[Scenario] We have 4 years.

[Whirligig Girl]

Suddenly, a catastrophe has occurred. Well, not really "Suddenly". Pallas has had something horribly wrong happen to it's orbit for some reason, and now on December 12th, 2018, Pallas will hit. It's actual impact location is on the east coast of America, around Virgina to North Carolina. Pallas is huge. It's 2.11E+20 kilograms, at a diameter of around 580 kilometers. It comprises almost 7% of the mass of the asteroid belt. And it's just partially deorbited. It's heading on an impact with Earth at precisely 10:32 EST on December 12th, 2018. It's on a grazing trajectory, which means it will just barely hit the Earth.

The question is, what can be done? Will humanity simply accept it's fate? A mass extinction event far greater than that which caused the extinction of the dinosaurs. Will we try to evacuate? Only 4 years! Speeding up a Mars or Moon colony perhaps? It would need to be totally self sustaining. Maybe the best bet is to attempt a redirect? Pallas is MASSIVE! And we only have 4 years! What do you think could be done?

(In case any of you were confused, this is a fictious scenario/thought experiment. Don't be worried about Pallas.)

Edited December 9, 2014 by GregroxMun

[Bill Phil]

Orion starship. Only thing big enough and powerful enough. Grabs Pallas, sends it on a trajectory that flies completely beyond Earth's SOI.

[astropapi1]

Orion starship. Only thing big enough and powerful enough. Grabs Pallas, sends it on a trajectory that flies completely beyond Earth's SOI.

In 4 years? I don't think so it would be enough.

[G'th]

Best option is a split op between redirect and an orbital Ark.

See, what people never realize about surviving an extinction level event is that you don't have to necessarily leave Earth orbit to survive it. Provided you can time the orbit of your Ark station so that it can't possibly be effected by the asteroid(s), an Ark in Earth orbit would do well and could be constructed far quicker and easier than a colony on Mars. Obviously you couldn't save everyone (and lets face it, given the scenario and the time frame, no more than a million people at best will survive it regardless) but given the relative ease of construction and the literally unlimited resources that would be dedicated to it, an Ark that could support a large enough portion of the human population to continue the species on would be the best idea given only 4 years to do it. Going to Mars would require too much research compressed into too little time.

It also gives us the best option for repopulating Earth relatively quickly after impact, as any habitable areas would likely be easy to reach to establish a surface base.

But, naturally, abandoning 99% of the Earth's population isn't going to go well with everyone, so obviously redirect has to have effort dedicated to it as well.

[Starman4308]

Well, you doomed humanity.

No way to make a self-sustaining colony anywhere for decades. In order to survive anywhere but Earth, you need heavy industry, and that means hundreds of thousands of people.

No way to get a redirect: you'd need on the order of 10^14 tons of NTR fuel for redirect. You'd basically need millions of Falcon Heavies to redirect by even a few tenths of a meter/second.

No way this could ever happen, because it would take something huge to redirect Pallas to an Earth-crossing trajectory, and everything huge is accounted for.

Edited December 9, 2014 by Starman4308

[Kibble]

I think with repeated launches you could set enough impactors on fast solar escape trajectories to redirect even something as massive as Pallas in 4 years. Pioneer 10 was launched March 1972 and got to the Asteroid Belt February 1973 - less than one year! It would be a Cro-Magnon solution, but doable with currently available hardware.

[xenomorph555]

There is absolutely no hope for the AU, the only possible way in my mind is damage it with many 100 megaton bombs, but that probably won't work. I'm gonna go with G'th who mentioned the ark station.

[Starman4308]

I think with repeated launches you could set enough impactors on fast solar escape trajectories to redirect even something as massive as Pallas in 4 years. Pioneer 10 was launched March 1972 and got to the Asteroid Belt February 1973 - less than one year! It would be a Cro-Magnon solution, but doable with currently available hardware.

I don't think you quite understand the sheer size of Pallas. It is 2.11*10^20 kg. A billion tons of impactors going at 10 km/s would change its velocity by something on the order of 50 micrometers/second

Even a hundred years of lead time would be difficult. In order to get a 50 mm/s velocity change over 80 years, ignoring the mass of the solar sails, you would need 500 million km^2 of solar sail. I may have done the conversions wrong at some point, but given my only reference value (10 g/m^2), that is 5 billion tons of solar sail.

EDIT: I also assumed (really badly) the same thrust you'd get at Earth. Pallas is further out, the thrust should be lower there. I also slipped a few zeros on the impactors, on account of dividing by a billion kilograms instead of a billion tons.

EDIT #2: Where did I get ^21? Woohoo, I get to slip a zero. Not going to change the final results much.

