Some scientists scoffed at University of Chicago physicist Eugene Parker’s 1958 paper proposing the existence of a solar wind — a constant stream of particles flowing out from the sun that permeates the entire solar system.
Spacecraft quickly proved him right, and 60 years later, Parker looked on early Sunday as a NASA probe bearing his name rocketed from Cape Canaveral Air Force Station on a $1.5 billion mission to “touch” the sun and solve some of its persisting mysteries.
“All I have to say is, wow, here we go,” said Parker, 91, after the launch he watched from Kennedy Space Center. “We’re in for some learning over the next several years.”
On its second attempt, the Parker Solar Probe — NASA’s first mission named for a living person — rumbled from the Space Coast at 3:31 a.m. Sunday atop one of the most powerful American rockets, United Launch Alliance’s 233-foot Delta IV Heavy.
A trio of first-stage boosters fired hydrogen-fueled engines to light up the night sky above Launch Complex 37, unleashing 2.1 million pounds of thrust to begin the probe’s seven-year mission.
A second rocket stage fired and then an extra third stage provided the final kick needed to hurtle the relatively small, 1,400-pound spacecraft out of Earth’s orbit and toward the sun, releasing it 43 minutes after liftoff.
“It went off like clockwork,” said Omar Baez, the mission’s NASA launch manager, said of Sunday’s countdown and launch. “The energy of that (launch) vehicle, the immense size, and when you realize how tiny the Parker Solar Probe satellite is, and you have this big vehicle around it, it’s just mind boggling.”
In six weeks, the probe will use the first of seven flybys of Venus to perform the equivalent of a handbrake turn to fine-tune its trajectory. That will set up the first of 24 petal-shaped orbits around Earth’s nearest star within a few months.
The first pass 15 million miles from the sun’s surface will already be the closest by any spacecraft, a distance that will close to within 3.8 million miles by the closest approaches through the sun’s super-heated outer atmosphere, or corona.
“While we have many missions dedicated to studying the sun from afar, we have never, ever had a mission to get this up close and personal,” said Thomas Zurbuchen, head of NASA’s Science Mission Directorate.
Parker’s equations predicted the solar wind, but six decades later, scientists can’t precisely explain the physics driving its acceleration or the corona’s extreme heating.
The corona, visible from Earth during last year’s total solar eclipse as a fiery glow around the sun with wispy bands stretching outward, is far hotter than the roiling surface below it.
“We’re used to the idea that if I am standing next to a campfire, and I walk away from it, it gets cooler,” said Alex Young, a solar scientist at NASA’s Goddard Space Flight Center in Maryland. “But this is not what happens on the sun. As we go from the surface of the sun, which is 10,000 degrees, and quickly move up into corona, we find ourselves quickly at millions of degrees.”
It’s also unknown what causes the solar wind to accelerate from a steady breeze to a supersonic flow, or what sparks violent solar storms that eject blobs of material at millions of miles per hour.
Theories have proposed waves and nanoflares, or a combination of them.
Pinning down those processes will advance understanding of how all stars work. It could also improve predictions of so-called space weather, which can damage satellites, endanger astronauts and disrupt power grids on Earth.
“It’s of fundamental importance for us to be able to predict space weather much like we predict weather here on Earth,” said Young.
The Parker Solar Probe is equipped with four instrument suites to measure plasma, magnetic and electrical fields and energetic particles, and to image the regions the spacecraft is about to fly through.
The probe will charge into the sun’s corona behind what engineers have nicknamed its “Eight-Foot Frisbee” — a heat shield measuring eight feet across and just four-and-a-half inches thick.
Consisting of two layers of carbon-carbon composite sandwiched around carbon foam, the front of the shield, coated with white ceramic paint, will withstand temperatures up to 2,500 degrees Fahrenheit. In the Frisbee’s shadow, the spacecraft’s body and most of its instruments will stay a comfortable 85 degrees.
How can the spacecraft survive in a region reaching millions of degrees?
“The corona is very tenuous plasma,” said Nicola Fox, the mission’s project scientist from the Johns Hopkins Applied Physics Laboratory in Baltimore. “If you think of putting your oven on and you set it at 400 degrees, and you can put your hand inside your oven and you won’t get burned unless you actually touch a surface. And it really is the same.”
But the Parker Solar Probe features multiple technologies to cope with the heat threat. It’s the first spacecraft to actively cool solar array wings that are critical to generating power, and onboard sensors will react if any sensitive areas are exposed to excessive heat, commanding the probe to adjust its position.
Such automation is needed because sunlight takes eight minutes to reach Earth 93 million miles away. There’s not enough time for engineers to receive signals, process them and return instructions before a problem could prove catastrophic.
“She has to be able to look after herself,” Fox said of the probe.
By the time of its closest approach to the sun’s surface, the Parker Solar Probe will be traveling at 430,000 mph, making it the fastest human-made object ever.
Mission scientists credited Eugene Parker with being the father of their field, heliophysics, calling him a superstar whose work underpins all of the mission’s objectives.
Parker said he’s particularly interested in learning more about the heating that occurs during explosive solar flares and storms.
“I suspect it’s going to be complicated, and I suspect some of us will argue with each other as to exactly what’s going on,” he said before the launch. “But you’ve got data to work with, and you have a chance of getting it straightened out.”
Sunday’s flight of his namesake mission was the first rocket launch Parker had seen in person, an experience he likened to seeing the Taj Mahal up close rather than in pictures or on TV.
“Somehow when you’re looking at the real thing, it’s quite impressive,” he told NASA TV.
Sunday’s mission was United Launch Alliance’s sixth of the year, and the third countdown in less than six days on the Eastern Range, starting with SpaceX’s early Aug. 7 launch of an Indonesian satellite.
SpaceX is expected to shoot for its 16th launch of the year in the next two weeks, with a Falcon 9 rocket carrying a Canadian communications satellite.
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