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posted 11-06-2013 05:14 AM               

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Browsing through "Exploring the Unknown" I came across an entry that listed possible ways of effecting a landing for the Mercury astronauts in the event of a system failure. One of these for the Redstone missions was a personal chute that the astronaut could use if the main chutes failed to deploy. Exit from the capsule was to be either through the hatch or by way of the neck.

On the face of it, it seems extremely hazardous. So, when was this idea dropped and was it because of an astronaut veto?

The relevant document is dated April 1961 and is part of a risk assessment for the Mercury flights.

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posted 11-06-2013 07:04 AM               

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Grissom's chute was recovered with Liberty Bell 7, so he definitely had one aboard. I'm not certain if every other Mercury spacecraft had one.

Gus was popularly quoted as saying about the chute, "Well, it'll give me something to do until I hit the water." That might sum up the sentiment of most of the astronauts.

Gemini had ejection seats with integrated parachutes. Concerns at the time included ejecting into the exhaust plume or into an unopened hatch. It wasn't until years later that it was realized they would have been igniting a rocket motor in a pure oxygen environment. With their suits and chutes soaked in O2, Tom Stafford commented that they "would have come out of there like two roman candles."

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posted 11-06-2013 05:36 PM               

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quote:

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Originally posted by 328KF:
Gemini had ejection seats with integrated parachutes.

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What was the sequence of events on the Gemini ejection? Would the ejection rockets fire and then the hatches blow off?

I would think if the hatches popped off a millisecond before the rockets fired, the O2 would have been vented out to some degree and the astronauts could have avoided being set on fire by the cabin atmosphere?

I realize this is all moot, when as you indicated, maybe the hatches don't even open, maybe the astronauts eject into engine thrust, etc. I know "On the Shoulders..." talks about this, but I am nowhere near my copy.

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posted 11-06-2013 07:47 PM               

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Yes the intended sequence was for the hatch to be explosively seperated first. I believe it was Stafford who questioned what would happen if they didn't and somebody quipped that it "would be the shortest headache you ever had."

The issue with the oxygen is that even though the cabin opened up with the hatch explosives, all of the fabric in the ship, including suits, parachutes, velcro, etc. was completely soaked for hours in pure O2.

It would take some amount of time before all of that could outgas from the fabrics and render them less flamable- certainly longer than the time between hatch jettison and ejection seat motor ignition.

Hope this helps.

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posted 11-07-2013 08:06 AM               

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quote:

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Originally posted by 328KF:
Yes the intended sequence was for the hatch to be explosively separated first...

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The hatches would not be explosively separated, but rather unlocked mechanically and then opened hydraulically (through expansion of hot gases) by a hatch actuator at the start of the ejection sequence.

Seat catapults would force the extraction of the seats. Then 4" from the end of the seat rails, at 0.394 seconds after initiating the ejection, the seat rockets would ignite. Up to that point all of the actions are either mechanical or contained. At seat rocket ignition the cabin would be open to the atmosphere and no longer pressurized with pure oxygen.

However, as mentioned previously, with everything saturated in pure oxygen for hours, practically everything made of fabric would likely have caught fire. I wonder if the parachutes would have been spared, and if the Nomex of the suits would have worked well enough to protect the astronauts. On the other hand, the ignition source (seat rocket) would have been downstream from the astronaut and seat, already moving rapidly into the air by the action of the seat catapult. So perhaps only the cabin fabrics would have been ignited.

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posted 11-07-2013 08:48 PM               

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All good points... as a matter of fact I was looking the Gemini 4 spacecraft just the other day at National Air and Space Museum and noticed the apparently simple hatch design with common hinges on both the currently installed hatch and the removed one.

It did not appear that there was any complex explosive mechanism to separate the hatches before ejection. I have some references for the Gemini system but being away from home I don't have access to them at the moment.

I am reasonably sure that the Gemini suits were constructed of plain nylon, rather than Nomex. As the story goes, Pete Conrad's involvement in auto racing was what brought Nomex to NASA, kind of like a reverse "spinoff." Prior to that, after the Apollo 1 fire came the Dow-Corning produced Beta Cloth which was made of Teflon coated glass fiber woven into sheets suitable for suit coverings and other cabin equipment.

