Newsgroups: sci.space.policy
From: henry@spsystems.net (Henry Spencer)
Subject: Re: New Venturestar Layout
Date: Sun, 26 Mar 2000 01:50:59 GMT

In article <8bg203$sd1$1@nnrp1.deja.com>,  <dave_salt@my-deja.com> wrote:
>> SSTO-class structures
>> have been built for many years: the Titan II first stage, the Saturn V
>> second stage, the shuttle ET, etc...
>
>The question is, however, could these structures form the basis of a reusable
>vehicle?

While Dave has a valid point -- you need to think about recovery loads and
number of cycles -- I will point out that much of the supposed gap between
expendable and reusable vehicles is illusory here.  The "expendable" ones,
especially the ground-test copies of them, in practice have to be built to
take *many* operational cycles just to get through the test programs.
Other than solid rocket motors and ablative heatshields, very few items of
"expendable" hardware are truly one-shot devices.

>But weight-growth control can be made more difficult if the original design
>is bad. My understanding is that part of the secret of the A4's success was
>that all of the key technical question marks had been effectively resolved
>before full development started, so the management of its weight-growth was
>far less of a challenge than, say, X-33.

I think that's true... but that is how a development program (as opposed
to a research program) is supposed to be run.  There was plenty of hassle
with the details -- the A-4 could easily have grown a lot of extra weight
if management hadn't been utterly determined that it was not allowed --
but it is true that only quite small technical snags were found with the
basic design.

(Incidentally, Ed Heinemann, chief engineer for the Skyhawk and the author
of its weight-management approach, knew Wernher von Braun... and considered
von Braun's weight-management policies rather sloppy.)

Also, do note that the resolution of the technical uncertainties didn't
mean that everybody agreed that the quoted weight was possible!  Heinemann
had a lot of trouble convincing people that he really meant what he said
and that his approach was credible; despite his long track record, there
was no shortage of technically-competent people who thought he was crazy.
To quote Bill Gunston:

	Today the Skyhawk is so familiar that it is hard to comprehend
	that experienced Navy staff were genuinely convinced it could
	never be built.

>> A modest price to pay just to avoid having to design two rockets where one
>> will do.
>
>However, this does not apply to all TSTO concepts. The Siames (Biamese?)
>concept would, if applied in the strictest sense, consist of two identical
>vehicles...

That's true.  My apologies, Dave -- I keep forgetting your pet TSTO
concept. :-)
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.policy
From: henry@spsystems.net (Henry Spencer)
Subject: Re: New Venturestar Layout
Date: Tue, 28 Mar 2000 19:44:15 GMT

In article <8bqo2uINNs4i@subds.rzg.mpg.de>,
Bruce Scott TOK <bds@rzg.mpg.de> wrote:
>>	Today the Skyhawk is so familiar that it is hard to comprehend
>>	that experienced Navy staff were genuinely convinced it could
>>	never be built.
>
>Was it simply back to normal afterward, as the F-4, F-14, F-15 and
>successors are quite heavy planes?

Pretty much.  Heinemann unfortunately never got the chance to apply his
from-scratch lightweight-design approach to a fighter, mostly because of
the luck of the draw on funding and his departure from active aircraft
design in the late 1950s.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.policy
From: henry@spsystems.net (Henry Spencer)
Subject: weight control (was Re: New Venturestar Layout)
Date: Wed, 29 Mar 2000 15:00:55 GMT

In article <38E1490A.C3110608@primary.net>,
James A Davis  <jimdavis2@primary.net> wrote:
>> >Was it simply back to normal afterward, as the F-4, F-14, F-15 and
>> >successors are quite heavy planes?
>
>The Northrop F-5, F-5E, and F-20 and the GD F-16 were American efforts
>(largely successful) in the lightweight fighter field.

Well, sort of.  Note that it *was* back to normal for the US, as there was
never any very serious possibility of the USAF buying the F-5, F-5E, or
F-20 -- they were built for export, and suffered even there from the
perception that they were second-rate aircraft.  Much later, the F-16 had
to be jammed down the USAF's throat (and the production F-16 was rather
heavier and more complex than the prototype YF-16).

>> Pretty much.  Heinemann unfortunately never got the chance to apply his
>> from-scratch lightweight-design approach to a fighter...
>
>Actually, Heinemann did direct the design of the Douglas F4D Skyray and
>F5D Skylancer fighters in the '50s.

The Skyray was a late-40s aircraft -- first flight, somewhat delayed, at
the beginning of 1951 -- and came before Heinemann's lightweight-design
approach was well developed.  The Skylancer was a Skyray derivative,
substantially reworked but not a from-scratch design.

Heinemann's original lightweight-design concept was for a fighter, and
you can get some idea of what might have been by considering that it was
a missile-armed interceptor with a gross takeoff weight of 8,000 pounds!
(A current F-16 weighs twice that much *empty*.)  It had a thrust:weight
ratio exceeding 1:1, not unusual today but quite something with early-50s
jet engines.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)