Strapping your self into a tiny capsule on top of what essentially controlled a large controlled explosion is one of the hazards of being an astronaut but if things go really wrong then is nice to know there is an escape system of some sort to get you out of there but how can you escape an exploding rocket if things go with a bang in all the wrong ways.
One of the great problems that engineers had to face when sending the first humans into space was how to save them should something catastrophic happen during launch, which in the early days before Apollo was actually quite common.
On the early manned missions there two main schools of thought on launch escape systems, the first was that originated by the American Maxime Faget, the designer of the Mercury spacecraft in 1958. He proposed a solid rocket motor puller that would be attached to the crew capsule by a tower which would fire in the event of a rocket malfunction and then pull the crew capsule away from the main rocket and float down to earth by parachute.
The second was to use ejection seats similar to a jet aircraft, this was used by Soviets on their Vostok rockets which included the one to launch the first man into space Yuri Gagarin and also on the US Gemini mission which came after Mercury and the rocket-based launch escape system.
The ejection seat system was simpler but had several drawbacks and was limited to about the first 40 seconds of flight because after that time, the speed of the rocket was too fast safely eject from. However, if there was a problem with the rocket either on the pad or within the first 20 seconds of the launch and the ejection seat were fired it could still be too close the ground and there wouldn’t be enough time to deploy the parachute.
In the Soviet system, large nets were placed around the launchpad to catch the ejector seats if they fired before the rocket took off, but that then placed the crew in the extremely dangerous position of being close to rocket if it exploded. The chief designer of the early soviet missions, Sergie Korelov said that he “felt terrible” about the inadequate system for crew escape in the opening seconds of a launch.
But the Soviet ejector system was used during the decent of each returning Vostok capsule. At about 7000 meters or 23,000 ft, the cosmonaut would eject and the land by parachute because the landing of the capsule itself was very rough and would more than likely cause serious injury to anyone inside. This is one of the reasons why the US landed their capsules in the sea, a parachute splashdown is much less of a shock landing on the water than one coming down on to land.
The now almost standard type of launch escape system use variations of Maxime Fadget design with solid or hygergolic rocket motors carrying the crew capsules away from the main rocket body. The main advantages of this is that the crew are protected from the atmosphere if the incident occurs later on in the launch at high speed and if it happens on the launchpad they are carried up and away from a potentially exploding rocket in less than a second
In 1959 just a few months after the contract was signed for the Mercury project the first tests were carried out on the rockets for the launch escape system or LES. These were mounted of a trellis-like tower fixed to the crew capsule and they could operate with a fraction of a second of a problem being detected.
A new small solid rocket-powered booster called “Little Joe” was built to test the LES under real conditions. In the later tests, a rhesus monkey was placed in the crew capsule to measure the G-forces and stresses on a living creature.
Within 16 months of the start of the Mercury program, the successful test of an off the pad abort was carried out on a production spacecraft carrying it to a height of over 600 meters or 2000ft but it wouldn’t be long before a real-life emergency would test out the system.
On 21st November 1960 the first full unmanned test flight of the Mercury-Redstone 1 was carried out.
But due to an error in the order in which the control and power cables should have separated, the rocket’s control system shut the engine off when it was a few inches of the pad, gaining it the nickname of the “4-inch launch”. This caused the rocket to act as it would at 40,000 ft or 12,000 meters and ejecting the tower and the antenna parachute, just as it was meant to but it left the rocket standing fully fuelled and unsupported on the launchpad. It was decided to leave the rocket balanced on the pad until the next morning when the batteries had depleted and the liquid oxygen had boiled off before the technicians could move in.
Although Mercury went on to be a successful program, the following Gemini mission reverted to ejection seats, something that Maxime Faget was opposed to not only for the same reasons as the Soviets had misgivings for, but that he thought the crew could end up being launched through the Titans rocket exhaust plume.
The main reason for the change was that the designer of the Gemini spacecraft Jim Chamberlin thought that the tower system of the Mercury would add much more weight than ejection seats. We have to remember that the Gemini–Titan II missile was like many of the early rockets which were modified Ballistic or Intercontinental Ballistic Missiles and not built for human space transport like the later Apollo.
This meant that the payload weight was a major issue and the tower which was discarded as the rocket reached space, could be seen as an unnecessary and heavy requirement if the crew could be removed from the spacecraft with a lighter alternative method.
It was also thought that in the event of a launchpad rocket explosion, the use of hypergolic fuels in the Titan would create a smaller fireball and explosion compared to liquid oxygen/RP1 mixture of the Mercury and therefore didn’t necessitate a Mercury style LES.
A lot of work was done to provide an ejection seat system which could cope with mission demands from the launchpad right up to 70,000ft and was much more sophisticated than the aircraft ejector seats of the time and although Gemini 6A came close to using them when the rocket shutdown 1.5 seconds into the launch they were never used for a real manned ejection.
After the Gemini program was over, Maxime Faget said that the best thing about it was that no one had to make an escape from it.
Although Apollo followed Gemini, Apollo reverted to the puller rocket system similar to Mercury but larger and also included a shroud that would cover the front of the command module, not only to protect it against the rocket exhaust should the escape system be needed but also as a heat shield from the atmosphere during launch.
