CAPE CANAVERAL, Fla. — NASA’s long-awaited Parker Solar Probe launched thunderously into the night sky atop a United Launch Alliance Delta IV Heavy rocket in the early morning hours of Aug. 12. Its goal? To unlock the secrets of Earth’s parent star.
The roughly seven-year mission got underway from Cape Canaveral Air Force Station, lifting off at 3:31 a.m. EDT (07:31 GMT). The sophisticated spacecraft has been produced to study the Sun’s corona region. Its sensitive instruments are designed to hopefully unlock many of the mysteries about how the corona is heated and how the solar wind is accelerated.
The mission has been a goal of NASA and the astrophysics community for decades.
“Parker Solar Probe is going to provide ground truth because we have never been at this location,” NASA Chief Scientist Jim Green told SpaceFlight Insider. “It is going to reveal the acceleration of the solar wind from where it is. It is going to reveal a whole series of phenomena from where they begin, like coronal mass ejections and flares. We are in solar minimum right now, and over the next seven or eight years we’re going to climb up to solar maximum. And that part of the solar cycle is where we see the coronal mass ejections. Three or four a week. This thing is going to get hammered! It’s going to be absolutely swimming in that stuff. It is going to be spectacular.”
The spacecraft is named after Eugene Parker, a renowned astrophysicist who originally theorized about the existence of the solar wind and many of the other coronal phenomena the spacecraft is expected to study. Parker is the first living person to have a NASA spacecraft named after him, and he was present for Sunday’s historic launch.
Originally slated to launch at 3:33 a.m. EDT (07:33 GMT) Aug. 11, sensor data had mission managers wanting more time to make sure there would be no issues before launch, prompting a 20-minute postponement. Consecutive issues resulted in a final attempt that day at 4:28 a.m. EDT (08:28 GMT). In the end, a gaseous helium red pressure warning saw hopes to get the spacecraft on its way dashed.
After a 24-hour turnaround, the launch team attempted again, this time successfully.
The Delta IV Heavy rocket sat on Space Launch Complex 37B through the night hours leading up to launch, bathed in spotlights and exuding the appearance of what it is—a mammoth and intimidating machine.
The three common booster cores (CBC) each measure 134 feet (40.8 meters) tall and 17 feet (5.1 meters) in diameter. With the Delta Cryogenic Second Stage (DCSS) stacked atop the center core and the spacecraft encapsulated at the top within its 62.7-foot (19-meter) tall payload fairing, the full stack stood an imposing 233 feet (68 meters) in height.
Fully fueled with liquid hydrogen (LH2) and liquid oxygen (LOX), the vehicle weighed more than 1,616,000 pounds (733,400 kilograms).
Fuel loading operations of the booster cores began about four hours, 30 minutes before liftoff with the LH2 tank chill downs and the beginning of LH2 loading some 20 minutes later. Over the course of the next 90 minutes, loading began on the booster core LOX tanks as well as the LH2 and LOX loading on the Cryogenic Second Stage.
With 50 minutes remaining in the countdown, engine spin start pressurization and gimbal steering checks were run on the booster cores’ RS-68A engines. At T minu 25 minutes, the weather briefing was favorable for continuing the countdown, which progressed without incident to its planned 30-minute hold at T minus four minutes. This allowed for a final weather update, after which the launch director conducted his final readiness poll before resuming the count.
As the count resumed, the vehicle was transferred to internal power. Over the next two minutes the booster cores’ LOX and LH2 tanks were secured at flight level and brought to flight pressure.
The countdown progressed steadily. One minute before liftoff, the Eastern Range verified “go” for launch. Some 35 seconds later came the “green board” call.
“We get everything ready and, essentially, everything on the rocket is secured, there are no steps or commands are going to the rocket,” United Launch Alliance’s Director and General Manager, Tony Taliancich, told SpaceFlight Insider before the launch. “Then we do all the polling. From the time that we poll the team and everything is ready and we’ll actually get to the position of handing everything over to a computer—that’s where the “green board” comes in.”
At 15 seconds before launch, “ROFI ignition” was called and the Radially Outward Firing Igniters, or “sparklers,” began sparking beneath the three booster core engine nozzles. These are intended for the LH2 gas that seeped out of the engine nozzles, as expected, at about T minus seven seconds. In this characteristic event of all Delta IV Heavy launches, the gas lingered momentarily around the bottom of the rocket, until about two seconds later when the sparklers ignited this excess LH2, creating a brief but dramatic fireball that charred the lower portion of the booster cores’ distinctive orange-and-white paint scheme.
In the next two seconds, the starboard booster core’s LOX valve opened, followed by the center and port boosters’ LOX valves. The engines rumbled to life, and at T minus 2 seconds roared to full thrust.
As the countdown reached zero, the hold-down clamps released and the Delta IV Heavy thundered slowly off the launch pad. The rocket lit up the night as it cleared the tower in the first 10 seconds. It then rose like a brilliant flare into the sky, obliterating the quiet as its mighty flaming thrust reverberated and crackled out over Florida’s Space Coast.
Twenty seconds into the flight, the rocket began to pitch over into its eastward arc, its fiery path remaining brightly visible as it headed far out over the Atlantic Ocean.
At about 44 seconds after liftoff the center booster core throttled down to 55 percent to conserve fuel before booster separation. About one minute later, the rocket’s velocity passed Mach 1, and shortly thereafter passed through the maximum aerodynamic pressure—Max-Q—phase of the flight.
