First private solar sail set for launch

 作者:逄卜     |      日期:2019-02-27 07:18:01
By Kelly Young The first privately-financed solar-sail spacecraft is scheduled to lift off on a converted Soviet intercontinental ballistic missile from a Russian submarine in the Barents Sea on Tuesday. Louis Friedman, director of the Cosmos 1 project for the Planetary Society, says the mission is a good way to test the novel method of space transportation. “It could turn out like blimps – a novelty that does not go anywhere – or it could be like airplanes,” he says Cosmos 1 is a solar sail spacecraft with eight triangular blades emanating from a central hub. The sails are made of lightweight reflective Mylar and measure 15 metres long and just 5 microns, or 0.005 millimetres, thick. Once the sails are unfurled, light from the Sun will strike the sails, exerting a small force and pushing the spacecraft. Given time, that small force can accelerate a spacecraft to very high speeds. Because of this, solar sails may one day allow probes to travel huge distances with a minimal fuel burden. Cosmos 1 is expected to launch at 1946 GMT and should take about 20 minutes to reach orbit. Thirty minutes after launch should see the probe deploy its solar panels and start charging its batteries. For the next several days, it will undergo a commissioning phase and allow any air that may have hitched a ride to escape. Then on Sunday morning, the eight sails will deploy in about 10 minutes. The sails can pivot in place to allow the maximum number of photons hit them – pushing the craft away from the Sun – or let photons slip past the sails, allowing the craft’s orbit to take it towards the Sun. This persistent push from the photons should slightly accelerate Cosmos 1. As its speed increases, so too will its altitude. Friedman says that at its peak, Cosmos 1 could raise its altitude by several kilometres per day. Mission designers hope the probe will survive a month in the harsh environment of space. But an attempt to test technology for unfurling the solar sail’s panels in 2001 failed before it began when the spacecraft did not separate from the final stage of its Russian launch rocket and crashed in Kamchatka. Ground control will measure the solar sail’s progress through accelerometers on the probe, a GPS navigation system and Doppler tracking from the ground. If all goes well, a microwave beam from Earth may also be aimed at the spacecraft to see if it causes any change in speed. Other solar sails have made launch attempts. The Japanese Space Agency launched a solar sail on a suborbital flight in 2004, but it was not in space long enough for the Sun’s energy make any impact upon it. Russia launched large mirrors in space, but they were not used specifically for solar sailing. Meanwhile, NASA is conducting tests on its own solar sails in vacuum chambers. The Planetary Society’s device had a budget of less than $4 million – a pittance for a space mission. Cosmos Studios, run by Ann Druyan – wife of the late Carl Sagan – funded part of the project. The society is also considering a plan to place a Sun-observing spacecraft between Earth and the Sun,