Dinosaur Killers 2

In a NYT article, by way of Boing Boing, columnist Errol Morris, asks for your opinion on a statement by David Deutsch about the asteroid threat to Earth:

…we live in an era of unprecedented safety: the twenty-first century is the first ever moment when we have known how to defend ourselves from such impacts.

The survey asked not only for your opinion, but your level of confidence in that opinion.

The problem with this survey is that it asks for a single answer to two questions: “Do you think Deutsch’s claim is true? Is it true that ‘we live in an era of unprecedented safety’?” Of course, that’s because Deutsch makes two claims (1) we live in an era of unprecedented safety and (2) the twenty-first century is the first ever moment when we have known how to defend ourselves, and both of these miss the point.

My answer to claim (1) was that his claim was false, and there wasn’t any place I could answer claim (2), which is true. Claim (1) is false because of the third claim that no-one mentioned — that we not only know what to do, but we have the technical capability to do it on an appropriate timescale.

We have, in the last decade, obtained an unprecedented inventory of earth-orbit-crossing, and near-earth-orbit asteroids. There is, among the rocks in that inventory, no high probability threat out there. Anything that was going to be a threat is likely to be something that’s not on our list. Let’s look at two different cases. In either case, the following things have to happen, successfully:
(1) detect the intruder, (2) confirm that it’s on a collision course, (3) assemble the deflection technology, (4) prepare the launch vehicle, (5) launch, intercept, and deflection.

The rock would is in a highly elliptical orbit, and so it was too far away to detect during the survey. That being the case, we aren’t likely to get much of a warning. It’s going to come diving out of the dark beyond the Main Belt, and we’re going to have only a year’s warning or less.
(1) The steeper the approach, the harder it is to detect, because it won’t be moving much against the background stars. It will just be getting bigger.
(2) Likewise, the steeper the approach, the harder it is to get a good orbit, and we have to have a really good orbit if we are going to go to the President or the UN and demand a crash program.
(3) Right now, the only short-term response we have is to blow it up, using nuclear weapons. Of course we’ve never actually accomplished that kind of direct-ascent-to-impact mission. All our asteroid rendezvous missions have been leisurely things that let us use ion engines and the like. What are the other choices? Painting one side of the asteroid so that differential heating will change its orbit. We’ve never done it, we don’t have the equipment, and it takes years for that kind of approach to work. Put up some sort of gravity drag? We don’t have the lift capability. We’re talking a mass that’s an appreciable fraction of the asteroid’s mass.
(4) The launch vehicle part is relatively simple. Nuclear warheads aren’t that heavy. Maybe this one needs additional mass to help in the deflection. The upper stage needs to be maneuverable, but it’s likely we could repurpose a NASA probe. Can we do it inside of a year?
(5) The actual engagement is incredibly difficult. It’s the interplanetary equivalent of ballistic missile defense. There won’t be much time to maneuver, and the fuzing and detonation will have to be near-instantaneous.

Summary: We’re screwed.

Case II
It’s a rock in an Earth-similar orbit, and we just missed it during the survey. This is not unlikely, since there’s a 50% error bar on the total number of near Earth asteroids. This situation is actually pretty survivable.
(1) Unlike Case I, we’d likely detect this kind of rock a few, maybe many, years before it became a threat, unless, of course, NASA suffers some major budget cuts.
(2) Given that amount of time, we can build up an accurate orbit
(3) We still don’t have the technology, but we might be able to crash-program something in time
(4) Still the easiest part of the mission. In fact, we might be able to rendezvous several launch payloads to build a heavyweight package in orbit
(5) This could be a much more leisurely affair, similar to our previous asteroid rendezvous and orbit missions.

Summary: We might be able to pull it off in the not too distant future, but for the near future, it’s not likely.

Of course, those two cases are merely the extremes — an asteroid with an orbit 90º to the Earth’s orbit, and an asteroid with an orbit more or less parallel to ours. The threat runs through that entire arc, in three dimensions, and only a limited part of that arc represents scenarios we have a good chance of solving under current conditions.

So there we are. For the next quarter-century our options range from screwed, to probably screwed. After the middle of the 21st Century, our chances jump to possibly screwed. We are certainly advanced from the benighted 20th Century, but we’re not safe yet. We are in the unenviable position of being the first generation of Earthlings that will see it coming, but we’re not likely to be able to do anyting effective about it, not for another twenty-five years, and only then if the politicians (with their next-election planning horizon) quit cutting the funding.


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One Response to “Dinosaur Killers 2”

  1. Dinosaur Killers 3 – The Science « FoundOnWeb Says:

    […] out, the quiz that kicked off my Dinosaur Killer essays was not about the Earth impact threat at all. Instead, it was about what typeface fonts people […]

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