|John D. Bird Inventor of Jet Shoes|
|Center:||Langley Research Center|
|Important Tests:||Flying Platform, Jet Shoes, Foot-Controlled Maneuvering Unit,|
|Back To 1220|
Uncertainties concerning physical capabilities and limitations of an astronaut performing an extravehicular activity have led many space flight centers to develop a variety of reduced gravity simulators. The Langley Research Center identified with the increased importance of extravehicular activity in space and had an overall desire in the mid twentieth century to design simple and reliable device that allows the astronaut to move freely without unduly restrictions. The Jet Shoes experiment was a direct result of this attitude and contributed to space exploration in a positive way by leading to other uses of the technology and inspiration for extravehicular devices that came after wards.
The Jet Shoe concept was created by John D. Bird in 1965. The concept was initially inspired by the “Flying Platform” design, created by Charles Zimmerman and Paul Hill, which showed man’s inherent ability to control a thrust vector pushing against the soles of his feet. The intentions of the “Flying Platform” project developers were to use it for exploration on the Moon. The platform was a proof-of-concept work for the servomechanism used for the Lunar Landing Research Facility in 1962 ( photo with Champine). The army was also interested in using the device for transporting soldiers. Considering that approach and the fact that swim divers can maneuver in water using utilizing the thrust developed by flippers it suggests the concept of placing jets on the shoes of a subject in zero gravity.
The Jet Shoe concept involves placing single jets on the soles of the shoes of the subject. These jets are activated on demand by depressing a toe switch. Movement of the feet and legs is used to direct the jets and so produce the desired change in attitude and position. The switches are individually controlled and can be activated by a toe switch, a bite bar, or a sip-switch (the latter options involve the subject’s mouth). The Jet Shoes experiment hardware consists of a gas storage backpack assembly and portable show mounted solenoid thrust valves. The pneumatic system was designed to use gaseous oxygen and to deliver two pounds of thrust from each thrust valve nozzle with a pressure at a regular outlet of approximately 165 psi. The gas storage tank was designed to contain a minimum of 15 pounds of gaseous oxygen at 6000 psi. This concept makes use of the well developed balance capability of the human body utilized in walking to control jets attached to the soles of the shoes to produce the desired translations and rotations of the body necessary for extravehicular activity.
There are several advantages to using the Jet Shoe concept. Because the jets are directed and controlled by the feet and not by the hands, both hands are free for other tasks. The utilization of only two jets for the entire locomotion process rather than a greater number of jets in an orthogonal array makes the system simple in number of components and more reliable.
[top] Facilities and Simulators
Several facilities at the NASA Langley Research Center were employed for simulating a zero gravity environment of the astronaut maneuvering in free space. Experiments were conducted using various techniques to gain confidence in the effectiveness of Jet Shoes for EVAs, or astronaut Extra-Vehicular Activity. The maneuvers here at Langley were performed first without a space suit in a short sleeve environment and later in a pressurized space suit to gain an idea of the influence of the restriction in mobility on the effectiveness of the Jet Shoes.
1220, or the Simulation Lab. The facility had an air-bearing test simulator where the test subject lied on his side on an air pad support test vehicle that enabled him to experience three degrees of freedom. The simulation utilized air pads that were specifically created for the purpose of this experiment. The first designs involved square wood planks that attached to a vacuum cleaner hose and held up the subject’s weight. The use of these air pads permitted zero drag over a leveled surface. Most of the floor in Building 1220 was specially surfaced with an extremely smooth plaster surface which was well-suited to low friction air bearing testing. The facility also contained a whipple-tree suspension simulation and a pendulum system. The whipple-tree suspension was ideal for testing jet shoes because it gave three degrees of linear freedom and angular freedom about the vertical axis. The simple pendulum system, an earlier simulator located in Building 1220, was not as effective because it only supplied one degree of freedom, however, it proved useful when the inventors were studying orientation capabilities. Building 1220 also housed the Visual Simulator. This simulator provided a complex way to study and investigate Jet Shoes and the Foot Controlled Maneuvering Unit, the concept inspired by the Jet Shoes project. In the Visual Simulator, complete six-degree-of-freedom motion was obtained from three angular degrees of freedom of a small model of a target vehicle, translation of the model in front of the television camera, and a servo-driven mirror placed to the right of the pilot’s head.
