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The Apollo moon landing missons?
Did the have to do a retro burn to slow down into lunar orbit? I
don't seem to remember any of the missions having done so. i.e. as you climb out of a gravity well in free space you loose speed, and as it took the LEM, command and service module the best part of a week to reach the moon from the 25,000mph departure speed they were slowing down all the time during the trip. Christopher +++++++++++++++++++++++++ "There's a light at the end of the tunnel" says the optimist. "It's probably a train coming stright at us" responds the pessimist. |
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The Apollo moon landing missons?
Christopher wrote:
Did the have to do a retro burn to slow down into lunar orbit? I don't seem to remember any of the missions having done so. Check again. They all did so on the far side of the Moon, which made for some harrowing times in Houston until AOS. Fortunately, they all went off without a hitch. The fact that the fuels were hypergolic, and that they could be used with a *very* simple (and therefore more failsafe) system helped. i.e. as you climb out of a gravity well in free space you loose speed, and as it took the LEM, command and service module the best part of a week to reach the moon from the 25,000mph departure speed they were slowing down all the time during the trip. Actually, no. They would pass a point in their trajectory that was a minimum between the Earth and the Moon (but closer to the latter); then they would speed up again. The Moon has gravity of its own, remember. -- -- With Best Regards, Matthew Funke ) |
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The Apollo moon landing missons?
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The Apollo moon landing missons?
Christopher wrote:
Did the have to do a retro burn to slow down into lunar orbit? I don't seem to remember any of the missions having done so. Indeed they did, but the orbit insertion burn had to take place above Lunar farside, where Earth communications were not possible. I clearly remember the first time it was done during Apollo 8. On the news coverage it was pointed out that if for some reason the burn didn't happen, the ship would come around the Lunar limb into line of sight in X number of minutes, if it was successful, they would emerge at a time several minutes later than that. And they did indeed re-establish contact at a time consistent with a normal insertion burn. |
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The Apollo moon landing missons?
"Christopher" wrote in message ... Did the have to do a retro burn to slow down into lunar orbit? I don't seem to remember any of the missions having done so. Yes they did. This was one of the two major burns required by the SPS on the CSM. (The TEI of course being the second.) i.e. as you climb out of a gravity well in free space you loose speed, and as it took the LEM, command and service module the best part of a week to reach the moon from the 25,000mph departure speed they were slowing down all the time during the trip. It took them approximately 3-4 days to reach the Moon. Not sure I'd call that the best part of the week. And once they reached the point where the Moon's gravity was stronger than the Earth's, they were accelerating. Christopher +++++++++++++++++++++++++ "There's a light at the end of the tunnel" says the optimist. "It's probably a train coming stright at us" responds the pessimist. |
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The Apollo moon landing missons?
Right, thanks for all the replys.
Christopher +++++++++++++++++++++++++ "Kites rise highest against the wind - not with it." Winston Churchill |
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The Apollo moon landing missons?
"Ian Stirling" wrote in message ... Christopher wrote: Did the have to do a retro burn to slow down into lunar orbit? I don't seem to remember any of the missions having done so. Yes. LOI, lunar orbit insertion. If this was not done, the whole stack would have gone round the moon, and been deflected back to earth. AIUI, it was called "free orbit return" or something. Free Return was a bit different. Apollos 8, 10,11 and I believe 12 all had a free return trajectory. If the the LOI had failed on the far side of the Moon, their return path would have intersected Earth and they could in theory land safely. Apollo 13 and above were schedued to land in areas such that when they went into orbit, it had to be from a trajectory other than a free return trajectory (the inclination was higher). As such if they had failed the LOI, they would have swung around to the Earth, but would not have intercepted it. By Apollo 13, they had enough confidence in the SPS (and fortunately the LM descent engine) that they went off the free return trajectory for the first time. After the accident, one of the first orders of business was to get them back on a free return trajectory. I believe they show this in the movie, but don't explain it. Searching on LOI Apollo should bring yhou more info. i.e. as you climb out of a gravity well in free space you loose speed, and as it took the LEM, command and service module the best part of a week to reach the moon from the 25,000mph departure speed they were slowing down all the time during the trip. -- http://inquisitor.i.am/ | | Ian Stirling. ---------------------------+-------------------------+-------------------- ------ Windows 2000, software for next millenia. latin pun alert - Ian Stirling. |
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The Apollo moon landing missons?
"Greg D. Moore (Strider)" wrote:
Apollos 8, 10,11 and I believe 12 all had a free return trajectory. If the Apollo 12 did not. |
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