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posted by LaminatorX on Thursday September 03 2015, @05:05PM   Printer-friendly
from the freight-train-hopping-IN-SPAAAAAACE! dept.

Traveling around space can be hard and require a lot of fuel, which is part of the reason NASA has a spacecraft concept that would hitch a free ride on one of the many comets and asteroids speeding around our solar system at 22,000 miles per hour (on the slow end). Comet Hitchhiker, developed at NASA's Jet Propulsion Laboratory, would feature a reusable tether system to replace the need for propellant for entering orbit and landing on objects.

The spacecraft would first cast an extendable tether toward the object and attach itself using a harpoon attached to the tether. Next, it would reel out the tether while applying a brake that harvests energy while the spacecraft accelerates. This allows Comet Hitchhiker to accelerate and slowly match the speed of its ride, and keeping that slight tension on the line harvests energy that is stored on-board for later use, reeling itself down to the surface of the comet or asteroid. A comet hitchhiker spacecraft can obtain up to ~10 km/s of delta-V by using a carbon nanotube (CNT) tether, reaching the current orbital distance of Pluto (32.6 AU) in just 5.6 years.

Unfortunately rocket scientists apparently don't read SN, or they'd know from discussions last year that it simply won't work. It seems that the idea defies "basic orbital mechanics" and "makes no sense".

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  • (Score: 2) by zocalo on Friday September 04 2015, @06:30AM

    by zocalo (302) on Friday September 04 2015, @06:30AM (#232147)
    I was also wondering whether it might be possible to have multiple tether release points at different tensions, so instead of getting a single sudden wrench on the tether as it went taut you could have multiple smaller ones, or to try and have a system where the tension on the extending tether, and thus the amount of acceleration stress on the system, increases in proportion to the length of the extended tether so the acceleration takes place over time instead of at one point. That would probably mean more mass though, so we're back to the trade off of whether this system would save enough to make it worth doing vs. just boosting more propellent to orbit.
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  • (Score: 1, Informative) by Anonymous Coward on Friday September 04 2015, @07:02AM

    by Anonymous Coward on Friday September 04 2015, @07:02AM (#232152)

    That was the point of having a brake. Rather than the acceleration taking place at one point, you let the tether spool out, but apply enough brake force to the tether that the vehicle is also pulled along.

    For optimum results, the brake force needs to be matched so that when you reach the end of the tether, the velocity difference between the vehicle and tether reached zero at the end of the tether.