The staggering difficulty posed by interstellar flight pushes us to imagine alternatives to today’s technologies. Using conventional rocketry we’re forced to amass so much propellant that the craft we want to send seem impossible to build, even if we could afford the vast fuel bill. A jacked up rocket engine is, of course, nothing but an old technology pushed to its extreme imaginative limits. And you could sense the constraints in that vision at the recent Joint Propulsion Conference in Hartford (CT), discussed not only in these pages but also here by Ray Villard.
I mention Villard’s comments because while I focused on Robert Frisbee’s antimatter rocket concepts in my Centauri Dreams post, Ray tackles the much broader question of how we place technologies within the context of scientific progress. The news director for the Hubble Space Telescope, Villard is well versed in the rewards and challenges of spaceflight, but he’s nonplussed with some of the reaction to the Hartford conference, much of it focused on the apparent impossibility of interstellar flight. Are these prognostications of doom accurate or do they indicate, as he opines, a simple ‘failure of imagination’?
For extrapolating from today into tomorrow often leads to dead ends. If rocket science doesn’t work, one possibility is to change the paradigm, leaving the fuel behind in the Solar System, or harvesting it along the route. The first alternative evokes beamed propulsion concepts including laser- and particle beam-pushed sails. The latter reminds us of Robert Bussard’s interstellar ramjet, a concept that now seems impractical (such devices seem to generate enough drag to make them function better for braking than acceleration), but one which has never been entirely abandoned. And then, as Villard notes, there are star drives:
The idealized “star drive” uses fundamental properties of matter and space-time to create propulsive forces anywhere in space without the need for carrying fuel. The idea of somehow tapping energy from the vacuum of space may be a little less crazy now. That’s because astronomers have discovered that the universe is dominated by “dark energy” which is stretching the fabric of space at an ever-faster rate. This has rattled our confidence in knowing the true underpinnings of modern physics.
All of which is the reason we keep such a close eye on dark energy research in these pages, for if there is a force of nature that may lead to our re-writing the textbooks, this is it, and its potential uses in propulsion (assuming we advance to the point we can harness it) are mind boggling. We’re at the very edge of speculation here, but at the same time, much that we now take for granted was once equally imponderable.
My guess is that the first interstellar mission, which I assume will be a robotic science probe, will fly with technologies that are as hard for us to imagine as (this is Villard’s phrase) ‘a Roman archer trying to imagine a military laser cannon.’ Tibor Pacher, my erstwhile opponent in the interstellar bet on the Long Bets site, doubtless agrees, but he may think that potential breakthroughs are closer than I do, or he wouldn’t be putting his money behind an interstellar launch as early as 2025. The great unknown here is the pace of computer technology and the possibility of vastly accelerated change.
Because people can vote on Long Bets, I hope you’ll drop by to cast yours. So far the ballots are running 23 to 7 in my favor, but I’m quick to note that neither of us will be collecting any money on New Year’s Eve, 2025. That night I hope to meet with Tibor either in northern Germany or Budapest to open a bottle of Champagne as we toast the victor (Tibor, I lean toward Pol Roger, and I suspect you’ll be buying). The funds that have accumulated interest through the intervening years will go either to the Tau Zero Foundation or SOS-Kinderdorf International, both good causes aimed at enhancing humanity’s future.
In the midst of all this interstellar musing, in came an e-mail from the SETI League’s Paul Shuch, opining that the bet has already been won and, moreover, that Tibor is the victor! Let me quote Paul:
I would argue that the first interstellar missions have already launched, and that (with only a little imagination) they meet the conditions of the bet. They are not spacecraft, but rather streams of photons. Think about it: interstellar microwave transmissions probe other civilizations’ interest in dialog, and pass numerous stars, thus are “flyby probes” in a sense. They are transmitted specifically for the purpose of reaching other solar systems. They have been “launched” (transmitted) several times from Earth, which is clearly within the orbit of Neptune. Some have conveyed scientific information about Earth, which satisfies the condition that they “deliver data for at least one scientific measurement.” They travel at the speed of light, so within the 2,000 year mission duration, will reach stars within 2,000 LY of our own Sun. And they are widely supported by the public, as witness the large number of humans who have submitted messages to the various projects that beam them into space. So, congratulations Tibor, you win!
Remind me not to play poker with Paul, who in the following e-mail exchange added that his argument was a bit of a Kobayashi Maru — a more or less no-win situation, for those of you not familiar with Star Trek lore. The key word here is ‘deliver,’ for now that I read through our Long Bets terms, I see that the operative sentence is ‘As a minimum requirement for the mission the spacecraft shall be capable to deliver data for at least one scientific measurement.’ Now, slapping forehead with palm, I wish Tibor had written (and I had agreed to) ‘return’ instead of ‘deliver’ data! Although I’m not conceding, I do invite Paul to join us for Champagne in 2025, and maybe Ray Villard can join us as well.