There's no need to freak out yet, however. Lawrence Livermore National Laboratory (LLNL), NASA and the National Nuclear Security Administration are on the case, and they're thinking about wielding a big Hammer.
Hammer stands for "Hypervelocity Asteroid Mitigation Mission for Emergency Response," which is an impressive name all on its own. Hammer's a concept at the moment, but if built, it would be a 30-foot-tall (9 meter), 8.8-ton spacecraft that could act as either an asteroid battering ram or as a delivery vehicle for a nuclear device. Let's call it the "nudge or nuke" option.
Bennu is a beast, according to the national lab. It's 1,664 times as heavy as the Titanic and measures more than five football fields in diameter. If it hit Earth, the impact would unleash 80,000 times the energy of the atomic bomb used on Hiroshima in 1945. It would be devastating.
Hammer is designed to launch using NASA's Delta IV Heavy rocket. Researchers at Lawrence Livermore published a paper in the journal Acta Astronautica in February that evaluates the options for using the spacecraft to successfully encourage Bennu to redirect from Earth.
The researchers say ramming the asteroid to change its course would be ideal, but it would need to be a "gentle nudge" that doesn't cause it to break up. It's a complicated proposition.
The team looked at a variety of scenarios. For example, if Earth started launching Hammer missions just 10 years before impact, "it was determined that it could take between 34 and 53 launches of the Delta IV Heavy rocket, each carrying a single Hammer impactor, to make a Bennu-class asteroid miss the Earth," the lab reported on Thursday.
All of this makes it sound like a gentle nudge might not be the best solution for big asteroids.
(Score: 2) by takyon on Monday March 19 2018, @09:20PM
BFR will be able to lift over five times the payload to LEO of Delta IV Heavy, in fully reusable mode. Not sure how that translates to other orbits, but probably "very well".
Reusable BFR launch cost could become lower than Falcon 1, which was $5-6 million:
https://www.universetoday.com/138821/first-spacex-bfr-make-orbital-launches-2020/ [universetoday.com]
Let's say that at the high end, with few launches under its belt, BFR might be closer to $40 million (cheaper than Falcon 9).
So there will be a rocket that can lift a lot more than Delta IV Heavy, for 1-10% of the cost per launch.
The summary mentions stopping a "Bennu-class" asteroid. 101955 Bennu [wikipedia.org] has a "1-in-2,700 chance of impacting Earth between 2175–2199". If we don't have better space technology by then, it will be because we wiped ourselves out with nukes rather than an asteroid.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]