[amsat-bb] Re: Soft,,, Well Kind Of,,

[Nate Duehr]

What would cause it to "decay" with no atmosphere?

--
Nate Duehr
Sent from my iPhone

On Feb 15, 2009, at 7:51, Joe <nss at mwt.net> wrote:

> That's exactly as I was thinking.
>
> With no atmosphere, the moon,  you could in theory orbit with a  
> decaying
> orbit until it was only as high as the surface,  (But of course the
> mountains are a problem.)
>
> But Some numbers were crunched,,  and say a lander was orbiting, and
> slowed down just the right amount that it began to decay.  ever soo
> slowly,  in theory of it was a perfect sphere and smooth as glass  the
> thing could orbit inches above the surface true?
>
> But  the moons gravity is very un even as well as the surface..  But
> give the sphere and smooth thought,
>
> It could orbit and eventually land at a speed of,  1.68 km per  
> second or
> slightly over 6000 MPh!  don't think it could survive.
>
> Oh well..
>
> Bob Christy wrote:
>
>> In 1966, the Soviet Luna 9 survived a near-vertical landing on the  
>> Moon
>> with a speed of about 50km/h (approx 30mph). It used an inflated  
>> bag to
>> cushion the impact.
>>
>> In 1997, America's Pathfinder rover used a similar technique and  
>> touched
>> down on Mars with a similar vertical speed. It was designed to take  
>> an
>> impact about fifty percent greater than it actually experienced.
>>
>> It would be possible to land something at a high velocity,  
>> providing the
>> vertical component is not much more than that of Luna 9 or  
>> Pathfinder.
>> Horizontal speed can be killed by rolling and bouncing, as happened  
>> with
>> Pathfinder when it struck the surface at an angle of about 50  
>> degrees.
>>
>> The downside of this approach comes in the form of any significant
>> vertical obstruction such as a large boulder or a cliff face.
>>
>> Bob Christy
>>
>>
>> ==============================================================
>> What speed do you think would be max survivable speed for a landing  
>> on
>> the moon for a robot, or comm system?
>>
>> How fast could something hit and survive?
>>
>> Joe
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