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Iain Lambert
2002-Sep-26, 10:06 AM
Hi everyone, long time no posting from me...

Anyway, I've popped back to ask a small question. As far as a quick search of the web shows, it seems there is little or no ionosphere on the Moon. Since I remember that being how radio waves get beyond the horizon here on Earth, am I right in thinking that this means that any radio communications on the Moon would have to be line-of-sight to work properly?

Only I've got a friend who is knocking around game ideas set on our Moon, and I'd like to get the physics as right as possible; this could actually be a really cool gameplay element between team members.

kucharek
2002-Sep-26, 10:33 AM
Thumbs up!

Harald

GrapesOfWrath
2002-Sep-26, 10:36 AM
Use lunasynch satellites? O wait, that'd be Earth, right?

Maybe just close orbiters--you wouldn't have to worry about atmospheric friction.

Iain Lambert
2002-Sep-26, 10:49 AM
Thanks muchly for the confirmation.

Actually, while this would be possible with satellites I think it'll be more interesting to either go with making the player build radio masts (which they would then have to defend) or even getting down 'n' dirty with a need to stay that close. Imagine holding a line in multiplayer, knowing that if you fall back you not only surrender your ground to the other team, but leave your team-mates cut off from the command centre. This has definite coolness factor, thanks!

kucharek
2002-Sep-26, 11:53 AM
For some time Jack Schmitt and a gang of flight controllers drafted a lunar landing mission on the not-earth-facing(*) side of the Moon, e.g. in Tsiolkovsky. They even tracked down some unused communication satellites somewhere they would have put in lunar orbit.
There is a story by Stanislaw Lem which deals with communication problems on the Moon. In the story, the use radio relays and cable.

Harald

(*) Avoiding "backside", "farside" or "DARK SIDE" /phpBB/images/smiles/icon_biggrin.gif

kucharek
2002-Sep-26, 12:03 PM
On 2002-09-26 06:36, GrapesOfWrath wrote:
Use lunasynch satellites? O wait, that'd be Earth, right?

Good question.
I guess, Earth is not in a lunasync orbit around the Moon, it's "mostly" the Moon that orbits around Earth. So, if Earth would be much smaller, it surely would need much longer to circle the Moon than the current 29 days.
But I guess a lunarsync orbit would be pretty much perturbed by Earth, so maybe we better put those satellites into the Lagrange points.

Harald

PS: I just recently visited Lagrange's tomb in the Pantheon in Paris. It's nice that nations not only honour people who achieved a sufficient kill rate...

[Spelling corrected]

<font size=-1>[ This Message was edited by: kucharek on 2002-09-26 08:05 ]</font>

GrapesOfWrath
2002-Sep-26, 12:52 PM
On 2002-09-26 08:03, kucharek wrote:
Earth is not in a lunasync orbit around the Moon, it's "mostly" the Moon that orbits around Earth.
Well, Earth is synchronous with the moon, but you're right that a satellite wouldn't have to be at Earth distance to be lunasynch. But they would be twice as far from the moon as geosynchs are from Earth--and the Earth would be a big perturbation, as you say.

But I guess a lunarsync orbit would be pretty much perturbed by Earth, so maybe we better put those satellites into the Lagrange points.
The Earth/moon Lagrange points (http://map.gsfc.nasa.gov/m_mm/ob_techorbit1.html)? L1 and L2 don't help much with communication from lunar farside to lunar nearside, and L4 and L5 are as far from the moon as Earth is. Which one am I forgetting? O yeah, L3 would be on the other side of the Earth from the moon.

Hey, since there is no atmospheric friction, what about satellites that zip just a couple feet off the ground--at the terrain high points anyway. The mascons would play hob, but it'd be kinda fun to watch 'em whirl by.

I envision huge observation decks, where spectators can watch it approach, and...help me out here, guys.

AgoraBasta
2002-Sep-26, 01:13 PM
It would be much more practical to communicate by acoustic signalling through the moon body. Then relay to local radio carrier.

kucharek
2002-Sep-26, 01:43 PM
On 2002-09-26 09:13, AgoraBasta wrote:
It would be much more practical to communicate by acoustic signalling through the moon body. Then relay to local radio carrier.

That's also in the Lem story I mentioned above.

kucharek
2002-Sep-26, 01:45 PM
On 2002-09-26 08:52, GrapesOfWrath wrote:

Hey, since there is no atmospheric friction, what about satellites that zip just a couple feet off the ground--at the terrain high points anyway. The mascons would play hob, but it'd be kinda fun to watch 'em whirl by.

I envision huge observation decks, where spectators can watch it approach, and...help me out here, guys.


You mean like this (http://www.hq.nasa.gov/alsj/gibbons_rapids.jpg) rare shot, showing Endeavour zipping along Hadley rille...?

GrapesOfWrath
2002-Sep-26, 02:41 PM
Have the HBers seen those (http://www.hq.nasa.gov/office/pao/History/alsj/alsj.funpix.html), especially this one (http://www.hq.nasa.gov/office/pao/History/alsj/moonwalkers.jpg). I liked the cat box one (http://www.hq.nasa.gov/office/pao/History/alsj/toonseman.jpg) too.

kucharek
2002-Sep-26, 03:02 PM
The most funny thing is, that this (http://www.hq.nasa.gov/alsj/alsj.trio.jpg) one already appeared on a few HB's pages as a hoax proof... /phpBB/images/smiles/icon_smile.gif

[Link corrected]


<font size=-1>[ This Message was edited by: kucharek on 2002-09-26 11:03 ]</font>

Karl
2002-Sep-26, 03:10 PM
On 2002-09-26 06:06, Iain Lambert wrote:
Since I remember that being how radio waves get beyond the horizon here on Earth, am I right in thinking that this means that any radio communications on the Moon would have to be line-of-sight to work properly?


VHF/UHF will exhibit knife edge diffraction over the top of mountain ranges, allowing some degree of non-line-of-sight communications, but the geography has to be right.