What to do if it does happen
NASA-organised war-gaming reveals complexity, complications and deep concern. RICHARD A. LOVETT reports.
DEADLY ASTEROID STRIKES are a staple of science fiction, but recently NASA took it kind of for real.
Over the five days of the International Academy of Astronautics’ 2019 Planetary Defence Conference in Maryland, US, it developed a scenario in which an asteroid moved from having a one-in-100 chance of striking the Earth to actually obliterating a big chunk of New York City.
Each day, participants were presented with fictional press releases that tracked crucial steps in an emergency that developed over eight years.
“We’re scientists pretending that we are actors playing scientists who happen to be ourselves,” joked Mark Boslough, a physicist at Sandia National Laboratories, New Mexico.
The exercise began with the announcement that an asteroid had been spotted on potential collision course with Earth, but that the odds of impact were 1%.
By day two, astronomers had refined their calculations of its orbit by enough to raise that to 10%. These same hypothetical observations also found the asteroid’s size was between 140 and 260 metres – too small to be a dino-killer, but big enough to pack a serous wallop if it hit.
At this point, the assembled scientists concluded it was time to start taking action, with an eye to deflecting the asteroid. There were two possible courses of action: hit it with a fast-moving rocket at a crucial point in its orbit or explode a nuclear device close above its surface. The latter strategy, of course, is currently prohibited by international law.
“You only need a few centimetres per second [change in velocity] to move
it thousands of kilometres [by the time it reaches the Earth],” explained Paul Chodas, of NASA’s Centre for Near Earth Object Studies in Pasadena, California. That said, you can’t deflect an asteroid if you don’t know the right direction to move it, or even if it really is on collision course.
To resolve that, the scientists concluded that the first step had to be to build and launch a reconnaissance mission. Additional spacecraft, ranging from a reconnaissance mission capable of rendezvousing with the asteroid to a fleet of asteroid-deflection spacecraft, were also urgently needed.
“We are looking at one to 10 Falcon Heavy impactors,” said Brent Barbee of NASA’s Goddard Space Flight Centre, Greenbelt, Maryland.
Falcons are a family of rockets built by the private company Space Exploration
Technologies, or SpaceX. The Falcon Heavy is the biggest of the bunch, capable of carrying the largest payload of any currently operable launch vehicle.
Unfortunately, the precise number of such rockets wouldn’t be known until the flyby satellite got to the asteroid, but, added Barbee, “we have to begin construction of whatever vehicles we are going to commit to, right now. And spacecraft could fail, so we need to include that in our thinking.”
Fast forward to December 2021. In the third press release, data from the flyby mission revealed that the asteroid was heading for somewhere near Denver, Colorado.
“The obvious thing to do is to deflect this thing,” Boslough noted on receiving the news. “We still have five years.”
The next update, dated September 2024, revealed that six Falcon Heavy rockets were built, but only three found their target. Three failed at launch or en route. Nuclear devices were not deployed.
The surviving three rockets would still have been enough to deflect the asteroid, but there was a problem. One hit hard enough to break it into two pieces. The larger fragment was deflected away from Earth, but the smaller one, about 60 metres across, was merely nudged hard enough to deflect it away from Denver. Instead, it wound up on course for an indeterminate location in the eastern US, or maybe the Atlantic Ocean.
Worse, Barbee said, the reconnaissance satellite observing the deflection attempt was hit by debris and knocked off line, making it impossible to calculate exactly where the fragment would hit.
It was still possible, he added, to launch a nuclear-equipped mission capable of either deflecting the asteroid fragment or breaking it up into tinier fragments that – if they reached Earth at all – would burn up harmlessly in the upper atmosphere. But such a mission had to be approved, built, and launched within 12 months.
Fast-forward one final time, to the last day of the exercise, just 10 days before the impact.
Blowing the thing up, as Bruce Willis did in the 1998 film Armageddon, wouldn’t get off the ground, the war-gaming team decreed, due to either lack of time or lack of political will.
As a result, the asteroid fragment got close enough for Earth-based radar to track its course with high precision. It was headed directly for the heart of New York City, which it would hit with the force of a 15 megatonne bomb. (To compare: the atomic bomb that levelled Hiroshima in 1945 had a yield of just 15 kilotonnes.)
New Yorkers would have been well aware that they might be in the asteroid’s cross-hairs, Chodas’s team said, but now that the scientists knew exactly where the asteroid would hit, emergency managers had 10 days to evacuate 10 million people.
All of this, of course, was simply a hypothetical scenario, but it was played out with excruciating attention to detail.
Conference organisers stressed that the exercise was not designed to represent a truly likely real-world scenario; it was intended to highlight ways in which things might go wrong.
“One of the things I take away from this is we probably should have been planning the back-up options from the beginning, just in case,” Barbee said.
RICHARD A. LOVETT is a science writer and science fiction author based in Portland, Oregon.