Lunar Lander Contest

[RogerInHawaii]

There's a contest that's sponsored by NASA and others (http://space.xprize.org/lunar-lander-challenge)
which challenges participants to build and fly a "Lunar Lander". The mission is to take off from some position, fly a specified distance, and then land again at another position. All of the entries, thus far, have a similar structure (see http://www.armadilloaerospace.com/n.x/Armadillo/Home/News?news_id=368) in that they look much like the Apollo lunar lander, with an engine beneath it.

It got me to thinking about alternatives. The very first liquid fueled rocket built by Robert Goddard (see http://en.wikipedia.org/wiki/Robert_Goddard_(scientist)) was a basically (tall) triangular shape with the rocket nozzle at the top, its exhaust plume directed down through the center of the structure.

The difference between Robert Goddard's design and the usual lunar lander designs is like the difference between lifting something by a string tied to its top and lifting something by pushing up on its bottom with your finger. Unless you're very adept at keeping the object from falling over, the push-from-the-bottom approach is much more difficult than the lift-with-a-string approach.

So, I'm wondering, might Robert Goddard's approach of having the combustion chamber and nozzle at the top of the craft be inherently more stable (relying primarily on gravity to provide its stability) and more easily controlled than having it at the bottom?

 

[origin]

The nozzel at the top seems like it would be more stable, but it would tend to toast the astronauts below the nozzel. With current computer capabilities I think the designs that have the rocket nozzel below the ship work just fine, and no toasted astronauts.

 

[RogerInHawaii]

The nozzel at the top seems like it would be more stable, but it would tend to toast the astronauts below the nozzel. With current computer capabilities I think the designs that have the rocket nozzel below the ship work just fine, and no toasted astronauts.

Mmmmm, toasty.

Two thoughts on this: 1) the structure of the craft itself could be donut shaped so that the thrust plume travels down the empty center, with appropriate heat shielding to protect the contents. 2) The Lunar Lander contest makes no requirements that the craft actually be astronaut-rated, only that it be able to take off and land accurately within a given time frame. So I'd think that having gravity give an assist on keeping the craft stable might just make control of the craft that much easier, and make the contest open to more people who may not have the computer-control expertise that's necessary with a bottom-thrust craft.