Re: Brute force re-entry
From: John W. Landrum (jwlandrum_at_aol.computer.retro.com)
Date: 08/25/04
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To: <sci-space-tech@moderators.isc.org> Date: 25 Aug 2004 11:21:38 GMT
In article <Pine.LNX.4.44.0408190938590.28902-100000@uurth.com>, Alcore
<alcore@uurth.com> writes:
>
>I think the basic idea here is that there is a *lot* of energy being shed
>by steep re-entry... and if there's enough energy to heat the air blasting
>past the spacecraft into a plasma, is doesn't *seem* like so much of a
>stretch to try and use some of that energy to alter the spacecraft
>trajectory upwardly... in order to deliberately remain in the thinnest air
>possible or even deflect completely outside the atmosphere briefly.
>Which in turn, should reduce the heat loading. (Or at least stretch out
>the heat loading over a long enough period of time to allow some scheme to
>manage it more efficiently.)
>
The Shuttle's angle of attack in the initial reentry thru max heating and I
believe all the way thru max-Q (dynamic pressure) is 30 degrees! With the
lousy lift to drag ratio associated with the high speeds in this phase of
reentry, it is hard to see how you could generate any more upward dynamically
than is alreadly being generated. However, If I understand the profile
correctly,
the deorbit burn places the craft in a trajectory with a perigee well within
the
upper reaches of the atmosphere, perhaps much more well within than is
strictly necessary. Rather than trying vainly to generate more up with the
wings,
perhaps the enlightened path to a more gentle reentry is to generate less down
with the deorbit burn.
At any rate, the reentry phase of the Shuttle is not really broke, and
doesn't
need to be fixed. It worked a gazillion times, and the one time it did not
work
was because a piece of a _new_ insulation material fell off of the ET and hit
the
wing, knocking part of the leading edge tiles off durring the _ascent_. The
new
insulation is broke and needs fixing or simply to go back to the old. The
reentry
works fine if you leave the tiles on. They are not just for show, they are
there
for a reason.
What the Shuttle needs, besides a new airline, is some small, incremental
improvements. Liquid flyback side boosters, rather than the dangerous, messy,
and operationally (rather than conceptually) complex solid ones. And make
the new Shuttles out of titanium rather than aluminum. Maybe a newer, lighter,
more sophisticated avionics package, stuff like that.
We need a stay-in orbit OTV, with a solar powered ion or plasma drive for
carrying unmanned payloads from LEO to higher.
A nice thing for smaller payloads launched with multistage rockets might
be
a small, ultralight high performance last stage which delivers a payload to
LEO.
The payload separates and the OTV transfers the payload to its operational
orbit.
Then it returns to transfer the light, empty top stage to a rendezvous with an
empty
Shuttle which has delivered a payload to orbit. The Canadarm slaps the upper
stage into the empty cargo bay, slam the bay doors shut and it returns to Earth
with the Shuttle to be reused. The weight and performance of upper stages has
a disproportional impact on the overall performance of a multistage delivery
system. You can afford to spend more on materials and fine tolerances if you
can reuse the vehicle. And in this case, you get it back without having to
design, build, or haul a reentry system. Just design the uppermost stage to
be as light as possible when empty, and to fit and attach in the Shuttle cargo
bay. The Shuttle's rated reentry cargo wieght capacity is over 14,000 kg,
almost half of it's rather large lifting capability prograde to LEO.
(Source: Illustrated Encyclopedia of Space Technology)
By way of comparison the Agena D 3rd stage of the Titan 23B is:
Weight: 7160 kg (15800 lb) - fueled
Empty Weight: 2300 lb (1045 kg) (Source http://en.wikipedia.org/wiki/Titan_23B)
Of course the Agena would not fit, but you get the idea.
Also, custom made ET substitutes could be quite a payload in their own
right. Skylab was a stretched Agena 3rd stage with fittings, what could be
engineered with an ET's volume and most of the Shuttle's ordinary cargo
capacity
as a mass budget for internal fittings, plumbing, etc?! Nothing this size has
ever been boosted to orbit in one piece or assembled. The Saturn V never did
it. The
biggest thing the Russians orbited was a mere Mir, which was much smaller than
Skylab, and an ET dwarfs both.
And use it as a truck, not a camper or a portible lab. Can we stop with
the
mission to planet Earth and the ants in orbit already? I hereby declare the
experimental phase of cislunar explorational phase over. Let the operational
phase of space development begin already! I would give an arm and a leg for a
quarter of the orbital lift that has been squandered on idiotic and
rerereredundant
experiments. In fact as a US taxpayer I effectively have, in vain! In the
space
age, "What goes up must come down" is a rule made to be broken. If those
hundreds of Shuttle missions had ascended with judiciciously selected
infrastructure, and returned with only personnel, we could have been well on
our
way to delivering lunar oxygen to LEO and looking to expand a lunar mining and
industrial base.
If launch expense is the cost driver, why are we squandering it? There is
a
short and obvious answer, the purpose of a bureaucracy is to spend money
without making waves. Yet one would think that the thickest heads among
them surely know why their agency exists, the goals and aspirations of those
without which their agency would not and should not exist. If they don't
personally believe in them the honest thing to do is seek more gainful and
meaningful employment in the IRS or the Department of Redundancy
Department. But I suppose this rant is redundant, as well, preaching to the
choir.<soulful sigh>
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- In reply to: Alcore: "Re: Brute force re-entry"
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