National Aeronautics and Space Administration

Glenn Research Center

TVC and Flywheel

We first learned about the benefits of flywheels over other energy storage methods like batteries. Flywheels, which are traditionally thought of as heavy spinning objects meant for big machines, actually hold the potential for extremely high energy density. Flywheels have great depth of discharge, unlike batteries, as they can be spun down to rest without fault, while batteries will start to chemically degrade when discharged past manufacture ratings. Since the energy in a rotating object scales with the rotational velocity squared, more energy can be stored in a flywheel by spinning it faster instead of making it heavier.

Glenn is researching flywheels constructed of advanced composite materials which can be spun up to tens of thousands of RPMs. Even higher speeds can be attained with breakthroughs in stronger materials such as carbon nanotubes. Flywheels are currently behind batteries in terms of energy density, but are expected to overtake them in the next 30 years with advancements in material technology. As a few interesting facts, everyone was surprised to hear that composite flywheels are actually under the most stress when at rest, in the way they are constructed. Additionally, building 333 actively uses a large flywheel as a backup power source. This UPS can supply 20 kW of power for 20 seconds to give time for diesel generators to kick on after a power outage.

The thrust vector control (TVC) test bed is an exact simulation of the TVC system on the Ares 1 rocket upper stage. This test bed simulates the gimbaling of the Ares 1 rocket engine with a large mass suspended from the test bed that has exactly the same inertial parameters as the real engine. This gimbaling allows the real rocket to make precise adjustments to its trajectory. The setup is supported by enormous three inch thick steel supports which are buried deep into the concrete below the building.

These supports must be stiff enough so that no movement occurs other than in the gimbaling mass. Everyone was thoroughly impressed with the robustness of the test rig. It is so robust, in fact, that the rig cannon even be removed from the ground. Once testing is finished, the supports sticking above the ground will be cut short and buried in concrete below the test rig, serving as an everlasting memorial to their own contribution.