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There's no need to freak out yet, however. Lawrence Livermore National Laboratory (LLNL), NASA and the National Nuclear Security Administration are on the case, and they're thinking about wielding a big Hammer.
Hammer stands for "Hypervelocity Asteroid Mitigation Mission for Emergency Response," which is an impressive name all on its own. Hammer's a concept at the moment, but if built, it would be a 30-foot-tall (9 meter), 8.8-ton spacecraft that could act as either an asteroid battering ram or as a delivery vehicle for a nuclear device. Let's call it the "nudge or nuke" option.
Bennu is a beast, according to the national lab. It's 1,664 times as heavy as the Titanic and measures more than five football fields in diameter. If it hit Earth, the impact would unleash 80,000 times the energy of the atomic bomb used on Hiroshima in 1945. It would be devastating.
Hammer is designed to launch using NASA's Delta IV Heavy rocket. Researchers at Lawrence Livermore published a paper in the journal Acta Astronautica in February that evaluates the options for using the spacecraft to successfully encourage Bennu to redirect from Earth.
The researchers say ramming the asteroid to change its course would be ideal, but it would need to be a "gentle nudge" that doesn't cause it to break up. It's a complicated proposition.
The team looked at a variety of scenarios. For example, if Earth started launching Hammer missions just 10 years before impact, "it was determined that it could take between 34 and 53 launches of the Delta IV Heavy rocket, each carrying a single Hammer impactor, to make a Bennu-class asteroid miss the Earth," the lab reported on Thursday.
All of this makes it sound like a gentle nudge might not be the best solution for big asteroids.
(Score: 2) by ledow on Monday March 19 2018, @01:43PM (9 children)
Maybe all my physics classes were bunk but:
- To move an object that huge you need a huge impulse (force over a period of time). One short bang isn't going to cut it, and is much more likely to just cause debris. You're going to want a long, sustained push.
- I seem to remember "equal and opposite reaction". If you blow up a device with the intent of pushing it one way, you need a force the other way. If you don't, pretty much the force goes where it likes, not where you want it. You can jump because you push off from the earth. Explosions hurt because the air contracts and pushes against something of lower pressure. Quite what is the explosion going to push "against" to move the object the other way? I think it'll just go boom and all the energy will dissipate into the vacuum of space rather the humongously heavy object.
It seems to me that with current technology anything other than "attach a thruster to it and make it push as long and as hard as possible" is nonsense. And all but rockets are pretty pathetic outside Earth's atmosphere. And they work by pushing enough material out the other way that it ejects a significant percentage of the mass you want to move. In other words, you're going to need to use an awful lot of fuel.
All the fancy technology in the world at the moment doesn't beat a handful of very simple Newtonian equations, which means we need a lot of mass pushing against the lot-of-mass we want to move, for a long time in order to move anything at all. Pretty much, the rockets and fuel are almost the entire weight of any launch from Earth. Everything else is really just filling.
To move 79bn kg is an awful lot of thrust and mass. For reference, that's about 28,000 Apollo 11's fully fuelled worth of mass to move (Apollo 11 was 2,766,913kg loaded, 239,725 kg empty, 2m kg was just liquid oxygen!)
Sure, we probably don't have to push it very far, and in theory you could push it with a cotton bud if it did it for long enough, but I'm not at all sure that there exists a single practical capability to move such mass in a vacuum very much at all. You could point a fully-fuelled Apollo 11 with all its rocket boosters at it and it'd barely feel it. That's assuming you could get that kind of mass out of Earth, near to the object, attach it and not use any of its own fuel en-route.
But we're not talking about a couple of nukes, or just shoving it over a bit. That's an enormous weight and there's pretty much nothing we can do about it except maybe in the thousands-of-an-inch kind of hairline adventure.
You're talking about something weighing nearly 16 times more than the Great Pyramid. It's gonna take one hell of a mission to shift that even slightly to the left in space where you have nothing to push against.
(Score: 0) by fakefuck39 on Monday March 19 2018, @02:22PM (3 children)
they probably were "bunk". 1/2mv^2. notice the velocity is squared. ever get hit by a strong gust of wind that knocked you down? lemme tell ya, the wind didn't have the mass you did but it still knocked you down. what they're talking about is throwing 50 little rocks at it really fast.
(Score: 2) by FatPhil on Monday March 19 2018, @03:18PM
And bennu's already got a freaking enormous v^2, we can change that barely a jot.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2) by ledow on Monday March 19 2018, @06:25PM (1 child)
Which... would be no better than 1 big rock weighing as much as the 50 small ones at the same v, no?
(Score: 0) by fakefuck39 on Monday March 19 2018, @09:18PM
yes, and if fish had fur they'd have lice. what exactly does your statement have to do with mine or the one I'm replying to?
(Score: 2) by FatPhil on Monday March 19 2018, @03:12PM
Of course, why are we trying to change its orbit when we can just spin it up in place such that when it hits earth it bounces like a skimmed stone on a pond!
Yes, these are retarded suggestions. However, I consider them only microscopically more retarded than what NASA's suggesting, for the reasons you state.
Why is nobody simply looking at developing the tech to help us recover from an impact easier? A transport system that can evacuate, and distribute supplies, hmmm, that's 19th century tech, haven't we perfected that yet? We can see the thing's left and right edges, by the time it looks like it's actually on an imminant collision course, only days away, we should be able to work out where it will land to within only tens of kilometers, and of course there would he high alert status for a larger area weeks or months in advance. If you're in the affected area, move, or be prepared to move in plenty of time. Most of the world is very sparsely populated, it's going to hit the sea or tundra, not a built-up area.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 0) by Anonymous Coward on Monday March 19 2018, @05:23PM (3 children)
Reaction mass doesn't need to be a rocket exhaust. If we could land some apparatus combination of a slingshot, a digger, and a power plant on it, we could start throwing chunks of it to one side to get it accelerating in opposite direction.
(Score: 2) by HiThere on Monday March 19 2018, @05:29PM
I think the concept you're looking for is a variation of "mass driver". Yeah, that should work. A combination automatic catapult and automatic loader working for a few years should work. But you need to give the ejecta an orbit that won't cause problems. Probably anything outside of the orbital plane of the solar system would work, though.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by ledow on Monday March 19 2018, @06:28PM (1 child)
Cool, so we just have to land on it, build all kinds of equipment, break it up into a thousand bits in a zero-gravity environment using heavy pneumatic tools, when it weighs as much as 16 Great Pyramids, then apply thrust to each part and it to separate them and somehow fling the bits somewhere safe and sensible, and do it to enough of its mass to make a big enough dent to manoeuvre it.
That sounds so much easier than just "let's stick a rocket on it pushing that way" (which is already a prohibitively expensive, dangerous, unlikely, and ineffectual method to start with).
(Score: 0) by Anonymous Coward on Tuesday March 20 2018, @01:25PM
All right, you win, I quit. There's no escape. If it is going to hit the Earth, we'll just sit tight and suck our tears up.