Edited December 9, 2014 by Starman4308

[Whirligig Girl]

Let's assume it's on a grazing trajectory, which means it will just barely hit the Earth. Perhaps huge ground-built lasers could blast Pallas and make part of it's surface act as a thruster. You'd not need too much for a change that makes Pallas fly by the Earth just outside the rouche limit. Maybe send a few thousand Mass-Drivers to the surface to throw the surface out and act as a thruster, or even blast it with the world's supply of nukes to redirect it. (not blow it up)

We don't have to push Pallas, maybe Pallas can push itself.

[Kibble]

It doesn't take 100-megaton bombs to push something off course. Earth is a small target, and a little delta-vee goes a long way, over long distances. We had 8 Atlas V launches this year, and with the threat of extinction we could probably churn out at least double that, plus the other active launch vehicles capable of sending probes on solar escape trajectories. The closer the asteroid gets, the less each launch pushes it off course though.

EDIT : Somebody posted some math! I guess basic impactors won't work as well as I'd assumed.

Edited December 9, 2014 by Kibble
math

[ZetaX]

It also gives us the best option for repopulating Earth relatively quickly after impact' date='[/quote']

So how exactly are you planning on repopulating a ball of molten rock¿

[Newt]

There was a study in the late sixties (I believe the sixties) that examined the possibility of blocking an object (not as big as Pallas) from an impact with the Earth. The conclusion was centered around the launch of several Saturn V's (those were the days) armed with nukes. These would fly close to the object, and detonate at a range so as to dislodge a large mass of presumed regolith from the surface, as reaction mass. After each detonation, the results would be examined, and plans tweaked to ensure that they do the course change right, and as a last ditch effort, there was the possibility of blasting the thing to bits, and hoping that most of it vaporizes.

We no longer have the Saturn V's, of course, but advances in propulsion technology, computer technology, and nuclear weapons technology might would simplify this deflection. Also, they were saying that there was one year, not four.

[EzinX]

Ok. So you need a place to live. Bonus points if that place has raw materials that you didn't have to launch. And it needs to be safe from Pallas.

There's actually only 2 possibilities if a redirect isn't physically possible. You can either build an underground or underwater protected habitat (how much devastation are we talking about here? Will we know in advance which side of the planet it will impact?) or you can build one on the moon.

Advantage of the earth habitat is that even post-impact, some of the plants and animals might survive the ice age and you would need a lot less technology to survive even in this hostile environment. The moon habitat's only advantage is that the impact shocks won't affect it.

I need more data on the effects of the Pallas impact, but, I suspect that building 3 massive equidistant earth habitats along the equator (since you probably don't know where they will impact), each stocked with years of supplies and essentially an entire Noah's ark worth of plants and animals (well, whatever you can reasonably store, you'd probably have to store most plants and animals as DNA samples and hope to be able to restore them many years later) would have the best chance of species survival.

[Whirligig Girl]

Man who caused the Pallas Event found, murdered brutally.

One Gregroxmun Bohannon had been found to be the cause of the imminent destruction of humanity. An internet discussion forum for a spaceflight videogame had a hypothetical scenario posted to it on December 8th, referring to the recent orbital failure of the asteroid 2 Pallas. The original poster of the thread was tracked down to the HypeTrain Sheds of North Carolina, where astronomers have detected a mysterious radiation beam radiating from, to Pallas. The radiation beam appears to have been a tractor beam that has moved Pallas's orbit significantly. Upon the release of this information, Bohannon was tracked down by several crazed madmen and brutally tortured and murdered. Unfortunately, Bohannon was the only one who could have reactivated the tractor beam to redirect Pallas. Bohannon's murderers have been brutally murdered for this failure.

[Starman4308]

Ok. So you need a place to live. Bonus points if that place has raw materials that you didn't have to launch. And it needs to be safe from Pallas.

The energy released from a Pallas impact at escape velocity is about 3*10^28 J. The energy required to melt Earth's entire crust is 2.9*10^28.

Do you really think anywhere on Earth's surface would escape?

[Jouni]

According to the Wikipedia, we need around 1e-2 m/s of delta-v a few years before an asteroid impact to avoid the impact. The mass of Pallas is around 2e20 kg. Assuming that we can make something hit the asteroid at 1000 km/s, we need around 2e12 kg of it for the task. In order to avoid the impact, everyone on Earth just has to launch a 300 kg impactor at 1000 km/s at the asteroid (or 30 tonnes at 10 km/s). Sounds easy enough.

