In August 1964, this test fixture was used by the Spacecraft Design Section at NASA's Jet Propulsion Laboratory in Pasadena, Calif., to study spin stabilization of spacecraft - in this case, Rangers 8 and 9 (part of the Ranger Block 3 design). Many spacecraft had used spin stability for attitude control during acceleration or thrust, and it was found that a slower spin provided better stability for the coasting phase.
One method of decreasing the spin of a spacecraft, or de-spinning, was the deployment of yo-yo devices. Weights were attached to rigid or stretch cords, then released while the fixture was spinning. The cords would unwind, like the arms of a figure skater extending to slow a spin, and then the cords were released. In this photo, the cables and weights can be seen, attached to the outside of the white circle. The test fixture is surrounded by what appear to be bales of paper and trash to absorb the impact of the weights when they were released from the spinning test fixture.