Rocking and rolling ISS during boost.

Every now and then the ISS needs to be given a little push to stay in the proper orbit. If the station never got a boost now and then, it would simply fall out of the sky like Skylab and the Mir station did. A planned rocket firing was canceled today since there are worries that the station may have been damaged by a rough boosting last month. The automated boost is normally very gentle, when rockets are fired on the Zvezda module. Astronauts could normally sleep through a boost. Basically, last month the booster rockets started to gimbal back and forth searching for the right angle, and set up a swaying in the station that reached the ISS's resonant frequency. Then the entire station started oscillating. Remember what happened to the old Tacoma Narrows bridge?
This problem will possibly delay visiting spacecraft this month and a Soyuz flight in March. The video below shows the rocking while the rocket was burning.

| James Oberg's article on MSNBC |