Asteroid Defense Systems

[p1t1o]

14 hours ago, Spricigo said:

What could possible go wrong? 

Theoricaly (1), we are just taking a weapon of mass destruction (2)that uses radioactive material (3) putting it on top a huge tank of explosives (4) igniting those explosives (5) to deploy our WMD on an asteroid we have little information (6) precisely positioning it (7), so we can detonate our WMD remotely (8) and effectively use the explosive energy (9) to overcome gravitational (10) and structural (11) bonding forces, turning the big asteroid in multiple (12) radioactive (13) smaller asteroids while also ensuring that the whole thing (14) is deflected from its collision course with the Earth. (15). 

Maybe we get in a desperate enough situation to go with that madness anyway. 

1-8 we have done multiple time already, to the point where we are experts at it, ok 5 we have only done once and with a tiny probe, not a WMD but its a start. And 2 and 12 are really insignificant when you consider the mission. The part where we actually detonate in order to deflect, is something we havnt done yet, we'll just have to learn that.

Nobody said it would be easy or risk-free. You can take apart any strategy into points like that.

Compared to the risks of letting a significant impactor hit the Earth? There's no question.

And if we get desperate-desperate then nukes really are are only option.

 

On 10/6/2017 at 7:22 PM, magnemoe said:

Shoemaker levy gave us an 2 year warning and it was in Jupiter orbit, impact speed was 60km/s with 21 kilometer sized bodies. 

Well in this case nukes really are our only option, at least they are made of ice and not rock. Worst comes to the worst we throw up every nuke we can manufacture until its just gas.

Very VERY rough calculation shows that to convert a 50km diameter sphere of water ice (65billion tons worth) at 3K to steam at 373K would require 55,645 megatons.

Naturally its not that simple, only a fraction of each devices energy would be absorbed by the comet, plus re-radiation, break up, outgassing etc. But on the other hand, total vaporisation would not be required, not by a long chalk, it would be way off course way before it was all gas.

But 55thousand megatons is not 55billion or trillion, its within the realm of plausibility. If measured against the survival of the human race.

I think the maximum possible yield-to-weight practically achievable is around 5-6kiltons yield per kg of bomb, which if we take it at 5 means 55.5k megatons is equivalent to 11,100tons of devices.

Scary numbers but not impossible numbers. Yes I know that total vaporisation is a terrible idea, this worked example is illustrative of general magnitude only. If it was a rock asteroid instead, you can expect these numbers to be at least 1000x larger I think.

The biggest difficulty in this scenario, I think, would be getting it all organised in the time window permitted, no mean feat.

Edited October 7, 2017 by p1t1o

[magnemoe]

4 hours ago, PakledHostage said:

Something to bear in mind for a realistic ELE type impact scenario is that we may not have any option other than to detonate nukes as the object whizzes by at ludicrous speed.

All the near earth objects over 1 km in diameter have been identified via the WISE probe's whole sky survey (within a reasonable degree of confidence) and none of them other than maybe 1950DA are on a collision course with us. The dinosaur killer has been estimated to have been on the order of 10 km in diameter, so we can be quite confident that we won't get blind sided by something like that. 

What we have to worry about, on the other hand is something like comet C/2013 A1 Siding Spring that passed close to Mars in 2014. It was only about 18 months from when it was discovered until it passed Mars, and initial computations of its orbit suggested that it might hit. Worse yet, it was on a retrtograde trajectory and would hit at ~60 km/sec. It wouldn't have to be very big to do a lot of damage at that speed. And we don't have any rockets with enough delta-V to reach and land anything on something like that enough in advance. All we could do is send nukes on flyby trajectories and detonate them at closest approach in the hopes that they deflect it enough (via the ablation method mentioned above) to miss us.

This, 1950DA is not something you nuke, you, launch an mass driver, this is an coil gun like the catapult on the last aircraft carrier but focus of getting say 25 kg up to solar escape speed. bucket with magnets is then braked and returned, you use gravel from the asteroid as reaction mass. Main purpose is not redirect but mining. 
Mass driver who can redirect an 1 km asteroid with the power source will be heavy as in IIS, might work with BFR, at least then using the refuel in high orbit idea, installing it on asteroid is likely to be an manned mission because of complexity. Again pretty doable if spacex predictions holds true but adding the falcon heavy time delay factor, add 10 years for the redirect and capture operation, name it Minmus

An comet with an 1 year warning, well the above plan has some downsides as in not being able to mach velocity before impact. This make it as useful as pulling out your phone and order an life jacket from Amazon if you fell into water and can not get back on shore. note that If your phone is water proof or not is irrelevant. 
 

[p1t1o]

2 minutes ago, magnemoe said:

An comet with an 1 year warning, well the above plan has some downsides as in not being able to mach velocity before impact. This make it as useful as pulling out your phone and order an life jacket from Amazon if you fell into water and can not get back on shore. note that If your phone is water proof or not is irrelevant.

