Briefing on SRB based CEV at NPS with Scott Horowitz
Tom Cuddihy
Postgraduate school today to teach a lecture to my class of Space
Systems Engineers & gave a very convincing argument for the SRB to
orbit option. (He works for ATK, but keep reading.) There were quite a
few details that I found interesting in his talk, and many of my intial
skepticisms about the idea were soundly refuted.
Here's a synopsis:
The summer of 2003, after OSP was announced and most of the spaceflight
office at Johnson was shaking their heads, several of the engineers
started looking at this option as an alternative after OSP was
inevitably cancelled.
What they determined from an overall perspective (much like the SpaceX
Futron study) is that maximizing reliability on larger systems means
minimizing component integration complexities--something the shuttle is
particularly ghastly at, and even EELVs like the Delta-IVH, with 3
cores, are bad about. (witness the first delta IV H failed!). That
means best reliability comes with 1 first stage engine, 1 separation
event, and 1 second stage engine.
The problem is that no liquid engines currently exist that are powerful
enough to (with one engine) thrust the first stage of a manned capsule
off the pad. Solution--make the first stage an SRB (3 million lbs of
thrust).
I've heard all this before, and I had some preconceived skepticisms,
among them:
1. Didn't an SRB failure cause the Challenger accident?
2. Don't SRB's cost alot?
3. Isn't that too much thrust to handle for a small vehicle?
4. thus Wouldn't extensive modifications to the burn profile be
required, costing even more?
5. Does the steerable nozzle have enough control authority?
Scott Horowitz was pretty convincing that these are not legitimate
concerns, for the following reasons:
1. Yes, but the explosion happened because hot gas burned through the
LOX/H2 tank. Solid rockets don't explode. If there wasn't a fuel tank
in the way, the Challenger probably still could have made orbit, as
most of the thrust was still going out the nozzle. Solid boosters DONT
explode like Lox/ H2, they just leak hot gas. A capsule on top of a
worst-case failed SRB (case burst, which has never happened in 240 some
SRB flights), even on the ground, where propogation is the worst, sees
only a 10 psi overpressure. Very survivable.
2. Yes, the shuttle contract costs the govt a fixed amount--but it
generally operates at ~15-20% of capability. In other words, if the
line is going to stay open through 2010 for shuttle anyway, why not use
that extra capacity to built boosters?
3. No, just put a bigger second stage on top of the SRB and
voila--thanks to the rocket equation, G loading is as variable as you
want to make the second stage. With an RP-1/Lox upperstage, Isp ~340,
and 250,000lbs propellant, a 28,000 lb payload (Astronauts) see a max
of 3Gs of acceleration, and a max Q about the same as the shuttle.
4. No, all proposed schemes use the exact same burn profile as the
shuttle SRB. In fact, it is a shuttle SRB with different GNC software
and an interstage instead of a nosecose.
5. Absolutely, in fact, it can launch under worse conditions than the
shuttle. Finite element analysis modeling shows that with the ker/lox
upperstage, CG, or rather cm is in about the same place as the shuttle,
and even under worse case wind conditions, etc, the steerable nozzle
has more than enough control authority to handle it, and lots of margin
to spare.
Some other points he made:
6. the reliability and safety of the SRB is extremely well known--thus
the system reliability depends nearly entirely on the reliability of
the second stage. For the 'best fit' notional model, he was using a
Saturn V J2S, although it works with a J2. That would require
re-developing the big ker/lox engine--big deal and much moolah, but it
would probably be a popular project. Also, rocketdyne has kept much of
the J2 knoweledge in working order, even using the turbopumps on the
X-33 linear aerospikes. It could probably be done pretty quickly.
7. One of the first people outside-of-NASA people briefed in on this as
a "reality check" was the then-head of APL, Mike Griffen. And he
apparently was very impressed by its possibilities for success. So
support inside NASA should not be a problem.
8. We should know if this is going forward within the next 2 months,
because that's the time limit to complete a people carrying version by
2010. If a decision is not made by then, it's not going to happen. So
standby...
Tom Cuddihy
Jeff Findley
Apparantly he left out the part where large segmented solids have gone
"boom" in the past. See Titan IV failure caused by a design flaw in the
propellant grain at the joints. The joints in large segmented solids are
definately a problem and can go "boom".
Jeff
--
Remove icky phrase from email address to get a valid address.
lex...@ix.netcom.com
gone
"boom" in the past.
That has never happened with the Shuttle motors in either flight or
groudn test.
George William Herbert
Right.
The Challenger type burnthrough would be relatively harmless on
a single SRB first stage; there's nothing for it to cut into and
cause to fail, other than slowly eroding a hole in the SRB.
Which the Challenger burnthrough would not have done fast enough
to cause a flight accident, if I recall the analysis right.
You have to have enough control authority if there's sideways
thrust and loss of thrust due to such a burnthrough, but that
should be manageable.
Having the nozzle depart would likewise be spectacular but
fairly safe.
But... large SRBs *have* catastrophically dissassembled
themselves or outright exploded recently. Any large SRB
that got an internal flow disruption due to propellant
grain structural failure could CATO.
Can an overall launcher be safe enough to be escapable
in case of CATO? Probably. Big bad day though.
-george william herbert
gher...@retro.com
Jake McGuire
True, but "The shuttle RSRMs have never gone BOOM" is a much weaker
statement than "solid rocket motors don't go BOOM." I seem to recall a
Delta solid going BOOM and raining bits of GPS satellite all over a
bunch of parked cars a few years back as well.
Without hearing Horowitz's defense of the SRBs word-for-word it's hard
to be specific, but claiming that "if there wasn't a fuel tank in the
way, Challenger would still have probably made orbit, as most of the
thrust was still going out the nozzle" strikes me as verging on
dishonest. If the contents of the ET were somehow magically rendered
inert, the flame from the SRB was still going to cause failure of the
aft attachment point and subsequent mechanical failure of the entire ET
and aerodynamic destruction of the stack.
-jake
George William Herbert
>Scott Horowitz, former shuttle pilot and astronaut, came to the Naval
>Postgraduate school today to teach a lecture to my class of Space
>Systems Engineers & gave a very convincing argument for the SRB to
>orbit option. (He works for ATK, but keep reading.) There were quite a
>few details that I found interesting in his talk, and many of my intial
>skepticisms about the idea were soundly refuted.
Too bad nobody told me it was happening, I would have driven down
and offered some useful criticism...
>Here's a synopsis:
>The summer of 2003, after OSP was announced and most of the spaceflight
>office at Johnson was shaking their heads, several of the engineers
>started looking at this option as an alternative after OSP was
>inevitably cancelled.
>What they determined from an overall perspective (much like the SpaceX
>Futron study) is that maximizing reliability on larger systems means
>minimizing component integration complexities--something the shuttle is
>particularly ghastly at, and even EELVs like the Delta-IVH, with 3
>cores, are bad about. (witness the first delta IV H failed!). That
>means best reliability comes with 1 first stage engine, 1 separation
>event, and 1 second stage engine.
>The problem is that no liquid engines currently exist that are powerful
>enough to (with one engine) thrust the first stage of a manned capsule
>off the pad.
This is not true. Both the Atlas V and Delta IV boosterless models
have enough weight to orbit a reasonably designed midsized capsule
with 4-6 seats. Both are single engine first stage launchers.
The other peak in reliability should come around 5 or more engines
per stage, as Saturn V's S-IC, S-II, and the upcoming Falcon V
first stage all do. But it's harder to engineer and will have
more soft failures than single engine stages.
>Solution--make the first stage an SRB (3 million lbs of
>thrust).
>
>
>I've heard all this before, and I had some preconceived skepticisms,
>among them:
>1. Didn't an SRB failure cause the Challenger accident?
>2. Don't SRB's cost alot?
>3. Isn't that too much thrust to handle for a small vehicle?
>4. thus Wouldn't extensive modifications to the burn profile be
>required, costing even more?
>5. Does the steerable nozzle have enough control authority?
>
>Scott Horowitz was pretty convincing that these are not legitimate
>concerns, for the following reasons:
>1. Yes, but the explosion happened because hot gas burned through the
>LOX/H2 tank. Solid rockets don't explode.
Large solid rockets can catstrophically fail, and have both
in ground test and flight recently. Titan IV had a really truly
spectacular ground test failure. A Delta II had a GEM let go
and blow chunks of the launch vehicle all over the pad, blockhouse,
and parking lot (and the Cape's air force museum).
>If there wasn't a fuel tank
>in the way, the Challenger probably still could have made orbit, as
>most of the thrust was still going out the nozzle. Solid boosters DONT
>explode like Lox/ H2, they just leak hot gas. A capsule on top of a
>worst-case failed SRB (case burst, which has never happened in 240 some
>SRB flights), even on the ground, where propogation is the worst, sees
>only a 10 psi overpressure. Very survivable.
10 psi overpressure is a lot. Well built concrete
buildings get knocked down by 10 psi overpressure.
It won't kill the people, but it may damage a capsule
beyond safe escape or post-escape landing.
>2. Yes, the shuttle contract costs the govt a fixed amount--but it
>generally operates at ~15-20% of capability. In other words, if the
>line is going to stay open through 2010 for shuttle anyway, why not use
>that extra capacity to built boosters?
>3. No, just put a bigger second stage on top of the SRB and
>voila--thanks to the rocket equation, G loading is as variable as you
>want to make the second stage. With an RP-1/Lox upperstage, Isp ~340,
>and 250,000lbs propellant, a 28,000 lb payload (Astronauts) see a max
>of 3Gs of acceleration, and a max Q about the same as the shuttle.
>4. No, all proposed schemes use the exact same burn profile as the
>shuttle SRB. In fact, it is a shuttle SRB with different GNC software
>and an interstage instead of a nosecose.
What, no gentler thrust termination system?
>5. Absolutely, in fact, it can launch under worse conditions than the
>shuttle. Finite element analysis modeling shows that with the ker/lox
>upperstage, CG, or rather cm is in about the same place as the shuttle,
>and even under worse case wind conditions, etc, the steerable nozzle
>has more than enough control authority to handle it, and lots of margin
>to spare.
>
>Some other points he made:
>6. the reliability and safety of the SRB is extremely well known--thus
>the system reliability depends nearly entirely on the reliability of
>the second stage. For the 'best fit' notional model, he was using a
>Saturn V J2S, although it works with a J2. That would require
>re-developing the big ker/lox engine--big deal and much moolah, but it
>would probably be a popular project. Also, rocketdyne has kept much of
>the J2 knoweledge in working order, even using the turbopumps on the
>X-33 linear aerospikes. It could probably be done pretty quickly.
There has to have been some error there; the J-2s were LOX/LH2
upper stage engines, not lox/kerosene as described elsewhere
and partly here.
J-2 isn't a bad choice, nor is LOX/LH2 for the upper stage,
but clarification would have been nice.
>7. One of the first people outside-of-NASA people briefed in on this as
>a "reality check" was the then-head of APL, Mike Griffen. And he
>apparently was very impressed by its possibilities for success. So
>support inside NASA should not be a problem.
>8. We should know if this is going forward within the next 2 months,
>because that's the time limit to complete a people carrying version by
>2010. If a decision is not made by then, it's not going to happen. So
>standby...
This launcher may well happen, but I remain unconvinced
that it's really a better choice than either of the two
EELVs in their boosterless configuration.
I do have this crazy idea to see what happens if you stack
a Delta IV core on top of a SRB, though...
-george william herbert
gher...@retro.com
Murray Anderson
"Tom Cuddihy" <tom.c...@gmail.com> wrote in message
news:1116009407.5...@o13g2000cwo.googlegroups.com...
> Scott Horowitz, former shuttle pilot and astronaut, came to the Naval
> Postgraduate school today to teach a lecture to my class of Space
> Systems Engineers & gave a very convincing argument for the SRB to
> orbit option. (He works for ATK, but keep reading.) There were quite a
> few details that I found interesting in his talk, and many of my intial
> skepticisms about the idea were soundly refuted.
>
> Here's a synopsis:
> The summer of 2003, after OSP was announced and most of the spaceflight
> office at Johnson was shaking their heads, several of the engineers
> started looking at this option as an alternative after OSP was
> inevitably cancelled.
> What they determined from an overall perspective (much like the SpaceX
> Futron study) is that maximizing reliability on larger systems means
> minimizing component integration complexities--something the shuttle is
> particularly ghastly at, and even EELVs like the Delta-IVH, with 3
> cores, are bad about. (witness the first delta IV H failed!). That
> means best reliability comes with 1 first stage engine, 1 separation
> event, and 1 second stage engine.
> The problem is that no liquid engines currently exist that are powerful
> enough to (with one engine) thrust the first stage of a manned capsule
> off the pad. Solution--make the first stage an SRB (3 million lbs of
> thrust).
>
The RD-171 has 740 tons of thrust, so I suppose this means no U.S. engine. A
good reason for bringing back the F1.
