NASA to Harpoon Comets
It's testing plan now with big crossbow on Earth
By Kevin Spak,  Newser Staff
Posted Dec 14, 2011 2:45 PM CST

(Newser) – Why the heck does NASA need a 6-foot crossbow capable of flinging a projectile up to a mile and generating as much as 1,000 pounds of force? So it can test its designs for a harpoon meant to sink into distant asteroids and comets, of course. NASA is currently hard at work on the OSIRIS-REx, a probe set to launch in 2016 that will fire large harpoons into passing comets and asteroids, retrieving a sample from them that Earth-bound scientists can study, Wired reports.

To figure out how much force that harpoon will need, NASA scientists have built the aforementioned hulking crossbow at the Goddard Space Flight Center, which they keep dutifully pointed down into buckets of dirt and rocks meant to simulate a comet's surface. Though that is an inexact science. "We’re not sure what we’ll encounter on the comet," one engineer explains."The surface could be soft and fluffy, mostly made up of dust, or it could be ice mixed with pebbles, or even solid rock."