Newsgroups: sci.space.history
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Gemini launch escape tower?
Date: Wed, 2 Jul 1997 05:00:07 GMT

In article <5pa8c9$6q3@charnel.ecst.csuchico.edu>,
Marc Siegall <msiegall@oavax.csuchico.edu> wrote:
>I've seen launch escape towers on the Mercury and Apollo capsules, but
>not on Gemini. Was there such a thing? If not, what were the plans in
>case of a pad disaster?

Gemini had ejection seats instead of an escape tower.  The theory was
that the hypergolic fuels of the Titan II could not mix and then explode,
because they would ignite on contact, and this reduced the blast hazard to
the point where ejection seats were a viable alternative.

Some fairly knowledgeable people argued that Apollo should not have an
escape tower, because the tower itself is a dangerous piece of hardware,
and Apollo's boosters were being developed correctly and should be safe.
(The main reason why Mercury had an escape tower was that Atlas's record
was so dismal at the time.)
--
Committees do harm merely by existing.             |       Henry Spencer
                           -- Freeman Dyson        |   henry@zoo.toronto.edu

From: itsd1@teleport.com (Thomas L. Billings)
Newsgroups: sci.space.history
Subject: Re: Gemini launch escape tower?
Date: Wed, 02 Jul 1997 23:18:17 -0700

In article <ECoDw8.5A%spenford@zoo.toronto.edu>, Henry Spencer
<henry@zoo.toronto.edu> wrote:

> In article <5pa8c9$6q3@charnel.ecst.csuchico.edu>,
> Marc Siegall <msiegall@oavax.csuchico.edu> wrote:
> >I've seen launch escape towers on the Mercury and Apollo capsules, but
> >not on Gemini. Was there such a thing? If not, what were the plans in
> >case of a pad disaster?

> Gemini had ejection seats instead of an escape tower.  The theory was
> that the hypergolic fuels of the Titan II could not mix and then explode,
> because they would ignite on contact, and this reduced the blast hazard to
> the point where ejection seats were a viable alternative.

> Some fairly knowledgeable people argued that Apollo should not have an
> escape tower, because the tower itself is a dangerous piece of hardware,
> and Apollo's boosters were being developed correctly and should be safe.
> (The main reason why Mercury had an escape tower was that Atlas's record
> was so dismal at the time.)

I remember seeing an explanation of this during the mid-1960s that
emphasized the radiance of the hydrocarbon fuels in the Atlas and Saturn
first stages. The idea was that, even in an explosion, the radiance of all
that hot carbon was so great as to risk frying an astronaut in an ejection
seat in the fraction of a second he'd spend in or near the fireball.  This
was supposedly was the reason for the escape towers on both Mercury and
Apollo.  I was wiling to accept this as valid at the time, since I'd
already been lectured on the problems hydrocarbons gave with radiant heat
transfer in rocket engines.

Of course, the 50:50 UDMH/Hydrazine fuel mix in The Titan II had a single
carbon in the methyl group tacked on to the hydrazine in the UDMH, but not
nearly so much.  This made people worry much less about fried astronauts,
I was told.

Any Comments on the validity of what I was fed so long ago?

Regards,

Tom Billings

--
Institute for Teleoperated Space Development
itsd1@teleport.com(Tom Billings)
ITSD's web site is at,  http://www.teleport.com/~itsd1/index.html