Posted on 01/23/2007 8:52:26 PM PST by John W
HONOLULU - NASA astronaut and former University of Hawaii solar physicist Edward Lu is calling for a new spacecraft that would divert asteroids on a path to slam into Earth.
The small space tractor, costing between $200 million and $300 million, would hover near an asteroid to exert enough gravitational pull that the space rock's orbit would change and a collision with our planet would be averted, Lu said before a crowd packed into a 300-capacity auditorium at the University of Hawaii-Manoa Monday night.
"We're only trying to get a really tiny change in the velocity of the asteroid to prevent an impact," he said.
Lu was part of a panel including three Hawaii scientists who characterized the chances of an asteroid colliding with Earth as rare but deserving of the same level of attention as major earthquakes, tsunamis and hurricanes.
A report on the appearance appeared on the Honolulu Star-Bulletin Web site on Tuesday.
The asteroid Apophis will pass within about 20,000 miles of Earth on Friday, April 13, 2029.
"It's going to come so close to the Earth in 2029 that its orbit will change and it might change enough so that it comes back and hits us in 2036," said Hawaii planetary astronomer David Tholen, who discovered Apophis.
During the asteroid's next close pass to the sun in 2013 that risk will be assessed in radar surveys, he said.
Objects the size of a grain of sand frequently hit the Earth's atmosphere, appearing as shooting stars in the night sky. But a larger impact could be devastating. Asteroids are blamed for the death of the dinosaurs 65 million years ago and an explosion over Tunguska, Russia, in 1908 that wiped out 60 million trees over a 830-square-mile area.
According to a presentation by university astronomer Robert Jedicke, a Tunguska-size explosion would be able to blast or burn nearly all of Oahu.
Because the devastation would be great, the risk to a person of perishing in a major asteroid collision is about 1 in 10,000 or 20,000 over a 100-year lifetime - the same dying in a plane crash, Jedicke said.
The University of Hawaii's Pan-STARRS program would train four powerful digital cameras toward the heavens to watch for would-be intruders.
Officials from the project are hoping to garner public support of a plan to locate on Mauna Kea. The telescopes also could be built at two sites on Haleakala, where a prototype is being built, but scientists warn the project would take twice as long to complete there.
Environmentalists and Hawaiian activists have argued against additional development on Mauna Kea and some scientists have expressed concern about additional construction as the volcano already hosts 13 telescopes.
The program would be able to provide decades of warning of an impending impact, the scientists said.
That would be enough time to launch a tractor spacecraft to knock the asteroid into a safe orbit, said Lu, who spent six month aboard the International Space Station in 2003 and was a postdoctoral fellow at the University of Hawaii's astronomy institute from 1992 to 1995.
To do nothing would be to invite disaster, he said.
"If we are wiped out by an asteroid, that will be our own fault at this point," he said.
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On the Net:
University of Hawaii's Pan-STARRS program: http://pan-starrs.ifa.hawaii.edu/public/
I'd like to develop space factories which land on asteroids and process them into something useful. With a long enough lead time, why just move things around?
You would need space docking and refueling. What would the propulsion system be? It would need to catch asteroids early enough that small changes in their orbits would translate to clean misses of earth. You can't do that in low earth orbit!
But just think of what it would mean to have a craft that could flit around the inner solar system with enough power to nudge asteroids! Just that technology alone could open up space travel!
Gravitational pull is determined by mass and distance. Distanc eisn't much of a problem but you're going to have to have a lot of mass to get the asteroid moved in time unless we can get far away from Earth to alter it's pass before it gets close.
Seems unrealistic but a novel idea anyways.
A tractor of that magnitude would have to have a LOT of mass to make enough of a difference. Ping for later research
Comes with previous crash experience.
The gravity tractor method is feasible if the threatening asteroid is detected early enough and at a sufficient distance from Earth. Based on calculations, it’s theorized that a 20 ton spacecraft could sufficiently deflect a typical 200 meter in diameter asteroid if given a lead time of 20 years. Deflecting a larger asteroid would require a spacecraft of greater mass or more lead time.
Whatever methods are employed to divert the trajectory of asteroids, early detection and better understanding of the objects are critical. That’s why there is great interest in funding increased efforts to explore known Near-Earth Orbit objects and search for presently undetected NEO objects.
Space barge!
I'm catching on here.
Now I think I know where they get polaroids.
http://www.space.com/news/051103_asteroid_apophis.html
More info.....
Asteroid 99942 Apophis – first labeled as 2004 MN4 -- is estimated to be roughly 1,000 feet (320 meters) in diameter. Were it to strike Earth, it would not set off global havoc but would generate significant local or regional damage, experts say.
However
The ruin stemming from asteroid Apophis colliding with Earth would potentially be very great.
Indeed, the consequences, Schweickart suggested, would dwarf those seen as a result of the Indian Ocean tsunami in December 2004, hurricanes Katrina and Rita in September of this year, and the Pakistan earthquake last month.
