Terminal Velocity and Challenger
Steven B. Harris
A followup on the discussion of terminal velocity and the
Challenger disaster.
Still curious about the aerodynamics of the Challenger loss, I
found a book by Klaus Jensen titled _No Downlink_, which gives a
few more details. The Jensen book actually gives a time from
explosion to crew cabin impact of 2 minutes 45 seconds (2.75
min), so my initial certainty that 2 minutes was an impossibly
short time, seems confirmed. Unfortunately, Jensen does not say
where HE gets the time. Just as unfortunately, the new time is
actually now 15 seconds too long, and I cannot get my little
terminal velocity simulator program to give me times longer than
2.5 minutes, unless I raise the angle of travel at breakup from
50 degrees to an unrealistic 80 degrees from horizontal. The
last figure is unrealistic because we've all seen the tapes, and
the craft is tilted far more than that-- fairly close to 45
degrees. Also, the Jensen book mentions that it was 7 nautical
miles up and 9 nautical miles downrange from the pad at the time
of the explosion, which make it certain that it was going very
far from straight upward, at that point.
Again, the problem is that the estimated impact terminal
velocity on the water at sea-level, also given in Jensen as 204
mph, fixes the aerodynamics of the cabin pretty well, with a
sectional density/drag coefficient of about 800 kg/m^2. That drag
coefficient has to change substantially (to a much higher value)
at higher V's and altitudes, to get the cabin down 15 seconds
later than 2.5 minutes. One might think that 15 seconds here or
there is easy to get, by fooling with a few parameters. Not so.
As mentioned earlier, you have to fool with them a surprising
amount to get 15 seconds. Enough that there are still effects
here, evidently, which we're not taking account of.
Some details in the Jensen book help, and some don't, and some
I don't know what to think of. Two months after the disaster
when the crew cabin was found, and later when several of the
recovered crew 3-min oxygen water-egress cylinders were found to
be 3/4 to 7/8 empty, there was a press briefing about the now
certainty that some of the crew had survived the explosion, and
been conscious and functional for at least long enough for one
guy to turn on the pilot's oxygen bottle, from the position
behind him. The NASA head aerospace doc was asked about how long
you can stay conscious at 46,000 ft with no oxygen (answer--
about 15 seconds), and he mentioned in passing that the crew
cabin had been at that altitude or higher for "almost a minute."
My simulation for 45 degrees gives 52 seconds from 46,000 ft back
down to 46,000 ft again, so that figure works. Hah. Also, it
means that NASA evidently did not completely stonewall the press
on the fall-times, as I had essentially accused them of doing.
My apologies on that.
On the other hand, some of Jensen's other details don't help.
At T+75 seconds, just a second after the last fireball flash, as
all the parts were coming out a the very beginning of their
ballistic paths, the tower tracking data announcer gave his
routine update tracking data for that point, including
(supposedly) a velocity of 2,900 fps. Clearly, that cannot be
correct. Several books of mine have mentioned that the craft hit
mach 1 at 18,000 ft, and was nearly at mach 2 at the explosion.
One source gives mach 1.92, which at that altitude (46,000 ft
mach 1 = 295 m/sec) is 566 m/sec. Since 1,900 fps is 579 m/sec,
I have to believe that the 2,900 fps is a misprint or mis-speak
for 1,900 fps. The only other possibility is that the radar had
been fooled by the faster explosion debris, and actually read out
2,900 fps.
Most interestingly, the Jensen book notes that some of the
debris from the explosion went as high as 117,000 ft on radar.
If you model the necessary vertical velocity component of even
something like a metal bolt with twice the sectional
density/drag ratio as the cabin-- about the same as many bullets-
- and ask how large it needs to be in order to make 117,000 ft
from 46,000 ft, you get an interesting answer. It takes a total
vertical velocity component of close to mach 3.5 (> 1000 m/sec)
to do this. Since the craft was doing less than mach 1.4 in the
upward direction at the time of breakup, you can see that some of
the debris (like bolts and objects of not inconsequential size
and mass) had to emerge with an *extra* velocity of better than
mach 2, and only those that happened to emerge with that extra
delta-V straight upward, might get to such heights. Jensen does
not discuss the the implications of how such a thing has to
happen, but so far as I can see, this is the only way it CAN
happen.
I've had some people tell me that the explosion of Challenger
wasn't really an explosion in the ordinary sense, but only a
controlled breakup and hydrogen/cryogen cloud and flair.
However, something that shoots out stuff large enough to track on
radar, and dense as solid metal, and does so at the speed of a
rifle bullet (relative to the craft's speed), qualifies as an
explosion in my mind. I certainly wouldn't want to be standing
in the vicinity, as grenades and mortars don't produce shrapnel
of nearly that energy, velocity, and penetrative power. It's a
testament to the toughness of the 15 psi pressure vessel crew
cabin that everybody inside wasn't shredded immediately. But it
also explains pretty well why the perforated thing didn't hold
pressure, either. Comments from people with more information
and insight are welcome. It's a matter of record that the two
errant boosters, which contain explosive charges for this
purpose, were blown up by the controller-- and perhaps it was
only debris from them which made it to 117,000 feet. I don't
know.
My little program was originally written to see if I could
model the maximal range of rifle bullets in air, and the terminal
velocity of skydivers. It works pretty well. The space shuttle
calculations have been a spinoff, but an amazingly annoying one,
since they are almost correct, but not quite. And the fudge
factors needed to make them come out right don't look plausable.
Here's one last detail that is more annoying than helpful,
especially if you consider it merely coincidental. But perhaps,
if it isn't, it tells us something more. According to Jensen,
the explosion happened 18 miles off the coast (9 nautical miles
from the pad on the cape), and the cabin was found 20 miles off
the coast. So the horizontal travel from explosion to impact of
the cabin was only 2 miles. That's also very hard to model. At
Mach 1.92, 46,000 ft, terminal velocity 204 mph, I get 6.5
horizontal ballistic miles at 45 degrees, and that's with the
thing falling almost straight down most of the way. In order to
get only 2 miles horizontal travel, I have to raise my angle
again to 80 degrees. It's curious that this also just happens to
exactly give me the 2.75 minutes total time needed, as of course
it goes up quite a bit higher in the narrow parabola. However,
THAT would require that the explosion itself projected the cabin
upward at this angle, not unlike those bolts and other stuff
which got up much higher still.
And perhaps that's what happened. Which would mean the chief
effect of the explosion on the crew section would have been to
kill some of the cabin's forward momentum, while at the same time
either augmenting its upward momentum, or at least not
interfering with it. That would require that in the breakup, the
fireball, or expanding gas ball, somehow mainly got "ahead" of
the cabin, whether above or below it. The ahead part it easy to
believe, as the orbiter is hanging upside down beneith this big
tank. It's even possible that the shock took the upside-down
orbiter in the midsection, and flipped it nose- upward, back-
first and pancaked into the airstream, just before it broke up,
so that the the nose section was blown not only "backward," but
also sky-ward. In either scenario, acceleration on the crew
during such an event would be downward into their seats as the
shuttle was pushed away, and then backward into them as the nose
section broke free-- exactly the direction the seats were
designed to handle. Which would explain why Onizuka, after the
event, was able to reach forward and turn on the oxygen to
Crippen's helmet, as he evidently did-- a maneuver rather
difficult if you are unconscious from negative-g "red-out," or
have a broken neck or dislocated shoulders.
