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AKONI
2012-Feb-29, 12:20 AM
Your thoughts?


http://news.discovery.com/space/asteroid-impact-hazard-2040-120228.html

antoniseb
2012-Feb-29, 12:57 AM
So this thing probably has a mass between 3 and 5 million tons. The article seemed to be calling for nuking it, but I disagree... I don't want the debris. If it goes through the keyhole in 2023, how hard would we have to nudge it to make it miss seventeen years later? We'd have to make it go about 1 cm/sec different speed (at most), which would require an impulse we could deliver using the kinds of rockets we already have.

Van Rijn
2012-Feb-29, 01:26 AM
You might be interested in the discussion in this thread, also the linked Wikipedia article:

http://www.bautforum.com/showthread.php/122626-2011AG5-on-Wikipedia-(NEO-PHA)

My thoughts: Not worried, it's very unlikely that it would hit, there's no doubt it will be kept under close watch, and there would be time to do something about it if conditions changed.

Cougar
2012-Feb-29, 02:08 AM
Your thoughts?
http://news.discovery.com/space/asteroid-impact-hazard-2040-120228.html

There's a good link on that site to "Top 10 Ways to Stop an Asteroid." (http://news.discovery.com/space/top-10-asteroid-deflection.html)

I like the mirrors and the munching robots. No, really!

Swift
2012-Feb-29, 02:36 AM
There's a good link on that site to "Top 10 Ways to Stop an Asteroid." (http://news.discovery.com/space/top-10-asteroid-deflection.html)

I like the mirrors and the munching robots. No, really!
I always liked the paint idea.

WayneFrancis
2012-Feb-29, 05:23 AM
My thoughts is this would be good for NASA.

loglo
2012-Feb-29, 06:07 AM
My thoughts is this would be good for NASA.

They do quite well with a deadline when they have to! :)

Alienathome
2012-Feb-29, 07:15 AM
A pea shooter with good supply of peas should work, too! No?

TimmayB
2012-Feb-29, 08:51 AM
How old will Bruce Willis be in 2040?

Seriously. I wonder if variations in solar wind over 40 years can make or break something like this.

astromark
2012-Feb-29, 09:46 AM
It must be pointed out that UNTIL greater precision of it's known orbital path are known accurately.

It is premature to become 'concerned' we are interested in the orbital path information..

Calm the hype.. learn the facts.. Study the information as we receive it.

Unwarranted speculation and exaggeration are the enemy.. Not rushing about screaming 'doomsday'

The sixth of Feb., 2040. Will be a fine day where I live. It's 28 years away....

Rhaedas
2012-Feb-29, 03:22 PM
I always liked the paint idea.

Me too. If you have enough time and don't need a lot of change, why use a sledgehammer when simple works fine.

That way all you have to worry about is getting there...no despinning, no fracturing or rubble pile problem, no vectors. Just make sure you have enough paint.

antoniseb
2012-Feb-29, 03:29 PM
... Just make sure you have enough paint.

Assuming that we have eleven years to get the package together (for the 2023 key-hole event), it might be easier to wrap it in mylar (or the like) than to actually paint it. Its radius is less than a football field, so it shouldn't be too expensive for the material.

While I like the idea of the robotic factories, I think 2023 is too soon to expect that idea to be feasible. By the end of this century, sure.

Rhaedas
2012-Feb-29, 03:35 PM
Good point. A big problem with painting (which would basically be adding some type of deposit) is the lack of a strong gravity. Not to say it can't be done, but like I said, simpler is better, and wrapping would probably work better. All you have to do is unfurl in the path (neglecting a spin, wonder how that would affect it).

antoniseb
2012-Feb-29, 03:42 PM
... (neglecting a spin, wonder how that would affect it).

If the rock (or heap) is spinning once an hour (fast for an asteroid), and it is 460 feet across, that spin would not be much of an obstacle. I also assume that you'd get the probe into a matching orbit, and use solar wind to unfurl the sheet somehow. ... You could also potentially hammer some stakes into the rotational poles, and attach the sheet as a sail rather than wrap it, but I think wrapping would reduce the risk of applied torques causing the rock to tumble...

