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  Why did Gemini-Titan lack an escape tower?

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Author Topic:   Why did Gemini-Titan lack an escape tower?
MontyCombs
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Posts: 8
From: Charleston, WV
Registered: Jun 2007

posted 06-22-2007 08:13 PM     Click Here to See the Profile for MontyCombs   Click Here to Email MontyCombs     Edit/Delete Message   Reply w/Quote
I've always wondered why a launch escape tower wasn't used on the spacecraft like in Mercury and Apollo. It seems like it would be dangerous for the astronauts to eject horizontally, especially on the launch pad.

VolMan
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From: Atlanta, GA USA
Registered: May 2007

posted 06-22-2007 08:56 PM     Click Here to See the Profile for VolMan   Click Here to Email VolMan     Edit/Delete Message   Reply w/Quote
I have wondered that too.

My wild guess would be — weight. Perhaps the ejection seats weigh less than the escape tower required to lift the Gemini spacecraft at the required velocity.

Again, just a wild guess.

By the way, as a fan, of all the three program spacecraft, I would liked to have rode in a Gemini-Titam the best. Not being an engineer, but looking at the times to achieve orbit during ascent, the Gemini-Titam had to be one hot ride. A real "hot rod" compared to an Apollo-Saturn. I am not knocking any liftoff, but just what I think would be the hottest ride.

There are some serious experts, would any of the above be correct?

SpaceAholic
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From: Sierra Vista, Arizona
Registered: Nov 1999

posted 06-22-2007 08:56 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Primarily for weight savings... spacecraft designers were looking at beyond orbit applications for Gemini-Titan — not having the tower allowed for greater payload.

Ejection seat design specifications required catapult action which placed the seat at least 500 feet from the launch vehicle while on the launch pad (actual tests demonstrated approx 800 feet) — this was outside the calculated diameter of lethality from an exploding/fully fueled Titan II.

Good details of the Ejection Seat design/testing here.

Lou Chinal
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From: Staten Island, NY
Registered: Jun 2007

posted 06-22-2007 08:58 PM     Click Here to See the Profile for Lou Chinal   Click Here to Email Lou Chinal     Edit/Delete Message   Reply w/Quote
Good question! Escape towers are heavy and produce a lot of drag. The fuel in the Titan burned rather then exploded. The McDonnell people took advantage of this.

The seat would get you about 350 feet high. I wouldn't want to try it but it did work (at least with the dummies).

As Wally Schirra once said" It's death or the seats." Speaking from experience it's not something you want to do for laughs.

kr4mula
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From: Cinci, OH
Registered: Mar 2006

posted 06-25-2007 11:25 AM     Click Here to See the Profile for kr4mula   Click Here to Email kr4mula     Edit/Delete Message   Reply w/Quote
Also read the Gemini land landings topic and you'll get some additional rationale: the proposed land landings enabled by the paraglider.

One argument was that the ejection seats provided backup for the untested (really, undeveloped!) paraglider, should it fail during descent.

I asked Rod Rose about this, since he was in charge of landing equipment in the Gemini Project Office. He in fact didn't mention the paraglider explanation at all and suggested Jim Chamberlin (GPO head) and Jim McDonnell preferred the "cleaner" design.

He also hinted at the rivalry between Chamberlin's GPO and Max Faget's engineering and development folks. Max preferred and designed escape towers. Chamberlin, the contrarian, ran a closed shop and preferred to stay away from E&D help as much as possible, including for the landing system, thus the seats and their commensurate problems.

That sort of in-house mentality persisted until Chamberlin was removed from his slot, but the damage was done.

Rose discusses this in brief and the problems at length in that interview (PDF).

I asked about ejection seats on p.55.

Danno
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From: Huntington Beach, CA - USA
Registered: Jun 2000

posted 06-25-2007 04:54 PM     Click Here to See the Profile for Danno   Click Here to Email Danno     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by kr4mula:
One argument was that the ejection seats provided backup for the untested (really, undeveloped!) paraglider, should it fail during descent.
Seems kinda nutty to eject into a parasail. Not all parasail failures would be with the parasail just not coming out.

DDAY
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From: Vienna, VA
Registered: Mar 2005

posted 06-25-2007 10:58 PM     Click Here to See the Profile for DDAY   Click Here to Email DDAY     Edit/Delete Message   Reply w/Quote
Although I don't have an answer to the original question, I suspect that it is answered in On the Shoulders of Titans, which should be available on the NASA history site somewhere.

