Can the disaster be avoided if.........

hk8900 · Feb 1, 2006

The Challenger accident happen because the SRB failed I am thinking that the accident could have been avoided If the SRB can be jettisoned mid-flight in case of emegency Then, if onboard sensor record serious abnormality in SRB that will threaten the safety of astronauts, the computer can perform an emegent function to jettison the failed SRB to prevent explosion of the External Tank due to fire in failed SRB. After that, the shuttle can perform emergency suborbital flight with the the fuel in the ET and main engine (without SRB, the shuttle cannot reach min. velocity to reach LEO) the shuttle will be able to reenter the atmosphere and land safely. Actually, this (emegency suborbital flight) had happened on the Russian Soyuz (detail see http://en.wikipedia.org/wiki/Soyuz_18a)

rfoshaug · Feb 1, 2006

When the solid rocket fuel of the SRB's are lit, there's no way to put them out. So if you jettison the SRB's, they would still have all that thrust, but no shuttle/ET to use all that thrust. So they would rapidly accelerate along the sides of the ET, and very soon the ET and orbiter would be in the middle of the plume from the SRB's - not a survivable scenario. Of course, this would not be so much a problem if you could somehow tilt the SRB's outward away from the tank and orbiter. But that would have required very powerful thrusters on the top of the SRB's that would again leave the tank in the way of their plume (this is how the boosters separate during normal staging, but those thrusters are much less powerful than those that would be required for clean separation if the SRB's still produced thrust). And it wouldn't help any if you released the upper SRB/ET attachment point first in order to let the SRB's rotate outward around the lower attachment before releasing completely. The thrust from the SRB's would make it rotate towards the tank instead of away from it (actually in the Challenger accident, the situation really got out of hand once the lower attachment point was severed, so the booster rotated around the upper attachment point and into the top of the tank, before rotating back and hitting the side/bottom of the tank). The main problem with the SRB's is that once you light them, they burn until fuel depletion and there's nothing anyone can do to stop them. This was the main point of those advocating the development of liquid rocket boosters, LRB's for the shuttle in the 1970's and 1980's. They would have been a lot larger, as liquid fuels can't be stored as densely as solid fuels, and they would have behaved differently, which would have required a complete re-certification of the entire shuttle system. The money to do this was never found. But the SRB's are quite reliable. In 114 shuttle flights, there have b <div class="Discussion_UserSignature"> ----------------------------------My minds have many opinions </div>

henryhallam · Feb 1, 2006

And at least during the early part of the ascent, the ET is still mostly full of fuel and oxidiser so it weighs considerably more than the thrust provided by the SSMEs can lift on their own.

vogon13 · Feb 1, 2006

Instantaneous decoupling of the stack during SRB burn will impart an enormous reaction load onto the ET and it will structurally fail instantly. Sudden cessation of acceleration is the same as a sudden decelleration, like hitting a wall. The failure of the ET in the Challenger accident (bottom of tank came off) instantly unloaded all the LH2 in the tank and the resulting impulse (thrust stayed (briefly) constant, mass of vehicle suddenly dropped drastically) reaction forces disrupted the orbiter. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

spacefire · Feb 1, 2006

can the Orbiter separate from the ET and SRBs using its flight controls and using the OMS engines and the SSMEs while there is still fuel in the lines? <div class="Discussion_UserSignature"> http://asteroid-invasion.blogspot.comhttp://www.solvengineer.com/asteroid-invasion.html </div>

hk8900 · Feb 2, 2006

"But the SRB's are quite reliable. In 114 shuttle flights, there have been used 228 SRB's, and just one has failed. And after the post-Challenger redesign, they're even safer. Right now it seems that the SRB's are not the Achilles heel of the shuttle system - the thermal protection system is." Oh, a good point The SRB haven't had any problems since 1986, 20years of safe flight........ Now, the major concern is the Thermal protection system I know that NASA is going to get rid of those troublesome foam on the ET However, will ice accumulate on the surface of the ET and cause new problems if the foam is removed? Installing that many heaters is a difficult job. Ice will still fall down during launch and cause danger if this problem is not solved.

rfoshaug · Feb 2, 2006

I believe the new shuttle-derived heavy launch vehicle will have that orange foam still to avoid ice buildup, but it will be completely expendable since it will no longer have an orbiter that it must not hit. <div class="Discussion_UserSignature"> ----------------------------------My minds have many opinions </div>

henryhallam · Feb 2, 2006

I know that NASA is going to get rid of those troublesome foam on the ET However, will ice accumulate on the surface of the ET and cause new problems if the foam is removed? A cryogenic tank, especially one carrying liquid hydrogen, really needs some kind of insulation and foam will certainly still be around on the SDHLV ET. The primary purpose of insulation is not to prevent ice buildup! It is needed to keep the propellants cold so that they won't boil off and be wasted during countdown and ascent. Ice is really a secondary, though important, consideration. As rfoshaug said, ice and/or foam loss during ascent won't matter much for the SDHLV as there is no fragile Orbiter TPS (or anything fragile really) below the tank. The payload is on top, where it should be!

