Thursday, July 7, 2011

Technologies for Asteroid Capture into Earth Orbit

The following is my presentation “Technologies for Asteroid Capture into Earth Orbit” given at the International Space Development Conference in Huntsville, Alabama, on May 19, 2011.

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The focus of this presentation is on a specific technical approach which enables us to capture an asteroid using essentially current technologies; the missions, tools, and complications of that approach; and then some asteroid selection criteria and a few specific asteroid capture opportunities.

Using the asteroid 99942 Apophis, I outline a possible capture mission, its requirements, and a timeline.

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So why capture an asteroid? The main reason is to gain convenient access to its resources. Even a relatively resource-poor low-iron, low-metal LL chondrite contains 20% iron, significant quantities of water and other volatiles in the form of minerals such as clays, and oxygen to burn.

The asteroid Apophis (likely one of those LL chondrites) contains enough materials to construct about 150 five-gigawatt solar power satellites at 25,000 tons of steel and silicon each, plus Kalpana One style habitats for 100,000 people, all shielded by the slag remaining after iron is smelted out of asteroid ore. The oxygen freed from iron compounds during smelting amounts to well over a million tons more than is needed for the habitats, valuable fuel mass for ion thrusters to move the habitats and solar power satellites into their chosen orbits and to spin them up.

Of course, a space habitat providing food, water, oxygen, fuel, construction supplies, gravity, radiation shielding, and skilled human workers situated above much of the Earth’s gravity well is an ideal platform from which to continue the exploration and exploitation of space.

And we should not forget that placing an asteroid into a stable Earth orbit prevents it from colliding with the Earth.

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So, how do we capture an asteroid? Even a tiny one masses millions of tons, and we don’t yet have the technologies to manhandle them and put them wherever we want. Luckily, we don’t have to. When a spaceship or asteroid passes close to a planet or large moon, its orbit is changed, sometimes dramatically.

In principle, the Earth can impart a delta-V of up to 60km/s to an asteroid in orbit around the Sun, although in practice the limits are a small fraction of this. More importantly, small changes in the position or timing of an existing close approach are enormously magnified.

We aren’t limited to the Earth, in that close encounters to other planets might be used to alter an asteroid such that it passes close to the Earth at a later time where its orbit can be further tuned by the Earth’ gravitational field.

If we can adjust the asteroid’s orbit such that it makes a subsequent close approach to the Moon with a relatively low velocity, the resulting slingshot can drop that asteroid into an Earth orbit. The Moon can (in principle) remove up to 2 km/s of velocity relative to the Earth, although less is easier.

A point I’d like to emphasize: In my opinion, gravitational slingshots are as much art as engineering, especially when considering the variations involved in multiple slingshots around one or more bodies. The people who dreamed up the Cassini and Messenger missions are both geniuses and artists, and I have every confidence that they can find suitable mission plans to capture any potentially hazardous asteroid into Earth orbit, although the missions may be very long and complex thanks to a shortage of appropriate close encounters and/or the need for significant changes to the asteroid’s orbital parameters.

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When selecting an asteroid for a potential capture, the most important consideration is simply the proximity of an asteroid’s orbit to a useful keyhole through which the orbital engineers can design a capture mission in a reasonable timeframe.

The second consideration is the size of the asteroid. Bigger is not better when a 1 kilometer asteroid masses fifty times as much as Apophis, and thus requires a fifty-fold increase in the product of mission time and fuel mass. On the other end, a small 120m LL asteroid massing 2 million tons (and relatively poor in useful metals and volatiles) still has sufficient materials to build a single small Kalpana One style habitat for 8,000 colonists plus a dozen 5 gigawatt SPSs. Thus I view 120 meters as the smallest asteroid worthy of (first) capture, since it is barely large enough to build a permanent habitat rotating at 3rpm for Earth-normal gravity and with adequate radiation and meteoroid shielding.

Another consideration is the V-infinity of the asteroid, because slower asteroids are easier to move a distance large enough to make a significant difference in the slingshot.