Isp of 340 seconds is very high for a gas generator cycle lox-kero engine.
You would need an expansion ratio of about 200. A version of the Atlas
booster engine with extended nozzle would have the right thrust, but would
be about 18 feet wide at the nozzle exit, too large to fit on any
reasonably-sized upper stage.
It's more likely that the Isp would be around 330 seconds, and you'd be down
several thousand lbs of payload.
> 5. Absolutely, in fact, it can launch under worse conditions than the
> shuttle. Finite element analysis modeling shows that with the ker/lox
> upperstage, CG, or rather cm is in about the same place as the shuttle,
> and even under worse case wind conditions, etc, the steerable nozzle
> has more than enough control authority to handle it, and lots of margin
> to spare.
>
This is very sensible. The SRB has plenty of thrust to lift the heavier
upper stage.
> Some other points he made:
> 6. the reliability and safety of the SRB is extremely well known--thus
> the system reliability depends nearly entirely on the reliability of
> the second stage. For the 'best fit' notional model, he was using a
> Saturn V J2S, although it works with a J2. That would require
> re-developing the big ker/lox engine--big deal and much moolah, but it
> would probably be a popular project. Also, rocketdyne has kept much of
> the J2 knoweledge in working order, even using the turbopumps on the
> X-33 linear aerospikes. It could probably be done pretty quickly.
> 7. One of the first people outside-of-NASA people briefed in on this as
> a "reality check" was the then-head of APL, Mike Griffen. And he
> apparently was very impressed by its possibilities for success. So
> support inside NASA should not be a problem.
> 8. We should know if this is going forward within the next 2 months,
> because that's the time limit to complete a people carrying version by
> 2010. If a decision is not made by then, it's not going to happen. So
> standby...
>
> Tom Cuddihy
>
Murray Anderson
Ed Kyle
>
> I do have this crazy idea to see what happens if you stack
> a Delta IV core on top of a SRB, though...
Maybe 15 or so metric tons to LEO, assuming you use
the RS-68 somehow. At 26-27 tons empty, CBC is a bit
on the heavy side for an upper stage.
An S-IVB with a J-2 would be almost perfect. S-IVB
only weighed 10 tons (or a bit less) at burnout. I
get about 18 tons (about 40,000 lbs) to LEO with this
configuration. It's kind of strange how this works
out. You get a Saturn IB, basically, but without all
of the mad plumbing. It's as if the SRBs were
designed to provide the same total impulse as an S-IB
stage.
An RP/LOX second stage, fitted with a notional,
throttlable RS-27A would be able to orbit maybe
10 tons (22,000 lbs). Not too bad, and maybe
cheaper than an S-IVB type second stage, but
an Atlas V Medium could do the same for probably
less money.
To really cut costs, NASA should abandon the VAB and
stack its SRB-based single-stick launcher on a pad.
How about recently-vacated Pad 40?
- Ed Kyle
Tom Cuddihy
George William Herbert wrote:
> There has to have been some error there; the J-2s were LOX/LH2
> upper stage engines, not lox/kerosene as described elsewhere
> and partly here.
>
> J-2 isn't a bad choice, nor is LOX/LH2 for the upper stage,
> but clarification would have been nice.
That's my error,not his. We were doing quite a bit of different
possibility discussions and I'm not sure how I got that mixed up. His
notional case used a J2--yes, LOX/H2, and there was another one he had
analyzed that was ker/Lox. I got mixed up somewhere in there & didn't
look up which was which.
>
Scott Lowther
>scottlo...@ixDOT.netcomARGH.com wrote:
>
>
>>>Apparantly he left out the part where large segmented solids have
>>>
>>>
>>gone
>>"boom" in the past.
>>
>>That has never happened with the Shuttle motors in either flight or
>>groudn test.
>>
>>
>
>True, but "The shuttle RSRMs have never gone BOOM" is a much weaker
>statement than "solid rocket motors don't go BOOM." I seem to recall a
>Delta solid going BOOM and raining bits of GPS satellite all over a
>bunch of parked cars a few years back as well.
>
>
I recall lots of liquid boosters raining payload all over the landscape.
In fact, it's one of my current tasks... working on a historical summary
of launch vehicle reliability. A whole fo of rockets going BOOM for a
whole lot of reasons.
>Without hearing Horowitz's defense of the SRBs word-for-word it's hard
>to be specific, but claiming that "if there wasn't a fuel tank in the
>way, Challenger would still have probably made orbit, as most of the
>thrust was still going out the nozzle" strikes me as verging on
>dishonest.
>
It's true. The analyses showed that Challenger should have made orbit,
had the burn-though been outboard. Performance would have been affected,
and thrust vectoring systems on both the SRBs and the SSMEs would ahve
been nearly maxed out, but Challenger would ahve made orbit.
Scott Lowther
>George William Herbert wrote:
>
>
>>I do have this crazy idea to see what happens if you stack
>>a Delta IV core on top of a SRB, though...
>>
>>
>
>Maybe 15 or so metric tons to LEO, assuming you use
>the RS-68 somehow. At 26-27 tons empty, CBC is a bit
>on the heavy side for an upper stage.
>
>An S-IVB with a J-2 would be almost perfect.
>
Without getting into specifics, the upper stage planned pretty much *is*
an S-IVb except longer and narrower.
Murray Anderson
"Scott Lowther" <scottl...@ix.netcom.SPAMBLOK.com> wrote in message
news:Nwghe.1184$8g....@news01.roc.ny...
That assumes the leak didn't get any worse than postulated by the analysis.
I think that statistical analysis has shown that solid and liquid stages
have similar reliabilities, but since the liquids are easier to shut down
they have the advantage. They also have higher performance, so in the case
of the shuttle you wouldn't be driven to keep the performance of the upper
stage engine quite so high, or the eweight so low. You could also freeze the
weight of the external tank at original level and spend upgrade dollars on
stopping foam shedding.
Murray Anderson
john....@gmail.com
>
> "Scott Lowther" <scottl...@ix.netcom.SPAMBLOK.com> wrote in
> message news:Nwghe.1184$8g....@news01.roc.ny...
> >
> > made orbit, had the burn-though been outboard. Performance
> > would have been affected, and thrust vectoring systems on
> > both the SRBs and the SSMEs would ahve been nearly maxed out,
> > but Challenger would ahve made orbit.
>
> That assumes the leak didn't get any worse than postulated
> by the analysis.
That's correct, too many wrong and unwarranted assumptions -- from my
experience with the faulty launch preparations and from my FOIA
research perspective. Please glance at:
<www.mission51l.com/disaster.htm>
and
<www.mission51l.com/postx.htm>
What I see is an effort by Lockheed, Thiokol, and NASA to evade and
ignore the tandem-booster thrust imbalance which destroyed Challenger,
by simply leaving it as an exercise in disinformation for the public
relations people -- while moving on irresponsibly and unchecked to
single-solid 'lighter-weight CEV' contracts.
Challenger's Ghost
john....@gmail.com
john.max...@gmail.com wrote:
> Please glance at:
>
> <www.mission51l.com/disaster.htm>
> and
> <www.mission51l.com/postx.htm>
Sorry, that last link should be:
<www.mission51l.com/postX.htm>
> Challenger's Ghost
Scott Lowther
>
>I think that statistical analysis has shown that solid and liquid stages
>have similar reliabilities, but since the liquids are easier to shut down
>they have the advantage.
>
Solids and liquids in general, yes. But some specific stages are more or
less reliable than others. The Shuttle SRM is pretty damend reliable.
Ed Kyle
>
> An S-IVB with a J-2 would be almost perfect [as a
> second stage on top of an SRB]. S-IVB
> only weighed 10 tons (or a bit less) at burnout. I
> get about 18 tons (about 40,000 lbs) to LEO with this
> configuration. It's kind of strange how this works
> out. You get a Saturn IB, basically, but without all
> of the mad plumbing.
And with a recoverable first stage!
But I still have to wonder if an SRB-based launcher
of this type, which basically replicates the existing
capability of an EELV-Heavy, is worth pouring money
into. The U.S. government and a couple of U.S.
companies just spent billions developing EELV -
and together have had to eat a couple of billion
on the program.
Would SRB-based save money - and not just fly-away
costs but real money over the life of the program -
and not a speculative overly-optimistic high flight rate
assumed program but a real program? Would it be safer -
both for astronauts and for ground processing crews?
Would it be more reliable? Could it be used to
accomplish other missions too? Its backers have to
provide convincing "yes" answers to these questions in
order to win authorization.
- Ed Kyle
Ed Kyle
Three questions come to mind.
1) How much did it cost to develop S-IVB?
2) How much will it cost to develop this SRB upper stage?
3) To save money, could such a new stage also serve as an
EELV-Heavy upper stage, or as an upper stage for a new
shuttle-derived super heavy-lifter?
- Ed Kyle
Tom Cuddihy
> Three questions come to mind.
>
> 1) How much did it cost to develop S-IVB?
> 2) How much will it cost to develop this SRB upper stage?
I think the development would be significantly eased by the long
history of J2, and even the J2S test stand experience (from what I
understand, J2S had~30,000 hrs of run time on the stand), however,
obviously if Boeing or Lockheed is prime contractor, the costs WILL be
made such that EELV seems an attractive alternative.
> 3) To save money, could such a new stage also serve as an
> EELV-Heavy upper stage, or as an upper stage for a new
> shuttle-derived super heavy-lifter?
>
> - Ed Kyle
I think the way this is looked at by NASA administration is probably as
a 'temporary' solution to the flight-gap problem, but one that would
make the 'shuttle derived superlifter' much easier to force--making Sen
Bill Nelson and other 'standing army' advocates happy, but it will
probably see a lot of resistance from EELV and SFF types.
cuddihy
Tom Cuddihy
> Ed Kyle wrote:
> >
> > An S-IVB with a J-2 would be almost perfect [as a
> > second stage on top of an SRB]. S-IVB
> > only weighed 10 tons (or a bit less) at burnout. I
> > get about 18 tons (about 40,000 lbs) to LEO with this
> > configuration. It's kind of strange how this works
> > out. You get a Saturn IB, basically, but without all
> > of the mad plumbing.
Yeah, it has a weird beauty to it. In essence, the SRB is actually a
Big, Dumb Booster.
>
> And with a recoverable first stage!
>
> But I still have to wonder if an SRB-based launcher
> of this type, which basically replicates the existing
> capability of an EELV-Heavy, is worth pouring money
> into. The U.S. government and a couple of U.S.
> companies just spent billions developing EELV -
> and together have had to eat a couple of billion
> on the program.
True. However, when you put the competing requirements of manned safety
and proveable reliability together, it starts to become clear how NASA
could think this might be cheaper than man-rating a 35-40,000 lb-to-LEO
EELV. While the Medium EELVs look to have a respectable record to work
off of by the middle of this decade, Heavy versions, for both Atlas and
Delta, will have a much smaller history-->doubtful that Atlas V H will
ever even exist now that they are one combined launch effort. Delta
IVH's first launch wasn't exactly stellar, and it is clearly MUCH more
complex than the SRB-boosted concept. Man rating it could prove very
expensive.
You look at something like Soyuz, that has hardly changed since 1970,
and it looks like 'evolution rather than revolution' for manned
spaceflight ought to be the preferred path. Consider this scenario: the
first or second EELV CEV launch ends in a fireball. What happens to the
CEV program?
Add in the fact that SRB's history is long, well documented, and very
respectable, and already 'man-rated', and I see how NASA thinks it
could save money, and more important, probably, time--all while saving
existing jobs in Louisiana and at the Cape.
As to whether or not it would be efficient for other payloads--that's
an open question. How much of EELV cost growth is because of small
manifest and how much is because of inherent cost factors? The military
is going to stick with EELV until there is a viable alternative that
does not rely on the military alone for funding.
that's my cut.
-cuddihy
Tom Cuddihy
Ed Kyle wrote:
>
> But I still have to wonder if an SRB-based launcher
> of this type, which basically replicates the existing
> capability of an EELV-Heavy, is worth pouring money
I forgot to mention one othercost consideration for this:
The initial testing of the SRB-boosted J2, say with a dummy second
stage, could essentially be done for the cost of the dummy stage and
personnel, since NASA has several just-expired SRBs apparently sitting
around, unavailable for anything useful, since they're past the
expiration date.
That does seem like a bonus for the start of the program.
cuddihy
Murray Anderson
Man rating it would cost whatever Nasa wanted to spend. The concept of
man-rating is poorly defined. If it means that the acceleration is not too
high, then any Delta IV is man-rated. If it means that the stage can be shut
down in flight, then the SRB isn't man-rated. Obviously there are other
definitions. The man rating of the SRB on the Shuttle means that it has been
used for over 20 years to launch people, and that the efforts to make it
reliable have been reasonably successful (except once).
> You look at something like Soyuz, that has hardly changed since 1970,
> and it looks like 'evolution rather than revolution' for manned
> spaceflight ought to be the preferred path. Consider this scenario: the
> first or second EELV CEV launch ends in a fireball. What happens to the
> CEV program?
