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Did Apollo do a burn prior to re-entry?



 
 
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  #1  
Old March 2nd 07, 09:24 PM posted to sci.space.history
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Default Did Apollo do a burn prior to re-entry?

to slow it down? It was going , what, about 25,000 MPH?

Or did it "crash" squarely enough into the atmosphere that it didn't
need to?
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  #4  
Old March 3rd 07, 09:39 PM posted to sci.space.history
Brad Guth[_2_]
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Default Did Apollo do a burn prior to re-entry?

"PP" wrote in message


to slow it down? It was going , what, about 25,000 MPH?

Or did it "crash" squarely enough into the atmosphere that it didn't
need to?


Coasting in from the moon's L1, being roughly 325,740 km away from
Earth, say passing through that nullification point at something better
than a km/s, you'd think that our return velocity prior to atmospheric
reentry would have become impressive, to say the least.

Too bad there's not a computer simulator for running off such complex
orbital mechanic stuff, such as in 3D animation format with the time
compressed at 60:1 or even 3600:1. Perhaps China or India can
accommodate such basic needs.
-
Brad Guth




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  #5  
Old March 3rd 07, 10:05 PM posted to sci.space.history
Henry Spencer
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Default Did Apollo do a burn prior to re-entry?

In article , wrote:
to slow it down? It was going , what, about 25,000 MPH?


No, no braking burn -- beefing up the heatshield to take a bit more heat
used far less mass than rocket braking would have.

Or did it "crash" squarely enough into the atmosphere that it didn't
need to?


Nothing "crash" or "square" about it -- a carefully-controlled entry at a
very shallow angle, using body lift to shape the path and hold the capsule
down in the atmosphere until it had lost enough speed that it wasn't going
to skip back out.
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  #6  
Old March 4th 07, 05:56 PM posted to sci.space.history
Brad Guth[_2_]
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Default Did Apollo do a burn prior to re-entry?

"Brad Guth" wrote in message
news:[email protected] .mailgate.org

Actually, the return from the moon had to be crossing the moon's L1 zone
at something better than 1 km/s, perhaps at 1.5 if not nearly 2 km/s,
and from that point on it would have been increasing in velocity as
being pulled towards Earth, giving it a rather spiffy orbital reentry
velocity that only a great deal of aerobraking could have managed to
have moderated that velocity down to the dull roar of being similar to
but still faster than the shuttle reentry velocity.

Is there any replicated proof that our NASA/Apollo wizards spent any
actual time within the moon's L1? (such as most of their time, as their
otherwise fully robotic portions of their mission went into lunar orbit)
-
Brad Guth


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  #7  
Old March 4th 07, 11:28 PM posted to sci.space.history
Pat Flannery
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Default Did Apollo do a burn prior to re-entry?



Henry Spencer wrote:
Nothing "crash" or "square" about it -- a carefully-controlled entry at a
very shallow angle, using body lift to shape the path and hold the capsule
down in the atmosphere until it had lost enough speed that it wasn't going
to skip back out.


Which brings up the question: What would happen if it did skip off the
atmosphere?
Does it go into some odd orbit around Earth, or does it go clean out of
orbit and into solar orbit?

Pat

Pat
  #8  
Old March 4th 07, 11:41 PM posted to sci.space.history
John[_3_]
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Default Did Apollo do a burn prior to re-entry?

On Mar 4, 6:28 pm, Pat Flannery wrote:
Henry Spencer wrote:
Nothing "crash" or "square" about it -- a carefully-controlled entry at a
very shallow angle, using body lift to shape the path and hold the capsule
down in the atmosphere until it had lost enough speed that it wasn't going
to skip back out.


Which brings up the question: What would happen if it did skip off the
atmosphere?
Does it go into some odd orbit around Earth, or does it go clean out of
orbit and into solar orbit?

Pat

Pat


Pat,

At the risk of sounding like a smart aleck, I think the answer is
yes . . . or perhaps more accurately, it depends. It probably
depends on the angle at which the reentry had been attempted, vechicle
velocity, and the weight of the vehicle, which increased as more and
more samples were brought back. I suspect that it would be a funny-
shaped earth orbit, but maybe someone more proficient at orbital
mechanics can tell us for sure.

Take care . . .

John

  #9  
Old March 4th 07, 11:53 PM posted to sci.space.history
Pat Flannery
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Posts: 18,466
Default Did Apollo do a burn prior to re-entry?



John wrote:
Pat,

At the risk of sounding like a smart aleck, I think the answer is
yes . . . or perhaps more accurately, it depends. It probably
depends on the angle at which the reentry had been attempted, vechicle
velocity, and the weight of the vehicle, which increased as more and
more samples were brought back. I suspect that it would be a funny-
shaped earth orbit, but maybe someone more proficient at orbital
mechanics can tell us for sure.

Take care . . .

John



I can picture it losing enough velocity that it travels outbound from
the Earth to a very high altitude, stops, and then falls straight into
the atmosphere and burns up.

Pat
  #10  
Old March 5th 07, 12:09 AM posted to sci.space.history
Henry Spencer
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Posts: 2,170
Default Did Apollo do a burn prior to re-entry?

In article ,
Pat Flannery wrote:
...using body lift to shape the path and hold the capsule
down in the atmosphere until it had lost enough speed that it wasn't going
to skip back out.


Which brings up the question: What would happen if it did skip off the
atmosphere?
Does it go into some odd orbit around Earth, or does it go clean out of
orbit and into solar orbit?


Yes. :-)

If I recall correctly, under the right/wrong conditions, it was barely
possible for a very shallow skip to end up in solar orbit. Orbits with
apogee near the Moon are not that strongly bound to Earth, and can end up
escaping when the three-body dynamics work out just so.

Far more likely, though, given that there would be *some* loss of energy
even in a skip, was a high elliptical orbit around Earth. Typically this
would encounter the atmosphere again, but long after the CM's consumables
were exhausted, so the difference wasn't too significant to the crew. :-)
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |
 




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