Delta 4 Heavy PSP launch
A Delta 4 Heavy carrying NASA's Parker Solar Probe lifts off from Cape Canaveral, Florida, Aug. 12. Credit: NASA/Bill Ingalls

GENOA, Nev. — A NASA mission to travel closer to the sun than any previous spacecraft is on its way after a successful launch from Cape Canaveral Aug. 12.

The United Launch Alliance Delta 4 Heavy carrying NASA’s Parker Solar Probe mission lifted off from Space Launch Complex 37 at Cape Canaveral Air Force Station in Florida at 3:31 a.m. Eastern. Controllers scrubbed a launch attempt the previous day because of technical issues late in the countdown. The spacecraft separated from its kick stage 43 minutes after launch.

The 700-kilogram spacecraft required not only a Delta 4 Heavy but also a Star 48BV kick stage from Northrop Grumman in order to counteract the Earth’s rotational speed around the sun, allowing it to fall closer to the sun. The spacecraft will also perform a series of Venus flybys, starting in early October, to bring it closer to the sun.

Parker Solar Probe will perform its first close approach to the sun in November, coming within about 24.8 million kilometers. Future flybys will bring it even closer, eventually coming as close as 6.1 million kilometers, far closer than any previous spacecraft. During those later close approaches, the spacecraft will be traveling at up to 695,000 kilometers per hour.

Those close approaches are needed for Parker’s instruments to study the solar wind and the corona. By taking measurements from within the corona, scientists hope to better understand how it is heated to temperatures of millions of degrees. The up-close observations may reveal new information about solar eruptions and the solar wind.

“We know the magnetic field is the real key. We know this is why we’re making this daring mission,” said Nicola Fox of the Johns Hopkins University Applied Physics Laboratory, project science for the mission, during a pre-launch briefing Aug. 9. “We’re going to go into the transition from where the magnetic field is dominant to where that coronal material dominates the magnetic field.”

Development of Parker Solar Probe — previously known as Solar Probe Plus — dates back a decade, but the idea of sending a spacecraft close to the sun is far older. Concepts for missions to travel to the sun date back to the late 1950s, around the time that University of Chicago physicist Eugene Parker, for whom the mission is named, first proposed the solar wind.

Parker visits PSP
Eugene Parker (center), the namesake of the Parker Solar Probe, visits the Delta 4 Heavy launching the spacecraft along with NASA Associate Administrator for Science Thomas Zurbuchen (left) and United Launch Alliance CEO Tory Bruno. Credit: NASA/Bill Ingalls

“For the science community, and some of the engineering community, it’s really been 60 years,” said Andy Driesman, project manager for the mission, during the pre-launch briefing. “You can trace back papers and read engineering reports from the ’60s and ’70s about this mission, about different concepts, different ways to get this environment.”

What made the mission feasible was a set of technologies, including a heat shield that protects the spacecraft during its close approach to the sun as well as an active cooling system for the solar panels. The spacecraft also needed to be small enough that it could be launched on the desired trajectory.

“Certainly, finding the right materials” was key, said Fox. “It isn’t just a case of surviving the incredible heat when we’re close to the sun. We come out around Venus and it’s cold there, which means these materials have to withstand heating and cooling, very extreme changes in temperatures.”

Parker Solar Probe has a primary mission of 24 orbits around the sun through the middle of 2025. Driesman, though, said he was optimistic that the spacecraft could operate far longer. “As long as we have propellant on board, we’re going to continue to take science data,” he said.

The mission will ultimately end when the spacecraft runs out of attitude control propellant. “It will lose attitude control and those sensitive bits of the spacecraft, which we worked so hard to protect, will eventually transition to the sun,” he said. “The way I like to think about it is that, hopefully in a long, long period of time, 10 to 20 years, there’s going to be a carbon disk floating around the sun in its orbit. That carbon disk will be around until the end of the solar system.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...