"blow the hatches" on Gemini

In article ,
Geert Sassen wrote:
But, in practice, was an on-the-pad-abort survivable on Gemini? Various
stories are a bit contradicting, it sounds like "yes, you could eject on
the pad, but it would be suicide". It is doubtfully whether you would
reach enough altitude to safely open the parachute...

No, that was pretty much assured. What was less clear was whether you'd
be intact at touchdown. Clearing the fireball of a booster explosion
wasn't easy, and the Gemini seats were the most powerful ejection seats
ever built, operating right at the limits of human acceleration tolerance.
Even aircraft ejection is violent enough that serious injuries are not
uncommon, and ejecting from a Gemini was just plain dangerous.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

There is not a lot of room for error. In the Project Gemini add-on for
Orbiter I wrote, I had to make sure every detail was accurate before
the pad eject worked. Even with that, you eject get tossed up a couple
of hundred meters and then the chute opens. The whole thing is done in
about 30 to 45 seconds.

Rob Conley

But, in practice, was an on-the-pad-abort survivable on Gemini? Various
stories are a bit contradicting, it sounds like "yes, you could eject on
the pad, but it would be suicide". It is doubtfully whether you would
reach enough altitude to safely open the parachute...

Henry Spencer wrote:

No, that was pretty much assured. What was less clear was whether you'd
be intact at touchdown. Clearing the fireball of a booster explosion
wasn't easy, and the Gemini seats were the most powerful ejection seats
ever built, operating right at the limits of human acceleration tolerance.

Of course, hypergolic fuels don't "explode", they simply burn :-)

--
Dave Michelson

Henry Spencer wrote:

Yes and no and kinda. They couldn't be jettisoned, but the ejection
system included pyrotechnic actuators -- hot-gas pistons -- to unlatch and
open the hatches very quickly. As each hatch actuator finished its
stroke, the movement of the piston uncovered vent ports which released hot
gas into the igniters of the seat propulsion system.



Now that was a novel set-up!

Pat

Henry Spencer wrote:


They would have liked to rely exclusively on the seats, but the speed and
altitude just got too high later in ascent.



Vostok's ejection seat had a degree of thermal protection on its bottom
to give the cosmonaut a better chance of surviving if he had to eject at
high altitude and speed during a abort situation:
http://www.ejectionsite.com/updates/vostok.jpg
As can be seen, the design is around halfway between a normal ejection
seat and a escape capsule.

Pat

Pat Flannery wrote:

Yes and no and kinda. They couldn't be jettisoned, but the ejection
system included pyrotechnic actuators -- hot-gas pistons -- to unlatch
and
open the hatches very quickly. As each hatch actuator finished its
stroke, the movement of the piston uncovered vent ports which released
hot
gas into the igniters of the seat propulsion system.


Now that was a novel set-up!

It didn't always work in the correct sequence, i remember reading a
story about one of the seats slamming straight *through* the hatch
during a test, resulting in a comment from Young "that will give a *big*
headache... but a short one".

Regards,

Geert

Robert Conley wrote:

There is not a lot of room for error. In the Project Gemini add-on for
Orbiter I wrote, I had to make sure every detail was accurate before
the pad eject worked. Even with that, you eject get tossed up a couple
of hundred meters and then the chute opens. The whole thing is done in
about 30 to 45 seconds.



On Vostok they at least gave some thought to having the cosmonaut eject
into a giant net at a distance from the pad in case of a pad abort-
although I don't know if this piece of circus equipment was ever
actually used in a manned launch, or if they decided to rely on a
quick-opening parachute on the seat.
The seat had a pair of good sized solid rockets mounted on its
underside, so it was probably capable of traveling quite a distance once
it was ejected.
You can see part of one of the solid rockets on this photo:
http://www.ninfinger.org/~sven/model...p/vostes02.jpg
It's the cylindrical thing near the descriptive placard.
I assume that you were to use the seat up till the aerodynamic fairing
was jettisoned, then rely on using the retro engine to separate the
spacecraft from the upper stage and make a normal reentry in the reentry
sphere after jettisoning the equipment module.

Pat

Geert Sassen wrote:


It didn't always work in the correct sequence, i remember reading a
story about one of the seats slamming straight *through* the hatch
during a test, resulting in a comment from Young "that will give a
*big* headache... but a short one".



How'd you like to eject straight up into the fouled parawing? That
wouldn't be fun either.
I keep wondering if that influenced the decision to abandon the concept.

Pat

Pat Flannery wrote:

Vostok's ejection seat had a degree of thermal protection on its bottom
to give the cosmonaut a better chance of surviving if he had to eject at
high altitude and speed during a abort situation:
http://www.ejectionsite.com/updates/vostok.jpg
As can be seen, the design is around halfway between a normal ejection
seat and a escape capsule.

Except for the fact that it's got nothing escape capsule like about
it, yes.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

In article , says...
In article ,
Kevin Willoughby wrote:
In this country, we produce more students with university degrees
in sports management than we do in engineering. - Dean Kamen

That quote was a Congressbozo's stupid mistake -- the US graduates more
than a hundred times as many engineers as sports managers each year.

Oh dear. .sig reverted.

I heard Kamen site that statistic at a motivational speech he gave to a
class of engineering students at WPI. I thought it was a great lecture
(How failure to design a small Sterling engine could, maybe, relieve the
suffering of the poorest folks on Earth.) I hope the rest of the talk
was better researched!
--
Kevin Willoughby lid

The loss of the American system of checks and balances
is more of a security danger than any terrorist risk.
-- Bruce Schneier