Harpoon concept for removing space junk tested in orbit

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A harpoon, the second of three engineering experiments for capturing space junk, was successfully fired last week.

A British satellite released from the International Space Station last year has successfully demonstrated a harpoon that could be used on future missions to clean up space debris, officials announced Friday.

The harpoon fired out of the RemoveDebris spacecraft Feb. 8, striking a target plate extended from the satellite on a 4.9-foot (1.5-meter) boom. The experiment was one of the main objectives of the $17 million (15.2-million-euro) RemoveDebris mission, conceived as a testbed for technologies engineers hope will allow future satellites to tidy up busy orbital traffic lanes by collecting dead satellites and rockets and driving them back into Earth’s atmosphere to burn up.

In a dramatic video released by Surrey Satellite Technology Ltd., the harpoon is seen catapulting out of the RemoveDebris spacecraft at a velocity of about 45 mph — 20 meters per second — and spearing its target. A cable attached to the harpoon kept the device from flying off and becoming its own piece of space junk.

The first experiment was a test of a net, tested successfully in September. The last of the three experiments, scheduled in a month, will test a sail designed to slow the satellite’s speed so that it gets de-orbited quickly.

I have embedded the video of the harpoon test below the fold.



  • wayne

    “Velocitas Eradico”
    (loosely — “speed kills”)

    GI Joe- Retaliation-
    Nuclear Summit Scene

  • Jerry Greenwood

    When I read this earlier in the week my first thought was how could they have gotten close to a random piece of space junk? Then I learned they brought their own target and speared it from only a few feet away. What a let down. I see this portion of the project as just a stunt. It will be interesting to see how well the sail works.

  • Edward

    Jerry Greenwood wrote: “I see this portion of the project as just a stunt.

    Not a stunt; a test. There are a few patents for capturing and for deorbiting space debris, and these guys are testing some of the concepts.

    From the article: “Experts were eager to gauge how the harpoon moved in zero gravity, collecting data that was difficult to obtain during ground testing.

    They used something well known so that they can judge the results. A proof-of-concept test needs to be well controlled and understood, not random. The concepts that work will later be tried on a more arbitrary spacecraft.

    For any tests that do not perform as expected, they have known targets so that they can assess whether improvements are possible or whether the concept should be abandoned, at least for now.

  • Look at how the harpoon was moving in a straight line.

    It was aimed at a target supposedly moving in a curved, “orbital” path.

    How did the harpoon hit the target?

  • Edward

    How did the harpoon hit the target?

    1) On the scale of the test, relative to the size of the orbit, the target’s orbital path can be approximated as a straight line. It would be difficult to see the deviation from straight at this scale.

    2) The harpoon, once released, also was in its own curved orbit, but it appeared to fly straight, because the scale makes the curvature difficult to see in the short time frame of the test.

    3) The target had a size large enough so that deviations in trajectory still had an excellent chance to hit the target. As part of the test, the location of the harpoon’s hit, relative to the aim point, would be important in order to help determine the proper aiming of future harpoon tests and operations.

    The cable, or tether, attached to the harpoon may have had more effect on the trajectory than the curvatures of the orbits. Having a tether on operational harpoons would be necessary in order to drag target satellites into the atmosphere, so the tether’s affect on trajectory is important to know.

  • wayne

    Mr Flat-Earth Guy is just trying to bait you, all science is lost on him.
    (I’m surprised he didn’t bring up the dome….)

  • Edward

    You may be right, but his question seems reasonable, considering that such a test would be unreasonable on the ground where everything seems to fly straight. If they weren’t trying to do this in space, would they even need this test? As I noted before, the reason to test in space was explained in a line from the article: “Experts were eager to gauge how the harpoon moved in zero gravity, collecting data that was difficult to obtain during ground testing.

    Because everything seems to fly straight when used on the ground, Jerry Greenwood thought that this was only a stunt. Instead, in space things often behave in unexpected ways, which is why we test there.

    The Gemini program learned, the hard way, several important lessons. Gemini spacecraft were the first U.S. manned craft that could maneuver in space and change their orbits (other than the reentry retrograde rocket burn). The first time that they tried to go back to meet up with the launch rocket, they discovered that orbital mechanics can be counterintuitive:

    In a spacewalk in which Gene Cernan was intended to perform what seemed during preparations on the ground to be easy and relatively quick, the reality showed that it can be difficult to do work in space outside of the spacecraft:
    The lack of hand and foot holds also made him unable to gain any leverage, which made it hard to turn valves or even to perform any basic movements. While making the connections, Cernan became very tired. During this portion of the EVA, his pulse soared to about 180 beats per minute; the flight surgeon on the ground feared he would lose consciousness. As he sweated, his visor began to fog. … In future Gemini EVAs, the work loads of the astronauts were reduced, but it was clear that during lunar exploration, workloads could be significant and changes were made to ensure that the Apollo EVA suit would be water cooled.

    Also, as a result of Cernan’s experience, future EVA missions were tested and practiced in a neutral buoyancy pool in order to find and prevent such difficulties before flight.

    Whether or not the Earth is flat, space is a very different place.

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