The present invention relates to a vibration suppressing device for spacecrafts that protects astronaut crews and sensitive electronic devices of the spacecrafts from a pogo oscillation, a combustion oscillation in rocket engines.
The spacecrafts produce self-excited combustion oscillation of a propellant called pogo oscillation during lift-off. The pogo oscillation can cause a vibration of a payload system that impairs astronaut crews' ability to perform piloting functions, and permanently damages electronics, optics and other sensitive equipment. To minimize the impairment of astronaut crews' ability and the permanent damage to sensitive equipments, the spacecrafts are generally designed to suppress the vibration both passively and actively.
U.S. Pat. No. 8,033,111 B2 discloses a device for damping a plurality of vibrations of a combustion chamber utilizing an acoustic resonator adjusted to a plurality of hazardous frequencies that can cause the pogo oscillation of the spacecraft. As a passive vibration suppression not at the source, U.S. Pat. No. 7,967,282 B2 discloses a vibration isolation mount consisting of a plurality of elastomeric members, a break frequency and a damping ratio of each of which are adjusted to suppress a vibration of a particular frequency and amplitude such that a plurality of vibrations transmitted to the payload system are attenuated. L. A. Nassar, R. Bonifant, C. Diggs, E. Hess, R. Homb, L. McNair, E. Moore, P. Obrist, M. Southward, “Spacecraft Structures and Launch Vehicles”, Nov. 18, 2004 discusses a structural design of the spacecraft minimizing an amount of the plurality of vibrations transmitted to the payload system while fulfilling a requirement for maximum payload capacity. Further, U.S. Pat. No. 7,461,728 B2 discloses an active vibration damping system that suppresses a vibration transmitted to the payload system by actuating an active mass.
The prior arts in U.S. Pat. No. 8,033,111 B2, U.S. Pat. No. 7,967,282 B2, and L. A. Nassar, R. Bonifant, C. Diggs, E. Hess, R. Homb, L. McNair, E. Moore, P. Obrist, M. Southward, “Spacecraft Structures and Launch Vehicles”, Nov. 18, 2004 fail to provide a best vibration suppression performance for varying relative contributions from the plurality of vibrations of different frequency under an influence of a climatical condition, an altitude and an amount of a residual propellant at an instant during lift-off, and for varying length of the spacecraft after a used stage thereof is disconnected, since they are adjusted to suppress only the plurality of vibrations of a plurality of fixed frequencies and amplitudes. On the other hand, after the application of U.S. Pat. No. 7,461,728 B2 a plurality of non-negligible amount of vibrations are transmitted to the payload system, since a phase of a motion of the active mass cannot be made completely opposite to that of the plurality of vibrations transmitted to the payload system due to a time delay in a control loop including a plurality of sensors, a logic circuit, an actuator and the active mass.