CAPE CANAVERAL, Fla. — NASA successfully launched humanity’s first probe to the sun on Sunday, kicking off a daring seven-year mission to better understand Earth’s closest star.
The Parker Solar Probe, carried on United Launch Alliance’s (ULA) Delta IV Heavy rocket, blasted off from Space Launch Complex 37 on Cape Canaveral Air Force Station at 3:31 a.m., a day after it was originally scheduled to launch.
The Parker Solar Probe will get as close as 3.83 million miles from the sun’s surface, which is about 95 percent of the way to the surface from Earth and is within the outer atmosphere known as the corona.
In the dark of predawn Sunday, as a T-10 countdown was broadcast to spectators watching on the NASA Causeway, the Delta's engines sparked to life and ignited the excess hydrogen around it.
Emerging from the fireball, the rocket began its journey before briefly being shrouded by a stray cloud. As the rocket continued upward, the ground trembled with the engine's roar.
At 3:37 a.m., as the rocket engine's glimmer faded into the night sky, the loudspeaker announced the boost phase was complete and the Parker probe was continuing its journey to the sun.
About 46 minutes into the journey, after losing telemetry for a short period, spacecraft separation from the rocket was confirmed, marking a successful launch.
Thomas Zurbuchen, NASA's associate administrator for the Science Mission Directorate, said after the launch that it was "textbook" save the telemetry "hiccup."
"It was a really clean launch," Zurbuchen told reporters Sunday. "I've never seen a Delta IV Heavy, and so for me, all this fire is — of course everybody told me, 'Don't get nervous, that's how it has to work.' And I read it in books too, but you see it there, and it's like, you know."
Sunday's successful launch comes after a last-minute technical issue with the rocket caused Saturday's originally planned launch to be scrubbed.
At four minutes before liftoff Saturday, there was a helium pressure alert, prompting a hold on the launch. About 20 minutes later, the team gave the all clear to proceed.
But with just one minute, 55 seconds to go before Saturday's new launch time, the team halted the launch again, running out the clock on that day's 65-minute launch window.
The probe is named after Gene Parker, who in 1958 wrote a paper theorizing the expansion of the solar atmosphere and solar wind. Parker was on hand to watch the launch of the namesake mission, which is NASA’s first to be named after a living person.
Among the questions NASA is seeking to answer is why the sun's corona is hotter than its surface, as well as why its atmosphere is continually expanding and continually accelerating away from the star.
The probe is equipped with a 4 1/2–inch thick carbon-carbon composite heat shield designed to withstand temperatures of about 2,500 degrees Fahrenheit. The shield took more than a decade to develop and 18 months to build.
The probe will make at least 24 passes around the sun, with gravity assists from Venus for seven of them, and continue going as long as it has propellant. When it runs of fuel, it will stay in the sun’s orbit in perpetuity.
The mission also set one speed record and is expected to set another. The first happened during launch, when the rocket became the fastest object ever to leave Earth at 43,000 miles per hour. The second is expected during the probe’s closest passes around the sun, becoming the fastest manmade object ever at 430,000 miles per hour.
Zurbuchen said the next highlight on the mission after the launch will be the probe's first pass by Venus in about eight weeks.
"Some of the instruments we have, we've never been to Venus with, so we think we can get data of the emissions from Venus, what's coming off the planet and its interaction with the solar wind in a way we've never done it before," he said.
In the lead-up to the launch, NASA collected 1.1 million names from members of the public who wanted their names to orbit the sun at close range. The names were uploaded to a memory drive that is being carried by the probe.
The launch also provided ULA a showcase for its Delta IV Heavy rocket at a time when the defense contractor is facing increasing competition from SpaceX.
ULA previously had a monopoly on the Air Force's Evolved Expendable Launch Vehicle program for launching sensitive payloads into space.
In February, SpaceX made headlines when it successfully launched its Falcon Heavy rocket. At more than double the power of the ULA Delta IV Heavy, the Falcon Heavy is the world’s most powerful commercial rocket and gives SpaceX the ability compete for contracts to launch larger spy satellites.
Ahead of Saturday's launch, ULA CEO Tory Bruno downplayed the importance of the Parker mission to the ULA-SpaceX competition.
"It's really no different for us," Bruno told a small group of reporters Friday. "All the launches are high-profile — this one's a little extra high. They're all, every one of them is important. I mean, we fly one-of-a-kind missions very often."
Updated at 4:55 a.m.