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Gravity Tractor Could Deflect Asteroids
Hugh Pickens writes "A new study at the Jet Propulsion Labs shows that weak gravitational pull of a "gravity tractor" could deflect an Earth-threatening asteroid if it was deployed when the asteroid was at least one orbit away from potential impact with Earth. First a spacecraft would be crashed directly into the asteroid, similar to the Deep Impact mission that impacted a comet in 2005. This would provide a big change of direction, but in a less controllable fashion that could push the path of the asteroid into a dangerous keyhole. But then a second spacecraft, the gravity tractor, would come into play, hovering about 150 meters away from the asteroid, to exert a gentle gravitational force, changing the asteroid's velocity by only 0.22 microns per second each day. Over a long enough time, that could steer it away from the keyhole. In the simulation, a simple control system kept the spacecraft in position, and a transponder on the asteroid helped monitor its position and thus determine its trajectory more precisely than would be possible otherwise. 'The gravity tractor is a wimp, but it's a precise wimp,' said astronaut Jack Schweickart. 'It can make very small, precise changes in orbit, and that's what you need to avoid a keyhole.'"
John Deere got the contract beating out Cat.
Do I get a nifty green hat to wear while I'm on it?
"It is a miracle that curiosity survives formal education." -Albert Einstein
I hope their simulations use doubles, not floats!
Or 1/3rd US population ?
Yes take 1/3rd of the US population and put them on early warning duties. It sounds as this has some pretty hefty notification requirements to be an effective scheme.
On the Oregon Cost born and raised, On the beach is where I spent most of my days
In a sense, you could apply the same approach, except try to modify earth's orbit, which might actually be easier...
Harder...harder...too hard!
Bruce Willis hovers over an asteroid for two action-packed hours!
http://twitter.com/OLDTELEGRAM
Can you imagine how much the tires go for on a gravity tracter? Those things have gotta be be Ginormous!
Will be done by holding monthly Gravity Tractor Pulls at the local fairgrounds, with free beer.
Just disrupt the deflector shield with a tachyon burst.
0.22 microns per second per day?
What kind of lame units are those?
How about 2.5 x 10-12 m/s^2
If the first spacecraft moves it significantly why not just keep throwing those at it. If you are planning on moving this thing by the micron then the first can't be all that innacurate because you'd never be able to nudge out any drastic error. Just keep throwing the firt at it until we're OK.
Que the space rednecks.
Could someone with the proper knowledge submit a Wikipedia article for keyhole? The word is used in the summary three times and seven times in tfa. I guess the term is here to stay.
Thank you.
Their they're doing there hair.
... and I thought it would be more like this.
How is gently pulling the asteroid with a weak gravity string more efficient than just landing the same "tractor" on the asteroid and pushing it gently but directly?
and what do we do when they mess up the calculations and we turn a near miss into an impact.
For a backup plan please use nukes.
or to hit one.
If all they're trying to do is move the orbit of the asteroid by a fraction or a millimeter per second, wouldn't it be easier to just, you know, harpoon the asteroid and use ion engines to gently pull on it rather than trying to keep a second spacecraft hovering over the non-smoking crater of the first spacecraft? Or, if harpooning isn't viable (cue 'Whalers on the Moon'), just have the spacecraft rest on the asteroid's surface and, using ion engines again, push on the thing.
Can someone more well versed in orbital mechanics and the motion of bodies in space please provide some information as to why these are not viable options.
We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
I'm glad I already read this story and understand the metaphor, because the summary is rather unintentionally surreal otherwise.
No kidding!!! What do you say at this point?
As I understand it, they used a hypothetical asteroid measuring ~140 meters in diameter. The Apophis asteroid measures ~1000 ft in diameter. As I understand it the mass scales as well so, outside of launching something exponentially heavier, how does this solution scale?
Not that I don't believe in NASA, I am actually applying for a job at JPL this fall.
From TFA: "...it would exert a gentle gravitational force, changing the asteroid's velocity by only 0.22 microns per second each day. But over a long enough time, that could steer it away from the keyhole..."
So... would there be confirmation that this plan is working when attempting it? Honestly, with a miniscule (and possibly undetectable) amount of 0.22 microns and such a large amount at stake (olbiteration), I would want to know if Plan A is working and if Plan B should start.
