Solar Sails: State of the Art 2010

Centauri Dreams readers know that I’m a great supporter of solar sailing as a technology that has interstellar ramifications as well as immediate practical value right here in the Solar System. What’s particularly appealing about the solar sail is that we’ve already shaken out many of the problems and are ready to begin testing sails in space, which is why it’s so frustrating to see NASA and ESA locked in to budgetary constraints that keep that vital next step from happening. NanoSail-D is one cheap way we might fly a sail soon, and so is The Planetary Society’s LightSail project, but as with so many aspects of the space program, we seem to be well behind earlier optimistic schedules.

In that environment, though, it’s important to keep the goal in front of us and to continue the work on solar sail theory. In June of 2007, the 1st International Symposium on Solar Sailing took place at Herrsching at Lake Ammersee, Bavaria. The 2nd in this symposium series is now scheduled for July 20-22 of this year at New York City College of Technology (City Tech) of the City University of New York. The venue is home to solar sail experts Greg Matloff and Roman Kezerashvili.

The focus in New York will be recent advances in solar sailing technologies and near-term solar sail missions. Particular attention is focused on hardware, enabling technologies, concepts, designs, dynamics, navigation, control, modeling and mission applications and programs. For more information, check the ISSS 2010 site, where you can register online. For those interested in submitting papers, abstracts are due May 15. The proceedings will be published to add to the substantial solar sail literature that continues to refine the concept.

As to The Planetary Society’s plans, LightSail-1 is to have four triangular sails constructed of 32 square meters of mylar, a configuration that will be placed 800 kilometers above the Earth to test the practicality of using sunlight as a means of propulsion. The Society talks about a launch before the end of 2010, but much depends upon the choice of launch vehicle — LightSail-1 will be flying as a secondary payload on either an American or a Russian launch. Assuming success, the next LightSail will carry a larger payload, with a third sail intended to fly on a multi-year mission that will create an early-warning station for geomagnetic storms triggered by events on the Sun.

The Planetary Society calls solar sailing “…the only known technology that might carry out practical interstellar flight, helping pave our way to the stars.” Although the language is stirring, I’ll have to disagree with the word ‘practical’ in that sentence given the times involved in a solar sail mission to a nearby star, and I’m sure fusion advocates would argue that by the time we develop laser or microwave beaming methods to boost sails to faster speeds, we’ll likely have fusion options as well.

But who can argue with the excitement of funding a solar sail mission with public and private contributions, bypassing government bureaucracies to move the state of the art forward? Meanwhile, we also have to keep an eye on Japan, where work continues on the IKAROS Project, a solar sail / ion engine hybrid whose first mission may fly this year. IKAROS (Interplanetary Kite-craft Accelerated by Radiation of the Sun) will use thin film solar cells on the 20-meter sail membrane to power up its ion engines, with a second, larger sail envisioned that would one day target Jupiter and the Trojan asteroids. All told, 2010 looks to be a significant year for solar sail technologies.