This is reminiscent of going down a slide on the playground – and then immediately getting back in line to go down again. Except in space.
Here’s what it looks like on board the International Space Station when thrusters fire for an orbital reboost. While it seems like the astronauts are moving inside the station, in reality it is the Space Station that is moving around them. And in actuality, the acceleration doesn’t happen this fast – the video is sped up eight times (GIF on top is sped up 32 times). But it still looks like fun!
The data for the acceleration rate/change for this particular burn was not available, but for a previous burn with a duration of 12 minutes, 17 seconds had a Delta-V of 1.34 meters/second (4.4 feet/second).
The crew seen here is Expedition 66, which includes 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.
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.
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.
Adapted from an article originally published on Universe Today.