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posted by Fnord666 on Tuesday September 04 2018, @01:04PM   Printer-friendly
from the going-up! dept.

Japan is taking us one step closer to a space elevator.

Elon Musk may not believe in space elevators yet, but Japan is taking a step forward to realise the dream of travelling to space by elevators instead of the traditional rocket.

A team of researchers from Japan's Shizuoka University and other institutions will conduct the first test in space this month as part of a project to build a space elevator, Japan's The Mainichi reported last week. The space elevator essentially ferries people and cargo shipments in an elevator car travelling on a cable connecting Earth to a space station.

This test is the first exploring the movement of a container on a cable in space. Two ultra-small cubic satellites measuring 10 centimeters on each side connected by a steel cable about 10 metres long will be carried from Kagoshima's Tanegashima Space Center to the International Space Station on Sept. 11.

From there, the connected satellites will be launched and a motorised container acting as an elevator car will travel along the cable and have its journey recorded via a camera attached to the satellites.

The project's technical advisor, Japan's construction giant Obayashi Corporation, is also working on a similar project, though it previously said it expects to deliver a space elevator by 2050.

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  • (Score: 4, Interesting) by Immerman on Tuesday September 04 2018, @05:10PM

    by Immerman (3985) on Tuesday September 04 2018, @05:10PM (#730343)

    1) it's *far* more expensive.

    2) you still need the same millisecond coordination unless the entire wheel rim is completely uniform and passive so that you can dock literally anywhere ("claws" on your ship to grab onto the ring? Supermagnets capable of holding your ship against the potentially multi-G centripetal force?)

    3) even if the wheel rim is uniform, you still haven't dramatically improved the timing window in the challenge of passing through exactly the right piece of space at exactly the right moment. The top of the ring is traveling far in excess of orbital velocity, it's not like you can just drift close to it and grab it when handy - you've got to coordinate the lowest, fastest point of your very elliptical incoming orbit to reach the upper-wheel elevation at exactly the same moment as the top of the wheel is passing through that point. Get there a few seconds too soon and the wheel won't be there yet - too late, and it will have already passed.

    What a a "wheel" really gains you is a spatially continuous selection of rendezvous points, meaning you can launch from, and return to, anywhere on the skyhook's orbital path without having to wait until a tether is in the appropriate alignment for your desired region (very handy, and well worth having if you can afford it). The rendezvous timing still needs to be nearly perfect though, you just have a bit more leeway in the exact position. And at the speeds you're traveling for a reentry rendezvous, even a full burn of your rocket isn't going to allow for much in the way of last-minute corrections.

    My own preference to widen the rendezvous window is to use "docking harpoons" to buy a bit more leeway - as you approach a skyhook docking site you fire a harpoon at a "docking target" which securely grabs the harpoon and drags you along at the end of the attached tether (obviously your ship needs to be designed to support its weight on the harpoon tether). That buys you at least a few dozen meters of allowable imperfection, maybe even a few hundred, which means your timing can be off by at least a sizeable fraction of a second, and potentially several seconds, depending on the precise orbital dynamics of the skyhook.

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