What Shape Should a Lunar Shuttle Have?

[sanman]

If you had to design a vehicle that would travel from the Moon's surface to lunar orbit and back down again, then what would it look like? What kind of geometry or shape would it have? I'm thinking of a heavy-lift vehicle, which would be able to bring down mining equipment, and lift up ore.

Would geometry really matter, since there would be no atmosphere to get in the way?

Would a wide and flat pancake-shaped saucer be just as practical as a tall thin pencil-shaped rocket?
Would a spherical shape be better, or perhaps an egg-shape?

Or could it simply be an assembly of scaffolding without a single all-encompassing hull?

 

[Astronuc]

The objective in the design of a lunar surface-to-orbit transfer vehicle would be to minimize tare mass, and maximize specific impulse or thrust/weight.

As one indicated the geometry is not so important since there is no atmosphere. There is no need for wings, since there is no atmosphere to provide lift. However, one would need a geometry that is stable and provides for maneuvering rockets.

From surface to orbit, the use of mag-lev or linear induction systems has been considered. Much of the propulsive force is derived from a surface structure and that minimizes on board propulsion and propellant mass.

From orbit to surface would seem to require an onboard propulsive system and use of propellant. For that reason, space elevators would be desirable.

A cylindrical craft with tapered ends might be optimal, but the packing (lading) efficiency is not as good as a parallepiped (rectangular) geometry.

 

[Danger]

The packing efficiency will depend upon what the payload is.
A sphere gives the maximum amount of internal volume vs. surface area, so is therefore most efficient for any flexible or fluid cargo. I agree that a rectangular structure would be better for things that are packaged. Other than aesthetically, I don't see what the purpose of a 'rounded cylinder' would be.

 

[sanman]

From surface to orbit, the use of mag-lev or linear induction systems has been considered. Much of the propulsive force is derived from a surface structure and that minimizes on board propulsion and propellant mass.

From orbit to surface would seem to require an onboard propulsive system and use of propellant. For that reason, space elevators would be desirable.

Hmm, I was thinking that a space elevator would be too confining on where you could land or take off from. A maneuvering vehicle however would be able to select any number of locations at which to land or take off.

So if we confine ourselves to a propellant-using vehicle, I was presuming an approximately cylindrical shape propelled by chemical rockets.

But if the vehicle had a larger horizontal radius -- perhaps a lenticular, flattened spherical shape -- couldn't that perhaps facilitate the idea of plasma propulsion?
Plasma doesn't like to be at high density, due to internal charge repulsion effects, and so a more pancaked shape with a larger cross-sectional area would allow for a very wide plasma thruster to lift the craft.

Comments?

 

[Danger]

I don't really see that the shape or size of the craft would matter as far as plasma propulsion is concerned. You could always just spread your engines across a wider area while maintaining whatever shape you want. I've never heard, however, of plasma thrusters being considered for lifting from a planetary body. The thrust is pretty low.