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Using Gravity To Tow Asteroids
cryptocom writes "Space.com is reporting that two scientists at NASA are proposing using a 20-ton spacecraft to pull asteroids off a possible collision course with Earth, using the spacecraft's own gravity as an attractor. This idea would not only be cheaper, but have a much higher chance of success, due to not having to actually land on the asteroid's surface."
2000 lbs in a ton
20 ton spacecraft
$10,000/pound to get to geosynchronous transfer orbit
$400,000,000 just to launch this thing into a geosynchronous transfer orbit (not counting construction costs). I assume the fuel to move it isn't included in the 20 ton estimate either (since it will burn off on the way) so that would need to be lifted as well. I wonder if a huge nuke would be cheaper and easier to construct and launch? Then again, with the current U.S. national debt at over 8 trillion (with which we could pay for the launch costs of 20,000 of these things) maybe the launch costs aren't unreasonable.
I Am My Own Worst Enemy
That would make the rig smaller than an 18-weeler. Their gross weight capacity is 40 tons.
That would place it safely in the realm of 'Cube Truck' capacity.
Hell, they wouldn't even have to stop at the scales in some states.
"Rocky Rococo, at your cervix!"
"The kind of spacecraft we've talked about could move an asteroid 650 feet (200 meters) across provided we have decades of advanced warning,"
Neat... although, if this works, it will totally kill the Hollywood "asteroid catastrophe" genre. The concept of sitting a giant hunk of metal next to an asteroid for 20 years to gradually shift its path doesn't exactly make for fast-paced, high-tension action movie fare.
domain combinatorics
Dealing with the impact of a 20-ton spacecraft on earth.
Interesting proposal, although the rate of towing still seems a concern if it takes a year to tow a 200 meter asteroid the small amount needed to make it miss Earth, with 20 years prep time required. Hopefully there aren't too many asteroids much larger than that which aren't currently tracked, but you never know.
If they're concerned about the amount of impulse delivered by a direct nuclear weapon impact, why not a series of projectile impacts (or at-a-distance, low impulse nuclear detonations)? While you'd have to launch more payload into space, the prep time would certainly seem to be far lower.
He's just being nice so my real father won't freeze him in carbonite and sell him for spice.
So comes the hard part of determining how far out the spacecraft would have to meet the asteriod and glide along beside it so as to veer the asteroid to a safe range of R kilometers from Earth. Any ideas?
Great, the asteroids miss the earth, but damage from falling 20-ton spacecraft becomes an issue.
"Flame away, I wear asbestos underwear"
So, by the same means they can put an asteroid in a direct collision course.
Maybe it would not have to be launched from Earth. Perhaps another asteroid type object could be maneuvered to do the same job, or perhaps a chunk of the Moon. Or maybe something that was already in orbit -- just collect a bunch of space junk, or dare I say the International Space Station?
it would be cheaper if we mined heavier rocks to use as primary weight from the moon. the lighter gravitational pull would help tremendously. you'd just have to launch a craft that transformed its parts into a container.
** "It's not my job to stand between the people talking to me, and the ones listening to me." -- Pego the Jerk
Crew? Not a chance. There is absolutely no reason to send crew on a mission like this. It would just complicate a mission that computer controls could already do more than well enough, and send the price through the roof. We're already doing completely automated asteroid *landings* (harder than it sounds, because they have very irregular gravity fields). There's no way that the 20 tonnes includes a human payload and all of the associated baggage.
No humans, no coming home. Also, they mention 20 years prep time - i.e., they're not planning to build it until a threat is discovered, and the couple billion dollar cost would be amortized over that time to perhaps 100 mil per year, split around the world's space agencies. I'm sure that's more than enough time and low enough cost. Also, a 200 meter asteroid is hardly a worldwide cataclysmic event if it hits; it's like a single large nuclear weapon hitting a random place on the planet, if you can trust the impact calculator.
He's just being nice so my real father won't freeze him in carbonite and sell him for spice.
mir weighed 135 tons and it burned up just fine on its way down. 20 tons, relatively speaking, isn't really all that much.
this isn't a follow-up story to "asteroid on collision coarse with earth" IS IT!?!?
Considering the number of asteroids etc that only get seen on the way out, asking for decades of warning is perhaps unrealistic.
Engineering is the art of compromise.
This just in:
Response from FEMA: "Not good enough. We need more time."
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...with women, but I've had mixed success(wrong body part got gravitationally attracted to my face).
