Advanced Question Moon curvature vs. Landing Pads elev and T/D points

Michael_Chr

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This applies to Orbiter 2010 (most likely different i 2016)
Trying to create a lunar base with realistic dispersal of Landing pads (i.e. situated around 1000 mtrs away with the delicate infrastructure protected by large blast barriers etc. for the dreaded lunar dust) I realised that Pads placed that far away are not aligned with the actual touch down (T/D) point. They tend to float above the T/D point giving the impression that the vessel "sinks through" the Lpad.
A little experimentation lended the conlusion that Lpads with a 1000 mtr displacement from base origo need to be "lowered" by 30 cmtr.

Having set "MAPOBJECTSTOSPHERE" to True for the base in question I can deduce that this function is not implemented for Lpads.

So I guess bases assume a flat body and since the moon in a spherical one and not that large at that so at greater distances this becomes an issue.

Does anyone know of any (online) tool to calculate how much to lower the local elevation for an object based on distance ?

P.s. Seem that Surftilelist statement works "spherically"

pps. tried to create a surface enviroment in GMAX but with objects at larger distances from the centre this issue got the better of me.

Best regards

Michael
 

BrianJ

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Hi,
a little geometry to think about :)

I think this should work....

If:
r = radius of Moon = 1737100m
d = distance of "object" from base centre
h = height of base plane above Moon surface at object position(we want to find this) measured perpendicular to base plane.

Then we can find the angle "theta" subtended by the lines from Moon-centre to Base and Moon-centre to object.

theta = atan(d/r)

Then for the height h:
h = r*(1 - cos(theta))

For an object 1000m from base centre this equals ~0.288m

I guess you could make a spread sheet to do it for you if you have many objects to do.

Cheers,
Brian
 

Michael_Chr

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Hi Brian.
Thanks for your help. Has everything set up in a nice spreadsheet where I can use the ordinated values (X,Z) as input.
However it is mindblowing to think that a local horizon only 1000 mtrs away on the moon dips by 30 cm. The moon is not that big after all.
Cheers...Michael
 
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