National Aeronautics and Space Administration

Glenn Research Center

Zero-G

On Wednesday, June 30, 2010, the Glenn Academy along with some other interns took a tour of Glenn’s own Zero Gravity Research Facility. Eric Neumann, the facility manager, and William Camperchioli, the lead electrical engineer, let students peer down the 510’ deep, 20’ diameter vacuum drop chamber. By height comparison, it is like looking down at the ground from the top of the Washington Monument! Although first operational in 1966 and registered as a national historic landmark, it still ranks as the largest vacuum drop chamber in the world offering experiments over 5 seconds of time in a microgravity environment. The chamber requires an hour of evacuation time (during which the experiment undergoes final preparations) and reaches a final pressure of 100 mTorr. That pressure is less than one thousandth that of atmospheric pressure!

The tower originally was designed to simulate twice the amount of zero gravity by launching a spherical vehicle from the bottom towards the top of the chamber, and then letting it fall back down, although this feature hasn’t been utilized since the 1970s. The original test vehicles are on display on the second floor of the facility, overlooking the drop chamber.

Each drop today utilizes one of the seven cylindrical drop vehicles, each 3’ in diameter and equivalent in weight to a Mini Cooper, which is optimally balanced to keep the vertical axis straight during the drop. At the bottom of the drop, the vehicle is decelerated in a 20’ deep and 5’ diameter container full of expanded polystyrene. This produces a force on the vehicle between 35g and 65g and creates quite a mess of little polystyrene pellets! Most of the pellet spray is contained by a net at the bottom of the tower, and a vacuum cleaner system pumps the pellets back into the container after the drop vehicle is recovered by crane.

The control room looks very similar to how it originally looked in 1966 with the addition of modern computer screens, and a flat screen television and provides electronic control as well as manual backups. During the drop, data is recorded on a flash card, an IR signal is sent to the control room in real time, and two wireless video feed are utilized although the experiment is controlled completely by on board automated systems and power during the drop. The most common experiments today deal with fire behavior in low gravity and in the past sought to understand low gravity fluid systems. The facility normally performs two or three tests per week and has a maximum capacity of two drops per day. Coming in at around $4,000 a drop, the facility is an economical choice for initial zero-g testing.