Death Roids: What's the minimum time to do anything?

[Lagmonster]

I was thinking about all of the ways - most silly, some not - that we think we could avert a collision with an incoming asteroid.

So what I want to know is, what is the minimum amount of warning we would need to do *anything*. How much time would a major nation need to say, "Holy shit, we have to launch SOMETHING right now and it has to go HERE".

I suppose it's a long-winded way of asking how quick we could target and launch *anything* related to the average size, speed, and distances we'd be talking about with a worrisome incoming rock. This is not really about the time needed to build a competent response or the method we'd use - this is more about the time needed to do even the most half-assed 'probably won't work but fuck it, send the nuke' zero-hour plan.

[Sea Skimmer]

It’d depend on the impact zone and size of the asteroid as to if it would do any good, but we should have some limited capability to nuke an incoming rock using a stock ICBM if the impact was to be in the northern hemisphere. However this would be dependent on some fusing features existing on the ICBM which may or may not currently be in service. Mainly a fuse capable of very high altitude operation. Such fusing was a big deal to have back in the 1960s, its not clear if one exists now because pin down tactics (creating a barrage of radiation to destroy enemy ICBMs in flight) are less viable then they used to be. If such a fuse exists then an hour warning time should suffice to target and fire the ICBM, or more likely a salvo pattern of them. Course doing this would almost certainly lead to large scale EMP which is going to be really annoying.

ABM missiles should also be quite well able to hit an incoming asteroid and at least break it up some, but that might make damage worse in some cases. Much would depend on the composition of the asteroid. Nickel iron ones will be far harder to damage then rocky ones. The US GBI system would be able to cover all of North America, and some other regional defense zone exist but most of the worlds surface would be wide open to attack. Given warning time measured in days or weeks then SSBNs and ABM armed warships could move to cover most of the earth.

Any kind of space launch option is going to need weeks of warning.

[Skgoa]

Erm, we want to save lives and not produce shrapnel that trashes most of a hemisphere.


We have pretty good ion drives nowadays. With enough time - years if we have to construct build it from scratch, several weeks if we keep such a vessel in reserve at all times - we could launch it, get it on a transfer orbit to whatever we want to move and just let it collide at the appropriate angle and keep it runing for as long as we need to.
We would probably have to take this craft up in parts and assemble it in orbit, but we have been doing that for 40 years, now. That would also reduce the size requirements for the launch vehicle. If we build the parts in the weight range of medium satellites, there will be several suitable rockets either on hand or very near finished at all times.
Note: in the first episode of Phil Plait's Bad Universe (great guy and great show BTW) they proposed useing gravity as a tether. That works even better, but the amount of force that can be applied on the asteroid is limited by this, resulting in much slower effects.
edit: The big problem with that would be the rotation of the target. Thats why the gravity idea is better, if we have the time. Maybe if we launch several such asteroid engines an fire them when appropriate...

[Serafina]

Given the distances involved, isn't the best solution to nudge it slightly so that it will just miss earth?
As it has been said, ion drives might work - but could we do that with explosions as well?

[nobody_really]

Phil Plait just covered this on his new show Bad Universe on Discovery Channel on Sun. Aug. 29. He was trying to get a Mythbusters take by using analogs of various asteroids and firing various projectiles at them. And he really seems to hate Sydney, as the graphics had it getting blown up multiple times.

If it is a killer asteroid (a few hundred meters to a few miles across), a single nuke isn't going to have much effect, except to possibly make a couple or few somewhat smaller asteroids that will wipe out a couple of locations on Earth, instead of completely vaporize one area. The takeaway that I got was that the best way is to have enough time to use gravitational towing with an ion-engine powered craft to deflect it, although there wasn't much time spent discussing that solution.

If the asteroid is small enough, and the explosion or kinetic collision big enough, and if there's enough distance, it also looked like nudging would be a viable solution. The iron asteroids are pretty tough, though, and a kinetic collision or explosion wouldn't have much effect. If one were to come in from the direction of the Sun, we're basically boned because of the lack of warning.

Also, if a sizable asteroid were to land in one of the oceans, it would probably destroy even more cities because of the massive tsunamis involved and the fact that so many of our big cities are on a coast.

[Sea Skimmer]

Erm, we want to save lives and not produce shrapnel that trashes most of a hemisphere.

