Portal:Concept Studies/Momentum Exchange Tether

From TeamFrednetWiki

This page is for pro and contra voices for Momentum Exchange option for landing Lunar Rover.

Background

Those who are not familiar with the issue, read first the TUI page.

Proposal

The basic idea was to hire a lift to Low Earth Orbit and accelerate from there by Ion Thrusters to Lunar Orbit. On the way a tether is released with the Lunar Rover and rotated by the climbing time to Luna. Rotation energy is generated by same motor as the acceleration, by oscillating main engine thrust/direction in resonance with tether system. At the lunar proximity the tether length is adjusted so that rover ground speed equals zero and tether is let go on touch down.
This scheme provides lowest total mass of the system and therefore lowest lift-up price to orbit, making it possible for us to reach Moon at all.

Conclusion

This option is closed by expert statement:

Robert Hoyt, TUI wrote:

What you are describing is basically a variant of a "Lunavator". I think the concept was first proposed by Hans Moravec around 1976. Here is a link to a paper where I did some 
analysis and design of a   Lunavator, using material strengths of currently available materials:
CislunarAIAA
I believe that a Lunavator could someday be part of a lunar transport system that would reduce costs for transporting many payloads to and from the Moon. Unfortunately, however, 
for a one-shot system it  doesn't make sense - the mass required for the tether will be larger than the mass of propellant to do the same job. You'd need to use the tether for 
many payloads (dozens, at least), before you'd see a net mass savings.