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International Experts Meet at City Tech to Discuss Advances in Solar Propulsion of Spacecraft

Solar sail scientists at ISSS 2010 held recently at City Tech.

Osamu Mori of the Japanese Space Exploration Center spoke publicly for the first time about the launch of IKAROS at ISSS 2010 held recently at City Tech.

Photo credit: Calvin Grace for City Tech.

Advances being made to explore outer space using solar sails were discussed by the more than 60 scientists from 12 nations who attended the Second International Symposium on Solar Sailing (ISSS 2010) held at City Tech July 20-22.

Composed of reflective material just one-fifth the thickness of saran wrap with test models as large as half a football field, solar sails harness the pressure generated by sunlight just as a cloth sail catches the wind, propelling a spacecraft as if it were a sailing ship.

The state of energy-efficient solar sailing space flight technology was discussed by scientists and engineers from Canada, China, France, Germany, Italy, Japan, Luxembourg, Russia, Spain, Sweden, the United Kingdom and United States.

According to a declaration issued by the international experts at the end of the symposium, they unanimously agree that solar sail technology “has significantly advanced in its technology readiness since the first symposium held in Ammersee, Germany (2007). It has been confirmed by flight testing in deep space that solar sail technology is viable for space flight operations.

Many important applications of solar sails were identified as useful to the international science community. It is vital that these users be engaged as soon as possible so that they may better understand the capabilities offered by solar sail technology and to thereby obtain their advocacy, according to the declaration.

There was palpable excitement in City Tech’s Atrium Amphitheatre when Osamu Mori of JAXA, the Japanese Space Exploration Center, spoke publicly for the first time about the launch of IKAROS, the world’s first successful solar sail space mission. As he made his presentation, the other scientists were aware that IKAROS was two months into an historic six-month interplanetary space flight around Venus.

Through stunning visuals, Mori showed how IKAROS has succeeded in stretching out its sail, confirming that it is accelerating under pressure from sun. Solar cells and small sets of LEDs (light-emitting diodes) cover the surface of this sail, which is only microns thick. When the IKAROS team changes the color of particular LED lights, they change how much light that side of the sail absorbs, allowing the scientists to steer the craft.

Mori said that later missions will combine solar sails with ion drives to deliver probes to Jupiter and the Trojan asteroids. These hybridized spacecraft will enable a probe to be propelled to a distant planet within a reasonable timeframe.

“With rockets and other spacecraft consuming fuel, the prospect of using solar sails, which employ the pressure of sunlight as propulsion, is becoming key,” said City Tech Physics Dept. Chair Roman Kezerashvili, head of the symposium’s local organizing committee. “We hosted an amazing collection of scholars who are working on this important cutting-edge technology.”

The three-day symposium began on Tuesday, July 21, a date recognized last year by New York’s governor and state senate as “Space Exploration Day.” At City Tech, the scientists in attendance celebrated Japan’s successful launch and spoke of upcoming launchings by The Planetary Society and NASA.

The Planetary Society’s current executive director, Louis Friedman, gave a history of solar sailing, including flights that failed and others that didn’t materialize. He noted that when he was at the Jet Propulsion Labs in California in the 1970s, he first pitched the solar sailing concept to NASA. Now, The Planetary Society is involved with the Lightsail-1 project. Plans call for this solar sail craft to be launched next year hundreds of miles up into orbit around the Earth, piggybacking on a NASA rocket launch.

Aerospace engineer Les Johnson, deputy manager of the Advanced Concepts division of NASA’s George C. Marshall Space Flight Center in Huntsville, AL, said NASA investigated solar sails in the early 2000s, but now was working more actively on the technology. It is focusing on square sail ideas that resemble IKAROS and LightSail-1 as well as on a much wilder designs -- consisting of a ribbon hundreds of meters long but less than one meter across -- in an attempt to find the most efficient design.

Kezerashvili, a nuclear and theoretical physicist who has authored 130-plus scientific papers and four textbooks, made a presentation on using a solar sail mission to test fundamental physics. He explained how a solar sail could be used to test certain predictions of Albert Einstein’s General Theory of Relativity. This is based on papers that Kezerashvili co-authored with City Tech Physics Professor Justin Vazquez-Poritz. Namely, a massive spinning body like the Sun distorts the fabric of spacetime around it like a whirlpool in water, causing other objects to rotate around it. Kezerashvili said that by observing the motion of a solar sail orbiting the sun, one might be able to detect this effect, which is known as frame dragging.

Kezerashvili, who is editing the symposium proceedings for a special issue of Advances in Space Research,  and Vazquez-Poritz’s proposal was just one of the many possible applications for solar sails explored by scientists and solar sail advocates during the City Tech symposium.

Solar sail missions, NASA’s Johnson said, are by far the best way to make round-trips in space. “Most other missions run out of gas,” he says. But here, “as long as the sun is shining, you’ve got thrust.”

In addition to The Planetary Society’s Lightsail-1 and NASA’s NanoSail-D2, other government, academic institutions and private organizations are developing multiple, small (approximately 10 square meters to 25 square meters) solar sail systems that will be space flight validated within the next few years. These include: The University of Surrey’s CubeSail and DEORBITSAIL, CU Aerospace’s CubeSail, Deutsches Zentrum fur Luft-und Raumfahrt/European Space Agency’s Gossamer-1 and Air Force Research Laboratory’s FURL. Also, the JAXA team will continue to evaluate and analyze test flight data of IKAROS.

The declaration signed by the symposium participants at City Tech concluded with, “The participants of the Second ISSS recommend accelerated development and space flight testing of solar sail technology to provide reliable, robust and revolutionary capabilities for future space science, exploration and operational missions.”

8.09.10


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