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Thermo Mechanical Systems Co

High Altitude UAV Turbo Charger Systems

TMS has designed and developed a family of turbochargers with demonstrated compressor efficiencies up to 82% and turbine efficiencies of up to 88%. Current compressor designs produced by TMS range from 3-inch to an 8-inch diameter impellers and are configured with various numbers of blades and varying blade backsweep geometry designs. TMS has designed, fabricated and developed compressors capable of operating over a wide range of pressure ratios and stages of compression with single stage compression ratios of up to 6 to 1, two-stage compression ratios of up to 20 to 1, and three-stage compression ratios of up to 70 to 1.

In 1980 TMS was selected by Developmental Sciences Incorporated to develop a turbocharger system for an ultra high altitude (over 80,000 feet) UAV. The TMS engineering team succeeded in designing, fabricating and testing a three-stage turbocompressor system while simultaneously designing and building a High Altitude Test Facility (HATF) in which the engine and turbo system could be installed and tested at actual altitude conditions. This DARPA funded program evolved into the Boeing Condor, a high tech test bed reconnaissance vehicle that had its first flight on 9 October 1988 and set an altitude record of 67,028 feet for propeller driven aircraft. The Condor had an un-refueled flight duration of 80 hours and was powered by two 175 hp, six-cylinder supercharged Continental TSOL-300-2 engines driving 16 foot diameter propellers through two-speed gearboxes that shifted the propellers to higher RPM at high altitude. It logged over 300 hours of secret missions before its retirement.

Since then TMS has successfully developed turbochargers and turbocharged engine systems for many UAV platforms.

Recently, as a member of the NASA ERAST program TMS was selected to develop a turbocharged engine system for operating a UAV at altitudes up to 85,000 feet. Although an aircraft was never built for this application, TMS was successful in developing a three-stage turbocharged engine system for it. The engine and turbochargers were tested in the TMS HATF at altitudes over 85,000 feet and  performed flawlessly.

In all, TMS developed three different systems for NASA to turbo charge the ROTAX 912 engine on the Predator UAV airframe. The systems consisted of:

  1. a single stage turbo charger to increase the flat 100 horsepower rating of the engine on the RQ-1B to an altitude of 33,000 feet from 22,000 feet;

  2. a two stage system enabling the same airframe to reach 52,000 feet; and

  3. a three stage system elevating the 100 HP flat rating to over 80,000 feet.

The cases shown in the graph correspond to minimum sustainable operations at:

  1. 32,000

  2. 50,000
  3. 70,000 and
  4. 88,000 feet, respectively.

Rotax engines that were specially prepared by TMS for high altitude operation power the General Atomics Altus UAVs. One UAV, owned and operated by the Naval Postgraduate School utilizes a single stage turbo system. The other, part of the NASA ERAST program, utilizes a two-stage system. TMS has also supplied Scaled Composites a two-stage system for their Raptor UAV in order to reach altitudes of 65,000 ft. This propulsion package was successfully tested in the TMS altitude chamber to over 70,000 ft altitude.

The three stage system shown in the TMS high altitude test cell was developed for NASA to operate at altitudes of up to 90,000 feet. It demonstrated engine outputs of 100 horsepower up to 82,000 feet in the test cell.

 

Defense planning provisions exists for high-altitude long-range (HALO) platforms. General Atomics developed the Altus UAV, depicted above, for that purpose. Altus uses a modified Predator airframe with twin TMS turbochargers to boost the performance of the Rotax engine to reach 55,000 ft. So far, only a prototype has been built and is being used for recovery of meteorological data associated with lightning storms. The need for HALO platforms continues with new wing-based as well as airship programs in which TMS is participating. The potential for TMS high altitude turbochargers and air pressure systems for fuel cells remains favorable.

 

Field experience with the current versions of the Predator over Kosovo, Iraq and Afghanistan demonstrated that at present operational altitudes the system is vulnerable to enemy fire. With further development of more acute radar, laser and video systems it should become increasingly possible to operate as effectively at higher altitudes whereby the need for higher performance turbochargers should become more commonplace and offer new opportunities for TMS.