I dunno, we are getting closer to this. Doesnt Amazon offer same-day delivery by drone to some limited areas nowadays?

Give it 50 years and this might be the normal way to get lifejackets XD

 

[magnemoe]

2 minutes ago, p1t1o said:

I dunno, we are getting closer to this. Doesnt Amazon offer same-day delivery by drone to some limited areas nowadays?

Give it 50 years and this might be the normal way to get lifejackets XD

 

On work we discussed using drone to deliver kids to kinder-garden, an trampoline would let you do air drops. The kids would love it
I always promote my 2 or 0 g elevator idea, elevator accelerate at 2 g the first half of trip then go ballistic, going down it fall free for the first half. 
This would be insane fun and save time, a bit downside if you carry an tray of coffee cups. 
Both ideas is way more safe than buying an life jacket after falling in water, I might add parachutes and bullet proof vests to the list. 
Now how do you combine an bullet proof vest and an life jacket? Note that this is an real issue for coast guards and its solved pretty well. 
 

[p1t1o]

A little OT:

Spoiler

39 minutes ago, magnemoe said:

On work we discussed using drone to deliver kids to kinder-garden, an trampoline would let you do air drops. The kids would love it
I always promote my 2 or 0 g elevator idea, elevator accelerate at 2 g the first half of trip then go ballistic, going down it fall free for the first half. 
This would be insane fun and save time, a bit downside if you carry an tray of coffee cups. 
Both ideas is way more safe than buying an life jacket after falling in water, I might add parachutes and bullet proof vests to the list. 
Now how do you combine an bullet proof vest and an life jacket? Note that this is an real issue for coast guards and its solved pretty well. 
 

In various sci-fi novels they seed the environment with numerous supersonic drones, in one example IIRC, capable of making rockclimbing totally risk-free.

I think I remember seeing something on TV about those bulletproof lifejackets, it resembled a kevlar vest that split open to allow it to inflate on contact with water, or something?

On topic thought:

Say we detect and successfully neutralise a dinosaur-killer.

Can we now safely disregard the possibility of another one? Given that statistically it would be several million years before we encounter another?

 

You can ask a variant of that question about impactors all the way down to multi-millenia periods. But the premise is the same. As a species, what level of risk are we prepared to ignore? We all know, that hydrogen bombs do not cause the atmosphere to self-destruct. But someone once asked the question, and the authorities came back with (I saw some document or other) something like "Is the chance less than 2%?". No scientist thought it was ever a possibility, but the person giving permission was not so certain.

Its a hard question. Clearly we are perceiving the risk more and more, to be one that cannot be ignored, but it cannot be denied that these thing do not rain out of the sky - if we kill a big one, what happens to the risk?

Edited October 7, 2017 by p1t1o

[PakledHostage]

5 hours ago, Spricigo said:

Which don't  make it a reliable options.  

That was implicit in my last post. But that doesn't mean that, in the absence of any other options beyond digging underground bunkers, (hey, it worked for our mammal ancestors 60 odd million years ago), we wouldn't at least try it.

Edited October 7, 2017 by PakledHostage

[PakledHostage]

 

4 hours ago, magnemoe said:

This, 1950DA is not something you nuke, you, launch an mass driver, this is an coil gun like the catapult on the last aircraft carrier but focus of getting say 25 kg up to solar escape speed. bucket with magnets is then braked and returned, you use gravel from the asteroid as reaction mass. Main purpose is not redirect but mining. 
 

Exactly. Because the thing won't hit (if it hits at all) until ~860 years from now. We've got lots of time. Heck, a significant factor in whether it even hits is the Yarkovsky effect. Simply taking the Rolling Stones' advice and painting it black might even be enough to deflect it.

Edited October 7, 2017 by PakledHostage

[Spricigo]

3 hours ago, p1t1o said:

Nobody said it would be easy or risk-free.

Nobody said. Nonetheless the risks were downplayed and the probability of sucess exaggerated. 

In particular 'blowing up' the asteroid is very unlike to do any good. We may call a sucess if we end with a radioactive pile of rumble  instead of a rock?

 

3 hours ago, p1t1o said:

And if we get desperate-desperate then nukes really are are only option

No, theorical solution like anyything else   We have no tools and no techniques.

2 hours ago, p1t1o said:

Say we detect and successfully neutralise a dinosaur-killer.

Can we now safely disregard the possibility of another one? Given that statistically it would be several million years before we encounter another?

Statistics don't work like that. The asteroid we deflected* will not change when the next one will appear. 

In any case the value of the question remains.  

I'd say we seems to have more urgent matters to deal with. And since we don't have unlimited resources. ..OTOH we can't just disregard a know risk until it becomes uncontested reality. 

23 minutes ago, PakledHostage said:

That was implicit in my last post. But that doesn't mean that, in the absence of any other options beyond digging underground bunkers, (hey, it worked for our mammal ancestors 60 odd million years ago), we wouldn't at least try it.