Romanus
2012-Mar-01, 12:35 AM
Agree with Astromark: Though I find it interesting from a dynamical and historical perspective, hype like this will--IMHO--only muddy the waters when and if a truly serious threat is found. If that isn't clear now, I'm guessing it certainly will be after another 30 years of "barely missing" the "Big One". A half-orbit arc for a date decades down the road; are people really talking about this now?

Jens
2012-Mar-01, 02:14 AM
That way all you have to worry about is getting there...no despinning, no fracturing or rubble pile problem, no vectors. Just make sure you have enough paint.

As a bonus, we could use it as a way to give jobs to some unemployed abstract painters. Just give them some paint and let them splash it on. And that way nobody is forced to look at their work. Kind of like killing two birds with one stroke of the brush.

Cougar
2012-Mar-01, 02:29 AM
...hype like this will--IMHO--only muddy the waters...

There's bound to be hype, but I don't see any here. I see some thoughtful "what ifs." Speaking of which, I had mentioned the mirrors concentrating sunlight to promote outgassing, thus thrust.... But how far is this thing from the sun? Actually, I think a low-power laser would be as simple, as inexpensive, and easier to control. Or a set of them with different powers on one craft, ready to use whichever works.... I guess this assumes a particular composition of the object that's going to produce outgassing when heated - using material on the object itself as your "jet" fuel.

Also, I stuck a 140 meter wide asteroid (as reported) into an impact calculator and was surprised at the result. That's puny in relation to the Earth, even as a high-speed projectile. Impact energy is only around 50 Megatons. Of course, you don't want to be 10 miles from the impact. A roughly 6.0 seismic event will reach you in about 3 seconds, and then a 170 mph air blast will hit about 45 seconds later. "Wood frame buildings will almost completely collapse... Up to 90 percent of trees blown down," etc. But at 20 miles, hey, might just shatter your windows....

danscope
2012-Mar-01, 05:26 AM
In general, not a game changer.

Jens
2012-Mar-01, 06:02 AM
In general, not a game changer.

In general, no, but I speculate that if it fell onto the pitch during a world cup match say between Brazil and Japan, it would be a game changer because the match would end in a draw rather than a second-place finish for Japan, which would be nearly inevitable otherwise. :)

tony873004
2012-Mar-01, 07:44 PM
Just nuke it!
The biggest complaint here is that instead of getting hit once, we'll get hit by all the fragments, delivering the same amount of kinetic energy. But that's only if we nuke it right before it hits. If we give it the same "decades in advance" treatment that we give to painting it, or to robot munchers, or mirrors, then that will be enough time for the debris to spread out in its orbit. The asteroid doesn't have enough gravity to pull itself back together. Once the fragments have spread out such that their distance is significantly more than 1 Earth diameter, we'll pass harmlessly through the debris field.

Since there's still uncertainty in its orbit, anything we do now, other than nuking it, might actually push it off a near-miss trajectory onto a collision trajectory. Remember, its current nominal trajectory is a near-miss trajectory. We don't want to change that. Nuking it doesn't have that problem. After nuking it, we'll have one bright fireball from the resultant debris every few decades for a few million years on the anniversary of the date it would have hit. Perhaps eventually we will get hit with all the fragments. But it's not the total energy delivered we're concerned about. It's the power: energy / time. Spread the time out over millions of years instead of seconds, and the power falls to safe levels. That's why we choose to take the stairs from the top floor to the ground rather than jump out the window. If we lose our potential energy slowly, it doesn't hurt.

Nuking it also has the advantage of using tested methods and off-the-shelf parts . We've already delivered payloads to asteroids. We've already nuked stuff. We have pleanty of nukes. The 2-km diameter crater formed by the Castle Bravo nuclear test is large enough to hold about 80 asteroids the size of 2011 AG5. Some point out that nukes don't work in space the way they work on Earth, where we have an atmosphere to propogate the shock wave. Fine. Send two nukes. The first vaporizes part of the surface, the second sends a shock wave through the newly-created, short-lived rock-vapor atmosphere. That's the only untested part of if. All the other ideas are completely untested. We've never attempted to paint a significant area of anything in space, or to build giant mirrors in space. And these things need to be done now! We don't have until 2023 to get the package together. We need those eleven years for the delta-V to accumulate enough make it miss the 2023 keyhole (assuming we know exactly where this keyhole is at this point in time. We don't).