Steve Harris
Dec 8, 99
Re: Terminal velocity of terminal
}astronauts in space shuttles, I'll cross post it to a few space
groups.
}
}The problem of terminal velocity is complicated by a bunch of
}things, not least of which is that you're never sure what the
}coefficient of drag of the object you're modeling is. For a lot
}of aerodynamic objects at "ordinary" speeds and mid-range
}Reynolds numbers (like a terminal velocity fall in air) the
}coefficient is about one. So you can model the drag force Fd as:
}
}Fd = 1/2 D * A * rho * V^2
}
}where
}
}D is drag coefficient-- about 1 for objects at airplane speeds
}A is the presenting area of the object
}rho is the density of air
}V is the velocity
}
}
}A falling object is then subjected to a acceleration which is the
}difference between its weight mg, and the drag force:
}
}force down = m*a(fall) = mg-F = mg - 1/2*A*rho*V^2
}
}dividing out the mass:
}
}acceleration down =
}
}dV(t)/dt = g - [1/2 (A/m) * rho * V(t)^2 ] (equation 1)
}
}When terminal V is reached, obviously a = dV/dt = 0, and the
}weight of the object is supported by air drag.
}
}So (V-terminal)^2 = (2g/rho) * (m/A)
}
}
}You can see that rho, the density of the air, is important. The
}quantity m/A, or mass per presenting area, is sometimes called
}"sectional density", and you can see that it's the other major
}thing that determines terminal velocity.
}
}
}To check that this equation works as a guesstimate you can try
}some real numbers. For example, the surface area of a human in
}cm^2 typically is 11*(mass in grams)^2/3. You can verify for
}yourself that the corresponding coefficient for a sphere of
}density 1g/cm3 would be only 4.8 or so. But a falling sphere
}would present not its entire 4(pi)r^2 surface area, but only its
}effective cross section, which is 1/4th of that. Humans are
}closer to being 2-dimentional than spheres, and a totally flat
}(2-dimentional) human would present only 1/2 of their total
}surface area. At a guess, a real human in standard skydiving
}arch presents something between: perhaps 1/3rd of total body
}area. For a 70 kg skydiver that works out to be (11/3)*(70,000)-
}^2/3 = 6227 cm^2 or 0.622 m^2. The sectional density of a 70 kg
}skydiver in good arch is then about 70/.622 = 112 kg/m^2. Taking
}rho to be a convenient 1 kg/m^3 at sea level, the terminal
}velocity at sea level of the skydiver then is:
}
}V(terminal) = SQRT (2*9.8*112) = 47 m/sec = 105 mph
}
}That's about right. So we must have been right to guess that D,
}the drag coefficient, is effectively about 1 in these situations.
}
}We've already mentioned Kittinger, in project Manhigh, who exceeded
}mach 1 in spacesuited freefall, during a balloon skydive, due to the
}very low terminal velocities possible at 100,000 feet. If the air
}density is 1/50th of normal, you can go 7 times as fast.
}
}
}****************************
}
}
}Now that we know our math is not too bad, a more complicated
}problem:
}
}Since this discussion has been about things falling from air-
}planes at high altitude, I decided to try this formula on a
}situation in which terminal velocity changes during a long fall,
}and for some "aircraft" sections.
}
}In the Challenger shuttle disaster, the craft blew up 73 seconds
}after launch, at 46,000 ft, and the nose of the craft containing
}the crew cabin/quarters free-fell from there, to the sea. The
}news reports said that NASA estimated from calculations that the
}nose section with crew cabin hit the sea at 200 mph, killing
}those aboard only at that time (some of whom were probably
}conscious to the end). Reports also quoted NASA that the time
}from explosion to sea-impact--- which would have been an
}important number, had this ever gone to trial as a pain and
}suffering civil tort-- was about 2 minutes.
}
}We'd like to know: is all this reasonable?
}
}I have no way of guessing the sectional density of the nose of
}the shuttle, but if the 200 mph figure is correct, this implies a
}sectional density about 4 times that of our skydiver (twice the
}velocity = 4 times sectional density). So use a figure of 400
}kg/m^2, and that fixes all the free parameters in our equation,
}including the particular drag coefficient. Now that we have done
}this, we want to know: is the fall-time correct?
}
}One can take equation 1, the dV/dt differential equation given
}above, and solve for the function V(t) by integration, but it's a
}nasty integral since the air pressure isn't constant during the
}fall, and is important. Then you have to differentiate V(t) to
}get x(t), then integrate the ratio of the functions to get t, or
}something. Not for lazy people. At least not lazy ones with my
}math skills.
}
}It's much easier to write a little 20 line BASIC program to
}integrate the equation above numerically, updating velocity,
}position, air density, and time every 0.1 second, until a certain
}distance has been traveled (46,000 feet), and read off the
}figures there, at impact. Which I did. (Anybody interested can
}have a copy of the program, or I can post it, but it's probably
}even easier to write yourself in the language you know best).
}You need to know that air pressure in kg/m^3 as a function of
}height in meters h above sea level is given approximately by the
}natural e exponential equation:
}
}rho(h) = exp[-0.00014*h] (.00014 is probably better than .00013)
}
}The results of running the program show that 0.1 sec is plenty
}fine enough to show negligeable numerical-integration segment
}size error. And of course the program shows impact at 204 mph
}(guaranteed by my choice of sectional density to put into the
}equation, but also showing that the program is working
}correctly).
}
}The output also shows some other interesting things. Maximal
}velocity reached in the Challenger crew cabin fall (assumed to
}start at 46,000 ft at zero velocity) is just short of 390 mph, at
}around 33,780 ft. So here's a case where terminal velocity
}through a max, a quarter of the way through a fall, to nearly
}twice what it eventually wound up as, at impact.
}
}And the total fall time? 113 seconds, or 1.89 minutes.
}
}The last is interesting as exactly the time reported in the
}media, and quite a coincidence. It made me wonder if somebody
}at NASA didn't do the same kind of thing I did (start at V = 0),
}not knowing how far upward the section would go (it was doing
}well over the speed of sound, as I recall) before beginning to
}fall back. Or else errors I've made in modeling this (velocity
}dependence of drag, etc) by chance took care of the extra seconds
}the nose-section should have spent killing its upward velocity,
}before beginning to fall again.
}
}The problem for me, is that the aerodynamic coefficients of the
}craft and all that, are all pretty much locked in by the 200 mph
}sea impact figure. If that is right, there's not much room
}anywhere to subtract from the fall-time, any extra time to ride
}from the explosion to apogee. The only real place to remove some
}time (which involves coming up with faster maximal velocities to
}get the section down faster, then slowing it up again), is in the
}V^2 dependence of the drag force, and also perhaps changing to
}smaller coefficients of drag at different higher velocities than
}the terminal one. Which NASA may be sophisticated to estimate,
}even for a sheared-off front shard of a shuttle...
}
}Naww. Do any of YOU believe this? It's very hard to make any of
}those fixes give smaller *fall* time, but with the same terminal
}impact velocity. Drag force would need to vary by some exponent
}of velocity GREATER than 2 for this-- and if anything, at slow
}speeds it tends to go less. Coefficients of drag or some figure
}of drag similarly have to somehow be less than the impact one,
}when the craft is going faster, up higher. This, too, seems very
}unlikely. Coefficients of drag can drop with higher V at VERY
}high velocities, but the thing never went that fast. Two minutes
}is already the minimal time to get down from 46,000 ft, if your
}impact velocity is terminal (in every sense) and is 200 mph. I
}do NOT see how you can get down faster, in order to use some time
}to keep going up, and have the total remain 2 minutes.
