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  Personal chute for Mercury Redstone flights

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Author Topic:   Personal chute for Mercury Redstone flights
moorouge
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Posts: 1627
From: U.K.
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posted 11-06-2013 05:14 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
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.

328KF
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posted 11-06-2013 07:04 AM     Click Here to See the Profile for 328KF   Click Here to Email 328KF     Edit/Delete Message   Reply w/Quote
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."

Rick Boos
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From: Celina,Ohio U.S.A.
Registered: Feb 2000

posted 11-06-2013 07:24 AM     Click Here to See the Profile for Rick Boos   Click Here to Email Rick Boos     Edit/Delete Message   Reply w/Quote
Grissom was the only Mercury astronaut to fly with a personal chute... it was located near the hatch.

PeterO
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Posts: 220
From: Rochester, NH
Registered: Mar 2002

posted 11-06-2013 08:13 AM     Click Here to See the Profile for PeterO   Click Here to Email PeterO     Edit/Delete Message   Reply w/Quote
Shepard also had a personal parachute. It's shown here to Shepard's right.

bwhite1976
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Posts: 181
From: belleville, IL USA
Registered: Jun 2011

posted 11-06-2013 05:36 PM     Click Here to See the Profile for bwhite1976   Click Here to Email bwhite1976     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by 328KF:
Gemini had ejection seats with integrated parachutes.
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.

328KF
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posted 11-06-2013 07:47 PM     Click Here to See the Profile for 328KF   Click Here to Email 328KF     Edit/Delete Message   Reply w/Quote
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.

moorouge
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From: U.K.
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posted 11-07-2013 01:27 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by 328KF:
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."

I thought it was John Young having just witnessed a test when the dummy astronauts were ejected but the hatches weren't blown.

ColinBurgess
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From: Sydney, Australia
Registered: Sep 2003

posted 11-07-2013 03:55 AM     Click Here to See the Profile for ColinBurgess   Click Here to Email ColinBurgess     Edit/Delete Message   Reply w/Quote
Spot on, Eddie, it was indeed John Young's quote. Speaking of dummies, I'm sure that's a dummy "Alan Shepard" in the photo in Peter's post.

space1
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Posts: 537
From: Danville, Ohio, USA
Registered: Dec 2002

posted 11-07-2013 08:06 AM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by 328KF:
Yes the intended sequence was for the hatch to be explosively separated first...
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.

328KF
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posted 11-07-2013 08:48 PM     Click Here to See the Profile for 328KF   Click Here to Email 328KF     Edit/Delete Message   Reply w/Quote
All good points space1...as a matter of fact I was looking the Gemini 4 spacecraft just the other day at NASM 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.

Rick Boos
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From: Celina,Ohio U.S.A.
Registered: Feb 2000

posted 11-07-2013 11:24 PM     Click Here to See the Profile for Rick Boos   Click Here to Email Rick Boos     Edit/Delete Message   Reply w/Quote
I stand corrected in reference to my previous post. Shepard did indeed fly with a personal parachute. My apologies.

moorouge
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From: U.K.
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posted 11-08-2013 02:31 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
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?

space1
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From: Danville, Ohio, USA
Registered: Dec 2002

posted 11-08-2013 06:57 AM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
The outer layer of the Gemini suit was made of a Dupont material called HT-1, which would later be called "Nomex." Nomex is flame resistant, but it will burn in a pure oxygen environment.

PeterO
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Posts: 220
From: Rochester, NH
Registered: Mar 2002

posted 11-08-2013 10:46 AM     Click Here to See the Profile for PeterO   Click Here to Email PeterO     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by moorouge:
So why was it excluded as a possible back-up for the orbital Mercury missions?
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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