But even Nomex is considered to be "fire retardant" as opposed to "fire proof," and I'm not clear on whether the Gemini ejection seat tests were performed from a pure oxygen environment or not. Definitely a subject worthy of further research, but I took Stafford at his word that he had considered these factors in his recollections.

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posted 11-08-2013 02:31 AM               

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Returning to my original posting - as far as I've been able to ascertain the personal chute was only available for the Redstone flights.

So why was it excluded as a possible back-up for the orbital Mercury missions?

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posted 11-08-2013 10:46 AM               

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quote:

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Originally posted by moorouge:
So why was it excluded as a possible back-up for the orbital Mercury missions?

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Mercury was both volume and weight limited. I'm just guessing here, but if the 'chute was not seen as a viable escape method, removing it freed up space and weight for other equipment. For instance, Sigma 7 carried an equipment pouch where the 'chute had been mounted.

Other equipment was deleted as unnecessary as the program progressed, including the entire periscope on Faith 7.

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posted 06-04-2017 07:14 AM               

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Alan Shepard carried a personal parachute with him on his MR-3 mission. Given that his Mercury capsule had a primary parachute as well as a back-up parachute if the main chute failed to deploy, why did Shepard carry a personal parachute as well?

Editor's note: Threads merged.

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posted 06-04-2017 07:50 PM               

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The thought was that if the escape tower failed to separate, neither of the capsule chutes would be available.

After two successful flights, and the fact that weight was always a major consideration for the orbital flights, the chest pack chute was deleted.

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posted 06-06-2017 05:07 AM               

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That all depends on what stage of flight and what altitude the failure happens. If the failure happens during launch at low altitude then the parachute is good for giving you a warm fuzzy feeling. If it is a launch vehicle failure then your chances are slim to none as well.

I guess the envelope for use would be similar to Gemini ejection seats on reentry and the altitude and velocity limits would be lower on launch.

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posted 06-06-2017 06:09 PM               

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I would think the critical part would have been strapping on the chest pack and exiting the hatch. Seeing the contortions needed to enter the capsule, without the 'chute, it's hard to imagine how an astronaut could don the 'chute and exit in a timely fashion.

I wonder if that was ever practiced?

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posted 06-06-2017 08:39 PM               

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quote:

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Originally posted by Joel Katzowitz:
How long did the quick release procedure take to provide an exit point for Shepard?

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A lever with a push-button lock release at the tip was mounted on the interior side of the hatch. The procedure was to push the lock release button and pull the lever inboard. The slipstream would almost certainly pull the hatch free.

Once the helo had raised Freedom 7 clear of the water, Shepard released the hatch and allowed it to fall into the water. It was quite heavy and there were no plans to retain it. The hatches from BOTH M-R flights currently reside on the bottom of the ocean.

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posted 06-08-2017 08:48 AM               

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quote:

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Originally posted by Skythings:
How much time would be involved between failure of a chute and impact?

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On Grissom's flight the main chute deployed at about 13,000 ft. Until then, with the drogue chute deployed the descent rate was some 40 fps though this is a number reported by Grissom as the main chute opened and the rates were falling.

One has to assume that the descent rate was higher than this on the drogue. Nevertheless, taking the 40 fps rate as a starting point, the astronaut would have had a little over five minutes before the ocean brought an end to the flight. Obviously, faster rates would lessen the time available to don the personal chute and exit the capsule.

So, to answer your question, one imagines that the time available would be somewhere between two minutes (worst case) to a little over five minutes (best case).

I've no doubt that someone with a better grasp on the actual numbers can improve on this and give you a more accurate estimate.

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posted 06-10-2017 07:37 PM               

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Both Shepard and Grissom were equipped with 26' Navy conical type canopies. The were from a lot made by Pioneer Parachutes Manchester, Conn. in 1957. I think the main reason for elating them from the Atlas flights was weight.

I did try to climb out of the Mercury prototype at McDonnell in the 1980's. It was very difficult but doable. I am 5'7' (Grissom size).

As far as firing the Gemini seats go, it's like the old Beach Boys song "God Only Knows."