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Scientists Map Out How to Nudge Small Asteroids into Earth?sOrbit
On Sep/5/2018 at 21:13, Sylvia Else wrote :
On 6/09/2018 6:18 AM, Alain Fournier wrote: On Sept./4/2018 at 06:44, Jeff Findley wrote : In article , ess says... On 4/09/2018 9:29 AM, wrote: "The notion of an asteroid headed for Earth is typically seen as a bad omen. On the flip side, some scientists and entrepreneurs increasingly see this scenario as a potential opportunity. Deliberately redirecting asteroids to our planet?s vicinity could enable us to study them up close, or even mine them. Given that these objects are packed with valuable resources, building a collection of them nearby could spark major advances in spaceflight, to say nothing of the scientific research that might result from easy access to these extraterrestrial bodies. A recent paper published in Acta Astronautica suggests that asteroids could be captured in Earth?s orbit with aerobraking, a maneuver that uses atmospheric drag to decelerate and position objects in stable trajectories around a planet. Aerobraking has helped place interplanetary spacecraft in orbit around Mars and Venus, and to slow down spacecraft returning to Earth. Led by Minghu Tan, a PhD student at the University of Glasgow, the paper immediately addresses the most obvious concern with this scenario: What if there?s some mistake in the redirect process and an asteroid accidentally impacts Earth? It?s bad enough that the dinosaurs were oblivious to their doomsday space rock, but it would be especially embarrassing if we humans smack ourselves in the face with one." See: https://motherboard.vice.com/en_us/a...o-earths-orbit After the aerobraking pass, you need to raise its perigee quite a lot, or it's just going to come back and burn up, either on the next pass, or some subsequent pass. The article doesn't say how the perigee would be raised.* Unless they're planning on using a lunar flyby, I don't see how you can do this without a sufficiently large rocket engine. If you can nudge it enough to get it to do aero-braking, it shouldn't be a problem to raise the perigee. One can imagine an extreme case where the asteroid was going to pass 200 km above Earth's surface and you can just barely nudge a little lower for aero-braking and then aren't able to raise the perigee fast enough. But a big asteroid being on such a trajectory isn't very likely. And those deciding to capture it being smart enough to be able to nudge into the atmosphere, yet too stupid to notice the danger isn't likely either. (People too stupid to see the danger aren't hard to find, it's the combination with smart enough to be able to nudge it that isn't likely.) A small nudge a long way out can be enough to direct it towards the Earth. But after the aerobraking, you don't have that option. You need to raise its perigee quite a lot. But you would probably want to nudge it millions of kilometres for it to go towards Earth. You only need to raise perigee a few kilometres per orbit. Yes, you do have to know what you are doing. And make sure that you can raise the perigee. But in most cases, raising the perigee should be easier than sending it to Earth's atmosphere, maybe not all cases, but most cases. And those who would do this are most likely people who understand the difficulty of the task and the risks. You don't send an asteroid towards Earth without understanding orbital mechanics and rocketry. Alain Fournier |
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