# Surviving the apocalyspe [duplicate]

It's 2020 and the world's astronomical organizations have just realized something: an asteroid (they have named it Potens) 10x larger than Chicxulub is racing towards the earth.

How could the earth survive given that

1. This is 2020, so their technology is not very advanced.

2. Nations still argue.

3. They know 5 years in advance.

In response to "Fly a probe up there that has a rocket engine to push it just enough out of the way." answers:

Chicxulub's mass is in the range of The mass is in the range of $1.0 \times 10^{15}$ kg to $4.6 \times 10^{17}$ kg. Therefore, Potens' mass is in the range of $1.0 \times 10^{16}$ kg to $4.6 \times 10^{18}$ kg. Assuming that the upper bound is correct, to move it at 1 cm per year, we would need a force of 1457683190 newtons. That's one big probe. (source)

• One year means we're toast. You need to give more time for something of that size to be deflected, or you need to make it smaller so that it will not wipe everything out so utterly.
– hyde
May 25 '15 at 20:25
• Did Aerosmith start playing in anyone else's mind after reading this question? ♪ ♫ I still miss you babe, and I don't want to miss a thing! ♪♫ May 25 '15 at 22:15

While I hate to say it, the movie "Armageddon" had the right idea. No, no, hear me out.

Let's assume that Poten (mass = 5 x 10^18 kg) is set to make bullseye impact - that is, its' trajectory passes through the center of the earth. Let's say that, 2 years before impact, a rather large nuke is set off at Poten's core. If large enough, this will produce an approximately spherical shell of debris. If the nominal diameter of the shell is 10 times the earth's diameter, then only about (2 x pi x R^2) / 4 x pi x (10 R)^2 of the total mass will impact the earth, where R is the earth's radius, about 6400 km. For these numbers, the expected impact mass is decreased by a factor of 200, for a total of about 2.5 x 10^16 kg.

The velocity required to get the shell to this speed is (6.4 x 10^7) / (6.2 x 10^7) m/sec, which just happens to be 1 m/sec, since a year is 3.1 x 10^7 sec.

The energy required to produce this velocity is, of course 1/2 mv^2, which in this case is about 2.5 x 10 ^ 18 J. Since 1 MT is equivalent to 4 x 10 ^ 15 J, we'll need about 600 MT. The largest nuke ever set off was the Tsar Bomba, and at 50 MT it was crippled by being configured to 50% of theoretical yield. So we'd only need 6 full-up Tsar Bombas to do the job.

For the next 3 months, all efforts are concentrated on tracking the fragments, identifying the ones still on a collision course, and prioritizing them by mass. Then a second wave of Bruce Willises arrives and sets more nukes, and the cycle repeats. There's some uncertainty as to how big the actual debris chunks are - the absolute best case is that only a few pieces are produced, and those will all miss. But let's say that the largest pieces are 1% of the original mass. Then you only need 6 MT per chunk for a successful deflection.

The process continues for the next year, and assuming a 99% deflection rate per 6 months, the mass impacting on earth will be on the order of 2.5 x 10^10 kg. This will, of course, be pretty nasty, but it's a million times less than Chicxulub. Just as important, the arriving swarm will consist of multiple objects rather than one big one, and the total effects will be much less, since atmospheric effects will be much more pronounced, and a lot of the smaller pieces won't make it to the ground. At a minimum, the impacts will be divided into two separate waves, corresponding to the leading and trailing surfaces of the debris shell.

All of this, of course, depends on getting the nukes to the right place at the right time, and I'm not real optimistic about this. But the priniciple seems sound.

And, as note, the ability to plant the nukes at the core of Poten and its brood is problematic but not necessarily fatal. It's not actually necessary to get to the exact center. An off-center blast is actually better, as long as the asymmetry axis is perpendicular to the line of motion. The result is a small, fast ejection in one direction with a larger piece moving more slowly in the opposite direction. If you can get deep enough to produce something like a 10-1 imbalance, you can essentially solve the whole problem with one shot, although the bomb has to be a bit bigger. As the pieces get smaller, you can get away with bigger asymmetries as long as you use bigger bombs, and with an upper limit of 100 MT per nuke that's not a problem.

If the collision is unavoidable, the nations scramble to send up as many people/spacecraft as they can to "dodge" it. Using the latest ion-drive craft, perhaps emergency mission to Mars even though they're not ready for it, etc.

Gather the world's nuclear arsenals plus whatever a crash-priority program can build in time.

Use what you need for an Orion booster, the booster carries a bomb-thrower that lobs the bombs at the rock as it gets close enough to aim accurately. (Note that it will probably need to roughly match orbits in order to remain close enough for long enough to get all the bombs off without causing fratricide.) Since the asteroid doesn't have a proper pusher plate the detonating bombs will erode it somewhat but this doesn't matter. The issue is if you have enough delta-v to generate a miss.

If you don't, you bend forward far enough to kiss your nether regions goodbye.

While in theory a bunker in a mine in a seismically stable area far from the point of impact could weather this the human factors are another matter. You're going to end up with a bunch of powerful people in that bunker who aren't able to rebuild when the come out into a land that's blasted back to the level of microbes--and you'll only get that far if somehow you manage to avoid a collapse of society fighting over admission to the bunker.

The correct answer is to send a bunch of rough and dirty oil riggers with loads of drilling experience up in space shuttles to intercept the asteroid as it passes the moon, then have them land on the asteroid with drilling rigs, drill to the center of the asteroid and lower a nuclear device into it's core and blast the the asteroid from the middle, this will split the asteroid in two and both halves will conveniently miss the earth on either side of the planet.

Just remember to bring a couple extra remote detonators, you wouldn't want to leave someone behind to detonate manually, and bring a copy of Star Wars with you, the Russian guy you pick up at the ISS hasn't seen Star Wars.

• Chicxulub's mass is in the range of The mass is in the range of $1.0 \times 10^{15}$ kg to $4.6 \times 10^{17}$ kg. Therefore, Potens' mass is in the range of $1.0 \times 10^{16}$ kg to $4.6 \times 10^{18}$ kg. Assuming that the upper bound is correct, to move it at 1 cm per year, we would need a force of 1457683190 newtons. That's one big probe. May 25 '15 at 20:28