English: Test subject wearing jet-shoe apparatus and resting in sling support. The cables are not attached. From A.W. Vogeley, "Piloted Space-Flight Simulation at Langley Research Center," Paper presented at the American Society of Mechanical Engineers, 1966 Winter Meeting, New York, NY, November 27 - December 1, 1966. "As mentioned previously, Langley is conducting in-house and contract studies of extra-vehicular activities wherein zero gravity is simulated by the water-immersion technique. ... Water immersion is a very useful technique where motions are slow. When more rapid motion is required, as in studying one-man propulsion systems, other approaches are required. For these studies Langley has been using the RDS [Rendezvous Docking Simulator] in a manner similar to the LLRF [Lunar Landing Research Facility] technique. The test subjects are suspended in a sling support from a single RDS cable. As they translate about, the RDS tracks them, keeping the cable vertical. The test subjects operate in an effectively zero g environment in the horizontal plane. Tracking was originally done visually using closed-circuit TV, but recently a fast-response servo system using cable angle sensors has provided better operation. Some results of tests where subjects moved about merely by jumping and also where propulsion in the form of simple "jet-shoes" was provided are given in reference 20. Both methods, within limits, appear feasible. Full six-degree-of-freedom equipment for studies of more sophisticated one-man propulsion systems is now being procured. Called OMPRA (One-Man Propulsion Research Apparatus), the device will provide a gimbal system for rotational freedom, a quick response vertical servo for this translational freedom that is not now feasible with the RDS, and a versatile maneuvering unit."