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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
"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
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"
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.
...with women, but I've had mixed success(wrong body part got gravitationally attracted to my face).
"You're everywhere. You're omnivorous."
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!
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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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.
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.
Actually, it would take precisely the same amount of fuel - either way, you're moving the tug plus the asteroid. The whole idea with this method is simply that gravity is a very gentle force. Pushing the asteroid by attaching a rocket to it or exploding something next to it are both very sharp, uneven forces that could very well break it up in to little pieces. Some of those pieces would probably hit the earth, even if the main bulk didn't.
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!
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.
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...
I'm disappointed in you, Slashdot nerds. For shame!
And there is another way to do it. If you put two thrusters at the end of a boom that is that is the same length as the asteroid's diameter (assuming it is spherical), you could aim them so that they are nearly tangential to the asteroid's surface, resulting in more efficient use of fuel. The downsides are 1) extra mass for the boom & dual thrusters, and 2) balancing the thrust so that the "tug" doesn't spin.
But this entire approach strikes me as overly complex. Given that the whole setup is only going to exert less than 1lb of force on the asteroid, I'd have thought it was easier to mount a gymballed 5lb thruster on the surface and fire it in synchrony with the asteroid's rotation. You'd need to spread the force across a wide surface area, and take steps to minimize vibration stresses, but that's just engineering ... not "rocket science" :-)
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