About four minutes after the vehicle had left the pad, the port and starboard boosters separated at an altitude of about 50 miles (80 kilometers). The center booster core was now powering the vehicle into space at about 10,000 mph (16,000 kph) and had traveled 200 miles (320 kilometers) downrange.
Five minutes, 35 seconds into flight, the center booster engine cutoff. Seven seconds later the it separated and 13 seconds after that, the RL10B-2 engine of the DCSS ignited. At just over six minutes into flight, the payload fairing separated, exposing the Parker Solar Probe to space for the first time.
After burning for almost five minutes, the second stage engine cutoff, sending the vehicle into an orbital coast phase for about 12 minutes until the engine ignited again at about 23 minutes into the flight. This burn would start the spacecraft on its interplanetary trajectory, burning this time for over 14 minutes until the engine cutoff some 37 minutes into the flight. The second stage separated 30 seconds later.
For its historic mission to the Sun, the Parker Solar Probe required the services of a third stage Star 48BV solid rocket motor. Provided by Northrop Grumman, it was a dependable workhorse for the mission and successfully applied the final 1.5-minute boost.
The third stage’s final engine burn sent the probe on a unique trajectory that will feature seven gravity-assist flybys of Venus, with the first flyby set to occur on Oct. 2, 2018.
Even one of the most powerful launch vehicles currently in service and an impressive upper stage cannot send a spacecraft on a close orbit of the Sun from the Earth directly. The Venus flybys are required to shed extra energy off the spacecraft’s orbit. This is because, with its launch from Earth, the spacecraft is already carrying the Earth’s orbital velocity around the Sun—some 19 miles (32 kilometers) per second. Some of this energy must be shed if the spacecraft is to fall into the inner solar system toward the Sun.
The Venus flybys refine the spacecraft’s flight path for its 24 highly-elliptical orbits of the Sun. Each orbit will carry Parker Solar Probe deeper and deeper into the Sun’s coronal environment, and closer and closer to the surface of the Sun. The spacecraft is expected to come within 3.8 million miles (6.1 million kilometers) of the Sun’s surface—eight times closer than any previous spacecraft.
“In 1958 the National Research Council had a Space Studies Board,” Project Scientist Adam Szabo told SpaceFlight Insider. “After the first satellite was launched, they said ‘okay gentlemen, we can go to space.’ And they asked, ‘what shall we do there?’ And these questions about the Sun, this mission, was on their top 10 list. This was identified from the get-go of the space age that these are questions that we need to answer. We can’t move forward without answers about the corona and the solar wind.”
Despite all these energy-shedding maneuvers, when the spacecraft makes its closest pass of the Sun it will be traveling at more than 430,000 miles (692,000 kilometers) per hour, making it the fastest spacecraft ever built.
While Parker Solar Probe collects its data within the coronal region of the Sun, its instruments will be protected from the incredible heat by a unique eight-foot-wide carbon composite heat shield, which acts as a shade to the equipment behind it. The spacecraft’s solar arrays feature a special water-cooled design to withstand the intense temperatures in the Sun’s corona. When the probe makes its closest passes of the Sun, the arrays will be folded back so that only their outer tips are exposed to the Sun’s heat, while the rest is protected in the shade of the heat shield.
The instruments aboard Parker Solar Probe should allow the science teams to collect data on the Sun’s corona and the solar wind that they have never been able to collect before. That data should shed light on many of the mysteries about this largely unknown and poorly understood region of the Sun.
“We’ve looked at the Sun in every single different way that you can imagine,” said Project Scientist Nicky Fox at a recent press briefing, “Every wavelength. We’ve traveled inside the orbit of Mercury even. But we need to get into this action region, into the region where all of these mysteries are occurring. And that’s why we are doing this incredibly daring journey, going through the corona 24 times.”
Out of necessity for the distance the spacecraft will travel and the environment it will be in, it is designed with a high level of autonomy.
“I like to think of her as a very independent spacecraft,” Fox said. “She has to look after herself when she is in this coronal region. There is no person in the loop. She is fully capable of figuring out if there is an anomaly, how to rectify it. It takes light eight minutes to get from the Sun to the Earth. We don’t have time for her to send a signal, someone to think about it, and send a signal back. She has to be able to look after herself. These are the big technology leaps we’ve had to make. That is why we’ve had to wait 60 years for this mission.”
Parker Solar Probe’s 24-orbit mission will carry it through 2025, and is managed in partnership with NASA by Fox and her science team at the Johns Hopkins University Applied Physics Laboratory. As noted, new realms of knowledge stand to be opened as its mission unfolds.
“To do that, we have to go there,” Green said. “This thing is going to get buffeted by normal solar wind, by coronal mass ejections. It will see flares. It will map over huge Sun spots. There will be coronal holes. It will see variations all over the place. That provides us ground truth which other spacecraft will be able to put in the pictures and say, ‘ah, that’s what’s happening here.’ Hopefully that will give us the edge to start predicting, when we look at a sunspot’s characteristics, the probability it will erupt and when it will erupt.”
The next launch of a Delta IV Heavy rocket is scheduled for Sept. 26 at Vandenberg Air Force Base’s Space Launch Complex 6. The vehicle will orbit the classified NROL-71 payload for the U.S. National Reconnaissance Office. The payload is likely a Keyhole KH-11 image reconnaissance satellite.
Video courtesy of SpaceFlight Insider
Video courtesy of NASA