[X] My Assistant

[algorimancer]

Any showstoppers? I would envision something similar to the upcoming Mars Science Laboratory (RTG's are a given). Lot's colder on Titan... rough on lubricants, and parts would be brittle. Not sure whether the organics would pose a problem in the way of gumming up the works, but it doesn't seem likely at liquid methane temperatures. Smaller world, lower gravity, thick atmosphere... I'm inclined to think that a simple copy of the MSL, perhaps with some added insulation, would work just fine. The only alternative I've been hearing about is a balloon-borne probe, but that doesn't allow the same level of geologic prospecting.

[Guest_BruceMoomaw_*]

A hovercraft, however, has one major problem that a rover doesn't: it's almost impossible for it to climb up or down even midly steep slopes -- and Huygens made it clear that these are a major feature of Titanian terrain.

Ralph Lorenz is an enthusiast for the idea of a Titan helicopter -- which, thanks to that combination of dense air and low gravity, would require fully 37 times less energy to hover than it would on earth -- but the control problems seem alarming to me, and in any case it lacks that really long range that one gets out of a balloon or blimp and which they badly want for Titan. The biggest goal of surface sampling, after all, is a region which has been exposed to liquid water -- or water-ammonia lava -- and it may take quite a lot of flying to find one.

[Bob Shaw]

Bruce:

A Titan helicopter need look very little like one designed for this planet, and could have a really stable flight regime. Look at the toy helicopters and other electric flying machines out there, and you can see a remarkable diversity - like four-engined ones, contra-rotating affairs and even a couple of honest-to-goodness saucers. Add in the experience from some of the smaller military UAVs and you really have the potential for a winner.

One thing that's certainly true about helicopters vs lighter-than-air is that the former would simply flit about, while the latter would be up and about for the longer term. Perhaps helicopters should be seen as an adjunct to a rover, or a lander - small, light and pretty much throwaway.

Bob Shaw

[tty]

Bruce:

A Titan helicopter need look very little like one designed for this planet, and could have a really stable flight regime. Look at the toy helicopters and other electric flying machines out there, and you can see a remarkable diversity - like four-engined ones, contra-rotating affairs and even a couple of honest-to-goodness saucers. Add in the experience from some of the smaller military UAVs and you really have the potential for a winner.

One thing that's certainly true about helicopters vs lighter-than-air is that the former would simply flit about, while the latter would be up and about for the longer term. Perhaps helicopters should be seen as an adjunct to a rover, or a lander - small, light and pretty much throwaway.

Bob Shaw

In my opinion this helicopter idea is utterly impractical. Helicopters are power-hungry, mechanically complex, highly stressed and dynamically unstable.

Yes, I know that a twin-rotor model like the CH-47 is stable, but at the cost of even greater mechanical complexity and the need to either synchronize the rotors, or have them far enough apart not to interfer with each other.

Just constructing a rotor head that will work at cryogenic temperatures would be an engineering nightmare. Metals will be brittle, standard lubricants useless, normal elastomers rock-hard etc. Building a rotor blade (which is highly stressed and has to move in a complicated way around all three axes during each rotation) wouldn't be easy either.

It is true that a helicopter for Titan would be very unlike an earth helicopter. It would also be impossible to test-fly on Earth. Temperatures and atmosphere composition it might just be possible (but very expensive) to simulate in a large refrigerated chamber, but never the gravity.

This also applies to the software. You could never test the flight control software (which must of course be completely autonomous) in a realistic way either. And remember, it must never re-boot and never safe itself. Also it had better be pretty good, so it doesn't get itself into a vortex ring situation, turns downwind at low altitude, overtorques or any other of the no-nos of helicopter flying.

Power: a RTG seems to be the only practical alternative. Unfortunately they're heavy and doesn't produce that much power. This is the best part of the balloon/blimp concept: the lift is produced by the waste heat, leaving all the electric power for propulsion and control/science/communications.

tty

[yaohua2000]

Power: a RTG seems to be the only practical alternative. Unfortunately they're heavy and doesn't produce that much power. This is the best part of the balloon/blimp concept: the lift is produced by the waste heat, leaving all the electric power for propulsion and control/science/communications.

Titan is full of methane, so why not bring some oxygen there as "oil" to make a normal chemistry engine?

[tty]

Titan is full of methane, so why not bring some oxygen there as "oil" to make a normal chemistry engine?

CH4 + 2O2 => CO2 + 2H2O, so you need four pounds of oxygen to each pound of methane. Methinks a RTG would give better value for money.

tty