}
}So 2 minutes is the fall time, but not the time from explosion to
}impact. That's longer, but can we estimate by how much? Sure,
}we can make a lower estimate. Velocity at the time of the
}explosion was officially Mach 1.92, which I estimate crudely to
}represent a speed of 550 m/sec at 46,000 ft. My worst estimation
}error is not what Mach is, but that not all of this speed was
}upward, but some of the velocity vector was downrange, since the
}craft was significantly rotated in normal flight path by this
}time, at 73 seconds. I don't know by how much. Let us estimate
}it cannot have been tilted by more than 45 degrees (thinking back
}to the TV pictures), so that at least 71% of the 550 m/sec, or
}390 m/sec, was along the upward vector. Then one can use the
}same equation 1 above, remembering to change the sign so drag and
}gravity are now acting in the same direction, to estimate how
}long it takes the Challenger cabin to go up, stop, then fall
}back.
}
}The answer is, that with these parameters, the cabin continues
}from 46,000 to 58,500 feet (!) before it stops going upward,
}after the explosion. This takes an additional 26 seconds.
}That's a long coast, but the air is thin, and the thing is moving
}fast. Christa got closer to space than we thought she did.
}
}To fall back from V (upward) = 0 at 58,500 ft, takes 129 seconds,
}or 2.16 minutes. This may seem surprising as being only 16
}seconds longer than from 46,000 ft, but due to thinner air, the
}model shows the cabin actually reaches a maximal terminal 465 mph
}on the return fall this time, although the impact velocity is, of
}course, still the same 204 mph. Overall, the time from explosion
}to sea-impact is 155 sec, or 2.58 minutes.
Greg D. Moore
"Steven B. Harris" wrote:
>
>
> A followup on the discussion of terminal velocity and the
> Challenger disaster.
<Snipped>
> Some details in the Jensen book help, and some don't, and some
> I don't know what to think of. Two months after the disaster
> when the crew cabin was found, and later when several of the
> recovered crew 3-min oxygen water-egress cylinders were found to
> be 3/4 to 7/8 empty, there was a press briefing about the now
> certainty that some of the crew had survived the explosion, and
> been conscious and functional for at least long enough for one
> guy to turn on the pilot's oxygen bottle, from the position
> behind him.
One major correction. These bottles were bottled AIR, not pure oxygen,
so in reality they would have had little to no affect on conciousness.
<snipped>
>
> I've had some people tell me that the explosion of Challenger
> wasn't really an explosion in the ordinary sense, but only a
> controlled breakup and hydrogen/cryogen cloud and flair.
Well, the definition in question here is the speed of the wavefront of
the chemical interaction (i.e. is it expanding faster than the speed of
sound (explosion) or not (conflageration)). That is the latter case.
Tom
}
}
} A followup on the discussion of terminal velocity and the
} Challenger disaster.
} Still curious about the aerodynamics of the Challenger loss, I
} found a book by Klaus Jensen titled _No Downlink_, which gives a
} few more details. The Jensen book actually gives a time from
} explosion to crew cabin impact of 2 minutes 45 seconds (2.75
} min), so my initial certainty that 2 minutes was an impossibly
} short time, seems confirmed. Unfortunately, Jensen does not say
} where HE gets the time. Just as unfortunately, the new time is
} actually now 15 seconds too long, and I cannot get my little
} terminal velocity simulator program to give me times longer than
} 2.5 minutes, unless I raise the angle of travel at breakup from
} 50 degrees to an unrealistic 80 degrees from horizontal. The
} last figure is unrealistic because we've all seen the tapes, and
} the craft is tilted far more than that-- fairly close to 45
} degrees. Also, the Jensen book mentions that it was 7 nautical
} miles up and 9 nautical miles downrange from the pad at the time
} of the explosion, which make it certain that it was going very
} far from straight upward, at that point.
Have you performed a 3D or 2D simulation? There is a slight reduction in
G-level from altitude. Also, since the earth curves away with horizontal
velocity exponent, if a flat-earth emulation is performed, you must
include a V-squared over radius upwards exponent. This must include the
approximately 400 fps horizontal earth rotational velocity.
} Again, the problem is that the estimated impact terminal
} velocity on the water at sea-level, also given in Jensen as 204
} mph, fixes the aerodynamics of the cabin pretty well, with a
} sectional density/drag coefficient of about 800 kg/m^2. That drag
} coefficient has to change substantially (to a much higher value)
} at higher V's and altitudes, to get the cabin down 15 seconds
} later than 2.5 minutes. One might think that 15 seconds here or
} there is easy to get, by fooling with a few parameters. Not so.
} As mentioned earlier, you have to fool with them a surprising
} amount to get 15 seconds. Enough that there are still effects
} here, evidently, which we're not taking account of.
Ballistic coefficient changes with velocity. There is a rather sharp
peak at mach-1. Perhaps this slowed down the fall to terminal at a
higher altitude than with a straight-line coefficient.
Here's a snippet of MSExcel Macro code from a Boosted Dart routine that
I use:
Function MachCorrect(M As Double, Sharp As Boolean) As Double
Dim Correct As Double
If Sharp Then
Select Case M
Case Is <= 0.8: Correct = 1
Case Is <= 1.05: Correct = 1 + 12.78 * (M - 0.8) * (M - 0.8)
Case Is <= 7.27: Correct = 1.27 + 0.53 * Exp(-5.2 * (M - 1.05))
Case Else: Correct = 1.27
End Select
Else
Select Case M
Case Is <= 0.8: Correct = 1
Case Is <= 1.2: Correct = 1 + 3.556208468 * Exp(1.1 * Log(M - 0.8))
Case Is <= 6.27: Correct = 2 + 0.3 * Exp(-5.75 * (M - 1.2))
Case Else: Correct = 2
End Select
End If
MachCorrect = Correct
End Function
Try applying this and see if it makes a difference. (For the shuttle use
False for "Sharp").
} On the other hand, some of Jensen's other details don't help.
} At T+75 seconds, just a second after the last fireball flash, as
} all the parts were coming out a the very beginning of their
} ballistic paths, the tower tracking data announcer gave his
} routine update tracking data for that point, including
} (supposedly) a velocity of 2,900 fps. Clearly, that cannot be
} correct. Several books of mine have mentioned that the craft hit
} mach 1 at 18,000 ft, and was nearly at mach 2 at the explosion.
} One source gives mach 1.92, which at that altitude (46,000 ft
} mach 1 = 295 m/sec) is 566 m/sec. Since 1,900 fps is 579 m/sec,
} I have to believe that the 2,900 fps is a misprint or mis-speak
} for 1,900 fps. The only other possibility is that the radar had
} been fooled by the faster explosion debris, and actually read out
} 2,900 fps.
Perchance the 2900 fps is geocentric and the 1900 fps is geodetic? I've
seen the NASA documents flip back and forth several times on this -
quoting 4200 fps and 5200 fps for the SRB Sep velocity.
