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Did Apollo do a burn prior to re-entry?



 
 
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  #11  
Old March 5th 07, 12:46 AM posted to sci.space.history
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Default Did Apollo do a burn prior to re-entry?



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.


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

I hate the word "skip". Makes it sound like the atmosphere gives it
some sort of push back up. In fact, of course, the atmosphere just
slows it down, and if not enough, then the ship's speed is enough to
allow it to increase it's distance from the earth. I presume it would
go into some highly eccentric orbit, and re-enter the atmosphere
perhaps the next few passes, depending on how far outside the re entry
window they were.
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  #12  
Old March 5th 07, 12:51 AM posted to sci.space.history
Hyper
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Default Did Apollo do a burn prior to re-entry?

On Mar 5, 1:53 am, Pat Flannery wrote:
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


The heat shield would have withstood 2 additional reentries (skip
+final), but I don't know whether the oxygen whould have run out or
not.
Anyone care to enlighten me regarding O2 supplies on Appolo?

  #13  
Old March 5th 07, 01:53 AM posted to sci.space.history
robert casey
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Default Did Apollo do a burn prior to re-entry?



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?


It wouldn't make solar orbit, but it might bounce into a long looping
orbit that would return it to the upper atmosphere a day or two later.
Bad news for the astronauts, as the command module only has supplies
and oxygen that lasts for only a few hours.
  #14  
Old March 5th 07, 01:56 AM posted to sci.space.history
robert casey
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Default Did Apollo do a burn prior to re-entry?

Hyper wrote:

On Mar 5, 1:53 am, Pat Flannery wrote:

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



The heat shield would have withstood 2 additional reentries (skip
+final), but I don't know whether the oxygen whould have run out or
not.
Anyone care to enlighten me regarding O2 supplies on Appolo?

Only good for a couple of extra hours. You really don't want to skip
off the atmosphere. This assumes that the capsule doesn't flip around
and expose the top part to the searing reentry heat.
  #15  
Old March 5th 07, 02:38 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 .com,
Hyper wrote:
The heat shield would have withstood 2 additional reentries (skip
+final), but I don't know whether the oxygen whould have run out or
not.
Anyone care to enlighten me regarding O2 supplies on Appolo?


Power, cooling, oxygen, etc. all were good for only a few hours after
separation from the SM.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |
  #16  
Old March 5th 07, 03:15 PM posted to sci.space.history
Pat Flannery
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Default Did Apollo do a burn prior to re-entry?



wrote:
I hate the word "skip". Makes it sound like the atmosphere gives it
some sort of push back up.


Actually that's what happens.
The CM was designed to generate lift on the atmosphere as it came in, by
angling its heat shield so it wasn't face-on into the airstream:
http://content.answers.com/main/cont...-Apollo_cm.jpg
Originally the intention was to have it hit the atmosphere, and skip out
again as it lost velocity, then do its final reentry.
This plan got ditched, and what it ended up doing was using its lift to
extend its reentry's length while staying in the upper atmosphere to
decrease G forces:
http://www.nasm.si.edu/collections/i...RES/Fig22d.jpg
The Soviet Zonds returning from looping the Moon on the other hand did
use a lifting skip reentry technique that had the spacecraft bounce out
of the atmosphere and then do a second reentry.
And it was some bounce... it would ether come in over Antarctica and
then do its final reentry over the Indian Ocean for a water landing, our
come in over the U.S. and then fly over the Arctic for a ground landing
in the Soviet Union.
So both sides owed a little something to Eugene Sanger and his Antipodal
Bomber idea that used atmosphere skipping to increase range, although in
this case the idea was to decrease G loads.

Pat
  #17  
Old March 6th 07, 01:36 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:
So both sides owed a little something to Eugene Sanger and his Antipodal
Bomber idea that used atmosphere skipping to increase range, although in
this case the idea was to decrease G loads.


Although range was part of it, too -- the reason you do the full
Zond-style skip, rather than the less drastic Apollo reentry, is if you
really need to stretch the reentry out, to get somewhere that a normal
reentry can't reach. Apollo dropped the skip partly because it also
dropped its original requirement for a landing in the continental US.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |
  #18  
Old March 6th 07, 02:48 AM posted to sci.space.history
Pat Flannery
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Posts: 18,466
Default Did Apollo do a burn prior to re-entry?



Henry Spencer wrote:
Apollo dropped the skip partly because it also
dropped its original requirement for a landing in the continental US.


I've never seen a drawing of it, but I once ran into a mention of a
Rogallo wing equipped Apollo.

Pat
  #19  
Old March 6th 07, 04:49 AM posted to sci.space.history
Charles Buckley
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Default Did Apollo do a burn prior to re-entry?

Pat Flannery wrote:


Henry Spencer wrote:
Apollo dropped the skip partly because it also
dropped its original requirement for a landing in the continental US.


I've never seen a drawing of it, but I once ran into a mention of a
Rogallo wing equipped Apollo.


Would not be surprised as Rogallo wings were the original idea
for Gemini. My guess is that you are talking about a later
block of Apollo capsule. Maybe a design concept from about 1967-69
for Apollo upgrades?

  #20  
Old March 6th 07, 05:05 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:
Apollo dropped the skip partly because it also
dropped its original requirement for a landing in the continental US.


I've never seen a drawing of it, but I once ran into a mention of a
Rogallo wing equipped Apollo.


There were a number of ideas for just how to bring an Apollo down on land,
and if you read early Apollo papers, you can find details and even some
test results -- for example, there was substantial testing done on braking
rockets for touchdown.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |
 




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