A team of engineers at Marshall Space Flight Center developing solutions to mitigate potential thrust oscillations of the Ares 1 rocket have received approval for two options during a December 17 meeting of the Constellation Program Control Board. The options include an passive upper-plane C-spring isolator for shock absorption and a LOX tank damper to detune the LOX propellant resonance from the rocket structural resonance.
Thrust oscillations occur on all solid rockets due to a coupling of the structural resonance of the launch vehicle with the pressure wave created during burning of the solid rocket propellent. The presence of thrust oscillations are of concern to astronauts during launch of Ares 1 because significant thrust oscillations could present a danger to crew safety and response capabilities during launch. Early simulations of Ares 1 showed the potential for unacceptable thrust oscillations. However, neither the Ares 1-X test nor the DM-1 test of the Ares-1 solid rocket motors exhibited problematic thrust oscillations.
The development and incorporation of the isolators provides a further measure of conservatism and safety within the Ares 1 design and is indicative of a development program addressing real issues that arise during engineering design and testing.