} Most interestingly, the Jensen book notes that some of the
} debris from the explosion went as high as 117,000 ft on radar.
} If you model the necessary vertical velocity component of even
} something like a metal bolt with twice the sectional
} density/drag ratio as the cabin-- about the same as many bullets-
} - and ask how large it needs to be in order to make 117,000 ft
} from 46,000 ft, you get an interesting answer. It takes a total
} vertical velocity component of close to mach 3.5 (> 1000 m/sec)
} to do this. Since the craft was doing less than mach 1.4 in the
} upward direction at the time of breakup, you can see that some of
} the debris (like bolts and objects of not inconsequential size
} and mass) had to emerge with an *extra* velocity of better than
} mach 2, and only those that happened to emerge with that extra
} delta-V straight upward, might get to such heights. Jensen does
} not discuss the the implications of how such a thing has to
} happen, but so far as I can see, this is the only way it CAN
} happen.
Remember that the SRBs thrusted for quite a while before the Destruct
was hit. And since the destruct slices open the casing, the 600 psi
inside the case can probably blow chunks quite a bit higher.
Steven B. Harris
<moo...@greenms.com> writes:
}
}
}"Steven B. Harris" wrote:
}>
}>
}> A followup on the discussion of terminal velocity and the
}> Challenger disaster.
}
}> Some details in the Jensen book help, and some don't, and some
}> I don't know what to think of. Two months after the disaster
}> when the crew cabin was found, and later when several of the
}> recovered crew 3-min oxygen water-egress cylinders were found to
}> be 3/4 to 7/8 empty, there was a press briefing about the now
}> certainty that some of the crew had survived the explosion, and
}> been conscious and functional for at least long enough for one
}> guy to turn on the pilot's oxygen bottle, from the position
}> behind him.
}
oxygen,
}so in reality they would have had little to no affect on conciousness.
}<snipped>
Why would they fill them with air when oxygen would be just as easy
to put in, and provide more margin of safety and breathing time, even
in water? And surely turning on the bottle of the guy in front of you
is a preplanned procedure also if there is depressurization? In which
case it also would have had to be oxygen. Or are you saying Onizuka
and several other people were creative enough to try it, even in a new
situation nobody had ever thought of? And all think of it within a few
seconds?
}> I've had some people tell me that the explosion of Challenger
}> wasn't really an explosion in the ordinary sense, but only a
}> controlled breakup and hydrogen/cryogen cloud and flair.
}
}Well, the definition in question here is the speed of the wavefront of
}the chemical interaction (i.e. is it expanding faster than the speed
of
}sound (explosion) or not (conflageration)). That is the latter case.
I don't understand what you mean by the last sentence. The fireball
appears to have thrown debris at Mach 2 relative to the craft. So
explosion it would then have to be.
Jorge R. Frank
>
> Perchance the 2900 fps is geocentric and the 1900 fps is geodetic? I've
> seen the NASA documents flip back and forth several times on this -
> quoting 4200 fps and 5200 fps for the SRB Sep velocity.
Did you mean "inertial" versus "earth-fixed", instead of "geocentric"
versus "geodetic"? The former comparison would show a 1000 fps
difference due to Earth rotation; the latter would involve a relatively
minor correction for Earth shape.
--
JRF
Reply-to address spam-proofed - to reply by E-mail,
check "Organization" and think one step ahead of IBM.
Henry Spencer
Steven B. Harris <sbha...@ix.netcom.com> wrote:
> Why would they fill them with air when oxygen would be just as easy
>to put in, and provide more margin of safety and breathing time, even
>in water?
Because oxygen is more dangerous to handle and can create a fire hazard
(you're *exhaling* almost straight oxygen, remember, and it can build up
in a confined space). Pure oxygen is not used where air will do.
>And surely turning on the bottle of the guy in front of you
>is a preplanned procedure also if there is depressurization?
*There was no preplanned depressurization procedure.* Get it out of your
head. The life-support system was supposed to prevent that. That's why
they didn't have pressure suits!
>...Or are you saying Onizuka
>and several other people were creative enough to try it, even in a new
>situation nobody had ever thought of? And all think of it within a few
>seconds?
Good training, whether for astronauts or for more mundane piloting jobs,
tends to emphasize that *anything is better than nothing* -- when faced
with an emergency, DO SOMETHING. The odds are way better if you do
something than if you do nothing, or if you sit around trying to figure
out what's optimal.
In fact, this particular action accomplished little or nothing. But it
was still a sensible thing to try in the circumstances. When faced with
difficulty in breathing, turn on any available breathing help!
>}Well, the definition in question here is the speed of the wavefront of
>}the chemical interaction (i.e. is it expanding faster than the speed of
>}sound (explosion) or not (conflageration)). That is the latter case.
>
> I don't understand what you mean by the last sentence. The fireball
>appears to have thrown debris at Mach 2 relative to the craft. So
>explosion it would then have to be.
As I understand it, it's quite well established that it was not (in the
technical sense) an explosion. Your conclusion that debris was thrown
off at Mach 2 is based on very sketchy evidence.
--
The space program reminds me | Henry Spencer he...@spsystems.net
of a government agency. -Jim Baen | (aka he...@zoo.toronto.edu)
Steven B. Harris
writes:
>Tom wrote:
>>
>> Perchance the 2900 fps is geocentric and the 1900 fps is geodetic?
I've
>> seen the NASA documents flip back and forth several times on this -
>> quoting 4200 fps and 5200 fps for the SRB Sep velocity.
>
>versus "geodetic"? The former comparison would show a 1000 fps
>difference due to Earth rotation; the latter would involve a
relatively
>minor correction for Earth shape.
Except there's a little problem with all this. At the latitude of
Cape Canaveral (about 28 degrees N) the velocity boost due to Earth's
rotation should be about equatorial velocity * cos(28), which is more
like 1340 fps, not 1000 fps. So this doesn't appear to be a viable
answer.
Steven B. Harris
writes:
>In article <82o6s0$2rd$1...@nntp1.atl.mindspring.net>,
>Steven B. Harris <sbha...@ix.netcom.com> wrote:
>> Why would they fill them with air when oxygen would be just as
easy
>>to put in, and provide more margin of safety and breathing time, even
>>in water?
>
>Because oxygen is more dangerous to handle and can create a fire
hazard
>(you're *exhaling* almost straight oxygen, remember, and it can build
up
>in a confined space). Pure oxygen is not used where air will do.
Nonsense argument. If you breathe 20 L/min (a reasonable figure in
moderate activity, or even 30 L/min (enough for even a panicked escape
in water), then 3 minutes of gas is, at most, 100 liters. That is not
enough, even at pure O2, to build up anywhere in any shuttle space
enough to be dangerous. Unless perhaps you are suggesting someone
might be smoking inside their helmet. Suppose the upper flight deck is
2 m x 3 m x 3 m. That's 18,000 L, already containing 3780 L of pure
O2. 400 more L would raise the O2 % from 21% to 23%. Wow, call out
the fire team. And no, air would NOT "do" for a water escape. In such
a case with limited gas, and some forced rebreathing, you'd like all
the oxygen you can get.
>
>>And surely turning on the bottle of the guy in front of you
>>is a preplanned procedure also if there is depressurization?
>
>*There was no preplanned depressurization procedure.*
You have the official word on that, do you?
