solar probe plus approaches sun illustration nasa
An illustration of NASA's Parker Solar Probe (previously called Solar Probe Plus) as it flies toward the sun.

  • NASA plans to launch a robot on Sunday that will fly closer to the sun than any mission in history.
  • A Saturday launch attempt was delayed due to a technical glitch.
  • The Parker Solar Probe will have to travel about 430,000 mph and use a high-tech heat shieldto survive the trip.
  • The probe is designed to study the sun's ultra-hot outer atmosphere, called the corona, among other mysteries of our star.
  • The mission may help scientists predict space weather events that can wreak havoc on Earth.

NASA is about to launch a $1.5 billion space mission to "touch" the sun and study its atmosphere, solar wind, and other mysteries.

The Parker Solar Probe (PSP) is scheduled to rocket toward space on Sunday, August 12. The launch was originally planned for Saturday, but an unspecified technical issue halted that attempt. Meteorologists say there's about a 60% chance the weather will cooperate for Sunday's launch at 3:31 a.m. EDT — though NASA can fly the probe as late as August 23.

When PSP does lift off from a launchpad in Cape Canaveral, Florida, it will ride atop a powerful Delta 4 Heavy rocket built by United Launch Alliance.

The Parker Solar Probe in the nosecone or fairing of a Delta 4 Heavy rocket.
NASA/Johns Hopkins APL/Ed Whitman
PSP is designed to survive sunlight 3,000 times more powerful than occurs at Earth and plow through a "solar wind" of high-energy particles. Outside the spacecraft, temperatures will get as hot as several thousand degrees.

And to achieve this mission, it will have to fly past the sun at about 430,000 mph, which is faster than any human object ever sent to space.

Its mission is to crack two 60-year-old mysteries: why the sun has a solar wind at all, and how the corona — the star's outer atmosphere — can heat up to millions of degrees.

"That defies the laws of nature. It's like water rolling uphill," Nicola Fox, a solar physicist at the Johns Hopkins University Applied Physics Laboratory, said during a NASA briefing in 2017.

"Until you actually go there and touch the sun, you can't answer these questions," said Fox, who's a project scientist for the new mission.

If the robot pulls off all the science that NASA and its partners hope, it might also help researchers learn critical information about solar outbursts that can overload power grids, cripple satellites, disrupt electronics, and inflict trillions of dollars' worth of damage in a matter of hours.

How to touch a star 24 times — and survive

NASA's Parker Solar Probe must withstand blistering temperatures and incredible speeds near the sun.
David McNew/Getty Images; NASA; JHUAPL; Jenny Cheng/Business Insider

Scientists plan to fly the Parker Solar Probe by our sun about 24 times over seven years. During the PSP's closest approach, it will come within 3.9 million miles of the star.

That distance is about four times the width of the sun itself, nearly 24 times closer than Earth is to the star, and seven times nearer than any spacecraft has ever dared travel to the sun. This dangerous proximity will enable PSP to record unprecedented measurements of the sun's corona, solar wind, magnetism, and other properties.

Pulling these flybys off isn't straightforward. To put PSP on the correct path, NASA will zoom its probe past Venus seven times, which will help it reach record-breaking speeds through space when it moves through the sun's corona. At that speed, you could travel from New York City to Tokyo in a minute.

The orbital path that NASA's probe needs to fly to "touch" the sun.
Johns Hopkins University Applied Physics Laboratory

The idea to do a mission like PSP started nearly 60 years ago. But temperatures reach about 2,500 degrees at the proximity scientists wanted to send a probe, so "the materials didn't exist" to make it happen, Fox said.

That changed recently with the development of a state-of-the-art, lightweight carbon composite. Engineers have crafted that material into a 4.5-inch-thick "ram" for the probe that will face the sun, absorb and deflect solar radiation, and protect a suite of gadgets behind it.

"Solar probe is going to be the hottest, fastest, and — as I like to call it — the coolest mission under the sun," Fox said.

Unraveling the mysteries of solar wind

An illustration of the Parker Solar Probe withstanding blasts of solar-wind particles.
NASA's Goddard Space Flight Center

Orbiting a star as close as Earth does means we live inside its atmosphere: a sea of moving particles, or solar wind, spews outward at about 1 million mph and bombards planets like ours.

Eugene Parker, an 89-year-old scientist after whom the probe was named, first discovered this solar wind in the mid-1950s. An editor of a science journal famously rejected his seminal paper in 1958 and scolded Parker — who was later found to be correct — for submitting it.

An illustration of Earth's magnetic field.

During the NASA briefing last year, Parker said he jokingly thought in 1958 that the editor "didn't have any real critique, so it must have been a really good paper."

Since then, physicists have wondered what, exactly, accelerates this stream of particles to breakneck speeds. They also question how the sun's atmosphere can jump from thousands of degrees Fahrenheit to millions of degrees in a tight region just above the star's surface.

"We want to go down there, take the challenge of going into the worst environment in the solar system and … really prove what the processes are that, in fact, make and accelerate the solar wind," Thomas Zurbuchen, the associate administrator of NASA's Science Mission Directorate, said last year.

Protecting Earth from violent solar outbursts

A solar flare and prominence erupting from the sun.
NASA Goddard Space Flight Center

Earth's magnetic field and atmosphere typically protect us from the solar wind.

However, the surface of the sun occasionally flings giant blobs of solar particles at us in events called solar storms or coronal mass ejections. This triggers the beautiful auroras at our planet's poles, but can also temporarily disturb Earth's magnetic field, which can in turn disturb electrical systems of all kinds.

While figuring out how to protect Earth isn't the main goal of PSP, researchers hope the mission equips heliophysicists (scientists who study the sun) with new information that can help them predict, characterize, and prepare the world for a potentially crushing solar blow.

"Until we can explain what is going on up close to the sun, we will not be able to accurately predict space weather effects that can cause havoc at Earth," states the mission's website.

Last year, NASA finished assembling the probe and put it through a brutal testing program (including sizzling-hot thermal exposure). It's now inside the Delta 4 Heavy rocket's fairing, or nosecone, and awaiting launch.

If all goes well after its launch, PSP should make its first pass of the sun in late 2018 and its final one in mid-2025.

This story was updated with new information. It was originally published on June 1, 2017.