REDSTONE ARSENAL, Ala., — May 3, 2026 : The United States Army has issued a formal solicitation for a precision closed-circuit wind tunnel to support its primary measurement standards laboratory, as part of efforts to enhance calibration accuracy across its testing infrastructure.
The solicitation was released on May 1, 2026, by the Army Contracting Command at Redstone Arsenal. The procurement is being conducted on behalf of the U.S. Army Test, Measurement and Diagnostic Equipment Activity, which oversees calibration and measurement standards for Army systems. Vendors have been given until May 18, 2026, to submit proposals. The acquisition was formally authorized through a memorandum dated March 31, 2026, signed by contracting officer Portia R. Sampson.
Laboratory Role and Installation Site
The wind tunnel will be installed at the Army Primary Standards Laboratory (APSL), located in Building 5435 on Fowler Road within Redstone Arsenal. The APSL functions as the Army’s central facility for maintaining primary physical standards used to calibrate measurement instruments deployed across operational and testing environments.
Personnel at the facility are responsible for ensuring that calibration benchmarks for devices such as pressure sensors, velocity gauges, and diagnostic equipment remain accurate. Any deviation at this level could propagate through multiple layers of testing systems, affecting reliability across Army programs.
Integration with Laser-Based Measurement Systems
The new wind tunnel will be designed to integrate with a Laser Doppler Velocimetry (LDV) system, a method used to measure airflow velocity by analyzing laser light scattered from microscopic particles suspended in moving air. This technique enables highly precise velocity measurements, particularly at low-speed ranges.
By pairing the wind tunnel with LDV capabilities, USATA aims to extend its measurable velocity range downward while simultaneously reducing uncertainty in laboratory measurements. The system will use Bis(2-ethylhexyl) sebacate as the seeding material required for LDV operation.
Closed-Circuit Design and Airflow Stability
The Army has specified a closed-circuit configuration for the wind tunnel. This design allows air and seed particles to be continuously recirculated, maintaining a consistent concentration of particles within the airflow. In contrast, an open-circuit system would expel these particles after a single pass, reducing measurement stability.
To support particle injection, the system must include a 3/8-inch Swagelok bulkhead fitting positioned upstream of the test and transitional sections. This ensures controlled introduction of the seeding substance into the airflow.
Performance Specifications
The requested wind tunnel must operate across a broad range of airspeeds for a compact laboratory system. The maximum airspeed requirement is approximately 50 meters per second (about 9,900 feet per minute), while the minimum speed must reach as low as 0.15 meters per second (around 30 feet per minute).
To achieve stable low-speed airflow, the design incorporates specialized nozzle restriction plates. These plates are mounted into 6.85-millimeter-thick grooves that extend along roughly 75 percent of the test section length.
A critical performance requirement is turbulence intensity, which must remain below 1 percent throughout the entire operational range. Maintaining low turbulence is essential for ensuring predictable airflow conditions and minimizing noise interference in precision measurements.
Test Section Configuration and Optical Requirements
The wind tunnel’s test section measures 101.6 by 101.6 millimeters, forming a compact square cross-section. Despite its size, the section must support high instrumentation flexibility and optical precision.
Sidewalls must be constructed from optical-quality glass to allow distortion-free transmission of laser beams used in LDV measurements. The system will operate with an argon-ion continuous-wave laser, delivering up to 500 milliwatts of output at a wavelength of 532 nanometers.
The test section must also include at least two sealable ports designed to accommodate standard calibration instruments, including Pitot-static tubes and hotwire anemometers. These ports must accept devices ranging from 4.3 millimeters to 15.9 millimeters in diameter.
Port placement is precisely defined: one port must be centered 49.5 millimeters from the inlet, while the second must be positioned with a 37.5-millimeter offset.
Control Systems and Security Requirements
Airflow within the tunnel will be generated using a centrifugal fan connected to a motor through a variable-frequency drive (VFD). The fan assembly must be mechanically isolated from the tunnel structure to minimize vibration, which could otherwise affect measurement accuracy.
The control system must support both manual operation and computer-based control. The Army has specified that all computer-to-VFD communication must be wired, explicitly prohibiting wireless technologies such as Bluetooth and Wi-Fi due to security requirements.
Additionally, the system must be fully programmable using LabVIEW, ensuring compatibility with existing tools used by USATA personnel.
Validation and Compliance Requirements
To reduce the risk of post-delivery issues, the Army has placed responsibility for performance validation on prospective vendors. Bidders must demonstrate, through quantitative methods such as computational fluid dynamics (CFD) simulations, that their designs meet all specified velocity and turbulence criteria before acceptance.
The procurement falls under NAICS code 541715 and PSC code 6636. Delivery is required at the U.S. Army TMDE Activity, Attention: Michael Tyler, Building 5435, Redstone Arsenal, Alabama 35898.
Broader Context
Redstone Arsenal serves as a key hub for Army missile, aviation, and weapons development programs. The precision calibration capabilities maintained at USATA support a wide range of defense activities by ensuring that measurement systems used in testing and operations produce accurate and consistent data.
The acquisition of the new wind tunnel is part of ongoing efforts to maintain and enhance the Army’s measurement standards infrastructure, supporting both current and future testing requirements.
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