Building 1268, then known as the Data Processing Center but now referred to as the Flight Control Research Facility, held all of the analog computers that interfaced with the simulation facilities in Building 1220. This facility contained the digital computation necessary to control the cockpits in Building 1220 to ensure effective and efficient Jet Shoes experiments. Building 1298 was the Navigation and Guidance Research building, now referred to as the Stability and Control Facility, which was concerned with the mechanics and control of the Jet Shoes.
Although Building 1220 housed the majority of the simulators used in the Jet Shoes experiment, the Langley Rendezvous Docking Simulator in the large flight research hangar, 1244, allowed the project to go to a whole new level. Arthur W. Vogeley proposed the concept for this device and helped create many of the components. A targeted vehicle was suspended at one end of a track attached to the hangar roof while a movable vehicle was driven along the track to move toward the target during a docking maneuver. The simulator allowed test subjects to experience the feeling of weightlessness while attempting to reach the target vehicle. Building 1244 was also home to the Langley Research Center Reduced Gravity Simulator. This simulator allowed for two translational degrees of freedom and one rotational. The vehicle and pilot were supported by two overhead trolleys 9.5 degrees from the horizontal. Amos A. Spady, Jr. was one of the leaders in Langley zero gravity simulation and also the author of Preliminary Research Flights of a One-Man Rocket Propelled Backpack in Simulated Lunar Gravity.
The Lunar Landing Research Facility, also known as the Impact Dynamics Research Facility and commonly called the Gantry (Building 1297), was home to Langley’s three-degree-of-freedom, inclined plane, lunar gravity simulator. This simulator, sustained by the same mechanism used to support the LEM during its testing, provided simulated lunar gravity by supporting a subject on his side in an incline attitude of 9.5 degrees from the horizontal. The resulting force was one-sixth the subject’s weight and it demonstrated the feasibility of the use of the Jet Shoe concept for extravehicular activity. In June 1967 a preliminary lunar flight vehicle program was carried out with a small, one-man, rocket-powered, stand-on vehicle. It was called POGO and the results that were produced from this limited program at the Lunar Landing Facility proved that a simple thrust-vector-controlled vehicle could be flown in simulated lunar gravity.
There were obstacles that the researchers faced while designing the Jet Shoes. The criticism of Jet Shoe models was that they were heavy, inconvenient to put on, and needed initial adjustment. There were varied opinions of the value of simulation studies at Langley. Hartley A. Soule, an early expert on aircraft control and handling qualities, claimed that any self space locomotion devices could be operated by an astronaut and therefore there was no need for any simulators to be run. This put an end to tests of these ideas at Langley for some time. The disadvantages to Jet Shoes eventually caused Langley researchers to move on to a new design.
[top] Progression to FCMU and MMU
The idea for the Foot Controlled Maneuvering Unit, or the FCMU, evolved from the “Flying Platform” and John D. Bird’s original Jet Shoes concept. On April 6, 1967, Deke Slayton, Direction of Flight Crew Operations, requested Jet Shoes to be removed from the experiment program. Slayton stated that their use while wearing a full life support unit would be too cumbersome for the astronaut and therefore pose a safety risk. Development continued, however, and the FCMU design flew on Skylab, the United States’ first space station, as experiment TO20. It consisted of a bicycle-like framework and saddle seat, with a backpack that held the propellant and control equipment. Attached to the framework was a set of four nozzle thrusters assembled under each foot and controlled by foot-actuated switches. The design involved an aluminum framework, with a 24,600 cm³ pressure tank of nitrogen gas at 3,000 psi attached to the backpack with a battery to supply the power. It could rotate around the three axes of roll, pitch, and yaw. The thruster assembly mounted outboard of each foot controlled the four nozzles, the top or bottom each producing 4,464 N of thrust, and the fore and aft each producing 1,339 N of thrust. The Principal Investigator of this experiment was Donald E. Hewes, who developed much of the Jet Shoes and FCMU design mechanisms and described his work in his technical papers Discussion of Control Systems for foot controlled space maneuvering units and Development of Skylab Experiment TO20.
