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is adopting this approach to achieving interoperability (through efforts such as NATO Standardization
Agreement (STANAG) 4586) that will foster an environment supporting C4ISR support to the warfighter
from UAS regardless of manufacturer, UA, or GCS.
As for those UA remaining under human control, the controller will eventually be linked to his remote
charge through his own neuromuscular system. Today's ground station vans are already being superseded
by wearable harnesses with joysticks and face visors allowing the wearer to "see" through the UA sensor,
regardless of where he faces. Vests will soon provide him the tactile sensations "felt" by the UA when it
turns or dives or encounters turbulence. Eventually, UA pilots will be wired so that the electrical signals
they send to their muscles will translate into instantaneous control inputs to the UA. To paraphrase a
popular saying, the future UA pilot will transition from seeing the plane to being the plane.
Recommended Investment Strategy: Focus DoD research and development on improved standards,
improved man/machine interfaces for UAS, conformal low observable antennae, and advanced UA
management systems.
Unmanned aircraft already exploit more forms of propulsion than do manned aircraft, from traditional gas
turbines and reciprocating engines to batteries and solar power, and are exploring scramjets (X-43), fuel
cells (Helios and Hornet), reciprocating chemical muscles, beamed power, and even nuclear isotopes.
Technological advances in propulsion that were previously driven by military-sponsored research are now
largely driven by commercial interests—fuel cells by the automotive industry, batteries by the computer
and cellular industries, and solar cells by the commercial satellite industry. UAS are therefore more likely
to rely on COTS or COTS-derivative powerplants than their manned predecessors were; Global Hawk
and Dark Star both selected business jet engines in their design. Because endurance (“persistence”) is
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UAS ROADMAP 2005
recognized today as the prime attribute of an UA when compared to manned aircraft, and endurance is
determined largely by the efficiency of the powerplant, propulsion is, with processors, one of the two key
UA technologies.
Two key propulsion metrics are specific fuel consumption (SFC) for efficiency and specific power (SP)
for performance. AFRL’s Versatile Affordable Advanced Turbine Engines (VAATE) program aims to
achieve a 10 percent decrease in SFC by 2015, while improving thrust-to-weight (T/W) by 50 percent and
lowering engine production and maintenance costs. Reciprocating engines for aircraft generally produce
1 hp per pound of engine weight (746 watts/lb), and today’s fuel cells are approaching this same level,
while lithium-ion batteries have about half this SP (See Figure 4.3-1). Fuel cells in particular are
expected to show rapid advancement over the coming decade due their increasing use in hybrid
automobiles. Heavy fuel engine (HFE) technology has advanced over the last few decades to the point
where replacement with internal combustion engines on tactical UA is now practicable. However, further
HFE development investment needs to be made to make their use on small UA practicable. Additional
investment also needs to be made in turbine technology for a J-UCAS class engine with a high thrust to
weight ratio and low SFC. Specific power trends in propulsion and power technology are forecast in
Figure 4.3-1 and Table 4.3-1.
Recommended Investment Strategy: Focus DoD research on developing diesel reformaters for fuel cell
use, enhanced engine durability and time between overhaul, improved specific fuel consumption for
enhanced endurance, and alternative propulsive power sources like fuel cells, photovoltaic, and nuclear
propulsion systems.
4.3.4 Reliability
Aircraft reliability and cost are closely coupled, and unmanned aircraft are widely expected to cost less
than their manned counterparts, creating a potential conflict in customer expectations. The expected
benefit of lower unit prices may be negated by higher attrition rates due to poorer system reliability. The
impact of reliability on UA affordability, availability, and acceptance is described in detail in Appendix
H. Figure 4.3-2 illustrates how the mishap rates of larger UA compare to that of representative manned
aircraft (F-16 and U-2) after similar numbers of flying hours have been accumulated. Since UA fleets are
generally smaller than manned fleets, they have accumulated flying hours at lower rates resulting in
slower progress down this curve. As an example, the MQ-1 Predator fleet just reached the 100,000-hour
mark in October, 2004, 10 years and 3 months after its first flight, whereas the F-16 reached this same
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