potential provider for a cost quote. I doubt the French
sat down one day and said to themselves, "Gee, wonder what we could get in
space for $52 million" (although if they did, I am sure they said it in
French :), they more likely had a goal in mind and worked from there.
>If you mean how much do they get to return, I don't know. If you mean
>how much extra can they return, as much as they are willing to pay
>for.
A question: how can they return more than they sent up? I'm not sure I
accept that there is a base return value and then a charge for extra; where
does the extra come from?
Maybe they should look into the U.S. after all. To use your overly simplistic
figures, $52 million is approximately 10% of a flight, which translates to
roughly 5,000 pounds of gear. At the rates charged by the Russians, that has
a return value of approximately $125 million.
Bill Higgins-- Beam Jockey
> In article <1993Aug14.1...@iti.org> a...@iti.org (Allen W. Sherzer) writes:
> In article <1993Aug14.1...@osuunx.ucc.okstate.edu> u10...@unx.ucc.okstate.edu (11086) writes:
> >Since I've seen this twice now...remember that Indy cars very rarely hit
> ??? Engine out, coming down, how do you avoid head-on?
> Tilt the Earth? ;-)
> I presume you do not intend all engine-outs to happen
> in narrow, high valleys,
Ah, but you get more points for landing in such places.
(Do today's kids still play Lunar Lander?)
>so I presume you're saying the
> SSTO will typically come in obliquely for the last 20k ft,
> not straight?
Bill Higgins | In the distant future,
Fermi National Accelerator Laboratory | nuns will be bartenders
Bitnet: HIG...@FNAL.BITNET | aboard starships
Internet: HIG...@FNAL.FNAL.GOV | and Sternbach paintings
SPAN/Hepnet: 43011::HIGGINS | will hang on every wall.
Henry Spencer
>BTW, two U. S. manned launches had a "loss of thrust" in liquid
>propulsion systems, which not only did not result in fatalities, but in
>one case, was so little noticed and commented on that I doubt if
>anyone but "Henrys" know about it. (I sure hope one of the other
>ones does, or I will have to look it up! It didn't even make my
Apollo 13 lost the center engine on its S-II midway up. The other four
burned longer than usual to use up the fuel, and the S-IVB likewise did
an extra-long burn to compensate. (There was some concern about whether
the S-IVB still had enough fuel for the second burn, but in fact it did.)
This was so thoroughly overshadowed by later events :-) that a lot of
Apollo-history books don't even mention it. "Moonport" says that the
problem was pogo oscillations, in the second stage this time, but doesn't
go into detail about how this caused the shutdown. (If I were to guess,
I'd say that the shutdown -- which was supposed to happen, but 2min later,
to reduce maximum acceleration -- was triggered by a specific acceleration
level, and the pogo fooled the accelerometers or the software behind them.)
--
"Every time I inspect the mechanism | Henry Spencer @ U of Toronto Zoology
closely, more pieces fall off." | he...@zoo.toronto.edu utzoo!henry
George William Herbert
Gary Coffman <ga...@ke4zv.UUCP> wrote:
>You're assuming the tanks will crush like the designed spaceframes
>of racecars. Unless they are a lot heavier than they need to be,
>they won't. Once the hoop stress factor is exceeded, they'll rupture,
>likely by spliting down the side, and fold up like old newspaper.
Ah, I was assuming the tank was nearly empty (full of gas) in a
landing accident, not a takeoff accident. From what I've seen on
plans for Delta Clipper, it's got multiple tanks in a four-square
arrangement under the payload space, which should resist the
sort of crumple you're describing better than one big tank will.
>Anything, including a spark from a tearing tank, can ignite the
>LH2. The flamefront will be confined to an expanding spherical
>wavefront where air and hydrogen mix at the limits of flammability.
>But since the tanks will rupture from mechanical stress, that
>cloud is going to develop very quickly as the fuel is sprayed
>out under high pressure. It would be somewhat akin to a FAE
>munition. It would be even more so it the spark is delayed
>by a fractional second, say from the electronics crushing in the
>passenger compartment, to allow better premixing.
