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Asteroid 2004 MN4 May Hit Earth After All
ControlFreal writes "Asteroid 2004 MN4 was introduced earlier on Slashdot, and although scientists are now fairly certain that is will miss earth on April 13th, 2029, the modification to its orbit caused by Earth's gravity may still cause an impact one or a couple of orbits further down the road, the Times reports; the impact probabilities in 2035, 2036 of 2037 will not be known until the exact modification to its orbit is known; in 2029, that is. By then it may be too late for effective counter-measures.
An impact would cause an energy release equivalent to about 1 Gigaton of TNT (~4e+18 Joule), and while that won't cause a massive extinction event, it causes widespread devastation.
More info on 2004 MN4 can be found here and here."
The following NASA page contains an impact risk summary of several near-earth object:
http://neo.jpl.nasa.gov/risk/
Note that this one is in the top three, but with due respect to Douglas Adams, "Don't Panic" appears to be in order.
0.865 gigaton for 2004 MN4 impact
vs
32 gigaton for Indian Ocean quake/tsunami, 2004
without some new propulsion technology i doubt even by 2029 we will have this option.
New propulsion technology? You mean like Nuclear Pulse, Nuclear Thermal (also in Trimodal for low atmospheric work), Nuclear Salt Water, M2P2, and hundreds of other mature, semi-mature, or proposed methods that we haven't used because it's "too damn expensive to get off this rock"?
Propulsion is *not* the problem.
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How is "0.1 lunar distance" not closer than the moon?
Well, it's only going to intersect the proper altitude at two points, right? Remember that geosynchronous satellites occupy a very narrow band over the equator. The asteroid may not intersect that plane at all. Even if it did, it'd be unlikely to hit anything.
I'm not sure what standard spacing is out there, but I'm sure it's at least a few hundred km. The chance of a 1 km object hitting one of these widely spaced, small objects is not great.
As for perturbation, I'm sure it's negligible. Even if it wasn't, the satellites should have sufficient station keeping ability to stay put.
The problem with those designs is legal - the US, Britain, and (through the former USSR) Russian are prohibited by the Limited Test Ban Treaty and the Outer Space Treaty from exploding nuclear devices in space. That prohibition may also cover engines like Nuclear thermal if it releases radiactive material. I'm all for nuclear propulsion, but those pesky international treaties get in the way.
Bush is planning cuts in astronomy budgets.
Zhrodague.net - I do projects and stuff too.
4x more likely to hit then in 2035. Impact risk
That's a lot of space. Geosynch orbit is 22,000 miles. Tack on 4,000 miles for the earth's radius, and it's a shell of space with a surface area of 8.5 billion square miles. Let's pretend we've got 50,000 satellites in that area by 2030. That means 1 sallite per 170,000 square miles. That suggests one satellite occupying a square of space 500 miles x 500 miles, and this thing is under a half mile across, probably less than a quarter-mile. The chances of it impacting anything in that orbit is incredibly tiny.
Caveat: my math may be off, but the point stands. This object occupies a TINY region of space, and satellits occupy an even TINIER region of space. There's no cloud of buzzing satellites around the planet, they're sparsely populating a huge shell around the planet.
"I have never won a debate with an ignorant person." -Ali ibn Abi Talib
Explanation
Several tons of Uranium per hydrogen bomb? No offence batman, but I don't think you exactly understand how those work.
A critical mass of Uranium-235 is somewhere around 112lbs. If you had several tons of uraniumin one spot you'd have one very large uncontainable spontaneous reaction going on.
H-bombs (also called thermonuclear bombs) don't typically use uranium. They use a smallish bit of Plutonium, perhaps a bit of deutrium or tritium to boost the initial fission reaction, and a material called lithium deuteride. Neutrons and heat created from the fission reaction cause spontaneous fusion of the lithium and deuterium atoms.
They can use depleted uranium (u-238), this is part of the third stage of the bomb. Because of the heat of the fusion, the normally un-fissionable uranium can be fissioned to give the bomb an extra kick at the cost of making a normally relatively clean bomb much more radioactive.
It's much more practical to scale the amount of lithium deuteride in the bomb (which is only limited to the vehicle carrying it, and it's much lighter than uranium, obviously), because once the fusion has started it keeps going till there's no more fuel.
While you're right that Hubble wouldn't be too useful for tracking this asteroid, Hubble is perfectly good for looking at things in our solar system.
Relevant figures for a 75 km. distant sedimentary rock hit:
For 30 km. range:
Doesn't sound like too much fun at 30 km.!
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The actual amount of radioactive materials released by these designs is pretty trivial - only of political importance, not environmental. However, the risk of disaster is large. A uranium-based fission pile can be made quite safe if it's never been used: uranium is a *lot* safer than most rocket fuels. Once you start using a fission pile you start building up dangerous decay products, but even that might not be a problem for an engine that wasn't re-used.
Orion is the exception, but orion is silly for moving anything smaller than a city into space.
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The Earth Impact Effects Calculator lets you calculate the destructive effect of various asteroid impacts.
Seastead this.
You're right, about the mark iv bomb, but you're wrong in the fact that it's simply an implosion type fission weapon, with a yield of 20kt. It's the same thing we dropped on Nagasaki. Very big, very clumbsy, pretty heavy, and for a nuclear weapon, relatively low yield. Contrast that with a device that was made about 10 years later: the W-31. Weight 900-1000lbs. Yield: 1-40kt, depending on the build..
We have in our stockpile weapons that weigh as little as 2800lbs that can do 5 megatons. We certianly don't need a saturn V to loft those.