What’s Up in the Sky – June, 2015
Sailing by Light
Wouldn’t it be nice if we could travel to other planets on a ship that requires no fuel tanks, no thrusters, no complex motors, pumps, wiring, or tubing? How about a spacecraft that can operate on solar energy alone, and I don’t mean solar panels powering electric motors.
In fact, it has already been done. In May of 2010, Japan launched the IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) spacecraft on a mission that would take it to Venus and then continue in orbit around the Sun. And on May 20, the Planetary Society successfully launched LightSail, a prototype craft designed to test the feasibility of using solar radiation for not only propulsion, but also navigation.
But let’s back up a minute and look at the concept of solar sailing. Light consists of packets of energy called photons and, although they have no mass, photons have momentum. When they strike a shiny surface, a lot of their momentum is transferred, giving the surface a small impulse or push. The force is tiny but it is constant and a small force pushing for a long time can create a large change in velocity.
The Planetary Society’s LightSail (www.planetary.org) uses a new type of miniature spacecraft called CubeSats. CubeSats are cubes, 10 cm on a side, that can be combined to form larger spacecraft. LightSail consists of three such units stacked together measuring 10 by 10 by 30 centimeters, about the size of a loaf of bread.
Hitching a ride on an Atlas V rocket whose prime payload is a classified USAF mission, LightSail is currently orbiting Earth but has not yet unfurled its sails. That will happen after four weeks of thorough testing of all its avionic and electronic systems. After the waiting period the sails will be deployed and the spacecraft will be propelled by solar radiation. The downside is that this will greatly increase the atmospheric drag, causing the spacecraft to reenter the atmosphere in about a week.
This is all in the plan, however, as this is a test flight, designed to gather data and “shake down” all systems. The second mission, scheduled for a 2016 launch, will be aboard SpaceX’s new Falcon Heavy rocket which will take it to a higher orbit (almost 450 miles) where it will not be as greatly affected by Earth’s atmosphere. It is hoped that this will lay the foundation for possible interplanetary or even interstellar missions in the future.
Finally, I hope you have been following Venus and Jupiter in the western sky after sunset. You won’t want to miss their close encounter on the evening of June 30 when they will be the “stars” of everything up in the sky.
This month in history:
June 3: Gemini IV astronaut, Ed White, takes America’s first space walk – 1965
June 8: First unpowered glide test of X-15 – 1959
June 10: Mars rover “Spirit” launched – 2003
June 16: Valentina Tereshkova first (and only solo) woman in space – 1963
June 18: Sally Ride becomes first American woman in space – 1983
June 22: Evidence of liquid water on Mars announced by NASA – 2000
June 30: Tunguska impact flattens hundreds of miles of Siberian forrest – 1908