July 22, 2001. Copyright 2001. Graphic News. All rights reserved.

Spacecraft to cruise on a sunbeam

LONDON, July 22, Graphic News: The first launch of a solar sail will be made using a converted intercontinental ballistic missile launched from a Russian submarine in the Barents Sea on Friday (July 20).

The Volna carrier rocket -- in one of the 16 silos on board the Borisoglebsk ballistic missile submarine -- will blast a prototype of the Cosmos-1 spacecraft to an altitude of 750 miles (1,200 km) to verify the technical viability of the solar sail concept. The first test will carry two Russian-built sail blades aloft.

The 30-minute suborbital flight is only designed to test how the blades unfurl. This will be followed by the launch later this year of the eight-sail Cosmos 1 spacecraft.

The US$4 million solar sail experiment has been privately funded by the Planetary Society, which was founded by astronomer Carl Sagan to promote space exploration.

The Planetary Society, which has more than 100,000 dues-paying members, contracted the Babakin Space Center, located just outside Moscow, to construct and launch its spacecraft. Russian scientists had proposed the idea of boosting the craft into orbit using a Volna ICBM. Arms-control agreements require the Russians to either discard the rockets or convert them to other uses.

ÒWe are literally taking these missiles out of the battlefield,Ó says Louis Friedman, executive director of the Planetary Society. ÒThe plan was so practical and inexpensive that we were able to find private funding for the mission.Ó

The solar sail, which will power Cosmos 1, is a very thin sheet of reflective Mylar. This ultra-thin plastic sheet -- about a quarter of the thickness of a trash bag -- will use the miniscule force exerted by a beam of sunlight in the same way that a sailboat is pushed along the water by the force of the wind.

Scientists describe light as little packets of energy called photons. It is the energy from these photons which run a solar-powered calculator or watch.

Once in Earth orbit Cosmos 1 will unfurl eight Mylar panels to form a 100-feet wide (30-meter-wide) solar sail to harness photons to propel it forward. As the sail reflects sunlight, zillions of photons bouncing off its mirror surface will transfer momentum, pushing the sail along.

The great advantage of solar sails over conventional propulsion systems is that they do not require huge loads of rocket fuel. In fact, NASA is studying the use of solar sails to propel the Interstellar Probe, a mission tentatively scheduled for launch in 2010. 

Although a solar sail is at first slower than a conventional rocket, it continues to accelerate over time. Designers say a spacecraft with solar sails could accelerate to speeds as high as 55 miles per second (90 kilometers per second), allowing it to travel far beyond the solar system in just a few years. 

ÒCosmos 1 could serve as a stepping-stone for such efforts,Ó says Friedman. ÒI hope this will be the beginning of something grand.Ó
/ENDS
Source: Planetary Society