>
> Add in the fact that SRB's history is long, well documented, and very
> respectable, and already 'man-rated', and I see how NASA thinks it
> could save money, and more important, probably, time--all while saving
> existing jobs in Louisiana and at the Cape.
>
If saving jobs is the issue then saving money isn't.
> As to whether or not it would be efficient for other payloads--that's
> an open question. How much of EELV cost growth is because of small
> manifest and how much is because of inherent cost factors? The military
> is going to stick with EELV until there is a viable alternative that
> does not rely on the military alone for funding.
>
> that's my cut.
>
> -cuddihy
>
The SRB-based launch vehicle would require an upper (third) stage to deliver
satellites to GTO. Something else to develop.
Murray Anderson
Henry Spencer
Scott Lowther <"scottlowtherAT ix DOT netcom DOT com"> wrote:
>It's true. The analyses showed that Challenger should have made orbit,
However, as far as Challenger goes that is pretty hypothetical, since
added stresses from the ET attach hardware were almost certainly a factor
in the joint leak -- that is, there was a *reason* why the burn-through
was inboard.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert | he...@spsystems.net
Damon Hill
@g49g2000cwa.googlegroups.com:
> I think the development would be significantly eased by the long
> history of J2, and even the J2S test stand experience (from what I
> understand, J2S had~30,000 hrs of run time on the stand), however,
Over THREE YEARS of run time?! Perhaps you meant seconds?
--Damon
Ed Kyle
> Ed Kyle wrote:
>
> > Three questions come to mind.
> >
> > 1) How much did it cost to develop S-IVB?
> > 2) How much will it cost to develop this SRB upper stage?
>
> I think the development would be significantly eased by the long
> history of J2, and even the J2S test stand experience (from what I
> understand, J2S had~30,000 hrs of run time on the stand), however,
> obviously if Boeing or Lockheed is prime contractor, the costs WILL
be
> made such that EELV seems an attractive alternative.
According to this snippit:
"http://history.nasa.gov/SP-4206/app-a.htm"
it cost MFSC $16 million in late 1960s dollars
just for the production of each S-IVB stage for
Saturn IB. That's something like $80-100 million
in today's dollars, depending on which year you
assume the table's dollars are presented in. A
similar stage would be required for an SRB-based
booster. Note that this does not include the
development costs, which would run in the hundreds
of millions at least.
Based on this, it looks like each SRB-based rocket
would cost NASA something in the $200 million plus
range - roughly the same as an EELV-Heavy. It
would also cost hundreds of millions, maybe more
than a billion, to develop - money that would not
need to be spent on EELV. NASA would have to spend
some development funds to adapt EELV to CEV, but
the amount would surely be less than the cost of
developing an SRB launcher.
- Ed Kyle
Andrew Gray
> According to this snippit:
> "http://history.nasa.gov/SP-4206/app-a.htm"
> it cost MFSC $16 million in late 1960s dollars
> just for the production of each S-IVB stage for
> Saturn IB. That's something like $80-100 million
> in today's dollars, depending on which year you
> assume the table's dollars are presented in. A
There's something a bit odd about those figures - they have "Engines"
listed seperately, which would seem to suggest the $16m is too low. On
the other hand, the Saturn IB's S-IVB cost substantially less than the
Saturn V's. Oddness.
--
-Andrew Gray
andre...@dunelm.org.uk
Henry Spencer
Murray Anderson <mur...@k1ngst0n.net> wrote:
>...The man rating of the SRB on the Shuttle means that it has been
>used for over 20 years to launch people, and that the efforts to make it
>reliable have been reasonably successful (except once).
Don't forget that the shuttle is *not* man-rated by NASA's current rules.
Henry Spencer
Tom Cuddihy <tom.c...@gmail.com> wrote:
>Yeah, it has a weird beauty to it. In essence, the SRB is actually a
>Big, Dumb Booster.
Uh, no, not hardly. The concept of the Big Dumb Booster is to make the
rocket bigger, and use the gains from size to permit extremely simple
construction and wide margins. The SRB is the most complex solid rocket
ever built, an elaborate and manpower-intensive design with quite thin
margins. It may be dumb by MSFC standards, but not by anyone else's.
>...I see how NASA thinks it
>could save money, and more important, probably, time--all while saving
>existing jobs in Louisiana and at the Cape.
Yep, can't forget those jobs. Lots and lots of jobs. Don't forget all
the guys at MSFC that will be working on that upper stage, and on systems
engineering for the combination, and on man-rating, and and and... (What
was that about low cost again?)
After all, we can't rely on those (ugh) capitalists to supply us with
launches. We need a *government* solution! The glory of spaceflight must
not be tarnished by buying commercial launches for our socialist hero
astronauts.
Um, what's that you say? NASA is *legally* *required* to buy commercial
launch services whenever possible? Oh, never mind that. What are a few
laws, when so many jobs at MSFC are at stake?
>As to whether or not it would be efficient for other payloads--that's
>an open question. How much of EELV cost growth is because of small
>manifest and how much is because of inherent cost factors?
Almost all the former. Those boosters are probably actually simpler than
the shuttle SRBs.
By the way, don't forget that NASA is forbidden by law to compete with
commercial launch suppliers.
>The military
>is going to stick with EELV until there is a viable alternative that
>does not rely on the military alone for funding.
The idea that the military will sign up as customers for another NASA-run
launch service is laughable. They made that mistake once, and won't make
it again.
Scott Lowther
>Ed Kyle wrote:
>
>
>
>>But I still have to wonder if an SRB-based launcher
>>of this type, which basically replicates the existing
>>capability of an EELV-Heavy, is worth pouring money
>>
>>
>
>I forgot to mention one othercost consideration for this:
>
>The initial testing of the SRB-boosted J2, say with a dummy second
>stage, could essentially be done for the cost of the dummy stage and
>personnel, since NASA has several just-expired SRBs apparently sitting
>around, unavailable for anything useful, since they're past the
>expiration date.
>
Don't remind me. My first historically notable task at ATK was to be
pre-flight prediction and post-test reconstruction of the RSRM-90 flight
set, for STS-114. But since (as it now appears) the RSRM-90 flight set
is being pulled from STS-114, and RSRM-92 put in it's place, the
schedule of who does what's all messed up. It's a little unclear jsut
what will happen to the RSRM-90 flight set... might be installed on a
future launch or, since they are nearing the end of shelf life, static
tested.
My suggestion was to install simple capsules on the noses of each, stack
'em both on the pad, have some rich maniacs pay good money to ride in
the capsules, and launch simultaneously and see which one gets to
100,000 feet first. My boss liked the idea, but said the chances of that
were pretty slim...
Murray Anderson
"Henry Spencer" <he...@spsystems.net> wrote in message
news:IGIBr...@spsystems.net...
Are these just prospective rules for the CEV, or are they intended to be
generally applicable?
I recall reading some specifications several months ago and they looked like
a laundry list intended to satisfy multiple constituencies. For example, the
flight controllers had to have override options on abort, as well as the
flight crew and the spec didn't define priorities.
Anyway, they defined a process for giving waivers that would let through the
shuttle - it was all a matter of going through the proper channels.
Murray Anderson
Henry Spencer
Murray Anderson <mur...@k1ngst0n.net> wrote:
>> Don't forget that the shuttle is *not* man-rated by NASA's current rules.
>
>generally applicable?
They're intended to be generally applicable... for future vehicles. The
existing ones, Soyuz and Shuttle, are grandfathered in rather than being
subject to the new rules.
>Anyway, they defined a process for giving waivers that would let through the
>shuttle - it was all a matter of going through the proper channels.
Yes, but such waivers exempt (say) the shuttle from compliance, rather
than declaring that it complies despite appearing not to.
Henry Spencer
Tom Cuddihy <tom.c...@gmail.com> wrote:
>What they determined from an overall perspective (much like the SpaceX
>Futron study) is that maximizing reliability on larger systems means
>means best reliability comes with 1 first stage engine, 1 separation
>event, and 1 second stage engine.
The key question to ask when presented with such a result is "what were
the underlying assumptions?".
In this case, the assumptions probably include "expendable vehicle" and
"no fault tolerance". The former means that the flight article cannot be
flight-tested before operational use. The latter means that any failure
is fatal. *With those assumptions*, the conclusion might be correct.
Change those assumptions, and the results change. Vehicles that can
tolerate failures are much more reliable than those which can't; this is
why airliners have multiple engines, multiple hydraulic systems, etc.
Four Saturns (two Is and two Vs) made it to orbit despite engine failures;
that rarely happens with single-engine-per-stage launchers.
>The problem is that no liquid engines currently exist that are powerful
>enough to (with one engine) thrust the first stage of a manned capsule
>off the pad.
A very curious assertion. The Delta IVM -- that's one core with no
strap-ons, i.e. one engine firing at liftoff -- can put 8.5t into the ISS
orbit. That's enough for two complete Gemini spacecraft, probably enough
for a single Apollo CM with a small LEO-only SM (as was originally
proposed for what became Skylab), enough with substantial margins for
BAe's four-man MRC design, and enough with large margins for a Soyuz or
for Venturer Aerospace's current capsule designs.
Clearly we have another assumption hiding here: a "manned capsule" must
be much larger and more massive than all previous capsule concepts.
Also, as other people have pointed out, either "liquid engines" are
limited to US designs, or designs like the RD-171 are being classed as
clusters rather than single engines. Zenit -- which lifts off on a single
RD-171 -- was meant to replace the Semyorka launcher series, including
taking over Soviet manned launches.
>1. Didn't an SRB failure cause the Challenger accident?
>1. Yes, but the explosion happened because hot gas burned through the
>LOX/H2 tank. Solid rockets don't explode...
Ho ho. Tell that to the people who were at the first Titan IVB SRB test.
richard schumacher
he...@spsystems.net (Henry Spencer) wrote:
> >What they determined from an overall perspective (much like the SpaceX
> >Futron study) is that maximizing reliability on larger systems means
> >minimizing component integration complexities... That
> >means best reliability comes with 1 first stage engine, 1 separation
> >event, and 1 second stage engine.
>
> The key question to ask when presented with such a result is "what were
> the underlying assumptions?".
>
> In this case, the assumptions probably include "expendable vehicle" and
> "no fault tolerance". The former means that the flight article cannot be
> flight-tested before operational use. The latter means that any failure
> is fatal. *With those assumptions*, the conclusion might be correct.
>
> Change those assumptions, and the results change. Vehicles that can
> tolerate failures are much more reliable than those which can't; this is
> why airliners have multiple engines, multiple hydraulic systems, etc.
> Four Saturns (two Is and two Vs) made it to orbit despite engine failures;
> that rarely happens with single-engine-per-stage launchers.
It is astonishing that people keep forgetting or mis-understanding these
basic points. Is this innumeracy at work, or some sort of design
prejudice?
Murray Anderson
> In article <1116009407.5...@o13g2000cwo.googlegroups.com>,
> Tom Cuddihy <tom.c...@gmail.com> wrote:
> >What they determined from an overall perspective (much like the SpaceX
> >Futron study) is that maximizing reliability on larger systems means
> >minimizing component integration complexities... That
> >means best reliability comes with 1 first stage engine, 1 separation
> >event, and 1 second stage engine.
>
> The key question to ask when presented with such a result is "what were
> the underlying assumptions?".
>
II has a very good record of reliability, something like 98%. Most of its
flights have been with the 9 solids, 6 ignited at liftoff and 3 in the air,
then there's the core liquid stage and the upper stage, then sometimes a
solid on top of that. Who'd think it was the most reliable expendable?
Take the transition from the ICBM-based Atlas to Atlas II, with failures
going way down, even though many Atlas IIs had SRB's. This wasn't due to
reduction in number of engines. The engines had thrust increased and the
structural weight proportion of the first stage was increased.
Take the Soyuz, with something like 97% relibility, and it has 5 engines
ignited at liftoff, or 20 if you count chambers, plus verniers.
The Proton rocket is only moderately reliable, and that may owe something to
the large number of stages, but the stage failure rates don't follow the
number of engines. The failures for the first three stages are 4, 8, 3
respectively in 290 flights since 1970, and the number of engines are 6, 4,
2 respectively, . The various versions of the Block D (1 engine) failed 8
times in 271 flights.
> In this case, the assumptions probably include "expendable vehicle" and
> "no fault tolerance". The former means that the flight article cannot be
> flight-tested before operational use. The latter means that any failure
> is fatal. *With those assumptions*, the conclusion might be correct.
>
> Change those assumptions, and the results change. Vehicles that can
> tolerate failures are much more reliable than those which can't; this is
> why airliners have multiple engines, multiple hydraulic systems, etc.
> Four Saturns (two Is and two Vs) made it to orbit despite engine failures;
> that rarely happens with single-engine-per-stage launchers.
