WRESAT spin dissipation system, was it passive or active?

Question

WRESAT had a hydraulic loop energy dissipation system to change its axis of spin.

An interesting point to note about the WRESAT design is that, even though WRESAT was spinning around its long axis at orbital insertion, this was not the preferred orientation for the scientific payload. Close inspection of the WRESAT schematic to the right shows an energy dissipator which was a closed hydraulic loop of silicone oil which dissipated the rotational energy as heat. The net result is WRESAT eventually tumbling around it's short axis which places the axis of rotation pointing out into space.

Was this silicone oil energy dissipation system passive or active? In other words, was it a rotational viscous dampener or was there a pump involved.

This related question asks about passive spin/oscillation dampening systems.

Answer 1

Everything I'm finding on the energy dissipation system indicates that it was passive. This makes sense--introduce a pump, and you add complexity.

The research on this type of passive system was first published in 1971: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710025114.pdf

In a passive system like this, you're looking at the friction of the viscous fluid on the walls of the energy dampening system being used to slow down the spin. That friction is then dissipated s heat.