Author Topic: Asteroid Collision Mitigation Q&A  (Read 8701 times)

Offline Aza

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Asteroid Collision Mitigation Q&A
« on: 02/03/2011 04:52 AM »
Hi, I didn't see a Q&A for Asteroids...

So this is a big mass of probably solid material over 300m wide that is passing near Earth in 2029 and again in 2036. Could it be directed into near Earth orbit?

It's difficult to get mass into orbit from Earth's gravity well and this is just passing by, twice! Sure I'm not saying it would be easy but would it be feasible and would the pay off if successful be more than the cost? 

Would an object like this in a far earth orbit be useful, say if it was a day away from Earth rather than 5 days like the Moon. Obviously it'd be far to dangerous to put it into a close orbit, better it slowly leaves Earth's orbit than gets closer.

Would it be easier than going to Mars?  And at least there a direct return for the effort and not a big expensive experiment.

« Last Edit: 02/12/2011 04:34 PM by Andy USA »

Offline Downix

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Hi, I didn't see a Q&A for Asteroids...

So this is a big mass of probably solid material over 300m wide that is passing near Earth in 2029 and again in 2036. Could it be directed into near Earth orbit?

It's difficult to get mass into orbit from Earth's gravity well and this is just passing by, twice! Sure I'm not saying it would be easy but would it be feasible and would the pay off if successful be more than the cost? 

Would an object like this in a far earth orbit be useful, say if it was a day away from Earth rather than 5 days like the Moon. Obviously it'd be far to dangerous to put it into a close orbit, better it slowly leaves Earth's orbit than gets closer.

Would it be easier than going to Mars?  And at least there a direct return for the effort and not a big expensive experiment.


In theory, yes.  You'd have to attach some kind of motor on the first pass.  With the period between passes, you have time to use a high-isp, low thrust system to guide the asteroid into a stable orbit.

I'd not be comfortable with it at 1 days trip however.  I'd recommend aiming to put it into orbit around the Moon instead, so worst-case, it still will not cause a catastrophe.
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Offline gospacex

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In theory, yes.  You'd have to attach some kind of motor on the first pass.  With the period between passes, you have time to use a high-isp, low thrust system to guide the asteroid into a stable orbit.

And it would need to be a BIG motor, considering that today's ion engine propelled spacecraft barely manage to accelerate themselves, i.e. something like 1 ton, and Apophis is billions of tons.

If humanity would be willing to spend enough $$$ to do this, I'd vote to spend it on Moon base instead.

Offline aquanaut99

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I don't understand why you would even want to do that.

It is theoretically possible, though it would require a huge investment (much bigger than going back to the moon).

It would also be dangerous (if you screw up, you might end up with Apophis hitting Earth).

And it would probably be a political no-go. If any nation announced it was going to do this, you can expect everyone else to gang up on them (for fear that nation X would then utilise the captured asteroid as a potential doomsday weapon to impose its will on the world). I would forsee the UN stepping in and outlawing the intentional redirection of an asteroid.

Offline MarsInMyLifetime

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You need high impulse right at close passing to capture it into orbit (like Cassini's capture around Saturn). If you start using low-impulse deceleration at the distances needed for the slow-decel scenario, you will effectively move the current orbit of the asteroid away from its near-passing path. After all, this is exactly the scenario for PHA (potentially hazardous asteroids) threat abatement. So if anything, by the time of its next visit, the most likely scenario is that nations might use the close fly by as a chance to use some technology to just nudge it out of the way for all time rather than try to capture it.
« Last Edit: 02/03/2011 03:07 PM by MarsInMyLifetime »
Don

Offline gospacex

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You need high impulse right at close passing to capture it into orbit (like Cassini's capture around Saturn). If you start using low-impulse deceleration at the distances needed for the slow-decel scenario, you will effectively move the current orbit of the asteroid away from its near-passing path. After all, this is exactly the scenario for PHA (potentially hazardous asteroids) threat abatement.

You can change not-quite-close-passing-path to one which comes closer, and in addition to coming at smaller velocity.

Quote
So if anything, by the time of its next visit, the most likely scenario is that nations might use the close fly by as a chance to use some technology to just nudge it out of the way for all time rather than try to capture it.