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Launching the craft. How much fuel would it take to get escape velocity on something this massive? Probably not a small amount.
Why would you launch it from earth??? It's just weight for weight's sake, so build it from stuff already in space, or at the very least, on the moon. Only the engines, control module, etc would need to be lifted from earth. My personal opinion would be to find a nearby asteroid or similar of the appropriate size, shape it as needed, and slap some thrusters on/in it.
The crew. The time the crew would be away from earth would be how long? 10 years? 20 years? Managing and provisioning crews for such a long amount of time is probably among the major challenges facing the extension of our space travel abilities.
What crew? Why on earth would you crew it? Remote operation should be just fine.
Coming home. What happens when a ship this large is re-entering Earth's atmosphere? That sucker will have a lot of force coming down.
OK, now you're just being stupid. What possible reason would there be for landing this contraption on earth?
Having it slam into the Earth would be one way.
I'll form my OWN solar system! With blackjack! And hookers!
The big, huge meteor headed toward Earth. Could nothing stop it? Maybe Bob could. He was suddenly on top of the meteor--through some kind of a space warp or something. "Go, Bob, go " yelled one of the generals. "Give me that" said the big-guy general as he took the microphone away. "Listen, Bob," he said. "you've got to steer that meteor away from Earth." "Yes, but how?" thought Bob. Then he got an idea. Right next to him there was a steering wheel sticking out of the the meteor.
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If we're talking decades here, could this be used to send other asteroids into Mars to introduce the planet with some new water?
Isn't the problem here the 20 ton spacecraft?
Which
a) is difficult to move all by itself.
b) doesn't do much to a 6800 ton asteroid travelling at 1600 miles per hour.
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No. We're not talking about a big counterweight - we're talking about a functional spacecraft. That weight will be nuclear reactor, engines, fuel, etc; there's no way they'd pack it with dead weight for no good reason.
Lunar and Martian industrialization is not a twenty year job. It's a several hundred year job. I can get more into this if you care. It's questionable whether the moon could ever support a mostly self sufficient industrial base because it is so deficient of many critical elements (nitrogen, hydrogen, etc) - and imports to the moon will cost a fortune, making the concept rather questionable. The moon has an awful lot of light metal oxides, and is mostly barren apart from that. Industry doesn't just require the particular ore that you're interested in - there are always other things needed in the process (strong acids, fluxing agents, sacrificial parts, etc).
He's just being nice so my real father won't freeze him in carbonite and sell him for spice.
Just send Kristie Alley up there. That should work.
// no
Here's a thought: how about launching a far smaller, more capable space craft which is able to gain mass on its way out of Earth orbit by collecting up whatever tonnage of free-floating space junk it needs from Earth's orbit?
If it employed some sort of lightwight truss-style, perhaps geodesic framework with cable "netting", it could form a lightwieght, but voluminous enclosure that could be used to capture orbiting space junk before heading off for its mission.
Overall, the idea of gravity-towing sounds pretty neat to me.
I know that people have already discussed the possibility of mounting a rocket on an asteroid, and it has many problems (namely that the asteroid rotates, and it would be difficult to mount the rocket) But if we are talking about parking a spacecraft next to an asteroid, why couldn't you simply mount an ion engine on opposite sides of a space craft, and point one beam at the asteroid, and one beam in the opposite direction. Wouldn't this beam impact the asteroid, and thus impart a thrust. I realize this would theoretically cost twice the energy of mounting the same ion beam on the asteriod, but it could fire continuously. Does the ion beam spread out too fast, because if it could stay collumated, I would think it could be quite effective.
....Bruce Willis happy.
This is my opinion. To make sure you don't steal it, it's covered by the DMCA.
...this 20 ton vehicle wouldn't you be better off simply sending the engine up without the 20 tons and have it push the asteroid directly? Even if the asteroid rotated, you could fire the engine in bursts, once per revolution. This is hardly 'complicated', it's elementary physics. You (1) wouldn't have to launch 20 tons and (2) you could get the job done much quicker. If you can spot an asteroid 20 years in advance you wouldn't need to use the thrusters for long to push it out of harm's way.
Correct me if I'm wrong, but wouldn't pulling it with gravity use even MORE fuel, since you're basically expending the same amount of fuel to move the target, plus additional fuel to move the 20-ton gravity "tug"?
