NASA: Bring on the asteroid, so we can chuck a fridge at it
Putting Bruce Willis out of work
NASA has okayed one of its save-the-world-from-asteroids proposals to move to the preliminary design phase, on the way to a hoped-for launch early in the 2020s.
If it goes ahead, the DART – Double Asteroid Redirection Test – will start with what the space agency describes as “a non-threatening small asteroid”. That way, presumably, if it gets knocked the wrong way, it won't bring about some kind of metropolitan (or global) catastrophe.
NASA's announcement identifies asteroid binary system Didymos as the target.
Only one half of the binary, though – the smaller half, a mere 160 metres in size (NASA classifies asteroids greater than 1 km in diameter as threatening), Didymos B. The primary in the system (Didymos A) is an impressive 780 metres across.
Being a binary is what makes Didymos a handy test-bed: DART will be designed to change Didymos B's orbit around its primary, not take it out of orbit entirely. That way, the agency's boffins can study the effects of an impact with minimal risk to Earth.
Program scientist Tom Statler says the experiment won't “change the orbit of the pair around the sun”.
Having flown to Didymos, the refrigerator-sized DART will aim itself at the smaller asteroid, impacting it at around 6 km per second (“about nine times faster than a bullet”, NASA explains).
Both the impact and the change to Didymos B's orbit will be visible to Earth-based observatories, so scientists can see how well kinetic impact works on an asteroid.
Only a small change in a threatening asteroid's orbit would be needed to swing it away from Earth, as long as it happens “well before the predicted impact”. ®