I thought that LH was a particularly bad thing to make FAE
bombs out of; it always evaporates slowly in air, fast in a fire
but not burning hot. An explosion from this sort of accident?
That's a possibility, but... hmm. I'll tell you what. If you have
a suitable test facility and will buy the LH, I'll build a scaled
model and see if we can blow it up or if it burns safely.
Presuming my personal finances aren't quite so tight in a month.
-george william herbert
Retro Aerospace
George William Herbert
Matthew DeLuca <mat...@phantom.gatech.edu> wrote:
>So what was the $51,000/kg for, then? Was it for extra above some base
>value? If so, how much?
I believe from what's being said that this is the case; $51,000/kg
for mass above the previously agreed upon limits, because the Russians
will have to de-manifest things once those limits are reached
and don't like that idea.
[Again, I don't know for sure]
-george
Rick Snydersmith 303 971-6100
Indy car and Formula 1 and Stock Car and GT race cars all meet
the "survive the impact" criterion for the crews.
Did you try to consider the MASS of the craft into your estimate? 200
MPH is only part of the total force.
The explosion is another issue. That can be avoided with a little
Halon (and I think the Ozone layer will begrudge you a bit of
damage in this case...).
Providing that the craft accomidates you and falls where your halon system
is, maybe. But it sure makes a mess and would kill any crew at the same time.
Rick SnyderSmith
disclaimer:
Any opinions stated within the above message are entirely my own thoughts or in
the case of legal suit, they are the official position of the Democratic party.
Regardless, my employer disavows any knowledge of my actions. This message will
self destruct in 10 seconds.
Rick Snydersmith 303 971-6100
>the wall head on at 200 mph.
Nither would an SSTO.
Are you stating the DC-X would glance off the Earth? Or just not hit a wall
head on at 200 MPH.
Rick SnyderSmith
Without starting a spelling duel it is neither not nither.
Matthew DeLuca
This makes sense...although now something else bothers me; how do what's
coming down and what's going up differ in mass? Either the base return
doesn't include all of the basic gear sent up, or they're bringing other
stuff with them on the way down.
Does anyone know exactly what they took up with them, anyway?
h.hil...@genie.geis.com
> "Allen W. Sherzer" <a...@iti.org>
Writes:
> Hydrogen is much less explosive then whatever fuel your airliner
> is burning. Most fatalities from airliner crashes happen from their
> lovely explosion afterwards (although nither explodes). So this
> is a common threat to safety and applies at least as much
> to airliners.
There is often a big disconnect between "technical" and "general"
discussions, but I find that when it comes to "explosions" that there
often seems to be no connection between the technical and non
technical views, at all.
Hydrogen and kerosene (what most of "your airliners are burning,"
currently) are fuels, and neither has ANY explosive potential unless
it is mixed with an oxidizer.
Despite every auto crash scene in every movie ever made, it is very
hard to get kerosene, gasoline, or any heavy hydrocarbon to
"explode" at all, with air. (It is really hard to get any "blast
overpressure" or "explosive yield." The actually definition of
"explosion" may be so weak as to be that a sound is produced, you
can manage that with kerosene, fairly well.)
What is easy, in an air crash, is to get a heck of a fire. Airliners burn,
but do not "explode" (usually. I can't understand it that is what you
are trying to say, or not.) The relative severity of the fire would be
related to the size of the rocket and the airplane. For rockets, a
kerosene fire would likely be more severe than the fire would be
with an amount of hydrogen that would be required for the same
launch vehicle function.
With LOX, on the other hand, it is relatively easy to get kerosene,
gasoline, etc. to explode in a fashion that would satisfy anyone. Real,
"high order," detonations. Ones that will curl your hair (for those that
still have any.)
