Regardez ce qui arrive aux astronautes de la station spatiale lors d’un reboost orbital.

Matthias Maurer Expedition 66 ISS Reboost
Matthias Maurer Expedition 66 ISS Reboost (en anglais)

Clip vidéo de l’astronaute de l’ESA Matthias Maurer et de ses coéquipiers de l’Expédition 66 lors d’un reboost de la Station spatiale internationale. Alors que la vidéo au bas de cet article est accélérée 8 fois, ce GIF est accéléré 32 fois.

Cela fait penser à la descente d’un toboggan dans la cour de récréation – et à la reprise immédiate de la file d’attente pour descendre à nouveau. Mais dans l’espace.

Voici ce qui se passe à bord de la Station spatiale internationale lorsque les propulseurs sont mis à feu pour une relance orbitale. Alors qu’on a l’impression que les astronautes se déplacent à l’intérieur de la station, c’est en réalité la station spatiale qui se déplace autour d’eux. Et en réalité, l’accélération ne se produit pas aussi rapidement – la vidéo est accélérée huit fois (le GIF du haut est accéléré 32 fois). Mais ça a quand même l’air amusant !

Les données relatives au taux d’accélération/changement pour cette combustion particulière n’étaient pas disponibles, mais pour une combustion précédente d’une durée de 12 minutes, 17 secondes, le Delta-V était de 1,34 mètres/seconde (4,4 pieds/seconde).

L’équipage vu ici est celui de l’Expédition 66, qui comprend ;” data-gt-translate-attributes=”[{” attribute=””>NASA astronauts Raja Chari, Thomas Marshburn Kayla Barron, and Mark Vande Hei; ESA (European Space Agency) astronaut Matthias Maurer; Roscosmos cosmonauts Anton Shkaplerov and Pyotr Dubrov.

ISS Expedition 66 Crew Official Portrait

The official portrait of the seven-member Expedition 66 crew. From left are, NASA astronauts Raja Chari and Thomas Marshburn; ESA (European Space Agency) astronaut Matthias Maurer; Roscosmos cosmonauts Anton Shkaplerov and Pyotr Dubrov; and NASA astronauts Kayla Barron and Mark Vande Hei. Credit: NASA

The astronauts are obviously enjoying the experience. It must feel somewhat similar to when a car or airplane accelerates – it feels like you are being pushed back into the seat, when in reality, the seat is being pushed into you by the acceleration of the vehicle.

The ISS usually orbits about 400 km (250 miles) above the Earth. But the effects of atmospheric drag can cause the station to lose as much as 100 meters a day in altitude. Therefore, regular reboosts are required, usually about once a month. There’s no real schedule for when a reboost is done, as the density of Earth’s atmosphere at those altitudes constantly changes, depending on how much energy is being fed into it by the Sun. Therefore, the orbital decay rate is not consistent. But the ISS orbits decays faster than other satellites at a similar altitude due to its massive size and surface area.

International Space Station From SpaceX Crew Dragon Endeavour

The International Space Station is pictured from the SpaceX Crew Dragon Endeavour during a fly around of the orbiting lab that took place following its undocking from the Harmony module’s space-facing port on November 8, 2021. The orbital complex was flying 263 miles above the Marshall Islands in the Pacific Ocean when this photograph was taken. Credit: NASA

Reboosts are also done to optimize the ISS’s orbital position for future visiting vehicles arriving at the station. This particular reboost was performed in March 2022 using Russia’s ISS Progress 79 cargo craft. By firing its engines for several minutes, the station was put at the proper altitude for an arriving Soyuz for the new crew members that arrived in March.

NASA says that all ISS propulsion is provided by the Russian Segment and Progress cargo spacecraft. Propulsion is used for station reboost, attitude control, debris avoidance maneuvers (as well as eventual deorbit operations). The U.S. gyroscopes provide day-to-day attitude control, i.e. controlling the orientation of the station. Russian thrusters are used for attitude control during dynamic events like spacecraft docking, and they provide attitude control recovery when the gyroscopes reach their control limits.

Northrop Grumman’s Cygnus is the only U.S. commercial spacecraft currently available to provide reboosts, although it is still currently in testing mode. The first Cygnus capable of performing reboosts arrived at the ISS in February 2022.

Originally published on Universe Today.

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