The Infobae article Japón inicia hoy el ambicioso proyecto de construir un ascensor espacial which translated from Spanish into English by Google says

Japan begins today the ambitious project to build a space elevator

and continues (likewise translated):

This test is the first that explores the movement of a container in a cable in space . In the experiment, two ultra-small cubic satellites, or "cubesats", will be released into space from the International Space Station (ISS).

They will be connected by a steel cable, where a small container, which acts as an elevator car, will move along the cable using its own motor. A camera connected to the satellites will record the movements of the container in space, according to the Japanese newspaper The Mainichi, citing authorities from the Japan Space Agency.

Each "cubesat" measures just under 10 centimeters on each side. The "cubesats" will be connected with a 10-meter steel cable so that the "elevator car" can move forward, according to the report.

The new Japanese project will be the first test to move a container similar to a car through a cable in space. If the experiment is successful, it could significantly increase the interest in the transport system of space elevators.

Question: How will the two cubesats establish and maintain a significant amount of tension in the cable strung between them, necessary for a realistic test? Will the vehicle moving along the cable cary its own power source (e.g. solar-photovoltaic, battery, wind-up spring) or will power be beamed by laser or electromagnetic radiation, or by conductors?


1 Answer 1


The cube-sat may easily maintain tension by flying in tandem and many formation flying missions have maintained a constant distance pretty well. Have a look at MAST(Multi-Application Survivable Tether) experiment.It's the most similar one I could find to this and while it did not work, you may find more information about how they designed the system."After deployment of the two CubeSats from the P-POD deployer, a timer will trigger a separation mechanism that will push the two nanosatellites apart. The upper CubeSat in Figure 3 will deploy a 1 kilometer long survivable Hoytether in between the two spacecraft. The lower CubeSat has a tether release mechanism that will enable it to separate from the tether upon command".Having one cube-sat tethered to the other and then launch the elevator object in between them is just the simple experiment in both missions but the tether length has been a challenge as so the 10 m proposed length seems more doable compared to previous missions. Another report I read just says that they intend to monitor elevator movement in space so it might be launched from one cube-sat and/ or have something similar to a counterweight system i.e., reeling in from one satellite to the other or similar to the MAST mission may have the elevator body crawling up and down the pseudo-taut tether. I'm however unsure about the elevator dynamics and have opined about the system. Hope you find it usefulenter image description here

  • $\begingroup$ How will it easily maintain tension by flying in tandem? If you can add an example of how at least one of the "many formation flying missions" maintain tension, that would be very helpful. There's certainly nothing wrong with including your opinions, but a reference to factual, supporting data is what makes Stack Exchange answers valuable (and well-received). Thanks! $\endgroup$
    – uhoh
    Commented Sep 18, 2018 at 6:48
  • $\begingroup$ Thanks for the edit! Stack exchange answers are best when they are written to be durable against broken links. Can you add a short description in your post as well? Did they use centrifugal force? Or thrusters? Or gravity gradient? Or something else? I know it's more work, but just saying "the answer is in this Wikipedia article" isn't really the best way to write a Stack Exchange answer post. $\endgroup$
    – uhoh
    Commented Sep 18, 2018 at 7:07
  • 1
    $\begingroup$ Hey, @uhoh. Thanks for the suggestions. I will learn and write better answers in the future. $\endgroup$
    – Rajath Pai
    Commented Sep 18, 2018 at 7:10
  • $\begingroup$ I don't see any attitude control systems in the "spool" part. That would mean the tension of the tether would draw it back quickly if it's not pulled away actively. Most likely it will be kept stretched by having the cubesat spin before separation, and create a "bolo" config. $\endgroup$
    – SF.
    Commented Sep 18, 2018 at 9:41
  • $\begingroup$ @SF. care to elaborate on it? I'd also liek to know what you're talking about. Also, MAST has details given but it was quite some years ago. This one is in 2018 and I have seen small ADCS systems for cubesats, so most likely it could also be there, albeit quite small and limited, perhaps $\endgroup$
    – Rajath Pai
    Commented Sep 18, 2018 at 13:56

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