the parker solar probe is expected to launch in the summer of 2018 on a historic nasa mission to travel into the atmosphere of the sun (about four million miles from its surface) to provide the closest observations of the star yet recorded.

the solar panels are shown here on this artist rendering of parker solar probe;
they are the black squares with gray rectangles on the center of the spacecraft.
(nasa/jhuapl)

in order for the probe to survive in the hostile conditions of the atmosphere of the sun, engineers have designed a revolutionary cooling system to ensure its solar arrays perform at peak level, according to a notice from johns hopkins university, which worked on the system in its applied physics lab.

the design of the probe included a thermal protection system (tps), an eight-foot-diameter-shield, which will hide all the instruments on the probe with the exception of four antennas and a special particle detector.

“every system will be protected, that is, except for the two solar arrays that power the spacecraft,” the article explained. “when the spacecraft is closest to the sun, the solar arrays will be receiving 25 times the solar energy they would while orbiting earth, and the temperature on the tps will reach more than 2,500°f. the cooling system will keep the arrays at a nominal temperature of 320°f (160°c) or below.”

the edges of the solar arrays are bent upward, the article added, and when the probe gets to its closest point to the sun, those edges will be extended beyond the tps to produce power for the craft. to combat the intense heat of the sun, johns hopkins engineers, in partnership with united technologies aerospace systems and solaero technologies, design an active cooling system for the arrays.

“the parker solar probe cooling system has several components: a heated accumulator tank that will hold the water during launch,” according to the university, “two-speed pumps; and four radiators made of titanium tubes and sporting aluminum fins just two hundredths of an inch thick.

“as with all power on the spacecraft, the cooling system is powered by the solar arrays—the very arrays it needs to keep cool to ensure its operation. at nominal operating capacity, the system provides 6,000 watts of cooling capacity—enough to cool an average-sized living room.”

the coolant is about five liters of pressurized water. it was chosen because of its ability to work across the range of 50-257°f. (pressurizing the water raises its boiling point to 257°f.)

in addition, a ceramic carrier will be soldered to the bottom of each photovoltaic cell and attached to the platen with a thermal adhesive that ensures proper thermal conductivity and electrical insulation.

as if planning for the heat of the sun was not enough, engineers also face a difficult task during the minutes following the launch.

the article explained, “first, temperatures of the solar arrays and cooling system radiators will drop from that in the fairing (about 60°f) to temperatures ranging from -85°f to -220°f before they can be warmed by the sun. the pre-heated coolant tank will keep the water from freezing; the specially designed radiators—designed to reject heat and intense temperatures at the sun—will also survive this bitter cold, thanks to a new bonding process and design innovations.”

to avoid the water freezing early in the mission, the first two radiators have an increased thermal blanket.

because the probe will be speeding past the sun at 450,000 mph and will be 90 million miles from earth, a new autonomous software was designed to enable the systems to make adjustments to ensure proper cooling. in particular, the system will have the crucial task of constantly adjusting the solar arrays to the optimal angle.

learn more about the parker solar probe in the video below: