The dog on Everest is kept in the up position via magnetic force generated by the wheels in motion (by a device attatched to the wheels). When the wheels stop moving for any reason, the force goes away and the dog drops down and engages the antirollback teeth.
Another form of silent lift technology is the hydraulic lift, which is basically a catch car attatched to a hydraulic winch underneath the lifthill. When the train attatches to the catch car, the winch pulls the train up the hill silently and at a faster speed than typical chain lifts. This system is used on Millenium Force at Cedar Point and the new El Toro at Great Adventure. Both rides have unusally steep and/or tall lift hills which wouldn't support the weight of the massive chain that would be required for the hill.
Such a system isn't possible on a ride like WDW's space mountain as there are multiple trains on the lift at once. The hydraulic lift can only carry one train at a time.
Another form of silent lift technology is the hydraulic lift, which is basically a catch car attatched to a hydraulic winch underneath the lifthill. When the train attatches to the catch car, the winch pulls the train up the hill silently and at a faster speed than typical chain lifts. This system is used on Millenium Force at Cedar Point and the new El Toro at Great Adventure. Both rides have unusally steep and/or tall lift hills which wouldn't support the weight of the massive chain that would be required for the hill.
Such a system isn't possible on a ride like WDW's space mountain as there are multiple trains on the lift at once. The hydraulic lift can only carry one train at a time.