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Deicing using piezoelectric actuators is considered as a potential solution to the development of low-energy ice protection systems for rotorcraft. This type of system activates resonant frequencies of a structure using piezoelectric actuators to generate sufficient stress to break the bond between the ice and the substrate. First, a numerical method was validated to assist the design of such systems. Numerical simulations were performed for the case of a flat plate and validated experimentally. The model was then used to study important design parameters such as actuator positioning and activation strategies, and it was concluded that positioning actuators at antinode locations, and activating them in phase with those antinodes to obtain maximum displacements for a given vibration mode. The findings were then used to apply piezoelectric deicing to structures more representative of a helicopter rotor blade. The method was implemented on a thinned Bell 206 main rotor blade and a Bell 206 tail rotor blade. Deicing performance was demonstrated in an icing wind tunnel. Power input to the actuators was below 19 kW/m2 (12 W/inch2) for all structures.

Two Viking spacecraft have successfully soft landed on the surface of Mars. Each carries, along with other scientific instruments, one biology laboratory with three different experiments designed to search for evidence of living microorganisms in material sampled from the Martian surface. This 15.5-kg biology instrument which occupies a volume of almost 28.3 dm; is the first to carry out an in situ search for extraterrestrial life on a planet. The three experiments are called the pyrolytic release, labeled release, and gas exchange. The pyrolytic release experiment has the capability to measure the fixation of carbon dioxide or carbon monoxide into organic matter. The labeled release experiment detects metabolic processes by monitoring the production of volatile carbon compounds from a radioactively labeled nutrient mixture. The gas exchange experiment monitors the gas changes in the head space above a soil sample which is either incubated in a humid environment or supplied with a rich organic nutrient solution. Each experiment can analyze a soil sample as it is received from the surface or, as a control, analyze a soil which has been heated to above 160°C. Each instrument has the capability to receive four different soils dug from the Martian surface and perform a number of analysis cycles depending on the particular experiment. This paper describes in detail the design and operation of the three experiments and the supporting subsystems.

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An integral method is used to obtain a solution for laminar flow of a compressible Newtonian fluid between rotating disks. The solution method is based on a Galerkin approach to the solution of the Navier-Stokes (radial, tangential, and axial momentum) equations, continuity, and on approximation of the energy equations. Four parameters are necessary to specify the flow: tangential inlet velocity, Reynolds number, a flowrate parameter, and Mach number of the disk tip. The solution is developed for turbine flow with uniform admission of the fluid at the outer boundary. The method can easily be extended to consider pump flow. Velocity profiles as well as turbine efficiencies are presented. Good agreement with published results for the incompressible regime is demonstrated. Short computational time and acceptable accuracy were obtained with a small number of terms in the velocity expansions.