I'll add a few more comments:

  • An escape tower was considered for Gemini. I have some early drawings of it showing the escape tower. My suspicion, without having my books handy right now, is that the performance penalties made it less practical for the Titan II and the fact that the fuel didn't really explode but burned gave them that option. I suspect that if they had the choice, they would have gone with an escape tower. The reason is that a tower is useful during other parts of the flight as well, whereas the ejection seats are not. (Then again, the Titan II accelerated so fast that the tower might not have been useful after a short period of the flight.)

  • There was an article on the Gemini escape system in Air Power History magazine about seven years ago or so. You might Google it. I'll warn you that it was terribly written, however. I found it virtually incomprehensible and it really lowered my opinion of the journal.

SpaceAholic
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From: Sierra Vista, Arizona
Registered: Nov 1999

posted 06-26-2007 11:18 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by DDAY:
My suspicion, without having my books handy right now, is that the performance penalties made it less practical for the Titan II and the fact that the fuel didn't really explode but burned gave them that option.
Hypergolic propellants (Aerozine 50 and N204) used on Titan II can and have exploded resulting in catastrophic launch vehicle failure.

Obviousman
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From: NSW, Australia
Registered: May 2005

posted 08-23-2013 04:07 AM     Click Here to See the Profile for Obviousman   Click Here to Email Obviousman     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by SpaceAholic:
Good details of the Ejection Seat design/testing here.
Does anyone have a copy of the NASA report on the Gemini ejection seat? The NTRS no longer carries it.

David C
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From: Pasadena
Registered: Apr 2012

posted 08-23-2013 08:08 AM     Click Here to See the Profile for David C     Edit/Delete Message   Reply w/Quote
Tom Stafford's words about the seat and it's lack of fully representative testing are worth a read (in his book "We Have Capture").

Spaceguy5
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Posts: 408
From: Pampa, TX, US
Registered: May 2011

posted 08-23-2013 08:58 AM     Click Here to See the Profile for Spaceguy5   Click Here to Email Spaceguy5     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Obviousman:
Does anyone have a copy of the NASA report on the Gemini ejection seat? The NTRS no longer carries it.

Here is a copy of the document on Scribd. The document is titled Development and Qualification of Gemini Escape System and was published June 1967.

mikej
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Posts: 377
From: Germantown, WI USA
Registered: Jan 2004

posted 08-23-2013 05:43 PM     Click Here to See the Profile for mikej   Click Here to Email mikej     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by kr4mula:
He also hinted at the rivalry between Chamberlin's GPO and Max Faget's engineering and development folks. Max preferred and designed escape towers.
Max Faget discusses the issue of Gemini ejection seats on page 38 of his JSC oral history:
Well, that was somewhat of an aberration, and I argued long and strong against what they did, but they did it anyway. Gemini was going to make a landing using a gliding parachute in the original concept, use a gliding parachute, and they wanted to put ejection seats in it. In the event that something went wrong with the gliding parachute, instead of having a back-up parachute, they'd just eject. So they had the thing designed with ejection seats in it from the beginning. They said, "Well, we've got ejection seats. We don't need to put the escape tower on there." And there was a little bit of rationale there. The fact that they were using hypergolic propellant meant that the fireball would not be near as big. Now, you might say, "Gee, you're going to use hypergolic propellant where you just touch it and it's going to go off and you've going to have a smaller fireball?" Yes, that's the case.

The thing about liquid oxygen and kerosene is that they can mix quite a bit before they go off. You can't mix hypergolic propellants. The minute they start to mix, they go off, and for that reason they'd blow each other apart, and the amount that ends up getting involved in the fireball is very small. You can see if the tank were to spring a big leak or an opening, the propellants could mix quite a bit and then go off. Of course, then you'd have a really big explosion. So that was the thought.

But the bad part about the ejection seats, they probably would not have worked much over about 20,000 feet of altitude just simply because the velocity would have been too high. If you had to eject very quickly while the rocket was still firing in the back, for some reason or another, you're liable to go right through the fire from the rockets. The best thing about Gemini was that they never had to make an escape.

micropooz
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From: Washington, DC, USA
Registered: Apr 2003

posted 08-23-2013 06:27 PM     Click Here to See the Profile for micropooz   Click Here to Email micropooz     Edit/Delete Message   Reply w/Quote
Here is a good chronology of the Gemini ejection system. Looks like they definitely considered an escape tower (see the November 15, 1961 entry) before selecting the ejection seats.

All times are CT (US)

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