rocketman5000 · Feb 2, 2006

the boil off could be accounted for in designs of tanks and the tanks could be kept topped off till the last seconds before launch

CalliArcale · Feb 2, 2006

<blockquote>In reply to:<hr />A very good post on this issue. i just want to add that once the SRB is jettesoned there is no thrust vector control since the Shuttle orbiter does that commanding. The boosters would start to tumble as soon as they are jettesoned.<hr /></blockquote> I was watching my Challenger video yesterday. Seeing the SRBs winding path as they climbed out of the cloud of debris, completely uncontrolled, until range safety commanded their destruction.... *shivers* Yeah. There's no way to jettison them. The other problem, of course, is realizing that you *need* to jettison. It's all well and good to have a means of escape, but if you don't know there's a problem until it's too late, it's not going to matter. There were bad signs well before Challenger was destroyed, but nobody realized just how badly things were going until the ET ruptured at 73 seconds, and of course at that point it no longer mattered. <img src="/images/icons/frown.gif" /> No matter how fancy your escape system, it will be totally useless without a good, reliable way of detecting imminent disaster. And of course it's not always possible to predict every failure mode, so it becomes a real challenge trying to guess at what might go wrong. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

CalliArcale · Feb 2, 2006

And that was exactly my point, although ineptly explained. <img src="/images/icons/wink.gif" /> There were signs -- but not signs anybody could see or make use of in a mere 73 seconds. Even if they'd had a way of shutting down and ejecting the SRBs, they wouldn't have realized that they needed to until it was too late. Probably the best indication was the telemetry indicating a deviation in attitude between the two SRBs, but that was pretty late in the timeline. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

henryhallam · Feb 2, 2006

You seem to be confusing thrust with pressure. Thrust is often measured in pounds. The SRBs provide ~3 million pounds of thrust each. Pressure is often peasured in psia which is short for "pounds per square inch, absolute" (absolute rather than gauge pressure). The pressure inside the SRBs is certainly not millions of psia, otherwise the case would rip apart instantly! In fact the pressure does not need to be very high because the thrust is not caused by pressure forces, it is caused by the Newton's 3rd reaction to combustion products escaping through the nozzle at high velocity. I don't know where you got your figure from but it is completely incorrect. Maybe it's just possible that shuttle_guy who has worked on the STS program since its inception has some idea what he's talking about <img src="/images/icons/wink.gif" /> <img src="/images/icons/wink.gif" /> I'm afraid I really can't make sense of the last part of your post, perhaps you could rephrase?

henryhallam · Feb 2, 2006

Let's be very explicit here, are you trying to say that the operating pressure inside the SRB is in the millions of psi? Because that is provably false. It is not difficult to work out the hoop stress in the SRB chamber wall and compare that with the ultimate tensile stress of the steel casing - more than a few thousand psi and it WILL FAIL. If you actually read that explanation you quoted, you will see that the deLaval nozzle causes the pressure at the nozzle exit to reduce until it is very close to the atmospheric pressure (that is part of the whole purpose of a deLaval nozzle). Very little pressure difference = /> very small component of thrust comes from the pressure. Thrust comes from the exhaust velocity. If Shuttle_guy is a shuttle pilot, (or an engineer associated with the Shuttle program)....attempting to teach engineering ...I wouldn't ride with him. I have flown with Dave and would be glad to again. He has taught me many things about real-world engineering. Your remarks are baseless.

john_316 · Feb 2, 2006

Will we have to worry about this particular SRB issue in the future as the CEV will ride on top and if the SRB does have a problem we can then use the CEV escape system to accelerate away from the SRB? I don't know why we keep going over the Challenger issue. Its all in hindsight and the issue was fixed. Sometimes I wonder if this issue is going to be brought up again when the CEV launches? But its hard to say what people will say in 10 years.... <img src="/images/icons/smile.gif" />

danwoodard · Feb 2, 2006

Let me just inject one fact. Early in the Shuttle program a so-called zero-thrust system was designed for the SRB so it could be jettisoned before burnout. The system consisted of a large port near the nose of the rocket that could be blown open by a pyrotechnic charge. There would be some exhaust escaping forward but the internal pressure would rapidly drop until thrust went to zero and the booster separation rockets could be fired normally. The system was deleted because there were few contingencies where it would help. It seems doubtful there would have been time to fire it in the Challenger disaster. Which brings up a related point. If there is a contingency involving the SRB in a CEV launh, it's hard for me to see how anybody will have time to identify the problem and activate the escape system. I am not sure the often quoted figure of two successful launches per STS mission is valid, but if it is, we've had over 300 successful SSME launches with only one shutdown which did not affect the mission. After Challenger everyone said we should never launch people on solids because of their "sudden death" failure modes. How soon they forget.