>
The space shuttle, with 99% launch reliability does lend some support to the
stage/engine theory, having only 5 engines lit at takeoff and 3 on the upper
stage. It also lends support to your theory about redundancy since there's
that 1985 flight that made orbit on 2 engines.
The number of stages must be a limiting factor on reliability, as must the
number of engines, unless you have redundancy, but they don't seem to be the
dominant factors on current launch vehicles.
Murray Anderson
Tom Cuddihy
seconds, yes. I should not type after beer.
Tom Cuddihy
> >Yeah, it has a weird beauty to it. In essence, the SRB is actually a
> >Big, Dumb Booster.
>
> Uh, no, not hardly. The concept of the Big Dumb Booster is to make
the
> rocket bigger, and use the gains from size to permit extremely simple
> construction and wide margins. The SRB is the most complex solid
rocket
> ever built, an elaborate and manpower-intensive design with quite
thin
> margins. It may be dumb by MSFC standards, but not by anyone else's.
It's all relative, then isn't it? The Big Dumb Idea is that the
development and manufacture of the SRBs are well understood and have an
established track record. It has a mass fraction of 84%. And it has a
Big Dumb amount of thrust. While it might not fit the "Space Access
'99" White Paper definition of Big Dumb booster or whatever you're
referring to, it provides a large, massive amount of thrust that would
be cheaper and more reliable to come by than developing a huge first
liquid first stage that, by the way, if you haven't noticed, NOONE is
offering to develop commercially anyway.
>
> After all, we can't rely on those (ugh) capitalists to supply us with
> launches. We need a *government* solution! The glory of spaceflight
must
> not be tarnished by buying commercial launches for our socialist hero
> astronauts.
As unfortunately has to be said every week in this forum, NASA will
stop launching its own manned rockets when somebody else starts doing
it. Last I heard, nobody's offering. (Unless you're referring to
several groups that have plans--and just need a billion or so of your
investment to get started...)
And any solution that doesn't consider the political ramifications is
likely to get a rude awakening from congress without
administration-level intervention. Thus far the white house has shown
no preference for outside-of government solutiuons. GWB's mode of
operation is not exactly anti-big government.
>
> Um, what's that you say? NASA is *legally* *required* to buy
commercial
> launch services whenever possible? Oh, never mind that. What are a
few
> laws, when so many jobs at MSFC are at stake?
Hey, I'm not saying the way the government does business is efficient,
or that I favor a government solution over a commercial one. By far, I
would prefer to see the CEV launched on a Falcon X, wouldn't you?
However, since we both know there won't be a CEV capable American
commercial rocket (unless it's EELV) in 2010, a NASA solution is
acceptable.
The Columbia INvestigation report mandated that the next NASA launch
vehicle should have asstronaut safety during launch as a prime
consideration, something a three-core rocket like Delta Iv, with its
already glowing record, is unlikely to provide.
> The idea that the military will sign up as customers for another
NASA-run
> launch service is laughable. They made that mistake once, and won't
make
> it again.
Agree. As stated, the military will minimize risk by sticking with EELV
until an actual competitor with a working launcher appears. My money's
on SpaceX, 2015 timeframe.
cuddihy
Tom Cuddihy
>
> My suggestion was to install simple capsules on the noses of each,
stack
> 'em both on the pad, have some rich maniacs pay good money to ride in
> the capsules, and launch simultaneously and see which one gets to
> 100,000 feet first. My boss liked the idea, but said the chances of
that
> were pretty slim...
My idea is to make it a 'survivor' like show, with all the participants
being culled from various media outlets, with viewers calling in and
voting down participants until one lucky journalist gets a ride to
mach 17 and 18 gees...
cuddihy
Tom Cuddihy
Henry Spencer wrote:
> In article <1116009407.5...@o13g2000cwo.googlegroups.com>,
> Tom Cuddihy <tom.c...@gmail.com> wrote:
> >What they determined from an overall perspective (much like the
SpaceX
> >Futron study) is that maximizing reliability on larger systems means
> >minimizing component integration complexities... That
> >means best reliability comes with 1 first stage engine, 1 separation
> >event, and 1 second stage engine.
>
> The key question to ask when presented with such a result is "what
were
> the underlying assumptions?".
>
> In this case, the assumptions probably include "expendable vehicle"
and
> "no fault tolerance". The former means that the flight article
cannot be
> flight-tested before operational use. The latter means that any
failure
> is fatal. *With those assumptions*, the conclusion might be correct.
He didn't say. It sounds like a good assumption, though, considering
the post-Columbia atmosphere.
> Clearly we have another assumption hiding here: a "manned capsule"
must
> be much larger and more massive than all previous capsule concepts.
It's not exactly 'hiding,'Henry. In order to meet the VSE intent, the
next NASA space vehicle has to be, if not already able to complete a
long-term lunar mission, at least be modifiable to meet that objective.
Clearly a smaller Soyuz-sized, or worse, Gemini-sized vehicle, while
meeting the words, does NOT meet the intent. A stopgap like that also
provides an easy congressional offramp after the ISS is taken care of.
> Also, as other people have pointed out, either "liquid engines" are
> limited to US designs,
Somehow I doubt NASA considered Russian rocket engines in its analyses.
or designs like the RD-171 are being classed as
> clusters rather than single engines. Zenit -- which lifts off on a
single
> RD-171 -- was meant to replace the Semyorka launcher series,
including
> taking over Soviet manned launches.
>
> >1. Didn't an SRB failure cause the Challenger accident?
> >1. Yes, but the explosion happened because hot gas burned through
the
> >LOX/H2 tank. Solid rockets don't explode...
Golly, he left that example out. still, it sounds like the SRB is
pretty solid. (now isn't that punny?)
cuddihy
Jorge R. Frank
> The Columbia INvestigation report mandated that the next NASA launch
> vehicle should have asstronaut safety during launch as a prime
> consideration, something a three-core rocket like Delta Iv, with its
> already glowing record, is unlikely to provide.
They didn't "mandate" it. They didn't even "recommend" it... all they made
was an "observation", and even that was a lot less specific than you
phrased it:
O10.2-1 Future crewed-vehicle requirements should incorporate the knowledge
gained from the Challenger and Columbia accidents in assessing the
feasibility of vehicles that could ensure crew survival even if the vehicle
is destroyed.
(There *were* recommendations in the report that were closer to your
wording... but read carefully: they were actually recommendations from
earlier NASA Aerospace Safety Advisory Panel reports that were *quoted* in
the CAIB report, but which the CAIB itself chose not to endorse in their
own recommendations. The key is placement and numbering: if it's not listed
in CAIB chapter 11, or doesn't have an "R" in front of it, it's *not* a
CAIB recommendation.)
--
JRF
Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.
Tom Cuddihy
> It is astonishing that people keep forgetting or mis-understanding
these
> basic points. Is this innumeracy at work, or some sort of design
> prejudice?
Design prejudice, I would say. Rather than analyzing all possibilities,
clearly these fools limited their scope to available technologies that
would fit within the NASA budget. (As opposed to, say, a new reusable
Shuttle II or a new Saturn V development.)
cuddihy
George William Herbert
>Henry Spencer wrote:
>[...]
>> Clearly we have another assumption hiding here: a "manned capsule"
>> must be much larger and more massive than all previous capsule concepts.
>
>It's not exactly 'hiding,'Henry. In order to meet the VSE intent, the
>next NASA space vehicle has to be, if not already able to complete a
>long-term lunar mission, at least be modifiable to meet that objective.
>Clearly a smaller Soyuz-sized, or worse, Gemini-sized vehicle, while
>meeting the words, does NOT meet the intent. A stopgap like that also
>provides an easy congressional offramp after the ISS is taken care of.
Soyuz models were intended for Lunar missions; stacked with...
Oh, I don't know, a slightly cut down Salyut it could stay in
orbit around the Moon for a long, long time, and you could just about
throw one of those to low lunar orbit with orbital assembly of
three Proton sized payloads, to rough back of the envelope guess.
So apparently the Soviet Union could meet the CEV requirements
with a Soyuz sized capsule, in 1972 or so.
We are having mission conflict here; the ISS mission is a lot simpler
than the lunar one.
In that sense, it would have made more sense to have two vehicles
designed and built. Except that the timing on all of this, with
O'Keefe's departure and what parts of NASA report to whom and
Steidle's scope as defined at the time, and Columbia's loss,
all turned out rather badly.
It may turn out that the missions get functionally separated some
more than they are right now. Where we are on the two divergent
mission models (LEO access for people, and deep space/planetary/
lunar manned activities) is fairly clear to a lot of people.
But, with new administrator, with his own opinions and biases
and experience, I don't think anyone outside his immediate inner
circle knows what direction the wind is likely to blow.
Who knows. Perhaps someone *cough* will be selling rides
to ISS for reasonable prices on an all US vehicle before the
2010 deadline with no NASA R&D money, making the CEV mission
more clearly deep space oriented.
-george william herbert
gher...@retro.com / gher...@venturerspace.com
Ed Kyle
>
> The Columbia INvestigation report mandated that the next NASA launch
> vehicle should have asstronaut safety during launch as a prime
> consideration, something a three-core rocket like Delta Iv, with its
> already glowing record, is unlikely to provide.
The first Delta IV Heavy suffered an anomaly during
its first demonstration flight that could have
provided survivable abort modes for astronauts. No
Delta IV or Atlas V flights have suffered catastrophic
failures to date. Crew escape systems could be designed
for the EELVs that could provide a much wider escape
coverage than the existing NASA crewed launch system -
which doesn't protect astronauts from catastrophic
failures during the critical first two minutes of
flight - including Max-Q when many failures occur.
Delta IV and Atlas V were designed to meet a 98%
reliability goal - which just so happens to be the
demonstrated reliability of NASA's current crewed
launch system (and, roughly, Russia's Soyuz launch
system, etc.).
No rocket is immune to failure. None. Rockets with
people on top of them *will* fail catastrophically
again some day - whether they be EELV or SRB-based.
Big solid rocket boosters offer the additional hazard
of inadvertant ignition during prelaunch preparations
when lots of people are nearby, as happened in Brazil
and India.
- Ed Kyle
lex...@ix.netcom.com
According to this snippit:
"http://history.nasa.gov/SP-4206/app-a.htm"
it cost MFSC $16 million in late 1960s dollars
just for the production of each S-IVB stage for
Saturn IB. That's something like $80-100 million
in today's dollars, depending on which year you
assume the table's dollars are presented in. A
similar stage would be required for an SRB-based
booster.
Well, an equivalent stage woudl likely be required for EELV options as
well. If the new lunar vehicles winds up with a mass roughly like that
of the Apollo CSM/LEM, then it'll take something akin to an S-IVb to
throw it from LEO to the moon. So if an S-IVb equivalent is designed as
an upper stage for the ATK CEV launcher, that upper stage would also be
available for deep-space launch (probably by putting it on a Shuttle
C/Magnum SDV).
So the ATK option is two stages... one being a modified version of the
existing RSRM, the other being a stage that would need development
anyway.
Henry Spencer
Murray Anderson <mur...@k1ngst0n.net> wrote:
>The first thing to do is to test the theory, at least informally. The Delta
>II has a very good record of reliability, something like 98%. Most of its
>flights have been with the 9 solids, 6 ignited at liftoff and 3 in the air,
>then there's the core liquid stage and the upper stage, then sometimes a
>solid on top of that. Who'd think it was the most reliable expendable?
Well, careful here. There is a strong element of random chance in this,
since the statistics are based on quite small numbers of failures (some of
them due to external factors rather than hardware failures) -- it would
only take one or two extra failures to make Delta II's record look
considerably worse.
Henry Spencer
>Four Saturns (two Is and two Vs) made it to orbit despite engine failures;
>that rarely happens with single-engine-per-stage launchers.
Small correction: the first of the Saturn Is in question was suborbital
(and the "failure" was actually a deliberate test), but the bottom line
was the same -- success despite an engine out.
Rand Simberg
<tom.c...@gmail.com> made the phosphor on my monitor glow in such a
way as to indicate that:
>I've heard all this before, and I had some preconceived skepticisms,
>among them:
>1. Didn't an SRB failure cause the Challenger accident?
>2. Don't SRB's cost alot?
>3. Isn't that too much thrust to handle for a small vehicle?
>4. thus Wouldn't extensive modifications to the burn profile be
>required, costing even more?
>5. Does the steerable nozzle have enough control authority?
>
>Scott Horowitz was pretty convincing that these are not legitimate
>concerns, for the following reasons:
>1. Yes, but the explosion happened because hot gas burned through the
>LOX/H2 tank. Solid rockets don't explode.
The people at the rocket lab, who lost half a mountain to a Titan
booster test failure, will be surprised to hear this.
>5. Absolutely, in fact, it can launch under worse conditions than the
>shuttle. Finite element analysis modeling shows that with the ker/lox
>upperstage, CG, or rather cm is in about the same place as the shuttle,
>and even under worse case wind conditions, etc, the steerable nozzle
>has more than enough control authority to handle it, and lots of margin
>to spare.
