The National Reconnaissance Organization (NRO) has a spacecraft program called the Space Technology Experiment (STEX) to test advanced technologies in space. During launch on the Taurus launch vehicle, dynamic loads imparted to the STEX spacecraft would have caused unacceptably low force/stress margins, if the spacecraft were hard-mounted to the Taurus. A vibration isolation system was designed to reduce the dynamic loads on the STEX spacecraft. The isolation system was designed, fabricated, tested, and delivered by CSA Engineering Inc., under an SBIR Phase II contract with the Air Force Research Lab.

• Reduce dynamic loads imparted from the launch vehicle to the spacecraft due to the resonant burn load case. This was the most severe load case for the spacecraft.
• Reduce dynamic loads imparted from the launch vehicle to the spacecraft due to the other load cases, if possible. This is of secondary importance.
• Do not increase dynamic loads from any load cases.
• Do not introduce too much spacecraft to fairing relative displacement.
• Do not introduce modes which are too low in frequency or high in amplitude such that they interfere with the attitude control system.

The isolation system was designed, fabricated, tested and delivered in a three-month period. The STEX spacecraft launch was very successful and the flight telemetry data confirmed that the isolation system performed as designed.

The telemetry flight data from the launch of the STEX spacecraft on the Taurus rocket on October 3, 1998 is shown in the figure. Specifically, two channels of the flight data measured acceleration in the longitudinal (thrust) direction of the vehicle to assess the performance of the SoftRide vibration isolation system. One accelerometer was just aft of the isolation system; this is referred to as "Below isolators" in the following plots and represents the "hard side" of the isolation system. The other accelerometer was located just forward of the isolation system; this is referred to as "Above isolators" in the following plots and represents the "soft side" of the isolation system. This transient data shows significant attenuation across the SoftRide isolation system.

A PSD of the flight data, averaged for the entire transient, shows excellent broadband attenuation from the SoftRide isolation system.

PSD waterfall plots of the flight data show the frequency content as a function of time. From these plots and from the transient data, it is clear that the SoftRide vibration isolation system performed very well to reduce structure-borne vibration levels transmitted to the spacecraft. The isolation system was designed specifically to reduce the effects of solid motor resonant burn in the 45 Hz to 60 Hz frequency range, which it did very well. It should also be noted that the SoftRide vibration isolation system provided extreme reductions of structure-borne acoustics at higher-frequencies as shown in the plots up to 2000 Hz.