Drucella Andersen                                                                                                      
July 23, 1991
Headquarters, Washington, D.C.
(Phone:  202/453-8613)


RELEASE:  91-116

NASA IN-STEP PROGRAM EXPERIMENT TAKES FIRST FLIGHT ON STS-43


     NASA's In-Space Technology Experiments Program (IN-STEP) 
passes a major milestone this week when its first flight 
hardware, the Tank Pressure Control Experiment (TPCE), rides into 
orbit aboard Atlantis on STS-43.

     Transfer and control of very cold (cryogenic) fluids in 
microgravity is critical to plans for several future U.S. space 
efforts.  TPCE will demonstrate how cryogenic storage tank 
pressures can be controlled by actively mixing the fluids to 
eliminate temperature stratification.  The technology would allow 
lightweight cryogenic tanks to be used in advanced space 
projects.  Scientists also will use the results to validate 
computer codes used to calculate the energy of liquid propellants 
in space.

     TPCE is contained in a Getaway Special canister mounted on 
the sidewall of Atlantis's payload bay.  It includes a Plexiglas 
tank 85 percent filled with liquid Freon 113, a refrigerant.  The 
remaining volume contains helium gas and Freon vapor, so that  
the tank pressure is about 2 pounds per square inch above the 
liquid's vapor pressure.

     During each test run, heaters are turned on to raise the 
pressure above equilibrium.  Liquid jets then circulate the Freon 
at a low velocity, a process that returns the pressure to 
equilibrium.  The experiment measures pressure, temperatures and 
jet flow rates within the tank.  Video cameras record the liquid 
flow patterns through the tank's transparent walls.  Thirty-eight 
different combinations of flow rates and heater locations will be 
tested.

     A second IN-STEP experiment package is also on this year's 
Shuttle manifest.  MODE (Middeck 0-gravity Dynamics Experiment), 
which will fly on STS-48 in September 1991, will study critical 
aspects of mechanical and fluid behavior of components for future 
space structures, such as Space Station Freedom.



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     One of the most attractive features of these experiments is 
the potentially large payoff for a relatively small financial 
outlay.  Boeing Aerospace Company, Seattle, developed the TPCE 
hardware for $1.7 million.  MODE, designed by the Massachusetts 
Institute of Technology, Cambridge, cost $1.9 million.

     Since 1987, IN-STEP has brought NASA, the aerospace 
community and academia together to research potentially valuable 
space technologies using small, relatively inexpensive payloads.  
NASA's Office of Aeronautics, Exploration and Technology at NASA 
Headquarters, Washington, D.C., selects the experiments and 
manages the program.

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