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> We know there are bodies in the asteroid belt with more water then all of Earth's oceans. Can you say more about the technology to redirect that much mass to

by schoen 5y ago

> We know there are bodies in the asteroid belt with more water then all of Earth's oceans. Can you say more about the technology to redirect that much mass to make it collide with Mars? (I understand that shifting an orbit is much different from escaping from a gravity well, but I don't have a good intuition for how different, maybe because I haven't played Kerbal Space Program or something.)

XorNot 5y ago
It's all essentially asteroid redirect stuff, so the trick is finding something with what we want, on a close enough orbit, with some reasonable timeframes (i.e. it'd be preferable to do an impact with a 20 year arrival time so the people planning it can live to see it). So either gravity-tug with ion thrusters do a minor correction, or more likely a solar reflector to turn part of the bodies mass into it's own propellant. Or a nuclear charge on the right side of it. I suspect if we were committed to this as a thing we were doing, then once you turned more resources to it the actual calculus would get more complicated: you'd want to map out and characterize everything in orbit, and then start looking for second or even third order redirect candidates - i.e. use a smaller body on a more useful orbit to collide into a larger one for a redirect. The technological criteria are much more reasonable for all of this though: we need to be able to get to what we're going to redirect reasonably quickly, several times so we can characterize and put the gear in place to do the mission. At this point you'd hopefully be using a bunch of Starships running on autopilot. If you take some near-future tech into account, then if end up building the laser array for the Breakthrough Starshot project, a decent use of that most of the time would be lasing the surface of redirect candidates from Earth. EDIT: Just realized I didn't answer your question very well - changing an orbit is much cheaper then escaping a gravity well. To go to the Moon from Low Earth Orbit takes maybe 1000ms-1 of delta-V (weak-boundary transfer and such - I'm probably a little off on that) under the right conditions. To get into Low Earth Orbit through you need to blow through at 8km/s of Delta-V and then a lot more to overcome atmospheric drag. But to return form a Near-Earth Object (say an asteroid) back into the Earth's atmosphere can be done with as little as 60 ms-1 of delta-V in some cases (a little more if you're aiming to hit the ground and not just plough through the atmosphere). Basically with the right timing, orbital adjustments can be incredibly cheap. EDIT 2: Basically it's quite likely there's more then a few comets out there which are going to make close passes to Mars already, where for the cost of an impactor, we could ensure they hit Mars instead if we found them early enough.

by schoen 5y ago

XorNot 5y ago

It's all essentially asteroid redirect stuff, so the trick is finding something with what we want, on a close enough orbit, with some reasonable timeframes (i.e. it'd be preferable to do an impact with a 20 year arrival time so the people planning it can live to see it). So either gravity-tug with ion thrusters do a minor correction, or more likely a solar reflector to turn part of the bodies mass into it's own propellant. Or a nuclear charge on the right side of it. I suspect if we were committed to this as a thing we were doing, then once you turned more resources to it the actual calculus would get more complicated: you'd want to map out and characterize everything in orbit, and then start looking for second or even third order redirect candidates - i.e. use a smaller body on a more useful orbit to collide into a larger one for a redirect. The technological criteria are much more reasonable for all of this though: we need to be able to get to what we're going to redirect reasonably quickly, several times so we can characterize and put the gear in place to do the mission. At this point you'd hopefully be using a bunch of Starships running on autopilot. If you take some near-future tech into account, then if end up building the laser array for the Breakthrough Starshot project, a decent use of that most of the time would be lasing the surface of redirect candidates from Earth. EDIT: Just realized I didn't answer your question very well - changing an orbit is much cheaper then escaping a gravity well. To go to the Moon from Low Earth Orbit takes maybe 1000ms-1 of delta-V (weak-boundary transfer and such - I'm probably a little off on that) under the right conditions. To get into Low Earth Orbit through you need to blow through at 8km/s of Delta-V and then a lot more to overcome atmospheric drag. But to return form a Near-Earth Object (say an asteroid) back into the Earth's atmosphere can be done with as little as 60 ms-1 of delta-V in some cases (a little more if you're aiming to hit the ground and not just plough through the atmosphere). Basically with the right timing, orbital adjustments can be incredibly cheap. EDIT 2: Basically it's quite likely there's more then a few comets out there which are going to make close passes to Mars already, where for the cost of an impactor, we could ensure they hit Mars instead if we found them early enough.