Look earlier in this thread. I have a suspicion in terms of physics that a net won’t stop an asteroid barreling in at 100 MPS relative to Earth however the idea of a large net-like screen many miles across, (you could drive a bus between the openings,) that applied a uniformly strong counterforce via a collision with the comet or asteroid, by stretching and applying equal resistance over a large surface area might actually be a viable way fo quickly altering the trajectory.

Seriously, I want to see more attention to catch-and-release technology.

Surely someone’s come up with a device that drags a net or otherwise arranges to get caught up and carried along, grabs the comet or asteroid firmly enough that a few ion engine devices can tie themselves down, network themselves, orient themselves, and then start gently steering the asteroid into a path that (with any number of ‘slingshots’ or other careful path selection) will eventually bring it back into a useful orbit, maybe a leading or trailing Lagrange point.

I’d invest in that. Big payback in a few decades.

Of course, if it had turned out the comet was nothing but a huge Lincoln penny, all bets would’ve been off.

http://www.dailymail.co.uk/pages/live/articles/news/worldnews.html?in_article_id=487764&in_page_id=1811

It seems that JPII is now appearing in bonfires….

And just what is it with these former pop stars and physics PhDs?

A rocket deploys a space craft on a rendezvous course which in turn is designed solely to deploy a very large spun carbon-fiber cable net, (sort of like a huge incredibly strong but stretchable fishing net). The secret of the net is its stretching ability which applies a broad force against the asteroid over the timeframe of a collision.

The net, moving rapidly through space toward the asteroid or comet, literally collides with and then envelops it. Though the asteroid/comet continues on its way, the total mass of the giant net rapidly exerts a counterforce over a large surface area of the asteroid rather than a point on its surface. This wide nudge, applied to a large surface area eventually alters its course so that it arrives (for example) a half hour too late to impact the Earth.

“The probe carried no instruments; none could survive a collision at such cosmic speeds.It was merely a small slug of metal, shot out from Discovery on a course which would intersect that of the asteroid.
“As the seconds before impact ticked away, Poole and Bowman waited with mounting tension. The experiment, simple though it was in principle, taxed the accuracy of their equipment to the limits. They were aiming at a hundred-foot-diameter target, from a distance of thousands of miles.
“Against the darkened portion of the asteroid there was a sudden, dazzling explosion of light. The tiny slug had impacted at meteoric speed; in a fraction of a second all its energy had been transformed into heat. A puff of incandescent gas had erupted briefly into space; aboard Discovery, the cameras were recording the rapidly fading spectral lines. Back on Earth, experts would analyze them, looking for the telltale signatures of glowing atoms. And so, for the first time, the composition of an asteroid’s crust would be determined.”

That’ll be Larry Niven, my fave, along with David Brin. ‘Hard’ SF is the only way to go, IMHO..

–Jeff