Why does nasa want to capture an asteroid




















We could extract the water from the target rocks by bagging them in plastic and using solar heat to bake out the water resource. In this way, asteroid water could create fuel for space tugs travelling between low Earth orbit and higher geostationary orbit where most communications satellites sit. While the multiple goals of the Asteroid Redirect Mission provide exciting opportunities, there is perhaps the nagging question of risk.

If an objective of the mission is to demonstrate the deflection of near Earth asteroids, why deliberately push part of one onto an Earth return trajectory? Although it seems to have lost political backing for the time-being, the NASA Asteroid Redirect Mission represents an important proof of concept for asteroid capture and return.

Portsmouth Climate Festival — Portsmouth, Portsmouth. Edition: Available editions United Kingdom. Become an author Sign up as a reader Sign in. Asteroids come in many forms, from rubble piles barely held together by their own gravity to dense balls of iron and nickel.

Dimotakis said the asteroid to capture needs to be the consistency of dried mud. Finding the right asteroid to capture will not be easy, Dimotakis said. Because of the limited size and nudging or towing power of the capsule that will be sent to the asteroid, the rock itself cannot be more than 1, tons. What's more, it needs to be on a trajectory that would take it close to the Earth and moon even without a tow. The capture spacecraft, Dimotakis said, would not have enough power and fuel to dramatically change the direction of an asteroid of to 1, tons.

By far the largest concentration of asteroids in the solar system orbit in the main belt between Mars and Jupiter. Bolden and Dimotakis listed numerous reasons for undertaking the project, but emphasized three in particular.

Because asteroids are among the oldest objects in the solar system, Dimotakis said, bringing one to a place where it could be studied intensely would allow scientists to gain a much better understanding of what that early solar system was like.

He said having an asteroid nearby that could be constantly visited would likely lead to scientific breakthroughs. And if the long-term goal of American space exploration is to send astronauts to Mars—which President Obama has proposed for the s—then space program managers need achievable milestones to prepare for that mission. An asteroid orbiting the moon, or at the unique second LaGrange point near the moon where the gravitational pull of Earth and the moon are about equal, would provide such a destination.

It would also provide a use for the Orion capsule and Space Launch System now being developed by the agency. Although tons of material fall every day from space down onto Earth, most is in the form of dust or the fist-sized rocks that become "shooting stars. Then in February an 11,ton meteorite exploded 10 to 16 miles above the skies of the Russian city of Chelyabinsk.

The explosion, which was 20 to 30 times more powerful than the atomic bombs dropped on Hiroshima and Nagasaki, caused more than 1, injuries, mostly from broken glass. Video: Predicting Asteroid Impacts. A significantly larger asteroid passed by Earth only 16 hours later. That one flew by harmlessly, but further increased concern about the hazards of the many asteroids in our solar neighborhood and supported the case for giving greater attention to what is termed "planetary defense.

An additional reason given to support the asteroid retrieval project involves the fast-growing number of commercial space companies and projects. Several companies have proposed mining asteroids for the rare and valuable metals they are believed to carry, and having a potential mining site so close could quickly spur development.

All rights reserved. Additionally, the issue of asteroid hazards has taken on a greater urgency of late. The asteroid Apophis likely one of those LL chondrites contains enough materials to construct about five-gigawatt solar power satellites at 25, tons of steel and silicon each, plus Kalpana One style habitats for , 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. And we should not forget that placing an asteroid into a stable Earth orbit prevents it from colliding with the Earth.

So, how do we capture an asteroid? When a spaceship or asteroid passes close to a planet or large moon, its orbit is changed, sometimes dramatically.

More importantly, small changes in the position or timing of an existing close approach are enormously magnified. 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 m 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, colonists plus a dozen 5 gigawatt SPSs. Thus I view 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 actual Roche limit depends upon density, but is likely to be of the order of 20, kilometers for a rubble pile asteroid passing near the Earth, and perhaps 5, 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.

But even a lowly LL chondrite will work. The last consideration here is the opportunity for intercept missions. 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. This table presents some possible asteroid capture candidates as of APR, all brighter than 24th magnitude and expected to pass within 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 various tables, databases, and lists at the NASA web site are inconsistent, sometimes even 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. This process has extremely large error bars. In April of , radar imaging resolved the asteroid YU Previous estimates were that its diameter was meters and its mass 4Mt. The actual measurement revealed a diameter of meters and an estimated mass of 87Mt, a 22 fold mass increase.

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. It masses 27 million tons, roughly twelve times larger than the minimum useful capture size. But being more than 20 times as large as Apophis means a lot of fuel is required, so WN5 will have to wait for a later, poorer opportunity, probably with a robotic mission.

It makes frequent approaches, about every 11 years, with relatively close approaches in April of , , etc , and in November of , , 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. It is large enough to build 7, 5-Gigawatt Solar Power Satellites, or to house 2 million people in a 2 mile diameter habitat.

While it is difficult to capture, it should be worth the effort. 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 would provide ample fuel to capture those big asteroids a few decades later. But it seems that nothing is ever simple.

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. 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, ton mass dangling meters from the center of Apophis would be needed to apply the necessary delta-V over a 10 month period.



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