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There has been talk of manned missions to Near Earth Asteroids as an intermediate step between the return to the Moon and a manned mission to Mars. What if NASA actually tried to capture a NEO into Earth orbit using the tonnage an Ares V booster could actually deliver to the asteroid's surface? We would have to find an asteroid with an orbit that is nearly the same as the Earth so that minimal deflection would be required to bring the asteroid into Earth's gravitational influence, and then, another impulse would be applied to slow the asteroid down to under the local escape velocity, thus bringing the asteroid into an orbit around the Earth, that way the asteroid could be studied more closely and its resources utilized.
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An enormous amount of energy would be needed to capture even a small asteroid, they have megatons of mass! It's far far more efficient to visit it for study, and if it has suitable resources, bring them back to Earth orbit.
An Ares V would almost be needed just to send Orion with crew to a NEO and bring them back to Earth.
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What if several Ares V rockets were sent along with the one carrying the astronauts, the other rockets would carry pieces of a mass driver which when assembled can use the asteroid's own regolith as reaction mass to push the asteroid into orbit around Earth. Gerard O'Neill evisioned some operation of that nature occuring eventually. The mass driver would be solar powered, accelerate buckets of asteroid material and fling them off of the asteroid at 7 km/sec, sacrificing some of the asteroid to bring the rest into orbit around Earth. The acceleration would be very gradual, the asteroid would have to be traveling in nearly the same orbit as Earth and the mass driver would cause it to either overtake Earth in its orbit or allow Earth to overtake in. If the asteroid is aimed properly, it can use the Moon as a gravitational assist to bleed off some of its velocity gravitationally so that it is captured into a temporary orbit around Earth. The mass driver would then slowly reduce the maximum radius of its orbit so that it will not be further perterbed and ejected by the Moon's gravity.
That seems to be the way to do it. I mean looking at the asteroids and examining the material is one thing, exploiting them is another. We would have to select the right asteroids of course, the ones with the right orbits that are the easiest to manuever into a capture orbit, and the ones that are made of the right materials so that we can properly exploit them once they are captured. We sort of need our own "Phobos" and "Deimos" Those moons are somewhat large and beyond our capability to maneuver, but perhaps something about 500 feet in diameter, a slight impulse might be enough to get it into a capture orbit, and it might be worth the expense of all those Ares V rockets to deliver the mass driver to that location.
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A 500 footer asteroid sounds more feasible and glad you're being realistic there, but I doubt the realism for a mass driver for two reasons:
1) One's never been built or used, certainly not in space and not on Earth.
2) Most asteroids are not heavy metals, and likewise material not magnetic.
Those are the achilles heal of the much-vaunted mass driver.
Still not a bad idea, the NEO...at least to a degree. It'd be an extensive project and, for safety and international reasons, likely require 30 years to organize and then implement. Ares tech might be able to do it if a stradegy can loft several boosters to the asteroid.
One last problem...after all this effort...what are we going to use this asteroid for? Strike out the Phobos-referenced-fuel idea...our neighboring NEOs are virtually all stony: little metal and no carbon-water resources.
Whatever purpose it'd serve...I wouldn't recommend putting it any closer than geosyncronus - lord forbid a terrorist gaining control of the asteroid's nagivation systems...
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A 500 footer asteroid sounds more feasible and glad you're being realistic there, but I doubt the realism for a mass driver for two reasons:
1) One's never been built or used, certainly not in space and not on Earth.
2) Most asteroids are not heavy metals, and likewise material not magnetic.Those are the achilles heal of the much-vaunted mass driver.
Still not a bad idea, the NEO...at least to a degree. It'd be an extensive project and, for safety and international reasons, likely require 30 years to organize and then implement. Ares tech might be able to do it if a stradegy can loft several boosters to the asteroid.
One last problem...after all this effort...what are we going to use this asteroid for? Strike out the Phobos-referenced-fuel idea...our neighboring NEOs are virtually all stony: little metal and no carbon-water resources.
