Gentaro Nakata

Propellant-less Space Travel with Tethers: Swimming in Space using an Asteroid’s Gravity Gradient

April 3, 2021   /  

Name: Gentaro Nakata
Major: Physics
Advisors: Dr. John Lindner, Dr. Susan Lehman

For this thesis, we set off to investigate the practicality of space travel via tether that can contract and extend. Through this experiment, we used Mathematica to create simulations that showed how a tether spacecraft would react when the tether length would change. Firstly, we started with increasing the eccentricity of the orbit, and were eventually able to reach a point where the spacecraft escaped orbit. Next, we attempted to decrease the eccentricity and radius of the orbit, using a dynamic plot we were able to tell how the orbit radius would change over time, as we changed the tether length and were able to decrease the orbit radius. Through this experiment, we were able to demonstrate the possibility of propellant-less space travel with a tether, two masses separated by a variable length. By computer simulations, we show how to lengthen and shorten the tether to, swim in space using the gravity gradient of a nearby asteroid, moon, or planet.

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Gentaro will be online to field comments on April 16:
noon-2pm EDT (PST 9-11am, Africa/Europe: early evening) and 4-6 pm EDT (PST 1-3pm, Africa/Europe: late evening)

8 thoughts on “Propellant-less Space Travel with Tethers: Swimming in Space using an Asteroid’s Gravity Gradient”

  1. Swimming the gravity gradient sounds amazing! Can we understand the eccentricity pumping using forces (in addition to energies) like how we understand the spiraling inward or outward?

  2. Congratulations, Gentaro!

    For a job well done. Your work must be an excellent contribution to Space Science. Your abstract and poster are understandable even for non-experts, cool!

    I wish you Good Luck.

    Seifu Kebede Gurmessa (South Africa)

  3. Congratulations, Gentaro! I second Seifu’s comment – I actually learned a little through your explanation, and I have zero knowledge of this field. Very cool to imagine and define the possibilities.

  4. What a great project Gentaro! What tether length would you need in order to generate an macroscopically observable difference in orbital motion for a small spacecraft, as compared to not having a tether?

  5. Hello, Dr. Leary. A minimum length requirement wasn’t found due to the simulations being independent of length. However, the results on the Orbit Transfer showed a 0.1% change in the orbit size, so when the orbit is several thousand kilometers in radius, that makes a change of several kilometers. Repeating that process will give us large changes over time. So, as long as the tether length allows for the precise movement required, that length would work.

  6. Congratulations, Gentaro!

    Also as a non-expert scientist, I enjoyed how you tackled to show the possibility of bringing a very cool concept to a real world.

    Best wishes to you, wherever you go from here!

  7. Congrats, and as much as I don’t want to do space travel, you are doing great and impactful work.

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