Boy, does time fly! It seems like yesterday that I was commenting live images of the launch of Soyuz TMA-09M from the Italian Space Agency headquarters in Rome and here we are: tonight Luca, Karen and Fyodor will return to the planet after having the ride of their lives as they reenter the atmosphere. I’m lucky that I’ll have the chance to follow the reentry and the landing from Mission Control Houston.
How does a reentry happen? At 23:26:00 GMT the undock command will be sent. The system is very simple: within about 2.5 minutes the docking system hooks will open and the spring loaded pushers at the docking interface will give the Soyuz a small separation velocity of about 12 cm/sec.
Once at a safe distance, after ca. 3 more minutes, the Soyuz attitude control thrusters will fire for about 15 seconds. We call that separation burn.
Only after that will the guidance and navigation system of the Soyuz be turned on. First thing, it will spin the ship to find the Earth with its infrared sensors. Once the sensors capture the Earth’s infrared emissions, they will start feeding the attitude control system the information needed to orient the Soyuz along the local vertical, with the periscope towards Earth, so that the Commander can visually verify that the orientation is correct. The Soyuz will also be flying “backwards”, with the nozzle of the main engine facing in the direction of flight. That’s called “braking attitude”.
The braking burn is scheduled for tonight at 1:55:33 GMT and will last about 4.5 minutes. Here are some pretty amazing numbers. The orbital velocity of the Station is somewhere between 7 and 8 km per second, or between 7000 to 8000 meters/second. The deorbit burn is “only” 128 meters/seconds. That’s all it takes to be hitting the ground less than an hour later!
But before that module separation will have occurred at about 02:23 GMT: remember that only the central, bell-shaped descent module can survive atmospheric reentry intact!
At about 10 km the active reentry guidance will terminate and the parachute will be opened. Expect that at about 02:35 GMT. It will then be about 15 minutes until impact, during which the heat shield will be ejected to expose the retrorockets and the seats will extend up to the “armed” position to give the shock absorbers the travel they need to work effectively. Even with the retrorockets firing, that you can see in the picture, it’s certainly not a soft landing!
Enjoy the ride and be safe Luca, Karen and Fyodor. Looking forward to seeing you soon!
Photo credit: NASA
(Trad IT) Traduzione in italiano a cura di +AstronautiNEWS qui:
https://www.astronautinews.it/tag/logbook/
(Trad ES) Tradducción en español aquí:
https://www.intervidia.com/category/bitacora/
(Trad FR) Traduction en français par +Anne Cpamoa ici:
https://anne.cpamoa.free.fr/blog/index.php/category/logbook-samantha
10/11/2013