The potential magnitude of a gravity assist is also constrained by how close to the center of the Earth the asteroid passes – and I think it’s important to keep it out of the lithosphere. Also, for a rubble pile we don’t want to pass closer than the Roche limit or the asteroid may be torn apart by tidal effects, much as Jupiter’s tide tore the comet Shoemaker-Levy into 20 fragments. The actual Roche limit depends upon density, but is likely to be of the order of 20,000 kilometers for a rubble pile asteroid passing near the Earth, and perhaps 5,000 kilometers for the Moon.

One might think that the composition of an asteroid would be the number 1 criteria, but in reality most asteroids should be quite valuable (see Mining the Sky by John S. Lewis). A common carbonaceous chondrite might contain 25% nickel-iron mostly in the form of metal grains, 10% water, and several percent carbon plus everything else needed for life in space. But even a lowly LL chondrite will work.

The last consideration here is the opportunity for intercept missions. We need to modify an asteroid’s orbit when it is easy, some months or years before the targeted close approach. This is difficult for a high-inclination or long-period asteroid because it might only approach closely enough to the Earth for low-delta-V intercept missions once every ten or a hundred years. But an asteroid with a two-year period might present suitable launch windows every two years. Also, for asteroids with periods close to a year and with low inclinations, there may be two launch windows per year as the asteroid passes inside and then outside the Earth’s orbit.

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This table presents some possible asteroid capture candidates as of 25-APR-2011, all brighter than 24th magnitude and expected to pass within 120 Earth radii in the next 50 years. Some of these may be eliminated by further refinement of their orbital parameters, while others can likely be added as new asteroids are discovered, or as orbits are corrected for known ones.

The entries on this table were gleaned from the Near Earth Object Close Approach database. The various tables, databases, and lists at the NASA web site are inconsistent, sometimes even on the same page. For example, the orbit visualization tool often has significantly different closest approaches than the “close approach” data on the same page.

A side note: Many asteroids have only been observed over a few days, resulting in large uncertainties in their orbital parameters. The shapes, diameters, and masses of most asteroids are estimated, not known. Diameters are estimated from an asteroid’s brightness and distance. But we can’t measure the actual albedo, and observations at multiple wavelengths are used to judge the asteroid class, and from that a typical reflectivity, and from that a formula results in an estimate of the diameter, and assuming an average density, we calculate the mass. This process has extremely large error bars. In April of 2010, radar imaging resolved the asteroid YU55. Previous estimates were that its diameter was 140 meters and its mass 4Mt. The actual measurement revealed a diameter of 400 meters and an estimated mass of 87Mt, a 22 fold mass increase.

Let’s consider these asteroids.

Apophis is fairly well characterized, although it may not be an LL chondrite, and may therefore have a different albedo, diameter, and mass. As a candidate for Earth-orbit capture, it has the advantages of passing quite close, and relatively slowly, plus launch windows occur in Aprils and Octobers near close approaches, suitable for a 1, 1.5, 2, or 2.5 year mission. It masses 27 million tons, roughly twelve times larger than the minimum useful capture size.

2001 WN5 is a bit on the large side, but it may pass about halfway between the Earth and Moon in 2028 which offers an opportunity to adjust its subsequent Earth approaches in 2037 and 2046. But being more than 20 times as large as Apophis means a lot of fuel is required, so 2001 WN5 will have to wait for a later, poorer opportunity, probably with a robotic mission.

2005 YU55 is three times as massive as Apophis, and approaches Earth, Venus, and Mars, giving multiple possibilities for gravity assists. Next year it will pass about 20% closer than the Moon’s orbit, but it won’t be that close again for quite a while. It makes frequent approaches, about every 11 years, with relatively close approaches in April of 2021, 2032, 2043 (etc), and in November of 2022, 2033, 2044 (etc). We can likely tune one close approach to allow a closer approach 11 years later that can lead to a capture 11 years after that.