Yes, look someone making another groundless assumption that nuking a rock guarantees shrapnel that will be more damaging then the giant solid object hitting. Sorry but no, even for rocks many hundreds of meters across that need not be true. In the first place most debris will be small enough to burn up. In the ICBM scenario the warhead goes off in near space, leaving the entire passage through the atmosphere for debris destruction. Whats more a follow nuke can vaporize many of those much smaller pieces in turn or smash them smaller. Hit to kill ABM can target the larger fragments as well as a lower layer of defense, for those areas so protected. Currently the world has ICBMs estimated to have at least as large as 5 megaton warheads, you can destroy some pretty large masses with that. The larger the threat, the more likely it is to be detected, and the rarer, so its really stuff below about 1km diameter we should be worried about that. Nuclear weapons can counter a threat of that scale.

We have pretty good ion drives nowadays. With enough time - years if we have to construct build it from scratch, several weeks if we keep such a vessel in reserve at all times - we could launch it, get it on a transfer orbit to whatever we want to move and just let it collide at the appropriate angle and keep it runing for as long as we need to.

Wow way to just totally miss the entire point of the thread. *Minimal Time* That was the question. Not what would work with years of warning, which we will not reliably have. In fact budgets for looking for that kind of thing have been seriously cut back in recent years. Its rather obvious that we can do a billion different things given years to plan, construct and test it. We've had plenty of threads on that before. But minimal reaction time is a much different subject.

[adam_grif]

I've been pondering Orion style nuclear shaped charges... blasting away at the surface of the asteroid. Simultaneously ablates the surface and steers it away.

NOT a "Oh no six hours to impact" thing of course. Since we don't have any of these weapons on standby in orbit...

[Sea Skimmer]

You might be able to build a crude but usefully improved nuclear shaped charge out of an existing warhead in a matter of weeks. At the most basic level you just need directional radiation reflectors.

But I don’t think anyone would want to try, because the weight distribution would be different and thus you now have all sorts of integration problems with the missile reentry vehicle and missile guidance system. What’s more the radiation reflections will play hell with the physics of the chain reactions, so it may fissile without additional modifications. Also it seems the neutron bomb is the best type of nuke for making one of those shaped charges, and no one ever put neutron bombs on ICBMs. Doesn’t make any real sense to do so.

Better to fire a stock warhead since if we use an ICBM, we’d really only have one short engagement window (assuming the fusing exists). This is not a good time to find out the first salvo ended up 2000 miles off course.

Once you start getting into months, it should be possible to hijack an existing space launch vehicle which is less sensitive to payload variations, and which can engage at a much high altitude, though we would still be relying almost purely on prediction to make an intercept. We would also have enough time to do some hasty atmospheric test shots. Course in reality the political resolve to do aggressive testing like that is rather unlikely. Especially since a 100-1000 meter rock isn’t a planet killer.

[Simon_Jester]

Once you start getting into months, it should be possible to hijack an existing space launch vehicle which is less sensitive to payload variations, and which can engage at a much high altitude, though we would still be relying almost purely on prediction to make an intercept. We would also have enough time to do some hasty atmospheric test shots. Course in reality the political resolve to do aggressive testing like that is rather unlikely. Especially since a 100-1000 meter rock isn’t a planet killer.

A rock that size would be a threat in terms of "level a major metropolitan area." If it was predicted to land on (or in the seas off of) a nuclear power, that power would probably do any necessary tests without more than the vaguest acknowledgement that yes, once upon a time it signed some test ban treaties. And who would blame them?

If it didn't affect any nuclear power, you'd still see the prospective victims screaming for any necessary work to mount a deflection mission.

If the course could not be predicted accurately, then everyone will be wanting to do the necessary tests to do a deflection mission, or screaming for others to do it for them.

[Sea Skimmer]

If the course could not be predicted accurately, then everyone will be wanting to do the necessary tests to do a deflection mission, or screaming for others to do it for them.

That's the trouble I see. Really accurate prediction could be very hard until we reach a very close range, though we could still be talking 100,000 miles as 'close'. The smaller the rock the more it will be affected by little things like passing satellites as it comes in. If it was clearly going to land right on NYC, the margin of error only meaning a impact on the outskirts then yeah sure, the limited test ban treaty is likely out of the window. We won't have time to drill boreholes for underground tests most likely. But what if its going to come down in an area of with 5,000 person towns spaced every couple miles, or an unpopulated area of ocean which is none the less one of the richest fishing grounds on earth and vital to the local economy in a non strategic manner? Cities just aren't that likely to be the impact point, and yet damage could easily be heavy in other areas from the general disruption and longer term extended winter effects from all the dust in the air. But stuff like that is harder to convey to the public, and the public and a great many of its representatives are a bunch of screaming hysterics.