>Get it out of your
>head. The life-support system was supposed to prevent that. That's
>why they didn't have pressure suits!
There are many situations in which you don't need a pressure suit,
if you have oxygen. Between 15,000 and about 45,000 ft, for a
sea-level pressure adapted pilot, extra O2 is the difference between
life and death. Since there were a number of scenarios in which the
orbiter might have lost pressure in that zone, but remained intact, it
would have been perfectly sensible to include oxygen for everyone, for
time enough to get down to a better altitude. Just as they do on any
airliner (where they don't have pressure suits, either).
>
>>...Or are you saying Onizuka
>>and several other people were creative enough to try it, even in a
new
>>situation nobody had ever thought of? And all think of it within a
few
>>seconds?
>
>Good training, whether for astronauts or for more mundane piloting
jobs,
>tends to emphasize that *anything is better than nothing* -- when
faced
>with an emergency, DO SOMETHING. The odds are way better if you do
>something than if you do nothing, or if you sit around trying to
figure
>out what's optimal.
No such general statement can be made. Sometimes in an emergency,
which may or may not be only an apparent emergency, it's better to do
nothing (by which I mean, nothing extra) for a while, while you think.
If there were good general rules for what to do in emergencies, they
wouldn't be such emergencies. Tom Wolfe tells the story of the plane
which is forced to land without gear, and begins breaking up on the
runway. There are two tandem pilots, each of which is forced to chose
between equally bad odds of riding the plane in, or else ejecting at
low altitude. The guy behind decides to eject, the guy in front
decides to ride it in. Both survive. Later they find that the engine
has entered the rear of the cockpit, and would have killed the guy
behind, had he stayed put. The guy in front's canopy was jammed, and
ejecting would have killed him. Both made the correct survival
decision, as it happens, under identical situations, by shear luck.
But they could as easily have both made the opposite decision, and just
as well could both have been killed, since neither decision was made on
the basis of the critical information needed. No general rule can be
formlated for this kind of thing, except to hope Lady Luck is smiling
on you.
>
>In fact, this particular action accomplished little or nothing. But
it
>was still a sensible thing to try in the circumstances. When faced
with
>difficulty in breathing, turn on any available breathing help!
Depressurization does not ordinarily result in a tangible
difficulty in breathing. If these folks had only air, the sensible
thing to have done would have been to save it for when it might have
been useful, in the water. In case the craft was intact and water
landing was required (which they might not have been able to rule out
in those few seconds). If the thing is intact, you'd better hope the
pressure holds out, since air won't help you at 46,000 ft and rising.
If it's not intact, probably you'd rather black out, hey?
>
>>}Well, the definition in question here is the speed of the wavefront
of
>>}the chemical interaction (i.e. is it expanding faster than the speed
of
>>}sound (explosion) or not (conflageration)). That is the latter
case.
>>
>> I don't understand what you mean by the last sentence. The
fireball
>>appears to have thrown debris at Mach 2 relative to the craft. So
>>explosion it would then have to be.
>
>As I understand it, it's quite well established that it was not (in
the
>technical sense) an explosion. Your conclusion that debris was thrown
>off at Mach 2 is based on very sketchy evidence.
It's based on a statement in a book. How strong that evidence is, I
have no idea. *If* the statement is true, then the fact would be
strong evidence of an explosian somewhere, since the laws of physics do
not allow you to get to 117,000 ft ballistically from Mach 1.4 and
46,000 ft, without a terrific kick in the fanny.
Tom
Velocity of the Surface:
2 * PI * 6378140 / 86164.1 = 465.1013 meters/sec
in Feet per Second:
/ 0.3048 = 1525.923 ft/sec
At KSC's Lattitude:
* cos(28.6) = 1339.734 ft/sec
Now apply the shuttle vector to the earth vector:
Shuttle 53.823° V=1900 Vx=1121.533 Vy=1533.677
Surface 0.000° V=1339.734 Vx=1339.734 Vy= 0.000
Combined V=2900 Vx=2461.267 Vy=1533.677
V is SQRT(Vx^2+Vy^2).
I arrived at 53.823° by applying "Goal Seek" in Excel.
Steven B. Harris wrote:
>
> In <3851972A...@ibm-pc.org> "Jorge R. Frank" <jrf...@ibm-pc.org>
> writes:
> >
> >Tom wrote:
> >>
> >> Perchance the 2900 fps is geocentric and the 1900 fps is geodetic?
> I've
> >> seen the NASA documents flip back and forth several times on this -
> >> quoting 4200 fps and 5200 fps for the SRB Sep velocity.
> >
Steve Wachowski
> It's based on a statement in a book. How strong that evidence is, I
> have no idea. *If* the statement is true, then the fact would be
> strong evidence of an explosian somewhere, since the laws of physics do
> not allow you to get to 117,000 ft ballistically from Mach 1.4 and
> 46,000 ft, without a terrific kick in the fanny.
I've been a mechanical systems tech at KSC in the shuttle program since
1979. I might have the answer you're looking for. Challenger did indeed
receive a "kick in the fanny" This is from the the Roger's Commission
report, quoted from this link:
http://www.ksc.nasa.gov/shuttle/missions/51-l/mission-51-l.html
At 73.124 seconds,. a circumferential white vapor pattern
was observed blooming from the
side of the External Tank bottom dome. This was the
beginning of the structural failure of
hydrogen tank that culminated in the entire aft dome
dropping away. This released massive
amounts of liquid hydrogen from the tank and created a
sudden forward thrust of about 2.8
million pounds, pushing the hydrogen tank upward into the
intertank structure. At about the
same time, the rotating right Solid Rocket Booster impacted
the intertank structure and the
lower part of the liquid oxygen tank. These structures
failed at 73.137 seconds as evidenced
by the white vapors appearing in the intertank region.
Could this be the acceleration that will solve your equation dilemma?
As to why the air packs were filled with air rather than oxygen - go
back to the thinking of the early '80s. Right or wrong, the Shuttle was
thought of as a safe system. The astronauts launched in basically a
shirtsleeve environment. The orbiter life support system was capable of
compensating for quite a large breach in the pressure hull, at least
long enough to make an emergency landing. The thinking was backup
systems in the sense that you are talking about, i.e. the air packs were
not needed. The air packs were meant as a breathing aid primarily during
a launch pad emergency or a landing contingency that resulted in a
release of toxic commodities (tank rupture or leak, releasing: N204,
MMH, Ammonia, etc.). The air pack would maintain a positive air flow to
the helmet, creating a very slight positive pressure in the helmet. That
in turn prevented any nasty stuff from getting inside the helmet and
being inhaled. Pure oxygen in this potentially explosive environment
would not be a good idea. O2 can saturate a persons clothing, causing a
very dangerous situation.
We use an emergency egress unit in Orbiter processing here at KSC. It's
basically a clear, heavy vinyl hood with an elastic neck ring. An
aluminum high pressure air bottle is attached via a rubber hose. Theses
units are staged all over the OPF bays, in the crew module, payload bay,
aft compartment and where ever a hazardous operation may be ocurring. In
the event of an emergency you open the unit, turn the valve on, place
the bag over your head and leave the area. The units provide 5 or 10
minutes of breathable air, enough to get to a safe marshalling area.
--
Steve Wachowski
-------------------------------------------
The above opinions are mine and mine alone,
mainly because no one else would want them.