I often refer people to look at unmanned Mars missions, and determine how many of the huge number of failed Mars missions could have been saved by people. The answer is almost none. Most were booster failures, calculation errors (which humans couldn't have noticed until it was too late), failures in critical hardware, even explosive depressurization of pressurized parts (and you better believe that you have a lot more pressurized area with people!). Only two in which the computer was shut down but recoverable could realistically have been saved by humans. On the other hand, one of the missions which was salvaged likely would have killed any human crew onboard; a solar panel used for aerobraking at Mars was damaged, and they had to make it take many months longer to get into Mars orbit. This would have been fatal to the crew (unless they were equipped to do spacewalks and metal repairs, which raises the price and complexity even further).
Adding humans will around 20x your cost. So, take your pick: 20 completely different designs, or one manned mission with a significant chance of failure, for the same price. It's a pretty simple call; there's a reason why almost all probes that we launch are unmanned. The manned space program gets funding. The unmanned space program does the research.
He's just being nice so my real father won't freeze him in carbonite and sell him for spice.
The Saturn V was capable of sending around 50 tons to the moon (over 120 tons to LEO), and the planned STS Heavy Lift Vehicle will be slightly more powerfull. Even with existing rockets, the Titan IVB/Centaur and the Delta IV are each capable of sending over 6 tons to geosyncronous orbit.
For recent comparison, the shuttle orbiter is over 100 tons and capable of carrying about 30 tons of payload to LEO Cassini was about 6 tons, and we sent it all the way to Saturn.
If we could afford to launch all these things, then we can afford to launch something to prevent a cataclysmic astroid strike.
What makes them think we're going to have that much warning? A few years ago we had a fairly near miss and only had a few days warning. There wasn't a whole lot of warning about the comet that hit Jupiter either. Remember asteroids don't emit any light of their own, they are small compared to a planet or even our moon, and they are are coming in from quite far away from the Sun so they aren't exactly the easiest things to see.
Personally, if I had to take a trip into orbit (which I would very much like to), I'd pick the Space Shuttle over one of those Chinese capsules any day of the week.
Yeah but don't you think there will be a boatload of people screaming
about an unmanned mission if the fate of the world hangs in the balance?
From a political point of view I can't see anyone supporting a robot probe
mission to save the earth.
Service guarantees Citizenship! Questions Guarantee GITMO.... Amerika Uber Alles!
Nuke the moon!
If you are willing to accept the small size and long lead time, there are better solutions. How about a solar sail? How about giving it a static charge (perhaps spraying from an ion drive, but cathode rays would do the job, too) and using big-ass magnets? If it's icy you can just focus lots of heat (big-ass mirrors) on one side and make its eruptions change its course. Hell, if it's that small, just fire lots of small, fast projectiles (magnetic acceleration of moon-mined iron, perhaps). There are innumerable ways of providing the energy for the dV needed to alter the asteroid's course that do not involve that much mass, that much expense, that much Earth-provided energy, that much fine control, or even that lack of reusability. What a godawful idea.
You remember all those left over copies of Windows ME?
Ira
Yeah, they're up to, what ... 2 now? Yeah, WAY ahead of us, they're sitting at about 1958 at the moment as far as space race progress goes. I'd say something pithy about their remarkable survival rating so far, but given the closed speech society that exists over there, I'm not willing to claim that they've had no fatalities. They could have had dozens at this point, we'd never know.
"I have never won a debate with an ignorant person." -Ali ibn Abi Talib
Why just a chunk of the moon? Blowing up the moon would be kind of like using chaff when being pursued by a heat seeking missile... many more fragments. If we have 20 years, let's just dedicate that time to stuffing the moon's core so full of WMDs that when the time comes, we'll get quite a show.
My other solution is to dig a hole through the Earth to allow the asteroid to pass through its natural trajectory. If we were clever enough, we could dig a hole in such a way that we could redirect the asteroid right into the moon.
Alright, alright... I'm really just sick of these damn dogs going nuts every month.
Sounds to me like it will be travelling in parallel with the asteroid, but being that it is using gravity, it will lose "altitute" relative to the object and need to regain it by thrusting away from the object without pushing the object or damaging it, thus bending the orbital arc toward the craft ever so slightly.
No conformist ever made history.
...if I simply ask you what you think your life is worth, you may be tempted to exaggerate, so economists judge people based on their actions. Dangerous jobs tend to earn higher pay, while activities such as buying smoke alarms or buckling seat belts carry their own costs as well as bringing safety benefits.
a lue-of-iraqi-life.html
A typical calculation: you might pay up to $6,000 on a safer car that reduced your risk of dying by one in a thousand. Six thousand divided by one in a thousand is six million, so you are valuing your own life at about $6m. This is a typical result for residents of the US.
http://www.timharford.com/deareconomist/2005/10/v
You can safely ignore people in instances like this. If the mission succeeds then you'll be a hero, if it fails then politics is the least of your worries.
