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Hillary Clinton's Fascinating Interview on NPR Fresh Air: 'Optimistic About Our Country, but I Am Not Naive'

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Love-Child of Cassandra and Sisyphus9/19/2017 1:38:38 am PDT

From what I have seen over the decades, almost no SciFi producers or writers have a clue of what it really takes to move in space.

Here is a good little article just on the ISS:

How Does the International Space Station Maintain Its Orientation?

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Nominally, attitude control is provided by four control moment gyroscopes (CMGs). Each CMG contains a wheel that is 220 pounds (100 kg). That wheel spins at 6600 rpm, resulting in an angular momentum of 3500 ft-lb-s (4742.5 N-m-s). The basic idea is that if a torque induces a rotation on the ISS, those wheels can rotate about their gimbals to change the angular momentum of the ISS, creating a counter torque. Using CMGs is much more subtle than using thrusters, so microgravity experiments are not impacted. CMGs do have limits, though, so thrusters can assist, if needed. That assistance is needed whenever the torques are large.

To minimize thruster assists, during quiescent operations, we do a type of attitude control called momentum management (MM). This is done by maneuvering the ISS to a torque equilibrium attitude (TEA) that was analyzed by the ground a year or more in advance. This TEA is an attitude that, with meanderings of up to 15 degrees, will result in the gravity torques and atmospheric torques adding up, over an orbit, to close to zero. The CMGs then take up the slack to make that zero.

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Angular momentum, torque, precession… all these things are usually ignored in SciFi shows.