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Re: Info about OSCAR on Moon surface



> 1 - What kind of temperatures an Moon station have to survive ?

IIRC, +200 to -200 F or more, sometimes across the device itself.  I.e., 
anything the sun is shining on will equilibrate to about +200 F, and 
anything the sun isn't shining on will cool off to -200 F.  If you have 
an antenna that is made of a material that has a large coefficient of 
thermal expansion and low thermal conductivity, it will bend away from 
the sun ..

> 2 - Is it difficult to get an station (10..50kg payload) on the Moon 
> surface ?

Grumman paid the LM development team engineers $10,000 for every pound 
they could eliminate from the LM design.  (This was in 1969 dollars -- 
it would be many times that now.)  The guy who won the jackpot was the 
one that figured out they didn't need seats, and without seats, they 
didn't need large windows.  In short, oh yeah.  It took a Saturn V to 
get an 80,000 pound LM+CSM combo into lunar orbit with enough fuel to 
put a 20,000 pound LM on the lunar surface.  I don't remember what sort 
of booster it took to get the Surveyor series landers on the surface, 
but I think it was at least a Titan and a large upper stage.

Putting an Oscar on the lunar surface would take a substantially bigger 
kick than a GTO boost.  You might not need to do the Apollo thing and do 
a TLI from LEO, but no matter how you slice it it's going to be a huge 
and expensive delta-V.  Bear in mind, too, that unless W5UN (sorry, 
Dave ;-) is the only one you want on the bird, it's going to need some 
serious transponder power and a very narrow beam -- Earth is only 3-4 
degrees wide at that distance.  I'd say 100-200W minimum for SSB, 
possibly less for CW, depending on how sharp your filters are.  Maybe 
more, depending on what band you're on and what sort of noise figures 
you can count on for the downconverters Earthside, etc.  Bear in mind, 
too, that you're not looking at a cold sky -- moon noise isn't that 
much, but it's above cold sky background, so you lose some performance 
there.  It might take as much as a 500W transponder to get a clean SSB 
signal on an average sat rig.

> 3 - I heared the moon changes in elevation/azimuth to the earth. How 
> many degrees ?

Well, the moon is in an elliptical orbit.  I don't remember exactly how 
much it librates in latitude, but it's at least a few degrees. This is 
how photography of more than 50% of the moon's surface is possible from 
terrestrial telescopes.  If you have a tight enough beam to keep 80-90% 
of the beam energy directed at Earth, you may need tracking equipment on 
the antenna, which means you have moving parts to break down.  Or you 
have a solid signal to the bird only part of the time, sort of like the 
current squint situation with AO-40.  Take your pick.

> 4 - How long takes an light/dark period on the moon ?

Approximately two weeks on, two weeks off, which is going to be pure 
hell on your batteries.  Apollo ALSEP's that needed power typically 
carried RTG's, and most of the powered experiments died after a month or 
so, if they even lasted through a lunar night.  I think the only 
experiment that is still in service is the laser ranging target, which 
is basically a pack of passive retroreflectors.  You *might* be able to 
get by with an RTG or two for keep alive/standby charge during dark 
periods, but the electronics may not survive more than a few hot/cold 
cycles before they crap out.

My thought is that a lunar Oscar would be a nice trick, but not reliable 
enough to be worth the enormous expense of putting it up there.  If we 
could get one that we could count on working for a year or two, it might 
be worth it, but for a month or two it's just not worth it.   Any 
engineers that know otherwise are welcome to prove me wrong .. ;-)

Heard from a flight instructor:
"The only dumb question is the one you DID NOT ask, resulting in my 
going out and having to identify your bits and pieces in the midst of 
torn and twisted metal."

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