July 24, 2021

How to deflect an asteroid with a SpaceX rocket

This Week In Space  brings you what’s new and exciting in space exploration and astronomy once a week, every week. From supernovae to SpaceX or Mars missions to black holes, if it’s out of this world, it’s covered here.

Spaceships like the ones used by SpaceX could be used to pull asteroids away from a collision with Earth, scientists say.

Aleksandra Malysheva/Getty Images/iStockphoto

SpaceX’s Starship may be good for more than transporting cargo, fuel or even humans. According to a recent paper, it could be ideal for future missions to redirect asteroids before they collide with the Earth.

At this spring’s Planetary Defense Conference, Aaron Boley and Michael Byers of Canada’s Outer Space Institute described how a spacecraft like Starship could be used to pull nearby asteroids into safer orbits. The ship wouldn’t have to make physical contact with the asteroid, but could instead act as a “gravity tractor”, staying close and carefully managing its gravitational pull to deflect the rock before it nears Earth.


Yet just as asteroids can be subtly shifted away from the Earth, they can also be nudged toward it. Boley and Byers warn that in the future, if no one controls who visits asteroids (whether for mining, science, or glory) a single botched rocket landing could shove an asteroid onto a collision course with the Earth.

The best policy, then, is to be proactive and manage any asteroids that might pose a future danger. It may not take an asteroid coming right at us for a craft like Starship to be called to action.

Solar sail mission to intercept next Oumuamua proposed

Scientists have concocted a new way to measure and intercept the next Oumuamua-like object to enter our solar system.

Scientists have concocted a new way to measure and intercept the next Oumuamua-like object to enter our solar system.

dottedhippo/Getty Images/iStockphoto

We may never know the true nature of Oumuamua. The interstellar object—which has been explained as a nitrogen comet, a fragment of a Pluto-like planet around another star and even an alien spacecraft powered by a futuristic solar sail—was already heading out of the solar system by the time it was discovered. It was impossible for any probe to catch up to it for a close study. The next time we have a mysterious visitor, though, NASA could be ready—and with a solar sail of its own.

In collaboration with multiple private space corporations and UCLA, NASA’s Jet Propulsion Laboratory has proposed a mission to rendezvous with the next Oumuamua-type object that enters the Solar System. To do so, it would use a solar sail: a huge, lightweight sheet designed to be thrust forward by the physical pressure of the sun’s radiation.

The mission envisions a 100-pound spacecraft powered by a sail about as big as a football field, but narrower than one-tenth the width of a human hair. The whole thing would “park” in an orbit close to the Sun. When the next Ouamuamua is discovered, the craft would turn and launch after it, quickly attaining speeds of over 50,000 mph. It would be able to intercept the visitor in a matter of days, take remote measurements, and then crash on purpose to generate a cloud of debris for astronomers to study.

The collaboration hopes to do a demo mission in 2025 and move on to a full intercept within the decade. If successful, it would provide the first-ever sample of material from another planetary system, and with it, a major clue to understanding the building blocks of planets everywhere.

China to build solar power array in space

Solar power transmitted from an orbiting satellite

Solar power transmitted from an orbiting satellite

Mmdi/Getty Images

China announced plans to build a solar power plant in orbit above the Earth. The costs involved—and international displeasure—may pose obstacles. But if achieved, the technology would be much more efficient than solar farms here on Earth, which have to deal with the atmosphere and Earth’s shadow blocking the sun’s rays.


A space-based solar array is ambitious, even for China. According to Andrew Jones at SpaceNews, constructing the array would involve over 100 rocket launches of about 10,000 tons of material. Assuming the launch vehicle’s price tag falls somewhere between the cost of the beleaguered Space Launch System and the efficient Falcon Heavy, that puts the launches alone at around $100 billion, enough to run all of NASA’s projects for five years.

Even if China is willing to hand over the cash, there’s no guarantee the rest of the world would allow it. Because energy from the solar farm would be sent down to Earth in an intense microwave beam, the array would have to be kept out of the way of other satellites—or vice versa.

The aim is to have a facility up and running by 2030. Only decades later, in 2050, would it grow to produce energies comparable to an Earth-based power plant. Perhaps someone could interest China in another $100 billion project (say, 25,000 wind farms, or 100 nuclear power plants) instead?