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Mistake #1, the idea of a "risk corridor" applies to an object in a decaying orbit. It will hit somewhere along the line of orbit. But for an object coming fr
by btilly 7y ago
Mistake #1, the idea of a "risk corridor" applies to an object in a decaying orbit. It will hit somewhere along the line of orbit. But for an object coming from out of orbit, there is a center of where it is likely to hit, and then a bell-shaped curve across the cross-section of the Earth for where it might. Basically half the world is at risk, with some areas at higher risk than others.
Mistake #2, objects that we find which could hit us get within range of our rockets only a finite number of times. For a previously unknown large object with a several year returning orbit, that finite number is likely to be 2 - once when we found it and once when it comes back (at which point it is too late). A more realistic version would be that it is on a long trajectory that will hit Earth after 3-4 times. Which gives us a lot longer to prepare, and a clear timing on when we want to try to hit it.
I won't comment on the cultural mistakes. Except to note that "We're going to get hit but odds are good that it is over water and nobody gets hurt" might be less panic inducing than the story claims.
- T-A 7y ago> the idea of a "risk corridor" applies to an object in a decaying orbit. It will hit somewhere along the line of orbit It also applies to asteroids, and is a standard concept used in these scenarios. See e.g. the materials from the exercise at this year's Planetary Defense Conference [1] (the story on LitHub is basically a variation on that scenario, which also features an asteroid splitting in two during the deflection attempt, a failure to use nukes, and a city destroyed by the impact: New York). > objects that we find which could hit us get within range of our rockets only a finite number of times There are more and less viable launch dates, clustered in launch windows, but the details vary depending on your vehicle and the orbit. JPL's NEO Deflection App [2] has several illustrative examples which you can play with, and which work pretty much as in the story. [1] https://cneos.jpl.nasa.gov/pd/cs/pdc19/ https://cneos.jpl.nasa.gov/pd/cs/pdc19/ [2] https://cneos.jpl.nasa.gov/nda/ https://cneos.jpl.nasa.gov/nda/
- btilly 7y agoHuh, that is bizarre. How does this square with my understanding that the path is off by something close to a normal distribution? I guess that the big question mark is time. If we know the path of the asteroid very precisely, and the path of the Earth very precisely, but we don't know exactly when the asteroid goes down that path, it would result in something like a risk corridor depending on where the asteroir was between leading and trailing the Earth at the point of impact. I wouldn't (in fact didn't) guess that. Thank you for the references!