I will bend like a reed in the wind.
TFA spells it out very nicely. Get there one orbit early (a year or a little longer) then gently tug. Of course that's for a small asteroid, for a dinosaur killer maybe five years. If you wait until the object is a few weeks away you are toast. Cindered toast. The entire "nuclear might" of the planet launched at the intruder will do diddley squat, Bruce Willis or no Bruce Willis. That's why NEAR should get lots more funding.
I choose to remain celibate, like my father and his father before him.
Its probably a good time to remind people that the distributed computing project to search for dangerous NEOs is soon to get under way. Test workunits have already been sent out and the news is that they ran very well.
That's a very small asteroid they're modeling, wake me up when they can do something about the mile-wide ones
a few megatons TNT of impact energy won't do much on most of the earth's surface, likely hit nothing important
but apparently they did.
In order for the "gravitational tractor" (GT) to keep pulling the object out of its current path, the GT would have to be ejecting reaction mass toward the object it was supposed to be pulling... thus pushing it away. Unless it was MUCH larger than the object it is supposed to be pulling, in which case it could eject mass to either side. Which seems unlikely.
Perhaps there is some small angle it can thrust at that does not impact the object while still pulling it away... but that seems like an even more unlikely balancing act.
What is your name?
Joe Q. Scientist.
What is your mission?
To capture an asteroid.
What units of measure were used in the mission?
English... no metric!
*KABOOM!*
~~ Behold the flying cow with a rail gun! ~~
I wanna watch from my front yard at night while drinking cold beer with my neighbors.
What?
This article is sooo 2007. http://science.slashdot.org/article.pl?sid=07/03/17/0538220
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
Next thing you know, bugs from Klendathu will throw rocks at us too.
Barman: Do you really think the world's about to end?
Ford: Yes, in just over 3 minutes and 5 seconds.
Barman: Well, isn't there anything we can do?
Ford: No. Nothing.
Barman: I thought we were supposed to lie down, put a paper bag over our head or something...?
Ford: Yes, if you like.
Barman: Will that help?
Ford: No. Excuse me, I've got to go.
Barman: Ah, well. Last orders please!
We should be watching to see if the dolphins leave the Earth by their own means.
It can make very small, precise changes in orbit, and that's what you need to avoid a keyhole. Actually, to avoid a keyhole, you just have to get drunk.
Armageddon 2: Space Farmers
they say it is often more relevant then the comment above, all we know is its called the Sig!
So . . . the tractor pulls the asteroid into a new orbit, causing it to slam into another asteroid of equal size, causing them to to split into eight equally large pieces for whose trajectory is now altered to collide with the earth.
Time to buy a lot of shares at the Tractor Supply Store.
Beer is proof that God loves us and wants us to be happy.
Ah Nukes, the redneck answer to all questions regarding earth crossing asteroids AND rouge terrorists/nation states.
If it can be guided away from the keyhole, could it not also be guided towards? I think this presents a wonderful opportunity for extortion. If I only had the resources I would shave my head, get a cool chair, and become adept at holding my pinky to the corner of my mouth in an evil fashion.
A micron is a unit of length, not velocity. Do they mean microns per second?
This is my sig.
And depending on the distance (though further away poses problems for the gravity-part) the object can subtend a small portion of the exhaust "pattern."
Further, directly above is not the only option. Halo orbits of a single body require constant thrust to maintain, which is actually quite ideal for the situation at hand: allowing the gravity tug to get closer to the center of mass (cos(phi)/r^2 is better than 1/r^2 when you can have a smaller r) and keep the body out of the way of the preferred thrust direction.
Can you be Even More Awesome?!
hated the movie
But the book was good. I am a 15 second bomb, I am 14 second Bomb...
Gravity Tractor? You know I love these sky high fantasy ideas to deflect asteroids as much as anyone else but shouldn't we be concentrating on what is real? If an asteroid does threaten Earth in the next few years we will use nuclear demolitions on it. We will not use a gravity tractor, laser beams, or giant snow balls. Nor will we attach plasma engines or mass drivers to it. We will use nuclear demolitions because that is, simply, all we have.
