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Could paint save us from a doomsday asteroid?

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bison
Posted (edited)

The Gizmodo article, which inspired this thread, doesn't explain too well about how painting an asteroid, like Bennu, would change its course thru space. It's pretty simple in its basics, really.

Color one side of the asteroid white, and that side will reflect more sunlight back into space. Doing so will impart a slight thrust, pushing the asteroid in the opposite direction. Given a long lead time, this slight thrust could be enough to shift the asteroid's orbit away from Earth. 

A fairly elegant, subtle solution, compared to blasting it, or even just nudging it aside with a nuclear bomb.

   

Edited by bison
added information, edited for accuracy
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Merc14
1 hour ago, bison said:

The Gizmodo article, which inspired this thread, doesn't explain too well about how painting an asteroid, like Bennu, would change its course thru space. It's pretty simple in its basics, really.

Color one side of the asteroid white, and that side will reflect more sunlight back into space. Doing so will impart a slight thrust, pushing the asteroid in the opposite direction. Given a long lead time, this slight thrust could be enough to shift the asteroid's orbit away from Earth. 

A fairly elegant, subtle solution, compared to blasting it, or even just nudging it aside with a nuclear bomb.

   

What is it is tumbling?

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Grandpa Greenman

Nuking it would be more fun, though.  

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bison

Tumbling would presumably reduce the efficiency of the thrust, if it meant that the painted half of Bennu faced the Sun less frequently, and sometimes less directly, than it would in the case of simpler rotation.  

I'm also concerned by the fact that Bennu has a fairly short orbital period. It travels between Mars and Earth most of the time, but also dips inside Earth's orbit.The cumulative effect of slight thrust  would increase the size of its orbit.

This seems to mean that Bennu could be pushed nearer Earth around the time of its perihelion.  Bennu will pass inside Earth's orbit many times in the course of 120 years before the closest approach is predicted, this would appear to present a problem, once we started tinkering with its orbit.   

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Nzo

Lets back up here a bit. Just a little bit. You would have to launch into space hundreds if not thousands of gallons of paint then remotely(or if you are adventurous, pre programmed) have some kind of robot spray one half of an asteroid. And we would be praying it sprays the proper side of the asteroid. This is another one of those ill thought proposals made by an intern, or worse.  The payload would be MASSIVE and painting in space with zero G is probably infinitely harder to do than painting with gravity because every time you press on that nozzle it acts as a booster.

 

A full 40 megaton nuke package delivered close to it and exploded would probably be the cheapest and most effective solution and it would also rid the world of a small percentage of nukes.

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bison
Posted (edited)

A load of fine, white powder, set to strike the asteroid and burst open with enough speed to distribute it widely would seem to be simpler. Maybe several loads to strike different areas and so improve the coverage.

I don't think it matters which side is 'painted', so long as its confined to that one side. Then every time that side of the asteroid rotates around to face the Sun, it would reflect the light and give a slight push, away from the Sun. 

By the way I don't think it was an intern (or worse) who thought this up. The Gizmodo article says that it came from Dr. Michael Moreau, NASA's OSIRIS Rex project, Flight Dynamics System Manager.

Edited by bison
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paperdyer

I see issues with the paint and powder plan.  The paint formulation would need to be able to be a liquid, or at least a paste in the cold of space.  On the powder plan, doesn't that depend on the asteroid have enough of a gravity field that the powder just doesn't float away?

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bison
Posted (edited)

With a slow enough impact, most of the powder should probably fall back onto the surface. (no atmosphere to keep it suspended.). The low gravity could allow it to spread widely, even from a fairly low energy impact. 

I doubt that any of this will be necessary, where asteroid Bennu is concerned. The odds of an impact with Earth are currently about 1 in 2700. In the past, the odds of one or another near Earth asteroid striking Earth have increased, the longer the object's orbit was studied. There are a great many ways an asteroid could move, and most of them don't pass very near the Earth. 

Thinking about how to control the motions of near-Earth asteroids in general still seems a good idea. Eventually, one will be found that truly has our name on it.   