The gravity tractor method is feasible if the threatening asteroid is detected early enough and at a sufficient distance from Earth. Based on calculations, it’s theorized that a 20 ton spacecraft could sufficiently deflect a typical 200 meter in diameter asteroid if given a lead time of 20 years. Deflecting a larger asteroid would require a spacecraft of greater mass or more lead time.
Whatever methods are employed to divert the trajectory of asteroids, early detection and better understanding of the objects are critical. That’s why there is great interest in funding increased efforts to explore known Near-Earth Orbit objects and search for presently undetected NEO objects.
That's kind of what I suspected.
We currently have nothing with the power to move large asteroids a sufficient distance anywhere near the earth, and no propulsion systems which could get way out (say, orbit of Mars) to take the long slow approach.
I think the price estimate of a few hundreds of millions of dollars are realistic for startup costs rather than hardware in orbit.
Moving a 200 meter diameter asteroid is a major effort unless its done millions of miles out. Even then you would need a craft that could accelerate to the asteroid, slow down and reverse course to match orbit, and then effect a change in the asteroid's orbit. And after that, hopefully slow down enough to return to earth at less than asteroid speeds.
I don't think we have the propulsion systems for this yet. And I don't think we are going to develop and launch it for a few hundred million dollars.
But we should be working on such a system whatever the cost. A craft that could do that could do a lot of other important things as well.
Hmmmm...I hadn't thought about up-time of the spacecraft. Twenty years is a long time to keep something running continuously with no maintenance in a very hostile environment.
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And we'll just tx the crap out of people to pay for these dumb idea's, right? Of course, we'll need Al- Gore to make a "documentry" a few years in advance to sell the idea, cause a panic, and get the sheeple to wllingly give you their money.
cant we just build a really cool laser? it would be more fun.
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.
Mine it out so there won't even be a question of coming around to hit the planet.
Space travel is already open. Space development is not happening, and the Treaty is the sole and only reason there is no private devleopment of space resources right now.
Repeal the Treaty. Maybe private space development firms would then have a position available for you, but if you don't repeal the Treaty they certainly won't.
No doubt, probability calculations will be part of the threat assessment together with orbital mechanics. Hey, nobody said it would be easy! However, it's worth some effort because an extinction impact event on Earth would be very unpleasant, especially if mankind is snuffed out. :-)
I dunno, I'm probably absurdly ignorant about this subject - but. I guess my "but" is that I find it very difficult to figure how putting a mass into the trajectory of the threat asteroid, such that the threat is attracted to that mass enough to be pulled out of the threat trajectory, can possibly be more efficient than simply colliding with the threat asteroid. It seems to me that entraining the threat gravitationally is really, in principle, indistinguishable from colliding with colliding with it at a very low velocity.And if you in fact are colliding with the asteroid, you might as well burn your "sufficient mass" as fuel in your rocket and slam into the asteroid with that much greater momentum. It looks to me like ultimately the only issue is the net momentum of all the rocket combustion products before/during the collision. And that the "tractor" approach is simply a long-duration collision.
Bump for later reading
The idea of crashing a spacecraft into an asteroid to alter its trajectory is seductive because, at first thought, it appears to be a simple, predictable game of celestial billiards. In other words, if we hit the threat asteroid at point X with mass Y traveling at velocity Z then A, B, and C will result. They script variations of this all the time in the killer asteroid movies Hollywood produces, so it must be possible, right? It’s accomplished in a flash and everybody can breathe a sigh of relief and go on with their lives. Who wants to fret over a boring gravity tug on a killer asteroid that drags on for 20 years?
Unfortunately, the reality of the situation is very different. A solution in the collision scenario can be calculated with barely an acceptable degree of certainty only if we know beforehand the exact material composition of the threat asteroid in all regions and its mass distribution to a degree of certainty approaching what we know about a billiard ball. To obtain that scope and depth of knowledge about a small celestial object hurtling through space many millions of miles from Earth is essentially hopeless. Even if we had the requisite knowledge of the asteroid, the solution might show a sufficient mass for a collision scenario couldn’t be constructed and delivered from Earth in time.
A basic rule of killer asteroid wrangling has something in common with the ethical practice of medicine described in the Hippocratic Oath, i.e., “First, do no harm”. Since the precise consequences of a collision can’t be predicted or quantified to an acceptable degree of certainty, it’s wise to attempt to alter the trajectory of the asteroid without adding the risk of making the problem worse; especially if the result might be multiple asteroid fragments. The stakes would be too high to do otherwise if an approaching asteroid threatened Earth with an extinction impact event.
Use a nuke or an ion engine tug and a fission reactor for power. Problem solved.
Of course watching Greenpeace go into meltdown over nuclear reactors and weapons in space would be worth it as well.
WE'RE GONNA DIE!!1!
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