SpaceX tourists are coming back; see how tense reentry on Earth will be – 18/09/2021

Few moments in a space mission are as tense as re-entry, when astronauts must pass through Earth’s dense atmosphere and land safely in the water. Visitors on SpaceX’s Inspiration4 mission are about to experience this feeling.

The mission, which for the first time took a group of four inexperienced civilian astronauts into space aboard a SpaceX spacecraft, is nearing its end. After three days and a few dozen turns around the planet, the Dragon capsule will bring the crew back this Saturday (18th).

The landing is scheduled to take place around 8 pm (Brasilia time). Everything indicates that the Dragon capsule will fall into the Atlantic Ocean, off the coast of the US state of Florida, as well as the other manned missions that the company has already carried out for NASA (US space agency).

Re-entry step by step

Once in space, the Dragon capsule flies at 12,070 kilometers per hour, circling nearly 15 times around the Earth per day. When it’s time to return, the ship’s computer will dispose of its “trunk” — that is, the base of the capsule that contains the solar panels and power systems used to control the flight in orbit.

After that, Dragon will use its thrusters to perform a 180º turn, turning its tip to the opposite side, as if it were in reverse. This maneuver will cause the capsule to start to slow down. The thrusters are going to direct the vehicle’s trajectory to bring it down from its altitude, getting closer to Earth.

First, you need to find the correct angle for the trajectory. If it’s too acute, the G-force (gravity force caused by the capsule’s strong acceleration/deceleration) could be fatal to astronauts and/or friction with the air could cause the capsule to explode. If it’s too shallow, it could catastrophically “bounce” into the atmosphere and return unchecked to space.

When the Dragon is close enough to be “captured” by Earth’s gravity, the re-entry process begins. In order not to disintegrate when passing through the layers of Earth’s atmosphere, Dragon is equipped with a set of shields called PICA (Phenolic-Impregnated Carbon Ablator), which use carbon ceramic plates capable of withstanding temperatures of up to 2760 degrees Celsius.

Dragon will enter our atmosphere above approximately 27,000 km/h (7.5 km/s). This is more than twenty times the speed of sound and generates a huge shock wave and heat around it. In the most extreme phase of re-entry, the temperature can exceed 2000°C. That’s why we see the glowing capsule.

The PICA shield will be completely charred, but if all goes well, the capsule above it will be just a little scorched, and the ship’s crew will be fine.

A great risk at this moment is the loss of connection due to electrical instabilities. In extreme heat, a glowing layer of plasma (a sort of electrified cloud) covers the ship and can block or attenuate radio signals. The biggest problem is not simply losing communication with amateur astronauts, but making navigation and remote control of the capsule impossible.

Finally, the last tense moment is landing with the aid of a parachute. The capsule will launch five of them in the final stage of re-entry (two at 5.5 km altitude and three at 1.8 km), as it descends towards the Atlantic Ocean off the coast of Florida. This maneuver has already been performed a few dozen times by SpaceX and should not face major problems.

When touching water, the capsule should be falling at a speed of 7 meters per second. To rescue the Dragon capsule at sea, two vessels will be used. Afterwards, the amateur astronauts proceed by helicopter to land, where they will undergo a battery of medical tests to check if they are OK.

The return of the Inspiration4 mission will be streamed live on SpaceX’s YouTube channel.

*With reporting by Marcella Duarte