The NASA Johnson Space Center built a 4200 ft2 parafoil for the U.S. Army Natick Soldier Center to demonstrate autonomous flight using a guided parafoil system to deliver 10,000 lbs of useable payload. The parafoil's design was based upon that developed during the X-38 program. The drop test payload consisted of a standard 20-foot Type V airdrop platform, a standard 12-foot weight tub, a 60 ft drogue parachute, a 4200 ft2 parafoil, an instrumentation system, and a Guidance, Navigation, and Control (GN&C) system. Instrumentation installed on the load was used to gather data to validate simulation models and preflight loads predictions and to perform post flight trajectory and performance reconstructions. The GN&C system, developed during NASA's X-38 program, consisted of a flight computer, modems for uplink commands and downlink data, a compass, laser altimeter, and two winches. The winches were used to steer the parafoil and to perform the dynamic flare maneuver for a soft landing. The laser was used to initiate the flare. The GN&C software was originally provided to NASA by the European Space Agency. NASA incorporated further software refinements based upon the X-38 flight test results. Three fullscale drop tests were conducted, with the third being performed during the Precision Airdrop Technology Conference and Demonstration (PATCAD) Conference a t the U.S. Army Yuma Proving Ground (YPG) in November of 2003. For the PATCAD demonstration, the parafoil and GN&C software and hardware performed well, concluding with a good flare and the smallest miss distance ever experienced in NASA's parafoil drop test program. This paper describes the 4200 ft2 parafoil system, simulation results, and the results of the drop tests. GNC GPS U D= air data probe = crew return vehicle = coefficient of drag = center of gravity = coefficient of lift = degree of freedom = decelerator system simulation = energy management circle = square foot = guidance, navigation and control system = global positioning system = lift over drag

NASA has developed and tested a large parafoil for use in landing the International Space Station crew return vehicle. A series of tests using low-velocity airdrop pallets and prototype lifting bodies ights has demonstrated that the parafoil recovery system is a viable option for safely landing a crewed vehicle. The aerodynamic characteristics of the parafoil system have been determined through a series of ight-test maneuvers and subsequently successfully modeled using an eight-degree-of-freedom simulation program. An introduction to the requirements for the crew return vehicle, a description of the parafoil system, an overview of the testing performed including several signi cant ndings, a description of the techniques used to assess the aerodynamic performance of the parafoil system, and a discussion of the simulation of the parafoil system are presented. Nomenclature AR= aspect ratio b= parafoil span C L ; C D = lift and drag coef cients Cm c=4= parafoil system pitching moment coef cient about c=4 Cn r = yawing moment due to yaw rate Cn ± f = yawing moment due to control line de ection difference between left and right aps c = parafoil chord c=4 = quarter chord point on the parafoil keel HR = velocity vector heading rate HR wc = wind-corrected heading rate N q = dynamic pressure RA, µ r = parafoil rigging angle (X pf to parafoil keel) R=b = line length ratio (average suspension line length divided by span) S = parafoil reference area t = time, where t 1 is time at rst data point and t 2 time at second data point V h wc = wind-corrected horizontal velocity V tot = total velocity V w = wind velocity V x = east velocity V y = north velocity V z = vertical velocity W pf = weight of the parafoil system, including rigging, but not payload W sys = weight of the parafoil system and payload W =S = wing loading (payload weight divided by parafoil area) X cg ; Y cg = distance from the con uence to the parafoil system c.g. in parafoil coordinates X PL = payload body axis parallel to payload's bottom surface X pf ; Z pf = parafoil coordinate system, Z axis originating at the con uence point with Z extending up through c=4 Z c=4 = distance from the con uence to the c=4 ® = parafoil angle of attack relative to keel ® PL = payload angle of attack relative to X PL°= wind-corrected ight-path angle (V wc to horizon) ± f = control line de ection delta µ = parafoil pitch angle (X pf to horizon) ½ = atmospheric density Á w = direction of the wind measured from the north, that is, wind is coming from Á w 9 & b = body yaw rate

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