Vessel ElectroDynamic Tether

[MaverickSawyer]

can anyone come up with a way to make an EDT craft? EDT's use a planet's magentic field to generate thrust, so a mission to Jupiter or Saturn should have plenty of available dV.

 

[Spacethingy]

What a beautiful piece of physics! Request seconded!
http://en.wikipedia.org/wiki/Electrodynamic_tether#Tethers_as_generators

 

[Tommy]

can anyone come up with a way to make an EDT craft? EDT's use a planet's magentic field to generate thrust, so a mission to Jupiter or Saturn should have plenty of available dV.

EDTs only work inside the magnetosphere - and don't provide much thrust. They are suitable for maintaining an orbit, even making small adjustments, but they will never get anywhere near to escape velocity. It would take months just to get from LEO to GEO.

 

[MaverickSawyer]

However, they are very efficient. You don't need any propellants, and if designed properly, can provide pseudogravity while in transit a la tumbling pidgeons.

 

[Tommy]

Very efficient, sure - but do you really want to double the trip time to mars to save less about 350 m/s of dV from the engines? It just doesn't make sense - even for an unmanned vessel. In fact, for any vessel large enough to carry humans to another planet it would take about 2 years to gain that 350 m/s using solar power alone to power the tether. The only way to do it faster would be to have a power generator (which would outweigh the fuel you save). Vessel powered by EDT's also need flywheels to maintain the rotation, which adds even more mass. You can use "tumbling pigeons" with a tether without trying to use the tether for propulsion.

EDT's need to be quite long in order to provide any useful amount of thrust - which makes for a vessel which can't change direction quickly if it needs to avoid an obstacle. The increased risk outweighs the increased efficiency in the real world - with all that space junk floating around.

The only time EDT's are truly practical are on a vessel that needs a long tether for some other reason, such as the high altitude rotovator in the HASTOL system.