Launching the craft. How much fuel would it take to get escape velocity on something this massive? Probably not a small amount.
20 ton spaceship. That's actually smaller than the Space Shuttle.
I can't remember the source now, but the Shuttle can lift about a 30ton payload. The boosters themselves can lift far more but of course have to carry the Shuttle too (which is something like 120tons).
The Saturn V rocket was capable of lifting 118 tonnes (with the 3 stage versions).
The Shuttle Derived Launch Vehicle will have a capacity of 125 tonnes.
All seem plenty to lift a 20ton spaceship if it's the only thing being launched. Even with a Shuttle it should be doable, or we can have another up there waiting to deploy it or use the ISS team.
Since we're able to use existing launchers to get the spaceship into orbit, it shouldn't cost any more to launch than any existing mission. All your left with is the pricetag for building it and giving it enough fuel to reach the asteroid.
The crew. The time the crew would be away from earth would be how long? 10 years? 20 years? Managing and provisioning crews for such a long amount of time is probably among the major challenges facing the extension of our space travel abilities.
Coming home. What happens when a ship this large is re-entering Earth's atmosphere? That sucker will have a lot of force coming down.
Due to the distance it would have to travel a robotic mission remote controlled from Earth would make the most sense. Just in case anything breaks which isn't workaroundable/fixable it would probably make sense to send more than one.
In this case it'd be best to leave it out there - without enough fuel to return it'd be cheaper and without a crew to bring home there's no real reason to.
Shelf life. So we make a ginormous space tractor. Maybe we don't face an asteroid threat for 15,000 years. That's a lot of upkeep.
The launchers are already around, and it wouldn't take long to build a ship which is essentially a remote controlled engine with a lot of metal attached.
Assuming that we'd know of the threat in enough time to send this to the asteroid, as long as we still have the launchers to get it into space in the first place it shouldn't be unreasonable that we can build them as we need them.
If we don't have that kind of timescale then we're probably in trouble even if we could send it straight away. Since the launchers seem capable of lifting more than 20 tonnes though, we could just build a 40 tonne version and half the time we'd need (disclaimer: not linear, i think it'd be more like 3/4?).
Never mind moving the objects, just move the earth out of the way. Just mount an engine on the north and south poles. No need for any space travel. This can be done at ground level. A pair of coal fired steam jets should do it.
Oh well, what the hell...
Wouldn't the ions shot out the ass end smack into the asteroid, counteracting the gravitational pull?
You'd have to have at least two, and arguably more, ion jets pointed away at opposing angles such that, combined, they push the craft in the correct direction, but individually, they shoot the ions past the edge of the asteroid. Like legs on a tripod, say.
(-1: Post disagrees with my already-settled worldview) is not a valid mod option.
Put Bruce Willis on the probe. The minor detail of whether or not to include an air supply can be left to the engineers.
The crew. The time the crew would be away from earth would be how long? 10 years? 20 years?
Why does it need a crew if it's just going to use gravity to nudge an asteroid?
Don't take life so seriously. No one makes it out alive.
Nope. All gravitational force exerted on an asteroid is directly proportional to its mass. Since Force=Mass*acceleration, the mass cancels out of the equation - the acceleration (and hence the trajectory) is independent of its mass. This is the exact same reason why objects of different weights fall at the same rate - both acceleration AND gravitational force are proportional to mass, so mass cancels out of the equation.
Of course, I'm assuming that gravitational interactions with objects of comparable size (i.e. other asteroids) are negligible. My argument only holds if everything the asteroid interacts with is much more massive than it (and thus not affected much by the asteroid's gravitational pull). But I would bet that's a pretty good assumption.
