Solar probe must survive ‘hellish’ conditions

JOHNS HOPKINS (US) — Engineers are designing a NASA probe to take a close-up look at the sun while enduring blowtorch temperatures, supersonic solar particles, and intense radiation.

The planned Solar Probe Plus must survive and thrive in hellish conditions more than 95 percent of the roughly 93-million-mile distance from Earth to the surface of our local star.

NASA has given designers developing the Solar Probe Plus the go-ahead to continue design work, building on concepts created during an initial design effort.


“Solar Probe Plus will be a historic mission, flying closer to the sun than any previous spacecraft,” says Nicky Fox, Solar Probe Plus project scientist at the Johns Hopkins University Applied Physics Laboratory.

“Encountering the sun’s atmosphere (or corona) for the first time, Solar Probe Plus will understand how the corona is heated and how the solar wind is accelerated. Solar Probe Plus will revolutionize our knowledge of the physics of the origin and evolution of the solar wind.”

“Solar Probe Plus is an extraordinary mission of exploration, discovery, and deep understanding,” says Lika Guhathakurta, the Living with a Star program scientist at NASA headquarters. “We cannot wait to get started with the next phase of development.”

After launch, scheduled for 2018, Solar Probe Plus will orbit the sun 24 times, gradually moving closer on each pass. The small car-sized spacecraft will zip through the sun’s atmosphere as close as 4 million miles from its surface—exploring a region (and facing conditions) no other spacecraft ever has encountered.

The probe will include five science investigations specifically designed to solve two key questions of solar physics: Why is the sun’s outer atmosphere so much hotter than the sun’s visible surface, and what accelerates the solar wind that affects Earth and our solar system?

As the spacecraft approaches the sun, its carbon-carbon composite heat shield and other components must temperatures exceeding 2,550 degrees Fahrenheit impacts from supersonic solar particles, and intense radiation.

Its science instruments will survey the most abundant particles in the solar wind—electrons, protons and helium ions—and measure their properties; image the solar wind; measure electric and magnetic fields, radio emissions and shock waves that course through the sun’s atmospheric plasma; and inventory the elements in the sun’s atmosphere.

In addition to working on the heat shield, researchers at the Applied Physics Lab will continue testing and development of other tricky aspects of spacecraft design.

For example, engineers will build and test a flight-like active cooling system designed to keep the solar arrays at safe operating temperature throughout the orbit. Most spacecraft parts will be subjected to high-velocity dust tests that simulate the pelting they’ll face flying through swarms of high-energy particles near the sun.

“Solar Probe Plus presents technical challenges like no mission before it,” says Andrew Driesman, Solar Probe Plus project manager at APL. “Over the next 26 months, our goal is to get these technologies to the point where we have full scale prototypes that we can test in a realistic environment.”

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