acourt@BBN-VAX.ARPA ("Anthony J. Courtemanche") (02/04/86)
Although, as said earlier, it is doubtful whether the Shuttle could survive the deceleration of landing in the Atlantic, it is interesting to think about what the possible abort scenarios would entail. First, the media (& NASA photos) say that an abnormal plume eminated from the right SRB at least 15 seconds before the deadly external tank explosion. Is 15 seconds long enough to initiate an abort? At least three events would have to occur: 1) Ground crew interprets visual data, determines that the situation is deadly, and tells shuttle commander to abort. My guess is that this could take up a very significant part of 15 seconds. 2) Shuttle commander receives abort message and initiates abort sequence. I don't know how well the Shuttle pilots are trained to respond to such frightening news, but I would guess that the commander wouldn't freeze for more than say 0.5 seconds. Now as far as initiating the abort sequence, I've heard that this consists of pulling a lever and pressing a button. If this is true, I would guess that this could be done within a second. 3) Shuttle breaks away from external tank soon enough to survive the explosion. I have no idea how different the trajectories of the shuttle and the ET/SRB assembly can be made to be during an abort. I would guess that in any case, to survive the explosion, the ET/SRB-Shuttle separation would have to be at least a thousand feet or so. Even at this distance, any shock wave effects could still be dangerous. Now, even if all the above could be done in time and the Shuttle remain intact, could the Shuttle obtain an aerodynamic trajectory before hitting the ocean? I don't remember the altitude that the Shuttle was at when the explosion happened, but the Shuttle was on it's back and this is not a graceful way to start gliding. Also, correct me if I'm wrong, but I don't think that any sort of engines are available to help re-orient the orbiter during the abort (could the de-orbit engines be used?). Hence, only the control surfaces on the Shuttle could be used to establish a gliding (as opposed to plummeting) trajectory. To me, it seems doubtful that an abort could have succeeded in saving the lives of 7 astronauts or the orbiter. I am welcome to have any comments on my above reasoning, and I'd like to know if, in light of what I've said above, there was any reasonable chance for a safe abort. --Anthony Courtemanche ac%mit-oz@mit-mc
weemba@brahms.BERKELEY.EDU (Matthew P. Wiener) (02/04/86)
In article <8602032227.AA10998@s1-b.arpa> ac%mit-oz@MIT-MC.ARPA writes: >3) Shuttle breaks away from external tank soon enough to survive the >explosion. I have no idea how different the trajectories of the >shuttle and the ET/SRB assembly can be made to be during an abort. >I would guess that in any case, to survive the explosion, the >ET/SRB-Shuttle separation would have to be at least a thousand feet or >so. Even at this distance, any shock wave effects could still be >dangerous. If the explosion was caused by an SRB burning into the ET, as seems likely from the latest news, then presumably the SRBs would travel separately from the ET, and there would be no explosion. But I've read on the nets that the ejection cannot occur until the SRBs have burned out anyway, so the question is moot. ucbvax!brahms!weemba Matthew P Wiener/UCB Math Dept/Berkeley CA 94720
steve@bambi.UUCP (Steve Miller) (02/05/86)
> 1) Ground crew interprets visual data, determines that the situation is > deadly, and tells shuttle commander to abort. My guess is that this > could take up a very significant part of 15 seconds. Navy pilots launching from aircraft carriers are trained to respond instantly to the command "Punch out" from the air boss. I have seen films of pilots being given this command. The air boss has maybe one to three seconds immediately after launch to identify an emergency, and then give the command. > Now, even if all the above could be done in time and the Shuttle remain > intact, could the Shuttle obtain an aerodynamic trajectory before > hitting the ocean? Challenger was about nine miles up and moving nearly 2000 mph. At this speed, even the thin air at that height provides adequate control for aerodynamic surfaces to orient a large aircraft. -Steve Miller ihnp4!bambi!steve
henry@utzoo.UUCP (Henry Spencer) (02/05/86)
> To me, it seems doubtful that an abort could have succeeded in saving > the lives of 7 astronauts or the orbiter. I believe NASA has said that the split-off-from-tank-and-SRBs-and-ditch abort possibility, which theoretically existed on the first few test flights but hasn't been included in recent missions, would be "better than certain death, but not by much". -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
allen@mmm.UUCP (Kurt Allen) (02/06/86)
In article <8602032227.AA10998@s1-b.arpa> ac%mit-oz@MIT-MC.ARPA writes: >respond to such frightening news, but I would guess that the commander >wouldn't freeze for more than say 0.5 seconds. Now as far as This type of action is exactly what is practised time and time again in the simulaters. I really doubt that the pilot in command is going to 'freeze'. Test pilots are trained to react. Listen to cockpit tapes of planes going down and listen to what the crew say while the plane is destroying itself. >could the Shuttle obtain an aerodynamic trajectory before >hitting the ocean? I don't remember the altitude that the Shuttle was >at when the explosion happened, but the Shuttle was on it's back and >this is not a graceful way to start gliding. Also, correct me if I'm >wrong, but I don't think that any sort of engines are available to help >re-orient the orbiter during the abort (could the de-orbit engines be used?). >Hence, only the control surfaces on the Shuttle could be used to >establish a gliding (as opposed to plummeting) trajectory. The shuttle was appx 50,000 feet in the air, and traveling at over 2000 miles an hour. A large part of this vecter was straight up, so their altitude would continue to increase after seperation from the srb's and main tank. They would probably require the use of the attitude rockets to point the shuttle in the right direction, as at 50,000+ feet the control surfaces will not have a great deal of effectiveness. Given that I think that it would have been able to enter a glide. They might have trouble dumping onboard fuel before impact, but they should have several minutes before impacting the ocean. Since the landing speed of the shuttle is (I think) around 150 - 200 kts (fairly high for a plane that size ) the impact with the ocean could be a problem, but with a carefull pilot the shuttle should be able to maintain structural integrity. Whether the shuttle would float afterwords, or even be able to skip on top of the water after impact instead of diving into the water and 'flying' down to a depth of several hundred feet below the surface (as happens to many fighter aircraft) I don't know. All in all I don't think their chances would have been too bad. But the shuttle would probably have needed to be mostly rebuilt, or even scrapped. Aircraft that have been overstressed are often never quite the same afterword, and NASA probably doesnt have any mechanism for getting a shuttle out of the water and onto a ship quickly. The electronics would surely suffer. -- Kurt W. Allen 3M Center ihnp4!mmm!allen