We will not send a robot to do it nor will we send some type of futuristic space ship driven by plasma/ion engines. It will be a manned ship with old style chemical rockets right out of the '60. Why? Because we have over 60 years experience with them and they will get the job done. We'll send men and not a robot because the mission is to important to have place in the hands on questionable technology. A robot breaks down and the mission is over. With men at least you have some hope they can fix it. Yes, it will probably be one way but the pilots will know that. They will go anyway.
Yes, we will break it up in to smaller pieces because that is best. Don't give me that shotgun crap about it scattering the damage over a wider area. We will think of that and cover it. If we let a huge honking rock ride in the atmosphere will not even slow it down. It will punch through it like it isn't even there. Worse is it will punch through the crust to the mantel causing shockwaves all around the planet.
We wont' use one nuke. We will blowup the big one then we will blow up the smaller ones into smaller pieces. We will do this until the chunks are small enough that the atmosphere will handle. With smaller chunks there is more surface area for the atmosphere to work on. Most importantly the smaller chunks will not "crack the crust" as one fat ass one would.
Supporting World Peace Through Nuclear Pacification
on my part. I am usually careful to read articles before I comment about them. :o)
Even so, I am not fully convinced by the illustration as presented. While it may not be a 100% accurate depiction, this is still throwing mass toward the "towed" object. Keep in mind that outside the nozzle, gas tends to expand outwards. It seems to me (as I mentioned) that to negate this effect, you would have to aim the reaction mass even more to the side, which would make the whole thing even more inefficient.
If they believe this would still work, then fine. I was not arguing against the idea as a whole, just pointing out a difficulty.
(I think you can achieve something like that by using a number to store the closest representable value and another one to represent the tiny difference from what it should be).
Yup. It's the Kahan summation algorithm. It works as you describe it and it used to compensate the error that happens when doing very big sums of very small numbers (exactly the situation in the gravity tractor's problem)
"Sufficiently advanced satire is indistinguishable from reality." - [Tips: 1DrYakQDKCQ6y52z6QbnkxHXAocMZJE61o ]
You have to keep a large mass close enough -- but not touching -- another mass to gravitationally "tow" it away from its existing trajectory... and away from a gravity well. This is a very delicate balancing act. Even a miniscule error will bollix the whole works.
In addition to that, you have to keep from pushing reaction mass AT the object you are towing. As another poster mentioned, at a minimum this will decrease the efficiency of the operation by a great deal, which makes the balance even more precarious.
If you can do that math, then let's see it please. Otherwise, please lose the sarcasm.
Actually, there is no free meal there. If you exert a force F on the asteroid, you get -F exerted upon the tractor. (Imagine a cute little vector mark above the F, to be completely true.) There is no known way to escape that.
If you always stay X metres in front of the asteroid, then effectively you can treat the whole system as one body. You're not just accelerating the asteroid (with mass m1), you're also equally accelerating the tractor (let's call its mass m2) with the same acceleration, or they'll collide or drift apart. So effectively you're accelerating the sum of their masses, m=m1+m2.
The force to do that is still F=m*a, or F=(m1+m2)*a. There is no free lunch. You're still accelerating the same m1+m2, and if done at the same a, you must apply the same force F. I.e., if the same rocket engine is used, you get to burn the same amount of fuel, regardless of whether they're physically in contact or weakly pulled by gravity. Using gravity there just puts a (very low) upper bound on F.
But wait, that was assuming the ideal case, where you magically apply _exactly_ the amount of force to stay always at X metres drom the asteroid. Reality is much less ideal. Such a tractor would probably have to fire rocket engines back and forth, just to stay anywhere near the prescribed distance. I.e., it would use extra fuel for positioning and maneuvering, whereas a lander with a big jet pointed "upwards" would have no such worries.
Just about the only reason I see there, is if you have to essentially rotate the system, to execute some complex maneuver with the asteroids (over aeons, mind you.) Then it's probably less waste to just move the tractor around the asteroid, than to rotate the asteroid with your thruster embedded in it.
Still, I'm kind of at a loss as to when or why you'd need that, or have the luxury of enough time for such infinitesimal accelerations to do the job. More realistically, you'd just want the asteroid's orbit changed enough that it doesn't collide with Earth. And you'll likely not have that awfully much time. So you just want to push it out of the way, hard enough to make a difference, but not hard enough for it to shatter into a MIRV of death and destruction. Probably the safest bet being to push it upwards or downwards, in regard to Earth's orbit, so it becomes a lot more inclined than the orbit which threatened to collide. You have a lot more margin for error in the calculation there. You don't need to rotate and maneuver it accurately, you just want it out of the way.
