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Sky_Render
Sky_Render HalfDork
2/19/13 12:22 p.m.
PHeller wrote: Which leads to another question: Could such a huge object be slowed down?

Yes. It is simply a question of force and time. The object is massive, but Physics tells us

F = ma

or FORCE = MASS x ACCELERATION.

Therefore, acceleration is simply force divided by mass. So, you could use an explosion to impart a large force that would cause a correspondingly large acceleration (change in velocity or delta-v).

Or, you could use thrusters or gravity to impart a small force over a much longer period of time and achieve the same result.

Nuculer explosions are cooler, though.

aircooled
aircooled PowerDork
2/19/13 12:32 p.m.
PHeller wrote: ...Which leads to another question: Could such a huge object be slowed down?

Probably the most practical way would be to do some path adjustments to do some gravity assist braking. You could do atmospheric braking, but that could be very risky of course (but visual spectacular and might involve some breaking ).

There would be an impressive amount of math involved and would depend on relative motions, might involve the moon etc. It would probably take a good amount of energy, or a good amount of time to get it done. You want it fast, or you want it cheap? Pick one.

4cylndrfury
4cylndrfury UltimaDork
2/19/13 12:48 p.m.
Sky_Render wrote: Nuculer explosions

Curmudgeon
Curmudgeon MegaDork
2/19/13 12:54 p.m.

The asteroid is already slowing down, entropy says that everything slows down and cools off. It just doesn't happen very fast. Yeah, I know the term entropy is normally used referring to thermodynamics, but you get the idea. Things still slow down in a vacuum, btw: http://www.geekosystem.com/friction-in-vacuum/

Sky_Render
Sky_Render HalfDork
2/19/13 12:55 p.m.
4cylndrfury wrote:
Sky_Render wrote: Nuculer explosions

LOL, exactly why I spelled it "Nuculer."

DrBoost
DrBoost PowerDork
2/19/13 1:01 p.m.

Send Chuck Norris into orbit. That sissy pebble doesn't stand a chance.

[/end thread]

codrus
codrus GRM+ Memberand Reader
2/19/13 1:30 p.m.
Sky_Render wrote: Wouldn't you have to make the tractor of appreciable mass for it to have a noticeable effect?

Imagine you went up and bolted a rocket engine to the asteroid and turned it on -- that would let you thrust it away from a dangerous path, right? This is exactly the same, except that the "bolt" is the gravitational force between the two objects. () Since the asteroid is pretty small as far as rocks in space go, that force is very weak, so the amount of thrust you can deliver is low. OTOH, if you've got 20 years til the "keyhole" event, and that keyhole is 800m wide, then you only need to move at most 400 meters at the end of those 20 years, so you don't need* to do much.

If you were to wait til after it went through a keyhole in 2029, then you'd have a much harder job on hand -- 7 years in which to move it 4000 miles (far enough to miss the entire Earth).

Low thrust over extended periods of time is what an ion engine is really good at. They're useless for launching spacecraft because the thrust is too low, but that's not a problem here.

(*) You also need to make sure that the exhaust from the the tractor doesn't hit the asteroid, otherwise you're counteracting that gravity. So either the tractor flies around in circles thrusting at angles away from the asteroid, or you put three engines on it that point backwards in a triangle so that they miss the asteroid.

Duke
Duke PowerDork
2/19/13 2:00 p.m.
4cylndrfury wrote:
Sky_Render wrote: Nuculer explosions

He's just the latest in a long line of US presidents and others who should know better. He is far from the inventor of that little bit of stupidity.

JThw8
JThw8 PowerDork
2/19/13 2:06 p.m.

This is why I love this place. What other car forum could you post about things of this nature and get such well informed responses?

And I will freely admit I seem to have misinterpreted what he was saying about the keyhole, he didn't dwell on it so I must have misinterpreted it. I was also PWD last night so I'm surprised I even came close to explaining it.

Beer Baron
Beer Baron PowerDork
2/19/13 2:09 p.m.
Duke wrote:
4cylndrfury wrote:
Sky_Render wrote: Nuculer explosions
He's just the latest in a long line of US presidents and others who should know better. He is *far* from the inventor of that little bit of stupidity.

mistanfo
mistanfo SuperDork
2/20/13 5:02 a.m.
Curmudgeon wrote: The asteroid is already slowing down, entropy says that everything slows down and cools off. It just doesn't happen very fast. Yeah, I know the term entropy is normally used referring to thermodynamics, but you get the idea. Things still slow down in a vacuum, btw: http://www.geekosystem.com/friction-in-vacuum/

Thanks for the link. Very interesting to read while laying in the ER bed on pain meds. This board is awesome!

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