Since the very beginning of space exploration, rockets had some sort of Launch Escape System (LES). From this Wikipedia article, we know that Mercury and Apollo had an escape tower, while Vostok and Gemini had ejection seats.

Apollo LES pad abort test

Apollo LES pad abort test (source: wikimedia.org)

Initially, the Space Shuttle had ejection seats but, (citing Wikipedia)

were removed once the vehicle was deemed operational

practically leaving it without any LES. What are technical reasons for this choice?

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    $\begingroup$ Part of this is documented in the Wikipedia page on Space Shuttle abort modes: en.wikipedia.org/wiki/… $\endgroup$ – Bart Aug 17 '13 at 20:20
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    $\begingroup$ Is there any study actually proving STS-51-L crew would've had any chance in surviving, if any escape system was installed / in use on board Space Shuttle Challenger? I mean, even with additional LES engines (on top of Space Shuttle's own), I just don't see it possible to escape that inferno alive. I might be utterly wrong, mind you. But I would like to see some feasibility study first, before suggesting such a system might have saved their lives. $\endgroup$ – TildalWave Aug 17 '13 at 20:53
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    $\begingroup$ @TildalWave This is a very hot and sensitive topic in space community. The sad thing is, there are a fair number of reasons to assume, that most of the crew survived the disintegration of the space shuttle. From a physical point of view, it was not even an 'explosion'. Furthermore, it is save to assume, that some crew members may have lived until the pressure compartment hit the water. In a way, a simple parachute could have made a difference here. (For sources, you need to read the original accident report of NASA. Or carefully ask any NASA astronaut - they are all familiar with this topic.) $\endgroup$ – s-m-e Aug 17 '13 at 22:39
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    $\begingroup$ My question is why, not what if. I never thought about a that kind of question, since I think has not answer. That suggestion is in your comment @TildalWave, but since someone like you could misread my question, I'm going straight to edit it and remove any reference to Challenger. $\endgroup$ – user55 Aug 17 '13 at 22:39
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    $\begingroup$ I guess the complete answer is "budget cuts". Each gram of weight brought to orbit costs a small fortune, and the ejection mechanism isn't quite lightweight. $\endgroup$ – SF. Aug 19 '13 at 10:54

Providing crew escape for all phases of flight of the Space Shuttle, given its design architecture, was simply not practical. Keep in mind you have up to 7 crew members on two decks. Keep in mind that the flight regime consists of large ranges of altitude and velocities. Keep in mind that it would have to cover launch, landing, and several abort modes. Even the ejection seats used in the early flights couldn't cover the entire flight regime and only worked for the Commander and the Pilot.

So to answer your question directly: ejection seats would have only been useful for the crew on the flight deck and then only for a (very) limited part of the total flight regime.

Regarding the use of a LES on the Shuttle: There were some studies done during early design phases of a separable crew compartment. Not surprisingly, this added an unacceptable amount of mass to the Orbiter -- at least with the architecture selected. Of course, this system looked nothing like the LES used on Apollo. Also, even the LES on Apollo didn't cover all of Apollo's flight regime.

Another interesting fact: the Shuttle was initially designed to allow a shirt-sleeve environment for the astronauts. This means that prior to STS-26, Shuttle astronauts didn't even wear parachutes (excepting the early qualification flights with ejection seats). In fact, the seats were not designed to handle astronauts with a parachute. By "handle," I mean handle the additional weight and volume of a crew member with a parachute and other gear attached. The seats were modified (and eventually entirely redesigned) for STS-26 and beyond for when the crew members did wear parachutes.

These new chutes were expected to be used for a very limited range of flight regimes/abort modes where the Orbiter could be put into a stable glide configuration that allowed all of the crew to bail out. This means that you had to ride the solids for at least 2 minutes till they burned out, do some fancy flying to get rid of the External Tank, get the Orbiter into a stable auto-piloted glide, climb down (or over) to the hatch, blow the hatch, extend a pole (see next paragraph), and bail out (x7). So this really wasn't a launch escape system -- once you light the SRBs, you are committed to at least 2 minutes of powered flight.

Bailing out was to be done with the aid of a crew escape pole. The pole kept the crew from hitting the leading edge of the wing. There is some good test footage available here: http://youtu.be/dfVTX25hH-I. Note that none of this would have helped the astronauts we lost on 51-L or STS-107.

So what is the take-away here? One (of many) of the big reasons the Shuttle was retired was its lack of provision for crew escape. All of the likely new manned US systems (government contracted and private) include crew escape for most if not all of the flight regime. This is one of the reason why most of these systems go with capsules too.

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    $\begingroup$ The Buran was never manned. It didn't even have oxygen for crew members. $\endgroup$ – Erik Aug 20 '13 at 20:00
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    $\begingroup$ Pure conjecture. Until the system is actually operational, it is nice to say that the crew would have had crew escape at every point. We will never know. $\endgroup$ – Erik Aug 20 '13 at 20:10
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    $\begingroup$ @Erik - we have to look at design docs. The SRBs and the full ET made a pre-SRB burnout abort impossible (exhaust from the SRBs, separation loads, tumbling ET). $\endgroup$ – Deer Hunter Aug 20 '13 at 20:32
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    $\begingroup$ @Dave, any "blast clear" prior to SRB separation would have taken it through the exhaust plume of the SRBs, with unpleasant consequences. After SRB separation, flying clear of the external tank was possible: these were the "return to launch site" and "transatlantic landing" abort modes. $\endgroup$ – Mark Jun 21 '16 at 22:28
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    $\begingroup$ What @LocalFluff says about Buran's ejection seats reminds me of the first few qualification flights for the space shuttle, which were done with a crew of two and ejection seats. Space Shuttle abort modes: Ejection seat on Wikipedia has details. $\endgroup$ – user Jan 13 '17 at 10:20

The Shuttle just did not have good abort options for most of the flight window. One possible change that would have required being designed in from the beginning would have been an abort system where the entire crew compartment would separate like on an F-111. But it would have added cost and complexity and was not actually designed in.