Just think about how many billions of people are going to believe the rock was actually a conspiracy by the US government, and that the Apollo program sent out an unmanned (because manned spaceflight is impossible the radiation will kill them all OMFG!!!!) probe to bump it onto a collision course so that the US could back out of the limited test ban treaty we signed just a few years earlier 50 years in the future…. Even if the rock was in fact nuked by the Chinese it'd still be claimed to be one giant US led New World Order UN illegal toilet hoarding cow raping act of pure evil.

[Skgoa]

Erm, we want to save lives and not produce shrapnel that trashes most of a hemisphere.

Yes, look someone making another groundless assumption that nuking a rock guarantees shrapnel that will be more damaging then the giant solid object hitting. Sorry but no, even for rocks many hundreds of meters across that need not be true. In the first place most debris will be small enough to burn up. In the ICBM scenario the warhead goes off in near space, leaving the entire passage through the atmosphere for debris destruction. Whats more a follow nuke can vaporize many of those much smaller pieces in turn or smash them smaller. Hit to kill ABM can target the larger fragments as well as a lower layer of defense, for those areas so protected. Currently the world has ICBMs estimated to have at least as large as 5 megaton warheads, you can destroy some pretty large masses with that. The larger the threat, the more likely it is to be detected, and the rarer, so its really stuff below about 1km diameter we should be worried about that. Nuclear weapons can counter a threat of that scale.

I wasn't all that serious, hence the smiley.

We have pretty good ion drives nowadays. With enough time - years if we have to construct build it from scratch, several weeks if we keep such a vessel in reserve at all times - we could launch it, get it on a transfer orbit to whatever we want to move and just let it collide at the appropriate angle and keep it runing for as long as we need to.

Wow way to just totally miss the entire point of the thread. *Minimal Time* That was the question. Not what would work with years of warning, which we will not reliably have. In fact budgets for looking for that kind of thing have been seriously cut back in recent years. Its rather obvious that we can do a billion different things given years to plan, construct and test it. We've had plenty of threads on that before. But minimal reaction time is a much different subject.

Yes, the ICBM/ABM option wins the thread by being the one with the "shortest time before impact".

I've been pondering Orion style nuclear shaped charges... blasting away at the surface of the asteroid. Simultaneously ablates the surface and steers it away.

Anything that contains the word "Orion" and is not about greek mythology or constelations is extremely stupid and/or silly anyways.

[Simon_Jester]

That's the trouble I see. Really accurate prediction could be very hard until we reach a very close range, though we could still be talking 100,000 miles as 'close'. The smaller the rock the more it will be affected by little things like passing satellites as it comes in. If it was clearly going to land right on NYC, the margin of error only meaning a impact on the outskirts then yeah sure, the limited test ban treaty is likely out of the window. We won't have time to drill boreholes for underground tests most likely. But what if its going to come down in an area of with 5,000 person towns spaced every couple miles, or an unpopulated area of ocean which is none the less one of the richest fishing grounds on earth and vital to the local economy in a non strategic manner?

Tidal waves, remember?

More generally, prediction of impact points is going to have a large enough margin of error that you can't know it won't hit a city, and a big one will have enough of a footprint that it will probably manage to wreck a city or two by default unless (like, say, the Tunguska blast) it lands in Siberia or the Canadian Shield or some such.

Under the circumstances, I think the relevant world governments- not the screeching ones whose foreign policy mostly consists of flipping off the rest of the universe as a gesture for the benefit of their own public, I mean the ones that are mature enough that they feel some vague obligation to make sense- will let it pass as long as the atmospheric tests aren't done gratuitously or at a level much greater than can be justified by the need to address the threat.

Cities just aren't that likely to be the impact point, and yet damage could easily be heavy in other areas from the general disruption and longer term extended winter effects from all the dust in the air. But stuff like that is harder to convey to the public, and the public and a great many of its representatives are a bunch of screaming hysterics.

