The PAL: Planetary Aeolian Laboratory
The PAL – Overview
The Planetary Aeolian Laboratory (PAL) is a facility used for conducting controlled experiments and simulations of aeolian processes (windblown particles) under different planetary atmospheric environments, including Earth, Mars, and Saturn’s moon Titan. The PAL is currently supported by NASA’s Planetary Science Division (prior to 2014, PAL was supported by NASA’s Planetary Geology and Geophysics (PG&G) program). PAL includes apparatus and facilities at NASA-Ames Research Center (ARC) at Moffett Field, CA, and Arizona State University (ASU) in Tempe, AZ, supporting separate equipment for PAL activities. The PAL includes one of the nation’s largest pressure chambers for conducting low-pressure research. PAL also enables testing and calibration of spacecraft instruments and components for NASA’s Solar System missions, including those requiring a large volume of low atmospheric pressure.
Proposal Guide and Contacts
For researchers interested in writing proposals to NASA to conduct research in the PAL wind tunnels, please download and review the PAL “Guidebook for Proposers” at this link:
“Guidebook for Proposers” (2015, v6) [PDF, 3MB].
The PAL and resources are available to faculty, post-doctoral associates, graduate students, research assistants, and visiting scientists.
Planetary Geology Wind Tunnel at Arizona State University
The ASU wind tunnel (ASUWIT) consists of a 13.7-m long, 0.7 m high, 1.2 m wide open-circuit boundary-layer wind tunnel that operates under ambient temperature and pressure conditions and is capable of wind speeds of 30 m/sec. Air is pulled through the tunnel by a large fan mounted in the downwind section of the tunnel. A viewing area of the test bed is encased by plexiglass with doors to access the test section for the setup of experiments. The ASUWIT facility can measure wind speed, temperature and humidity inside the tunnel, and physical conditions in the room outside of the tunnel are also collected. These data include laboratory temperature, humidity and barometric pressure. Wind conditions exterior to the building, including wind direction and speed, are also recorded. Independent sources power the pressure transducers, humidity sensors, anemometers, and wind vanes.
ASU also has a vortex generator (ASUVG). The ASUVG consists of a large vertical fan mounted above a moveable table. The table can be moved across the X, Y and Z-axes during experiments. A variable speed motor controls the 0.5 m fan mounted above the testing table. A large board of pressure transducers is available and can be setup to collect wind pressure points in various areas of the test section. Currently the vortex generator’s data is fed to a Windows PC running LabView™. The test section measures 1.2 x 1.2 m. Fan position can be adjusted vertically and horizontally; likewise, the table can be adjusted in the X, Y and Z directions.
Planetary Wind Tunnels at NASA Ames Research Center, Mountain View, CA
Our facilities at NASA Ames consists of: (1) the Mars Surface Wind Tunnel (MARSWIT) and (2) Titan Wind Tunnel (TWT) located in the Structural Dynamics Building (N-242) at the NASA ARC in Mountain View, California that is administered by Arizona State University. The MARSWIT and TWT are supported by shops, instrument facilities, and imaging services at NASA-Ames. PAL facilities at ARC also have a full-time technician (an ASU employee working at ARC) to serve planetary users.
The Martian Surface Wind Tunnel (MARSWIT) at NASA-Ames was put into operation in 1976, and is used to investigate the physics of particle entrainment by the wind under terrestrial and Martian conditions, to conduct flow-field modeling experiments to assess wind erosion and deposition on scales ranging from small rocks to landforms (scaled) such as craters, and to test spacecraft instruments and other components under Martian atmospheric conditions. MARSWIT is a 13-m long open-circuit boundary-layer wind tunnel within a large environmental chamber that operates at atmospheric pressures ranging from 1 bar to 5 millibars, with maximum speeds of 10.5 m/sec at 1 bar and 100 m/sec at 5 millibars. The wind tunnel is an open-circuit design, but sits on the floor of a large pressure chamber with an inside height of 30 m and an interior volume of 4,000 cubic meters.
For low-pressure wind tunnel runs, the chamber is sealed and pumped down, and the open-circuit wind tunnel inside is operated within the low-pressure environment. Evacuating the interior pressure of such a large chamber requires a lot of power, which ordinarily would be quite expensive. PAL draws its vacuum power from the Thermal Physics Facilities’ Steam Vacuum System and can be evacuated to Mars analog pressure (4 torr) in about 45 minutes. Due to the high cost to operate the vacuum system an agreement was struck in which PAL draws its vacuum almost exclusively only as a ride-along with other NASA-Ames projects/facilities that sponsor the activities of the NASA-Ames steam plant. This arrangement is highly cost-effective, but requires advance scheduling of low-pressure runs (requiring pump-downs) well in advance. Aside from this agreement, reserved vacuum service is available, provided sufficient funding is presented and there are no scheduling conflicts.
The MARSWIT instrumentation includes differential pressure transducers (Setra 239 and MKS 226A) linked to pitot tube apparatus for measuring free-stream wind velocities and deriving wind profiles. Pitot tube options include singular, vertical traversing pitot tubes, and stationary multiport rakes that can be mounted on the test section floor if needed. These have a range of ±0.5 inches of a water column, or approximately 1.25 millibars. The MKS 226A specifies an accuracy of 0.30% of the instrument reading and a resolution of 0.01% of full scale. The Setra 239 specifies an accuracy of 0.14% of full scale. The Setra has been used in MARSWIT for many years and is reliable to measure velocities of 30-100 m/s at low pressure. The MKS is a new addition that will enable measurement of velocities below 30 m/s at low pressure. In addition, a Vaisala model DMP-248 dewpoint and temperature transmitter is used to monitor the temperature and relative humidity within the chamber. A DigiVac model 2L760 digital vacuum gauge measures the chamber pressure from Earth standard to the minimum allowable operating pressure (1 bar to 5 millibars) of the chamber. The MARSWIT is equipped with a high-speed (500k samples/second capability) analog-to-digital data acquisition system from National Instruments, Inc. Installed and operated on a dedicated computer, the system is capable of simultaneously measuring 64 analog channels, each of which can be independently accessed. The system is controlled by the National Instruments software package LabView™. This system allows for the simultaneous acquisition, analysis, and visualization of wind tunnel temperature, pressure, and velocity. Other analog and digital instruments can be incorporated to suit experimental requirements.
The TWT is a remodel of the Venus wind tunnel (operated 1981-1994), and became operational in June 2012. The TWT is a closed-circuit, pressurizable (to 20 bars) wind tunnel with an overall dimension of 6-m by 2.3-m. Included in the remodel were upgrades to a newer, higher performance motor, advanced motor controls, and new instrumentation. Overall tunnel pressure is determined by visual observation of a calibrated gauge (manufactured by Wika Instrument Corp., + or – 1psig) attached to the front of the tunnel instrument panel. Differential pressure is measured (for flow velocity calculation) by a custom designed sensor (manufactured by Tavis Corp.). This sensor is connected to a stack valve that determines which pitot tube is being “read” (traversing or fixed). The voltage from the sensor is sent to a data acquisition module (manufactured by Measurement Computing Corp.) and processed for interpretation by TracerDAQ software installed on a laptop computer. A test section is designed to allow the substitution of test plates. A test plate specifically designed for boundary layer profile work already exists and can be installed should the need arise.
Page last updated: Dec. 8, 2016