AERODYNAMIC AND PROPULSION TEST UNIT
Published March 25, 2013
The Aerodynamic and Propulsion Test Unit (APTU) is a blow down wind tunnel designed for aerodynamic testing of supersonic and hypersonic systems and hardware at true flight conditions. Given its versatile design, APTU can support a myriad of test setups: propulsion, material, structures, store separation, and directed energy lethality/survivability.
A combustion air heater (CAH) provides the required temperature to simulate the enthalpy to which a flight vehicle is exposed during high-speed flight. The CAH is designed to operate over a range of total pressure from 50 psia to 2,800 psia and a range of total temperature from <1,000°R to 4,700°R. Liquid oxygen is added upstream of the CAH to provide the correct oxygen content (mole fraction) in the flow. The facility is computer-controlled during a run, and rapid transitions in pressure and temperature (altitude and/or speed changes) can be accomplished. Axisymmetric nozzles generate the required environments in the test section. Five fixed freejet nozzles are currently available to produce test conditions from Mach 3.1 to Mach 7.2. The remote location of the facility in addition to the straight line ejector exhaust configuration allow for unique test capabilities like ammunition, explosive or live-fire testing. The facility can be sited for 10,000 pounds of Class 1.3 explosives.
A 22,000-cubic-foot air reservoir, which can be pressurized to 4,000 psia, allows run durations from 30 seconds to 6 minutes, depending on the Mach number and altitude required for the run. This air storage system also supplies an annular air ejector, located in the exhaust duct. The ejector lowers the test cell pressure to minimize the facility startup loads on the test article, and to obtain/sustain altitude conditions in the cell during testing.
Cooling water is supplied to APTU from the AEDC pumping station through a 36-inch-diameter main pipe at 90 psig. This water can be used directly for low-pressure test article cooling requirements. If high-pressure cooling water is needed five pumps are available that can be used individually or in combination as necessary. Water pressure can be provided up to 2,000 psig.
An endothermic fuel heater is installed to support hydrocarbon-fueled testing of scramjet engines. The fuel heater is able to generate and control endothermically reacted hydrocarbon fuels up to 7.2 lbm/sec at 1,300°F. Greater fuel flow rate is available at reduced temperature output. Maximum heater operating pressure is 1,000 psia.
HISTORY AND FUTURE PLANS
From 1981 to 2005, APTU used its vitiated air heater (VAH) to conduct over 275 runs for a wide range of system development programs. The maximum pressure and temperature of the VAH were limited to 300 psia and 2,000ºR, respectively. Significant improvements in test productivity were made during that time frame with as many as four runs per day.
In 2002, under the High-Speed/Hypersonic Air-Breathing Propulsion Test and Evaluation Capability (HAPTEC) program, APTU began a series of major upgrades to provide a ground-test capability for supersonic and hypersonic systems up to Mach 8. Upgrades are planned through 2014 that will be implemented with minimal interference to customer test schedules.
Phase I of the upgrade, completed in 2004, modified the APTU utility supply systems (high-pressure air, isobutane, liquid oxygen and water) and replaced the air ejector system to increase the facility's altitude simulation capability.
Phase II centered on replacing the VAH with a much more capable high-pressure, high-temperature CAH. APTU in its CAH configuration reached initial operational capability of Mach 7.2 in September 2007.
Possible future upgrades that are being considered include variable Mach number test capability, and clean air heater technology.
The HAPTEC upgrades provide customers with a much needed ground-test capability for the research, development and acquisition of high-speed and hypersonic aerospace systems.