Whatever purpose it'd serve...I wouldn't recommend putting it any closer than geosyncronus - lord forbid a terrorist gaining control of the asteroid's nagivation systems...
Mass drivers accelerate magnetic buckets containing non-magnetic material, decellerating the buckets and letting the rocks fly.
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Very bad idea. According to the JPL NEO database, there are 29 objects with period +/- 1% of Earth's orbital period, 275 objects within 10%. However, moving any object into Earth orbit raises the serious risk of impacting the Earth. It's better to mine in place and transport the extracted material.
As an analogy, I saw a documentary about a gold mine in Brazil. They mined using hand shovels and buckets. The material was mud, gumbo. Despite the primative tools, they moved an entire small moutain and created a hole as large as the mountain was. Modern open pit mines can move a mountain of rock, also creating a hole as large as the mountain, but they do it one truck load at a time. That's the trick, one truck load at a time. You don't move the entire mine into Earth orbit.
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Several Ares V rockets don't have the power to push an asteroid of any significant size around in space, because of the mass of those asteroids to the thrust of those buster. If you wanted to go out there with a few fission powered engines or better yet, fusion powered engines, then you would have enough power to push those asteroids around where you want them. But, you try to do that same trick by using Ares V rockets instead of those nuclear rockets that have a whole lot more power that they can generate, then your asking for trouble. One mistake and you could send that asteroid earthward and you would not have enough power in those engines to correct your mistake.
Larry,
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Very bad idea. According to the JPL NEO database, there are 29 objects with period +/- 1% of Earth's orbital period, 275 objects within 10%. However, moving any object into Earth orbit raises the serious risk of impacting the Earth. It's better to mine in place and transport the extracted material.
As an analogy, I saw a documentary about a gold mine in Brazil. They mined using hand shovels and buckets. The material was mud, gumbo. Despite the primative tools, they moved an entire small moutain and created a hole as large as the mountain was. Modern open pit mines can move a mountain of rock, also creating a hole as large as the mountain, but they do it one truck load at a time. That's the trick, one truck load at a time. You don't move the entire mine into Earth orbit.
Tell me, did you ever hit the bullseye of a target by shooting a gun in a random direction blind-folded?
The chance of a random accident altering an asteroid's trajectory to a collision course with Earth is approximately the same as the asteroid being on a collision with Earth initially. The asteroids are already in random ornits more or less, and they get nudged all the time by planet's gravity and by impacts with other asteroids. Do you really think that anything humans do by mistake is going to set an asteroid on a collision course with Earth, or that the chances of say Mars doing it would be the same. An NEO can be perterbed by Mars' gravity at any time such that it would be set on a collision course with Earth, I don't see why you think that humans should have a necessarily greater chance of doing it than Mars would. These asteroids cross Earth's orbit all the time, and its just a matter of time before they all eventually hit or are ejected from the solar system. I think putting an asteroid in a stable orbit around Earth eliminates the chance of an impact. Whereas before both are in seperate orbits around the sun with the chance of the asteroid hitting Earth, but if in a circular orbit around Earth at above a minimum threshold altitude the chances of an impact are reduce to effectively zero. I think its easier to support an asteroid mining operation if that asteroid is within teleoperative distance of Earth. Miners can come and go in a matter of days, they can be evacuated to a hospital should any experience any medical emergency, they only have to deorbit and reenter the atmosphere, however an asteroid miner operating at an asteroid in a seperate solar orbit around the sun has no recourse should he have a heart attack or other such emergency, as the laws of orbital mechanics are inflexible and only allow travel back and forth at specific launch windows, that open and close, and the travel time is on the order of a few months, while a capsule in geosynchronius orbit can deorbit within a day. I think it is safer for the miners to operate within the vicintity of Earth. Setting up operations to move the asteroid into an orbit around Earth is going to take fewer workers than actually mining the asteroid and exploiting it, thus you'd be exposing more miners to tha hazards of interplanetary space and its remoteness from Earth by mining the asteroid in place, and as their are only a few oppotunities to send the ore back with mining in place, while in orbit around Earth, the window is open continuously.