Edited by bison
improved composition

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Hankenhunter

I personally like the solar sail idea. Let the sun do all the work. 2nd would be some type of cluster thrusters. 

Hank

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Merc14
50 minutes ago, Hankenhunter said:

I personally like the solar sail idea. Let the sun do all the work. 2nd would be some type of cluster thrusters. 

Hank

Cluster thrusters?

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Hankenhunter
Posted (edited)
1 hour ago, Merc14 said:

Cluster thrusters?

Some thing I thought of a while back. Auto rock bolt anchored pocket thruster packs attached at key points on the rock. I haven't figured out the thrust part yet but I'm thinking of something that could make its own fuel once anchored. Ya, I know it's a bit out there but dare to dream. If ice was available on the rock it would be easier. It's the solid nickel and iron ones that keep me running into a wall.

Hank

 

Edited by Hankenhunter

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Peter B
On 3/23/2018 at 0:19 PM, Nzo said:

Lets back up here a bit. Just a little bit. You would have to launch into space hundreds if not thousands of gallons of paint then remotely(or if you are adventurous, pre programmed) have some kind of robot spray one half of an asteroid. And we would be praying it sprays the proper side of the asteroid. This is another one of those ill thought proposals made by an intern, or worse.  The payload would be MASSIVE and painting in space with zero G is probably infinitely harder to do than painting with gravity because every time you press on that nozzle it acts as a booster.

 

A full 40 megaton nuke package delivered close to it and exploded would probably be the cheapest and most effective solution and it would also rid the world of a small percentage of nukes.

You are a negative nelly, aren't you. Most of the issues you describe don't seem terribly hard to resolve.

1. Launching hundreds or even thousands of gallons? Well, I think powder would work better, but the mass wouldn't be a major issue. Consider that the Falcon Heavy can launch over 16 tons to Mars, so given the location of the asteroid, that means 16 tons could be sent there too. Assuming only half the spacecraft is "paint" (of whatever sort), that's 8 tons, which is over 2000 of your weird American gallons. So we already have the launch capacity with a single rocket.

2. Have some kind of robot spraying? Well, the effect doesn't have to be perfect. Just make the sun side of the asteroid considerably lighter coloured. So it wouldn't matter if the paint job was a bit blotchy. The reason I think powder would work better is that it could be dispersed from a distance using some sort of low-energy gas-powered process: the powder would drift onto the asteroid at low speed, gradually assisted by the asteroid's minute gravity.

3. Spray the proper side? Are you serious? What exactly leads you to think that a spacecraft intended to be on the sunny side of an asteroid with its business end pointing away from the Sun might end up on the shady side of said asteroid with its business end pointing at the Sun? And even if it did, I fail to see how there'd be any problems moving the spacecraft to the correct position and facing the correct direction.

4. Payload would be MASSIVE? Yeah, no. We already established the Falcon Heavy is already a player in the game. In any case, given that this sort of solution is intended for long term problems, it probably wouldn't be a major issue to launch a second spacecraft. Or a third.

5. Nozzle acting as a booster? Wouldn't be much of a boost though. Remember, you've already said that the spacecraft would be MASSIVE, so the acceleration generated by this thrust would be minute. Plus, remember that time is on our side - it wouldn't matter if the spacecraft took a year to do the painting, so the rate of spraying could be very low. So low that the asteroid's gravity might even be sufficient to cancel it out. And if not, ion thrusters would be sufficient to counteract the thrust of a spray gun. Finally, my idea of a powder-puff system wouldn't even generate any thrust at all.

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Peter B

Actually, another powder dispersal system might be as simple as landing a device on the surface. It consists of a large container of white powder and a low-powered gas blower aimed at the pile from above. After landing, the container opens up and the powder collapses slowly into a low heap. Then you fire up the gas blower, which would disperse the powder in all directions. The effect is intended to mimic the effect of the Apollo lunar module descent engines, which did a very good job of blowing away dust particles directly underneath.

Given Bennu's extremely low gravity, it wouldn't take much energy at all to push powder sized particles a couple of hundred metres...

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