So basically while I'll agree that their method could work, I'm kinda at a loss as to why would you want to do it that way.
A polar bear is a cartesian bear after a coordinate transform.
I think when a skyscraper-sized chunk of iron is going to smash into the Earth we have much better things to worry about than any cosmic peeping toms who might be living on it. :|
It seems that if you wanted to change it's course by a continuous amount, that simply increasing it's mass by pushing other material into it's field would make the sun do the work. Just a random thought.
"Gravity Tractor" would be a great band name.
FoundNews.com - get paid to blog.,
"The gravity tractor is a wimp" ah so they found those weakly interacting massive particals!
the Astronaut Farmer
Which has the added effect of causing it to act like a gyroscope and resist further alterations to it's vector.
I don't think rotational and linear momentum are coupled in the way that you seem to imply they are, otherwise it would be a lot easier to build an inertialess drive.
Don't forget small game hunting!
lol: You see no door there!
..at least two years old
Were that I say, pancakes?
I just got a patent on giant space traffic signs to divert and manage traffic flow. More effective and it does not get stuck in space mud. Plus I can't get sued if my product fails! hahaha I'll be rich.
lol: You see no door there!
Why use one of the weakest forces in existence to move it? You'd probably get the same amount of thrust by attaching a dozen black cat bottle rockets to it. Gravity is pathetic! If I've got a paperclip sitting on a desk, the entire earth is pulling at it and yet one little 1 ounce magnet could pick it up. Refrigerator magnet 1, earth 0. They could strap a tiny, low yield rocket to the asteroid and blast it away waaaaaaay faster and more effectively. The whole gravity thing is so weak and dependent on the distance between the asteroid and the weighted spacecraft that it has a high chance of not working or at least not working enough.
Google's Super Secret Search Algorithm: SELECT @search_results FROM internet WHERE @search_results = 'good'
Just lob a used FORD at it.
Sounds like they should hire one of the broom guys from a curling team.
It's just a confession of not knowing how to build a tractor beam!
Power corrupts the few, while weakness corrupts the many.
... but it order to do that, it must keep itself moving ever so slowly away from the object's trajectory. So it must push itself away from that path by some means, which with today's technology means throwing mass in that direction. Which means rocket engines of some sort.
If you place your massy spacecraft near an asteroid and let go, the two will mutually attract each other and eventually collide. The centre of gravity of the system won't change.
So, in order for this to work at all, you need a manouevering system on the spacecraft in order to maintain its separation from the asteroid.
The thing is, though, that from a pure orbital mechanics point of view, this is absolutely equivalent to simply mounting the spacecraft's thrusters on the asteroid itself. In fact, using the gravitational tractor is probably going to be rather less efficient, because the geometry of the system is such that you have to fire your thrusters towards the asteroid --- and a certain amount of your thruster exhaust is going to bounce off the asteroid's surface, imparting momentum in the wrong direction to the asteroid.
The only things I can think of that the gravity tractor does for you that direct acceleration doesn't is:
But, given the type of accelerations we're talking about --- which will be the same regardless what technique you're using --- I wouldn't imagine that either of these would be a problem in practice. So, what makes the gravity tractor so much better than just using rockets? Indeed, what makes it better than alternative approaches like spraying the asteroid with aluminium powder (which raises the albedo, causing increased photon pressure, which alters the orbit over time)?
Actually, "The Astronaut Farmer" would be more suited for sequel here.
They could even re-edit the first Astronaut Farmer movie to match its Billy Bob Thornton with the Armageddon one.
Make it so that Bruce Willis' character is actually Armageddon Bruce's twin brother.
Only to make it bigger... have those two halfs of the asteroid from the Armageddon break into two halfs each, and back on their course to Earth.
FOUR MOTHERFUCKIN ASTEROIDS!!!
Call it "The Astronaut Farmer 2 - Four Riders of the Apocalypse".
Have Ben (Affleck), Billy Bob and 2nd Bruce (get it - Plan B) stopping one 'steroid each - with one left over to obliterate France. Again.
