Parker Solar Probe prepped for delivery to Kennedy Space Center
GREENBELT, MD — NASA’s Parker Solar Probe (PSP) is getting ready for its flight to space. The spacecraft is currently scheduled for launch in July or August of this year (2018). PSP is NASA’s long-awaited mission to explore the Sun’s corona and is designed to discover more about the solar wind, and learn how conditions there interact to create space weather.
The spacecraft has just completed a final round of testing at Goddard, emerging from the thermal vacuum testing chamber on March 24. The chamber, called the Space Environment Simulator, mimicked the conditions the spacecraft should experience during its upcoming seven-year mission, in which it will travel within 3.9 million miles (6.2 million kilometers) of the Sun and endure temperatures of nearly 2,500 degrees Fahrenheit (1,377 degrees Celsius).
Members of the media were able to view the spacecraft from outside the cleanroom, where it is undergoing final preparations at Goddard before being carefully packed up for its flight to Florida this weekend. The spacecraft will go through its final integration and testing at the Astrotech Space Systems facility located in Titusville, Florida. Once this phase of processing is complete, the spacecraft will be launched from Cape Canaveral Air Force Station’s Space Launch Complex 37. PSP is scheduled to launch atop a United Launch Alliance Delta IV Heavy on July 31.
A mission team from Johns Hopkins University Applied Physics Laboratory (APL) designed the spacecraft. Partnered with NASA, the APL team and its industry partners have built a spacecraft that should make some 24 orbits around the Sun. The orbits should take PSP eight times closer to the Sun than any previous spacecraft. Such close encounters with the Sun will put PSP well within harm’s way of some very big events in the heliosphere, such as coronal mass ejections.
Nicky Fox, a PSP Mission Project Scientist, has no reservations about such encounters.
“We’re designed to see these big events,” Fox told Spaceflight Insider. “I’m actually more concerned that we might only see a quiet Sun. What I really want is to see everything. I hope we’re really up close when we see something big.”
PSP could help answer some of the biggest questions about the Sun. Those questions can only be answered by sending a probe directly into the corona.
“Why are we flying to the corona? Because that’s where all the magic happens,” Fox said. “It’s not just beautiful, it’s also the home of two big mysteries. One is that that big coronal material that you see in an eclipse is actually about 300 times hotter than the surface of the Sun. And that just shouldn’t happen. It breaks the laws of nature.” Fox described how a person walks away from a camp fire and gets colder instead of warmer. But in the Sun’s corona, the opposite happens.
“The other thing that happens there is the solar wind and coronal material suddenly become incredibly energized, so much so that it can break away from the giant pull of the Sun and bathe all of the planets,” Fox said, explaining that it is important for us to understand such ejections because it carries the Sun’s magnetic field with it and interacts with Earth’s magnetic field and causes space weather. Gaining a better understanding of these phenomena in the coronal region would allow us to fully model the Sun and its effect on Earth.
“We really don’t know what causes the heating in the corona,” Fox said. “We don’t know what causes the solar wind to be suddenly accelerated. We don’t know what causes all these issues. Once we know the real physics and put the real equations into that model, then we’ve made transformational improvements in our ability to predict space weather. So it really is the last piece of the puzzle.”
PSP is planned to collect this data through four main instruments. The Fields Experiment (FIELDS) is designed to measure the electric and magnetic fields and waves, absolute plasma density and electron temperature, and radio emissions.
Meanwhile, the Integrated Science Investigation of the Sun (ISOIS) will observe energetic electrons, protons and heavy ions that are accelerated to high energies in the Sun’s inner heliosphere, and correlate them with solar wind and coronal structures.
The Wide-Field Imager for Solar Probe (WISPR) will record images of the corona and inner heliosphere, solar wind and shock events, and provide measurements to complement other instruments. The Solar Wind Alphas and Protons (SWEAP) Investigation will count the electrons, protons, and helium ions in the solar wind and measure their velocity, density, and temperature.
This suite of instruments should yield a wealth of data about the Sun’s corona and its solar wind, protecting them from the 2,500 degree Fahrenheit (1,377 degrees Celsius) temperatures will be the job of a special heat shield. The 4.5-inch (11.43 cm) thick carbon-composite shield, is attached to one end of the spacecraft, acting more as a “shade” than a shield. Having said that, it is all that stands between the unrelenting heat of the Sun and the instruments.
“The heat shield is various forms of carbon,” Lead Thermal Protection System Engineer Betsy Congdon told Spaceflight Insider. “It’s a lot like a honeycomb panel you might find in an airplane, or on some of the panels of our spacecraft. There are two face sheets that are carbon-carbon, which is basically a superheated version of graphite epoxy that you might find in your golf clubs or your tennis rackets. And then in between there is a carbon foam. And it’s all bonded together using basically a carbon slurry.”
The main heat shield body was built at Carbon-Carbon Advanced Technologies in Kennedale, Texas. The white coating on the front of the heat shield, the part that will face the Sun, was sprayed on by Plasma Processes, Inc. in Huntsville, Alabama. The heat shield has brittle properties and so was tested at Goddard in its own thermal vacuum chamber, separate from the rest of the spacecraft, to avoid unnecessary damage to the shield.
During its seven-year mission, when its elliptical orbit takes it nearest the Sun, the spacecraft must be carefully oriented so that the shield is always keeping the instruments shaded from the direct heat of the Sun. Even the spacecraft’s solar panels are designed to fold downward like flaps so that only the tips of the panels are outside the shade of the shield during these close passes. During its closest approaches, PSP will be travelling some 450,000 miles (724,000 km) per hour. Despite these incredible speeds and the intense heat of the Sun, the shielded instruments should experience temperatures of no greater than 80 degrees Fahrenheit (27 degrees Celsius).
At the end of the initial seven-year mission, PSP should have sufficient fuel to keep the spacecraft operational for many years afterward. This will increase its chances to observe all manner of coronal and heliospheric events and phenomena.
“If humanity wants to live or spend significant time in space, we need to have a better understanding of that space environment,” PSP Project Manager Andy Driesman told Spaceflight Insider. “Right now we don’t have the ability to make very good predictions. We don’t understand space weather events. We have satellites that will take corrective actions. Power grids will do things differently depending on space weather, and so being able to predict it better will be important for our satellite communications, our telephone networks, and our power systems going forward.”
Formerly referred to as the Solar Probe Plus, the spacecraft was renamed the Parker Solar Probe last year in honor of astrophysicist Eugene Parker. Among his work in the field, he is noted for his theory about the superheating of the solar atmosphere.
Video courtesy of NASA Goddard
Michael Cole is a life-long space flight enthusiast and author of some 36 educational books on space flight and astronomy for Enslow Publishers. He lives in Findlay, Ohio, not far from Neil Armstrong’s birthplace of Wapakoneta. His interest in space, and his background in journalism and public relations suit him for his focus on research and development activities at NASA Glenn Research Center, and its Plum Brook Station testing facility, both in northeastern Ohio. Cole reached out to SpaceFlight Insider and asked to join SFI as the first member of the organization’s “Team Glenn.”