space@ucbvax.UUCP (02/06/86)
Speaking from a position of relative ignorance, I would like to raise the following points about shuttle aborts: The SRBs cannot be turned off, therefore the suttle would have to survive the exhaust. Suppose the shuttle decelerates from drag at 1G, and the SRBs can power the tank away at 3G. Then at least 4 seconds are required to let the shuttle reach your 1000 foot separation (which I think is generous, but not *safe*. There should be no trouble attaining proper glide characteristics aerodynamically. Being miles up, at Mach 3, an intact shuttle could do 'loops', or whatever. Getting to a specific point is made more difficult by time consumed in rolling over, etc, but I suspect that only a very limited window avoids the ocean. Survival in a ditching may be determined by the payload (better glide if nothing else). I see lots of problems in trying to empty the cargo bay. To detach from the ET without igniting fuel will require sealing the lines at the ET, waiting for them to drain, and then blowing the shuttle free. This may require a significant amount of your remaining allotment.
hester@ICSE.UCI.EDU (Jim Hester) (02/12/86)
Re time to abort: if the ground crew decides it should be done, they could do it themselves, while (perhaps) simultaneously advising the shuttle commander (he should be able to figure it out for himself pretty quickly, though). I'm not advocating stepping on his toes this way, but it is one possibility that could save a lot of the delays you mentioned. As for the physical problems of getting the shuttle far enough away to survive the explosion, that seems a more difficult problem. One thing to remember is that the shuttle is traveling with a fair speed relative to the air around it so it's manuevering flaps would have a reasonable effect. Assuming part of the abort program is to set everything the shuttle has on traveling "up" (relative to the shuttle; i.e., away from the booster), I would expect the shuttle to seperate quickly (recall, the separation speed is is better than linear, since the shuttle will continue to deviate it's course away). I don't know if it is good enough in this case, but consider that a bit academic. The point is, the shuttle should be ready for the fastest ditch it can make within the engineering and cost constraints it has. We cannot predict the time needed to escape in future mishaps; we can only be ready for the shortest time we can handle. Saying "It would have worked" or "it would not have worked" on this particular emergency is certainly of interest, but we must remember that a conclusion of "it would not have worked" on this mission is no reason to not prepare for it in the future. Re time needed after seperation for shuttle to attain aerodynamic trajectory: Same point: The shuttle already has velocity relative to the air around it, so the fact that it is "upside down" relative to the Earth is not major. As long as it is travelling "forward" through the air it can manuever, and thus can roll to orient with the earth. I would expect an abort operation to entail: Everything on the shuttle automatically set to make the shuttle go "up" relative to itself, to get away from the booster fastest. At some point, the shuttle will be traveling roughly perpendicular to the booster, parallel to Earth's surface, and upside-down relative to Earth. If it has enough velocity left, it can roll and end up gliding. If not, it can continue turning "up", or, towards the Earth in a dive to get back enough speed to roll and begin a glide. The altitude of ditching does not seem so important to me as the velocity when ditching (of course, they are directly related). Also remember that, while ditching, the shuttle will continue to gain altitude until it is traveling parallel to the surface. I'm not a pilot, but everything I've heard leads me to believe that the good ones don't care much what their orientation is relative to Earth, as long as they have control of their ship, which is dependant only on working controls and instruments, and forward motion relative to the air around them. Of course, the shuttle is no stunt plane, but then the pilot is presumably one of the best. There is always a time early enough in the liftoff where the shuttle would stall before being able to get into a controled dive, but I suspect this case was not in that category: the shuttle was moving relatively fast. As an afterthought, if the shuttle is equiped with a less efficient passenger ejection system, all the abort needs to do is get the shuttle away from the bomb to give time for the passengers to get out of the shuttle before it crashes. I have my doubts about this one, but it might be worth looking into if they determine that the shuttle can't be safely landed after an abort. Again, I am neither an engineer nor a pilot, but I would not rule out the possibility of mechanically quick aborts, and I tend to think that the shuttle could usually be adequately handled in the case of an abort, unless it was quite early in the liftoff. I am by no means sure of any of this, I am answering more because I am disturbed that you conclude the opposite on the basis of speculations and opinions which appear to be no better informed than mine, nor more complete. Neither of us has given arguments anywhere near conclusive, so why don't we just continue to point out this-and-that pro and con and leave asserting final conclusions to those who think they are qualified?
