How To Catch An Asteroid? Put A Bag Over It

Artistโ€™s conception of the asteroid-catcher with bag extended ready to grab a 7-meter space rock. Photo: Rick Sternbach / KISS

Why bother with an expensive, potentially dangerous manned mission to an asteroid when you can just tow it to lunar orbit and study it there? That’s the thinking behind a recent proposal by NASA’s Keck Institute for Space Studies (KISS). Researchers there have come up with a plan to launch a spacecraft to a small 7-meter (23-foot) near-Earth asteroid, capture it, de-spin it and then tow the garage-sized rock into lunar orbit, where it could be studied and mined for raw materials at a convenient distance from home. The Keck team points out that 842 lbs. of rocks were returned from the moon during the entire Apollo program, while this mission would bring an approximately 1.1 million-pound kilogram asteroid within Earth’s reach by the year 2026. Total price tag: about 2.6 billion.

The craft would be launched from an Atlas rocket and travel to its target using a solar electric propulsion system similar to the one that propelled NASA’s Dawn spacecraft to the asteroid Vesta and will soon carry it to Ceres. Upon arrival, the probe will first study and characterize the asteroid. Prior to capture, the craft would match the asteroid’s rotation, then, using inflatable arms, extend a large bag around the object. Cinching cables would close the bag. Once secured inside, the probe would fire its thrusters to de-spin both it and the asteroid, and then return to the vicinity of the moon and park itself in lunar orbit.

An example mission that would return near-Earth asteroid 2008 HU4 to lunar orbit. Credit: KISS

Expect the entire mission to take a decade to complete. Escaping the Earth’s gravity using ion propulsion requires between 1.6 to 2.2 years, then 2 years to reach the asteroid and 2-6 years to return depending upon the asteroid’s mass. If we were to start working out the details now, including building the spacecraft, we might just get our asteroid home by the projected 2026 time frame.

Top view of the spacecraft showing instruments and the capture mechanism before being released. Credit: KISS

Assuming that humans will be tooling around in lunar orbit by the 2020s, having a nearby asteroid opens up the possibility for mining. If we choose the right object, not only might there be precious metals available, but more importantly, water. Water can be used for shielding astronauts from dangerous solar radiation and cosmic rays on future missions to other planets. You can also chemically break down water into hydrogen and oxygen to make fuel for your spaceship.

It’s an intriguing idea that on the surface sounds almost as crazy as the sky-crane and tethers used to land the Curiosity rover on Mars last August. But hey, that was a carefully-engineered plan that worked flawlessly, and this may too. Read the full proposal HERE.

10 Responses

  1. lynn

    Hi Bob
    Well I don’t think this is one of the better idea’s out there it sounds a bit iffy (but then again anything to do with asteroid’s makes me a bit jumpy), but what would happen if this went all wrong and would the asteroid just stop spinning once it was caught and if it gets released again to be in lunar orbit how does it just start being in orbit again, also as they don’t have exact weight of a particular asteroid how can they be sure it doesn’t just fall straight through as I’m imagining say you had a paper bag and you put a big stone in it then it would fall straight to the bottom and rip the bag, could that happen with this sort of ‘bag’, this is a confusing one Bob hope you can help out. Thanks ๐Ÿ™‚

    1. astrobob

      The asteroid will be fixed inside the spacecraft, not floating around in the bag. To de-spin the space rock, the two must be anchored to each other. The ship-asteroid combo will insert itself into lunar orbit by using propellant the same way Dawn inserted itself into orbit around Vesta. Once in orbit, the ship-asteroid can orbit almost indefinitely. The Earth orbits the sun in a similar way. Plans are to keep the craft attached to the asteroid – at least for a time.

  2. Lynn

    Thanks Bob, I know it might of seemed a silly few question’s but I couldn’t get my head round it all, but I get it now ๐Ÿ™‚

  3. Giorgio Rizzarelli

    A clever mission because obviously an exercise to learn something about deviate asteroids, useful in the remote case we discovery one in trajectory with Earth. And as you say, crazy yet innovative just like sky crane!

    1. Bob Crozier

      Is the main point of this, though, just an exercise to see if we can do it? There does not seem to be any immediate economic benefit to trying to mine an asteroid. As valuable as water is in space, an asteroid would have to have a fair bit of useable water to make it worth such a project. I can see some benefit perhaps to trying something like this for the purpose of preparing for the potential need for “planetary defense” as they call it in that paper you linked for us. The biggest benefit would, in my estimation at least, not be in bringing the rock home, but simply in trying to grab it and stop it from spinning. If we could successfully do those two things, then we should be able to control it enough to redirect it. The benefit would be found in in being able to do that for another asteroid that was looking like it was going to crash into us. I assume that the bigger it is, the harder that becomes – more mass, more momentum.

      Are some of these asteroids actually rich enough in very precious metals or other materials to make a space mining operation potentially feasible?

      1. astrobob

        Asteroids have valuable materials like water and metals that can be used to shield astronauts from radiation, provide drinking water and build spaceships. If you build or outfit a ship in orbit, you don’t have the expense of hauling all your materials into space by launching rockets from Earth. Even if we didn’t mine the asteroid, having it always “near home” for study would be an incredible scientific and research benefit. The asteroid size and mass for this project – about 7 meters – would be too small to cause damage if it were to hit Earth. The ones that would make a difference would require an entirely different scale mission and probably a lot more time coming and going unless the propulsion method was changed. Some asteroids have lots of metal including valuable platinum. Tons of it!

    1. astrobob

      Hey Lynn,
      Constellations aren’t at specific distances. They’re composed of stars all at different distances from Earth – some close, some far. Camelopardalis, a northern sky constellation, is a connect-the-dots pattern of stars with a wide range of distances.

  4. Lynn

    Thanks Bob, it was because I had read about Nustar at NASA and they had said about a black hole that was found but it was in a galaxy inside the constellation camelopardalis but I didn’t realise the galaxy was millions of miles away, I think i’ve got this right lol ๐Ÿ™‚

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