NASA calls on APL to send a probe to the sun

Artist's concept of NASA's Solar Probe spacecraft making its pass toward the sun, where it will study the forces that create solar wind. Preliminary designs include a 9-foot-diameter, 6-inch-thick, carbon-foam-filled... Click here for more information.

The Johns Hopkins University Applied Physics Laboratory is sending a spacecraft closer to the sun than any probe has ever gone - and what it finds could revolutionize what we know about our star and the solar wind that influences everything in our solar system.

NASA has tapped APL to develop the ambitious Solar Probe mission, which will study the streams of charged particles the sun hurls into space from a vantage point within the sun's corona -- its outer atmosphere -- where the processes that heat the corona and produce solar wind occur. At closest approach Solar Probe would zip past the sun at 125 miles per second, protected by a carbon-composite heat shield that must withstand up to 2,600 degrees Fahrenheit and survive blasts of radiation and energized dust at levels not experienced by any previous spacecraft.

Experts in the United States and abroad have grappled with this mission concept for more than 30 years, running into seemingly insurmountable technology and budgetary limitations. But in February an APL-led team completed a Solar Probe engineering and mission design study at NASA's request, detailing just how the robotic mission could be accomplished.

The study team used an APL-led 2005 study as its baseline, but then significantly altered the concept to meet challenging cost and technical conditions provided by NASA.

"We knew we were on the right track," says Andrew Dantzler, Solar Probe project manager at APL. "Now we've put it all together in an innovative package; the technology is within reach, the concept is feasible and the entire mission can be done for less than $750 million [in fiscal 2007 dollars], or about the cost of a medium-class planetary mission. NASA decided it was time."

APL will design and build the spacecraft, on a schedule to launch in 2015. The compact, solar-powered probe would weigh about 1,000 pounds; preliminary designs include a 9-foot-diameter, 6-inch-thick, carbon-foam-filled solar shield atop the spacecraft body. Two sets of solar arrays would retract or extend as the spacecraft swings toward or away from the sun during several loops around the inner solar system, making sure the panels stay at proper temperatures and power levels. At its closest passes the spacecraft must survive solar intensity more than 500 times what spacecraft experience while orbiting Earth.