The powerful rocket is needed to propel the payload, NASA's Parker Solar Probe, to the sun.
The project was proposed in the year 1958 to a brand-new Nasa, and "60 years later, and it's becoming a reality", said project manager Andy Driesman, also of Johns Hopkins, which designed and built the spacecraft.
Nasa counted down on Friday (Aug 10) to the launch of a US$1.5 billion (S$2 billion) spacecraft that aims to plunge into the Sun's sizzling atmosphere and become humanity's first mission to explore a star.
"The solar corona is one of the last places in the solar system where no spacecraft has visited before", Parker Solar Probe scientist Adam Szabo said in a statement. Although the corona reaches millions of degrees, it's a wispy, tenuous environment and so the spacecraft won't need to endure such severe temperatures. It's the first time NASA has named a spacecraft after someone who's still alive.
It is a fast-paced mission, with the first Venus encounter occurring less than two months after liftoff, in early October, and the first brush with the Sun in November.
The Delta IV Heavy's launch window opens at 3:33 a.m. Saturday.
In all, the spacecraft will make 24 elongated laps around the Sun, closer than the orbit of Mercury, the innermost planet.
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"You know something exciting is just around the bend, but where you're sitting you can't see what that is", Fox said. But these findings are going to take a long time - first, the Parker probe will have to orbit around the sun, getting closer and closer, for as many as seven years.
The car-sized probe, which will fly closer to the sun than any other man-made object, is set to blast off at 3:33am eastern daylight time (8:33am BST) from Cape Canaveral, Florida on August 11.
Image: The spacecraft can withstand enormous heat. And it needs to be, because it takes an huge amount of energy to get to our final orbit around the Sun.
A LEARNING OPPORTUNITY. Ultimately, the more we can learn about the Sun, the better.
The probe, named after American solar astrophysicist Eugene Newman Parker, is set to use seven Venus fly-bys over almost seven years to steadily reduce its orbit around the Sun, using instruments created to image the solar wind and study electric and magnetic fields, coronal plasma and energetic particles.
Though the side facing the Sun will reach 2500F, the probe itself will be cooler at 85F, says NASA.