1999 AN10 is a large (50x Apophis), fast, and dangerous asteroid which will pass about as close as the Moon in 2027. It is large enough to build 7,500 5-Gigawatt Solar Power Satellites, or to house 2 million people in a 2 mile diameter habitat. Actually, we can solve Earth’s energy problem for the next thousand years AND build a habitat for one million people, with materials to spare. While it is difficult to capture, it should be worth the effort.

2009 WM1 is only half the size of Apophis, and should be easy to capture some fifty years from now at its next close approach.

Lastly, 1999 RQ36 is 7 times the size of Apophis and passes 1.2 Lunar distances from the Earth in 2060. It, too, won’t be easy to capture, but is also worth the effort.

I’d like to point out that every one of these asteroids were placed into their current orbits by a slingshot around the Earth, a fact clear at a glance at the orbital simulation on the NASA web site. One of the principles of orbital mechanics is that an orbiting body (in a 2-body system) will always return to the altitude and velocity vector of its last orbit change. Ignoring hyperbolic orbits, one near Earth pass means more, until the body collides with the Earth or is deflected away by another planet.

Note, too, that capturing Apophis in 2029 would provide ample fuel to capture those big asteroids a few decades later.

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But it seems that nothing is ever simple. Part of the problem is that we don’t really know much about asteroids. Many of them appear to be rubble piles, and in some cases these spin so rapidly that their shape is constrained by their spin, yielding flying-saucer shapes. Others are contact binaries which might be exceptionally awkward to manipulate. We have more options with solid bodies, but we can’t plan on that.

So how do we apply thrust? Two ways come to mind: dock and push, or use a gravity tractor to pull. Gravity tractors can only apply tiny amounts of thrust, but that might work, especially on longer missions. It would also help to dangle heavier components such as nuclear reactors and fuel as close as possible to the asteroid, with the thrusters some distance away so they can aim off to the side without much loss of thrust efficiency. But a 1,700 ton mass dangling 170 meters from the center of Apophis would be needed to apply the necessary delta-V over a 10 month period. Gravity tractors generally require very long missions.

We can dock with an asteroid and push against it in a traditional way, but there are complications due to microgravity and asteroid rotation. It is possible that a number of cables could be looped around the asteroid to hold the tugship securely in place. Even then, a spinning asteroid means that thrust can only be applied during a fraction of each rotation, wasting thrust and fuel to the extent that the applied thrust isn’t directed in the correct vector.

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Let’s consider a specific example. The asteroid Apophis will approach Earth to within 30,000 kilometers on April 13, 2029, significantly inside the orbits of our geostationary satellites. If we do nothing, the Earth’s gravity will slingshot Apophis into a new orbit as it deflects it by about 28 degrees and boosts its velocity by 3.04 km/s. The result of this is that Apophis changes from a 0.89 year period Aten class asteroid orbiting mostly inside the Earth’s orbit to an Apollo class asteroid with a 1.167 year period and an orbit mostly outside of the Earth’s. I should point out that we don’t yet know with any degree of certainty exactly what the resulting orbit will be, because tiny changes in the position of closest approach have a huge impact on the resulting orbit. The period I’m quoting here corresponds to the keyhole that targets an Earth impact in 2036.

My main point is that delaying Apophis’ arrival at the Earth’s orbit by changing its velocity by only 10 cm/s results in a 1.5 km/s reduction in delta-V - a velocity gain of a factor of 15,000. I chose that particular slingshot because it results in a semi-major axis of exactly 1 au, with a period of 1 year. I used a program named GravitySimulator by Tony Dunn to model several Apophis orbit variations, and simultaneously to gain a true appreciation of the art and genius needed to find useful orbits.

The Tisserand criterion indicates that it’s possible to change Apophis’ eccentricity to zero at the same time, although that would result in an inclination of about 10.5 degrees, and requires a much larger delta-V. In any case, what we really want is not a near-Earth orbit, but rather a subsequent low-speed slingshot around the Moon to remove excess velocity and drop the asteroid into Earth orbit. That may require some finesse and multiple slingshots, but I’m confident it can be done. Look at the success of Cassini, Messenger, and other missions that have relied on gravity assist slingshots to achieve what once was considered impossible for our current technology.