Sort of "3 sigma" worst case, was the only Titan I that ever came
close to getting launched from VAFB, and from a silo. After a
propellant loading, as the missile was being lowered back into the
hole, the elevator hit the down stops, rather more abruptly than
intended. Both first stage tanks apparently ruptured, there was a
"pregnant pause," and the entire guts of the silo was disgorged.
After that, I often made the statement that it was not possible to get
"yield" from liquid propellant rockets, unless one had confinement,
and premixing, and that unless one dropped them in holes, like the
Titan, you wouldn't get either. Then there was an Atlas that I got to
see, close up and personal, a few minutes after the LOX pump split
into, one half apparently going out through the top of the tank. The
fact that the test stand was rotated 90 degrees by the event led
me to believe that you could, sometimes, get some yield, even in a
case were the only confinement was the ground.
I don't know of and yield estimates from that one, but another one,
Atlas Centaur 5 (a "fall back") was well documented, and had a yield
of a few percent TNT equivalent, in some directions.
Liquid hydrogen, on the other hand, is physically incompatible with
LOX, and usually disperses and burns with hardly any effect at all.
That is if you are lucky.
If, on the other hand, if you are not lucky (which is the way one does
hazard evaluations, I hope), it is quite easy to get a lot of hydrogen
vapor, and if the vapor is premixed with the right amount of air, you
can get a "Vapor Cloud Detonation." (Called a "Fuel Air Explosion"
when it is done deliberately.) It is not at all easy to do that, but it can
be done, and has been done in tests of propellant hazards.. And,
though the LOX is not involved, the equivalent yield of the hydrogen
and air comes reasonably close to the yield of an amount of TNT
equal to the COMBINED hydrogen/LOX weights. That is enormously
more than the potential yield of the kerosene in a flock of Jumbo
Jets, but not so much as the LOX/kerosene yield of a rocket of the
same lift capability as a LOX/LH2 one.
So, in any ordinary sense, I think that hydrogen is MORE explosive
than any airliner fuel could be. And the fuel in a landing SSTO has to
be considered a hazard to the crew, and more especially, to anyone
that the vehicle happened to fall on, in an accident.
Besides the hazard of the fuel, there is also the hazard of the LOX,
which isn't trivial, and isn't necessarily helped by a "dump,"
particularly not in a vertical descent.
And, if you try to land your rocket in MY back yard, please expect
me, and others, to make that point, loudly and publicly. Rockets are
not safe, not as safe as airliners, and it doesn't matter how many
stages they have, and they are probably not as safe coming down as
going up. (IMHO, wings make them a lot safer than legs, but I will
admit that I have a vested interest in that position.)
I am not even going to address the question of comparing the
survivability of an SSTO to a Indy car. No comment.
Henry S. Hillbrath
----------------------------------------------------------
NO ONE believes an analysis... | EVERYONE believes a.test...
- except the guy who did it. | - except the guy who did it.
T. M. ("Scotty") Davidson
Allen W. Sherzer
>This makes sense...although now something else bothers me; how do what's
>coming down and what's going up differ in mass?
From what I have read, it appears that only the data and samples will be
returned. The experiments will be left behind. In fact, to reduce
development time and costs, the French will be using an experiment they
themselves flew a few years ago and left behind. Unlike us, the Russians
can leave hardware up there for use later. They needn't spend hundreds
of millions hauling it back down just to haul it back up again.
BTW, the Russians are charging the French to use the hardware the
French left behind.
Allen
Matthew DeLuca
>Unlike us, the Russians
>can leave hardware up there for use later. They needn't spend hundreds
>of millions hauling it back down just to haul it back up again.
I think it's *have* to leave it up there, not *can* leave it up there, due
to their lack of return capability. From what I read, they are having to
cram stuff in airlocks to make enough room.
yancy l shirley
>In article <24mplh$q...@agate.berkeley.edu> g...@soda.berkeley.edu (George William Herbert) writes:
>>In article <1993Aug15....@ke4zv.uucp>,
>>Gary Coffman <ga...@ke4zv.UUCP> wrote:
>>>George, have you ever inspected an Indy car or Stock Car carefully.
