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Probe to approach the sun

May 1, 2008
Courtesy Johns Hopkins University 
Applied Physics Laboratory
and World Science staff

Sci­en­tists plan to send a space­craft nearer the sun than ev­er be­fore. The un­manned NASA So­lar Probe would go nine times clos­er to the star than the hot­test plan­et, Mer­cu­ry, and in­to an in­fer­no more than hot enough to melt stone.

Artist's con­cept of NA­SA's So­lar Probe space­craft mak­ing a dar­ing pass to­ward the sun, where it would study the forc­es that cre­ate so­lar wind. Pre­lim­i­nar­y de­signs in­clude a 9-foot-diameter, 6-inch-thick, carbon-foam-filled so­lar shield atop the space­craft body, and two sets of so­lar ar­rays that would re­tract or ex­tend as the space­craft swings to­ward or away from the sun—mak­ing sure the pan­els stay at prop­er tem­per­a­tures and pow­er lev­els. (Cred­it: NA­SA/Johns Hop­kins Uni­ver­si­ty Ap­plied Phys­ics Lab­o­ra­to­ry)



The finds could rev­o­lu­tion­ize know­ledge of our star and the so­lar wind it em­anates, which in­flu­ences ev­erything in our so­lar sys­tem, re­search­ers pre­dict.

The space agency has tapped the Johns Hop­kins Uni­ver­s­ity Ap­plied Phys­ics Lab­o­r­a­to­ry in Lau­rel, Md. to de­vel­op the mis­sion. It is meant to study the streams of charged par­t­i­cles the sun hurls in­to space from a van­tage point with­in the sun’s co­ro­na, or out­er at­mo­sphere. There, pro­cesses that heat the co­ro­na and pro­duce this wind oc­cur.

At clos­est ap­proach the probe would zip by the sun at 125 miles (200 km) per sec­ond, pro­tected by a carbon-composite shield that must with­stand up to 2,600 de­grees Fahr­en­heit (1,400 Cel­sius), re­search­ers said. The craft would al­so have to sur­vive blasts of radia­t­ion and en­er­gized dust un­like any that hit pre­vi­ous crafts.

Expe­rts have grap­pled with how to send a probe so near the sun for dec­ades. But like the doomed he­ro Ic­a­rus of Greek myth—who strapped on wings, but fell af­ter fly­ing too near the sun—these re­search­ers have hit re­peat­ed road­blocks. Not death, but tech­no­log­i­cal and budg­et­ary prob­lems thwarted them.

But in Feb­ru­ary a team from the Hop­kins lab­o­r­a­to­ry com­plet­ed a study at NASA’s re­quest lay­ing out a plan for the mis­sion. It all “can be done for less than $750 mil­lion,” said An­drew Dant­zler, So­lar Probe proj­ect man­ag­er at the lab­o­r­a­to­ry. The lab­o­r­a­to­ry is to de­sign and build the craft, planned for launch in 2015.

The com­pact, so­lar-pow­ered probe would weigh about 1,000 lb (450 kg). Pre­lim­i­nar­y de­signs in­clude a carbon-foam-filled so­lar shield atop the craft, six inches (15 cm) thick and the width of a ping-pong ta­ble. Two sets of so­lar ar­rays would re­tract or ex­tend as the ship swings to­ward or away from the sun.

The probe will use sev­en Ve­nus fly­bys over nearly sev­en years to grad­u­ally shrink its or­bit around the sun, re­search­ers said. It would come as close as 4.1 mil­lion miles (6.6 mil­lion kilo­me­ters), some eight times clos­er than any pre­vi­ous craft.

The goals are to de­ter­mine the struc­ture and dy­nam­ics of the mag­net­ic fields at the sources of so­lar wind; trace the flow of en­er­gy that heats the co­ro­na and ac­cel­er­ates the so­lar wind; de­ter­mine what ac­cel­er­ates and trans­ports en­er­get­ic par­t­i­cles; and ex­plore dusty plas­ma near the sun and its in­flu­ence on so­lar wind and en­er­get­ic par­t­i­cle forma­t­ion. 

De­tails are to be spelled out in another study to come from NASA this year.

“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,” said Rob­ert Deck­er, So­lar Probe proj­ect sci­ent­ist at the Ap­plied Phys­ics Lab­o­r­a­to­ry. “As with all mis­sions of disco­very, So­lar Probe is likely to raise more ques­tions than it an­swers.”


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Scientists plan to send a spacecraft closer to the sun than ever before. The unmanned NASA Solar Probe would go nine times closer to the star than the hottest planet, Mercury, and into an inferno more than hot enough to melt stone. The finds could revolutionize what we know about our star and the solar wind it emanates, which influences everything in our solar system, researchers predict. NASA has tapped The Johns Hopkins University Applied Physics Laboratory in Laurel, Md. to develop the mission. It is meant to study the streams of charged particles the sun hurls into space from a vantage point within the sun’s corona, or outer atmosphere.There, processes that heat the corona and produce the wind occur. At closest approach the probe would zip by the sun at 125 miles (200 km) per second, protected by a carbon-composite shield that must withstand up to 2,600 degrees Fahrenheit (1,400 Celsius), researchers said. The craft would also have to survive blasts of radiation and energized dust unlike any that hit previous crafts. Experts have grappled with how to send a probe so near the sun for decades. But like the doomed hero Icarus of Greek myth—who strapped on wings, but fell after flying too near the sun—these researchers have hit repeated roadblocks. Not death, but technological and budgetary problems thwarted them. But in February a team from the Hopkins laboratory completed a study at NASA’s request laying out a plan for the mission. “Tthe entire mission can be done for less than $750 million,” said Andrew Dantzler, Solar Probe project manager at the laboratory. The laboratory is to design and build the spacecraft, on an announced schedule to launch in 2015. The compact, solar powered probe would weigh about 1,000 lb (450 kg). Preliminary designs include a carbon-foam-filled solar shield atop the spacecraft body six inches (15 cm) thick and the width of a ping-pong table. Two sets of solar arrays would retract or extend as the spacecraft swings toward or away from the sun. The probe will use seven Venus flybys over nearly seven years to gradually shrink its orbit around the sun, researchers said. It would come as close as 4.1 million miles (6.6 million kilometers), some eight times closer than any previous craft. The goals are to determine the structure and dynamics of the magnetic fields at the sources of solar wind; trace the flow of energy that heats the corona and accelerates the solar wind; determine what accelerates and transports energetic particles; and explore dusty plasma near the sun and its influence on solar wind and energetic particle formation. Details are to be spelled out in a Solar Probe Science and Technology Definition Team study to come from NASA this year. “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,” said Robert Decker, Solar Probe project scientist at the Applied Physics Laboratory. “As with all missions of discovery, Solar Probe is likely to raise more questions than it answers.”