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We still need to give Apophis that 10 cm/s nudge. I don’t suggest abrupt changes from nuclear bombs or high-velocity impacts, partly because we need finesse to fine-tune the orbit, and that’s best done by the equivalent of titration. We need a tugship, a long-mission, highly fuel-efficient spacecraft to gradually move the asteroid into a new orbit.

Magnetoplasmadynamic or VASIMR thrusters are likely the best choice to apply delta-V, as their high exhaust velocities reduce the total fuel mass needed, they can generate significant levels of thrust, and they should be able to achieve sufficiently high reliability.

Of course, we need to push or pull the asteroid, which isn’t simple, partly because they are rotating, undoubtedly along an inconvenient axis. And they have enormous angular momentum which we can’t simply cancel. This means we’ll either have to dock – not land – at an appropriate location and thrust a fraction of the time, or use a gravity or magnetic tractor approach which might limit us to lower thrusts and longer missions.

Note that ion thrusters take copious amounts of energy. 25 megawatts can be generated by a 300 by 300 meter solar array, or by a single compact nuclear module available commercially. We do have a lot of experience with high-power nuclear modules in submarines and aircraft carriers, so that’s an option I personally lean toward, but politics may dictate a less proven approach. Also, working fluids and cooling grids need to be addressed for nuclear or for solar dynamic electric generation.

Given an appropriate power supply, we still need enough time and fuel to move an asteroid. So how much do we need?

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From our mission-time derived flight plan, we compute the needed delta-V, and conservation of momentum allows us to compute the needed momentum change and the product of fuel mass times exhaust velocity. The asteroid’s mass is a given, but we can choose to some extent our mission time, and thus the needed delta-V. Double the mission time, halve the delta-V.

Note that doubling the exhaust velocity quadruples the needed energy (100 times the energy is needed for 10x velocity for a given amount of fuel). But doubling Vex also halves the fuel mass required, so the net effect is doubling the required power for a given thrust duration. At a specific impulse of 5000, consuming 55 tons of fuel over a 10 month period requires 5 megawatts of continuous power.

With a lot of energy, we don’t need much fuel at all. These numbers are all well within our technological capabilities. Of course, additional fuel will be needed to deliver the tugship and its load of fuel to the asteroid, but again, the numbers are within our capabilities. We can do this.

However, remember that Apophis is rotating and we may only be able to apply thrust half of the time. This doubles the thrust and power required.

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I’m proposing a mission with two main phases and a three-year (or so) timeframe.

The first phase is to launch the necessary components and assemble them in orbit, some time in 2027.

The actual deep-space phase begins with a lunar slingshot for intercept injection in October of 2027, and docking with Apophis some 5 months later. This requires 3 km/s of delta-V, and about 15 tons of fuel.

We would grapple Apophis, and apply 400 Newtons of thrust (enough to deliver 1.0 cm/s/month of acceleration) for half of every 30-hour day. Ten months of thrust consumes 55 tons of fuel. Then there is a three-month coast until the slingshot.

The major slingshot must occur on April 13, 2029. The goal is to change Apophis’ orbit to achieve a lunar slingshot 1 year later to capture the asteroid into Earth orbit. Note that the initial thrust moves Apophis further from the Earth, and the subsequent lunar slingshot is necessarily even further out.

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I want to talk briefly about that tugship.

It must support an extended deep-space mission, providing everything the crew needs to thrive. My supplies estimate assumes ammonia provides hydrogen for carbon dioxide recycling, and food to be dehydrated.

My mission plan requires 55 tons of fuel to change the asteroid’s orbit, plus 15 tons for the intercept and docking, plus contingencies. I’d suggest at least 100 tons total, perhaps more. Note that if properly oriented, the fuel can provide significant radiation shielding during the trip to Apophis, and then the asteroid itself provides even more, especially if the crew quarters can be partially buried.