-------------------------------------------
H. McDaniel
[pure oxygen...]
> enough to be dangerous. Unless perhaps you are suggesting someone
> might be smoking inside their helmet. Suppose the upper flight deck is
Um hm, but what happens if a "minor" cabin fire occurs and involves any
part of an astronauts air supply or suit? Something very nasty. do you
think it's a safe bet that emergencies will not include onboard fires?
> the fire team. And no, air would NOT "do" for a water escape. In such
> a case with limited gas, and some forced rebreathing, you'd like all
> the oxygen you can get.
If the shuttle makes a water landing and you're still in what's left of
it I doubt the form of air supply will really matter to you.
[...]
> >with an emergency, DO SOMETHING. The odds are way better if you do
> No such general statement can be made. Sometimes in an emergency,
> which may or may not be only an apparent emergency, it's better to do
> nothing (by which I mean, nothing extra) for a while, while you think.
Yeah whatever. When a real emergency happens you are *thinking* and
*acting* quickly. One's perception of time is nothing like what it is
while sitting in an armchair removed from any real danger.
[..]
> as well could both have been killed, since neither decision was made on
> the basis of the critical information needed. No general rule can be
> formlated for this kind of thing, except to hope Lady Luck is smiling
Um, if you had trained for years on what to do under various scenarios
and suddenly found yourself under real emergency conditions you will
either freeze up or do precisiely what you trained to do in a split second.
> Depressurization does not ordinarily result in a tangible
> difficulty in breathing. If these folks had only air, the sensible
> thing to have done would have been to save it for when it might have
I believe that the astronauts onboard Challenger had a better clue about
what they should and shouldn't try than you do.
> It's based on a statement in a book. How strong that evidence is, I
> have no idea. *If* the statement is true, then the fact would be
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I guess this says it all.
-McDaniel
Steven B. Harris
}
}Actually, it works out perfectly.
}Velocity of the Surface:
}in Feet per Second:
} / 0.3048 =3D 1525.923 ft/sec
}At KSC's Lattitude:
} * cos(28.6) =3D 1339.734 ft/sec
}
}Now apply the shuttle vector to the earth vector:
}
}Surface 0.000=B0 V=3D1339.734 Vx=3D1339.734 Vy=3D 0.000
}Combined V=3D2900 Vx=3D2461.267 Vy=3D1533.677
}
}V is SQRT(Vx^2+Vy^2).
}
}I arrived at 53.823=B0 by applying "Goal Seek" in Excel.
}
}
}
}
}Steven B. Harris wrote:
}>=20
geodetic?
}> I've
}> >> seen the NASA documents flip back and forth several times on this
-
}> >> quoting 4200 fps and 5200 fps for the SRB Sep velocity.
}> >
"geocentric"
}> >versus "geodetic"? The former comparison would show a 1000 fps
}> >difference due to Earth rotation; the latter would involve a
}> relatively
}> >minor correction for Earth shape.
}> Except there's a little problem with all this. At the latitude of
}> Cape Canaveral (about 28 degrees N) the velocity boost due to
Earth's
}> rotation should be about equatorial velocity * cos(28), which is
more
}> like 1340 fps, not 1000 fps. So this doesn't appear to be a viable
}> answer.
Ah, I see. We assume that the added Earth's rotational 1340 fps
adds only to the Vx vector (naturally) and then compute what
Challenger's V angle has to be at V = 1900 fps, in order to add Vx =
1340 and give us an extra 1000 fps total in the V direction. Thus, if
Vx and Vy are the V components relative to the air, then:
2900^2 = (Vx+1340)^2 + Vy^2
1900^2 = Vx^2 + Vy^2
Eliminating Vy and solving for Vx gives Vx = 1121 fps
and theta is arccos (1121/1900) = 53.8 degrees.
Very nice, and I'll bet you're right! We have now inferred
Challenger's upward direction angle and V vector, from odd bits of
information bits here and there. Vy(air) = 1900 * sin 53.8 =~ 1534 fps
and Vx(air) is 1121 fps.
Steven B. Harris
writes:
>I believe that the astronauts onboard Challenger had a better clue
about
>what they should and shouldn't try than you do.
You can believe what ever you like. The shuttle, when intact, can
land in water, and those aboard survive. They had John Glenn
practicing water escapes for a good reason, not just because it amused
them.
On the other hand, nobody who knows anything about depressurization
thinks that breathing air in an unpresssurized helmet is going to do
you any good. Might as well be a whiff of limburgher.
H. McDaniel
>
> In <3853E96D...@wolfenet.com> "H. McDaniel" <ha...@wolfenet.COM>
> writes:
>
> >I believe that the astronauts onboard Challenger had a better clue
> about
> >what they should and shouldn't try than you do.
>
> You can believe what ever you like.
Perhaps future shuttle crews should fly with copies of your USENET postings
so that they might be able to improvise your "solutions" when disaster
strikes. Of course they'll need a time machine so as to pickup future
copies of your hindsight based "solutions".
> The shuttle, when intact, can
> land in water, and those aboard survive. They had John Glenn
> practicing water escapes for a good reason, not just because it amused
> them.
Anything can land "in water" provided there is sufficent energy to get
it to the water. I think if you put on a pressure suit, get into your
car and drive it into water off the highest bridge you can find you'll
have a better understanding of the difficulties involved. You'll
probably still believe that a space shuttle will remain intact after
magically hovering onto open sea, but that's find. We all must have our
fantasies.
-McDaniel
Tom Faber
>
>
> You can believe what ever you like. The shuttle, when intact, can
> land in water, and those aboard survive. They had John Glenn
> practicing water escapes for a good reason, not just because it amused
> them.
>
It's more like crash in water.
If the cargo bay is empty, the astronauts might survive.
If there's any sizable payload in there, it's gonna
come through the crew cabin.
--
Tom Faber
Don Sterner
>>about what they should and shouldn't try than you do.
>
>land in water, and those aboard survive. They had John Glenn
>practicing water escapes for a good reason, not just because it amused
>them.
It doesn't sound like you have a grasp of the probabilities of
surviving a contingency abort. They're somewhere between zip and
none.
Jorge R. Frank
>
> "Steven B. Harris" wrote:
> }
> } In <3853E96D...@wolfenet.com>
> } "H. McDaniel" <ha...@wolfenet.COM> writes:
> } >what they should and shouldn't try than you do.
> }
> } You can believe what ever you like.
>
> haji@MY_STATE_SUES_SPAMMERS.wolfenet.com writes:
> >
> >Perhaps future shuttle crews should fly with copies of your USENET postings
> >so that they might be able to improvise your "solutions" when disaster
> >strikes. Of course they'll need a time machine so as to pickup future
> >copies of your hindsight based "solutions".
>
> wrong with the procedures they had in place, NASA quietly added an
> escape system to the Space Shuttle to allow bailouts.
*Because* they accepted that a water landing was probably not
survivable. Mr. Harris was asserting that it *is*.
Jim Carr
}
} In <3853E96D...@wolfenet.com>
} "H. McDaniel" <ha...@wolfenet.COM> writes:
} >I believe that the astronauts onboard Challenger had a better clue about
} >what they should and shouldn't try than you do.
}
} You can believe what ever you like.
