A probe will voyage closer to the Sun than ever before.
Nasa’s Parker Solar Probe will be the first spacecraft to “touch” the Sun, coming within just 3.8 million miles of its surface.
It is designed to take solar punishment like never before, thanks to its revolutionary heat shield that is capable of withstanding 2,500F (1,370C).
Lift-off is set for the pre-dawn hours of Saturday for this first-of-its-kind mission to a star.
“The coolest, hottest mission, baby, that’s what it is,” said Nicola Fox, the project scientist at Johns Hopkins University.
Roughly the size of a small car, Parker will get nearly seven times closer to the Sun than previous spacecraft.
To snuggle up to the Sun, it will fly past Venus seven times over seven years. Each flyby will provide an orbit-shaping gravity boost, drawing it ever closer to the Sun and straight into the corona — the Sun’s outermost atmosphere.
The closer, the better for figuring out why the corona is hundreds of times hotter than the Sun’s surface.
Another mystery scientists hope to solve is what drives the solar wind. That is the steady, supersonic stream of charged particles blasting off the corona and into space in all directions.
“There are missions that are studying the solar wind, but we’re going to get to the birthplace,” Ms Fox said.
Scientists expect the 1.5 billion US dollar mission to shed light not only on our own dynamic Sun, but the billions of other yellow dwarf stars — and other types of stars — out there in the Milky Way and beyond.
This is a journey into never-never land
While granting us life, the Sun also has the power to disrupt spacecraft in orbit, and communications and electronics on Earth.
“This is where we live,” said Nasa solar astrophysicist Alex Young. “We have to understand and characterise this place that we’re travelling through.”
The project was proposed in 1958 to 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.
The technology for surviving such a close solar encounter, while still being light enough for flight, was not available until now.
Parker’s 8-foot (2.4-metre) heat shield is just four-and-a-half inches thick. Sandwiched between two carbon sheets is airy carbon foam. The front has a custom white ceramic coating to reflect sunlight; it’s expected to glow cherry red when bombarded by the extreme solar heat.
The spacecraft will hit 430,000 mph in the corona at closest approach. That is equivalent to going from Chicago to Beijing in under a minute.
This is the first Nasa spacecraft to be named after someone still alive.
Eugene Parker, 91, professor emeritus at the University of Chicago, predicted the existence of solar wind 60 years ago. He plans to be at Cape Canaveral for the launch. United Launch Alliance’s Delta IV Heavy rocket is providing the muscle.
Mr Parker got to inspect the spacecraft last autumn. He said he is holding his breath that everything goes well.
“This is a journey into never-never land, you might say, where it’s too hot for any sensible spacecraft to function,” Mr Parker said in a recent interview. “But some very clever engineering and construction have succeeded in making what looks like a very workable instrument.”
The spacecraft holds photos of Mr Parker as well as a copy of his 1958 research paper on what he termed solar wind. Despite scepticism, Nasa’s Mariner 2 spacecraft proved Parker right in 1962.
Also on board are more than a million names of space fans submitted to Nasa this past spring.