We need to apply 200 newtons of thrust continuously for 10 months, or double that for half of the time. We’d need to double the power as well, 10 megawatts total. A 200 meter square array of 25% efficient solar cells generates 12 megawatts, the extra needed since ion thrusters aren’t 100% efficient.

Lastly, we need some way to grab hold of the rotating asteroid. I suggest using 6 harpoons with 1-km lines launched around Apophis, the ends retrieved and securely tied to the tugship. This would function as an effective net and friction applies sufficient traction to apply thrust even at high angles of attack. We could break several of the lines and still hold on. Note that this is a good example of where people can easily accomplish a task which might be nearly impossible for an automated system.

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This project plan assumes a separate launch of a construction shack housing six or more workers for several months.

Their job is to assemble all of the components, as I’d expect at least 5 launches of 50+ tons each are required.

-Two launches for the solar panels and supporting structures – total 100 tons

-Two launches for the fuel and thruster assemblies – another 100 tons

-One launch for the tugship (crew quarters) itself

-The construction shack is a sixth launch, and the assembly crews, mission crew, and supplies are likely two more man-rated launches. Note I’m assuming the assembly crew is launched early, and the mission crew at the last minute, because the deep-space mission already requires a very long time. The number of people in each is an estimate, of course. While 6 workers may suffice to assemble the tugship during a two month project, double the people would simplify training, ease workloads, and provide significant redundancy.

-Likewise with the deep-space mission crew. Two people may be able to handle the workload, but that is cutting it close. I’d suggest four at a minimum, and six is better.

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Continued research tops the list of the several logical next steps we should take. NASA is ideally suited for several of these, and the continuing search for potentially hazardous asteroids identifies the same candidate asteroids as a search for potentially capturable ones.

We do need to address several legal issues, which pose a serious problem for Western civilization private enterprise. Key among this is the right to own and exploit objects in space. If a person or company does not have the right to exploit space-based resources, they can have no incentive to acquire them, and the future of humanity in space is effectively dead.

We must also address the liability of moving asteroids. Certainly this should be done with the utmost care and intense oversight tempered with some sense of practicality. For example, the adjustment to Apophis orbit that I propose appears to pass through the 2036 impact keyhole. Does that mean we must move the orbit out and around that keyhole, or simply that we use reliable, even redundant systems, and closely monitor to track the potential need for additional intervention? I’m afraid that science and logic may have little to do with the outcome of that discussion.

We need to design and build a tugship using thruster and power technologies available in an appropriate timeframe. Of course, that research is an excellent task for NASA’s Marshall Space Flight Center. I think the biggest challenge here might be in supporting deep-space, long-term missions with the human crews I believe are necessary to get the job done.

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The bottom line is that we CAN capture asteroids into Earth orbit, thanks to the amplification of delta-V due to gravitational slingshots.

There are several candidate asteroids today, and there will be more tomorrow. Also, I did not look for opportunities where the asteroid close approach was to Venus, or Mars, or Mercury, and there is every chance that good candidates exist although longer missions (and an extra slingshot or two) would be required.

The most important consideration to me is that capturing an asteroid such as Apophis places millions of tons of raw materials into Earth orbit where we need them to build solar power satellites, permanent orbiting habitats, and to advance humanity’s exploration and further exploitation of the vast resources of space.

Lastly, we should never forget that capturing a potentially hazardous asteroid converts a dangerous threat into a resource of immense value.

President Obama needs a grand goal for NASA and the nation in the next decades, one comparable to Kennedy’s “We choose to go to the moon in this decade.” I believe that capturing Apophis into Earth orbit is such a grand goal, with benefits to global energy and warming (via those solar power satellites), and to space exploration, and to permanent, self-sustaining habitats in space. And it removes a threat to the Earth.