I think any mining company would agree that the ability to extrac ore contiously is more economical, that having to gather all the ore in one place on a big freighter as it waits for the window to open up to send it to where its needed.
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Several Ares V rockets don't have the power to push an asteroid of any significant size around in space, because of the mass of those asteroids to the thrust of those buster. If you wanted to go out there with a few fission powered engines or better yet, fusion powered engines, then you would have enough power to push those asteroids around where you want them. But, you try to do that same trick by using Ares V rockets instead of those nuclear rockets that have a whole lot more power that they can generate, then your asking for trouble. One mistake and you could send that asteroid earthward and you would not have enough power in those engines to correct your mistake.
Larry,
You really can't make a generalized statement about all NEO asteroids as the range from a few miles wide to down to the size of you fist, the smaller ones being of course more numerous. There are asteroids that exist that we could capture with today's technology, if you have in-situ fuel production you could even mount a conventional rocket engine on an asteroid and locally produce rocket fuel from the asteroid's material. In the case of chemical rockets, the crucial factor is whether the right material for rocket fuel production exists on that asteroid. So long as you can keep supplying rocket fuel and maintian the engine for a long enough burn, you can move an asteroid. For NEOs solar power is sufficient for the manufacture or rocket fuel. The necessary change in velocity to orbit Earth is small compared to the change in velocity for the space shi to get there from Earth's surface. I think a really useful amount of material can be brought to Earth orbit by asteroid capture, an amount that would dwarf the mass that can be brought up from Earth's surface. Chemical rocket engines aren't very efficient, but with todays technology, we could bring an asteroid into orbit around Earth with the mass of an Islan One colony, and that would be easier than flinging lunar rocks to L5 with a mass driver.
Perhaps chemical rockets are the way to move asteroids in the short term, we just have to make sure we don't have to bring our own fuel to move them. Borrowing Zubrins terminology, you live off the land.
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Right; and NASA has never missed. Mars Polar Lander and Mars Climate Orbiter operated perfectly. Genesis arrived perfectly and the parachute opened, helicopters intended to catch the aeroshell by its parachute functioned perfectly. NOT!
First, moving something as big as an asteroid required every trick known to man. That means orbital capture would require aerocapture. Propulsive capture cannot be done slowly, as the asteroid would accelerate as it falls into Earth's gravity well, you have to slow to orbital speed before it shoots out. That would require rediculously large rocket engines. On the other hand, aerocapture means you move a rough, irregular rock with centre of gravity off-centre from its mass, hope chunks don't break off as it skims the atmosphere, and hope the Earth's atmosphere doesn't expand from a sudden solar flare. There are too many variables, too many things you don't control, too many chances for failure.
You can aerocapture a 3 tonne capsule, or even a 104 tonne spacecraft, but a one billion tonne asteroid would cause too much damage if it were to impact Earth. For useful mining targets, one billion tonnes is a small one.
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I really don't know orbital mechanics, so I may be offering a useless suggestion here, but...
What about bringing a rock into Lunar orbit? Way closer than an NEO's natural orbital path, and further away from Earth than bringing it into Earth's orbit directly. Might give you more margin for error, but might not. Like I said, I don't know orbital mechanics. Anyone have a clue if Lunar orbit would make a difference in this scenario?
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I really don't know orbital mechanics, so I may be offering a useless suggestion here, but...
What about bringing a rock into Lunar orbit? Way closer than an NEO's natural orbital path, and further away from Earth than bringing it into Earth's orbit directly. Might give you more margin for error, but might not. Like I said, I don't know orbital mechanics. Anyone have a clue if Lunar orbit would make a difference in this scenario?
Actually it is exactly in significant interactions with the Earth-Moon system that the possibility of error arises (the 3-body solutions have regions of chaos where the uncertainty can not be reduced, even in principle).
