Brute force re-entry

Early on in the space program, the space capsule used brute force re-entry.
IE: it slammed into the upper atmosphere at high speed to slow down for
return.
The space shuttle is a lifting body.
Why can't it fly back???
If the shuttle hit the atmosphere slower, use aero braking and descend at
a shallower angle, the shuttle could return at a slower decent rate, and not
be subjected to the high temptures.



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The space shuttle is a lifting body.
Why can't it fly back???
Because nasa designed it as a Mack truck with little wings instead of going
with the ultralight Rogallo Wing re-entry vessel.
The wing loading is so high that the shuttle is a brute force reentry vessel
with a glide path.
For CATS, a real glider, with low wing loading, will reenter slower and
cooler after using engine braking. It doesn't have to be so hard, it's just
that nasa never does anything nice and easy, there's no money in it.
^
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~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

Allen Meece wrote:
[...]
Because nasa designed it as a Mack truck with little wings instead of
going with the ultralight Rogallo Wing re-entry vessel.

Has anyone ever flown or even designed a workable hypersonic waverrider or
other exotic wing vehicle? Every so often I hear about them, and the sound
really great (and look *amazingly* cool), but they never seem to get off
the ground...

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On Wed, 11 Aug 2004 02:20:48 GMT
"Lizerd" wrote:

Early on in the space program, the space capsule used brute force
re-entry. IE: it slammed into the upper atmosphere at high speed to
slow down for return.
The space shuttle is a lifting body.
Why can't it fly back???
If the shuttle hit the atmosphere slower, use aero braking and descend
at a shallower angle, the shuttle could return at a slower decent
rate, and not be subjected to the high temptures.

It can't "hit the atmosphere slower" without first slowing down, and to do that it has to aerobrake. All other ways of reducing velocity are just too expensive in terms of mass.
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"Lizerd" wrote in message
...
Early on in the space program, the space capsule used brute force
re-entry.
IE: it slammed into the upper atmosphere at high speed to slow down for
return.

That's a fairly accurate description.

The space shuttle is a lifting body.
Why can't it fly back???

Because it first needs to shed most of it's orbital velocity before it can
"fly". That means a re-entry very similar to that flown by capsules (a very
high angle of attack that generally presents the bottom of the orbiter to
the worst of the air flow instead of the nose). Once the speed is low
enough, the shuttle lowers the angle of attack and transitions to gliding
flight.

If the shuttle hit the atmosphere slower, use aero braking and descend at
a shallower angle, the shuttle could return at a slower decent rate, and
not
be subjected to the high temptures.

How exactly would you propose to shed this extreme orbital velocity?

Jeff
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Michael Smith wrote:
(Allen Meece) wrote:

Because nasa designed it as a Mack truck with little wings instead of
going with the ultralight Rogallo Wing re-entry vessel.

The Rogallo Wing is a modified parachute. It was developed as a
steerable recovery system for Gemini before finding a use as a hang
glider wing. It has no role in reentry.

No role? It could have a role in civilian CATS [cheap access to space]
vessel reentry. The reason nasa didn't go with it was because it was too
slowly developing a folding/deployment system for the wing and it was holding
the Gemini program back. It wasn't meeting the program's schedule.
So there you go. Institutional priority results in bad technology.

What Michael means is that the Rogallo wing can be deployed at low
speeds, as in the final landing phases of a return from orbit, but not
at the hypersonic speeds Gemini (and the Shuttle) experienced during
"entry interface" and the upper atmosphere. It would be a major
engineering challenge to develop a deployable structure of significant
span that *could* take hypersonic speeds -- we're having enough trouble
with fixed structures.

/dps

It would be a major
engineering challenge to develop a deployable structure of significant
span that *could* take hypersonic speeds -- we're having enough trouble
with fixed structures.
But how do we know that? Especially since it depends on the flight profile.
Look, there's hypersonic speed in the atmosphere where the air is dense and
there's hypersonic speed in the stratosphere where there are scattered
molecules. There's no reason why a well-designed Rogallo Wing would not deploy
in the stratosphere, and provide lift for a slow descent.
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

Isn't the quantity of energy being shed going from orbit to ground the
same regardless of the angle of reentry? The energy to be shed is
determined by the orbit and the spacecraft mass right
True, Brute force reentry sheds it faster with a steep plunge while the
elegant lifting body approach is to shed the same energy over a longer time
using suitable heat radiators, flying and skipping rather than diving.

Incorrect. The space shuttle re-enters at a flight path angle typically
between -1 and -1.5 degrees. That's hardly "steep".
Also incorrect. The shuttle's flight path angle in the atmosphere is 20 --
25 degrees.
You're thinking about the initial orbital departure angle, not the average
sink rate along the entire descent.
The shuttle's reentry path IS STEEP. It is a high wing-loading, controlled
brute force reentry. Hardly as graceful as a good lifting body like the
cancelled [!?] X-38 would do.
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

(Allen Meece) wrote in
:

Incorrect. The space shuttle re-enters at a flight path angle
typically
between -1 and -1.5 degrees. That's hardly "steep".
Also incorrect. The shuttle's flight path angle in the atmosphere
is 20 --
25 degrees.
You're thinking about the initial orbital departure angle, not the
average
sink rate along the entire descent.

No, the number I quoted was for EI, not "initial orbital departure angle."
The average sink rate along the *entire* descent is irrelevant if we're
talking about entry, which is only the first part of the descent. During
*entry* the shuttle's flight path angle remains quite shallow, close to the
EI flight path angle I quoted. The flight path angle doesn't come anywhere
close to -20 until TAEM, which is well after entry.

The shuttle's reentry path IS STEEP. It is a high wing-loading,
controlled
brute force reentry. Hardly as graceful as a good lifting body like
the cancelled [!?] X-38 would do.

Incorrect. The shuttle has a much higher hypersonic L/D (4.0) than the X-38
(1.4).


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