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Sailing Through Space, On A Starboard Tack

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Sailing Through Space, On A Starboard Tack


Sailing Through Space, On A Starboard Tack

Sailing Through Space, On A Starboard Tack

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  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

In the vacuum of space, photons — not wind — may someday fill the sails of lightweight spacecraft, propelling them without need for engines or fuel. Louis Friedman, executive director of The Planetary Society, discusses the society's plans for a sailing spaceship prototype.


You're listening to SCIENCE FRIDAY from NPR News. I'm Ira Flatow.

Next up, a little bit of back to the future and that would be sailing through space as opposed to crashing into the moon. You know that out in space there is no air and there is no wind. But back in 1609, before we knew any of that, Johannes Kepler wrote a letter to Galileo and in it, he predicted that someday maybe, it would be possible to design ships and sails, quote, adapted to the breezes of heaven" and they might transport people around the solar system.

Well, in the last 400 years, we figured out what those breezes are and how we could use them to push a sail through space. But we've yet to make the first flight with any sort of sailing spacecraft. Well, that might change soon if my next guest has his way. Lou Friedman is executive director of the Planetary Society of Pasadena, California.

Welcome back to SCIENCE FRIDAY, Dr. Friedman.

Dr. LOUIS FRIEDMAN (Executive Director, Planetary Society, Pasadena, California): Well, nice to be here. Hello.

FLATOW: Hello. Tell us about the sailing spaceship, a spaceship with a sail on it.

Dr. FRIEDMAN: Yeah. Its a terrific idea. Its been around for awhile, actually since the 1920s, but now, were finally getting the means to do it. And its not solar wind. There is a wind

FLATOW: Mm-hmm.

Dr. FRIEDMAN: from the sun then thats protons and electrons, which are actually you just heard a little about. But they go at relatively low speeds. What the real way to do sailing is from light pressure, the photons, the pure energy of sunlight. And when they bounce off a highly reflective thin mirror that were going to have made of aluminized mylar, they will transfer their momentum to the sail and act as a continuous thrust. And by steering that sail, we can go inwards or outwards. And someday, its the only technology we know that will take us on interstellar flight.

FLATOW: Mm-hmm.

Dr. FRIEDMAN: And thats why were so excited about trying it now.

FLATOW: So theres enough power from just sunlight itself


FLATOW: to push the spaceship?

Dr. FRIEDMAN: Yes, thats right. Light its a little thrust that youll get. Its a low acceleration, but its continuously acting and itll build up speeds.

FLATOW: Right. And how far could you take this? I mean, this - youll lose sunlight quickly out there, dont you?

Dr. FRIEDMAN: Well, thats right. And for the first steps, we will use sunlight to fly in a near-Earth orbit, may be out at the interplanetary space, missions to Venus and Mars and even the asteroids could be done this way, but ultimately you would run out of sunlight. And even though you can build up enormous speeds going out of the solar system, when you start to go out of the solar system, youre going to want to use a laser power system, a laser light that can focus a light over long, long distances, interstellar distances, and thats the way someday

FLATOW: Mm-hmm.

Dr. FRIEDMAN: interstellar travel will happen or interstellar spacecraft will happen. Thats probably still 100 or 200 years in the future, though.

FLATOW: So you have a spaceship - sort of proof-of-concept idea?

Dr. FRIEDMAN: Yes. Were going to use a were going to marry two technologies. One, very small - called a nanosat - spacecraft that only weighs on the order of five kilograms - very, very small satellite. It would fit on your desktop. But its going to have a very large sail: five and a half meters. By five and a half meters in size - because thats what you want for a solar-sail spacecraft. If you want large areas to collect photons and you want small mass so that your acceleration is high. We tried this a few years ago with a more conventional spacecraft that weighed over 100 kilograms.

FLATOW: Mm-hmm.

Dr. FRIEDMAN: Unfortunately the rocket failed at that time.

FLATOW: I remember that. Yeah.

Dr. FRIEDMAN: But our acceleration even as we make this very much smaller spacecraft will be greater than anything thats ever been attempted.

FLATOW: And when we might see this being launched?

Dr. FRIEDMAN: Well, we hope to be ready for launch by the end of next year. One of the things thats really strange in working with nanosats and is exciting -in fact, the basic building block is called a cube set, you can buy them online is the hardware costs become relatively small and relatively easy to work with. And so were going to build this spacecraft very fast and hope to launch by the end of next year.

FLATOW: Mm-hmm. And who knows from there on it if that works, sailing is the future, if you want to go...

Dr. FRIEDMAN: Yes. So we have a three-step process. We have three missions. You can read more about it on our Web site at in which we actually do want to go out into interplanetary space on the third step.

FLATOW: Mm-hmm. Well, thank you very much and good luck to you, Lou.

Dr. FRIEDMAN: Okay. Well, thanks very much for your interest.

FLATOW: Youre welcome.

Lou Friedman, executive director of the Planetary Society in Pasadena, California.

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