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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?
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.
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).
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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?
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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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.
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.
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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.
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...