No Salvation

I recently watched a few episodes of the television show Salvation, a science fiction, disaster thriller with soap opera overtones.  It's a Deep Impact knock-off - MIT grad student discovers asteroid headed for Earth, improbable conspiracies of silence are revealed, beautiful people fall into bed with each other.

I know that appreciating this sort of thing requires a big effort at suspension of disbelief, and I was prepared to ignore to ignore giant plot holes, the grad student's attempts to solve the 3-body problem using "gravimetric data" (WTF?), and the Elon Musk type inventor demanding and getting billions to develop a Newton's Third Law violating EM drive, but they managed to break me anyway.

The last straw was the arrogant and pig-headed government scientist (all the scientists here are dull, arrogant, pig-headed, and spend a lot of time saying "you're insane," mostly to the Elon Musky guy) declaring that they would crash a Jupiter probe into the asteroid fragmenting it into pieces which would mostly hit Russia and China and kill a billion people.

Now I've studied the real "Deep Impact" mission which crashed a high velocity probe into Comet Tempel 1, and I know that even a cometary pile of dust like Tempel 1 is not so easy to disrupt, so a rock-like, much bigger asteroid is not going to be any piece of cake.  The gravitational binding energy of a massive object is roughly G*M^2/R (5*G*M^2/(3*R) for a uniform sphere), where G is Newton's constant, M is the mass, and R the radius.  Working out the numbers for a 10 km asteroid gives about 10^18 Joules gravitational binding energy.  (If the asteroid is iron or rock, the chemical binding energy for this size asteroid would be of the same order of magnitude - a few tens of kiloJoules per kg.)  A heavy space probe (2000 kg) moving at 10 km/s has a kinetic energy of 10^11 Joules - much too small to do more than knock a few chips off the asteroid.   How about a 10 Megaton H-bomb?  It's energy release is 4.18 * 10^16 J, so it would still be too small by a factor of 50, even if you could get it to deposit all of its energy in the asteroid.


Popular posts from this blog

Left, Right and Indian


Ethics, Economics, and Climate