Lithobraking for lunar soft landing or habitat formation

[Frank]

It sounds really stupid at first - a survivable crash landing...

The idea is similar to aerobraking where regolith is used to decelerate a space ship.  Not one with humans aboard of course, it's a crash landing and bad things can happen.  So bring the elliptic orbit of a ship to a grazing height and touch down, then skid along the lunar surface.  But what can this get us?  A bunch of otherwise useless upper stages of rockets could have their material recycled once dropped onto the lunar surface.  If we do this enough times, we might become able to clear out a runway or learn how to do it without much damage, then more sensitive stuff could be "landed" this way.

But what if we send a rocket into a mountain or crater wall?  Maybe it creates an automatic habitat - a space covered by the 1 to 10 m of regolith needed to protect humans from cosmic rays and solar proton events.  So forget trying to build lunar excavators and complex 3D printing for habitats, just(tm) drop a rocket into the regolith, cut out the unneeded parts and replace that space with some sort of inflatable Hab.  Done.

A less random/gross way might be to use a spent rocket as a form and drop the edge of a mountain or crater down on it instead of lifting and gathering regolith from all around.  Use the potential energy already in the mountain to quickly bury a habitat.

Maybe use the buried rocket tanks as storage and the regolith would help regulate the temperature, acting as insulation.  If the rocket goes in engine first, access to the tanks or even tank fittings might be available.

 

[Enthalpy]

The Moon's escape speed in 2380m/s, so the smallest velocity, dropping from low orbit, is 1680m/s. Nothing keeps its shape at this speed, and I don't imagine how a "grazing" impact is achieved nor what it brings concretely.

Effect on the Moon: the same as any impact, it makes a crater, wide but not very deep, open to the sky, the radiations and the meteorites. Long effort before it's something usefu, and I don't see why we should add craters on the Moon since there are already enough ones.

[Frank]

1 hour ago, Enthalpy said:

The Moon's escape speed in 2380m/s, so the smallest velocity, dropping from low orbit, is 1680m/s. Nothing keeps its shape at this speed, and I don't imagine how a "grazing" impact is achieved nor what it brings concretely.

Effect on the Moon: the same as any impact, it makes a crater, wide but not very deep, open to the sky, the radiations and the meteorites. Long effort before it's something usefu, and I don't see why we should add craters on the Moon since there are already enough ones.

I agree that the tank would likely be deformed now that I've read how thin the material is: 2.5 to 5 mm of aluminium alloy.  I've thought of a better way to build a habitat anyway.

 

Assuming constant deceleration, ((2380 (m / s))^2) / (2 * 45 000 (m / (s^2))) = 62.9377778 meters, we need a crater less than 100 m long for hardened payload (4500g) to survive.

 

Krafft Arnold Ehricke (March 24, 1917 – December 11, 1984) was a German rocket-propulsion engineer and advocate for space colonization.

https://en.wikipedia.org/wiki/Krafft_Arnold_Ehricke

Krafft Ehricke invented the Lunar Slide Lander as an alternative to powered descent to the lunar surface, which would use 90% less propellant by taking advantage of the Moon’s sandy and glassy soil to slow the vehicle.  http://schillerinstitute.org/educ/sci_space/2017/0324-lifting_mankind/lmo.html

 

I wasn't proposing we land humans, just hardened payloads.