The sun's gravity will accelerate the spacecraft to record-breaking speeds during such encounters; at its fastest, the Parker Solar Probe will go about 430,000 miles per hour (690,000 km/h), NASA officials said. The launch window for the mission now closes on August 23.
NASA postponed until Sunday the launch of the first ever spacecraft to fly directly toward the Sun on a mission to plunge into our star's sizzling atmosphere and unlock its mysteries.
In the lead-up to the launch, NASA collected 1.1 million names from members of the public who wanted to symbolically orbit the sun at close range.
If it launches successfully at the same time on Sunday, the probe will reach speeds of up to 430,000 miles per hour (700,000 km/h).
The car-sized Parker Solar Probe is scheduled to blast off on a Delta IV Heavy rocket from Cape Canaveral.
The launch of the Parker Solar Probe will set it on a journey all the way to the Sun's atmosphere, or corona - closer to the Sun than any spacecraft in history.
The Parker probe will swing close to the sun, then out around Venus, and back again, 24 times over the next seven years.More news: Samsung Galaxy Note9 is up for pre-order in India
More news: Alaska Airlines reports stolen aircraft, witnesses report chase
More news: Transfer: Manchester United in talks to sign Chelsea defender
The problem had to do with the gaseous helium pressure alarm on the spacecraft, officials said early today.
The spacecraft eventually will run out of fuel and, no longer be able to keep its heat shield pointed toward the Sun, will burn and break apart - except perhaps for the rugged heat shield.
"We'll be going where no spacecraft has dared go before - within the corona of a star", said project scientist Nicky Fox from Johns Hopkins University Applied Physics Laboratory.
The Parker Solar Probe, named after American solar astrophysicist Eugene Parker, will, as the U.S. space agency describes it, "touch the sun" as it flies within 3.9 million miles of the star's surface.
"It was just a matter of sitting out the deniers for four years until the Venus Mariner 2 spacecraft showed that, by golly, there was a solar wind", Parker said earlier this week.
The probe is protected by an ultra-powerful heat shield that is 4.5 inches (11.43 centimeters) thick. The current close-to-the-sun champ, NASA's former Helios 2, got within 27 million miles (43 million kilometers) in 1976. It's the first time NASA mission has been named after a living person.
But it can withstand 2,500 degrees Fahrenheit (1,370 degrees Celsius) as well as extreme radiation, thanks to its high-tech carbon.