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Solar Probe Plus gets green light to proceed

Artist's concept of the Solar Probe Plus craft during one of its gravity assists at Venus. Image credit: NASA/JHUAPL

An artist’s rendering of the Solar Probe Plus spacecraft during one of its planned gravity assists at Venus. Image credit: NASA / JHUAPL

NASA’s Solar Probe Plus has passed an important design review milestone and can now proceed to assembly and integration in preparation for its scheduled summer 2018 launch date. Currently comprising only a primary structure and propulsion system, the assembly can now move forward with the installation of the remainder of the spacecraft’s systems and science instruments.

Solar Probe Plus is slated to launch atop a United Launch Alliance (ULA) Delta IV Heavy during a 20-day window that opens on July 31, 2018. Though heading to study the Sun, the center of the Solar System, the craft will need to make use of several gravity-assist maneuvers with Venus in order to reach its desired orbit.

Engineers at the Johns Hopkins University Applied Physics Lab prepare the Solar Probe Plus spacecraft for testing. Photo credit: NASA/JHUAPL

Engineers at the Johns Hopkins University Applied Physics Lab prepare the Solar Probe Plus spacecraft for testing. Photo credit: NASA / JHUAPL

In all, the probe will make seven passes of Venus, over more than six years, to gradually reduce the craft’s perihelion (closest approach to the Sun) to approximately 8.5 solar radii, or 3.7 million miles (6 million kilometers). This will put the spacecraft well inside Mercury’s orbit.

Solar Probe Plus will hold the record for the closest solar pass, approaching nearly seven times closer than the current record holder, the Helios 2 spacecraft.

Although it will take six years and twenty-four orbits for the spacecraft to reach its intended final orbital configuration, Solar Probe Plus will make its first pass of Venus less than two months after launch and will begin collecting data on its first pass of the Sun one month after that.

The probe will gather data which should give scientists a greater understanding of the processes that heat the corona and accelerate the solar wind – the stream of charged particles constantly flowing from the Sun. During these close approaches, the spacecraft will experience temperatures nearing 2,500 degrees Fahrenheit (1,400 degrees Celsius).

It will be the job of the probe’s 4.5-inch (11.4-centimeter) thick carbon-composite heat shield to protect the spacecraft and its instruments from the searing conditions. It’s expected that while the heat shield is pointed toward the Sun and experiencing maximum heating (nearly 475 times greater than what spacecraft encounter in Earth orbit), the interior of the spacecraft will be at, or near, room temperature. Additionally, Solar Probe Plus must survive bombardment of radiation and energized dust at levels greater than any previous spacecraft.

Not only will the spacecraft experience brutally harsh conditions at perihelion, it will also be traveling at its fastest: approximately 450,000 miles per hour (724,205 kilometers per hour) relative to the Sun. At this speed, the probe would cover the distance from Earth to the Moon in a little more than half an hour – something that took roughly three days for the Apollo spacecraft.

Solar Probe Plus is a key part of NASA’s “Living With a Star” program and has – as a concept – been approximately 50 years in the making. “Living With a Star” was developed to help NASA understand more about the Sun, and how it interacts with the Solar System’s planets and inhabitants. The program is managed by NASA’s Goddard Spaceflight Center in Greenbelt, Maryland, with the spacecraft being managed and built by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.


Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.

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