Asteroid question

[joema]

@Gray_Ghost

…if you want to use a nuke to move the asteroid, use it to vaporize a puck of polyethylene next to the device, and let the momentum from that now quickly moving plasma cloud move your Rock of Doom. If the nuclear device can have its radiation directionally biased, as opposed to radiating uniformly in all directions, even better…

That might work, but it wouldn’t be necessary to do that. A nuclear detonation in space produces no blast and no fireball, only a brief burst of intense neutron and X-radiation. A precision stand-off detonation would vaporize the outer layer of the asteroid, whether it was a monolithic body or a rubble pile, producing an opposite impulse.

See “Deflecting Asteroids By Means Of Standoff Nuclear Detonations”, (Glennary, 2004): http://research.dynamicpatterns.com/wp-content/uploads/2011/03/Deflecting-Asteroids-by-Means-of-Standoff-Nuclear-Explosions.pdf

However for the OP scenario the asteroid (2019 OK) was only detected about 24 hr in advance. If it had been on a direct earth-intercept trajectory, it’s unlikely any nuclear device and launch system could deflect it within the available time – even had one been ready and available.

The above paper states that for objects smaller than about 100 meters diameter, they could probably be destroyed or fragmented to sizes that would burn up in the atmosphere. Asteroid 2019 OK was 17 - 39 meters, so hypothetically that could be an option given a prepared system. Above that size, deflection is the only option and even using nuclear methods this takes more than 24 hr warning time.

However the Chelyabinsk meteor of 2013 was only estimated at about 20 meters diameter and the lower end of the 2019 OK size estimates are smaller than that. Even if a nuclear intercept system was available it might not be worth the risk for such a marginal case.

[Darren_Garrison]

There was a study on blowin’ up asteroids published earlier this year.
(tl;dr: if a doomsday asteroid is on the way, be prepared to bend over and kiss your ass goodby.)

[KarlGauss]

@Gray_Ghost

. . . For your Tunguska rock, it doesn’t even matter if it strikes the Earth…provided the impact is over an ocean or similarly uninhabited area. Satellites catch kt level air bursts from bolides all of the time.
No one cares because they’re over the ocean, at 200,000 feet or so, or both.

Something like Apophis, hitting an average depth of ocean with a ~1GT of TNT impact, is going to cause a minor tsunami 500 miles away or so . . .

Could this type of thing account for the 1979 Vela Incident after all?

[Gray_Ghost]

@KarlGauss

Could this type of thing account for the 1979 Vela Incident after all?

I don’t think that you get a double flash from an impacting bolide, versus a nuclear fireball, but I definitely could be wrong. See this explanation of the physics behind the double-flash. There isn’t the prompt radiation causing incandescence ahead of the hydrodynamic shock front for a bolide.

Also, a bolide wouldn’t cause the anomalous I-131 levels in Australian (but not New Zealand) sheep. I did think that the double-flash usually scaled to device yield, and indeed according to the wiki, that double-flash is what you’d expect from a 2-3 kT device. Which is awfully small, now that I think of it, but probably large enough to serve as a decent primary for something bigger.

Neat article, joema, thanks. I like that they mention the anisometric nature of neutron radiation from a nuclear device, and utilizing that asymmetry.

So, how much impulse would it take to deflect a dead on asteroid in the OP to a non-Earth-colliding trajectory, if the asteroid were 24 hours from impacting?

[carnivorousplant]

@Gray_Ghost

So, how much impulse would it take to deflect a dead on asteroid in the OP to a non-Earth-colliding trajectory, if the asteroid were 24 hours from impacting?

An Enterprise tractor beam, and even that didn’t work in *The Paradise Syndrome.
*

If you had time, would it be better to hit the asteroid with a probe, or land an engine and fuel on it to change the trajectory?