Instinctive answer: send everything we have.

Ractional answer: lets come with a better plan because otherwise we are doomed. 

 

*I can't seriously consider the idea of vaporizing an asteroid. 

[PakledHostage]

15 minutes ago, Spricigo said:

*I can't seriously consider the idea of vaporizing an asteroid. 

I don't think anyone is talking about vaporizing whole asteroids... at least I am not. What we are talking about is using the energy of a nuclear explosion to ablate the surface of the asteroid/comet with the conequece of imparting an equal and opposite momentum to it. The idea is that the "push" is sufficient to cause it to miss.

The advantage of this method is you don't need to land anything on the impactor. You just detonate the warehead in proximity. It may not work or it may not work enough, but with today's technology, it may be the only arrow that we have in our quiver if we suddenly discover an inbound oort cloud comet that's going to hit us in 18 months.

Edited October 7, 2017 by PakledHostage

[p1t1o]

1 hour ago, Spricigo said:

Nobody said. Nonetheless the risks were downplayed and the probability of sucess exaggerated. 

In particular 'blowing up' the asteroid is very unlike to do any good. We may call a sucess if we end with a radioactive pile of rumble  instead of a rock?

Yeah, in most cases I'd call that a huge success. But again, blowing into pieces is not often the aim. Forget about radioactivity, the danger to life compared to the rock is negligible.

1 hour ago, Spricigo said:

No, theorical solution like anyything else   We have no tools and no techniques.

Too bad, everything guaranteed to be "theoretical" until we actually do it.

1 hour ago, Spricigo said:

*I can't seriously consider the idea of vaporizing an asteroid. 

No of course not - as stated, the example was to illustrate the magnitude of the problem only, plus the example was for a comet which would be several orders of magnitude easier to "vaporise" than an asteroid.

****

I should say, that most of the time I am assuming a much better ability to detect impactors than we have today. Since we do not have a working practical solution in service, I reasonably assume that by the time we do, detection facilities would have undergone an expansion of a similar magnitude.

Edited October 8, 2017 by p1t1o

[Spricigo]

3 hours ago, PakledHostage said:

What we are talking about is using the energy of a nuclear explosion to ablate the surface of the asteroid/comet

And I'm pointing that it have serious risks associated.  Forced to choose between this and extinction we will take any risk, no matter how big.  

But while we still have time better to find alternatives or, at least, create ways to reduce the risks in this one.

2 hours ago, p1t1o said:

3 hours ago, Spricigo said:

We may call a sucess if we end with a radioactive pile of rumble  instead of a rock?

Yeah, in most cases I'd call that a huge success actually

So you prefer to get hit and poisoned instead of only hit? Because that's the difference.  

2 hours ago, p1t1o said:

Forget about radioactivity, the danger to life compared to the rock is negligible.

I'll continue to consider the potential radiological accident in global scale. My reasoning: if it can cause a mass extinction by Itself is not negligible. 

2 hours ago, p1t1o said:

Too bad, everything guaranteed to be "theoretical" until we actually do it.

The point remains: there is nuclear weapons and spaceflight, but no nuclear weapons flying in space. Granted there are political reasons,  but technical reasons also exist.

 

[PakledHostage]

13 hours ago, Spricigo said:

The point remains: there is nuclear weapons and spaceflight, but no nuclear weapons flying in space. Granted there are political reasons,  but technical reasons also exist.

 

But nuclear weapons have been detonated at an altitude of 400 km: 

https://en.m.wikipedia.org/wiki/Starfish_Prime.

That's "space" enough for the ISS.

Edited October 8, 2017 by PakledHostage

[Spricigo]

8 hours ago, PakledHostage said:

But nuclear weapons have been detonated at an altitude of 400 km: 

https://en.m.wikipedia.org/wiki/Starfish_Prime.

That's "space" enough for the ISS.

And screw with stuff on Earth without affecting any asteroid.

Nuking a asteroid is no more real than landing a mass drive or using a gravity tug to change  its trajectory.

 

[PakledHostage]

3 hours ago, Spricigo said:

And screw with stuff on Earth without affecting any asteroid.

Nuking a asteroid is no more real than landing a mass drive or using a gravity tug to change  its trajectory.

 

Why? So far your argument has amounted to "because [technical] reasons" but "because reasons" as an argument doesn't even pass muster with my three year old. 

You do realize that we are talking about detonating a warhead at a distance of tens of millions or even hundreds of millions of kilometers from earth?

Edited October 9, 2017 by PakledHostage

[Spricigo]

2 hours ago, PakledHostage said:

Why? So far your argument has amounted to

Why would be my burden to disprove the viability of your proposal? 

YOU made the claim that redirecting an asteroid with nuclear weapons is viable. Where are YOUR evidences? 

So far I can only agree with this:

On 07/10/2017 at 8:02 PM, PakledHostage said:

It may not work or it may not work enough

How that goes with your 3yo?