Space Shuttle.

On Dec 29, 1:27 am, "Oz Lander" wrote:
Bob Noel wrote:
In article ,
"Oz Lander" wrote:

Why does the shuttle have to be travelling so fast to re-enter the
atmosphere?

How do you propose to slow the shuttle down from orbital velocity?

That I guess answers my question then. I was not aware that such high
speeds were required to just stay in orbit. What would it take to slow
the shuttle down whilst in orbit, enough to allow it to re-enter at a
slower speed?


Orbital velocity is about 8km/s I think. That's what all that fuel is
for -to accelerate it to that speed and raise it to orbital height.
Most fuel is burnt just lifting fuel... Getting down is a fine
balance, too fast (steep) and the shuttle can't dissipate it's energy
as radiated heat and it will burn up. Too slow (shallow) and it is
likely to skip off the atmosphere which will then rob the shuttle of
energy and lead to a very steep descent the next time it comes down
(and it will as it does not have escape velocity). At least that's how
I understand it.

Cheers

Wolfgang Schwanke wrote:
"Oz Lander" wrote in
:

What would it take to slow
the shuttle down whilst in orbit, enough to allow it to re-enter at a
slower speed?

The same amount of fuel that was needed to accelerate it in the first
place, plus lots more to get that extra fuel up. To avoid all that,
spacecraft use the atmosphere for braking. They've been doing that
since the beginning of manned spaceflight, it's not specific to the
shuttle. They just accept the risk associated with that method as a
tradeoff against the extra complication of carrying those enormous
masses of fuel all along.

Regards



They could aero-brake from orbit slower but it would take
forever. If they launched an unmanned fuel source, docked
and then transfered fuel it could be done.

Keep it simple the new Orion(Apollo on steroids) will work
just fine. The Russians have done a good job with safe and
repeated journeys from orbit

"WolfRat" wrote

They could aero-brake from orbit slower but it would take forever.

Not really. If you slow down gradually, the effect of gravity takes hold,
and you start falling faster. Mush of the speed is picked back up in that
manner.

If they launched an unmanned fuel source, docked and then transfered fuel
it could be done.

You still have to pay to get all of that fuel up there. That is not cheap,
let alone the fueling station cost, and the weight to get that up there.

Keep it simple the new Orion(Apollo on steroids) will work just fine. The
Russians have done a good job with safe and repeated journeys from orbit.

I would have more of a warm fuzzy feeling, if that were true. The Russians
have lost a couple crews on the whole re-entry landing procedure, I believe.
At least one, I am positive.

The Orion will be/should be more reliable, because of more simplicity, and
the fact that it will be above the whole rocket, and the fact that it does
not need to be made reusable.
--
Jim in NC

On Fri, 28 Dec 2007 13:53:06 -0500, "Morgans" wrote:

Keep it simple the new Orion(Apollo on steroids) will work just fine. The
Russians have done a good job with safe and repeated journeys from orbit.

I would have more of a warm fuzzy feeling, if that were true. The Russians
have lost a couple crews on the whole re-entry landing procedure, I believe.
At least one, I am positive.

Soyuz 1 and Soyuz 11. The first due to a parachute failure, the second due to
failure of a valve.

http://en.wikipedia.org/wiki/Soyuz_1

http://en.wikipedia.org/wiki/Soyuz_11

Ron Wanttaja

WolfRat wrote:
Wolfgang Schwanke wrote:
"Oz Lander" wrote in
:

What would it take to slow
the shuttle down whilst in orbit, enough to allow it to re-enter at a
slower speed?

The same amount of fuel that was needed to accelerate it in the first
place, plus lots more to get that extra fuel up. To avoid all that,
spacecraft use the atmosphere for braking. They've been doing that
since the beginning of manned spaceflight, it's not specific to the
shuttle. They just accept the risk associated with that method as a
tradeoff against the extra complication of carrying those enormous
masses of fuel all along.

Regards



They could aero-brake from orbit slower but it would take
forever. If they launched an unmanned fuel source, docked
and then transfered fuel it could be done.

And put it in what and do what with it?

It took the jettisoned external tanks and engines to provide the
energy to get up in the first place and would take an equivelant
amount of energy to kill all your velocity and energy of position
in orbit to get down slowly.

--
Jim Pennino

Remove .spam.sux to reply.

The same amount of fuel that was needed to accelerate it in the first
place, plus lots more to get that extra fuel up.

Actually not the same amount...not even close. You only have to lower
the perigee such that you reenter on the proper trajectory whereas
going up you have to get into a circular orbit

Ron Lee

Ron Lee wrote:

The same amount of fuel that was needed to accelerate it in the first
place, plus lots more to get that extra fuel up.

Actually not the same amount...not even close. You only have to lower
the perigee such that you reenter on the proper trajectory whereas
going up you have to get into a circular orbit

How do you get rid of all the velocity than builds up as you decend
through near vacuum and your energy of postition becomes energy of
motion?


--
Jim Pennino

Remove .spam.sux to reply.

wrote:
How do you get rid of all the velocity than builds up as you decend
through near vacuum and your energy of postition becomes energy of
motion?

Yes potential energy becomes kinetic energy and that is taken care of
by friction during reentry.

Ron Lee

Ron Lee wrote:
wrote:
How do you get rid of all the velocity than builds up as you decend
through near vacuum and your energy of postition becomes energy of
motion?

Yes potential energy becomes kinetic energy and that is taken care of
by friction during reentry.

And thus we have come full circle and forgotten the original question,
which was why does the shuttle have to land so fast.


--
Jim Pennino

Remove .spam.sux to reply.

wrote in message
...
Ron Lee wrote:
wrote:
How do you get rid of all the velocity than builds up as you decend
through near vacuum and your energy of postition becomes energy of
motion?

Yes potential energy becomes kinetic energy and that is taken care of
by friction during reentry.

And thus we have come full circle and forgotten the original question,
which was why does the shuttle have to land so fast.


--

We are certainly getting better at dragging discussions off topic. In the
old days it used to take as much as a hundred posts to come full circle, but
today we can accomplish it in as little as dozen or so.

People that live in reality have things like "speed dating", here we are
limited to things like "speed drifting".