MIT developed a simulation to determine the best way to deflect an asteroid

Shawn Knight

Posts: 12,186   +120
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Scientists for decades have theorized how to avoid an impact and now, researchers have gone so far as to lay out a framework to help determine what method of intervention would be best to mitigate a threat.

Their decision method accounts for multiple factors including an asteroid’s mass and momentum, the amount of time scientists would have before an impending collision and its proximity to a gravitational keyhole, among others.

Sung Wook Paek, lead author of a paper appearing in the journal Acta Astronautica this month, said people have mostly considered strategies of last-minute deflection, when an asteroid is heading toward a collision with Earth. “I’m interested in preventing keyhole passage well before Earth impact. It’s like a preemptive strike, with less mess,” the researcher said.

Paek and his team developed a simulation to help determine the best type of defense based on an asteroid’s various properties. The simulation was tested with Apophis and Bennu, asteroids in which researchers already know the locations of their gravitational keyholes, with a variety of variables.

Time seemed to be the major differentiator. For example, with Apophis, if they have at least five years before it will pass through a keyhole, there would be time to send two scouts out – one to measure the asteroid’s dimensions and another to nudge it slightly off track as a test before sending a main impactor to deflect it at a later date. If keyhole passage is set to occur between two and five years out, there may only be time for a single scout. Should the asteroid pass through a keyhole within a year or less, it could be too late to intervene.

Using the simulation tool, Paek and team may be able to set up alternative deflection methods in the future, such as launching projectiles from the Moon or using defunct satellites as kinetic impactors.

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Plutoisaplanet

Posts: 211   +198
I thought I was reading some fictional piece meant for Kingdom Hearts at first... So for everyone who isn't cozy with astrophysics, here's the definition of a gravitational keyhole:

A gravitational keyhole is a tiny region of space where a planet's gravity would alter the orbit of a passing asteroid such that the asteroid would collide with that planet on a given future orbital pass.
 

QuantumPhysics

Posts: 2,644   +2,262
The best defensive strategy for Earth should be to build colonies on the moon and Mars, complete with missile launching platforms.

The biggest problem with Earth is that it takes so much energy just to escape Earth Gravity. Furthermore, Humanity needs to expand to other planetary bodies. No single disaster would be able to wipe us all out.
 
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wiyosaya

Posts: 5,115   +3,208
The best defensive strategy for Earth should be to build colonies on the moon and Mars, complete with missile launching platforms.
The problem with breaking apart a potential impacting asteroid is that the small pieces, if all or most of them impact, can be as devastating and perhaps more so than the asteroid impacting on its own. Plus, for some asteroids, the amount of explosive force needed to break it up might be astronomical - pun intended. :)

This is the reason that the astronomer mentioned in the story prefers an option where the asteroid is detected early enough so that they can, instead of trying to destroy it, nudge it to a different orbit where it would not threaten the Earth at all. Brute force will not necessarily work where a gentle nudge, if employed early enough, is most likely to be successful, in part, due to the lack of undesirable fracturing of the asteroid.

The main problem is that due to the amount of effort currently dedicated to detecting Earth Crossing Asteroids, some are missed, and any one of those that are missed could be "the big one." There have been several instances of "missed Earth Crossing Asteroids" that have made the news in recent years. https://www.businessinsider.com/ast...neocam-nasa-funding-astronaut-support-2018-11

The biggest problem with Earth is that it takes so much energy just to escape Earth Gravity. Furthermore, Humanity needs to expand to other planetary bodies. No single disaster would be able to wipe us all out.
IMO, with our current technology, we have a long way to go before being able to establish self-sustaining colonies within our planetary system.
 
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Actually, most of proposed approaches to planetary defense are neither effective nor scalable even to asteroids capable of country-wide destruction. As of now, it appears that asteroid ablation using highly concentrated sunlight is the only method that meets all of the following criteria: scalability up to global-threat sizes and any type of hazardous bodies as well as low cost and environmental friendliness. This method converts the asteroid to a “natural rocket”, providing more than enough thrust without fuel and energy concerns.

An improved concept for such solar-based deflection using an innovative solar collector was proposed and substantiated in 2013 – see https://link.springer.com/article/10.1007/s11038-012-9410-2
and also a short demo-video

 

GreenNova343

Posts: 428   +313
So...John Ringo was right, & we need to first build VSA (Very Scary Array) mirrors, then upgrade to VDA (Very Dangerous Array) mirrors, then get a SAPL (Solar Array Pumped Laser, aka Serious A** Powerful Laser), then find a big enough nickel-iron asteroid to hollow out & protect the focusing mirror...
 
