Oberg: "The real significance of the ISS thruster test failure"

John Doe wrote in :

"Jorge R. Frank" wrote:
And ISS does exactly that - they call the mode "Night Glider".


If the arrays are at an angle to direction of travel (with the sun in
the back), do they provide any lift at all ?

"Any", yes. "Non-negligible" (in terms of being useful for orbit
maintenance), no. The station isn't just hypersonic; it's in a "free-
molecular" flow regime. L/D is generally so poor ( 1) that ISS is better
off following a strategy of minimizing drag (even though lift goes to zero)
rather than maximizing lift.

Once the truss os fully deployed, if they were to put one side at 45°
and the other at -45°, would it create sufficient force to actually put
the station into a spin ?

It would generate a measurable aero torque, and could in theory generate a
spin over time, though the angular acceleration would be quite low (the
station's moments of inertia are very large) and would take a long time to
build up a visible rate, even in the absence of control torques.

Will the surfaces be large enough that they could use the arrays/truss
to help desaturate the CMGs ?

In theory, yes. The software accounts for this (rather than seeking gravity
gradient attitudes, it seeks torque-equilibrium attitudes that balance the
aero and gravity-gradient torques), but currently does not take advantage
of it.

--
JRF

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