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Old 12-18-2013, 11:27 AM
luke strawwalker's Avatar
luke strawwalker luke strawwalker is offline
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Quote:
Originally Posted by astronot
I was looking at and comparing the different earlier manned Space Flight vehicles of the U.S. and I was wondering why the Gemini Titan looked like a departure from the others and then it hit me.

It doesn't have an escape tower.

So then my next question is why? I'm sure someone here knows.

An example of what I'm talking about is attached.

David


Gemini was equipped with ejection seats... thus no need for a tower...

The Atlas was powered by LOX and kerosene... and Redstone was powered by LOX and alcohol... the later Saturn was powered by LOX/kerosene and LOX/LH2 (enough to make a small atom bomb yield if it blew up). The Titan II, on the other hand, was powered by nitrogen tetroxide oxidizer and Aerozine 50 (50/50 mix of hydrazine and unsymmetrical dimethyl hydrazine). These propellants are room temperature storables, and also will ignite on contact with each other (hypergolic). They won't explode when mixed, just burn at a predictable rate, unlike LOX and other propellants which burn EXTREMELY FAST in an uncontrolled fireball if the vehicle were to fail. Thus, due to the slower, more predictable burn rate between NTO and UDMH/hydrazine, if the Titan rocket failed on the pad or early in flight, it was felt ejection seats were sufficient to ensure the astronauts survival should they need to escape a failing booster. The Gemini spacecraft, since one of the requirements was to be able to conduct spacewalks, also was equipped with large individual hatches for each astronaut directly "overhead" for each astronaut. These hatches would be jettisoned shortly before the ejection seats fired to blast them out of the capsule in an ejection. The Mercury spacecraft, on the other hand, was equipped only with a small, off-center hatch that one could barely squeeze through, and there simply was no way they could make an ejection seat work with it, nor was their enough weight allowance in the design to permit the use of a heavy ejection seat. Besides, an ejection seat was not sufficiently powerful to get an astronaut safely away from an exploding Atlas, and might not have been for a Redstone, either... hence the launch escape tower on Mercury.

By the time the Apollo came along, weight was a MUCH more important consideration in the design than it had been on Gemini, due to the requirements of sending extra weight to the Moon and back. Plus, there simply wasn't room in the spacecraft for THREE heavy ejection seats, and of course requiring three heavy hatches instead of one would also greatly complicate spacecraft design and compromise the mission. Plus, the Apollo was designed to fly on Saturn V (and Saturn IB) and both of those launch vehicles were SO large and would create fireballs SO huge if they failed on the pad or early in flight, that ejection seats would not be powerful enough to get the astronauts safely out of the fireball... hence the return to a launch escape tower for Apollo.

In fact, the Apollo escape tower was more powerful than the Redstone that launched Alan Shepard and Gus Grissom on the first two Mercury missions back in 1961...

Later! OL JR
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