Unfortunaly, Dr. Lubin's method (in common with Breakthrough Starshot) are rather science fictions at best. It should be clear to the physicist or engineer, because of even a few minutes is enough to damage the emitting zone of a continuously operating powerful laser without active cooling. Actually, I don’t know why the authors of DE-STAR “forget” to mention that there are no materials in nature whose thermal conductivity is sufficient to remove heat from the core of a quasi-continuous kilowatt-class diode laser. Perhaps, that this is a consequence of publication “only for publication” or for obtaining any grants. Even the air convection, which is dozen times more efficient than radiant cooling, will not be enough. But the convection in open space is absent, therefore, such a fundamental limitation exists regardless of the size or type of the passive heat spreader and heat sink. The only way to cool of powerful (over 100 W) quasi-continuously operating lasers is to use the flowing fluid systems (water loops) and open-type refrigerators, which in open space is obviously impossible.

Moreover, the authors of such type approaches, in addition to insurmountable problems with cooling, also “forget” to show the dependence of the laser beam cross-section from the distance to the target. Recall, minimum kilowatt-class diode laser as a separate element of the giant array has the beam's divergence around one angular minute These are key data from which it will become clear that the laser beam will be expanded to values far exceeding the size of the target even at distances near the hundreds of thousands kilometers. So that “the nature is the nature” and laser evaporation of any asteroid, which is enough for its deflection (operational deflection of the sub-km asteroid requires from months to year action of local continuous irradiation at a power density of about several megawatts per square meter of target surface.), isn’t real…
 
Deflecting to where? A minor change in an asteroids orbit at our end could have unforeseen consequences at other points. Deflection, destruction or capture. It there a perfect solution?
 

wiyosaya

Posts: 5,115   +3,208
Unfortunaly, Dr. Lubin's method (in common with Breakthrough Starshot) are rather science fictions at best. It should be clear to the physicist or engineer, because of even a few minutes is enough to damage the emitting zone of a continuously operating powerful laser without active cooling. Actually, I don’t know why the authors of DE-STAR “forget” to mention that there are no materials in nature whose thermal conductivity is sufficient to remove heat from the core of a quasi-continuous kilowatt-class diode laser. Perhaps, that this is a consequence of publication “only for publication” or for obtaining any grants. Even the air convection, which is dozen times more efficient than radiant cooling, will not be enough. But the convection in open space is absent, therefore, such a fundamental limitation exists regardless of the size or type of the passive heat spreader and heat sink. The only way to cool of powerful (over 100 W) quasi-continuously operating lasers is to use the flowing fluid systems (water loops) and open-type refrigerators, which in open space is obviously impossible.

Moreover, the authors of such type approaches, in addition to insurmountable problems with cooling, also “forget” to show the dependence of the laser beam cross-section from the distance to the target. Recall, minimum kilowatt-class diode laser as a separate element of the giant array has the beam's divergence around one angular minute These are key data from which it will become clear that the laser beam will be expanded to values far exceeding the size of the target even at distances near the hundreds of thousands kilometers. So that “the nature is the nature” and laser evaporation of any asteroid, which is enough for its deflection (operational deflection of the sub-km asteroid requires from months to year action of local continuous irradiation at a power density of about several megawatts per square meter of target surface.), isn’t real…
Phase-conjugated fiber lasers are probably the highest power laser devices available at this time. The do not have the same problems as diode lasers do.

If I am not mistaken, this is an example of such.

It would be significantly more challenging to do the same thing, especially phase-conjugation, with a diode laser no matter how powerful due, in part, to their internal construction, and, as you note, having to cool the diode.

These fiber lasers do use diode lasers as a pump on each fiber, however, conjugating the phase of the output from the fiber lasers effectively combines the output from the separate fibers into a single beam that "sums" the output coherently to make it as if it came from one giant laser. Each diode is, of course, cooled; however, since it is not one giant diode, the task is significantly easier.

I could see pumping them with sunlight, too.

The ablation concept is an awesome application of physics, IMO.

EDIT: Phase-conjugation would not be necessary for something like this. A fiber laser alone would likely fit the requirements.
 
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wiyosaya

Posts: 5,115   +3,208
Deflecting to where? A minor change in an asteroids orbit at our end could have unforeseen consequences at other points. Deflection, destruction or capture. It there a perfect solution?
Deflection is where mathematical modeling comes in. If you get it right, it could be delayed for a very long time.
 

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