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.



--
(All advice is checked, re-checked and verified to be questionable....)

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.
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

In article ,
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.

That is the only method anyone has ever used for reentry, from that day
to this: atmospheric braking. The details have gotten fancier (in most
cases), but the basic scheme of things has not.

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

It does. The Apollo and Gemini capsules were lifting bodies too, by the
way (and so is Soyuz). They all use aerodynamic lift to stretch their
reentries out as much as they can. But there are severe fundamental
limits to what can be done. Even pushing it as far as the shuttle orbiter
does incurs serious penalties, notably a thermal protection system which
is complicated and rather fragile compared to the simple and robust
heatshields the capsules used.

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.

The longer, slower reentry the shuttle uses makes its thermal problems
*worse*, not better. The prolonged baking is actually rather harder to
handle than a quick blowtorching.

In any case, this isn't a question of the shuttle being deliberately
operated in some stupid, suboptimal way. It *already* uses aerodynamic
lift as much as it can without melting something off.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

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.
--
Michael Smith
Network Applications
www.netapps.com.au | +61 (0) 416 062 898
Web Hosting | Internet Services

"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
--
Remove icky phrase from email address to get a valid address.

Lizerd wrote:

Brute force re-entry

I wouldn't have expected using the atmosphere to slow you down would be
considered using a 'brute force' method of slowing down. I would think
it would be considered elegant, and spending fuel to slow down or just
running directly into the planet at full speed would be consider the
brute force approaches.

http://science.ksc.nasa.gov/shuttle/...s/gidefinl.pdf

Here's some information on what goes into reusable spacecraft design.

http://www.astronautix.com/lvs/shuenara.htm

Here's a picture of an alternative to the Shuttle, that in my
estimation would have been better than the Shuttle's present delta
wing.

An even better version would have been a slender cylinder with
straight wings deployed at subsonic speeds. Think of a tomahawk
cruise missle. This was proposed for the Russian PKA

http://www.friends-partners.org/part.../craft/pka.htm

VonBraun planned to recover his boosters with a parachute solid rocket
combination. The booster would slow after cutoff. Then, at terminal
speed, a chute would deploy. Finally, a solid rocket assembly would
bring the booster to a safe touchdown.

I like the idea of a 7 element vehicle that consists of 7 cylinders -
each with tomahawk style deployable wings. Each with appropriate
thermal protection for its speed regime. Each with a LOX/LH RL10
based pump system - aerospike engine.

The 7 cylinders operate together at lift off. They drain four of the
7 - feeding all 7 with cross feeding. The four detach and three
continue on. Two of the three remaining are drained to feet the three
remaining. These detach when they're empty. Finally, the one
continues on to nearly orbit. A small kick stage circularizes the
orbit aboard the payload. All 7 elements return to Earth and
re-enter, then deploy wings when subsonic speed is achieved. An
aircraft loitering downrange near the impact point of each cylinder,
snags it Corona capsule fashion, except here the 'capsule' has a
shallower glide slope since its using wings and not parachutes, and a
GPS system in both the plane and the 'capsule.'

The winged cylinders glide back to be snagged by planes loitering at
predetermined locations. The gliders are towed back to the launch
center and released - to be reused.

http://www.globalsecurity.org/space/systems/corona.htm



(Henry Spencer) wrote in message ...
In article ,
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.

That is the only method anyone has ever used for reentry, from that day
to this: atmospheric braking. The details have gotten fancier (in most
cases), but the basic scheme of things has not.

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

It does. The Apollo and Gemini capsules were lifting bodies too, by the
way (and so is Soyuz). They all use aerodynamic lift to stretch their
reentries out as much as they can. But there are severe fundamental
limits to what can be done. Even pushing it as far as the shuttle orbiter
does incurs serious penalties, notably a thermal protection system which
is complicated and rather fragile compared to the simple and robust
heatshields the capsules used.

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.

The longer, slower reentry the shuttle uses makes its thermal problems
*worse*, not better. The prolonged baking is actually rather harder to
handle than a quick blowtorching.

In any case, this isn't a question of the shuttle being deliberately
operated in some stupid, suboptimal way. It *already* uses aerodynamic
lift as much as it can without melting something off.

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...

--
+- David Given --McQ-+ "There is one thing a man must do // Before his
| | life is done; // Write two lines in APL // And make
| ) | the buggers run."
+- www.cowlark.com --+ --- The Devil's DP Dictionary

On Sun, 15 Aug 2004, Bill Bonde ( ``Soli Deo Gloria'' ) wrote:

Lizerd wrote:

Brute force re-entry

I wouldn't have expected using the atmosphere to slow you down would be
considered using a 'brute force' method of slowing down. I would think
it would be considered elegant, and spending fuel to slow down or just
running directly into the planet at full speed would be consider the
brute force approaches.

I think the point that he was trying to make was that given the steep
angle of re-entry that NASA always uses, you might as well be "running
directly into the planet at full speed" instead of "skipping repeatedly
off the top of the atmosphere to shed speed".

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.)

Conceptually you might deliberately use a series of shrinking sub-orbital
skips to shed speed (while within the upper atmosphere) and then heat
(while above the atmosphere) in alternation until the final sub-orbital
entry *can't* be shaped back into a trajectory that climbs above the
atmosphere again.

All that plasma rushing by the outer skin of the spacecraft just seems
like an energy resources that just begs to be harnessed and manipulated.
(The phrase "Magneto-Hydrodynamic Boundary Layer Control" comes to mind.)

Gene Pharr
Slidell, LA



--
Alcore Nilth - The Mad Alchemist of Gevbeck

I have not been following this thread, so i apologize if it repeats or sends
down an different alley, but i saw it today, and the idea of a brute force
re-entry matced an informal (very) discussion I had and wanted to know if
the conclusion we came to was correct:

to do a real brute force reentry ie, one that does not utilize air
resistance to any significant degree (and therefore, main point, would NOT
require a heat sheild) would require a rocket as big as the one that put the
spacecraft in orbit, correct?

the next question would be, if you allowed air resistance for landing (wings
or parachute) but continued to insist on no heat sheild, how much smaller
could it be? Our idea/question was whether it would be theoretically
feasible to put a re-entry rocket in orbit that could be attached to any
craft with a damaged heat shield and could lower it into the atmosphere by
brute force expenditure of fuel.