In article <38553D3E...@wolfenet.com>
haji@MY_STATE_SUES_SPAMMERS.wolfenet.com writes:
>
>Perhaps future shuttle crews should fly with copies of your USENET postings
>so that they might be able to improvise your "solutions" when disaster
>strikes. Of course they'll need a time machine so as to pickup future
>copies of your hindsight based "solutions".
You might notice that, after loudly saying that there was nothing
wrong with the procedures they had in place, NASA quietly added an
escape system to the Space Shuttle to allow bailouts.
--
James A. Carr <j...@scri.fsu.edu> | Commercial e-mail is _NOT_
http://www.scri.fsu.edu/~jac/ | desired to this or any address
Supercomputer Computations Res. Inst. | that resolves to my account
Florida State, Tallahassee FL 32306 | for any reason at any time.
Florian Stadler
>Steven B. Harris wrote:
>>
>>
>> You can believe what ever you like. The shuttle, when intact, can
>> land in water, and those aboard survive. They had John Glenn
>> practicing water escapes for a good reason, not just because it amused
>> them.
>>
>
>It's more like crash in water.
>If the cargo bay is empty, the astronauts might survive.
>If there's any sizable payload in there, it's gonna
>come through the crew cabin.
What about opening the payload bay doors, loosening the payload and
rolling the shuttle. That should make the payload drop out.
However IMHO if you are landing on water without too high waves you
will be able to slow down gently enough to avoid the payload crushing
the crew.
Flo
H. McDaniel
> >It's more like crash in water.
> >If the cargo bay is empty, the astronauts might survive.
> >If there's any sizable payload in there, it's gonna
> >come through the crew cabin.
>
> What about opening the payload bay doors, loosening the payload and
> rolling the shuttle. That should make the payload drop out.
Couple of problems: How dificult would it be to handle the sudden
weight change that would occur while flying an inverted glider?
Getting the shuttle sideways or buttocks forward isn't really an
option (though it might work in a video game.) Would the not so
areodynamic payload collide with shuttle control surfaces leading
to some underisable result? Would the cagor bay doors close? When
they don't close how much more complicated will the flight
characterisitcs of the shuttle be?
As to landing on the water: I'd bet you the shuttle would break up
but maybe if the pilot prays a lot it won't. At any rate if I were
an astronaut I'd ask the pilot to let me parachute out and watch
his landing attempt from a safe distance.
-McDaniel
Ian Stirling
>Florian Stadler wrote:
>>
>> On Tue, 14 Dec 1999 14:31:31 -0500, Tom Faber <t...@edai.com> wrote:
>> >It's more like crash in water.
>> >If the cargo bay is empty, the astronauts might survive.
>> >If there's any sizable payload in there, it's gonna
>> >come through the crew cabin.
>>
>> What about opening the payload bay doors, loosening the payload and
>> rolling the shuttle. That should make the payload drop out.
>Couple of problems: How dificult would it be to handle the sudden
>weight change that would occur while flying an inverted glider?
Doesn't matter, you just need pilots with the "Right Stuff"
I wonder if the payload bay doors will in fact open in flight, seems to
me, with any significant aero loading, they are likely to stall in one
or other position.
If the shuttle is in straight and level, the best solution would be
to add some sort of ejection pole, surely?
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
If it can't be expressed in figures, it is not science, it is opinion.
-- Robert A Heinlein.
Richard Schultz
: You might notice that, after loudly saying that there was nothing
: wrong with the procedures they had in place, NASA quietly added an
: escape system to the Space Shuttle to allow bailouts.
It's quite possible that they added the escape system for PR purposes
to show how much they care, in full knowledge that any emergency that
would call for the use of such an escape system would be over long
before the astronauts had a chance to use it.
-----
Richard Schultz sch...@mail.biu.ac.il
Department of Chemistry tel: 972-3-531-8065
Bar-Ilan University, Ramat-Gan, Israel fax: 972-3-535-1250
-----
"an optimist is a guy/ that has never had/ much experience"
Tom Faber
>
> Jim Carr (j...@ibms48.scri.fsu.edu) wrote:
>
> : You might notice that, after loudly saying that there was nothing
> : wrong with the procedures they had in place, NASA quietly added an
> : escape system to the Space Shuttle to allow bailouts.
>
> It's quite possible that they added the escape system for PR purposes
> to show how much they care, in full knowledge that any emergency that
> would call for the use of such an escape system would be over long
> before the astronauts had a chance to use it.
>
Re Jim Carr's comment - The escape pole wasn't "quietly" added.
It was talked about alot at the time (between 51-L and STS-26)
if you had been paying attention. AW&ST and other space publications
had articles on it and I saw film on the TV news of test jumps out
of aircraft.
Re Richard Schultz's comment - The escape pole was never intended
(nor implied) to be used during a Challenger type accident. It
is to be used if the orbiter is in controlled glide and cannot
reach a suitable airfield.
--
Tom Faber
Richard Schultz
: Richard Schultz wrote:
: > It's quite possible that they added the escape system for PR purposes
: > to show how much they care, in full knowledge that any emergency that
: > would call for the use of such an escape system would be over long
: > before the astronauts had a chance to use it.
: Re Richard Schultz's comment - The escape pole was never intended
: (nor implied) to be used during a Challenger type accident. It
: is to be used if the orbiter is in controlled glide and cannot
: reach a suitable airfield.
I had known that the escape hatch wasn't intended for a Challenger type
accident; I had thought that it was for launchpad emergencies, if
anything. Thank you for the more accurate information.
-----
Richard Schultz sch...@mail.biu.ac.il
Department of Chemistry tel: 972-3-531-8065
Bar-Ilan University, Ramat-Gan, Israel fax: 972-3-535-1250
-----
"I've lost my harmonica, Albert."
Jim Carr
|
| "Steven B. Harris" wrote:
| }
| } "H. McDaniel" <ha...@wolfenet.COM> writes:
| } >I believe that the astronauts onboard Challenger had a better clue about
| } >what they should and shouldn't try than you do.
| }
|
| haji@MY_STATE_SUES_SPAMMERS.wolfenet.com writes:
| >
| >Perhaps future shuttle crews should fly with copies of your USENET postings
| >so that they might be able to improvise your "solutions" when disaster
| >strikes. Of course they'll need a time machine so as to pickup future
| >copies of your hindsight based "solutions".
|
| wrong with the procedures they had in place, NASA quietly added an
| escape system to the Space Shuttle to allow bailouts.
In article <38570529...@ibm-pc.org>
jrf...@ibm-pc.org writes:
>
>*Because* they accepted that a water landing was probably not
>survivable. Mr. Harris was asserting that it *is*.
I was not commenting on what he had to say, only observing that the
rationales given for various decisions rarely match up with reality.
Did the shuttle suddenly become unable to land in the water after
the Challenger problem? Or did NASA finally listen to its pilots
and drop the not-invented-here syndrome?
Terrell Miller
>
>What about opening the payload bay doors, loosening the payload and
>rolling the shuttle. That should make the payload drop out.
How you going to loosen the payload? Minor detail...
>However IMHO if you are landing on water without too high waves you
>will be able to slow down gently enough to avoid the payload crushing
>the crew.
I wonder if NASA or Rockwell ever did sims of this, I'm sure they'd have to.
I just can't see an orbiter holding together once it hits the first wave.
Terrell Miller
Ian Stirling wrote in message
<945432782.4454.0...@news.demon.co.uk>...
