NASA's Sunjammer solar sail to fly next year
(SpaceX) is slated to fly 's $27 million Sunjammer solar-sail demonstration next year as a secondary payload with the National Oceanic and Atmospheric Organization's ( ) revived Deep Space Climate Observatory (Dscovr) satellite.
Named after Arthur C. Clarke's 1964 short story, Sunjammer aims to be the largest solar sail ever constructed and deployed in space, and could prove the feasibility of an advanced space warning system for more timely and accurate predictions of solar-flare activity.
Led by L'Garde Inc. of Tustin, Calif., with ground-station support provided by NOAA, Sunjammer's propellantless solar sail could demonstrate the potential for other practical applications as well, including space-debris removal and de-orbiting of spent satellites.
says the mission builds on two successful ground-deployment experiments L'Garde conducted in 2005-06, quadrupling the area of the largest sail ever deployed on the ground, a 20 x 20-meter (4,300-sq.-ft.) behemoth tested by L'Garde at NASA's Plumbrook facility in Ohio. It also leverages the successful deployment of the NanoSail-D sail, a 100-sq.-ft. test article NASA launched in early 2011 to validate sail-deployment techniques.
“We're making a very high-performance sail and flying it in interplanetary space 300 million kilometers [186 million miles]—10 light seconds—from Earth,” says L'Garde Chief Operating Officer Nathan Barnes. “It's a point where we'll be far enough from the influence of the Earth's atmosphere that we'll get to do some really sporty things with the sail.”
Barnes says ultra-thin solar sails hold the potential to mitigate the Sun's force on spacecraft positioned at “pseudo” Lagrangian points close to the giant star—closer to the Sun than NOAA's Advanced Composition Explorer (ACE), which is currently monitoring coronal mass—where solar-weather satellites could provide more timely forecasts. NASA says the capability could improve space-weather warning time by up to 45 min.
Made of 5-micron-thick Kapton—the same material used to construct the giant sunshade on NASA's James Webb Space Telescope—the Sunjammer solar sail measures 1,200 sq. meters when fully deployed. When collapsed, however, it is the size of a dishwasher, weighs 70 lb. and is easily packed into a secondary payload on Falcon 9.
Barnes says the launch is funded by NASA through the U.S. Air Force, which contracted SpaceX to carry the Dscovr mission as part of the rocket's military launch certification process.
“They were going to this place, and we had planned on going to this place, so it's a terrific opportunity and synergy we're going to capitalize on,” says Barnes, adding that Sunjammer's launch costs comprise roughly one- third of NASA's $27-million investment in the demonstration.
Following liftoff from Cape Canaveral, the Falcon 9 is expected to jettison Dscovr, sending it to the Earth-Sun Lagrangian point, also known as L1, where it will replace ACE. Sunjammer will be jettisoned a short time later, initially deploying a small antenna and solar arrays before firing four 5-lb. hydrazine thrusters.
“These are small reaction control thrusters that big spacecraft use for orbital positioning, but we're using them for our main thrusters,” Barnes said. “The burn will take one or two minutes, but it gets us to where we mathematically can, or cannot, operate.”
If the sail deploys as expected, the booms supporting it will be “rigidized” ahead of final checkout of the spacecraft, at which point the hydrazine tank, thrusters and primary batteries will be jettisoned. In addition to deploying the 40 x 40-meter solar sail, the six-month mission will demonstrate attitude control and passive stability and trim using beam-tip vanes, and execute a navigation sequence with mission-capable accuracy.
Barnes says six months is enough to send Sunjammer close to its objective —the desired sub-L1 point 300 million km from Earth. But if all goes well, L'Garde plans to continue operating the spacecraft indefinitely.
“We have onboard solar arrays, and Sunjammer has no propellant, so until something fails, a device or a widget, there's no reason to turn it off,” he says. “We would like to experiment with a few other things, to incline ourselves up on on a radius plus or minus 20 degrees to demonstrate some more of the capabilities of the sail itself.”
During the mission, Sunjammer will fly two instruments developed by scientists at Imperial College London and Mullard Space Science Laboratory (MSSL) in Oxford. These include a magnetometer, known as Magic, and a wind analyzer, Swan—both designed to monitor different aspects of space weather to help researchers understand its influence on space-borne and ground-based systems.