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By NASA // July 21, 2018
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ABOVE THE VIDEO: NASA's Parker Solar Probe is heading for the Sun. Why will not the spaceship melt?
(NASA) – This summer, NASA's Parker Solar Probe will launch to get closer to the Sun, deeper into the solar atmosphere, than any other mission. If the Earth was at one end of a bar and the Sun at the other, Parker Solar Probe would be traveling within four inches of the solar surface.
Inside this part of the solar atmosphere, an area known as the crown, Parker Solar Probe will provide unprecedented observations of what drives the wide range of particles, from Energy and heat that cross the region – throwing particles outward into the solar system and far ahead of Neptune.
Inside the Crown
The spacecraft will travel through materials with temperatures exceeding one million degrees Fahrenheit while being bombarded with intense sunlight.
If the Earth was at one end of a bar and the Sun at the other, Parker Solar Probe will be traveling within four inches of the solar surface. (NASA Image)
So why will not it melt?
Parker Solar Probe was designed to withstand the extreme conditions and temperature fluctuations of the mission.
The key lies in its personalized heat shield. autonomous system that helps protect the mission from the intense light emission of the Sun, but allows the coronal material to "touch" the spaceship
The science behind why it will not melt
A key to understand what keeps the spacecraft and its instruments are safe, that is to understand the concept of heat according to the temperature. Counter-intuitiveness, high temperatures do not always translate into a real warming of another object
In space, the temperature can reach thousands of degrees without providing significant heat to a given object or feeling hot. Why? Temperature measures the speed at which particles move, while heat measures the total amount of energy that they transfer. Particles can move quickly (high temperature), but if they are very few, they will not transmit much energy (low heat). As the space is usually empty, there are very few particles capable of transferring energy to the spacecraft.
The crown through which the Parker Solar probe passes, for example, has an extremely high temperature but a very low density. Think about the difference between putting your hand in a hot oven rather than putting it in a saucepan of boiling water (do not try it at home!) – in the oven, your hand can withstand temperatures much higher than in water it must interact with many more particles. Similarly, compared to the visible surface of the Sun, the corona is less dense, so that the spacecraft interacts with fewer hot particles and does not receive as much heat.
This means that Parker Solar Probe will travel in a space with temperatures of several million degrees, the surface of the heat shield facing the sun will only be heated to around 2500 degrees Fahrenheit (about 1400 degrees Celsius) .
The Shield That Protects It
Of course, thousands of degrees Fahrenheit is still incredibly hot. (For comparison, volcanic eruptions can range from 1,200 to 2,200 F (1,200 to 1,200 C.) To resist this heat, Parker Solar Probe uses a thermal shield known as a thermal protection system. With its few centimeters in diameter and its 4.5 inches (approximately 115 mm) in thickness, these few inches of protection mean that on the other side of the shield, the body of the spacecraft will remain at a comfortable temperature of 30 ° C (85 ° F). [19659010] The TPS was designed by the Johns Hopkins Applied Physics Laboratory, and was built at Carbon-Carbon Advanced Technologies, using a carbon composite foam plug sandwiched between two carbon plates.This lightweight insulation will be accompanied by a final touch of white ceramic paint on the plate facing the sun, to reflect as much heat as possible Tested to withstand temperatures ranging up to 1650 ° C, the TPS can handle all the heat that the sun can send, keeping almost all the instrumentation safe.
ABOVE THE VIDEO: [19659007] Johns Hopkins' Betsy Congdon Applied Physics Lab is the main thermal engineer on the heat shield that the NASA's Parker Solar Probe will use to protect against the sun. The shield is so sturdy that Congdon can use a blowtorch on one side and the other side stays cool enough to touch it.
The cup that measures the wind
But not all instruments Solar Parker Probe will be behind the TPS
Pushing the heat shield, the Solar Probe Cup is one of two instruments of the Parker solar probe which will not be protected by the heat shield. This instrument is what is called a Faraday cup, a sensor designed to measure the flow of ions and electrons and the flow angles of the solar wind. Due to the intensity of the solar atmosphere, unique technologies had to be designed to ensure that the instrument could not only survive, but also that on-board electronics could return accurate readings .
The cup itself is made of titanium zirconium-molybdenum sheets, a molybdenum alloy, with a melting point of about 4 360 F (2349 C). The chips that produce an electric field for the Solar Probe Cup are made from tungsten, a metal with the highest melting point of 6,192 C (6,192 F). Normally, lasers are used to burn the grid lines in these chips – but because of the high melting point, the acid must be used.
