Posted on 01/23/2007 8:52:26 PM PST by John W
I suspect that some very dubious and imprecise assumptions underlie the numbers in this probability calculation. How many asteroids? How big is each asteroid? Which year does each asteroid hit? How many people are in the area? Etc. Never mind that they're working from exactly zero previous similar events.
Maybe.I'm with those who think we ought to be doing something or I wouldn't have posted this.The yahoos who can't see beyond their own wallet disappoint me.
But nuking them would be so-o-o-o much more cool!
Why not just blow it to flinders?
You're right. Send me your money, I'll put it in the trust account so we are well prepared. We'll show those sceptics by golly...
Oh come on. A little humor isn't a reason to delete posts. consider the topic...
You have to admit, it's low maintenance compared to other methods, once the job is done. Then it's up to the Sun to do its thing.
The best case performance of the thing would require that the engine thrust equals the amount of force to be exerted on the asteroid, but unless the distance between the craft and the asteroid is large or the craft uses a pair of engines firing at extremely shallow angles relative to the asteroid (which would be extremely inefficient) I would think the ejecta from the engines would push on the asteroid in such fashion as to work against the desired motion.
Why not just have a spacecraft slowly land on the asteroid, fasten itself, and then use thrusters to push the thing directly?
20 year lead time? Huh? Orbital mechanics can't predict where the rocks will be in 20 years with enough accuracy to determine if they need to be moved. That sounds crazy.
Actually, the risk in any given year that we get hit is is small. The risk over several thousand years is quite high. The results would be catastrophic.
Being hit by a big asteroid is a lot more of a threat to mankind's survival over the next 100 years than global warming--you might consider that the Gulf of Mexico is an asteroid impact crater.
Any sensible species in our situation would be taking steps to deal with a known threat of these proportions.
It really is only a matter of time. It would really suck if we diddled around for the next fifty years and then found we were in the gunsights of a big one only five years out; but we needed twenty years to get it moved. My boy and my grandkids will still be around. I'd like it to stay that way.
I'm more optimistic it's within our reach. Depending on the orbital mechanics of the asteroid, it's feasible with the technology we have today.
For example, there was the Near Earth Asteroid Rendezvous (NEAR) mission that intercepted Asteroid 433 Eros in February, 2000 and orbited the asteroid for a year before being commanded to attempt a controlled descent to the surface of Eros. The Deep Impact mission sent a spacecraft on a flyby of Comet Tempel 1 and released an impactor object crashing into the comet in July, 2005. NASA's Stardust mission intercepted Comet Wild-2 and returned samples back to Earth in January, 2006.
An asteroid that makes a close approach to Earth and is destined to strike the Earth many years later on a return orbit could be a prime candidate for a gravity tractor mission to launch for a rendezvous on the first pass of the asteroid.
There are several factors that could make this extremely difficult to accomplish. The asteroid may be tumbling in a random fashion at a high rotational velocity. Even if one could manage to land, using thrusters effectively on a tumbling object is problematic. The surface of the asteroid might be extremely irregular and rocky making the landing treacherous. Furthermore, the composition and properties of the asteroid are likely not well known which makes it difficult to design anchors to plant into the surface.
Another idea I read about is to launch, rendezvous, and set up a large reflective mirror that concentrates sunlight on the asteroid which would heat it up and cause out gassing which would deflect the orbit ever so much. The mirror could be made out of light weight mylar film. If it's tumbling at a fast rate I don't know what you'd do.
Comets outgas. Do meteors do so, also? I thought that they were mainly composed of iron and nickel.
Which is susceptible to magnetic influence. Hmm. I wonder if there will eventually be some practical way to use that to deflect it.
What could be more obvious than that "a sufficient mass" would be most economically available from a small body with low gravity?Or that the acquisition of that mass would require less energy, as the original trajectory of said mass was closer to that of the asteroid you are trying to deflect?
Or that a piece of the threat asteroid itself would fill that bill better than anything else?
I only see disadvantages to attempt to steer the threat asteroid using a second, companion celestial object.
Even in the highly unlikely event that a small, companion celestial object exists near enough to the threat asteroid to be useful, it might not be detectable from Earth and its properties known at the time of launch. Moving two, small celestial objects in close proximity to each other, but allowing both objects to travel in free drift does not accomplish the objective with an acceptable degree of certainty.
Whatever tractor object is used (man-made or second celestial object), it must be propelled and steered intelligently to exert gravitational force on the threat asteroid along a constant vector over a very long period of time.
The success of the gravity tractor method, or any other method, to divert an asteroid depends on reducing variables and reliance on assumptions to an absolute minimum. If it doesn’t work the first time, we probably won’t get a second chance using the tractor method.
Reducing the celestial objects involved greatly reduces uncertainty. Keeping the threat asteroid intact in a single piece is critical. The “drill and nuke” method seen in the film Armageddon is fine for movie entertainment thrills, but not preferable in reality. It introduces numerous, unpredictable variables and creates intolerable uncertainty in estimating the number, size and trajectories of the resulting asteroid fragments and, thus, unacceptable risk of making the threat to Earth worse.
The gravity tractor solution has the elegant advantage of relying on a precisely known mass of a spacecraft and highly predictable gravitational attraction. The greatest remaining uncertainty in the tractor method is spacecraft navigation and long duration survivability. Both of these challenges can be overcome based on our prior experience and existing technology.
HA! I spit my drink!
Face it. If an asteroid hits the earth wiping put civilization, it's an act of God and you're gonna die.
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