How about roll control?
Rand Simberg
<edky...@hotmail.com> made the phosphor on my monitor glow in such a
way as to indicate that:
>Would SRB-based save money - and not just fly-away
>costs but real money over the life of the program -
>and not a speculative overly-optimistic high flight rate
>assumed program but a real program? Would it be safer -
>both for astronauts and for ground processing crews?
>Would it be more reliable? Could it be used to
>accomplish other missions too? Its backers have to
>provide convincing "yes" answers to these questions in
>order to win authorization.
Sadly, that's not necessarily the case. If history is any guide, it
may be sufficient for its backers to simply demonstrate relative job
losses in certain congressional districts.
Rand Simberg
<tom.c...@gmail.com> made the phosphor on my monitor glow in such a
way as to indicate that:
>> After all, we can't rely on those (ugh) capitalists to supply us with
>> launches. We need a *government* solution! The glory of spaceflight
>must
>> not be tarnished by buying commercial launches for our socialist hero
>> astronauts.
>
>As unfortunately has to be said every week in this forum, NASA will
>stop launching its own manned rockets when somebody else starts doing
>it.
Why should we believe that it will happen then?
>And any solution that doesn't consider the political ramifications is
>likely to get a rude awakening from congress without
>administration-level intervention. Thus far the white house has shown
>no preference for outside-of government solutiuons. GWB's mode of
>operation is not exactly anti-big government.
Sadly true.
Henry Spencer
Tom Cuddihy <tom.c...@gmail.com> wrote:
>> ...another assumption hiding here: a "manned capsule" must
>> be much larger and more massive than all previous capsule concepts.
>
>It's not exactly 'hiding,'Henry. In order to meet the VSE intent, the
>next NASA space vehicle has to be, if not already able to complete a
>long-term lunar mission, at least be modifiable to meet that objective.
As was Gemini -- there were a number of proposals for doing lunar missions
with it, up to and including lunar landings. Soyuz was designed to be
used for lunar missions as well as LEO ones. And note that one of the
examples I cited was an Apollo CM; swapping service modules, from a small
LEO-only one to a deep-space one with bigger tanks, strikes me as a rather
small modification.
>Clearly a smaller Soyuz-sized, or worse, Gemini-sized vehicle, while
>meeting the words, does NOT meet the intent.
Why not? And given that there's enough payload on a Delta IVM for *two*
Geminis, there is clearly room to build something a little larger... The
BAe MRC proposal was quite sizable -- bigger than Apollo -- with the bonus
of being (by intent, at least) almost fully reusable, although it would
surely need a thicker heatshield and an expendable propulsion module for a
lunar mission.
>> Also, as other people have pointed out, either "liquid engines" are
>> limited to US designs...
>
>Somehow I doubt NASA considered Russian rocket engines in its analyses.
This wasn't a NASA analysis (although the people who did it are undoubtedly
hoping to sell NASA on their conclusions).
Tom Cuddihy
> >Scott Horowitz was pretty convincing that these are not legitimate
> >concerns, for the following reasons:
> >1. Yes, but the explosion happened because hot gas burned through
the
> >LOX/H2 tank. Solid rockets don't explode.
>
> The people at the rocket lab, who lost half a mountain to a Titan
> booster test failure, will be surprised to hear this.
>
several people have mentioned that--we didn't discuss it, none of us
students knew enough to ask about it, but supposedly this kind of
explosive situation has never happened in 240 SRB flights.
> >5. Absolutely, in fact, it can launch under worse conditions than
the
> >shuttle. Finite element analysis modeling shows that with the
ker/lox
> >upperstage, CG, or rather cm is in about the same place as the
shuttle,
> >and even under worse case wind conditions, etc, the steerable nozzle
> >has more than enough control authority to handle it, and lots of
margin
> >to spare.
>
> How about roll control?
I didn't think to ask about it. Is there any reason it would be
different than pitch and yaw control? From what we discussed the SRB
has a steerable nozzle capable of about 8 deg deflection (on the
limiting end), with the max expected deflection (derived from F.E.M. of
the paper 'J-2' stacked ATK rocket)about 1-1.5 deg. We didn't discuss
the specific rates, but Mr. Horowitz said it had been initially
analyzed as being well within the capability of the current SRB
actuators.
How does the shuttle handle roll control? Is it handled by the orbiter
itself or the combined stack? I'm past the limits of my knowledge here.
Tom Merkle
Earl Colby Pottinger
> > >LOX/H2 tank. Solid rockets don't explode...
>
> Golly, he left that example out. still, it sounds like the SRB is
> pretty solid. (now isn't that punny?)
That has not been the only solid to blow up, just tne one that you sure
everyone will know of once they are reminded.
Earl Colby Pottinger
--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp
Earl Colby Pottinger
Budget? What does budget have to do with it? As Henry already pointed a
small capsule could be launched on present day boosters. Are you saying it
is cheaper to design and build a large capsule and a new booster for it than
just a small capsule.
NASA's management choose certain base assumations for two reasons:
1) Because it is what they did before (but they have done small capsules).
2) It keeps thier little empire/pork-barrel rolling. When NASA choose a
design that requires them to layoff more that 80% of thier maintenance staff
then we will see savings.
Tom Cuddihy
Henry Spencer wrote:
> In article <1116218139.0...@g49g2000cwa.googlegroups.com>,
> Tom Cuddihy <tom.c...@gmail.com> wrote:
> >> ...another assumption hiding here: a "manned capsule" must
> >> be much larger and more massive than all previous capsule
concepts.
> >
> >It's not exactly 'hiding,'Henry. In order to meet the VSE intent,
the
> >next NASA space vehicle has to be, if not already able to complete a
> >long-term lunar mission, at least be modifiable to meet that
objective.
>
> As was Gemini -- there were a number of proposals for doing lunar
missions
> with it, up to and including lunar landings. Soyuz was designed to
be
> used for lunar missions as well as LEO ones. And note that one of
the
> examples I cited was an Apollo CM; swapping service modules, from a
small
> LEO-only one to a deep-space one with bigger tanks, strikes me as a
rather
> small modification.
That's possible, I guess I myself have a preconceived notion that CEV
is supposed to maintain most long-duration capabilities within the
capsule itself, and obviously that's the assumption the spaceflight
office was departing from when they came up with a "greater than 30,000
lbs to LEO" capsule. Even doubling the Gemini capacity to 4 astronauts,
while it would not double the weight, would mandate some sort of
roomier module (inflatable? add-on CM portion of the capsule itself?).
I see now what you're getting at about a 'hidden' assumption--after
all, the CEV requirements don't mention anything about the astronaut
return method actually having the duration capability onboard--that
just seemed like common-sense to me, but I see there are ways to
reasonably separate the capabilities without going to the extremes of
'2 launches for a single LEO mission', which would be pretty silly.
> >Clearly a smaller Soyuz-sized, or worse, Gemini-sized vehicle, while
> >meeting the words, does NOT meet the intent.
>
> Why not? And given that there's enough payload on a Delta IVM for
*two*
> Geminis, there is clearly room to build something a little larger...
The
> BAe MRC proposal was quite sizable -- bigger than Apollo -- with the
bonus
> of being (by intent, at least) almost fully reusable, although it
would
> surely need a thicker heatshield and an expendable propulsion module
for a
> lunar mission.
>
I would think the thicker heatshield is non-modular--I assume it would
be designed even into the very first LEO-only versions. The propulsion
module, on the other hand, seems very negotiable, and could be launched
on a cargo-only EELV or a large enough single launcher, which
ATK-boosted J2 sounds capable of.
> >> Also, as other people have pointed out, either "liquid engines"
are
> >> limited to US designs...
> >
> >Somehow I doubt NASA considered Russian rocket engines in its
analyses.
>
> This wasn't a NASA analysis (although the people who did it are
undoubtedly
> hoping to sell NASA on their conclusions).
Perhaps I misunderstood Scott Horowitz, but my impression was that this
was an internal analysis done at JSC before ATK got involved...
cuddihy
Rand Simberg
>> How about roll control?
>
>I didn't think to ask about it. Is there any reason it would be
>different than pitch and yaw control?
Yes. The Shuttle gets roll control (partly) by gimballing the nozzles
on the SRBs, which are offset from the vehicle CG. An SRB only has no
intrinsic roll control, because gimbaling the nozzle only controlls
pitch and yaw, and can't exert a torque about the longitudinal axis.
Such a vehicle would require either thrusters, or vanes on fins or in
the exhaust to provide such torque, or rely on a roll-control system
in the upper stages.
john....@gmail.com
It's certainly refreshing to see *anyone* who posts to the sci.space
groups admit this. Jon Berndt, take notice!
Challenger's Ghost
Scott Lowther
>Such a vehicle would require either thrusters,
>
Bingo.
Rand Simberg
john....@gmail.com made the phosphor on my monitor glow in such a
way as to indicate that:
>Rand Simberg wrote:
>> On 16 May 2005 12:57:37 -0700, in a place far, far away,
>> "Tom Cuddihy" <tom.c...@gmail.com> made the phosphor
>> on my monitor glow in such a way as to indicate that:
>>
>> >> How about roll control?
>> >
>> >I didn't think to ask about it. Is there any reason it
>> >would be different than pitch and yaw control?
>>
>> Yes. The Shuttle gets roll control (partly) by gimballing
>> the nozzles on the SRBs, which are offset from the vehicle CG.
>> An SRB only has no intrinsic roll control, because gimbaling
>> the nozzle only controlls pitch and yaw, and can't exert a
>> torque about the longitudinal axis. Such a vehicle would require
>> either thrusters, or vanes on fins or in the exhaust to provide
>> such torque, or rely on a roll-control system in the upper
>> stages.
>
>It's certainly refreshing to see *anyone* who posts to the sci.space
>groups admit this. Jon Berndt, take notice!
There's nothing to "admit" here with regards to your nutty theories,
Maxson.
Rand Simberg
Lowther <scottl...@ix.netcom.SPAMBLOK.com> made the phosphor on my
monitor glow in such a way as to indicate that:
>Rand Simberg wrote:
>
>>Such a vehicle would require either thrusters,
>>
>
>Bingo.
"Bingo" what? If that's the answer, expand on it, or Herb (and other
anal retentives) will accuse you not only of "one liners," but "one
worders."
Henry Spencer
scottlo...@ixDOT.netcomARGH.com <lex...@ix.netcom.com> wrote:
>>"http://history.nasa.gov/SP-420=AD6/app-a.htm"
>>it cost MFSC $16 million in late 1960s dollars
>
>Well, an equivalent stage woudl likely be required for EELV options as
>well. If the new lunar vehicles winds up with a mass roughly like that
>of the Apollo CSM/LEM, then it'll take something akin to an S-IVb to
>throw it from LEO to the moon.
However, a pure TLI stage would differ considerably from one that also had
to double as the second stage of an orbital launcher. (The S-IVB suffered
from this too, being optimal for neither role.)
In particular, you probably would *not* use a J-2 or straightforward J-2
derivative for a pure TLI stage. The J-2's Isp is not really very good
for a LOX/LH2 engine, and it's too heavy for a role where high thrust is
not all that important. A small cluster of RL10s would give a noticeably
larger TLI payload, and could probably provide engine-out capability too.
But it wouldn't have enough thrust for use as a launcher second stage.
john....@gmail.com
> >>
> >> The Shuttle gets roll control (partly) by gimballing the
> >> nozzles on the SRBs, which are offset from the vehicle CG.
Note the admission that two SRBs are required, and that their
contribution to roll control is shared with the three main engines.
> >> An SRB only has no intrinsic roll control, because gimbaling
> >> the nozzle only controlls pitch and yaw, and can't exert a
> >> torque about the longitudinal axis. Such a vehicle would require
> >> either thrusters, or vanes on fins or in the exhaust to provide
> >> such torque, or rely on a roll-control system in the upper
> >> stages.
Note the admission (applicable to the separated SRBs of Mission 51-L)
that SRB nozzle position on a lone SRB has no effect whatsoever on the
SRB's roll orientation.
> >It's certainly refreshing to see *anyone* who posts to the sci.space
> >groups admit this. Jon Berndt, take notice!
>
> There's nothing to "admit" here with regards to your nutty theories,
> Maxson.
I don't believe there was any confusion whatsoever in my reference to
the inadequate efforts of one or more NASA apologists (i.e., Rube
Goldberg oriented, double-speak efforts).
Challenger's Ghost
Rand Simberg
"gh...@gmail.com" <john....@gmail.com> made the phosphor on my
monitor glow in such a way as to indicate that:
>Rand Simberg wrote:
>> >>
>> >> The Shuttle gets roll control (partly) by gimballing the
>> >> nozzles on the SRBs, which are offset from the vehicle CG.
>
>Note the admission that two SRBs are required, and that their
>contribution to roll control is shared with the three main engines.
The "admission"? It was my point.
