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castings, bonded disks, metal-injected moldings and inertial welding.
Unique component designs must be pursued to allow UA engines to provide a high level of sophistication
while minimizing cost. Since part count is a major determinant of production cost, design features such
as drum turbo-machinery, slinger combustors, threaded casings, and integral blisks can reduce part count
by an order of magnitude. Low cost seals such as brush and finger designs have shown great promise for
replacing large, expensive labyrinth-type seals.
FIGURE D-2. JETEC COST GOAL IN COMPARISON TO EXISTING SYSTEMS.
Development costs can inhibit a buyer from pursing a new engine design. This leaves only off-the-shelf
systems that typically have less than optimal performance and/or cost for UA. These penalties can come
in the form of increased maintenance, decreased range or speed, increased production costs, or decreased
low observable (LO). To counter this and minimize development costs, industry must examine multi-use
concepts where a common-core can be incorporated into UA and commercial propulsion systems such as
general aviation, business jet, and helicopter gas generators. The payoffs are enormous for both
communities – decreased cost to the military and increased technology for the civilian sector.
Versatile Affordable Advanced Turbine Engines (VAATE). As currently planned, the
DoD/NASA/DOE VAATE initiative is ramping up over the next several years, and will follow and
build upon the IHPTET effort. Unlike IHPTET, which focused heavily on performance, VAATE will
build upon the technology advances of IHPTET, and concentrate on improving aviation, marine and
even ground-power turbine engine affordability, which proponents define as capability divided by
cost. VAATE's affordability orientation will look at technologies cutting engine development,
production and maintenance costs. The balance of the VAATE affordability improvements will come
from performance capabilities--technologies associated with boosting thrust and cutting weight and
UAS ROADMAP 2005
APPENDIX D – TECHNOLOGIES
Page D-3
specific fuel consumption. VAATE also emphasizes improvements to installed performance,
addressing overall performance improvements in addition to engine component technologies.
• VAATE is a two-phase program with specific goals. By the end of phase 1 in 2010, a six fold
improvement in affordability will be demonstrated, and at the end of phase 2 in 2017, a ten-fold
improvement in affordability will be demonstrated. Baselines for the effort are current state-ofthe-
art power plants such as the Honeywell F124 used in the Boeing X-45A UCAV
Demonstrator.
• VAATE work will be concentrated into three focus areas and two pervasive areas. Focus areas
will include durability; work on a versatile core, and intelligent engine technologies. Pervasive
areas, which are really incubators for hatching ideas that should be included in the VAATE focus
areas, will be segregated into the categories of high-impact technologies and UA.
Propulsion – Internal Combustion
Reciprocating internal combustion gasoline engines are widely used in fixed wing UA with take-off gross
weights less than 2,000 pounds. This is true among legacy UA, (Pioneer, Shadow 200, and Predator) and
numerous demonstration aircraft from both industry and government laboratories where two and four
cycle engines are used. While either cycle offers advantages and disadvantages, the demonstrated lower
cost and better efficiency of these engines precludes developing turbo-shaft engines to meet the engine
needs for UA in these size classes. However, these engines do not meet the requirements for a common
battlefield fuel as defined in DoD 4000. In addition, the engines tend to fall short in reliability/durability
as compared to man-rated aircraft engines, making them less attractive to warfighters who rely heavily on
the data received from their UA payloads to make real-time decisions. Future small UA will continue to
utilize these low cost, gasoline engines unless significant advances are made. Two potential areas are
weight reduction for true diesel cycle engines and successful modification of existing gasoline engines to
burn jet propellant (JP) fuels with increased reliability.
True diesel cycle engines had been precluded up to this time due to significantly higher engine weight as
compared to most gasoline engines. However, the advent of turbo-diesel technologies over the last few
decades, along with continuing development work with engine manufacturers to reduce the weight of
diesel engines has advanced the possibility of diesel engines being used by light aircraft. For example,
the Thielert Group in Germany has worked for many years to qualify several of their engines with the
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