[Starman4308]

According to the Wikipedia, we need around 1e-2 m/s of delta-v a few years before an asteroid impact to avoid the impact. The mass of Pallas is around 2e20 kg. Assuming that we can make something hit the asteroid at 1000 km/s, we need around 2e12 kg of it for the task. In order to avoid the impact, everyone on Earth just has to launch a 300 kg impactor at 1000 km/s at the asteroid (or 30 tonnes at 10 km/s). Sounds easy enough.

According to that analysis, you can probably shave off ~99% of my solar sail mass. Probably even more, because that estimate is probably a rule of thumb for short redirect time.

We're now down to 5 million km^2 of solar sail, massing a mere 50 million tons, for 80 years of lead time.

[Skyler4856]

According to the Wikipedia, we need around 1e-2 m/s of delta-v a few years before an asteroid impact to avoid the impact. The mass of Pallas is around 2e20 kg. Assuming that we can make something hit the asteroid at 1000 km/s, we need around 2e12 kg of it for the task. In order to avoid the impact, everyone on Earth just has to launch a 300 kg impactor at 1000 km/s at the asteroid (or 30 tonnes at 10 km/s). Sounds easy enough.

10 cubic meters of osmium traveling in retrograde solar orbit would do the trick.

[Starman4308]

10 cubic meters of osmium traveling in retrograde solar orbit would do the trick.

Were you using kinetic energy? You should be using momentum. If I did my math right, 10 cubic meters of osmium traveling at 60 km/s relative will impart enough momentum to Pallas to change its velocity by a whopping 60 picometers/second.

p=mv

m1v1=m2v2

m1 = 10 m^3 * 22600 kg/m^3 = 226000 kg

v1 = 2*Earth's orbital velocity ~= 60000 m/s

m2 = 2.11*10^20 kg

v2 = m1v1/m2 = 226000 kg * 60000 m/s / 2.11*10^20 kg = 6.43 * 10^-11 m/s = 64.3 pm/s

EDIT: If nothing else, this thread has given me a significant appreciation for the ridiculous size of Pallas. I suspect the shortest survivable lead time is on the order of 100 years, and that's including options like "colonize Mars". Maybe some hardened bunkers somewhere might survive the impact and provide a shorter time-frame solution, but it'd really do a number on everything on Earth.

Edited December 9, 2014 by Starman4308

[Tommygun]

With only four years, dig really deep bunkers under Antarctica and hope you get lucky.

[Kerbart]

One can be cynical here. Three years will be wasted on bickering over that this is only a "theory" and that we should not waste tax payer money on this scientific dream project as we need jobs, not rockets.

If proof of the looming impact can no longer be denied, we'll be able to build an ark to save the most important people to humanity -- the senate and the house of representatives. And maybe a governor or two.

[Starman4308]

If proof of the looming impact can no longer be denied, we'll be able to build an ark to save the most important people to humanity -- the senate and the house of representatives. And maybe a governor or two.

Don't forget their corporate sponsors!

I wouldn't usually do political humor, but the question is so ridiculous that it deserves ridiculous answers, like maybe praying a wormhole pops up near Saturn so we can go explore a black hole.

[Guest]

We have heavy lift vehicles in storage. NASA has mothballed Saturn Vs (in museums and the like), and Russians have old Energia tanks and engines (booster ones are in production and constant use, core ones are mothballed). We can design a 100MT nuke, and we can make it a shaped charge (it's nontrivial, but possible). The theory and hardware are here, we'd just need to put all our effort into getting this to work.

The biggest obstacle would be getting the governments to actually shut up and start working together for this. Russians have the hardware, but no money. US has the money, but refurbishing a Saturn V would be both less useful (less payload) and more difficult than an Energia. The Russians had the bomb, but it's the US that researched nuclear shaped charges (though they could probably make a 100MT one, it'd just be their first one). If they managed even one bomb, and if it worked, the Earth would be saved.

And how would that look? Energia launches the nuke into LEO, a transfer stage (there were several proposed, none built. They'd most likely use some old retainer, like Blok D) brings it into solar orbit, the nuke maneuvers itself towards a close asteroid encounter (we've done that a few times already, maybe the transfer stage handle that), aims and blasts the asteroid with a focused beam of energy. The crust is vaporized, providing further thrust to push the asteroid off course. Problem solved.

[Whirligig Girl]

Don't forget their corporate sponsors!

I wouldn't usually do political humor, but the question is so ridiculous that it deserves ridiculous answers, like maybe praying a wormhole pops up near Saturn so we can go explore a black hole.

I wonder why the

future5Dhumans

put the wormhole around Saturn.

[Tiberion]

Heh 4 years? Might as well build a 600km-wide trampoline at the impact site.

No, the easy answer would be to nicely ask whatever god-like creature that was able to redirect Pallas enough to hit Earth to kindly undo that and not murder all of humanity.