Comment Re:Killowatts are power, not energy (Score 1) 262
Regenerative braking systems work by having a generator driven by the wheels that drives an electrical load - typically a battery charger. Charging the battery generates a current through the generator making it act like a motor but in the opposite direction to the way the wheels are making it spin.
Actually, your typical freight train is running regenerative braking. If you look down on a locomotive going by, you can see huge fans in the top of the cab that are used to blow air over load coils. Figure a maximum sized train weighs in at 19,000 tonnes (130 car coal train), that means that when it's operating at 60km/hr it has roughly 2.6 gigajoules of kinetic energy. To stop it, that energy has to be dumped. Some of it is done by the train's air brakes, but most of it is done through regenerative braking in each of the locomotives.
This is all irrelevant when it comes to the SSC though, since it's using air resistance to drop its speed to 260kph, then slowing down with traditional brakes. The hard part is going to be making the brakes survive spinning at 10,000rpm, not dissipating the energy from slowing down.