scottb50 · Feb 2, 2006

It might be easier to redesign the Shuttle cockpit to carry 4-5 people and use the mid-deck area to house escape rockets. Eject the entire cockpit and use parachutes for landing, like the F-111. Possibly both Shuttle disasters could have been averted, Challenger for sure. <div class="Discussion_UserSignature"> </div>

scottb50 · Feb 2, 2006

I would think you could modify the cockpit, which is pretty much a stand alone structure to allow escape at pretty much any phase. Like you say how much payload you want to sacrifice. It does seem that with the ISS and that being the Shuttles only destination, the mid-deck is superfulous, they can't tough it out for a day or so? <div class="Discussion_UserSignature"> </div>

Swampcat · Feb 3, 2006

Not a specific reply to newsartist...anyone can jump in <img src="/images/icons/smile.gif" />. All this talk about failures in the SRBs...I mean, exactly what kind of failure would prevent the LES from doing its job and saving the crew? I'm somewhat familiar with solid rocket motors from my amateur rocketry experience and I know things can happen, but it seems to me it would take something really bizarre to cause a failure of the LES to do its job in the event of an SRB malfunction. The problem experienced with Challenger's SRB, IMHO, would not be enough and, besides, that problem has not reoccurred. In fact, are there any examples of a post-Challenger SRB having a problem of any sort? The only possible problem I see with the SRB is the G loads. If that can be mitigated then why all the concern over using the SRB as a CEV launcher? <div class="Discussion_UserSignature"> ------------------------------------------------------------------- "I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."Thomas Jefferson </div>

Swampcat · Feb 3, 2006

"I think the Challenger problem happened too fast for the LES to detect and fire. The system must have a positive indication to fire the LES and the positive failure indications came during the breakup. That was too late." Far be it from me to doubt you SG. I respect you too much for that. Maybe I didn't set the scenario properly. Let's suppose the particular SRB that caused the problem with Challenger had been launching a CEV instead. Isn't it likely that the breach would have given some indication of a problem? Was there enough of a leak to affect the trajectory? Remember, I'm not talking about an STS launch here, just a single stick with a CEV. Also, without the ET next to it, there is nothing for the leaking gases to impinge on so there would be no breakup as with Challenger. <div class="Discussion_UserSignature"> ------------------------------------------------------------------- "I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."Thomas Jefferson </div>

Swampcat · Feb 3, 2006

"I was referring to a Shuttle launch configuration." I figured that I hadn't explained the scenario very well. So it's back to my question...what could go so wrong with an SRB as a CEV launcher that would result in the LES not being able to save the crew? Anyone? I should probably start a new thread for this question. <div class="Discussion_UserSignature"> ------------------------------------------------------------------- "I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."Thomas Jefferson </div>

strandedonearth · Feb 3, 2006

SG: In the Challenger mishap, you stated the leak started at launch (black puffs of smoke) and quickly sealed itself, only to reopen later while passing through some wind shear. In a CLV scenario, if the leak was reopened due to wind shear, would there not be a miniscule drop in performnce (presumably not enough to affect the mission), as well as some lateral thrust (imparting unwanted pitch or yaw), which would require extra steering input? Wouldn't these be detectable, especially as the breach would (presumably) grow bigger the longer the breach leaked? My WAG is that the performance drop would not be enough to trigger the LES, but too much steering input required would. This is all assuming there was ever another such O-ring leak, which I doubt there would be.

Swampcat · Feb 3, 2006

"A very large fiel joint failure." OK, I can buy that. I've seen small solid motors blow up from failure of the motor casing or end closures, usually as a result of incorrect assembly. It happens pretty darned fast. I'm wondering if that has ever happened with an STS SRB...even in testing. <div class="Discussion_UserSignature"> ------------------------------------------------------------------- "I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."Thomas Jefferson </div>

drwayne · Feb 3, 2006

Note that a key factor in the Challenger leak was the rocking of the stack associated with the build up of SME thrust. A single stick vehicle won't be doing that. Wayne <div class="Discussion_UserSignature"> "1) Give no quarter; 2) Take no prisoners; 3) Sink everything." Admiral Jackie Fisher </div>

john_316 · Feb 4, 2006

I think you have a very good point here... I dont see the fireball in the sky and I could see the LES working and saving the crew in the event of an emergency abort. I imagine they will have some sensors to indicate launch failure and allow the crew to punch out. <img src="/images/icons/smile.gif" />

Swampcat · Feb 4, 2006

"A single stick vehicle won't be doing that." The reason I brought this up was to counter those who have expressed concerns about using the STS SRB as a CLV. As SG has pointed out there are failure scenarios with solids that could possibly produce a LOC, but there are also scenarios with liquids that could so the same thing. I have yet to read of a SRB failure mode that was any worse than what might occur with a liquid propellant booster. <div class="Discussion_UserSignature"> ------------------------------------------------------------------- "I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."Thomas Jefferson </div>

Can the disaster be avoided if.........

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