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Saturn Ring Sample Return Mission?
Craig Fink wrote:
In article , Craig Fink wrote: A planetary probe should be able to fly in and sample Saturn's ring material and analysis it and/or return a sample to Earth. The relative velocity between the probe and ring material would be almost zero if the probe is in-plane near circular. Has anyone proposed or is working on a Saturn Ring Sample mission? Herman Rubin wrote: Assuming you had a big enough and complex enough vehicle you could get to the neighborhood of Saturn and get the vehicle into the same orbit as ring particles, getting the piece of the ring particle might not be too difficult. But it would have to be analyzed there. Returning it to Earth in usable shape might be difficult for many reasons, one of them being that the current estimate of what the ring particles are come up with some sort of water-ammonia ice, and even returning an empty probe requires more energy than will be available. An Aerobrake using Saturn's atmosphere to start the journey at the bottom ring, a reasonable L/D could supply the plane change. And it could be used at Earth with the returning samples... Aerobraking at Saturn is a challenge. We are talking speeds greater than 35 km/s here. If you want to complicate this with a plane change using aerodynamic lift then I think your heat shield is in sci-fi territory. You might be able to do it with multiple passes where each orbital dip in the atmosphere only takes away a little velocity and only changes the plane a little. But that would take a lot of time (years) and would still be technically challenging. Alain Fournier |
#22
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Saturn Ring Sample Return Mission?
Alain Fournier wrote:
Craig Fink wrote: In article , Craig Fink wrote: A planetary probe should be able to fly in and sample Saturn's ring material and analysis it and/or return a sample to Earth. The relative velocity between the probe and ring material would be almost zero if the probe is in-plane near circular. Has anyone proposed or is working on a Saturn Ring Sample mission? Herman Rubin wrote: Assuming you had a big enough and complex enough vehicle you could get to the neighborhood of Saturn and get the vehicle into the same orbit as ring particles, getting the piece of the ring particle might not be too difficult. But it would have to be analyzed there. Returning it to Earth in usable shape might be difficult for many reasons, one of them being that the current estimate of what the ring particles are come up with some sort of water-ammonia ice, and even returning an empty probe requires more energy than will be available. An Aerobrake using Saturn's atmosphere to start the journey at the bottom ring, a reasonable L/D could supply the plane change. And it could be used at Earth with the returning samples... Aerobraking at Saturn is a challenge. We are talking speeds greater than 35 km/s here. If you want to complicate this with a plane change using aerodynamic lift then I think your heat shield is in sci-fi territory. You might be able to do it with multiple passes where each orbital dip in the atmosphere only takes away a little velocity and only changes the plane a little. But that would take a lot of time (years) and would still be technically challenging. I agree, Multiple Passes are reasonable to reduce heat loads to within the physical limits of the heatshield. Or, may not be required. The two largest passes, Injection into a highly elliptical orbit around Saturn and Apogee Reduction from the top to the bottom of the rings, are much smaller than 35km/s. The others can be of the same magnitude. A few months, really dependant on the first aerobrake and the period of the injection orbit. Although, taking a few years would be ok. Maybe drop off some monitor probes in a bunch of different orbits. Lifting surfaces are much cooler than the stagnation point surface. The more lift, the more the orbital elements can be adjusted. More than just inclination. The more lift, the lower peak heating loads. All can be adjusted during Multiple Passes, which really makes it much easier to target the final orbit. Flying through the rings may also be possible...just don't run in to anything solid... -- Craig Fink Courtesy E-Mail Welcome @ |
#23
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Saturn Ring Sample Return Mission?
Craig Fink wrote:
Alain Fournier wrote: Aerobraking at Saturn is a challenge. We are talking speeds greater than 35 km/s here. If you want to complicate this with a plane change using aerodynamic lift then I think your heat shield is in sci-fi territory. You might be able to do it with multiple passes where each orbital dip in the atmosphere only takes away a little velocity and only changes the plane a little. But that would take a lot of time (years) and would still be technically challenging. I agree, Multiple Passes are reasonable to reduce heat loads to within the physical limits of the heatshield. Or, may not be required. The two largest passes, Injection into a highly elliptical orbit around Saturn and Apogee Reduction from the top to the bottom of the rings, are much smaller than 35km/s. The others can be of the same magnitude. A few months, really dependant on the first aerobrake and the period of the injection orbit. The 35 km/s I mentioned wasn't a delta-V. It is the speed of the probe relative to Saturn's atmosphere at first encounter. Hitting an atmosphere at 35 km/s is painful even if you just skim the atmosphere a little and you only want to have an aero-braking delta-V of a few hundred m/s. Even if you are hitting a very thin atmosphere, it will be heated to a plasma, the ions hitting your heat shield at such high speeds will damage your heat shield no matter what material you use. I don't think it is impossible to do, but it is very challenging. Alain Fournier |
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