At what? I mean, Americans aren't nuke-happy, but I don't think opposition to nuclear technology is that fanatical, not among a large enough sector to matter. If a rock big enough to fry an area the size of South Carolina is projected to hit somewhere in North America, I doubt anyone would complain about the testing needed to make sure a deflection mission succeeded. Ditto for any of the other major nuclear powers.

Just think about how many billions of people are going to believe the rock was actually a conspiracy by the US government, and that the Apollo program sent out an unmanned (because manned spaceflight is impossible the radiation will kill them all OMFG!!!!) probe to bump it onto a collision course so that the US could back out of the limited test ban treaty we signed just a few years earlier 50 years in the future…. Even if the rock was in fact nuked by the Chinese it'd still be claimed to be one giant US led New World Order UN illegal toilet hoarding cow raping act of pure evil.

Skimmer, I think you're missing a critical point: who cares? There are still people who believe Pearl Harbor was an inside job (somehow!), but they don't have a real long term effect on the world.

Ultimately, conspiracy theories have very little power, because the likelihood that you will be one scales inversely with the amount of actual knowledge you have about how the system works.

There may be a bunch of people who believe that the whole thing was (for some reason) an elaborate fake, but world governments with their own astronomers who could do the math will not be among them. It might be annoying because you'll be having to put up with a new breed of conspiracy theorists, but compared to getting hit by a high-megaton or low gigaton range rock, it's just not a meaningful problem.

[Sarevok]

I am unsure about using existing ICBMs against incoming meteors.

They are programmed to fly in a ballistic toward another point on Earth. They don't have SAM like guidance system to home into another flying object. A mathematician could calculate an intercept solution to hit the rock with a missile. But actually putting into an accurate flight path would be a problem. The missile may have required speed and altitude to reach a meteor. But it does not have a seeker or command link. Without active course correction accuracy would be spotty at best.

[J Ryan]

I am unsure about using existing ICBMs against incoming meteors.

They are programmed to fly in a ballistic toward another point on Earth. They don't have SAM like guidance system to home into another flying object. A mathematician could calculate an intercept solution to hit the rock with a missile. But actually putting into an accurate flight path would be a problem. The missile may have required speed and altitude to reach a meteor. But it does not have a seeker or command link. Without active course correction accuracy would be spotty at best.

Active course correction is hardly going to be required as asteroids don't attempt to dodge. If you have something that can achieve the speed and altitude that's all you need. After all Voyager II was able to visit the 4 gas giants over a journey of 12 years and all it took was it's initial launch out of Earth orbit thrust wise. Mathematicians is all you need in space.

[Sarevok]

Actually Voyager 2 had sophisticated navigation equipment like a star tracker and a sun sensor. It was not simply shot like a cannonball on a ballistic path. Most spacecraft do make course corrections en route as they close in on a planet. They have the benefit of ground control actively monitoring position of the spacecraft and recommending course changes which a ICBM does not. An ICBM is flying blind on a preset flight plant. Furthermore ICBMs are not known for smartbomb levels of accuracy. For most ICBMs CEP is large enough that they have difficulty landing within 100 meters of a target site. Against a space borne target it was not designed for ? I have doubts if a pre calculated flight path will produce a successful impact.

[Patrick Degan]

I also have serious doubts about the adaptability of an ICBM for the purpose of a space interception. These things are designed and built to follow a suborbital trajectory. If you took a standard booster and fitted it with guidance instrumentation and ground-control, such as was done with the earliest space launchers, you could get a nuke into orbit. But a missile straight out of the silo? It would take far too long for the timeframe you have available, if you're down to attempting an intercept before the asteroid is about to enter its terminal flightpath, to modify it for such a mission.

The better bet might be to have a few Delta or Centaur space launchers held in reserve, each fitted with a nuclear charge and kept on standby.

[Sarevok]

Funnily the producer of the widely used Dnepr launch vehicle offers to sale anti asteroid defense systems on their website. No price or technical details are offered. I wonder if its some Ukrainian engineers idea of an april fools joke ?

linky

[Alyrium Denryle]

For the people suggesting nukes: It Wont Work.

Lets say we have an asteroid the size of Apophis. It is the size of the rose bowl. In order to fragment it will require a buried explosive of 93 kilotons to crater it. Fragmenting it into chunks that wont get through the atmosphere requires a buried explosive of 19.7 kt if it is hard granite, which IIRC it is not. This asteroid if nuked will just break up into large pieces and shower parts of itself over the planet in a completely unpredictable path.