Another challenge came from electronic wiring – most cables would melt due to heat radiation. so close to the Sun. To solve this problem, the team developed sapphire crystal tubes to suspend the wiring and made the niobium wires.
To make sure the instrument was ready for the harsh environment, the researchers had to emulate the intense heat radiation from the sun. laboratory. To create a level of heat worthy of a test, the researchers used a particle accelerator and IMAX projectors – jury-rigged to increase their temperature. The spotlights mimicked the heat of the sun, while the particle accelerator exposed the cup to radiation to ensure that the cup could measure accelerated particles under intense conditions. To be absolutely sure that the Solar Probe Cup would withstand the harsh environment, the Odeillo solar furnace – which concentrates the sun's heat through 10,000 adjustable mirrors – was used to test the cut against the intense emission solar
The shield consists of two panels of carbon-carbon composite overheated sandwiching a core of lightweight carbon foam 4.5 inches thick. To reflect as much as possible the solar energy of the spacecraft, the side of the heat shield facing the sun is also treated with a specially formulated white coating. (NASA Image)
The Solar Probe Cup has passed its tests with flying colors – indeed, it has continued to perform better and to give clearer results, the more it has been exposed to test environments.
Contamination, "said Justin Kasper, principal investigator for SWEAP instruments at the University of Michigan at Ann Arbor." He's cleaned up on his own. "
The spacecraft that keeps its
Several other designs on the spacecraft keep Parker Solar Probe out of the heat.Without protection, the solar panels – which use the same star energy studied for powering the spacecraft – can overheat.As each approach to the Sun, the solar panels retract behind the shadow of the heat shield, leaving only a small segment exposed to the intense rays of the Sun.
But closer to the Sun, more protection is needed The solar panels have a surprisingly simple cooling system: a heating tank that prevents the coolant from freezing during the launch, two radiators that will prevent the refrigerant to freeze, aluminum fins to maximize the cooling surface and pumps to circulate the liquid. The cooling system is powerful enough to cool a medium sized salon, and will keep the solar panels and instrumentation cool and running during the hot sun.
Coolant used for the system? About one gallon (3.7 liters) of demineralized water. Although there are many chemical coolants, the temperature range at which the spacecraft will be exposed ranges between 50 F (10 C) and 257 F (125 C). Very few liquids can handle these beaches like water. To prevent water from boiling at the highest temperature, it will be pressurized so that the boiling point is greater than 125 ° C [125905] In the Titusville Astrotech Plant, in Florida, near the Kennedy Space Center of NASA. On Tuesday, June 5, 2018, technicians and engineers perform light bar tests on NASA's Parker Solar Probe. The spacecraft will be launched on a Delta IV rocket from the United Launch Alliance launched by Space Launch Complex 37 at the Cape Canaveral Air Station in Florida. The mission will make the closest observations of a star as it travels through the Sun's atmosphere, called the crown. The probe will rely on measurements and imagery to revolutionize our understanding of the crown and the Sun-Earth connection. (NASA Image)
Another problem with the protection of any spacecraft is how to communicate with it. Parker Solar Probe will be largely alone on its course. It takes eight minutes to light to reach the Earth, which means that if engineers were to control the spacecraft from Earth, it would be too late to fix it.
Thus, the spacecraft is designed to remain autonomous and safe. on the right track to the sun. Several sensors, about half the size of a cell phone, are attached to the body of the spacecraft along the edge of the heat shield's shadow. If any of these sensors detects sunlight, it will alert the central computer and the spacecraft will be able to correct its position to protect the sensors and the rest of the instruments. All this must be done without any human intervention, so the central computer software has been programmed and extensively tested to make sure that any corrections can be made on the fly.
Launch to the sun
After launch, Parker Solar Probe detect the position of the sun, align the heat shield to face it and continue its journey for the next three months, embracing the heat of the sun and protecting from the cold emptiness of space.
During the seven years of the planned duration of the mission, the spacecraft will make 24 orbits of our star. At each approaching approach to the Sun, he will sample the solar wind, study the Sun's crown, and offer unprecedented close-up observations around our star, and armed with his innumerable innovative technologies, we know that he will keep his blood- cold all the time.
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