- NASA launched its $US1.5 billion ($2.1 billion)Parker Solar Probe mission toward the sun in August.
- The spacecraft is scheduled to “touch” the sun on Monday night during the first of 24 flybys.
- NASA’s probe will reach a speed of 343,100km/h while flying through solar plasma of about 3.6 million degrees.
- A heat shield protects the probe, but these conditions won’t be the fastest or hottest the spacecraft will experience.
NASA’s Parker Solar Probe just smashed the record for the fastest human-made object – but it’s just getting started on a series of feats that defy comprehension.
On Tuesday around 2.28pm AEDT, the probe should fly around the sun at about 343,100km/h. For comparison, NASA’s Juno spacecraft zooms past the cloud tops of Jupiter at 210,000km/h once every two months.
While the car-size Parker Solar Probe breaks humanity’s speed record, it’s also surviving some of the solar system’s harshest conditions. Right now, it’s screaming through the diffuse outer atmosphere of the sun, which is about 2,000,000 degrees Celsius.
The Parker Solar Probe is expected to easily survive this solar flyby, though its operators won’t know until later this week whether anything went wrong.
“For several days around the Nov. 5 perihelion” – the term for the closest point to the sun during a given orbit – “Parker Solar Probe will be completely out of contact with Earth because of interference from the sun’s overwhelming radio emissions,” the space agency said in a press release.
This orbit will bring the spacecraft within about 24 million km of the sun’s surface. That’s about one-sixth of the distance from the Earth to the sun.
However, this perihelion will be only the first of the Parker probe’s 24 death-defying solar encounters.
What’s in store for the Parker Solar Probe
Over the next seven years, the robot’s orbits will get closer and closer to the sun. Its speed relative to the star will also increase, as will the hellish conditions it must survive.
The Parker Solar Probe’s perihelion in December 2024 (about 21 orbits from now) will accelerate it to nearly 690,000 km/h and get it within 6.5 million km of the sun. That’s close enough to study the star’s mysterious atmosphere, solar wind, and other properties more deeply than ever before.
The goal is to crack two 60-year-old mysteries: why the sun has a solar wind, and how the corona – the star’s outer atmosphere – can heat up to millions of degrees, or about 100 times as hot as the sun’s surface temperature of about 5540 degrees Celsius.
“That defies the laws of nature – it’s like water rolling uphill,” Nicola Fox, a solar physicist at the Johns Hopkins University Applied Physics Laboratory, said during a NASA press briefing in 2017. “Until you actually go there and touch the sun, you can’t answer these questions.”
Both the solar wind and the corona are key to understanding solar storms, which can overwhelm electrical grids on Earth, harm our satellites, disrupt electronics, and possibly lead to trillions of dollars’ worth of damage. Data collected by the probe’s sensors might help space-weather forecasters better predict potentially devastating, violent solar outbursts.
The probe’s maximum expected speed translates to nearly 190km per second, which would be fast enough to fly from New York to Tokyo in less than a minute and is 3.3 times as fast as the Juno spacecraft.
To achieve this feat, the probe has to zoom past Venus seven times; each flyby helps the robot correct its orbit to slip closer to the sun and boost its speed.
On September 25, during its first Venusian flyby, the probe turned back toward Earth and took the photo below. Our planet is the bright dot at the top right.
How to fly through hell and back
For now, the searing-hot plasma that the plucky solar probe is withstanding is so diffuse that “it doesn’t influence the temperature of the spacecraft,” NASA said.
But the space agency added that the spacecraft’s high-tech heat shield is the reason its temperature is so stable.
The shield, called the Thermal Protection System, always faces the sun and blocks its light. It also protects the probe and its sensors from a solar wind of charged, high-energy particles that can mess with electronics.
The 8-foot-wide shield is made of 11.5cm of carbon foam sandwiched between two sheets of carbon composites, allowing it to absorb and deflect solar energy that might otherwise fry the probe. A water-cooling system is designed to help prevent the spacecraft’s solar panels from roasting and keep the Parker probe at 30 degrees Celsius.
Already, the surface of the heat shield has reached a temperature of about 437 degrees C. And it’s only expected to get hotter as the probe continues its mission.
During the most harrowing segment of its journey, NASA’s probe must withstand sunlight 3,000 times as strong as what occurs at Earth. Outside the spacecraft, temperatures during this pass may reach 1370 degrees Celsius. (If steel were heated to this temperature, the metal would melt into a liquid.)
The probe’s mission will continue for about seven years, or until it runs out of the propellant necessary to keep the heat shield pointed at the sun.
When that happens, the star’s blistering heat will burn up “90% of the spacecraft,” Shannon Stirone, a science writer, said on Twitter – but not the heat shield itself.
“The heat shield will then orbit the sun for millions of years,” she said.
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