More than 400 years ago, Greek astronomer Johannes Kepler looked up at the night sky and suggested that "ships and sails proper for heavenly air should be fashioned." And thus, Kepler was the first man to be disappointed by the prospect of solar sailing.
Two years ago, I stood in a Capitol Hill office building with Nathan Barnes, chief operating officer of L'Garde, the company NASA had contracted to build the largest solar sail ever.
Barnes was there with a piece of his impossibly-thin Sunjammer creation (which looks like aluminum foil but is much more expensive), which was to park itself between the Earth and the Sun and stay there, for perpetuity, powered only by solar wind. The Sunjammer, Barnes told me, was supposed to get much closer to the Sun than existing solar monitoring spacecraft and warn us if any solar flares were coming our way. Its 1,200 square foot sail was to be unlike anything that had ever been launched before, he promised.
All of that is in past tense because, just months before it was set to be launched, Sunjammer has been canceled, the latest in a long string of solar sail failures that raises the question: When are we going to figure these things out?
The allure of a solar sail is obvious: Basically, it uses the Sun's photons, bounced off a reflective surface, to very, very slowly push a spacecraft. Well, slowly at first, anyway: Unlike most spacecraft, a solar sail-powered one would be constantly accelerating, eventually allowing super fast speeds, without burning any fuel.
Kepler can be forgiven—from what I hear, it was quite difficult to propel anything into space in the 17th century. But, by now, NASA should have this figured out. Its first attempt was aborted in the 1980s (a solar sail was supposed to take a spacecraft close to Halley's Comet), then the Russians failed in 1993.
India's solar sails failed on two satellites in 1992 and 2003 (admittedly, they were side missions), and the Planetary Society's solar sail called Cosmos 1 didn't even make it into space thanks to a rocket failure.
If solar sails are so promising, why isn't anyone trying to turn them into a reality?
There are only two solar sails that can be looked at as successes: NASA's 2011 mission called NanoSail-D2 worked (after NanoSail-D failed in 2008)—for 240 days. The goal here, remember, is to create a spacecraft that requires no fuel and can go, in theory, forever.
Japan has also created a solar sail that's worked, and worked well: IKAROS has sailed past Venus and is currently still orbiting the Sun, though the spacecraft itself has to be shut down from time to time to preserve power.
IKAROS appears to be working just as Kepler and others would have hoped. The spacecraft continues to gain speed, meaning the dream of relatively quick interplanetary travel (within the solar system), at least, isn't completely out of the question. But it's hard to look at what's come before and after IKAROS and not be a little disappointed.
NASA sunk four years and $21 million on Sunjammer, and it's getting nothing out of it. Admittedly, $21 million isn't much in space terms. In Sunjammer's case, Barnes' company wasn't able to build a spacecraft that could go along with its massive sail, according to Space News.
Barnes said that it couldn't get NASA or any other company to build the spacecraft itself, which is troubling: If solar sails are so promising, why isn't anyone trying to turn them into a reality?
Next up? LightSail-1, another project from the Planetary Society, which is supposed to launch sometime in 2016. That sail, which is citizen-funded, reportedly just passed an important benchmark and is still on schedule to launch aboard a SpaceX rocket. There's reason for optimism, the society says that if not for the doomed Russian rocket nearly a decade ago, Cosmos-1 would have worked out just fine.
But, that said, I wouldn't necessarily hold your breath if you're hoping for a smashing success—these things seem borderline cursed at this point.