I'm not sayin' that it would get anywhere close to topping off The Dark Knight...
But it could probably take out Finding Nemo.
Mit der Dummheit kämpfen Götter selbst vergebens
The other techniques have so many uncertainties that it's simply too dangerous to rely on them. We have only one chance to get it right, and that's all.
Landing is fraught with uncertainties (composition, center of gravity, even existence of surface, material rigidity, locking onto surface under such tiny gravity, stability under thrust) and difficulties (rock spinning, danger and ambiguity in landing, thrust vector issues).
Crashing is likewise fraught with uncertainties (center of gravity, composition) and difficulties (waste of kinetic energy of the impactor by conversion into heat and spin, accuracy of high-speed impactor).
In contrast, the gravity tractor method is continuously adaptive and acts on all the material in the rock simultaneously, so it's immune to all the above issues. What's more, ion engines are extremely fuel-efficient, so long-term station keeping just off the rock isn't a massively hard problem.
Given just one shot at this, I would much rather trust the life of the planet to the gravity tractor approach. There's less to go wrong.
I'd send several tractors though, not just one. We simply can't afford to fail.
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
Gravity Tractor Could Deflect Asteroids
Teleporters Could Decrease Travel Time
Shield Could Provide More Protection
Photon Torpedos Could Increase Firepower
Clean Energy Source Could Reduce CO2
How about we launch 'accelotrons" to generate wormholes around the threatening asteroids and cometary matter. Just send them off... POOF! GONE. (Well, until beings from Klixator Prime and other places come knocking on our door with cease and desist orders due to all OUR life-extinguishing heavenly bodies create junk yards in other worlds...)
Previously: "Linux... Toward the Sunrise..." Now: "Linux... Toward the-- No, now, part of Every Sunrise"
Ok, the only known ways to accelerate in space are:
1) To eject matter from the object in the opposite direction (preferably at very high speed).
2) To get a push (or pull) from other matter.
To keep the tractor at the right distance from the asteroid (i.e. to keep it pulling), it would have to keep accelerating away from the asteroid. The matter ejected from the tractor would hit the asteroid, pushing it back on course and negating the pull of the tractor. I suppose you could eject the matter in a spray all around so it passes around the asteroid, but that would waste fuel and would mean keeping the craft at a pretty good distance from the asteroid, and the force of gravity decreases by distance squared (that's probably why the craft looks the way it does in the article, a dumbbell shape with much of the weight at one and and thrusters at the other). It's still not very elegant, and it's very expensive to send heavy craft into deep space to rendezvous with an asteroid.
It seems like it would be better to land a small light craft (or a number of them) with an ion engine on the asteroid's surface. Simply land, point the solar panels and ion engine straight up (or at an angle if necessary), and let it fire. Landing may be difficult if the asteroid is spinning too quickly, but scientists have used craft designed to crash land before. It should work as long as they can land and manage to hang on, even if the ion engines have to be fired intermittently to keep thrusting in the right direction. It should be cheaper than trying to send a big heavy lump of a ship to catch an asteroid, and it should provide a much better thrust-to-weight ratio.
Ah Nukes, the redneck answer to all questions regarding earth crossing asteroids AND rouge terrorists/nation states.
And those cold winter nights....
The 'Gravity Tractor' device was discussed somewhere on or off the net as it might relate to 'saving the earth'. As i recall, the topic was about the ultimate demise of our Sun .. in 5 billion years or so .. The process of the Sun's destruction will include its diameter expanding .. the Sun's surface approaching Earth's orbit.
LONG before that, of course, the heat would sterilize our world. The proposal was to navigate a large asteroid to 'lead the earth' in its orbit around the Sun.. accellerating Earth to a higher orbit, adding millions of years of biology to continue to exist.
I seem to recall that such an asteroid would need 64,000 years to accomplish its goal. At the time, i concluded that this would represent an engineering project of the largest possible scale ..
In the meantime, our highways and bridges would continue to fail, of course.
"There are 11 kinds of people: those who know binary, those who don't, and those who could not care less!"