If you agree that we need a space-faring humanity and that exploiting asteroids is key, if you agree that sending cheap solar energy to Earth simultaneously helps humanity and reduces global warming, if you agree that we should act to prevent asteroid impacts on the Earth, then please share the word. Follow this link (Project Apophis) and tell President Obama that he holds the key to the future of humanity in space, that capturing Apophis is feasible, affordable, solves many problems in a single step, and is a Grand Goal worthy of his – and this nation’s – focus. Thank you.

20 comments:

Dex said...

While I am supportive of human space flight, I think it would be worthwhile to evaluate closely the need for a crewed tug-mission and visibility of a robotic tug-mission.

Stephen D. Covey said...

The orbital slingshot model I used for the Apophis capture example had a significant flaw. Re-analysis using better tools and more recent data indicates that 95 cm/s of delta-V is needed instead of 10 cm/s, and that in 2030 Apophis approaches the Moon with too great a velocity for orbital capture in a single pass.

Alternative mission profiles are being explored that should work with an applied delta-V of around 1 m/s, although the mission duration and cost will increase.

michael Hanlon said...

I think some are making this too complicated a task. I feel there is a growing blurring of the tasks to identify earth crossing, excentric orbit objests with Neaar Earth co-orbital targets. Those second of targets should never be more than a year away after we are ready to go get it. The second mis thought I sense growing is that Lagrange points are gravity wells. They are the opposite. They are plateaues in the gravity wells of dual point systems where the pull toward either point is offset by the pull from the other. Think of the L pts as little balconies on the down slope of a roulette wheel.If a ball is dropped into the system and lands in one of the balconies, it doesn't move further into the well. but then it isn't without mass and momentum either even though it is apparently motionless in regard to the pit of the well. The task we need to perform is to move an object from one high in the well point (L4,5) down to one of the others (L1,2,3)It won't take much energy at all to push that oject off its balcony and sent it deeper into the well to the next lower balcony. It'll just take a precise nudge. The real energy requirement will be to impart the new vectors of direction and momentum to keep it on the balcony once it gets there. So, you don't need all the fuel and equipment at the start point, you need to dress up your reciever like a baseball catcher with all the gear needed.
Back to the first errant I mentioned. The task of moving an object from the EarthMoon/Sun L1,2,3 pts would be a lot. There are a lot of dVs to impart to do the nudge from those points. The L4,5 (60 degrees ahead and behind but in the same orbit as the EarthMoon are the best points to get an object from. you simply need to advance or retard it's orbital angular component to match the Earth's. There area few objects already just out and in from the EarthMoon but thase would be few and hard to locate (The Earthmoon system being an efficient orbital path clearing machine given a billion years to work its plowing). There are at least two other orbits unconnected to the EarthMoon which should hold good candidates for easy capture: The corkscrew orbit and the prograde/retrograde orbit. The first circles the EarthMoon system and corkscrews with us as we orbit the sun. The second is half the time coming toward us, swings around our syustem then is headed away from us. That orbit is a long term near approach situation and the likelyhood of having one on near approach when we finally get our gear together is unlikely. That leaves us with the L4,5 & Corkscrew objects to search for. In terms of energy to capture, the corkscrews, being closer, are the better choice. Look there500,000 to a 1,000,000 miles (a toruoidal area) for our candidate. But still watch the deep skies for the occasional eccentric orbit crosser for safety reasons.
So, find a nearby corkscrew orbit object, nudge it to the arthMoon L1 balcony and park it there to exploit.

QuantumG said...

Loved the presentation Stephen. I watched the second half today on the NSS youtube channel.

I notice your tug ship doesn't have any artificial gravity, and you don't mention creating any until they get back to Earth orbit. Perhaps by the late 2020s there will be some medical mitigation techniques for zero-g health issues but currently this is a show stopper for a 30+ month mission.

How feasible would you consider it to do mining/colony development on an asteroid in solar orbit, with just the solar power satellites and spaceships returned as products to Earth orbit? Such a "distant colony" strategy could be favorable for the larger asteroids.

Stephen D. Covey said...