I'm not sure what yours is, but I suspect that it will improve with
proper medication.
john....@gmail.com
> On 16 May 2005 17:41:23 -0700, in a place far, far away,
> "gh...@gmail.com" <john....@gmail.com> made the phosphor on my
> monitor glow in such a way as to indicate that:
>
> >Rand Simberg wrote:
> >> >>
> >> >> The Shuttle gets roll control (partly) by gimballing the
> >> >> nozzles on the SRBs, which are offset from the vehicle CG.
> >
> >Note the admission that two SRBs are required, and that their
> >contribution to roll control is shared with the three main engines.
>
> The "admission"? It was my point.
Whereupon I candidly admitted that it was "certainly refreshing,"
remember? It hasn't been that long ago, Rand (unlike most of your
rather unenlightening comments about the Challenger cause).
> I'm not sure what yours is, but I suspect that it will improve with
> proper medication.
Better check your own, Rand; you may not have fully "recovered" yet.
Fortunately, I have yet to find myself in need of any.
Challenger's Ghost
Murray Anderson
"Henry Spencer" <he...@spsystems.net> wrote in message
news:IGL8t...@spsystems.net...
Even with two more failures Delta II would be one of the better launchers.
Unfortunately we have to deal with moderate sample sizes when dealing with
most launch vehicles.
With the Proton there's enough data for a contingency table analysis:
Stage failures # of flights Expected # Expected #
since 1970 (equal probs) (weighted by # of engines)
4 290 5.98 10.81
8 286 5.89 7.11
3 278 5.73 3.45
8 261 5.4 1.63
Chi-squared (equal probs) = 3.96
Chi-squared (weighted by # of engines) = 29.41
Both of these are on 3 degrees of freedom, and the first is insignificant,
the second highly significant.
These results are consistent with equal failure probabilities per stage.
A mixed model, where you average the two expectations gives
Chi-squared = 8.93, which is marginally significant (hypothesis rejected).
This certainly casts doubt on the multiple engines = unreliable thesis.
Murray Anderson
Scott Lowther
Not sure how much detail I can go into WRT the ATK design, as I'm not
sure what they've made public, but yes, there's a distinct roll (and
attitude) control section at the head end of the CEV-RSRM. The aft fins
are gone, which is, artistically, a shame.
Henry Spencer
Tom Cuddihy <tom.c...@gmail.com> wrote:
>> How about roll control?
>
>I didn't think to ask about it. Is there any reason it would be
>different than pitch and yaw control?
As others have noted, you can't do roll control with only a single
gimbaled nozzle. On the other hand, there aren't any very strong external
roll torques on a symmetrical vehicle, so if there isn't *too* much of a
problem with asymmetric throat/nozzle erosion in the SRB, quite a small
thruster pack will suffice for roll control. (There have, mind you, been
a few infamous examples of underestimating how big a thruster pack was
required...)
Tom Cuddihy
Tom Cuddihy wrote:
> Scott Lowther wrote:
>
> >
> > My suggestion was to install simple capsules on the noses of each,
> stack
> > 'em both on the pad, have some rich maniacs pay good money to ride
in
>
> > the capsules, and launch simultaneously and see which one gets to
> > 100,000 feet first. My boss liked the idea, but said the chances of
> that
> > were pretty slim...
>
> My idea is to make it a 'survivor' like show, with all the
participants
> being culled from various media outlets, with viewers calling in and
> voting down participants until one lucky journalist gets a ride to
> mach 17 and 18 gees...
>
I've now decided who the lucky journalist should be: Michael Isikoff,
or if he's unavailable, any other Newsweek editor will do.
cuddihy
Jon S. Berndt
> john....@gmail.com made the phosphor on my monitor glow in such a
> way as to indicate that:
> >It's certainly refreshing to see *anyone* who posts to the sci.space
> >groups admit this. Jon Berndt, take notice!
>
> There's nothing to "admit" here with regards to your nutty theories,
> Maxson.
The Thiokol image I've seen for an SRB-based CEV launcher has fins.
Jon
Scott Lowther
>The Thiokol image I've seen for an SRB-based CEV launcher has fins.
>
>
>
No longer. In any event, they were not actuated fins, it seems.
Damon Hill
news:IGLJ3...@spsystems.net:
Whereas one or several RL60s could do the job nicely.
--Damon
Jon S. Berndt
> Jon S. Berndt wrote:
>
> >The Thiokol image I've seen for an SRB-based CEV launcher has fins.
> >
> No longer. In any event, they were not actuated fins, it seems.
No wonder they're gone.
I was wondering about how effective the SRBs could be at inducing an
unintended roll in the first place (did Henry bring this up in an earlier
posting in this lengthy thread)? As I recall, the roll problem with SS1 on
its first X-Prize flight was instigated by a nozzle throat problem that
caused a thrust imbalance that had a roll-causing component.
Jon
john....@gmail.com
>
> As I recall, the roll problem with SS1 on its first X-Prize
> flight was instigated by a nozzle throat problem that
> caused a thrust imbalance that had a roll-causing component.
Please provide a reputable scientific reference and/or published
engineering consensus to support your recollection.
Dr. Eugene Covert (MIT) told me a problem with repeatability prevented
him from properly investigating Challenger's 51-L control problems.
What repeatability evidence to you have to show us for SS1?
Challenger's Ghost
Earl Colby Pottinger
> Rand Simberg wrote:
>
> > >Scott Horowitz was pretty convincing that these are not legitimate
> > >concerns, for the following reasons:
> > >1. Yes, but the explosion happened because hot gas burned through
> the
> > >LOX/H2 tank. Solid rockets don't explode.
> >
> > The people at the rocket lab, who lost half a mountain to a Titan
> > booster test failure, will be surprised to hear this.
> >
> several people have mentioned that--we didn't discuss it, none of us
> students knew enough to ask about it, but supposedly this kind of
> explosive situation has never happened in 240 SRB flights.
The point is making point-blank statements like the above one ie, "Solid
rockets don't explode" leads people into not planning for possible failure
modes that really do exist. If solid fuel rockets really did not explode you
can follow certain design short-cuts verses what you may think to do/add to
try and help people survive an explosion.
Any point-blank statement that does not match reality (even if there is only
one execption found) can lead to dangerous assumtions.
George William Herbert
>>> [SRBs don't explode]
>>
>> The people at the rocket lab, who lost half a mountain to a Titan
>> booster test failure, will be surprised to hear this.
>
>several people have mentioned that--we didn't discuss it, none of us
>students knew enough to ask about it, but supposedly this kind of
>explosive situation has never happened in 240 SRB flights.
240 Shuttle SRB flights; if you expand out to "large solids"
then it's happened 3 times in recent history: the Titan
booster test that went high order and dissassembled the
test stand and a chunk of the mountain, and one flight
Titan IV and one flight Delta II, both of the flight
losses being less catastrophic than the test stand
near or actual detonation incident.
The particulars of the Titan ground explosion are not
likely to repeat; it was an unpleasant discovery about
the nature of solid rocket internal ballistics, and we
know that lesson now. Rarefaction waves inside the
casing ok, compression bad, and choking very bad.
Flat internal surfaces, or slope them to avoid
any compression shocks in the gas flow.
But the general form of the accident could repeat,
if a large chunk of propellant grain breaks off and
chokes the gas flow somewhere in the casing.
And is always by the nature of the vehicle a risk
for any solid (and, any hybrid, though their
oxidizer injection nature and transient energy
potential in the casing at any time reduce the
magnitude of energy release in potential failures
significantly).
-george william herbert
gher...@retro.com
Derek Lyons
>In article <1116273457....@g43g2000cwa.googlegroups.com>,
>Tom Cuddihy <tom.c...@gmail.com> wrote:
>>> How about roll control?
>>
>>I didn't think to ask about it. Is there any reason it would be
>>different than pitch and yaw control?
>
>As others have noted, you can't do roll control with only a single
>gimbaled nozzle. On the other hand, there aren't any very strong external
>roll torques on a symmetrical vehicle, so if there isn't *too* much of a
>problem with asymmetric throat/nozzle erosion in the SRB, quite a small
>thruster pack will suffice for roll control. (There have, mind you, been
>a few infamous examples of underestimating how big a thruster pack was
>required...)
One wonders why roll control is needed at all? The C4 and D5 (and
Peacekeeper IIRC) don't have any roll control, instead they keep the
nozzle stable in inertial space by varying it's position in pitch and
yaw as defined by the body axes.
D.
--
Touch-twice life. Eat. Drink. Laugh.
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL
john....@gmail.com
> Jon S. Berndt wrote:
> >
> > As I recall, the roll problem with SS1 on its first X-Prize
> > flight was instigated by a nozzle throat problem that
> > caused a thrust imbalance that had a roll-causing component.
Maybe this will help clear up your confusion:
<http://www.strategypage.com/messageboards/messages/21-160.asp>
> Please provide a reputable scientific reference and/or published
> engineering consensus to support your recollection.
This piece from HobbySpace.com quotes from Aviation Week (10/10/2004):
<<A slightly negative angle of attack (AOA) at high Mach reduced the
directional stability and the SS1 yawed about 8 deg. Then a "strong
dihedral effect coupled the yaw into roll, and the nose pitched up
about 15 deg. as well, starting a snap roll motion that was
uncomfortable for Melvill."
That soon settled into a pure roll at about 180deg./sec. Before
aerodynamic controls became useless due to the thinning atmosphere,
Melvill was able to reduce the roll to about 140deg./sec using left
rudder and rudder trim.
After the engine was shut down and the feather deployed, he was able to
use the cold-gas reaction control system to eliminate the roll
completely. Rutan was glad to see this tested but noted that it used up
most of the gas and said "we don't need to try that again."
For the second flight, a positive AOA was maintained. However, you
don't want too much else the craft goes on its back. So a less
aggressive pullup was done. These measures successfuly prevented the
roll problem.>>
Challenger's Ghost
john....@gmail.com
> he...@spsystems.net (Henry Spencer) wrote:
> >In article <1116273457....@g43g2000cwa.googlegroups.com>,
> >Tom Cuddihy <tom.c...@gmail.com> wrote:
> >>
> >>> How about roll control?
> >>
> >>I didn't think to ask about it. Is there any reason it would be
> >>different than pitch and yaw control?
> >
> >As others have noted, you can't do roll control with only a
> >single gimbaled nozzle. On the other hand, there aren't any
> >very strong external roll torques on a symmetrical vehicle, so
> >if there isn't *too* much of a problem with asymmetric
> >throat/nozzle erosion in the SRB, quite a small thruster pack
> >will suffice for roll control. (There have, mind you, been
> >a few infamous examples of underestimating how big a thruster
> >pack was required...)
>
> One wonders why roll control is needed at all? The C4 and D5 (and
> Peacekeeper IIRC) don't have any roll control, instead they keep the
> nozzle stable in inertial space by varying it's position in pitch and
> yaw as defined by the body axes.
It seems to me that Henry is involved in a bit of presumptory
double-speak, whether knowingly or not.
I take it from the subject under discussion that Henry wrongly assumes
a totally "symmetrical vehicle" (the CEV-SRB combination), while
concurrently alluding (in contradiction to single-booster flight
history) to roll-producing "asymmetric throat/nozzle erosion in the
SRB."
Challenger's Ghost
George William Herbert
>One wonders why roll control is needed at all? The C4 and D5 (and
>Peacekeeper IIRC) don't have any roll control, instead they keep the
>nozzle stable in inertial space by varying it's position in pitch and
>yaw as defined by the body axes.
Neither did some early Atlases. But historical experience is
that in practice, the symmetrical assumptions in both the airflow
and thrust alignment are somewhat optimistic, and vehicles tend
to pick up roll over time.
An ICBM with robust PBV is probably ok; the bus can despin prior
to RV release. Some space launch payloads might be ok with
moderate vehicle spin (many get spun up prior to release,
in fact). But there have been launchers where the spin was
problematic for launcher operation and payloads which didn't
put up with the spin.
So, the default nowadays is to keep it 3-axis stable and prevent
roll with little thrusters.
-george william herbert
gher...@retro.com / gher...@venturerspace.com
Henry Spencer
Damon Hill <damonun...@comcast.nyet> wrote:
>> In particular, you probably would *not* use a J-2 or straightforward
>> J-2 derivative for a pure TLI stage. The J-2's Isp is not really very
>> good for a LOX/LH2 engine, and it's too heavy for a role where high
>> thrust is not all that important. A small cluster of RL10s would give
>> a noticeably larger TLI payload, and could probably provide engine-out
>> capability too. But it wouldn't have enough thrust for use as a
>> launcher second stage.
>
>Whereas one or several RL60s could do the job nicely.
Which job? The problem remains: a stage optimized for TLI does not have
the thrust to be a second stage, while something with enough thrust to be
a second stage has excessive engine and structure mass for the TLI role.
Conceivably you could take a multi-engine second stage and derive a better
TLI stage by deleting some of the engines. You'd still pay a mass
penalty, but it would be substantially reduced, at the cost of extra
engineering work.
