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  Gemini-Titan: Capability for an escape tower

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Author Topic:   Gemini-Titan: Capability for an escape tower
MontyCombs
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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
Why was a launch escape tower not used on Gemini 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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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
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.

SpaceAholic
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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 approximately 800 feet) — this was outside the calculated diameter of lethality from an exploding, fully fueled Titan II. Good details of the ejection seat design and testing here.

Lou Chinal
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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
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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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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posted 06-25-2007 04:54 PM     Click Here to See the Profile for 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 kind of nutty to eject into a parasail. Not all parasail failures would be with the parasail just not coming out.

Dwayne Day
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posted 06-25-2007 10:58 PM     Click Here to See the Profile for Dwayne Day   Click Here to Email Dwayne Day     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 is available on the NASA history site.

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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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 Dwayne Day:
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.

David C
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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").

mikej
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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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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.

History Discussion
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posted 05-16-2015 03:49 AM     Click Here to See the Profile for History Discussion   Click Here to Email History Discussion     Edit/Delete Message   Reply w/Quote
The Gemini spacecraft had ejection seats as its means for escape during launch. But I wonder if the Titan II could have supported a launch escape system had ejection seats not been used.

I believe a fully fueled Gemini spacecraft was just about at the launch vehicle's maximum capacity. Does anyone have an answer to this?

Editor's note: Threads merged.

Jim Behling
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posted 05-16-2015 06:38 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
There would be mass saved with the elimination of the ejection seats and the redesign of the spacecraft. Since an abort tower is jettisoned early in ascent, it is not a one for one performance impact. It is somewhere between (5 to 1 and 10 to 1).

Headshot
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posted 05-16-2015 08:27 AM     Click Here to See the Profile for Headshot   Click Here to Email Headshot     Edit/Delete Message   Reply w/Quote
Don't forget that the ejection system would have been use during descent had the parachute lines fouled or had Gemini been coming down on land as opposed to water. The crew might have sustained serious injuries had they been inside the spacecraft when it hit the ground.

Had NASA opted for a tower-like LES, the re-entry module itself would have had to have been redesigned to survive a land landing.

GACspaceguy
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posted 05-16-2015 02:08 PM     Click Here to See the Profile for GACspaceguy   Click Here to Email GACspaceguy     Edit/Delete Message   Reply w/Quote
I wonder if part of the reason was due to the paraglider recovery originally proposed.

Some sort of recovery would be needed if that had failed on approach (including a weather issue if there was an emergency, i.e. GT-8).

Jim Behling
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posted 05-16-2015 03:56 PM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Headshot:
Had NASA opted for a tower-like LES, the re-entry module itself would have had to have been redesigned to survive a land landing.
The requirements to negate those issues would have been been part of the design to accommodate the LES, and it would have been larger chutes and a reserve chute.

Jim Behling
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posted 05-17-2015 08:58 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by HistoryDiscussion:
But I wonder if the Titan II could have supported a launch escape system had ejection seats not been used.
Provide a weight of an LES and the weight saved by removing the ejection seats and it would be easy to figure out.

Tom
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posted 05-17-2015 09:56 AM     Click Here to See the Profile for Tom   Click Here to Email Tom     Edit/Delete Message   Reply w/Quote
So, when the decision was made not to use the paraglide return system, were the Gemini ejection seats "active" for the entire mission, or just the launch phase?

Jim Behling
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posted 05-17-2015 10:11 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
They were active during entry phase in case of a parachute failure.

Headshot
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posted 05-17-2015 11:31 AM     Click Here to See the Profile for Headshot   Click Here to Email Headshot     Edit/Delete Message   Reply w/Quote
There was a safety device called a "pin" that was removed when the ejection seat needed to be active. The pin was removed just prior to hatch closure so the ejection seats might be used, if needed, during launch.

Once in orbit, each crew member installed the pin in his ejection seat to prevent accidental ejection during orbital operations. The pins were again removed during re-entry preparation procedures, in case the crew needed to eject during descent.

Once landed, the pins were immediately reinstalled.

Jim_Voce
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posted 07-29-2016 12:30 AM     Click Here to See the Profile for Jim_Voce   Click Here to Email Jim_Voce     Edit/Delete Message   Reply w/Quote
Does anyone know if the Titan II had enough lift capacity to support the Gemini spacecraft and a launch escape system? Early in the Gemini program, some consideration was given to a launch escape system.

Other than the Rogallo wing program, I wondered if limitations in the lift capacity of the Titan II dissuaded planners from developing a launch escape system.

Also does anyone know what the maximum altitude was for the Gemini astronauts to eject? And comparatively speaking, what would the highest altitude have been that a launch escape system could have been used in the Gemini program?

Editor's note: Threads merged.

moorouge
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posted 07-29-2016 12:42 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Jim_Voce:
Also does anyone know what the maximum altitude was for the Gemini astronauts to eject?
The answer may be found here and here.
Escape can be effected from conditions of pad aborts at zero velocity to altitudes in excess of 40,000 feet at veloc­ities in excess of 1600 feet per second.

Jim Behling
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posted 07-29-2016 08:03 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Jim_Voce:
I wondered if limitations in the lift capacity of the Titan II dissuaded planners from developing a launch escape system.

It is all explained earlier in the thread, but will be repeated here, no, it had nothing to do with the lift capability of the Titan II.

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