QuantumG, you are right, 30+ months in zero G is a potentially serious problem. At the same time, the mission is complex enough I don't see how to handle it robotically.

Remote mining & manufacturing missions are not only possible, they will likely dominate in the the long run. But getting started, bootstrapping the process, is a different issue. The cost of sending a workforce in the thousands to a distant asteroid may be prohibitive, until we can build mining & manufacturing habitats in Earth orbit, populate them, and then migrate the entire structure out to where the asteroid resources are. But I don't see that happening until we run out of low hanging fruit (asteroids that may be captured into Earth orbits). It is also more likely that we'll send robotic missions to return bags of ore (with minimal processing) to earth orbit, at least until the space population grows significantly enough to provide a self-sustaining market.

MikeL said...

Hi Stephen,

I was at your ISDC talk and enjoyed it greatly. It's great to see you're still working on the process. It seems to me from what I've read that some of the uncertainties with the 2029 encounter may yet change the values of the delta v required to bring apophis into orbit. Hopefully we'll know more in 2013.

There's an elegance to the way this mission could fulfil Obama's "go to an asteroid" mission while having this second productive result. Good luck making it happen!

Stephen D. Covey said...

Thank you, MikeL.

We've always known that the reality of an Apophis capture mission would be different than my plan as described. It will certainly have a different size and mass (hopefully not too much larger), and its actual path will certainly be different from the current "nominal" path, but again not by too much.

I wanted to describe a mission that is feasible given what we know today, as a starting point for what could be an extremely important actual mission in the future.

Bootstrapping humanity's move into space is the most important step we can take into the future, and it's great that we could do it while (1) reducing global warming, (2) preventing an asteroid from slamming into the Earth, and (3) making a profit.

What's Obama waiting for?

michael Hanlon said...

Another reason for having a controlled mass at our disposal would be to also assist if needed in deflecting any other objects that might come our way. Stephen, I think you should updadte your list of purposes for having a captured asteroid around to include this defensive aspect of it. Whether its mass is used to divert by gravitation or actually smash into a rogue object would depend on the situation. But I'd rather have one at the disposal of future generations than leave them dependent on just a nuclear arsenal for the task.

Stephen D. Covey said...

Interesting idea, Michael. My first thought was negative - any mass small enough that we can readily sling it around is too small to have much effect. But then again, a small effect might be all we'd need. It sure beats not having a mass to sling around! And if parked near an unstable Lagrange point (L1 or L2 come to mind), we might be able to use a few slingshots to give us some free momentum and launch it out to where it's needed.

Yes, a very interesting idea.

michael Hanlon said...

Remember that any object that threatens us would most likely be on the same order of mass magnitude as the one we captured. So, a great gravitational effect could occur. If a planet sized object came at us, say goodbye. But, it would probably be on the order of an Appophis sized asteroid which could be dealt with by any of the objects you've identified. Cosmic Billiards anyone?

michael Hanlon said...

Slingshots! Remember that the Apollo 13 mission was changed from a Lunar orbit insertion to a slingshot aimed back at the Earth? That was the most beautiful Slingshot trajectory calculated and done on a die or else true deadline.

michael Hanlon said...