The L4 and L5 points are probably more interesting for this purpose ...
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Actually it is exactly in significant interactions with the Earth-Moon system that the possibility of error arises (the 3-body solutions have regions of chaos where the uncertainty can not be reduced, even in principle).
The L4 and L5 points are probably more interesting for this purpose
Yes. And this is why there are no moons of moons anywhere in the solar system. Lunar orbit is even more unstable because of mascons - areas of mass concentration on the Moon that perturb the gravitational field.
Both L4 and L5 are unstable, keeping an object there would require energy. However it would require a lot less energy to move an object into orbit around these points than Lunar or Earth orbit.
Ok, so at enormous expense and effort a megaton of rock is moved to L5, what next?
(correction: L4 & L5 are stable)
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Thanks, noosfractal and cIclops, for the info.
More questions on my part: How does the delta-V requirement for L4 or L5 compare with the requirement for getting to the moon? What if you just hurl raw ore into Earth orbit instead of the whole asteroid? It wouldn't have to be a completely passive flight either, you could have a mass driver, a control assembly, and the pile of ore you wanted to sell to someone. I'm picturing the 21st century equivalent of guys poling logs down rivers to the mill.
It's an incomplete analogy, of course. It would be almost certainly automated, and you don't have the friendly river flow to give you free velocity.
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How does the delta-V requirement for L4 or L5 compare with the requirement for getting to the moon? What if you just hurl raw ore into Earth orbit instead of the whole asteroid? It wouldn't have to be a completely passive flight either, you could have a mass driver, a control assembly, and the pile of ore you wanted to sell to someone. I'm picturing the 21st century equivalent of guys poling logs down rivers to the mill.
Obviously it depends on the orbit of the asteroid. All asteroids are orbiting the Sun, some NEO's are interesting because their orbits are similar to the Earth and the delta-V is small. L4 and L5 are points in a two body system, so there are two sets of these, one in the Sun-Earth system (SE) and one in the Earth-Moon system (EM). SE-L4/5 requires the least energy to reach because these points are in the same Solar orbit as the Earth itself. EM-L4/5 requires entering Earth orbit, that requires much more delta-V.
There are a few asteroids that can be reached with a delta-V of about 5 km/sec from LEO, compared with a delta-V of 4 kms/sec to reach SE-L4/5 ... in other words these asteroids would need about 1km/sec change in velocity to be moved into orbits at SE-L4/5. The energy is proportional to mass times the delta-V squared, for a megaton asteroid that's a LOT of energy.
Yes it makes much more sense to bring smaller pieces of the asteroid to L4 or LEO, and yes a mass driver could do this. However imagine the cost of installing such a device on an asteroid that could also "collect" these pieces. Then what would you do with them? An industrial smelter in LEO? Iron ore isn't needed in LEO, spacecraft don't contain much iron or metal ores, they use complex alloys and composites. This would need a whole industrial complex. Until huge quantities of such materials are needed, it simply won't make any economic sense to manufacture these materials in space.
Having said that, what would be useful in LEO or even at a nearby asteroid is water ice - forget the logs, look at the river!
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I was unclear, I was intending:
How does the delta V requirement for getting to L4,5 from the Earth compare to getting to the moon from the Earth?
I can look at an orbital diagram and see how far away they are, but what does that mean from an energetics point of view?
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See diagram at right hand side for Earth-Moon Delta-v
SE-L4/L5 should be stable due to Coriolis force (see correction above). Transfers from orbits around SE Lagrange points can be made with minimal delta-v to EM Lagrange points, but they require a long time.
The energy required to reach any of the Lagrange points should be equal to that needed to escape Earth's gravity. That's equal to the energy required to change the object's velocity by about 11 kms/sec relative to the surface. Reaching the surface of the Moon at zero velocity requires more energy and therefore more delta-v, as it has to be decelerated to counter the Moon's gravity.
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