This month The Economist published The World If, a compilation of future scenarios to accompany its annual collection of predictions for the year ahead, The World In. Among these was discussion of a crisis game developed by Paul Chodas, a Near Earth Object (NEO) expert at NASA, for the International Academy of Astronautics 2015 Planetary Defence Conference held this April in Italy. The simulation envisaged a large asteroid on an apparent collision course for Earth:
ON APRIL 13th 2015 the Minor Planet Centre (MPC), an office with a staff of six which looks after such matters for the International Astronomical Union, recorded hundreds of newly discovered asteroids—a typical daily haul. The one to which it assigned the name 2015 PDC, though, stood out.
When asteroids are discovered in orbits that come close to the Earth’s, as this one did, the MPC makes various calculations to see if they pose a threat. Because observations of small, distant rocks cannot be made with perfect accuracy, those calculations define a “corridor” where the asteroid might be. The calculations for 2015 PDC showed that on September 3rd 2022 the Earth would cross the corridor where the asteroid might be. The two might collide.
As 2015 PDC’s orbit became better known the corridor in which it might be on that fateful day in 2022 shortened. But it still contained the Earth. By June the probability of an impact had risen to 1%, making it the most threatening asteroid astronomers had ever seen. By September governments in America, Europe, Russia and China had started work on space missions aimed at changing the asteroid’s orbit by ramming into it. Even at a speed of more than 10km (6 miles) a second, hitting a billion-tonne asteroid with a few tonnes of spacecraft will make only a minute difference to the asteroid’s orbit.
You can find the scenario as provided to the participants via the NASA JPL website (archive version).
Much of the asteroid’s predicted impact area was ocean.
One participant, representing India, argued that the effects of this could be dealt with by the same sorts of measures used to address any tsunami. Indeed, many of those measures would also have later value as protection against the general rise of sea level due to ongoing global warming. Rather than “take the hit,” however, most of the players supported trying to deflect the approaching asteroid.
That effort, however, went somewhat awry:
…in Dr Chodas’s scenario the deflection went wrong. Instead of being nudged safely onto a new trajectory, the asteroid was cleft in two. The larger part had been given a big enough impulse to no longer be an imminent threat, but the smaller part was still on a collision course. And now its orbit was newly uncertain. The corridor that had been shortening was lengthened, with the once-threatened, then-safe places between Vietnam and Tehran newly at risk again thanks to the actions of space programmes that were mostly based in places (Europe, America, Russia) that were at no direct risk at all. India began work on a mission that would use a nuclear warhead to try to blast the new fragment to smithereens on its final approach—but which might have simply changed its impact point again.
China warned that it wanted a veto over any such mission; if it did not approve of the way it was being done it would feel justified in using anti-satellite weapons to shoot down the Indian rocket pretty much as soon as it took off. Iran, previously safe, fulminated against the Great Satan, and it was hard not to think it had a point. Hannes Mayer, an Austrian lawyer who has given the application of space law to such situations a lot of thought, raised the possibility that by altering the asteroid’s orbit the intercepting nations changed its legal status from that of a “celestial body” for which no one was responsible to that of a “space object”—and thus become liable for any damage that it did.
By the end of the scenario, when the asteroid was a few days from exploding in the sky over Dhaka with more power than 1,000 Hiroshima bombs and more than 20m people were being evacuated, that was looking like a great deal of liability. The question of India’s last-ditch nuclear interception, and China’s worries, were brushed aside as beyond the scenario’s scope. In the real world, though, a botched interception which created a crisis for people who would otherwise have avoided one would be a grave issue—perhaps, in some circumstances, casus belli.
All-in-all, the simulation seems to have highlighted several payoffs from crisis gaming: exploration of complex decision-making processes (who decides on behalf of planet Earth?); testing of analytical approaches (in this case, a JPL NEO impact prediction tool); identification of alternative courses of action; risks from second and third order effects; and even some counter-intuitive findings (under some circumstances it might be better to allow an asteroid to hit).
h/t Charles Vasey, via the Simulating War discussion group