Two objects have come to be observed that may bear relevance to this effort. One is in the forward Trojan position (L4). The other isan Earth orbit companion that travels mostly with the Earth in a corkscrew orbit!. They are an order of magnitude different in size The L4 one, 2010_TK7, is quesstimated to be 300 meters in size. The more massive one is the corkscrew, 3753_Cruithne, estimated to be 3 kilometers in diameter and 1,3 x10^14kg! Quite massive and riding along on our highway with us and constantly changing lanes without a directional light.
I think Cruithne is too big to use for a capture target itself. Where its greatest resource may lie is as a gravity well which is near by! Not the Moon but still it gives us the potential to add more dVs to any equational re-orbiting attempt. It is also so massive that it may itself have object of a size we could manage to harvest in its Lagrange points! objects on the size of 2010 TK7. We should seriously spend a tremendous effort to map the vicinity of Cruithne to find harvest targets.
Now as to 2010 TK7. Hey, its already in a Lagrange point 60 degrees ahead of us (That equates to one sixth of a year or 60 days ahead, 300 days behind but a total of 365 days to and from) it could be used as a practice destination for a Mars mission! Steven's desire for a habitat could begin there. Anything built there would only take 60 days to drop back to Earth. If we have not one (Earth) nor two (Earth & Moon) but three rescue stations for any Mars mission, it makes it that much more safe to accomplish. We might start a Mars mission there, swing back at Cruithne, then the Earth and then the Moon to sling with loads of dVs to boost to Mars! Study of 2010 TK7 is a must too.Since it is in a type of stable null gravity field at the L4, it may, even with its weak gravity well, be the central object in a mini-system. We could harvest its orbitals for resources there and here!
Jus tsome encouraging outlooks I thought I'd pass along. (sorry I didn't spell check if there were any)

michael Hanlon said...

Another lost opportunity: 2005 YU55. Six years of knowledge that this object would be travesing within the range of the Moon's orbit and what did we get from the scientific money earners? "Slowly, get the cameras ready. Don't make any sudden moves, you might scare it?

michael Hanlon said...

Hey, I just became aware that the crew section of the Apollo Lunar Module, Snoopy, after separating from its launching base (which crahed into the moon) was separated from the main capsule, Charlie Brown, and the remaining booster fuel was fired off to set into a heliocentric orbit. Meaning it should be an easy go to practice approach and retrieve target for any asteroid program. With this object we know its material make-up so there'd be no surprises there. It weighs around ten tons. If it were captured and placed into Earth orbit, a shuttle could have returned it from orbit. But some other means of that could be devised (A special re-entry shell?) We keep missing the fly-bys, let's bring back a piece of history. The only remaining Lunar Module should be worth something (all th eothers were moon crashed after rendezvous with the main crew capsules)

michael Hanlon said...

That was from Apollo 10 (or X), sorry.

michael Hanlon said...

Whoa. A little more reading reveals that there are several third stages of the Apollo mission vehicles that were put into solar orbit. (Maybe there are Russian Boosters also?) The linked article at Wikipedia says there are 5 S-IVBs in heliocentric orbits making 6 total, possibly spaced at two months apart in Earth's year around the sun. Their empty weight was 20,000 lbs and their physical make up is also documented and might be targets which might not need Earth return.
Hmmm, a nice mission might be to get one, toss it back at earth then go to a second one and capture it for return. Or maybe even, after the second one, gather Snoopy and return both the S-IVB and Snoopy to prove handling of a broken asteroid.

michael Hanlon said...

A link to the Wikipedia S-IVB article:
http://en.wikipedia.org/wiki/S-IVB

Unknown said...

BRILLIANT!! The White House is considering a KISS proposal to do this RIGHT NOW!
IF you agree, you can go to:

http://wh.gov/Pkzq

and sign the petition to urge the Office of Science and Technology to give their robotic mission the green light.

michael Hanlon said...

This is about 2012 DA14 (That Mayan Thing):
Here is where I armchair quarterback what happened with That Mayan Thing. Before when talk of asteroid response was to blow them up or divert them, I prayed that wiser heads would realize that capturing such objects was the way to handle them. Now there are start up businesses planning just such ventures. That is in the private sector. Our Governments have failed us in this arena miserably. NASA, ESA, China and India, the space capable nations, never banded together to treat the occasion of 2012 DA14. This was a case where we could have tried our "bomb it to oblivion tactic". No, not when it was headed at us. But after it passed. There should have been a posse of instruments and devices to head it off after the pass. Once we knew it was gone by, we should have blown the hell out of it to: 1) make sure it never came back as anything more than a meteor; 2)analyzed the dust remains to determine its composition; 3)calibrate our armaments; and 4) tried to capture and return some of the material for study. A year was plenty of advance notice time to have organized off the shelf components for such a mission.

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