NASA's Parker Solar Probe, mankind's first mission to "touch" the Sun, was successfully launched today on an unprecedented, seven-year long journey to unlock the mysteries of the star's fiery outer atmosphere and its effects on space weather.
At closest approach, when the probe will hurtle around the Sun at approximately 700,000 kilometres per hour, the front of the solar shield will face temperatures approaching 1,377 degrees Celsius.
ULA's Delta IV Heavy is ULA's most powerful rocket with three common booster cores and capable of 2.1 million pounds of liftoff thrust.
The Solar Probe will fly as close as 3.8 million miles to the sun - more than seven times closer than any spacecraft has come before - revolutionising our understanding of the sun's atmosphere.
NASA needed the mighty 23-story rocket, plus a third stage, to get the Parker probe - the size of a small auto and well under a ton - racing toward the sun, 93 million miles (150 million kilometers) from Earth.
If all goes well, the Parker Solar Probe will fly straight through the wispy edges of the sun's corona, or outer atmosphere, in November.
During its closest approach to the sun, the Parker Solar Probe will leave other speedy spacecraft eating metaphorical dust.
NASA has billed the mission as the first spacecraft to "touch the Sun". We've studied it from missions that are close in, even as close as the planet Mercury.
When it nears the Sun, the probe will travel rapidly enough to go from NY to Tokyo in one minute - some 430,000 miles per hour, making it the fastest human-made object.
A mission to get up close and personal with our star has been on NASA's books since 1958.
The $1.5bn (£1.17bn) project is created to give scientists a better understanding of solar wind and geomagnetic storms that risk wreaking chaos on Earth by knocking out the power grid.
These solar outbursts are poorly understood, but pack the potential to wipe out power to millions of people.
A worst-case scenario would cost up to two trillion dollars in the first year alone and take a decade for full recovery, experts say. It will make 24 passes through the corona during its seven-year mission.
A highly advanced heat shield just 4.5 inches (11.43 centimeters) thick was devised to keep the probe from melting.
Weighing just 635 kgs, it is a relatively light spacecraft, Andy Driesman, project manager for the mission at the Johns Hopkins University Applied Physics Laboratory in the U.S., said in an earlier statement.
"Wow, here we go".
Thousands of spectators turned up at the launch site on Sunday, including Eugene Parker, the 91-year-old astrophysicist the spacecraft is named after.
The 8-foot (2.4-meter) heat shield will serve as an umbrella that will shade the spacecraft's scientific instruments, with on-board sensors adjusting the protective cover as necessary so that nothing gets fried.
Tools on board will measure high-energy particles associated with flares and coronal mass ejections, as well as the changing magnetic field around the Sun.
A Saturday morning launch attempt was foiled by last-minute technical trouble.
But Sunday's bid "went off like clockwork", said NASA launch manager Omar Baez.