You may be able to do something if you see the asteroid a few days or weeks out. That something however for even a (relatively) small killer asteroid may or may not be effective. Realistically (no nerdy nuke-wanking), you need much greater lead time, which means you need to detect the asteroid years or better yet decades in advance. particularly for bigger asteroids. For something the size of the one that caused the KT event, you will need multi-gigaton buried charges just to crater the fucking thing.

The best option is a gravity tug, but you need significant lead time.

[Sarevok]

I am not so sure about Apophis sized objects. They are small enough to be destroyed by a nuclear weapon. If one warhead is not sufficient we can use more. There many nuclear weapons in the 50-500 kiloton range available. The real trick is getting a way to send them to the asteroid on short notice. Since there is not always a rocket available on a launch pad somewhere in the world we are fucked if the asteroid shows up at a wrong moment.

[Alyrium Denryle]

I am not so sure about Apophis sized objects. They are small enough to be destroyed by a nuclear weapon. If one warhead is not sufficient we can use more. There many nuclear weapons in the 50-500 kiloton range available. The real trick is getting a way to send them to the asteroid on short notice. Since there is not always a rocket available on a launch pad somewhere in the world we are fucked if the asteroid shows up at a wrong moment.

Unless you can bury the nuke, you will need a lot more than that. A firecracker set off on your open hand will cause some burning, a firecracker set off in your closed hand will cause you to need hospitalization and possibly the amputation of your hand.

[adam_grif]

For the people suggesting nukes: It Wont Work.

If you're imagining that we are just trying to vaporize it, maybe. A detonation on or near the surface will vaporize surface material and cause a change in momentum; depending on time, size and power, this is enough to alter it's trajectory. You might need 1 nuke or you might need 100.

The reason I proposed nuclear shaped charges is because it packs tremendous energy in a small package, but also dumps most of the energy into what may as well be a DEW. ~85% of the energy will be delivered instead of <50% for an ordinary surface burst, and it will impart changes in momentum far faster than a gravity tug or something will be able to. Which is key with minimum warning time.

[Alyrium Denryle]

For the people suggesting nukes: It Wont Work.

If you're imagining that we are just trying to vaporize it, maybe. A detonation on or near the surface will vaporize surface material and cause a change in momentum; depending on time, size and power, this is enough to alter it's trajectory. You might need 1 nuke or you might need 100.

The reason I proposed nuclear shaped charges is because it packs tremendous energy in a small package, but also dumps most of the energy into what may as well be a DEW. ~85% of the energy will be delivered instead of <50% for an ordinary surface burst, and it will impart changes in momentum far faster than a gravity tug or something will be able to. Which is key with minimum warning time.

Depending on the time, size and trajectory, that wont be enough. You end up with the same problem, except the energy required to change the asteroid's trajectory enough that it wont hit needs to be applied instantaneously, and in a stochastic manner. Surface features of the asteroid will change how its trajectory changes as a result of the vaporization. You dont have that problem with a grav tether.

[Sarevok]

The US military is rumored to be working ways to destroy buried installations with ground penetrating nukes. Perhaps the technology can be adapted for use against small asteroids to efficiently destroy them from within rather than a wasteful surface detonation.

[Seggybop]

Funnily the producer of the widely used Dnepr launch vehicle offers to sale anti asteroid defense systems on their website. No price or technical details are offered. I wonder if its some Ukrainian engineers idea of an april fools joke ?

linky

The specific feature of the proposed anti-asteroid modules is in that they do not utilize the components of an atomic fuse applied in hydrogen bombs, and, therefore, no radioactive elements are present in the products of explosion. In the proposed system, initiation of the explosion reaction of hydrogen synthesis is provided at a meeting point of cumulative jets that are formed during collision with an asteroid at relative velocity of about 100 km/s.

Eh, are these guys suggesting that they can effect a pure nuclear fusion explosion by crashing their pod into the asteroid at high velocity...?

[Sky Captain]

100 km/s impact velocity is far too high for NEO's. Most NEO's have relative velocity of 15 - 20 km/s. A cemical rocket could provide only few additional km/s to a spacecraft targeted at incoming asteorid so that 100 km/s figure is dubious.