[AR] Re: titans and stuff \ Re: Re: names please
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 18 Nov 2016 00:52:20 -0500 (EST)
On Thu, 17 Nov 2016, David Weinshenker wrote:
For example, Dyna-Soar was one of the design payloads for the
Saturn I
Interesting - somehow I had got the idea that Dyna-Soar was to use one
of the early Titan "heavy" (i.e., with side-boosters) configurations - I
forget the nomenclature: was that one called the "Titan 3" or...
The USAF's definitive concept was that Dyna-Soar would be launched by the
Titan IIIC, the first Titan with SRBs. Indeed, if you find a photo of an
early Titan IIIC on the pad, you'll see oval outlines on the sides of the
SRB nose caps -- those are the thrust-termination ports that would be used
to shut down the SRBs as Dyna-Soar fired its escape rockets for an abort.
(The ports were deleted when Dyna-Soar died and it became clear that the
IIIC would never fly manned.)
However, there were a number of alternatives to that in the early days.
Originally the USAF had hoped to fly Dyna-Soar on Titan II. When people
started having doubts about that, well, there was already an even bigger
rocket in the works, so flying on Saturn made sense.
There were some technical issues; in particular, the thrust of the Saturn
second stage, as originally conceived, was really rather too low for a big
heavy payload, and the result was a fairly inefficient trajectory. But
the *big* snag was that the USAF's hot new toy would be flying on a rocket
that would have to be bought through NASA, and that just wouldn't do.
Despite some early rhetoric about short-notice launch and such, the real
driving requirement for Titan IIIC was to be a Saturn-class launcher that
said "USAF" on the side, rather than "NASA".
Losing Dyna-Soar as a payload actually benefitted the Saturns quite
significantly. The S-IB first stage of the Saturn IB was an S-I stage
with a substantial tank stretch, which nevertheless had a dry mass eleven
tons *less* than the S-I. Part of that was detail improvements based on
S-I experience, but about half the total mass loss was lighter structure,
mostly as a result of losing two difficult payloads: Dyna-Soar and RIFT
(a suborbital nuclear-rocket flight test). Not only was Dyna-Soar rather
heavy, but its wings created nasty side loads when hit by high-altitude
winds, so the worst-case bending moments went down considerably when it
was crossed off the manifest.
... I think all the Gemini RCS/OMS motors burned N2O4 with "50-50" (like
the Titan 2 itself), didn't they?
As Chris has already posted, no, both the Gemini propulsion systems burned
N2O4/MMH. 50-50 is more or less the poor man's MMH: somewhat similar
properties, and not quite as good, but a lot cheaper to make.
Henry
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