With the Hubble Space Telescope (HST) visible overhead in the Florida morning sky, Space Shuttle Columbia took off with a roar at 6:22 am on March 1, 2002. The CSA Hubble Damper team was present to witness the launch as the Shuttle ascended to rendezvous with the HST. Servicing Mission 3B proved to be a very successful mission for NASA… and for CSA Engineering.

In 1998 and 1999, CSA designed, built, tested, and delivered solar array dampers for the two new solar array wings that were installed during Servicing Mission 3B. On this March 1 mission, Shuttle astronauts replaced the two "flexible" wings that provided power for HST for 8 years (referred to as SA2) with "rigid" wings (SA3). In addition to providing increased power for HST, these new arrays will allow the Telescope to survive re-boost to a higher orbit. SA3 jitter performance is now at least an order of magnitude better than that of SA2. The dampers were added to the design of the new wings to accommodate attitude control bandwidth requirements by reducing the dynamic interaction of the wings with the HST spacecraft.

The solar array dampers are integral to the solar array masts, and are now suppressing the fundamental bending modes of the deployed wings at approximately 1.2 Hz (in-plane) and 1.5 Hz (out-of-plane). Modal damping of greater than 3.5% of critical is now present in these modes, over the temperature range of 0°C to 25°C, with a peak damping level of about 4.5%. The unique damper design, a combination of titanium spring and viscoelastic damper, was developed using a system finite element model of the solar array wing with measured viscoelastic material properties. Direct complex stiffness (DCS) tests were performed to characterize the temperature- and frequency-dependent behavior of the damper for correlation with measurements from fixed-base modal testing of the wing at NASA/Goddard Space Flight Center. Qualification testing of the damper at CSA Engineering insured that the "visco-titanium springs" could survive the launch loads. Performance testing (DCS tests) was repeated at CSA during the summer of 2000 after wing-level environmental tests at NASA/GSFC were completed. The dampers were built for a minimum life of 10 years, which is the anticipated remaining life of the HST on orbit.

Cutaway view of damper finite element model

The CSA Hubble Damper Team:
Kirsten Bender, Joseph Maly, Scott Pendleton and Jason Salmanoff