5 ms·

Happened to catch rockstar astrophysicist Neil deGrasse Tyson on Charlie Rose the other night and the subject of asteroid deflection came up. For small candidat

Happened to catch rockstar astrophysicist Neil deGrasse Tyson on Charlie Rose the other night and the subject of asteroid deflection came up. For small candidates, vaporization would be ideal. But for larger ones, any attempt at destroying them may have unwanted consequences. Debris fields, partial cleaving, etc. Sending a team of human miners with demolition expertise is not in the cards. So the current vogue in asteroid deflection would be to send something heavy to intercept the asteroid and deflect it a degree or two using only gravitational pull! A very clean and elegant solution that would no doubt make a great simulation or video game ;) Mission Concepts and Operations for Asteroid Mitigation Involving Multiple Gravity Tractors http://www.ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120013195.pdf http://www.ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201...

valarauca1 11y ago
This already exists in a video game. It's call kerbal space program. But instead of gravity you can attach thrusters to asteroids to deflect them. The mod was created by NASA.
- frandroid 11y ago
  What do you think the smilie was about...
chr1 11y ago
A nice thing about this is that it doesn't need to destroy the large asteroid, it just vaporizes small part of it creating thrust and changing the trajectory. One of the videos mentioned bringing asteroids with useful resources closer as a possible usecase.
mabbo 11y ago
The point isn't the vaporize them, it's to nudge them ever so slightly. Consider a comet- you fire one or more lasers to a specific spot on the comet, causing heat. The heat causes the water to expand, and shoot off from the comet. Does this destroy the comet? Certainly not much of it. But as that water vapor shoots away from it, Newtons Third Law comes into play and the comet, ever so slightly, is pushed in the opposite direction. You may rightfully say that this would be a very minuscule push, so what good will it do? Well, if you play Kerbal Space Program you'll quickly learn that tiny nudges can have huge effects in the long-run, especially on big orbits. Add a few mm/s to the velocity of a comet two years ahead of time, and it can make the difference between that comet hitting a planet, or not. It can mean the comet is ever so slightly closer to Jupiter, causing it to be pulled by its gravity just a bit more.
- sandworm101 11y ago
  But KSP does give a false impression. It is very much a "spheres in a vacuum" approach to orbital physics. It doesn't model many/most of the realworld forces. When dealing with the truly minuscule forces such as would be created by lasers aimed at asteroids, one much accommodate all other similarly-sized forces before taking action. Rocks in space are subject to a force/pressure from the sun, a pressure comparable to that from a earthbound laser. Before trying to deflect, one would have to understand how the sun will be altering the course. That calculation is not easy and requires details (albedo/rotation) that are hard to come by for tiny rocks. You don't want to be countering the force from the sun only to push the rock into an intercept it would otherwise have missed. Vaporization also need not mean destroying the rock. So long as the vaporized material achieves escape velocity (not hard on an asteroid) vaporizing the surface of an object creates a force, a thrust, which is greater than the pressure directly from the laser.
  - marcosdumay 11y ago
    > Rocks in space are subject to a force/pressure from the sun, a pressure comparable to that from a earthbound laser. Hum, is it? When near the Sun, yes, of course, but when away from it, we can probably throw way more energy on it than the Sun. Yes, it does require details that we currently can't measure. The good new is that the laser doubles as an excellent instrument for measuring those details.
    - sandworm101 11y ago
      That very much depends on the laser. Most of the approaches I've seen discussed involve multiple 'attacks' on a rock spread out over a considerable period of time. You only fire when the rock is far enough above the horizon (say 25-30% of the time if you have 1 ground laser). And then you want to hit it when it is at some sort of apsis, preferably when it is far away with a relatively slow velocity. The sun has a 24/7 line of sight and is always firing.
      - chr1 11y ago

valarauca1 11y ago

This already exists in a video game. It's call kerbal space program. But instead of gravity you can attach thrusters to asteroids to deflect them. The mod was created by NASA.

frandroid 11y ago
What do you think the smilie was about...

chr1 11y ago

A nice thing about this is that it doesn't need to destroy the large asteroid, it just vaporizes small part of it creating thrust and changing the trajectory. One of the videos mentioned bringing asteroids with useful resources closer as a possible usecase.

mabbo 11y ago

The point isn't the vaporize them, it's to nudge them ever so slightly. Consider a comet- you fire one or more lasers to a specific spot on the comet, causing heat. The heat causes the water to expand, and shoot off from the comet. Does this destroy the comet? Certainly not much of it. But as that water vapor shoots away from it, Newtons Third Law comes into play and the comet, ever so slightly, is pushed in the opposite direction. You may rightfully say that this would be a very minuscule push, so what good will it do? Well, if you play Kerbal Space Program you'll quickly learn that tiny nudges can have huge effects in the long-run, especially on big orbits. Add a few mm/s to the velocity of a comet two years ahead of time, and it can make the difference between that comet hitting a planet, or not. It can mean the comet is ever so slightly closer to Jupiter, causing it to be pulled by its gravity just a bit more.

sandworm101 11y ago
But KSP does give a false impression. It is very much a "spheres in a vacuum" approach to orbital physics. It doesn't model many/most of the realworld forces. When dealing with the truly minuscule forces such as would be created by lasers aimed at asteroids, one much accommodate all other similarly-sized forces before taking action. Rocks in space are subject to a force/pressure from the sun, a pressure comparable to that from a earthbound laser. Before trying to deflect, one would have to understand how the sun will be altering the course. That calculation is not easy and requires details (albedo/rotation) that are hard to come by for tiny rocks. You don't want to be countering the force from the sun only to push the rock into an intercept it would otherwise have missed. Vaporization also need not mean destroying the rock. So long as the vaporized material achieves escape velocity (not hard on an asteroid) vaporizing the surface of an object creates a force, a thrust, which is greater than the pressure directly from the laser.
- marcosdumay 11y ago
  > Rocks in space are subject to a force/pressure from the sun, a pressure comparable to that from a earthbound laser. Hum, is it? When near the Sun, yes, of course, but when away from it, we can probably throw way more energy on it than the Sun. Yes, it does require details that we currently can't measure. The good new is that the laser doubles as an excellent instrument for measuring those details.
  - sandworm101 11y ago
    That very much depends on the laser. Most of the approaches I've seen discussed involve multiple 'attacks' on a rock spread out over a considerable period of time. You only fire when the rock is far enough above the horizon (say 25-30% of the time if you have 1 ground laser). And then you want to hit it when it is at some sort of apsis, preferably when it is far away with a relatively slow velocity. The sun has a 24/7 line of sight and is always firing.
    - chr1 11y ago