Solar Sail Stunner Play Audio Download Audio Join Mailing List   
       
   January 24, 2011 : Call it a stunner.   
       
   In an unexpected reversal of fortune, NASA's NanoSail-D spacecraft has   
   unfurled a gleaming sheet of space-age fabric 650 km above Earth, becoming the   
   first-ever solar sail to circle our planet.   
       
   "We're solar sailing!" says NanoSail-D principal investigator Dean Alhorn of   
   the Marshall Space Flight Center in Huntsville, AL. "This is a momentous   
   achievement."   
   [...]   
   An artist's concept of a solar sail in Earth orbit. [larger image]   
   NanoSail-D spent the previous month and a half stuck inside its mothership,   
   the Fast, Affordable, Science and Technology SATellite (FASTSAT). FASTSAT was   
   launched in November 2010 with NanoSail-D and five other experiments onboard.   
   High above Earth, a spring was supposed to push the breadbox-sized probe into   
   an orbit of its own with room to unfurl a sail. But when the big moment   
   arrived, NanoSail-D got stuck.   
       
   "We couldn't get out of FASTSAT," says Alhorn. "It was heart-wrenching-yet   
   another failure in the long and troubled history of solar sails."   
       
   Team members began to give up hope as weeks went by and NanoSail-D remained   
   stubbornly and inexplicably onboard. The mission seemed to be over before it   
   even began.   
       
   And then came Jan. 17th. For reasons engineers still don't fully understand,   
   NanoSail-D spontaneously ejected itself. When Alhorn walked into the control   
   room and saw the telemetry on the screen, he says "I couldn't believe my eyes.   
   Our spacecraft was flying free!"   
   [...]   
   Click to listen to one of NanoSail-D's beacon packets recorded by radio   
   amateur Henk Hamoen of the Netherlands. [audio] The team quickly enlisted   
   amateur radio enthusiasts Alan Sieg and Stan Sims at the Marshal Space Flight   
   Center to try to pick up NanoSail-D's radio beacon.   
       
   "The timing could not have been better," says Sieg. "NanoSail-D was going to   
   track right over Huntsville, and the chance to be the first ones to hear and   
   decode the signal was irresistible."   
       
   Right before 5pm CST, they heard a faint signal. As the spacecraft soared   
   overhead, the signal grew stronger and the operators were able to decode the   
   first packet. NanoSail-D was alive and well.   
       
   "You could have scraped Dean off the ceiling. He was bouncing around like a   
   new father," says Sieg.   
       
   The biggest moment, however, was still to come. NanoSail-D had to actually   
   unfurl its sail. This happened on Jan. 20th at 9 pm CST.   
       
   Activated by an onboard timer, a wire burner cut the 50lb fishing line holding   
   the spacecraft's panels closed; a second wire burner released the booms.   
   Within seconds they unrolled, spreading a thin polymer sheet of reflective   
   material into a 10 meter-square sail.   
       
   Only one spacecraft has done anything like this before: Japan's IKAROS probe   
   deployed a solar sail in interplanetary space and used it to fly by Venus in   
   2010. IKAROS is using the pressure of sunlight as its primary means of   
   propulsion-a landmark achievement, which has encouraged JAXA to plan a   
   follow-up solar sail mission to Jupiter later this decade.   
       
   NanoSail-D will remain closer to home. "Our mission is to circle Earth and   
   investigate the possibility of using solar sails as a tool to de-orbit old   
   satellites and space junk," explains Alhorn. "As the sail orbits our planet,   
   it skims the top of our atmosphere and experiences aerodynamic drag.   
   Eventually, this brings it down."   
       
   Indeed, mission planners expect NanoSail-D to return to Earth, meteor-style,   
   in 70 to 120 days.   
   [...]   
   The NanoSail-D team gathered around their sail after a successful laboratory   
   deployment test: movie.   
       
   If this works, NanoSail-D could pave the way for a future clean-up of   
   low-Earth orbit. Drag sails might become standard issue on future satellites.   
   When a satellite's mission ends, it would deploy the sail and return to Earth   
   via aerodynamic drag, harmlessly disintegrating in the atmosphere before it   
   reaches the ground. Experts agree that something like this is required to   
   prevent an exponential buildup of space junk around Earth.   
       
   Alhorn and colleagues will be monitoring NanoSail-D in the months ahead to see   
   how its orbit decays. They'd also like to measure the pressure of sunlight on   
   the sail, although atmospheric drag could overwhelm that effect.   
       
   No matter what happens next, NanoSail-D has already made history: It has   
   demonstrated an elegant and inexpensive method for deploying sails and become   
   the first sail to orbit Earth. Eventually, the team will diagnose the sail's   
   reluctance to leave FASTSAT-"and then we'll be batting a thousand," says   
   Alhorn.   
       
   A follow-up story on Science@NASA will explain how sky watchers can track and   
   photograph NanoSail-D before it returns to Earth. Stay tuned for "Solar Sail   
   Flares."   
       
       
   Author: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   Credits: "I am thrilled with the success of our partnership with NASA's Ames   
   Research Center," adds Alhorn. "This project would not have been possible   
   without their involvement and the support of the many other companies on our   
   team. It was truly a team effort."   
       
   NanoSail-D -- home page   
       
   A Brief History of Solar Sails -- Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.59   
    * Origin: NCS BBS (1:3828/7)