Experts have grappled with this mission concept for more than 30 years. Now a team at Johns Hopkins University’s Applied Physics Laboratory is developing a special spacecraft for the Solar Probe mission of NASA.

At closest approach, the 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 energised dust at levels not experienced by any previous spacecraft.

True mission

“The Solar Probe is a true mission of exploration. For example, the spacecraft will go close enough to the sun to watch the solar wind speed up from subsonic to supersonic, and it will fly though the birthplace of the highest energy solar particles.

“And, as with all missions of discovery, Solar Probe is likely to raise more questions than it answers,” Robert Decker, Solar Probe Project Scientist at APL, was quoted by the ScienceDaily as saying.

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. 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 US $750 million, or about the cost of a medium-class planetary mission. NASA decided it’s time,” said Andrew Dantzler, APL’s Solar Probe Project Manager.

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.

The Solar Probe will use seven Venus flybys over seven years to shrink its orbit around the sun, coming as close as 4.1 million miles (6.6 million kilometres) to the sun, well within the orbit of Mercury and about eight times closer than any spacecraft has come before.