The Crew Dragon spacecraft, produced by the private company SpaceX, is scheduled to return from the International Space Station (ISS) and take off for the Atlantic Ocean on August 2. With a favorable weather forecast and a successful final week on the ISS, NASA astronauts Robert Benken and Douglas Hurley will begin the unblocking process on August 1, and the next day will re-enter the Earth’s atmosphere – a total of 64 days after departure.
The historic launch took place on May 30 from NASA’s Kennedy Space Center in Florida, the first time a commercial space company has launched humans into orbit around the Earth. But while the launch was a nail biting review, revisiting will be even more risky ̵1; presenting a tense moment for mission control. SpaceX founder Elon Musk said repertoire was his biggest concern.
The joint mission of SpaceX and NASA was successful in docking with the ISS, allowing astronauts to perform scientific and technical work, including four space passages.
Importantly, the main purpose of the mission is to test and demonstrate the vehicle’s ability to safely transport its crew to Earth and Earth’s orbit as a first step in launching regular ISS missions and commercial spaceflight.
Danger points for re-entry
The extreme speed and temperature that the car must withstand is a serious problem for engineers and makes rebooting the most dangerous part of the mission.
The danger begins with finding the right angle of the trajectory when the spacecraft enters the upper atmosphere. If it is too steep, astronauts experience potentially deadly g-forces, and friction by air drag can cause a spacecraft to explode. If it is too shallow, instead the capsule will catastrophically slip out of the atmosphere and return to Earth’s orbit.
The spacecraft will enter the upper atmosphere at a speed of 27,000 km / h. This is 7.5 km / second, or 20 times the speed of sound. In any unit you will prefer – it’s fast. At this speed, a very strong shock wave is formed around the front of the car, compressing and overheating the air. Managing a huge heat load is a huge engineering problem.
At the most extreme stage, the air temperature in the impact layer exceeds 7000 ° C. For comparison, the temperature on the surface of the Sun is about 5500 ° C. This makes the car’s heat shield so hot that it begins to glow – a process called incandescence. The new and improved PICA-X heat shield from SpaceX managed to protect the capsule in test flights, later it was restored in a very charred condition.
The air molecules around the vehicle also break down into positively charged atoms and free electrons – the so-called plasma. When part of the molecules recombines, the excess energy is released in the form of photons (light particles), giving the air around the vehicle an amber glow.
This plasma layer may be fine, but it can cause radio cancellation. When an electron passes along a conductive wire, we have electricity. Similarly, when free electrons move through the plasma around a vehicle, we have an electric field. If the electric field becomes too strong, it can reflect and attenuate radio waves as it tries to reach the spacecraft.
Completion not only results in loss of communication with flight crews and flight data, but may also make remote control and guidance impossible. Missions Apollo, Mars Pathfinder and the recent failed Soyuz 2018 rocket launched all damaged communications in a matter of minutes. Control of NASA’s mission involves six minutes of nervous eclipse during the peak heating phase of the return of the Dragon Crew – if during this time something goes wrong, it is in the hands of astronauts.
Another risky stage is parachute landing. In the final stage of the re-launch, the Dragon crew will deploy four parachutes as the vehicle descends to a slight splash in the Atlantic Ocean off the coast of Florida. This maneuver was tested by SpaceX 27 times before the crew landed next week, so it should work.
Successful landing will have huge consequences – reducing the cost of space exploration through the use of reusable rockets and enabling private space exploration. While SpaceX was developing the Crew Dragon vehicle under a NASA contract, the company is free to use the spacecraft for commercial flights without NASA’s involvement after operational certification.
SpaceX has partnered with the commercial aerospace company Axiom Space, which has the ultimate goal of building the world’s first commercial station. The proposed commercial activities for the station are wide: from space research and production to support for space research.
Then there is space tourism. Private citizens are already queuing for a ticket to space, and with the successful surge of Crew Dragon, they will not wait long. The American space tourism company Space Adventures (in partnership with SpaceX) plans to offer atmospheric flights with zero gravity, orbital flights with the possibility of space travel and the Moon by the end of 2021.
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Whether the costs, environmental impact and dangers of space flight for space tourism are justified is debatable. As this article shows, the necessary security briefings for Space Adventure ticket holders will be much more comprehensive than your usual “please take a minute to read the security card in the pocket of the seat in front of you.”