Despite being the brightest and most obvious object in our skies, there is still a lot to learn about the Sun.
This is why NASA and their partners are working on the Parker Solar Probe that will eventually fly seven times closer than any other artificial object to date: its closest fly-by will be 3.8 million miles from the surface. For context, the Earth orbits at about 93 million miles away from the surface of the Sun, and Mercury (the closest planet to the Sun) about 36 million miles. This will also mark the first time humanity has sent a probe to the Sun’s corona, its outer atmosphere.
A rendering of the Parker Solar Probe. Image courtesy of NASA.
The Parker Solar Probe is expected to launch later this summer, sometime between July 31st and August 19th, using Venus for gravity assists to get close to the Sun.
However, this close proximity fly-by does not come without its engineering challenges—after all, we still have problems with our smartphones overheating if left in the sun or heat for too long. How do we design, build, and test a sensitive piece of equipment for millions of times more heat and radiation exposure?
The Faraday Cup: Unconventional Designing and Testing
Designing electronics that can withstand extreme environments involves a bit of materials engineering. There have been great strides over the years in figuring out what works and what doesn’t—take the research being done on designing a spacecraft that can survive the surface of Venus for example. The last time humans have sent a probe to the planet was in 1984, and the vehicle and it’s electronics only last two hours before being vaporized under extreme heat and pressure. JPL engineers suspect they could now send a spacecraft that could last much longer using different materials in the electronics, such as ceramic and glass.
On the Parker probe, for one of its instruments, the University of Michigan has designed a Faraday cup using sapphire crystal insulators and refractory materials. The cup is part of the Solar Wind Electrons Alphas and Protons (SWEAP) investigation, which will help scientists determine the composition of the Sun’s solar winds.
Sapphire has been used in electronics in the military and aerospace industries since the 60s. The material acts as both an electrical and thermal insulator, protecting electronics from radiation and heat. Refractory materials are heat resistant minerals, used in things like reactors and furnaces.
Of course, building and designing a sensor is half the challenge—the other half is successfully testing it. In order to simulate the extreme heat of the Sun’s surface, the research team bought four old IMAX movie theatre bulbs from eBay, which uses bulbs that can reach 5,700 Kelvins. The researchers say that this is about the same temperature as the Sun’s surface, with a similar spectrum of light.
With the four projectors, a test chamber was built that then exposed the cup to a simulated near-Sun environment. Then, ions were shot at the cup’s sensors to ensure the device was still working and able to detect the plasma particles it was designed to measure. The team, and the cup, so far have passed all tests.
The Sun’s Impacts on Earth Tech
The SWEAP mission has a very obvious benefit to us on Earth. Solar activity can, and does, impact our daily lives. While we enjoy protection from most cosmic particles thanks to the Earth’s magnetosphere, CMEs (Coronal Mass Ejections), solar flares, and solar maximums can disrupt electronics in Low Earth Orbit, and even on Earth’s surface.
Solar activity is cyclic and every 11 years there is a “solar maximum”, a period where there more sunspots appear on the Sun’s surface which signify magnetic field fluctuations, and the overall irradiance of the Sun increases by about 0.07 percent. During this time there is a higher chance of a coronal mass ejection, which sends a large number of protons and electrons out into space.
Image courtesy of Space Answers.
For Earth, we have been mostly lucky to avoid them for the last 100+ years, but in 1859 a CME did in fact hit Earth. Some of the effects were interesting, such as the creation of an aurora that lit up the sky across North America. Other impacts were less welcome, like damage to telegraph systems.
Today, we rely on much more sophisticated systems that are much more vulnerable to this sort of damage. Satellites in orbit could become severely damaged or inoperable, impacting GPS navigation, communications, and Earth Observation. On the ground, power grids could become damaged, creating blackouts.
The study of the Sun is certainly a worth one, especially from an electronics engineering point of view. Understanding more about what the Sun’s atmosphere is composed of and being able to better predict its activity could help us mitigate the certain damage it will otherwise cause us if or when we are struck by another CME.
And in the meantime, ingenious new ways to design heat and radiation tolerant equipment is helping us investigate.