Pedal combinations for the FCMU produced the following movements:
Foot movement – result
Both feet up – translation head first
Both feet down – translation feet first
Right and left toes up – pitch up
Right and left toes down – pitch down
Right toes up, left toes down – yaw left
Right toes down, left toes up – yaw right
Right foot up, left foot down – roll left
Right foot down, left foot up – roll right
The Manned Maneuvering Unit, or MMU, is the most recent extravehicular activity device that has assisted many astronauts during EVA. The research conducted at the Langley Research Center on Jet Shoe and the FCMU helped with the progression towards this back-mounted maneuvering system complete with thrusters equidistant around the system’s center of gravity on the outside of the frame of the backpack unit. Placing the thrusters on the bottoms of the astronauts’ shoes proved to be less practical then placing them on the astronaut’s back. The distance between the thrusters and the astronaut’s center of gravity in the Jet Shoes concept, which is approximately around his torso, was too large. Any slight alteration of inertia could swing the astronaut off balance, whereas the placement of the MMU thrusters is at a much closer proximity to the astronaut’s center of gravity. The MMU was stored in flight support units in the forward end of the orbital payload bay, and could be put on or taken off by one pressure-suited astronaut during EVA. It had the capability of supporting a six-hour EVA. The propulsion system involved twenty-four thrusters, affording a six-degree-of-freedom control mode (+X, +Y, +Z, +roll, +pitch, +yaw). The thrusters were powered by gaseous nitrogen from the two storage tanks in the rear central compartment of the unit.
Contributor: Rachel Weinberg, 2010
[top] Facilities Used for Jet Shoe Research
1220 Old hangar known as the Simulation Lab during Jet Shoe experiments
1244 Hangar with Rendezvous Docking Simulator
1297 Impact Dynamics Research Facility otherwise known as the Lunar Landing Facility or Gantry
1268 Flight Control Research Facility
1298 Stability and Control Facility
646 Free Spinning Tunnel
1974 Building 1298 Navigation and Guidance Branch Photo (Names)
2010 Jet Shoes with Dan Burdette – Rachel Weinberg interviews Dan Burdette on the work of Jets Shoes at Langley Research Center
[top] For Further Reading
Bird, John D., Howell D. Garner, Ernest D. Lounsberry, and David F. Thomas. Jet Shoes. NASA, assignee. Patent 3,420,471. 7 Jan. 1969.
Bird, John D., Otis J. Parker, and David F. Thomas. "Jet Shoes" Experiment in EVA. Tech. no. CN-159367. Hampton: NASA, 1967.
Hansen, James R. Spaceflight Revolution: NASA Langley Research Center from Sputnik to Apollo. Washington, DC: National Aeronautics and Space Administration, 1995. 229-31.
Harris, Sr., Randall L., Eric C. Stewart, Lee H. Person, Jr., and Kenneth R. Yenni. Preliminary Research Flights of a One-Man Rocket Propelled Backpack in Simulated Lunar Gravity. Working paper no. LWP - 836. Hampton: NASA, 1969.
Hewes, Donald E., and Kenneth E. Glover. Development of Skylab Experiment TO20 Employing a Foot-Controlled Maneuvering Unit. Tech. no. TN D-6674. Hampton: NASA, 1972.
Phillips, W. Hewitt. "Space Simulation Studies." Journey into Space Research: Continuation of a Career at NASA Langley Reserach Center. NASA/SP-2005-4540. Washington, D.C.: NASA, 2005. 35-49.
Thomas, David F., John D. Bird, and Richard F. Hellbaum. Jet Shoes – An Extravehicular Space Locomotion Device. Tech. no. TN D-3809. Hampton: NASA, 1967.
Vogeley, A. W. “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.
Zimmerman, C. H., Paul R. Hill, and T. L. Kennedy. Preliminary Experimental Investigation of the Flight of a Person Supported by a Jet Thrust Device Attached to His Feet. Tech. no. R L52D10. NASA.