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    $\begingroup$ What actually destroyed Challenger? Not the SRB burning through. Not the ET burning. It was being pitched into the hypersonic airflow that physically destroyed the airframe. Possibly killing most of the crew as well. How do you depart, at hypersonic speeds, while still in appreciable atmosphere from burning SRB's and a tank, when your engines will cut off as soon as you ditch the tank? The airflow will kill you. $\endgroup$ – geoffc Aug 11 '15 at 13:18
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    $\begingroup$ The Shuttle had zero tankage for SSME's inside it. All that it would hold internally is the volume left in the plumbing, which I imagine would run out in milliseconds if you were lucky. $\endgroup$ – geoffc Aug 11 '15 at 15:41
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    $\begingroup$ @LocalFluff You are describing RTLS. It was only possible in a VERY narrow window. And NO it could not carry enough fuel to land. Not using SSME's. They can only throttle down to I think 60ish percent. At that rate, even only one SSME would burn through fuel so fast that there would be payload left on the Shuttle to support it. This would be a good question as there is lots of reasons. $\endgroup$ – geoffc Aug 11 '15 at 17:29
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    $\begingroup$ @LocalFluff New question asked space.stackexchange.com/questions/10600/… $\endgroup$ – geoffc Aug 11 '15 at 21:36
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    $\begingroup$ @geoffc: Your comment about the plumbing inside the Shuttle inspired this question: space.stackexchange.com/q/35744/26446 $\endgroup$ – DrSheldon Apr 24 '19 at 21:24

In order to obtain additional political support for STS, NASA essentially convinced lawmakers to force the Air Force/NRO to replace Titan with Shuttle as the launch vehicle for KH-11 spy satellites and other intelligence hardware which would require launches directly into polar orbit. As both of these programs progessed, weight grew beyond original specifications. The margin was very close already before the increases, and by 1984 NASA was getting ready to do some pretty risky stuff to make good on their promise to launch intelligence payloads--including filament wound boosters, running Block I engines with the original throats/injectors/turbopump impellers at 109% for the entire flight. This should give you an idea of why even 5,000 lbs was completely out of the question for an effective LES. Of course, 51L happened and pretty much the entire military mission was ditched save for a few birds already configured for Shuttle launch, so ironically the same LES that could've easily saved the 51L crew would've ultimately been feasible for the missions STS ended up flying.

  • $\begingroup$ TL;DR: It wouldn't be able to launch the satellites it was contractually built for. $\endgroup$ – Mazura Dec 23 '18 at 19:19

An effective launch escape system was not incorporated into the STS because of weight considerations that now seem to be both short sighted and even absurd.

Possible Escape Systems.

1) An escape ejection capsule system similar to the one used in the B-58 Hustler was a possibility. But the ejection capsule weighed several times as much as the seats on the shuttle and were thus not developed.

2) Then there is the fact that the entire crew compartment could (should) have been designed to separate as was the case with the F-111 escape system. However the system would have once again been in NASA's opinion too heavy.

3) verum potest esse penale

The reality is I believe that NASA didn't want to reduce the payload capacity of the STS by including an effective crew escape system. It seems that 50,000lbs of payload to LEO was the 'magic' number NASA wanted and reducing that for the sake of crew safety down to 40,000 to 45,000 pounds of payload to LEO was an undesirable effect of incorporating such an escape system. A system mind you that could have safely protected the crew members from a stationary position on the pad up to a speed of +Mach 2.

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    $\begingroup$ Hmm, Mach 2 out of a maximum of Mach 25, that's certainly very effective for a 10-20% payload reduction…. $\endgroup$ – Nathan Tuggy Jan 13 '17 at 6:26
  • $\begingroup$ Yes, Mach 2 has you covered for something like the first 70-80 seconds of flight. By the time the SRBs provide negligible thrust and are jettisoned, you are already at Mach 4 or thereabouts, and that's around two minutes into the flight. $\endgroup$ – user Jan 13 '17 at 7:43
  • $\begingroup$ The +mach 2 figure assumes that the escape system would be no more robust than those on the B-58 or F-111. Be that as it may I have no doubt (but can not prove) that a very similar system to the B-58s ejection capsule system could have been designed and produced that would be effective at mach numbers s high as 4. But that is something we will never know. $\endgroup$ – user18198 Jan 13 '17 at 11:07
  • $\begingroup$ The question is not about possible escape systems but about why the orbiter didn't have one. The only part of your answer that addresses this seems to be a 'belief' of yours. Do you have any reference to back this up? $\endgroup$ – Organic Marble Jan 13 '17 at 13:48
  • $\begingroup$ Organic Marble....From Encyclopedia Astronautica, "the shuttle was designed as if it had the inherent operating safety of an airliner. It was not equipped with any provision for crew rescue in case of booster failure during ascent to orbit, or being stranded in orbit, or structural failure during re-entry............ "But the weight problem also meant that there was no margin for crew safety measures without (to NASA) unacceptable impact to the net payload." This is common knowledge full article= astronautix.com/s/shuttle.html $\endgroup$ – user18198 Jan 13 '17 at 21:19

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