This whole subsystem including the shroud was 10 meters long and weighed 3,630kg, still a considerable weight to carry but the Saturn was a much bigger and more powerful rocket than the Mercury-Redstone and this would be jettisoned at 295,000 ft or 90km, just on the edge of space.
The Apollo system could operate automatically during the first 100 seconds after which it would automatically turn off. It could also be manually triggered by the astronauts at any time from the pad to its jettison altitude. If it was on the pad the LES would launch the command module to about 4000ft or about 1200 metres.
In its automatic mode, part of the system used 3 wires which ran down the side of the main booster to detect if the structure of the rocket was starting to break up, this was unintentionally tested during a test in Nov 1965.
Again “Little Joe” was being used as the test rocket which was to launch upto 10,000ft or 3,000 metres then fire the launch escape system. But due to a setup error with the roll gyros, as “little Joe” rose it began to roll faster and faster until it broke up, the escape system monitor wires down the side of the rocket were severed and the escape rocket fired and lifted the command module up and away exactly as it was supposed to. Although the rocket in the test had failed, the launch escape system had worked perfectly and as such, it turned out to be the ideal test.
Luckily, non of the Apollo missions required the use of the launch escape system.
Sadly for the Space Shuttle, the two occasions of the Challenger and Columbia disasters there were no means of escape from the shuttle.
Only the first two shuttles Enterprise and Columbia had ejection seats because they were designed to be flown with a crew of two during its development, these were removed once the rest of the crew seats in the lower deck were fitted and all the following shuttles had normal seats.
The reason for not using them was summed up by STS-1 pilot Robert Crippen who said that once the Solid Rocket Boosters were running, even if you managed to eject safely you would probably end up going through the fire trail from the SRBs and if you survived that, then your parachute would have been burned up and by the time the SRBs had detached, you were too high and too fast for an ejection seat system away, something which all the crews had to accept.
With Columbia, the break up occurred during re-entry at hypersonic speeds where there was no chance that they could have survived in an ejector seat even if they had them. In the subsequent crew survivability report, the investigation team said that there were no known space suit technologies available other than the shuttles crew module itself that could have saved them and that had disintegrated along with the rest of the shuttle.
The Soviet Buran shuttle had ejections seats but only for a two-man crew and only worked up to 30,000ft or about 9,000 metres. As the only launch before the program was shut done was a fully automated one with no crew we don’t know whether they would have been kept or removed the ejectors like the US Shuttle.
With the recent resurgence in space missions by NASA and private companies like SpaceX, Boeing and Blue Origin, the Launch Escape Systems of Apollo have been brought back and updated with modern twist and technology.
NASA’s new Artemis program which will return man to the moon continues in a similar way to Apollo with a new updated Launch Abort System (LAS) and is again designed to be jettisoned after launch to reduce the weight carried during deep space flights.
Using the same type of puller rocket system as Apollo, it’s the most powerful yet built and needs to be to outrun the 8.8 million pounds of thrust from the SLS rocket.
The new escape rockets consist of the abort motor that will pull the Orion capsule up and away and an attitude control motor that sits at the top of the tower. The attitude control motor is the first solid rocket motor designed for vectored thrust and uses the length of the tower as leverage to change the direction of the escape system so as to get as far away from the SLS rocket as possible. Basically, the whole subsystem including the Orion will become its own aircraft. After the Orion has been moved to a safe position the launch abort tower will be ejected and the Orion will splashdown by parachute.
This is in contrast to the SpaceX Dragon 2 spacecraft, it’s Launch Abort System uses rocket motors which are part of the spacecraft itself and push the spacecraft up and away from rather than pull it. Whilst this adds weight which is not ejected at the end of the launch, the major difference is that this is designed to ferry crew and cargo to go to and from the ISS and is not designed to go into deep space to the moon and beyond like the NASA Artemis.
The Dragon 2 uses eight SuperDraco hypergolic rocket engines, the fuels of which combust on contact with each other. Whilst these fuels are highly toxic they are very stable whilst in space and going through the multiple day-night heating cycles each 24 period when they are docked at the ISS, something that solid rocket motor fuel can have a problem with and become unstable.
Because the rocket engines of the Dragon 2 are contained in the body of the craft and the craft is designed to be reusable, so are the engines which cuts down on the costs were as the Artemis Orion launch abort tower is ejected after the launch and not reusable.
Because the Dragon 2 lands in the sea, it can’t be reused for manned flight and can only be used for cargo flights going forward but SuperDraco engines can be used for further manned missions.
As the SuperDraco engines are built-in and not ejected at the end of the launch can also provide propulsion whilst in space and do things like orbital boosting of the ISS.
They were also due to be used for propulsive landing for the Dragon 2 like the Falcon 9 boosters do, but in 2017 SpaceX dropped that in favour of parachute splashdowns because of the difficulties of making the propulsive landing system man-rated and issues of the landing legs coming out of the heatshield.
Both Blue origin with the New Sheperd and Boeing with the CTS-100 Starliner will also be using reusable spacecraft with similar pusher rocket abort systems to the Dragon 2 the next few years will be an exciting time for space, hopefully, none these launch escape system will need to be used in an emergency but if they do the crews will have the best escape system so for developed.
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