The point is, this second stage *isn't* "a stage you were going to build
anyway", even if the assumptions about TLI stage size are right. It's a
stage that somewhat resembles a stage you were going to build anyway, to
the point that a purpose-built second stage might well be suboptimal but
workable for the TLI role. (Vice-versa wouldn't work.)
Henry Spencer
George William Herbert <gher...@retro.com> wrote:
>The particulars of the Titan ground explosion are not
>likely to repeat; it was an unpleasant discovery about
>the nature of solid rocket internal ballistics, and we
The story I heard at the time -- unconfirmed -- is that we knew about it
beforehand too: the Hercules engineers who reported ominous preliminary
results, and requested approval to investigate the interior ballistics
more thoroughly, were told that the budget did not permit it and they
would just have to cross their fingers and pray. (The underlying problem
was that the development contract was fixed-price, and Hercules had been a
government contractor for so long that it had forgotten how to make
realistic cost estimates.)
Henry Spencer
Derek Lyons <fair...@gmail.com> wrote:
>One wonders why roll control is needed at all? The C4 and D5 (and
>Peacekeeper IIRC) don't have any roll control, instead they keep the
>nozzle stable in inertial space by varying it's position in pitch and
>yaw as defined by the body axes.
You can get away with this for unmanned launch if (a) you're confident
that the resulting roll rates won't be too high for guidance and pitch/yaw
control to keep up, (b) there are no liquid propellants/lubricants/etc.
whose flow control might be messed up by centrifugal force, (c) the
payload either doesn't care about being left with a spin or is prepared to
despin itself, and (d) there are no issues with things like radio-antenna
coverage.
The Athena (nee LLV) series of launchers are indeed allowed to roll slowly
during powered ascent, but they do have roll thrusters to ensure that the
rate doesn't get too high.
A lot of older launchers have old-technology guidance systems which want
to keep the pitch axis perpendicular to the trajectory plane, and thus
need full roll control. (Some of them, like Long March, have rotating
pads, so the axis-trajectory alignment can be established before launch;
others, like the Saturn V, do a roll maneuver immediately on liftoff to
establish it.)
Most liquid-fuel rockets need to severely limit roll rates to prevent tank
drains from being uncovered before the tank is empty, as happened to the
second Ariane 5 after the unexpectedly large roll torque from its main
engine overwhelmed its roll control.
Manned launches generally want full roll control, partly for comfort and
partly to maintain a stable view out the window for pilot monitoring of
the guidance system. (Asymmetric configurations like the shuttle often
also have antenna-coverage issues.)
Tom Cuddihy
> But the general form of the accident could repeat,
> if a large chunk of propellant grain breaks off and
> chokes the gas flow somewhere in the casing.
> And is always by the nature of the vehicle a risk
> for any solid (and, any hybrid, though their
> oxidizer injection nature and transient energy
> potential in the casing at any time reduce the
> magnitude of energy release in potential failures
> significantly).
>
>
> -george william herbert
> gher...@retro.com
This statement is objectively true--but it either misses the point or
intentionally muddies the waters when it comes to overall vehicle
reliability and safety. It's akin to the reasoning used to ban
nukes,"solids are dangerous!" like "nuclear power is dangerous!", never
mind the actual reliability numbers.
The fact is that the SRBs so far have a better overall safety record
than any liquid booster available. The fact that large solids are
capable of having explosive failures is uncontested--but also
completely irrelevant unless considered with the reliability numbers.
Liquid boosters are prone to explosive failures, albeit by a different
mechanism. The large number of SRB flights results in reliability
numbers with a statistically small confidence interval compared to a
comparable liquid booster, very few of which have launched often enough
to provide adequate reliability data. Even with large confidence
intervals for liquids, my hunch is that the SRB would still come out
ahead.
cuddihy
Jake McGuire
> This statement is objectively true--but it either misses the point or
> intentionally muddies the waters when it comes to overall vehicle
> reliability and safety. It's akin to the reasoning used to ban
> nukes,"solids are dangerous!" like "nuclear power is dangerous!",
never
> mind the actual reliability numbers.
You were the one relaying the claim that solid rocket boosters were
safer than liquid boosters because they "don't explode." From your
original post on the thread:
> 1. Yes, but the explosion happened because hot gas burned through the
> LOX/H2 tank. Solid rockets don't explode.
- and -
> Solid boosters DONT explode like Lox/ H2, they just leak hot gas.
If you want to claim that the SRBs have demonstrated higher reliability
than existing liquid fueled stages, fine. There then could have been a
response that liquid fueled rockets usually fail in a manner amenable
to safe escape such as unexpected early shutdowns or gradual
underperformance, and that solid motors that have a tendency to go
"bang" violently and without warning.
We could then move on to demonstrated stage reliability, questions
about where the guidance system for the integrated vehicle would come
from and how reliable *that* would be, ponder the relevance of the
Delta III failure due to incompletely understood whole-vehicle
structural modes (do you charge that to solids or liquids?), and so on.
That could actually be an interesting discussion - my gut reaction is
that we've spent huge sums of money designing launch vehicles to
varying states of maturity and have not very much to show for it (ALS,
NLS, OSP, blah blah blah) and trying yet again is not a good idea.
Bite the bullet and launch on EELV Heavy, spend more money getting
in-space rendezvous and propellant transfer down, and generally move
forward on things. The world doesn't need yet another slightly better
launch vehicle.
-jake
Scott Lowther
>The point is, this second stage *isn't* "a stage you were going to build
>anyway",
>
Unless it is. As I said, the S-IVb served two roles. Perhaps not
perfectly optimised for either, but so what? Perfect optimization, in
the world of gubmint contracting, is for when you don't really care
about gettign the job done.
Scott Lowther
>Tom Cuddihy wrote:
>
>
>>This statement is objectively true--but it either misses the point or
>>intentionally muddies the waters when it comes to overall vehicle
>>reliability and safety. It's akin to the reasoning used to ban
>>nukes,"solids are dangerous!" like "nuclear power is dangerous!",
>>
>>
>never
>
>
>>mind the actual reliability numbers.
>>
>>
>
>You were the one relaying the claim that solid rocket boosters were
>safer than liquid boosters because they "don't explode." From your
>original post on the thread:
>
>
>
>>1. Yes, but the explosion happened because hot gas burned through the
>>
>>
>
>
>
>>LOX/H2 tank. Solid rockets don't explode.
>>
>>
>
>- and -
>
>
>
>>Solid boosters DONT explode like Lox/ H2, they just leak hot gas.
>>
>>
>
>If you want to claim that the SRBs have demonstrated higher reliability
>than existing liquid fueled stages, fine. There then could have been a
>response that liquid fueled rockets usually fail in a manner amenable
>to safe escape such as unexpected early shutdowns or gradual
>underperformance, and that solid motors that have a tendency to go
>"bang" violently and without warning.
>
The violence of solids going BANG is often overstated. With vanishingly
rare exceptions, solids don;t detonate (a few military motors made from
class 1.1 propellants can do so, but the class 1.3 propellants used in
the bulk of space launches don't). So what you get is case burst, caused
generally by weakened cases for whatever reason. It's spectacular, but
there is no true explosion.
Len Lekx
<scottl...@ix.netcom.SPAMBLOK.com> wrote:
>The violence of solids going BANG is often overstated. With vanishingly
>rare exceptions, solids don;t detonate (a few military motors made from
>class 1.1 propellants can do so, but the class 1.3 propellants used in
>the bulk of space launches don't). So what you get is case burst, caused
>generally by weakened cases for whatever reason. It's spectacular, but
>there is no true explosion.
Problem is - most people wouldn't see it that way. I've seen hobby
rockets that have suffered ruptured casings, spit nozzles, blow-bys,
and other forms of CATO failures... and pretty much every time, it's
been referred to by the non-rocketry spectators as an explosion.
In most peoples' minds, burn-rate and shock propagation don't
matter. If it creates a ball of fire and a loud BANG, then it's an
explosion. :-(
Paul F. Dietz
> In most peoples' minds, burn-rate and shock propagation don't
> matter. If it creates a ball of fire and a loud BANG, then it's an
> explosion. :-(
I would call it an explosion if you have a sudden release of
sufficient gas to form a blast wave in the surrounding atmosphere.
This doesn't even require any chemical reaction -- sudden
rupture of a boiler can cause an explosion.
Paul
Murray Anderson
"Tom Cuddihy" <tom.c...@gmail.com> wrote in message
news:1116449659....@g49g2000cwa.googlegroups.com...
Actually no. You can't distinguish 1% from 0.5% with sample sizes of order
200.
A contingency table analysis of the SRB and first stages of Delta (all
versions except IV) and Proton shows no difference:
Delta Proton SRB All Expected
Failure 3 4 1 8 3.02 2.79
2.19
Success 311 286 226 823 310.98 287.21 224.81
All 314 290 227 831
Chi-squared = 1.18 on 2 df (not significant)
The values for Delta come from kevinforsyth.net/delta/delta2.htm
The values for Proton come from the Users Guide at the ILS website.
The Proton data start in 1970, whereas the Delta ones go back to 1960, to a
time when all launch vehicles were less reliable. If we start the
comparisons in 1981, when the SRBs were first used, we get 158 Delta flights
with one first stage failure, 229 Proton flights with 1 first stage failure,
and 226 SRBs flown with 1 failure.
This is rather flattering to the Proton, but if you look at the Proton
second stage it doesn't look so good (5 failures since 1981).
The shuttle SRB has a good record, as rockets go, but doesn't stand out from
other rocket stages, and remember that it would have to be modified to use
as a true first stage. You would need to develop a new hydrogen-burning
upper stage of about 100 tons to get a 20 ton vehicle in orbit.
Murray Anderson
Henry Spencer
Tom Cuddihy <tom.c...@gmail.com> wrote:
>Liquid boosters are prone to explosive failures, albeit by a different
Name three recent examples.
Historically, liquid-rocket failures are almost always fairly benign,
assuming a modicum of sense from the control system. (Continuing to run
the engine, instead of hastily shutting it down, when the high-speed
turbomachinery is about to start sucking air does not count.) Liquid
engines may refuse to start, or stop suddenly, but they rarely explode.
Challenger's SSMEs were calmly executing an orderly shutdown, due to
grossly improper inlet conditions, until they lost electric power as the
orbiter disintegrated around them.
The usual failure modes of liquid rockets are to underperform like the
recent Delta IV Heavy, or to break up due to structural failure or loss of
control like Challenger (with a spectacular ball of flame as spilled fuel
burns, but no explosion).
Jake McGuire
> The violence of solids going BANG is often overstated. With
vanishingly
> rare exceptions, solids don;t detonate (a few military motors made
from
> class 1.1 propellants can do so, but the class 1.3 propellants used
in
> the bulk of space launches don't). So what you get is case burst,
caused
> generally by weakened cases for whatever reason. It's spectacular,
but
> there is no true explosion.
Absolutely. But LOX/LH2 rockets don't detonate either, as near as I
can tell. Challenger certainly didn't. Liquid rocket engines may
occasionally violently disassemble during development, but this seems
to be pretty uncommon during flight operations. The last time a liquid
rocket engine failed violently in flight (the Delta III RL-10) the
stage didn't even come apart.
I don't know what the design drivers for manned spaceflight abort
systems are - it could be that the engines failing one second after
liftoff and dropping the whole thing down on the pad requires more
getting away from in a hurry than an SRB case letting go at max Q -
you've done more work on this than I have - can you comment?
Reliability and safety aren't the same thing, and the relationship
between them is different on an ELV launching a satellite and an ELV
with a launch escape system launching people.
-jake
Scott Lowther
>Scott Lowther wrote:
>
>
>>The violence of solids going BANG is often overstated. With
>>
>>
>vanishingly
>
>
>>rare exceptions, solids don;t detonate (a few military motors made
>>
>>
>from
>
>
>>class 1.1 propellants can do so, but the class 1.3 propellants used
>>
>>
>in
>
>
>>the bulk of space launches don't). So what you get is case burst,
>>
>>
>caused
>
>
>>generally by weakened cases for whatever reason. It's spectacular,
>>
>>
>but
>
>
>>there is no true explosion.
>>
>>
>
>Absolutely. But LOX/LH2 rockets don't detonate either,
>
Typically, no. About the only way you could get a lquid rocket to truly
detonate woudl be to somehow mix the propellants, and then set up a
supersonic shock. Seems quite unlikely.
>I don't know what the design drivers for manned spaceflight abort
>systems are - it could be that the engines failing one second after
>liftoff and dropping the whole thing down on the pad requires more
>getting away from in a hurry than an SRB case letting go at max Q -
>you've done more work on this than I have - can you comment?
>
>
Depends on *where* the SRB unzips. If you assume the nozzle blows off,
then it's a fairly sedate failure. If you assume the forward dome blows
off, the crew are up shit creek. The difference is this: in each case,
the impulse imparted from the suddenn exposure (you have a case at, say,
800 psi, and 13 or so feet in diameter... total force is something like
15 millions pounds, but of course it only lasts for a split second.
