Comment Re:Yeay! (Score 2) 39
Indeed, I prefer a relay too; I was just pointing out that it's not a fundamental requirement and there are mission proposals that don't use one.
Actually my "ideal" mission (a Titan sample return mission) has the relay probe be the propulsion stage (ion powered), and operating in a low orbit. While a tilt-rotor explorer would be exploring, the orbiter would be pumping its propellant tanks full of Titan's outer atmosphere (most ion engines are very propellant flexible, and the 1500m/s Titan atmosphere drag velocity is way less than the ion output velocity) and thus refilling its tanks for a return mission. So once the explorer returns on its ascent stage and re-docks, the propulsion stage now has full power and has full tanks for the return mission with the surface samples. Then back at Earth, not only are the surface samples returned, but also the residual Titan atmosphere in the propellant tanks. And both the propellant stage and explorer's (expensive) RTGs are recovered at the same time .
My ideal explorer is not a lander, but a tilt-rotor pontoon aircraft (I really don't see the point of fixed wing... tilt rotor adds in another driven component and joint, but it removes a corresponding required control surface, so it's a wash in terms of complexity, and it lets you land VTOL, then rest on the surface and recharge your flight batteries while doing surface science - aka, you can use a much smaller, cheaper RTG. Win-win-win. And while most propelled designs I've seen use ridiculously tiny quadcopter-ish motors to barely hold a heavy probe aloft (say a 0,5kg motor for a 120kg probe), my mission would have a several kilogram motor so that it'd have enough power to haul its ascent stage up to max flight altitude and velocity and reduce its delta-V reqs down to about 2k m/s. If the ascent stage has the same payload fraction as a Pegasus solid stage then that means that it'd only need to be about 150% the weight of whatever portion of the explorer you wish to return to orbit - totally doable. And the explorer doesn't need orbital maneuvering capability because you've got an ion-propelled propulsion stage out there that can come to you.
As an added bonus? You can do a stardust-style flyby of Enceladus for the added weight of a little aerogel, same with various rings, and a dip through the most extreme outer layers of Saturn with the scoop / pump feeding into a small sampling tank. Then it's not just a Titan sample return, but a Titan / Enceladus / Saturn sample return. And you save weight and cost on science experiments. You don't need to bring the science experiments to the Saturnian system, you just bring the Saturnian system back to Earth
Yeah, that'd probably be a Flagship mission. But my god, can you imagine how much data we'd get out of that?
(Concerning robotic arms... I was surprised how light they are when researching. MERs's very capable arms were barely over 4kg. Totally doable for even a mission where weight constraints are significant)