Re: 1teraflops cell processor possible?

On 28 Nov 2003 01:17:59 -0800, [EMAIL PROTECTED] (George William
Herbert) wrote:

<snip>
>
>The reason for the wings configuration is crossrange on re-entry.
>High hypersonic lift to drag.  NASA wanted lower hypersonic L/D
>and lower crossrange; the DOD wanted higher crossrange so they could
>loft certain payloads into polar orbit and return to land in one
>orbit if they had to, and certain related mission issues.
>
>Fundamentally, again: if you're going to reuse the vehicle
>it has to land softly and to land softly it has to be
>able to land on specific points and at specific attitudes.
>Reusing a capsule which lands blunt end down on random
>soil may not be possible, even if you want to.
>Salt water is very hard on aerospace equipment.
>To reuse you need to either make very rugged equipment,
>or land it softly with wings or with rocket motors.
>

This isn't the place for a lengthy discussion, and I don't want to get
into an ugly flame war.  The sensible thing to do would be to shut up
and to allow you just to keep repeating the elaborate web of nonsense
that has surrounded the shuttle program from the very beginning.  I
just can't stand reading it and not responding because I've been
listening to the same arguments and thinking the same things for
decades:

1. The best way for the military to get its satellites into orbit is
with expendable launch vehicles.  That's what they've wound up doing
for the most part, anyway.

2. The idea behind reuse was that it was somehow supposed to save
money.  It hasn't, and in bucketsful.  Your argument comes down to: if
we had spent even more money, we could have saved money safely.  Reuse
is a maguffin (a plot device that holds the story together but that
isn't really central to the action, like the Maltese Falcon in the
Maltese Falcon).

3. There are three different missions: manned exploration of space,
putting satellites into orbit, and developing something like the
national aerospace plane.  The three missions got jumbled up among
different agencies with different agenda, and I suspect that Bill is
corrrect on this point: the desire to develop cutting edge technology
that would be useful in developing a military vehicle with
partial-orbit capabilities trumped everything else.

Since an aerospace plane with military capabilities was supposed to be
super-secret, the whole mess had to be sold some other way.  The way
it was sold was cost savings, and the programs as presented didn't
even pass the laugh test: dozens of launches a year with vehicle
turnarounds on the order of weeks.  If I'd had to present that kind of
BS with a straight face, I'd have had to go into the bathroom and puke
my guts out afterward.  

The idea of manned exploration of space got lost in the shuffle.  Or,
I should say, it got buried.  Putting human beings on the moon or on
Mars captured the public imagination.  Scientists argued (correctly)
that most of the scientific goals could be better satisfied with
unmanned deep space probes, and NASA has done a really good job of
pumping out colored photos as fast as it could.  

What did capture and what still does capture the public imagination
was putting human beings out there, but neither NASA nor anyone else
had any serious intention of pursuing such an objective because it
didn't satisfy any urgent national priority and it cost too much, and
the public was never told that the mission that really excited it had
essentially been abandoned.

What we were left with was an ill-conceived, high-risk program that
did successfully advance one objective: the program developed a
considerable amount of cutting-edge technology that *would* be useful
for a partial-orbit vehicle with a military mission.

I've misrepresented myself in one respect: I said I *am* an aerospace
engineer.  Not quite true, or at least misleading.  I left the
business in disgust over a decade ago at seeing how things really
worked.  Some people have the stomach for it, some don't.  I didn't.

As to what we will get going forward, we shall see.  If the congress
and NASA abandon winged vehicles and develop a capsule, feel free to
send me a gloating e-mail.  Everything I can discern says it isn't
going to happen.

RM

RM



>>  To reuse a large vehicle it has to be
>>> flown to a relatively low velocity pinpoint landing.
>>
>>Reuse may be over-rated (at least it certainly never operated to reduce
>>Shuttle costs below that of its non-reusable competition), or the definition
>>biased.  The only part of the system that usually needs to return to Earth
>>is the crew compartment, and reuse of that (minus its ablative shield)
>>should be relatively easy - especially if the landing uses water to cushion
>>the impact on the structure.
>
>Water immersion generally voids the warranty on most aerospace
>alloys.  Jets that skid off the runway into the ocean, even if they
>just get lightly soaked, are junked.  Same thing with capsules.
>Stainless steel may not be so subject to it, and Titanium isn't so 
>bad, but most capsule structures are aluminum.
>
>>Given the difficulty of putting mass into even low Earth orbit, putting any
>>more up there than is necessary seems silly.  The Shuttle structure not only
>>contains a large cargo bay (which usually returns to Earth empty) but also
>>its heavy and powerful main engines (and it must be strong enough to survive
>>their thrust) - neither of which is of much use once LEO has been attained.
>
>The engines still being along is a function of the rocket being a
>stage-and-a-half vehicle, not it being reusable.  Any single stage
>or stage-and-a-half rocket has the same problem, going back to
>the early Atlas rockets.
>
>The cargo bay is, in fact, not a major weight component of
>the overall shuttle structure.  
>
>The whole airframe, needed to return all the parts safely
>to the ground, *is* a major weight component... an expendable
>vehicle with the same basic technologies would save at least
>fifty tons over the shuttle's weight.
>
>>As long as propulsion systems and fuel dominate cargo capacity in launch
>>vehicles (exactly the reverse of the situation with general-purpose
>>aircraft), using purpose-built vehicles built up from standard (and, where
>>feasible, reusable) components rather than attempting to create
>>general-purpose, reusable vehicles at coarser grain seems to make much more
>>sense.
>
>Fuel is cheap.  If you ever build a rocket where the fuel bill
>is a noticable fraction of the launch cost, you will receive
>serious congratulations from the space launch community.
>
>Using nitrogen tetroxide is cheating, however.
>
>Propulsion systems are not cheap, however.
>
>We could go on ad infinitum about big dumb boosters;
>I happen to agree that they're a really good technology
>option at this place and time, but if the volume of
>launches increased by a factor of ten, as it might
>if costs dropped down to low hundreds of dollars per
>pound launched, then reusable vehicles will likely
>be a significantly more cost effective option from
>that point onwards.
>
>I say that as someone with man-years of so far unreimbursed
>engineering time into some BDB booster designs and tech
>analysis, plus two so far failed rounds of commercializing
>and capitalizing to get the full scale development program
>going to build one.  BDBs are great, until they succeed
>wildly, and then RLVs will win in the long run.
>I hope to help make that happen and make some money
>in the decade or so that it takes for that to happen,
>if I am lucky.
>
>
>-george william herbert
>[EMAIL PROTECTED]