You're not getting it:
F=G*m1*m2/d^2
Cutting the distance in half quadruples the force of gravity; distance is far more relevant than mass. You can pick how much gravitational attraction there is between your craft and the asteroid (within limits, but those limits aren't closed to being reached)
Lets say that your craft has the new HiPEP engine under testing (JIMO's engine). I believe that's a 0.5 newton engine (very strong for an ion engine). It takes the entire 20 tonnes of craft mass to run. Lets assume that the 200 meter diameter asteroid is porous rock with a density 50% more than water - 4/3*3.14159*(200/2)^3*1500kg=6.28e9kg. Thus, the balanced equation becomes:
0.5=6.67e-11 * 20000 * 6.28e9 / d^2
Solving for d, we get 130 meters, or 30 meters over the surface. However, it gets better: asteroids are almost never uniform spheres, and are usually somewhat oblate. Thus you can hover closer to its center of gravity if need be. So, even if we can improve the mass of the engines, radiators, or engines, we can simply fly closer to the asteroid. The larger the asteroid, the more this holds true: double the diameter of the asteroid, the hovering distance increases fourfold from the center (and 5.5x the distance from the surface). You'd have to make your craft more efficient by orders of magnitude in order to justify adding dummy weight to it.
*You Do Not Need Extra Bulk*. With the limits of modern technology, you inherently have more than enough bulk just in the functional mass of the spacecraft. And even if you needed extra bulk, scientists would *love* to supply it in the form of a science payload.
He's just being nice so my real father won't freeze him in carbonite and sell him for spice.
Assuming a spherical iron asteroid with a 100m radius (the article mentions two football fields across) and a 20 ton ship you can provide a maximum gravitational force of about 1 pound. This is find and dandy and could provide a deflection of nearly the diameter of the earth over a decade period.
But...
The problem is how to produce that required force on your ship without impacting the asteroid. Conventional rockets or ion thrusters would necessarily be directed in the direction of the asteroid which would nullify any net force on the system (ship+asteroid). If you get enough distance between the asteroid and the ship so yout thrust can miss the asteroid and provide a net force, the force you can provide on the asteroid due to gravity drops as the square of the distance and becomes unusably low. You'd need litterally centuries or millenia of advance warning!
If anyone has ideas how to avoid this problem, I'm all ears. :)
I'm disappointed in you, Slashdot nerds. For shame!
Next: Nasa patents "A Method and Process for Using Gravity To Tow Asteroids"
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Returned Peace Corps IT Volunteer
The scientist quoted in the article says: "The kind of spacecraft we've talked about could move an asteroid 650 feet (200 meters) across provided we have decades of advanced warning". 650 feet?
I'm posting this here for attribution, just in case in 20 (or 50 or 200) years from now someone rediscovers this idea. Then they'll use the archives to discover that the idea used to save the world was originally conceived by me! (and boost my Karma score into the ionosphere!).
Basically one of the big problems of moving an asteroid is its rotation. Trying to move a big spinning object, is really hard. There is a tremendous amount of energy contained in the spin so fighting it will be very expensive.
So don't fight it, USE it. Lower a long rope to the surface of the asteroid letting the spin of the asteroid keep it taught. (same idea as a space elevator). Now ferry rocks way beyond the "Geosync" point, if the rotation is anything substantial it shouldn't be too far from the surface (a few tens of kilometers, no need for carbon nanotubes). Release the rocks into space, timing the release so that they shoot off in the same general direction.
What you're doing is converting the enormous rotational energy of the asteroid into kinetic energy of the rocks. Depending on how long your rope is (and thus how fast your rocks are released) you are going to get a substantial thrust in the opposite direction. (for every action there is a reaction). You are also making the asteroid smaller. As for the released rocks, while they may someday in the distant future hit the earth they'll be small and won't make it past the upper atmosphere.
Of course in addition to the long time frame (given) that this will take; this assumes that the asteroid is rotating (probably won't have to be too fast) and that you can attach the cable to some point on the asteroid. I believe most asteroids we've discovered have a substantial rotation, this is probably due to the violent manner in which they were formed and subsequently battered. As for the cable attachment, some nets and cables stretching around the asteroid should handle this just fine.
So there you have it. Instead of launching a huge expensive power hungry spacecraft that'll provide an absolutely tiny acceleration, you could send a relatively tiny spacecraft consisting of a few solar powered low mass robots (to move the rocks to the cable) and some sort of conveyor mechanism. While this'll take some engineering, it certainly is less than trying to have a 20 ton spacecraft do precision (because gravity is inverse squared you need to be close) station keeping off a tumbling (maybe chaotically!) asteroid for decades. If the rotation rate is high enough, you could even use the asteroid to generate energy (microwave beaming?).
wisebabo
Look, the thing is that a 200 meter asteroid is puny by comparison to something that could destroy civilization. Something of that size would break up mostly in the atmosphere, and cause little to no damage to the earth. And besides, something that small we can just blow up.
What we should be worried about is one that is a few MILES in diameter. Those are the asteroids that threaten extinction.