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article imageTech and science will keep the Parker Solar Probe from melting

By Karen Graham     Jul 21, 2018 in Science
On August 6, 2018, NASA's Parker Solar Probe will launch to travel closer to the Sun, deeper into the solar atmosphere, than any mission before it. Cutting-edge technology and engineering will help it beat the heat.
On July 20, 2018, Nicky Fox, Parker Solar Probe's project scientist at the Johns Hopkins University Applied Physics Lab in Laurel, Maryland, and Alex Young, associate director for science in the Heliophysics Science Division at NASA's Goddard Space Flight Center in Greenbelt, Maryland, introduced Parker Solar Probe's science goals and the technology behind them at a televised press conference from NASA's Kennedy Space Center in Cape Canaveral, Florida.
"We've been studying the Sun for decades, and now we're finally going to go where the action is," said Young. How close will the probe actually get to the sun? If the Earth was at one end of a yard-stick and the Sun at the other, Parker Solar Probe will make it to within four inches of the solar surface, writes Science Daily.
Engineers at the Johns Hopkins University Applied Physics Laboratory in Laurel  Maryland  work on NA...
Engineers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, work on NASA’s Parker Solar Probe spacecraft. Parker Solar Probe will be the first-ever mission to fly directly through the Sun’s atmosphere.
The robotic spacecraft - the size of a small car, is slated to launch from Cape Canaveral, Florida on August 6, on a seven-year mission. The probe will fly into the Sun’s corona within 3.8 million miles (6.1 million kilometers) from the solar surface, seven times closer than any other spacecraft.
“To send a probe where you haven’t been before is ambitious. To send it into such brutal conditions is highly ambitious,” said Fox at the news conference. The only other probe to make a close pass by the sun was Helios 2 in 1979. Helios 2 came within 27 million miles (43 million kilometers). The Parker Solar Probe will get much closer.
European Space Agency
Scientific goals to be achieved
The sun is vital to our existence, however, as CBC Canada notes, it's not really our ally. It is a roiling, churning ball of gas and charged particles that generate a solar wind that influences our planet — and not always in a good way.
The Parker Solar Probe is part of NASA’s Living With a Star program to explore aspects of the sun-Earth system that directly affect life and society. And while there are hundreds of questions that we could ask about our star, NASA wants the probe to get close enough to answer "three important questions."
Why is the sun's surface, called the photosphere, not as hot as the sun's atmosphere, or corona? It may sound strange, but the surface of the sun is only 10,000 degrees Fahrenheit while the atmosphere above the surface is about 3.5 million degrees Fahrenheit.
On August 31  2012 a long filament of solar material that had been hovering in the sun s atmosphere ...
On August 31, 2012 a long filament of solar material that had been hovering in the sun's atmosphere, the corona, erupted out into space at 4:36 p.m. EDT.
By NASA Goddard Space Flight Center via Wikimedia Commons
How does the solar wind get its speed? "The sun blows a stream of charged particles in all directions at a million miles an hour," Eric Christian, a NASA research scientist said in May, reported Digital Journal "But we don't understand how that gets accelerated."
Scientists also want to know why the sun occasionally produces high-energy particles known as solar energetic particles. These particles are a danger to astronauts and spacecraft. Scientists hope the mission will provide data on solar activities that could affect our ability to forecast space-weather events that can impact life on Earth.
Solar Variability Affecting Earth. Incidents range from solar flares  sunspots.
Solar Variability Affecting Earth. Incidents range from solar flares, sunspots.
Technology will keep the probe from melting
So, why won't the Parker Solar Probe melt when it gets close to the sun? The answer lies in the technology available today, in the form of a special heat shield and an autonomous system that includes a solar array cooling system and onboard fault management systems.
One key to understanding how the systems work is understanding the concept of heat versus temperature. In other words, high temperatures do not always translate to actually heating another object.
Holding your hand in a hot oven is easier than sticking your hand in a pot of boiling water.
Holding your hand in a hot oven is easier than sticking your hand in a pot of boiling water.
Arnold Reinhold
OK, now pay attention. Temperature measures how fast particles are moving. In turn, heat measures the total amount of energy they transfer. So look at it this way - If there are particles moving fast, but there are very few of them, they won't transfer very much energy, resulting in low heat.
So, because space is empty - there aren't very many particles to hit the spacecraft. Following along this same train of thought, when the probe goes through the sun's corona - which has an extremely high temperature but very low density - the spacecraft will interact with fewer hot particles and won't receive as much heat.
It's sort of like holding your hand in the middle of a hot oven, You can feel the heat, but you don't feel that uncomfortable because the atmosphere around your hand is not dense. But stick your hand in a pot of boiling water, where the particles make the medium very dense, and you will get burned.
The Delta IV is a rocket operated by United Launch Alliance. The one that ill be used for the Solar ...
The Delta IV is a rocket operated by United Launch Alliance. The one that ill be used for the Solar Probe Plus mission will be a Delta IV Heavy.
The temperature the solar probe has to withstand is still very hot, with the surface of the heat shield that faces the Sun only getting heated to about 2,500 degrees Fahrenheit (about 1,400 degrees Celsius). Parker's heat shield, called the Thermal Protection System, or TPS, is 8 feet (2.4 meters) in diameter and 4.5 inches (about 115 millimeters) thick.
This carbon-composite shield will also protect Parker and its delicate instruments from the extreme coldness of space as it travels to the sun. The TPS adds only about 160 pounds to Parker Solar Probe's mass because of its lightweight materials.
The launch is all in the timing
The timing of Parker Solar Probe's launch – between about 4 and 6 a.m. EDT, and within a period lasting about two weeks – was very precisely chosen to send the Parker Solar Probe toward its first, vital target for achieving such an orbit: Venus. The launch vehicle is the Delta IV Heavy, one of the world’s most powerful rockets.
A look at the orbit of the Parker Solar Probe.
A look at the orbit of the Parker Solar Probe.
NASA/Johns Hopkins APL
“The launch energy to reach the Sun is 55 times that required to get to Mars, and two times that needed to get to Pluto,” said Yanping Guo from the Johns Hopkins Applied Physics Laboratory, who designed the mission trajectory. “During summer, Earth and the other planets in our solar system are in the most favorable alignment to allow us to get close to the Sun.”
If everything goes as planned, after being launched on August 6, the probe should arrive safely on Nov. 1. It will then begin its 88-day orbit of the sun that will take it out past Venus. At its closest approach, which will be in 2024, Parker will be traveling 692,000 kph.
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