But it's actually a pretty complicated task for one spacecraft to "grab" another, requiring special fixtures to grasp specific objects. And making repairs to the ISS or to satellites compounds the difficulty.
But now a Colorado-based company has developed a new kind of robotic arm it calls a "sticky boom" that uses electroadhesion to stick to any object by inducing electrostatic charges in the object of interest, whether it be made of plastic, metal, glass, or rock (like, say, an asteroid).
And it doesn't need to be designed especially to grasp a given object. That kind of robust flexibility makes Altius Space Machines' "sticky boom" highly attractive for future space machines.
So, what is this mysterious thing called electroadhesion? It exploits the same difference in charge that gives rise to static electricity.
We experience this every time we drag our feet on the carpet and then touch a conducting surface, or rub a balloon on our hair and then marvel as it magically "sticks" to a wall.
The shuffling (or rubbing) causes our bodies to pick up extra negatively charged electrons, making it "unstable" -- that is, the object is just dying to get rid of its excess negative charge, and thus will be attracted to objects with a positive charge.
With the balloon example, the electrically charged particles are attracted to the more stable particles in the wall, causing it to "stick" to the surface -- at least until enough charged particles transfer to the wall so that the balloon falls to the ground.
The effect is more immediate when we shuffle our feet on the carpet and then touch a metal doorknob. The electrons "jump" across the small gap from our fingers to the knob, and we experience a tiny electric shock.
The electroadhesion technology used in the "sticky boom" is based on work by SRI International to develop wall-climbing robots for military and rescue operations.
Those robots employ a similar unique clamping technology -- a high-tech version of rubbing a balloon on your head to get it to stick to the wall.
Specifically, the robot has a battery power supply connected to pads on the bottom of the robot.
This enables the operator to induce electrostatic charges so that the robot "sticks" to whatever surface it is attempting to manoeuvre across -- even if that surface happens to be a vertical wall covered in dust.
Among other advantages, Altius claims that its sticky boom would enable "just-in-time" supply deliveries to the ISS.
Smaller spacecraft carrying supplies wouldn't need their own docking systems; instead, the ISS crew could reel them in using the sticky boom.
Also, it would be easier to repair the ISS, or nearby satellites.
This capability has implications for the future commercial development of space, particularly when it comes to smaller launch vehicles and "nanosatellites" like the prototype microchip mini-satellites designed by Cornell University's Mason Peck.
Peck's tiny satellites nicknamed "Sprite" and measuring just one square inch launched with Endeavor back in May and are now attached to the international space station.
The chip satellites contain sensors, a microchip, and an antenna to transmit collected data about the chemistry of the solar wind and associated radiation and particle impacts.
Spacecraft outfitted with such a sticky boom could also grasp bits of space debris more easily to clear out our cluttered low-Earth orbit. This is a serious problem.
Earth is now surrounded by so much space junk that a leading expert on the issue has declared that it may soon become too dangerous to venture into low-Earth orbit through fear of having a manned spaceship punctured or a communications satellite trashed.
Altius claims it has already tested successfully a small-scale protype of the sticky boom under simulated space conditions -- namely, a parabolic aircraft flight and within a thermal vacuum chamber -- and has been talking with NASA about implementing the concept on future missions.
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