>
>If the shuttle is in straight and level, the best solution would be
>to add some sort of ejection pole, surely?
I remember after Challenger they showed pix of the astronauts testing this.
They blow the side hatch, extend a pole that's in the middeck, attach
parachute harnesses, and jump. All this requires a lot of advanced notice
(takes time to assemble the pole and hook up, not to mention muster the
crew) and a fairly steady flight regime. In which case, why would they need
to eject anyway, unless the landing gear was damaged or something.
Tom Faber
>
> Tom Faber (t...@edai.com) wrote:
>
> : Re Richard Schultz's comment - The escape pole was never intended
> : (nor implied) to be used during a Challenger type accident. It
> : is to be used if the orbiter is in controlled glide and cannot
> : reach a suitable airfield.
>
> I had known that the escape hatch wasn't intended for a Challenger type
> accident; I had thought that it was for launchpad emergencies, if
> anything. Thank you for the more accurate information.
>
We may be talking about two different things here. Since the
beginning of the Shuttle program there has been an escape
system that the crew could use if they had to quickly evacuate
the orbiter on the pad. They would exit thru the side hatch and
use a basket and slide-wire system to get to the ground quickly
and get into an armoured personnel carrier parked nearby and drive
away.
After the Challenger accident, a means of exiting an orbiter
that is in controlled glide but can't reach a suitable airfield
was added. This involved blowing the side hatch and then using
the slide pole for the crew to jump out without hitting the wing,
and parachuting to the ground/water.
This was added because it was decided that a water landing
(especially if any sizeable payload is in the cargo bay) is
probably not survivable.
--
Tom Faber
Greg D. Moore
The pole is in place, it simply needs to be slid out the open hatch. I
believe the total time to evacuate is under 90 seconds. (Though I'd
question if it's really possible for the the CMDR and Pilot to get out
since in many scenario's they'd probably be busy keeping the shuttle in
the controled glide.
Henry Spencer
Greg D. Moore <moo...@greenms.com> wrote:
> The pole is in place, it simply needs to be slid out the open hatch.
Well, it doesn't just slide out, it also telescopes out to full length.
But yes, it's already more or less in position.
>I believe the total time to evacuate is under 90 seconds. (Though I'd
>question if it's really possible for the the CMDR and Pilot to get out
>since in many scenario's they'd probably be busy keeping the shuttle in
>the controled glide.
The bailout-system modifications included a bailout mode in the autopilot,
to make it possible to hold a suitable glide with nobody at the controls.
DMeriman
>>
>> Ian Stirling wrote in message
>> <945432782.4454.0...@news.demon.co.uk>...
>> >
>> >If the shuttle is in straight and level, the best solution would be
>> >to add some sort of ejection pole, surely?
>>
>> I remember after Challenger they showed pix of the astronauts testing this.
>> They blow the side hatch, extend a pole that's in the middeck, attach
>> parachute harnesses, and jump. All this requires a lot of advanced notice
>> (takes time to assemble the pole and hook up, not to mention muster the
>> crew) and a fairly steady flight regime. In which case, why would they need
>> to eject anyway, unless the landing gear was damaged or something.
>
>
The Shuttle escape system has the same utility as the buoyant ascent escape
methode to get crewmen to the surface from a sunken submarine - zero! Just
something for the home-folk to feel better about. The Shuttle continues to be a
death-trap during a 'catastrophic event'.
David D. Merriman, Jr.
r/c submarines, 'the only way to fly!'
"Barns! Cargrave!... Come back here!!!"
Henry Spencer
DMeriman <dmer...@aol.com> wrote:
>The Shuttle escape system has the same utility as the buoyant ascent escape
>methode to get crewmen to the surface from a sunken submarine - zero! Just
>something for the home-folk to feel better about. The Shuttle continues to be a
>death-trap during a 'catastrophic event'.
Uh, who ever said otherwise? The bail-out system was NEVER ADVERTISED as
an answer to "catastrophic events". It is there solely and only because,
as the Rogers Commission pointed out, the orbiter is unlikely to survive
either a ditching or a belly landing. There is a class of emergencies in
which the orbiter is in stable gliding flight but cannot reach a runway --
for example, many multiple-engine-out cases end that way -- and this case
is unsurvivable without some kind of bail-out system. To quote the
Commission report (emphasis added):
The Commission recommends that NASA make all efforts to provide
a crew escape system for use *during controlled gliding flight*.
The Commission agreed with assessments by Bob Crippen and other astronauts
that there is *no* escape system which could reasonably be retrofitted to
the shuttle that would have saved the 51L crew.
Tom Faber
>
>
> The Shuttle escape system has the same utility as the buoyant ascent escape
> methode to get crewmen to the surface from a sunken submarine - zero! Just
> something for the home-folk to feel better about. The Shuttle continues to be a
> death-trap during a 'catastrophic event'.
>
I don't know how many times this has to be said:
The Shuttle bailout pole *isn't* intended to be
used for a catastrophic event.
It is intended, and has always been intended, to
be used in the event that an *intact* orbiter
in controlled glide can't reach a suitable airfield.
Period.
--
Tom Faber
Greg D. Moore
Henry Spencer wrote:
>
> In article <3870A3B3...@greenms.com>,
> Greg D. Moore <moo...@greenms.com> wrote:
> > The pole is in place, it simply needs to be slid out the open hatch.
>
> Well, it doesn't just slide out, it also telescopes out to full length.
> But yes, it's already more or less in position.
>
> >I believe the total time to evacuate is under 90 seconds. (Though I'd
> >question if it's really possible for the the CMDR and Pilot to get out
> >since in many scenario's they'd probably be busy keeping the shuttle in
> >the controled glide.
>
> The bailout-system modifications included a bailout mode in the autopilot,
> to make it possible to hold a suitable glide with nobody at the controls.
Fair enough. I wasn't clear. I was partly assuming that some of the
scenarios that may require ditching (say a hole burned into the wing)
might be so "unusual" that the software wouldn't be able to cope.
DMeriman
type events.
Derek Lyons
>The Shuttle escape system has the same utility as the buoyant ascent escape
>methode to get crewmen to the surface from a sunken submarine - zero! Just
>something for the home-folk to feel better about.
Hmmm.... The crew of the USS Tang at a minimum would disagree with
you. As well might the crew of several U-Boats sunk in Norwegian
waters. (ISTR at least one Brit boat as well...)
Steinke Hoods & etc are not perfect, but they are a *damm* sight
better than nothing.
Derek L.
------------------------------
Proprietor, Interim Books http://www.interimbooks.com
USS Henry L. Stimson homepage http://www.hurricane.net/~elde/655.html
Derek on Books http://www.interimbooks.com/derek/books/
------------------------------
Henry Spencer
DMeriman <dmer...@aol.com> wrote:
>Yet the 'bail-out' pole is sold (through the press) as the answer to Challenger
>type events.
No, the bail-out system is sold *by* the press as the answer to such
events, and that's their mistake. NASA doesn't say that.
Tom Faber
>
> Yet the 'bail-out' pole is sold (through the press) as the answer to Challenger
> type events.
>
When was that said through the press?
I've *never* heard anybody within NASA say the bailout system is
for use in that type of accident, and I've followed the Shuttle
program since it's beginnings. If some member of the press said
the bailout system is for use in that type of accident then that
member of the press doesn't know what they are talking about.
--
Tom Faber