You can't nudge it "away" at this point of its orbit. Not propulsively (say, with a nuke): it will return to the approximately the same point in space later. Nuking the asteroid to change its orbit away from Earth's orbit necessarily happens far away from Earth orbit.

Deploying solar sail might work.

Offline Danderman

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Imagine the insurance cost for that mission.

Offline Downix

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In theory, yes.  You'd have to attach some kind of motor on the first pass.  With the period between passes, you have time to use a high-isp, low thrust system to guide the asteroid into a stable orbit.

And it would need to be a BIG motor, considering that today's ion engine propelled spacecraft barely manage to accelerate themselves, i.e. something like 1 ton, and Apophis is billions of tons.

If humanity would be willing to spend enough $$$ to do this, I'd vote to spend it on Moon base instead.
Eh, not really.  You just need plenty of fuel.  This is a pass with years to work, and we're not talking about major orbit change.  By my calculations, Apophis could be captured with only a 4.3m/sec delta-v, using the right gravity injection.  It would be easier to use the Moon for the capture orbit too, as I'd be using the moons and earths gravity as part of the system.  By the way I'd do it, the 2036 pass would be such that it would capture Apophis into a highly eccentric orbit initially, then would take 3 more years to get it into the right position.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Aza

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...
Eh, not really.  You just need plenty of fuel.  This is a pass with years to work, and we're not talking about major orbit change.  By my calculations, Apophis could be captured with only a 4.3m/sec delta-v, using the right gravity injection.  It would be easier to use the Moon for the capture orbit too, as I'd be using the moons and earths gravity as part of the system.  By the way I'd do it, the 2036 pass would be such that it would capture Apophis into a highly eccentric orbit initially, then would take 3 more years to get it into the right position.

That's pretty interesting.

I wonder if it could orbit both the Earth and the Moon in a weird  elliptical orbit, so that one end passes near the Earth and the other the Moon. Just jump on and jump off for a free ride to the Moon.

Obviously this is all just sci-fi... but then so was going to the Moon once.  It's good that people in this forum don't discount such ideas out of hand as impossible.


Offline Danderman

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http://www.theonion.com/articles/republicans-vote-to-repeal-obamabacked-bill-that-w,19025/

"In a strong rebuke of President Obama and his domestic agenda, all 242 House Republicans voted Wednesday to repeal the Asteroid Destruction and American Preservation Act, which was signed into law last year to destroy the immense asteroid currently hurtling toward Earth.

The $440 billion legislation, which would send a dozen high-thrust plasma impactor probes to shatter the massive asteroid before it strikes the planet, would affect more than 300 million Americans and is strongly opposed by the GOP.
" :P

Offline kevin-rf

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Sounds like the Onion authors read NSF :D
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Offline Danderman

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Re: Asteroid Collision Mitigation Q&A
« Reply #11 on: 03/07/2011 04:32 PM »
Here is a general asteroid question:

Typically scientists use spectrographs to determine surface composition of a planet or other solar system body, whether the spectrograph is ground-based or on a spacecraft.  However, in the case of asteroids, what typically is the case is that the whole satellite is covered with some sort of regolith that may or may not be consistent with the composition of the satellite itself.

So, how can scientists ever know the real composition of an asteroid? Even a sample return mission would likely return regolith and not actual solid crust.

I understand that the density of an asteroid can be determined from its orbital motion and gravitation effects, but density cannot tell us what a spectroscopic examination can, assuming the object is not covered in dust.

Offline yinzer

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Re: Asteroid Collision Mitigation Q&A
« Reply #12 on: 03/07/2011 05:09 PM »
In one sense, they can't really KNOW unless they get there and dig.

But if you can get close enough a bunch of options might present themselves.  There might be new-ish craters that expose what's beneath the regolith.  You might be able to do gravity mapping to deduce the internal mass distribution, and from there you could take guesses at internal composition.  Different kinds of particle spectroscopy (neutron, gamma ray, etc) might tell you things about what's beneath the surface.