>>>I have, I've raced stock cars. Almost all their mass, aside from
>>>the engine and drivetrain, is devoted to maintaining integrity during
>>>a crash [...]
>>, even the engine is used as a load bearing member. *And* almost
>>>all crashes are either with other cars going about the same speed and
>>>direction, or glancing strikes to crash barrier walls. Drive any
>>>racecar into an unyielding head on barrier at 200 MPH and I can
>>>almost guarantee 100% fatalities. A NASCAR racer carries 350 lbs
>>>of fuel in a 4000 lb car. I don't think that describes an SSTO
>>>very well.
One last note on INDY cars... Indy cars are meant to hold integrity
ONLY WHERE THE DRIVER SITS... this region is known as the "tub". When an
INDY car impacts the wall... the carbon-fiber body flies off.. carrying with
it momentum, etc. The new indy desingns on the nose of the car are designed
to deform (to carry the momentum and to keep the drivers feet from sustaining
an impact with the wall). General Motors with Delco Electronics has desinged
a black box that analyzes head on crashes in INDY cars. Part of the tradeoff
(as i understand it) is momenutm transfer vs. deformity... for if the nose
section deforms too much, the driver's feet become exposed. That's why nose sections
were lengthened ... to help the tradeoff. Not all the mass in INDY cars are used
for integrity. If that were the case.. the driver would feel a MASSIVE impulse
when he hit the wall (surely fatal). This is case-in-point. Look at INDY cars
in the 1960s. How many drivers lost their lives beacuse they hit the wall in
solid-body chassis ??? LOTS. Nearly every year at indy in the 60s, a driver
lost his life. Now, you don't see that anymore because INDY cars are built to
fly apart everywhere except where the driver sits.
Yancy Shirley
Michael C. Jensen
: Allen W. Sherzer wrote:
: >>Don't quibble? You quote meaningless numbers
: >Are you saying that these mission's won't fly? Then just why is the French
: >government contracting for them?
: Good question. I wonder how much the French have budgeted for 'extra'
: fees likely to be imposed by the Russians.
: I'm going to make a prediction, that in each flight in this contract there
: will be some signifigant (millions of dollars) fees added on, and that the
: French will pay so as not to invalidate the investment they have already
: made. We'll judge the value of this contract after they actually fly.
Um, just to be accurate, if I understand the quotes properly, it costs
the French $52 million to get 165 days plus blah blah blah on russian
systems, and 3.5 days on the shuttle. Now it appears to me that you
MAY be miscalculating one or the other of the two costs. If you are
dividing the total mission cost by money spent to fly, then the
russian number appears wrong, but if you are meerly totaling actual
flight costs charged to the govt vs time and payload capabilities, then
your US launcher values are off. Or did I misunderstand the original posts?
Mike
--
mje...@gem.valpo.edu "I bet the human brain is a kludge." -- Marvin Minsky
jen...@cisv.jsc.nasa.gov *WindowsNT - From the people who brought you edlin*
---Disclaimer: The opinions expressed are my own... ---
Henry Spencer
>And, if you try to land your rocket in MY back yard, please expect
>me, and others, to make that point, loudly and publicly. Rockets are
>not safe, not as safe as airliners, and it doesn't matter how many
>stages they have, and they are probably not as safe coming down as
>going up. (IMHO, wings make them a lot safer than legs, but I will
>admit that I have a vested interest in that position.)
Actually, from the viewpoint of the guy with the back yard, wings
make them *less* safe than legs. A wingless craft will necessarily
be coming almost straight down on its landing approach, meaning that
a crash due to a late malfunction is likely to be within the grounds
of the airport/spaceport. (A crash due to an early malfunction could
be anywhere with either type of craft.) Things with wings, making
near-horizontal approaches, are much more dangerous to the neighbors.