On August 12, 2018, Eugene Newman Parker was at Cape Canaveral. He watched as the Delta IV launch vehicle carried the Solar Probe research vehicle into space. 70 years earlier, Eugene Parker was the first scientist to suggest the existence of the solar wind and described the shape of the magnetic field in the outer solar system (later this shape was called the Parker spiral). And now NASA has named the apparatus designed to explore the Sun after a physicist — for the first time doing this in honor of a living person.
Realization After 70 Years
A series of missions to the Sun were proposed as early as 1958. One that involved exploring space inside the orbit of Mercury to investigate particles and magnetic fields in the vicinity of our star was among them. And then decades of research passed, which only confirmed the need to “probe” the Sun up close. But everything was broken about the price of the issue.
As a rule, when we talk about very complex, long-term missions, in our imagination there is a device flying somewhere to the outskirts of the solar system, performing gravity maneuvers around Jupiter and traveling in the cold of space for decades. However, launching a probe to the very center of our piece of the world is no easier or cheaper.
It is ironic that when it came to developing a mission to the Sun, it was originally supposed to launch it to… Jupiter. Yes, in the opposite direction, so that with the help of the gravity of the giant planet, enter the polar solar orbit. However, this option was abandoned, because in this case the apparatus would need a radioisotope generator and eight years to reach the first perihelion (the point of the orbit closest to the Sun). Also, the probe would approach very close to the surface of the star, and this would increase the cost of thermal insulation.
As a result, in the early 2010s, after NASA experienced a radical reduction in the budget, the Solar Probe Plus mission was developed. In it, Venus served as the “upper stage” of the spacecraft — several flights around the planet made it possible not only to gain a large one, but also to correct the orbit. In addition, such maneuvers made it possible to achieve a higher perihelion and, consequently, to reduce the requirements for thermal insulation. However, even with such reductions in cost, Solar Probe Plus cost NASA one and a half billion dollars.
Let Take the Heat!
Of course, high temperature and solar radiation are the main problems of the Parker Solar Probe. The probe should be the first spacecraft in history to fly into the solar corona — a little more than six million kilometers (3.7 million miles) from the surface of the star. Scientists hope not only to learn more about the physics of the Sun, the origin of our star, but also to learn how to predict astronomical events that can affect life and technology on Earth.
At the closest perihelion, the probe will be exposed to radiation with a power of 650 kilowatts per square meter (10 square feet) — this is 475 times higher than in Earth’s orbit. The temperature will reach 1370 degrees Celsius (743 Fahrenheit) — more than on the sunny side of Mercury, the closest planet to the Sun. To prevent heat and radiation from destroying the probe, it has a thermal shield. This is real armor with a thickness of 11.4 centimeters (4.5 inches) made of reinforced carbon-carbon composite material. A reflective layer of Al2O3 aluminum oxide is deposited on the screen surface. All systems and scientific instruments are positioned to fall into the middle of the shadow formed by the screen, where the radiation is completely blocked.
The Parker Solar Probe must be very independent because it will not be possible to give it an operational command: the signal from the Sun to the Earth takes a little more than eight minutes. Niki Fox, a researcher at Johns Hopkins University’s Applied Physics Laboratory, called the probe “the most autonomous spacecraft ever launched.” Therefore, the device has four sensors, which, at the first sign of direct sunlight, give a command to turn the device, with the screen towards the radiation source.
Going For the Record
As already mentioned, the trajectory of the Parker Solar Probe is built in such a way as to perform gravitational maneuvers, flying around Venus. The device will approach the planet seven times in seven years, making a total of 24 revolutions around the Sun. In this case, at perihelion, the speed of the probe will be maximum, and at aphelion (the most distant point from the Sun) — minimum. At the same time, the period of circulation after each meeting with Venus decreases. If after the first meeting, having entered an elliptical orbit, Parker Solar Probe made a revolution around the star in 150 days, then after the seventh time — in just 88.
On November 5, 2018, the probe reached perihelion, at which the distance to the Sun was a record 15 million kilometers (9.3 million miles), and the speed was more than 90 kilometers (56 miles) per second. Beyond that, the Parker Solar Probe remained the fastest man-made spacecraft and beat its own records. In 2021, its speed reached 147 kilometers (91 miles) per second. When the probe reaches a perihelion of 6.2 million kilometers (3.85 million miles) in 2024, it is predicted to fly at a speed of 194 kilometers (120.5 miles) per second.
Now the Parker Solar Probe is on its thirteenth orbit around the Sun — on June 1, it reached perihelion for the twelfth time. The next time the probe will approach the Sun at a minimum distance on September 6th.