Nuking it also gives us the cushion of waiting a few years until we're certain that its on an impact trajectory. There's currently a 624/265 chance that it will miss. The other costly ideas need to be implemented immediately to prevent this 1 in 625 event from happening.

antoniseb
2012-Mar-01, 07:50 PM
Just nuke it!
The biggest complaint here is that instead of getting hit once, we'll get hit by all the fragments,...

No, the biggest complaint isn't what happens to people protected by an atmosphere... Not adding to the loose debris that hazards interplanetary spaceflight is the biggest complaint.

tony873004
2012-Mar-01, 08:35 PM
The loose debris is insignificant compared to what's already out there, and we don't worry much about that, other than making our spacecraft strong enough to impact the microscopic stuff its likely to hit. To date, no interplanetary spacecraft has ever been damaged by a collision with uncharted objects. And the debris would spread out along the orbit of the original asteroid, so its location would not be a great mystery. It would be like a comet shedding debris. It forms a ring around the Sun that creates predictable meteor showers.

ZunarJ5
2012-Mar-03, 03:07 AM
From all the information in this thread alone I'm more worried about Iranian nukes than this. My favorite is the weak gravitational tractor beam idea :)

danscope
2012-Mar-03, 06:45 AM
There may be a question about the delivered power of a "nuke" . Remember: the explosion takes place in a vacuum, not within an atmosphere. You might just make a lot of heat, but no air or steam to expand and deliver a decisive blow to the object.
Any thoughts? And lie was said earlier: It depends too on how well held together it is. If it was just a carbon cinder,
pooof. If it is an iron/nickel meteorite...... who knows? Icy snowball? Better.

swampyankee
2012-Mar-04, 04:45 PM
Paint or gravitational tractor would probably be the best two choices, but they don't have the sheer, mind-numbing stupid factor of using near misses by nuclear weapons.

Chew
2012-Mar-04, 06:14 PM
Paint or gravitational tractor would probably be the best two choices, but they don't have the sheer, mind-numbing stupid factor of using near misses by nuclear weapons.

Why do you say "near miss"? Do you envision someone blindly shooting missiles at it and hoping they get close before it detonates, because, you know, the only way to detonate a nuke is with an alarm clock? Or do you envision a spacecraft rendezvousing with the asteroid and navigating to the optimum position for detonation then awaiting orders from Earth to detonate?

Swift
2012-Mar-04, 07:13 PM
From all the information in this thread alone I'm more worried about Iranian nukes than this. My favorite is the weak gravitational tractor beam idea :)
I note the smilie, but let's also keep politics out of this discussion.

publiusr
2012-Mar-10, 07:50 PM
Something else to consider. A gravity tractor will be a lot like the Rosetta mission, which I think launched when I was in diapers, and will reach its target by the time I'm in the home'

I am exaggerating of course, but bear with me. It will take time to have a matching orbit, and that is before the gravity tractor can even begin its mission, which itself will require some time to take effect.

On the other hand, a nuke-mission can have a much simpler flyby trajectory, much as Deep Impact. Heck, the Orion pusher plate nuclear pulse units aren't all that much different in general shape and size from the Deep Impact copper disk.

Like it or not, nukes allow for quicker missions that reach the asteroid faster when it is farther out, and even allow for smaller LVs in that nukes pack a lot of mass-energy for their size. No "This Old House" painting needed. Be it enamel or latex...

If a single deep impact mission is not enough, then try a salvo
http://www.flightglobal.com/news/articles/nasa-plans-armageddon-spacecraft-to-blast-asteroid-215924/

swampyankee
2012-Mar-10, 08:35 PM
Why do you say "near miss"? Do you envision someone blindly shooting missiles at it and hoping they get close before it detonates, because, you know, the only way to detonate a nuke is with an alarm clock? Or do you envision a spacecraft rendezvousing with the asteroid and navigating to the optimum position for detonation then awaiting orders from Earth to detonate?

No, not an alarm clock. Proximity fuze.

caveman1917
2012-Mar-10, 11:10 PM
Paint or gravitational tractor would probably be the best two choices, but they don't have the sheer, mind-numbing stupid factor of using near misses by nuclear weapons.

And those aren't as cool to watch in slow-motion on tv with Carl Orff's O Fortuna playing in the background :)