...they can shoot her to space to deflect an asteroid.
alias possession='chmod 666 satan && ls
I wonder if anyone has thought about the difficulty of knowing precisely where an asteroid will strike as much as a year or more in advance to allow one of these "feather tickle" gravity tractors to have time to do its work. Two concepts: - Measurement error - Rounding error I suspect our ability to accurately forecast (i.e. measure) the exact path of an asteroid (and therefore the needed correction) is nowhere good enough for this. For a more realistic scenario, I suggest everyone go re-read Niven & Pournelle's "Lucifer's Hammer". "Ten million to one against ... million to one against ... ten thousand to one against..."
If you do the math, the shift is about 1.3 km during the first year. In ten years, the shift is 130 km, and in a hundred, 13000 km (~ one earth diameter). So we need to detect the rock a century before the impact, make a very precise calculation of its trajectory and park the rocket next to the asteroid for the whole duration possibly replacing or refueling it many times over.
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It will be much easier to colonize the moon if we move it a bit closer.
You make nice word problems, but you solved none of them. The problem has been described... it involves thrusting enough to KEEP the towed object SUFFICIENTLY within the influence of gravity, WHILE pulling it away from its original trajectory.
In order to "do that math", you need to have a plausible trajectory, the masses of the objects, the thrust (direction, mass, velocity, expansion charasteristics, etc.) of the engines, not to mention all the other variables... you also have to GET the vehicle there in the first place, and you need formulae to control the thrusts. For the purposes of this exercise, we can assume that the tow vehicle uses three thrusters as shown in the illustration of TFA.
So, sorry, but a few words about calculating the gravity between a couple of bodies won't do it. The problem is VASTLY more complex than that. And if you CAN do that math, then LET'S SEE IT!!! Not just a few snide words about a tiny part of the overall problem that is, indeed, pretty trivial. So... if it is so damned easy, then let's see you do it. That was my challenge, and you have not even scratched the surface. In fact, you have actually done nothing at all to back up your words.
The word problems are anything but "confusing" to me. I am simply waiting for you to put your money where your very large mouth is.
Since when did /. have so many damn rocket surgeons?
I guess we all read that spaceX launch article the other day, and are now qualified to design rockets and plan for doomsday scenarios.
Someone's been watching too much Star Trek.
In one of his books Dyson warns against the idea of blowing up approaching asteroids and proposes mass drivers that push the asteroid into a new orbit over extended periods, possibly years. Factors I can think of from the top of my head:
- a mass driver needs mass, which it gets from the asteroid. So you don't have to sling huge masses towards the asteroids.
- anchoring the mass drivers can be a problem if the asteroid is brittle. Bigger asteroids may be stronger but you also have to push harder.
- you can have many mass drivers
- the more time you have the better.
So the special thing about a gravity tractor is that it's a reliable way to attach a mass driver to any type of asteroid. The tractor still needs mass drivers and it needs a lot of mass to build up the gravity. If you see the asteroid as a "soft waterball" that is hard to push, you could consider the tractor as an empty box with . It flies over, fills itself with parts of the asteroid and starts pulling.
How about changing the gravitational constant of the universe, therefore making the asteroid lighter and easier to move? And don't you start telling me how "changing the gravitational constant of the universe is beyond our capabilities." or some other crap like that!
Lesbian Nazi Hookers Abducted by UFOs and Forced Into Weight Loss Programs - -all next week on Town Talk.
In which case a surface mounted thruster is useless.
It'll make the asteroid corkscrew along its trajectory but it won't deflect it to a large degree (depending on thrust and rotation).
Whereas a mass hovering next to the asteroid pulls continuously to the same direction.
And it is an order of magnitude easier to just hover nearby, vs landing on an unknown surface without damaging the equipment, anchoring and deploying the thrusters and making sure you land in a place where the thrusters can have an effect without sinking, falling over or breaking up the asteroid.
The chances of success on the hover method are likely more than an order of magnitude better than the landing + thrust method.
If NASA can call a rock a gravity tractor, then I'm calling my chair a hovercraft and calling my pentium 4 hal
prepare the survey weasels.
I did not assume that the thrusters would be operating continuously. Quite the opposite.
Be that as it may, you have kept asserting how easy it would be for you to calculate these factors, yet you have not -- even once -- actually made any calculations. I would have accepted some reasonable assumptions regarding mass, trajectory, etc... but now I am just laughing.