Bridging the Gap: Part III

A Discussion with Freeman Dyson

Going to another star is a terribly powerful idea, just as going to the Moon was originally. At some point in human history, there will be a leap across the great void not just to the nearest star but to any star that might be interesting to explore.

Renowned physicist, educator, and author Freeman Dyson joined Planetary Society Chairman of the Board Bruce Murray and Executive Director Louis Friedman at Society headquarters for an informal discussion about interstellar flight.

Their discussion dovetails to a proposal for sailing on solar wind. Nearly 400 years ago astronomer Johannes Kepler observed comet tails blown by a solar breeze and suggested that vessels might likewise navigate through space using appropriately fashioned sails. It is now widely recognized that sunlight does indeed produce a force which moves comet tails and a large, reflective sail could be a practical means of propelling a spacecraft. In fact, one concept explored by NASA centers is to develop an interstellar probe pushed along by sunlight reflected from an ultra-thin sail. Nearly half a kilometer wide, the delicate solar sail would be unfurled in space. Continuous pressure from sunlight would ultimately accelerate the craft to speeds about five times higher than possible with conventional rockets — without requiring any fuel.

In collaboration with the Planetary Society, Cosmos Studios, has funded the first solar sail. which had its initial trial launch from an intercontinental ballistic missile [ICBM] on a Russian submarine in the Barents Sea. The launch unfortunately had a third-stage separation failure, which was a problem of the ICBM rather than the spacecraft. They are launching again. Solar sailing is a kind of technology which enables probes to move through space ten times faster than even the Voyager spacecraft,–38,000 miles an hour. To go ten times faster than that begins to get to a potentially practical rapid transit system for our local neighborhood in space, but also even to go to other stars.

Lou: So, what is your appraisal of the Cosmos 1 solar sail mission?

Freeman: I think it’s great that somebody finally started on this technology. The main thing is not to raise expectations too high. It’s important to get your feet wet and find out what the problems are. You’re certainly doing that.

Freeman Dyson, physicist, educator, author
Image Credit: Trustees of Dartmouth College

Lou: The vision of Cosmos 1 has been the fact that the technology, as we’ve been discussing, allows us to think about traveling to the stars, but it’s also technology that allows us think about traveling back and forth through the solar system.

Freeman: Oh, very much so. In fact, that, to me, is the most interesting part of solar sailing. It could become very cheap if the sails were produced in large quantity, and then solar sailing would be essentially open to everybody.

Bruce: We could park the sails in high Earth orbit, for example.

Freeman: Then you’d have your own little sailboat and go wherever you wanted.

Lou: What’s your biggest technological uncertainty about sailing?

Freeman: I would say it’s all a matter of operations. The physics is easy the problem is, how do you operate the system, where do you want to go, and what do you do when you get there?

Bruce: Freeman, in your book Disturbing the Universe, you had a section on solar sailing. Looking back at that, what would you say differently about solar sailing or space travel or whatever?

Freeman: I don’t remember what I said, but clearly progress has gone much slower than I expected. Yours is really the first serious effort, and that’s a pity. NASA has been systematically opposed to any advanced technology right from the start. That more or less remains true today.

Bruce: Are you optimistic that America’s, and therefore NASA’s, interest will be renewed in moving beyond Earth orbit?

Freeman: Maybe you have to get NASA out of the way first.

Bruce: That’s our strategy. If we can demonstrate a solar sail, even a primitive one, especially on a Russian nuclear submarine launch, NASA will be shamed into it. Also, the Europeans are beginning to look very seriously at the technology. That’s The Planetary Society’s job: to induce change, just as with the Mars rovers, when we got NASA seriously interested by demonstrating what you could do with them.

Russian submarine
The Cosmos 1 flights launch from this Russian submarine.
Credit: The Planetary Society ©.

Freeman: Well, I would say that the initiative has to come from outside NASA. Certainly it’ll happen one day, although it’s taken much longer than I expected.

Lou: I guess that brings us back to the somewhat discouraging view about the possibility of interstellar flight being hundreds of years in the future. So much will happen between then and now. What will happen in genetic engineering or human evolution? What will happen in robotic technology? To me, these things are fairly unimaginable. So, trying to superimpose these unimaginable developments on the imaginable evolution of a solar sail vehicle is where I lose it. If we were looking at only a hundred years of change, I’d feel a little better about grabbing on to it.

Bruce: I have one last point. We’ve been thinking about humans migrating, and adapting in some form, to other worlds in this solar system at least. There’s an alternative possibility: to stay here and send only sensors and surrogates elsewhere. I’m wondering, in the 30 to 40 years since you first began fantasizing about some of these things, how do you feel about this alternative vision?

Freeman: Well, I detest it. It’s quite possible that if we decide to go that way, I will become a rebel and go off in my little spaceship and leave everybody else behind. So, I hope we’ll all be rebels when the time comes.

Lou: So, you won’t be satisfied sitting in some room with a hologram of data pouring in?

Freeman: No. I will have lost any freedom that I may have had. It’s a matter of taste, of course, but I hope there will always be people who rebel against that kind of thing.

Bruce: But it’s so much easier to live here than elsewhere.

Lou: None of us, to quote John F. Kennedy, is "doing this because it’s easy, but because it’s difficult."

Related Web Pages

Freeman Dyson: Biography
Carl Sagan
Cosmo Solar Sail Project
Mars terraformation
Planetary Society