Michigan Engineering News

Two men inspecting the heat shield

Part 5: Sunblock and instrumentation

The extreme conditions of the corona are one of the main reasons a solar probe mission like this hasn’t been undertaken before. But Parker features a series of innovations that will allow the probe to get close enough to do what needs to be done.

Part 5 of 7. This is a seven-part series anticipating the launch of the first mission to the sun, NASA’s Parker Solar Probe. The University of Michigan’s Justin Kasper, a climate space science professor, serves as one of the principal investigators for the mission. 

It’s the weirdest thing – and totally counterintuitive. The sun’s outermost atmosphere, NASA scientists believe, is hotter than its surface.

You would expect temperatures to cool as you move away from the 10,340-degree-Fahrenheit surface of a burning ball of gas. But entering the sun’s corona, things get hotter – up to 1,000 times hotter. And that’s where the Parker Solar Probe is headed.

Scheduled to launch at the end of July, the probe will travel closer to the sun than any man-made object before it to gather data from the corona. That data is expected to help create an early-warning system to protect Earth from dangerous solar weather.

Researcher Justin Kasper meeting with a collaborator
Justin Kasper (left) is the principal investigator for Parker’s SWEAP investigation – charged with measuring the solar wind.

Among those charged with overseeing that data collection is Justin Kasper, a principal investigator on the Parker mission and a climate and space science professor at the University of Michigan.

The extreme conditions of the corona are one of the main reasons a solar probe mission like this hasn’t been undertaken before. It simply wasn’t possible. But Parker features a series of innovations that will allow the probe to get close enough to do what needs to be done.

Key among these is the probe’s heat shield, a 4.5-inch-thick plate of carbon foam that will sit three meters away from the craft’s most sensitive equipment. Its front is covered by synthetic sapphire crystal across its eight-foot diameter to help survive temperatures of up to 1,600 degrees Celsius and five megawatts of sunlight.

Meanwhile, behind the shield, temperatures will remain at just a few hundred degrees.

To run all of the equipment protected by the shield, any self-respecting solar probe would utilize solar power, right? Before Parker, that was impossible since solar panels weren’t able to deal with the extreme heat.

But Parker’s engineers made it work – after launch, the probe will unfold a pair of long solar panels to each side for power. Their conductors, capable of handling the extreme heat and light of the mission, are a relatively new creation.

Probe approaching the sun
After launch, the probe will unfold a pair of long solar panels to each side for power. Illustration by Steve Alvey

Yet even far away from the sun, those panels will need cooling, and the probe provides an elegantly simple solution. It pumps water from behind the panels to an area in the shade of the heat shield, where it cools quickly before being sent back to the panels.

“It’s almost the same way coolant in your car’s engine is circulated through a radiator, except we don’t have any air to flow in space,” Kasper said. “We just have to radiate it.”

As Parker draws closer to the sun, roughly five days out, circulation will no longer do the trick. To offset the rising heat, the probe will draw in its solar panels behind the shield. Those panels are designed with slanted ends that allow a small portion to stick out from behind the shield and continue powering the craft.

Continue reading: “Part 6: The big send-off”

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James Lynch

Research News & Feature Writer