LAUREL, MAY 3:So how do you send a spacecraft to the sun without broiling it to a cinder?

“We go at night,” said Andrew A. Dantzler, project manager for Solar Probe, a new space science mission announced on Friday by the Johns Hopkins University’s Applied Physics Lab near Laurel.

That’s been the running joke around the lab, Dantzler said. But APL scientists and engineers are perfectly serious about the $750 million NASA-funded mission — the first to fly scientific instruments through the sun’s million-degree corona, and to within 4.1 million miles of its roiling surface. Launch is planned for 2015, with the craft’s first solar flyby just three months later — thanks to a boost from the Sun’s gravity.

Buzzing the sun repeatedly demands a tough spacecraft. Solar Probe — 9-feet long and 1,000 pounds — will need to shield its instruments and communications gear from temperatures up to 2,600 degrees Fahrenheit.

APL’s designers are working on a 6-inch-thick solar shield made of advanced carbon-carbon foam. Solar physicists want to answer two questions:

• How temperatures in the corona — the sun’s outermost atmosphere — can reach more than a million degrees centigrade, while those down on the surface are only around 6,000 degrees.

• How the solar wind, which is not very strong near the sun’s surface, is accelerated to several million miles per hour as it moves out of the corona and across the solar system.

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