Slash Boxes

SoylentNews is people

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".

Original Submission

This discussion has been archived. No new comments can be posted.
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
  • (Score: 2) by draconx on Thursday September 03 2015, @06:50PM

    by draconx (4649) on Thursday September 03 2015, @06:50PM (#231897)

    Yeah, my first thought is that there is too much delta-v for a grappling hook and cable to be practical.

    Well, what matters are the magnitude of the forces involved (acceleration), the tensile strength of the cable, and the mass of the whole assembly (compared to a more conventional thruster). As well secondary issues, like how reliable the system is. The idea in the article is that you fly by the comet, fire an anchor into it, and the cable unwinds as the spacecraft flies by the comet. This powers the spacecraft via a generator, and simultaneously slows the craft (relative to the comet).

    For the concept to be useful, I imagine that the cable would be unwinding for the entire usable life of the spacecraft. Which means it needs to be unimaginably long, low mass, and have high tensile strength. The article suggests carbon nanotubes, which of course make all sorts of cool things possible except that, well, nobody has ever actually managed to build a cable out of the stuff.

    For reference, 10 km/s delta-v is appox. the same as the delta-v budget of Dawn (after separation from its launch vehicle), which carried 425kg of Xenon propellant.

    Starting Score:    1  point
    Karma-Bonus Modifier   +1  

    Total Score:   2