Shock absorbers use valving of oil and gasses to absorb excess energy from the springs. The 1993 Rodeo featured a recalibrated suspension system, softened spring rates and softened shock valving. The airship slowed, then adjusted buoyancy to neutral by valving off hydrogen or dropping ballast. It also requires additional external piping and valving, and so requires additional maintenance. Madou's group also invented a serial siphon valving structure which makes flow control much easier. It got new composite plates and valving. Valving procedures can give some relief, but further research is required.