April 14, 2016 Zimmerman/Batchelor podcast

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Tonight’s podcast is embedded below the fold. Lots of ULA discussion, as well as Russian court battles.



  • J Fincannon

    The interstellar ship sounds interesting but look at the paper upon which it is based.

    The gram level spacecraft (2.4 grams for the spacecraft) they propose to send to .25 the speed of light in ten minutes (what are the g forces?… 20,000 g’s!) and take 15 years to get to the nearest star must be powered by a 50-70 gigawatt laser array… which is a laser array that is 10 km by 10 km big! Not sure how many millions of lasers are needed to fill 100 square kilometers but their basic building block is 10 m by 10 m so it is at least 1 million more units than that! Even with Moore’s Law, this is expensive.

    I think there must be a better way.

  • Matt

    Hi Fincannon, I think the use of the two principles 1. high power beamer at ground (better as in orbit)+ reflecting propulsion unit (sail, mesh) 2. extreme miniaturization is the only practical way to send something to next stars in a scientist life-time. However, the use of a microwave system instead of laser may be better, because it is order of magnitudes cheaper. There are proposals of this kind around. A large rotating mesh of wires (sensors are at the knots) can be used instead of light reflecting surface for propulsion. A correct sizes mesh is sufficient to reflect the microwaves back. 10,000 g are not a problem for specific designed electronics.

  • Matt

    Hi Fincannon, here is a link, which refers to my comment made above: http://interstellar-flight.ru/design/base_e/starwisp.pdf

  • Edward

    I’m glad to see that someone has considered a much more reasonable acceleration rate (115G, although by my calculation he only needs 11G to reach 0.2C in a week) than reaching relativistic speed in less than an hour (2,000G) or in 10 minutes (10,000G).

    Unfortunately, the author, F. L. Forward, assumed that the temperature of the sail would be close to the 2.7K of deep space, during acceleration, when in fact the sail would be bathed in sunlight and would have a higher temperature than deep-space background temperature. Some amount of absorption of the microwave energy must be expected, which would further warm the structure.

    A basic problem with any solar sail is creating a structure that, under an accelerating force, does not fold up like an umbrella in a strong wind from the wrong direction. One proposal was to spin the sail, so that centrifugal forces keep it stretched out, relatively flat, while a modest accelerating force is applied (e.g. sunlight). For stronger accelerating forces, a strongback structure would be required, and the stronger the acceleration, the more massive the strongback.

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