Nevertheless, it's a hell of a kick in the pants... but if that kick in
the pants also has to kick the bulk of the mass of the booster (if the
aft dome pops off), then the felt acceleration up in the CEV is far
lower than if that kick in the pants *doesn't* have to accelerate the
bulk of the booster (forward dome cuts loose).
If the booster splits down the side, then there could well be no forward
impulse at all.
As for liftoff vs. mx Q, liftoff sucks not because it's hard to get
away, but because you won't go up very high (might get caught in the
fire on the way down), and could hit solid ground. One thing I wonder
about is one of the outboard RS-68's going *burp* at Max Q. Sudden
serious thrust imbalance...
Henry Spencer
Jake McGuire <jamc...@yahoo.com> wrote:
>I don't know what the design drivers for manned spaceflight abort
>systems are - it could be that the engines failing one second after
>liftoff and dropping the whole thing down on the pad requires more
Those two cases are both hard, in different ways.
For the Apollo escape system, which is a reasonable comparison, there were
in fact four critical cases:
+ Pad abort requires altitude for parachute deployment, and horizontal
distance to avoid parachute overheating from the fireball. This sets the
total impulse (thrust*time) of the escape system, so in a sense it takes
"the most getting away from".
+ Transonic abort has to fight a huge amount of base drag until the
capsule is well clear of the booster. This sets the thrust required.
+ Max Q abort is the worst case for capsule structural loads, due to both
aerodynamics and escape-system exhaust plumes impinging on the spacecraft.
This sets stability requirements for the escape burn -- the spacecraft
*must not* tumble during the burn.
+ High-altitude aborts, where aerodynamics are insignificant, can also
have impingement problems, and attitude control for reentry becomes a
serious issue.
Oh yes, and the major design driver for the Boost Protective Cover over
the capsule (assuming you use one, which is probably a good idea) is not
escape at all, but tower/BPC jettison, especially if the normal jettison
sequence fails and it becomes necessary to use the backup sequence which
fires the main escape motor.
Henry Spencer
Scott Lowther <"scottlowtherAT ix DOT netcom DOT com"> wrote:
>The violence of solids going BANG is often overstated. With vanishingly
>So what you get is case burst, caused
>generally by weakened cases for whatever reason.
Correct -- basically a boiler explosion on steroids. Which is still
plenty violent enough, especially if you're sitting on top of the thing.
>It's spectacular, but there is no true explosion.
Only by a narrow and pedantic definition of "explosion". Even in
technical literature, the term is not restricted to detonations.
Tom Cuddihy
Jake McGuire wrote:
> We could then move on to demonstrated stage reliability, questions
> about where the guidance system for the integrated vehicle would come
> from and how reliable *that* would be, ponder the relevance of the
> Delta III failure due to incompletely understood whole-vehicle
> structural modes (do you charge that to solids or liquids?), and so
on.
>
> That could actually be an interesting discussion - my gut reaction is
> that we've spent huge sums of money designing launch vehicles to
> varying states of maturity and have not very much to show for it
(ALS,
> NLS, OSP, blah blah blah) and trying yet again is not a good idea.
> Bite the bullet and launch on EELV Heavy, spend more money getting
> in-space rendezvous and propellant transfer down, and generally move
> forward on things. The world doesn't need yet another slightly
better
> launch vehicle.
The difference between 20,000 lbs to LEO (as both EELV-H are analyzed
for) and 40,000 lbs is not 'slight,' especially when it comes to manned
systems. The starting assumption of a heavier lift requirement may
indeed be wrong, but it's more than just NASA job continuation that's
being considered.
cuddihy
Jake McGuire
> Those two cases are both hard, in different ways.
>
> For the Apollo escape system, which is a reasonable comparison, there
were
> in fact four critical cases:
>
> + Pad abort
> + Max Q abort
> + High-altitude aborts
So it sounds like given aerodynamically unstable boosters (which means
you might have to fire your abort system RIGHT NOW during the first
three cases), the abort requirements are not appreciably different for
liquid or solid boosters, with the exception that there are some rare
solid failure modes that might be unsurvivable (e.g. forward dome
blowing off per Scott Lowther, except that you'd overdesign that joint
and make the nozzle a structural fuse).
Is this an accurate summary?
-jake
Ed Kyle
> >
> > The fact is that the SRBs so far have a better overall safety
record
> > than any liquid booster available.
>
order
> 200.
> A contingency table analysis of the SRB and first stages of Delta
(all
> versions except IV) and Proton shows no difference:
Aren't you cherry-picking a bit here? What would
happen if you added Rocketdyne-powered Atlas or
Ariane 4 or R-7 or Titan or all of the Thor-based
launchers, etc?
It only makes sense that a solid should be more
reliable than a liquid due to complexity reduction.
Consider Minuteman, which started flying in 1961 -
back when liquid boosters were more frequently
falling out of the sky. By the end of 2004, there
had been 838 Minuteman or Minuteman-based launches
(including two orbital Minotaur flights) with 25
failures. During the same time frame there had
been 685 Thor-based flights (including IRBM, Thor,
Delta, and NASDA N-1, N-2, H-1) with 76 failures,
581 Rocketdyne Atlas flights with 112 failures,
366 Titan flights with 61 failures, 1,693 R-7
flights with 96 failures, 311 Proton launches with
37 failures, etc. This isn't a comparison of just
booster stages, but entire vehicles.
The comparison isn't perfect, of course, since solid
boosters were used on Thor, Titan and Atlas and
accounted for a few failures. But I think it shows
a trend.
I think solids are still more reliable today, but
there can be little doubt that the reliability
difference between solid and liquid has closed.
Consider just the "modern" big solid boosted
launch vehicles - STS, Titan 3/4, H-II/IIA,
and Ariane 5. Up to the end of 2004, they had
flown 267 times with 24 total failures. Four of
the failures were caused by solid boosters. Four
were problems with liquid core stages. The rest
were upper stage or guidance or fairing problems.
Solids still seemed to have a slight edge with this
"modern" group, but it is hard to discern in the
statistical haze.
- Ed Kyle
Derek Lyons
>Derek Lyons <fair...@gmail.com> wrote:
>>One wonders why roll control is needed at all? The C4 and D5 (and
>>Peacekeeper IIRC) don't have any roll control, instead they keep the
>>nozzle stable in inertial space by varying it's position in pitch and
>>yaw as defined by the body axes.
>
>Neither did some early Atlases. But historical experience is
>that in practice, the symmetrical assumptions in both the airflow
>and thrust alignment are somewhat optimistic, and vehicles tend
>to pick up roll over time.
>
>An ICBM with robust PBV is probably ok; the bus can despin prior
>to RV release.
<nods> In the case of the SLBM's cited above, the bus wants to roll a
bit after burnout and before commencing deployment - so having some
roll isn't an issue. You simply stop any existing roll at the angle
you desire rather than inducing and removing a roll.
Makes sense.
Tom Cuddihy
I guess I have trouble distinguishing spectacular balls of flame from
explosions. Still, an orderly liquid engine shutdown that leaves a
capsule in a ballistic trajectory landing in the North Atlantic ocean
is not much better.
It might be obvious from my comments I'm short on the long experience
you have with launch vehicles, and I'll admit to making sweeping
generalizations in my opening comment that aren't completely proveable.
But two things--first, my opening post was intended to summarize
comments from a class I attended that I largely agreed with, and to
open up those ideas for comment by those more knowledgeable than I.
I greatly appreciate your, Ed Kyle, and Murray Anderson's informative
analyses. It's given me a lot of food for thought and a kernel of a
thesis idea.
Second, despite direct contradiction of some of my more reckless
assertions about the inherent booster safety, I cannot shake an
intuitive grasp that this is the right way for NASA to go, and here's
some of my reasoning in that regard:
-No, solids are not 100% safe. But when you look to two stage liquid
rockets capable of lofting a large capsule, they all have solid booster
strapons anyway, an overall design consideration that appears (from my
ignorant perspective on current technology) to be mandatory when
designing to limit staging events and gee loading. A liquid booster
engine and nozzle designed to maximize ISP 2/3 of the way up just
cannot be given adequate thrust to liftoff--at least not without
violating max Q constraints or requiring a very large range of
throttling that further lowers engine thrust/weight ratio. This appears
to be mitigated in most cases by increasing the number of core
stages--in Delta IV's case to three, and thus further increasing
complexity and lowering inherent reliability, or using lots of solid
boosters like Delta-II. But if you have to use solids already, why not
stick with the SRB?
-Yes, this design requires restarting a discontinued rocket engine
line, developing a new upperstage, and performing some integrated
testing on the system--which argues for an EELV approach--assuming that
overall mass-to-LEO in a single launch is not a consideration.
Intuitively I cannot believe in that assumption. Ideas requiring 5 or 6
EELV launches/rdvz to provide sufficient mass for a single lunar
mission just does not pass the smell test. Considering how frequent
launch delays are, it's an insane idea.
The longer we wait to develop a big-mass-to-orbit booster, the more it
will cost, and specifically, if we are not bending metal on a larger
launcher by January 2009 (the next administration inauguration), it is
likely to be abandoned. I have no faith in Congressional vision and
foresight.
Anyway, those are my admittedly unscientific reasons, if there are
unconsidered gaping holes in my specific argument, please point then
out.
tom cuddihy
Andrew Gray
>
> -No, solids are not 100% safe. But when you look to two stage liquid
> rockets capable of lofting a large capsule, they all have solid booster
> strapons anyway, an overall design consideration that appears (from my
> ignorant perspective on current technology) to be mandatory when
> designing to limit staging events and gee loading. A liquid booster
The current two-stage systems use solid boosters, but there's no
fundamental reason for that - it's arguably more a case of the initial
designs being underpowered. Two-stage liquid launchers have worked fine
in the past.
Titan II was two-stage, although I'll give you that it wasn't too large
a capsule. Saturn IB, on the other hand, certainly was capable of
lofting a large capsule - fifteen tonnes or so, versus four tonnes for
Titan II. (and the earlier Saturn I was capable of ~9 tonnes)
--
-Andrew Gray
andre...@dunelm.org.uk
Ed Kyle
>
> The difference between 20,000 lbs to LEO (as both EELV-H are analyzed
> for) and 40,000 lbs is not 'slight,' especially when it comes to
manned
> systems. The starting assumption of a heavier lift requirement may
> indeed be wrong, but it's more than just NASA job continuation that's
> being considered.
I may be misreading you here, but as I understand
it the suggested SRB-based launcher is less
powerful than the existing Delta IV Heavy. The
SRB + SIVB-class launcher would be in the 18 metric
ton to LEO class. The existing Delta IV Heavy can
boost 24 metric tons into the ISS orbit - and
probably 25 tons or more to a lunar mission LEO
parking orbit from Cape Canaveral.
For probably about the same that it would cost to
develop the new SRB launcher, Delta IV could be
upgraded to the mid-30 ton to LEO range by upgrading
to a lightweight RS-68 thrust chamber and by
developing a more powerful upper stage engine. Or
Atlas V Heavy could be developed - it would start
with a near 30-ton LEO capability.
- Ed Kyle
Jeff Findley
"Andrew Gray" <andre...@dunelm.org.uk> wrote in message
news:slrnd8plfu.mf...@compsoc.dur.ac.uk...
> The current two-stage systems use solid boosters, but there's no
> fundamental reason for that - it's arguably more a case of the initial
> designs being underpowered. Two-stage liquid launchers have worked fine
> in the past.
>
> Titan II was two-stage, although I'll give you that it wasn't too large
> a capsule. Saturn IB, on the other hand, certainly was capable of
> lofting a large capsule - fifteen tonnes or so, versus four tonnes for
> Titan II. (and the earlier Saturn I was capable of ~9 tonnes)
Skylab was orbited by a two stage Saturn V.
Jeff
--
Remove icky phrase from email address to get a valid address.
Ed Kyle
> Intuitively I cannot believe in that assumption. Ideas requiring 5 or
6
> EELV launches/rdvz to provide sufficient mass for a single lunar
> mission just does not pass the smell test. Considering how frequent
> launch delays are, it's an insane idea.
What about ISS? It is an example of what can be
accomplished using low earth orbit rendezvous methods.
ISS currently has a mass of about 187 metric tons -
the biggest man-made thing ever assembled in space.
It took 14 major hardware launches over the course of
six years to put most of this mass in place. There
have been more than 40 launches to ISS altogether.
All have gone off without a major hitch really.
And thanks to launch vehicle diversity, the station
has even managed to survive, continuously occupied,
during the 2.5 year grounding of its main launch
system.
The Apollo lunar missions required less mass than
ISS weighs in low earth orbit. If cyrogenic
propellants, which account for the majority of the
mass, can be stored for extended periods in orbit
(using the propellant depot approach), there is no
reason that earth orbit assembly methods could not
be applied to a lunar mission.
- Ed Kyle