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From: Henry Spencer <>
Subject: Re: Dyna-Soar (was Re: What would it have taken to go...)
Date: Mon, 1 Dec 1997 01:50:32 GMT

In article <>,
Bev Clark/Steve Gallacci <> wrote:
>The one thing the X-20 would have done of inportance would be was fly the
>profile. Even if everything on it was off the shelf and its creation
>contributed nothing to the data base, flying the missions would have
>answered a ton of questions on hypersonic flight and such...

True, which is why such profiles *were* flown -- by unmanned research
programs such as ASSET and PRIME.  If all you want to do is fly reentry
profiles, and you can tolerate a lost vehicle or two, there's no great
need to have a crew on board.  Mind you, it *would* have been useful to
elaborate on this, flying a wider range of profiles more times, because
the unmanned programs missed things (e.g., the "potholes in the sky"
phenomenon the shuttle discovered -- large variations in the density of
the extreme upper atmosphere, which have serious implications for
aerocapture and such).

Whether it was better to fly such an expanded program with a manned
suborbital research aircraft like X-20 or with unmanned suborbital drones
like ASSET and PRIME is harder to call.  Either version would have been
costly because of the expendable boosters.  X-20 would have been more
reliable -- more likely to come home for re-use -- but would have needed a
bigger booster.  Note that orbital capability was irrelevant to this
mission; the X-20 as planned was massively overbuilt for this role, and
far too expensive as a result.

(Spaceplanes in general have a history of being billed as research
aircraft, but also of being massively overbuilt for that role because of
hidden or not-so-hidden agendas.  This is part of why so few of them have
actually flown; there's a limit to what people are willing to pay for a
research aircraft.)

>Ultimately, the X-20 would have likely been a much better sceince and
>space work platform, as it was designed for just that, rather than the
>expediant delivery systems of the capsules.

I find this statement curious -- it's the sort of thing that makes me call
people "Dyna-Soar worshippers" -- because Gemini and Apollo were most
certainly designed as science and space work platforms.  Indeed, in many
ways they were better for it than Dyna-Soar -- e.g., better views from the
windows -- because they were largely free from Dyna-Soar's aerodynamic
constraints.  (Remember that Apollo, in particular, was originally
designed as a general-purpose manned orbital spacecraft without reference
to the special needs of a lunar landing.)

The only thing that was "expedient" about the capsules was that they
didn't deliberately do everything the hard way just for the sake of doing
it that way.  They chose the simplest and cheapest way to get into space,
operate there, and come home, regardless of its lack of ideological
purity.  The technical term for this is "good engineering".
If NT is the answer, you didn't                 |     Henry Spencer
understand the question.  -- Peter Blake        |

From: (Henry Spencer)
Subject: Re: Dynasoar
Date: Sun, 2 May 1999 01:43:26 GMT

In article <>,
Kleekamp <> wrote:
>Why was the Air Force Dynasoar project, an early shuttle design, canceled?

Dyna-Soar was *not* an early shuttle; it was just a spacecraft with wings,
which had to be launched on top of a (large) expendable booster.  It was
killed because it was a difficult and expensive project, which was making
very slow progress, at a time when the USAF's case for military manned
spaceflight was looking poorer and poorer as unmanned spysats got better
and better.

A contributing factor was that the semiballistic capsules -- notably
Gemini -- were much easier to develop and could be launched on smaller
rockets, making Dyna-Soar look like a poor way to proceed even if one did
need manned military space missions.  Dyna-Soar was cancelled after six
years and $400M, still at least three years and another $400-600M away
from its first flight.  Gemini went from design sketches to flight in a
little over three years for about $600M, and was a considerably more
capable spacecraft in most ways.
The good old days                   |  Henry Spencer
weren't.                            |      (aka

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