In short - what the Dawn spacecraft is going to try to do at Vesta in a few months, and Ceres later.
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Offline Danderman

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Re: Asteroid Collision Mitigation Q&A
« Reply #13 on: 03/07/2011 05:34 PM »
In one sense, they can't really KNOW unless they get there and dig.

But if you can get close enough a bunch of options might present themselves.  There might be new-ish craters that expose what's beneath the regolith.  You might be able to do gravity mapping to deduce the internal mass distribution, and from there you could take guesses at internal composition.  Different kinds of particle spectroscopy (neutron, gamma ray, etc) might tell you things about what's beneath the surface.

In short - what the Dawn spacecraft is going to try to do at Vesta in a few months, and Ceres later.

The implication is that it is necessary to orbit an asteroid to determine its composition, unless luck intervenes and there are craters that expose the surface.

Offline IsaacKuo

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Re: Asteroid Collision Mitigation Q&A
« Reply #14 on: 03/07/2011 05:35 PM »
So, how can scientists ever know the real composition of an asteroid? Even a sample return mission would likely return regolith and not actual solid crust.

With the exception of a few tiny particles, all of our asteroid samples came to us on their own in the form of meteorites.  These samples give us a good idea of asteroid composition in general, at least the "inside" part that doesn't get worn away during atmospheric entry.  We infer the composition of various asteroids we see in the sky by comparing what we can see with known meteorite samples.

Offline Comga

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Re: Asteroid Collision Mitigation Q&A
« Reply #15 on: 03/07/2011 05:36 PM »
in 2029 and 2036 Apophis will approach the Earth with high relative velocity.  This cannot be eliminated so that the asteroid can go into orbit, even if there was a reason to do it.

If we want to spend a gazillion dollars (adjusted for inflation over a century) to get another moon, there is an asteroid (can't recall it's number) coorbiting the Sun with the Earth.  It will approach slowly in ~90 years before "bouncing off" the Earth's gravity.  (It works, even if you have to think about it for a while.)  Every few hundred years it goes into a pseudo orbit of the Earth, going over the poles.  For a lot less effort than messing with Apophis, but still an enormous effort, its orbit could be modified to make that happen the next time it approaches, around the year 2100.

Why anyone would want this is not clear.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Danderman

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Re: Asteroid Collision Mitigation Q&A
« Reply #16 on: 03/07/2011 05:36 PM »
So, how can scientists ever know the real composition of an asteroid? Even a sample return mission would likely return regolith and not actual solid crust.

With the exception of a few tiny particles, all of our asteroid samples came to us on their own in the form of meteorites.  These samples give us a good idea of asteroid composition in general, at least the "inside" part that doesn't get worn away during atmospheric entry.  We infer the composition of various asteroids we see in the sky by comparing what we can see with known meteorite samples.

But what we can see in the sky is the dusty regolith, not the actual crustal surface.

Offline IsaacKuo

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Re: Asteroid Collision Mitigation Q&A
« Reply #17 on: 03/07/2011 05:57 PM »
We infer the composition of various asteroids we see in the sky by comparing what we can see with known meteorite samples.

But what we can see in the sky is the dusty regolith, not the actual crustal surface.

Since asteroids lack sufficient gravity for differentiation, regolith would be made of much the same stuff as what's underneath (just broken up into smaller pieces due to impacts).  Still, there is much we do not know about asteroid composition and structure.

Offline Danderman

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Re: Asteroid Collision Mitigation Q&A
« Reply #18 on: 03/07/2011 06:41 PM »
We infer the composition of various asteroids we see in the sky by comparing what we can see with known meteorite samples.

But what we can see in the sky is the dusty regolith, not the actual crustal surface.

Since asteroids lack sufficient gravity for differentiation, regolith would be made of much the same stuff as what's underneath (just broken up into smaller pieces due to impacts).  Still, there is much we do not know about asteroid composition and structure.

So, the regolith of a metallic asteroid would be metal dust. Hmmmmm ....

Offline MP99

Re: Asteroid Collision Mitigation Q&A
« Reply #19 on: 03/07/2011 07:40 PM »
Since asteroids lack sufficient gravity for differentiation, regolith would be made of much the same stuff as what's underneath

...less any volatiles that have boiled off?

cheers, Martin

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