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.

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 )

(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.

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.


They had to do a trans lunar injection from earth orbit followed by a
mid course correction which put them on a free return trajectory. This
was followed by a lunar orbit insertion, which was done behind the
moon when they were out of contact.

Zoltan

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.

"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.

Right, thanks for all the replys.


Christopher
+++++++++++++++++++++++++
"Kites rise highest against
the wind - not with it."
Winston Churchill

"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.

"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.