space@ucbvax.UUCP (02/15/86)
Your article makes good sense to me. It's important to get back to land (to save the orbiter), so while a roll maneuver would quickly get the shuttle right-side-up, a long dive & loop would get it headed back to the Cape. Unfortunately, it has a lot of horizontal speed away from land; the loop might be inefficient in converting that to the reverse direction. What we SHOULD have done is launched the thing from Texas or La to pass OVER the Cape, so that the orbiter could easily glide straight to Canaveral after an abort. Hindsight sure is 20-20.... mike k
kwan@smeagol.UUCP (Richard Kwan) (02/20/86)
> What we SHOULD have done is launched the thing from Texas > or La to pass OVER the Cape, so that the orbiter could easily glide > straight to Canaveral after an abort. > Hindsight sure is 20-20.... mike k Texas or La? Louisiana? I hope that wasn't Los Angeles. ^^ -- Rick Kwan JPL Spacecraft Data Systems -------------------------------------------------------------------- "...jumpin' into hyperspace ain't like dustin' crops, boy." H. Solo --------------------------------------------------------------------
adolph@ssc-vax.UUCP (Mark Adolph) (02/22/86)
*** YOUR MESSAGE ***
According to "The Shuttle Operators Manual," any shuttle abort involves
a firing of the OMS engines, both to maintain altitude and airspeed and
to dsipose of dangerous tetrazine fuel. It seems to me that with the
aeordynamic control due to an airspeed over mach 1 plus the extra push
from the OMS engines, an abort should be possible during the boost phase
of flight. The only reason I can think of that it wouldn't be possible
is that the g-forces during the maneuver are outside the limitations of
the orbiter's structural strength, much like one shouldn't do outside
loops in a DC-10.
More reliable information about this would be much appreciated.
--
-- Mark A.
...{uw-beaver|fluke}!ssc-vax!adolph
"1 + 1 = 1, for sufficiently small values of 1..."bl@hplabsb.UUCP (Bruce T. Lowerre) (02/25/86)
> What we SHOULD have done is launched the thing from Texas > or La to pass OVER the Cape, so that the orbiter could easily glide > straight to Canaveral after an abort. > Hindsight sure is 20-20.... mike k Yes, that would also make it easier to recover all the debris. The large wing section would be removed from the school building in Dallas, the lower fuselage section from the housing development in Phoenix, the left SRB pieces from the slum in Mexico, and the right SRB from downtown Flagstaff.
paul@axiom.UUCP (Paul O`Shaughnessy) (02/26/86)
NASA and its contractors have consistently maintained that a ditching of the shuttle during the SRB boost phase of the flight is impossible to perform survivably. The most believable reasons which I have heard on the net and in the media go something like this: Very early in the launch, detatching and landing the shuttle is impossible simply because there is insufficient altitiude. By the time there is sufficient altitude for anything other that a nosedive, the spacecraft is travelling at several times the speed of sound through atmosphere which is still quite dense. If the shuttle were to detach from the fuel tank at this point, it would not veer away gracefully as we might imagine, but would flip over backwards and its wings (at least) would be torn up by the excessive aerodynamic force. I don't think that such a detatchment is possible until the spacecraft is quite high, which is after the SRB's are jettisoned. I've also read that jettisoning the SRB's while they're still burning full force is near impossible because their exhaust would explode the fuel tank or frazzle the shuttle as they raced ahead of the spacecraft. Is this true? I certainly don't trust everything I read or hear, and I post this not as truth but as a concentrate of recent publications. Confirmations or corrections are appreciated. Also, could any of these ditching modes be made safe? ------------ Paul O'Shaughnessy Axiom Technology Corp. Newton, Massachusetts 'Home of the AT100'
allen@mmm.UUCP (Kurt Allen) (02/28/86)
In article <172@axiom.UUCP> paul@axiom.UUCP (Paul O`Shaughnessy) writes: >NASA and its contractors have consistently maintained that a ditching >of the shuttle during the SRB boost phase of the flight is impossible >to perform survivably. There are a few more scenarios that I have been made aware of recently, that would preclude shuttle survival in case of a SRB failure. These are 1) If one of the SRB's fails to ignite at launch. As it is impossible to stop the other SRB the shuttle would pinwheel uncontrollably, with no possibility of survival. 2) The shuttle lands at 190 knots. It is not expected to maintain structural integrity ditching in the ocean at this speed. -- Kurt W. Allen 3M Center ihnp4!mmm!allen