Ef
fi
ciency
,
%
(So
l
ar
C
e
l
l
s Only
)
15
FIGURE 4.3-1. MASS SPECIFIC POWER TRENDS.
TABLE 4.3-1. PROPULSION AND POWER TECHNOLOGY FORECAST.
Now 2010 2015
Turbine Engine Turbofan, turboprop, Integrated High Performance Turbine Engine Technology (IHPTET) Versatile Affordable Advanced Turbine Engines (VAATE-1) VAATE-II Note: VAATE ends in 2017
Hypersonics Scramjets AF Single Engine Scramjet Demo, Mach 4-7, X-43C Multi-engine, Mach 5-7 Robust Scramjet: broader operating envelope and reusable applications (e.g. turbine-based combined cycles) Hypersonic cruise missiles could be in use w/in operational commands. Prototype high Mach (8-10) air vehicles possible
Turboelectric Machinery Integrated Drive Generator on Accessory Drive, Integrated Power Unit – F-22 No AMAD, Electric Propulsive Engine Controls, Vehicle Drag Reduction/Range Extension Enabling electrical power for airborne directed energy weaponry
Rechargeable Batteries Lead Acid, NiCd, in wide use, Lithium Ion under development –(B-2 battery – 1st example) Lithium Ion batteries in wide use (100-150 WH/kg) Solid State Lithium batteries initial use (300-400 WH/kg)
Photovoltaics Silicon based single crystal cells in rigid arrays Flexible thin films Multi-junction devices – Germanium, Gallium based Concentrator cells and modules technologies (lens, reflectors)
Fuel Cells Prototypes demonstrated in ground-based assets. Production PEM/SO fuel cells available for UA Begin UA integration Fuel cells size/weight reductions Fuel flexible reformers
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Class A or B Mishaps per 100,000 Hours
900 800
700
600
500
400
300
200
100
0
FIGURE 4.3-2. MISHAP RATE COMPARISON.
4.3.5 Survivability
Aircraft survivability is a balance of CONOPS, tactics, technology (for both active and passive measures), and cost for a given threat environment. For manned aircraft, aircraft survivability equates to crew survivability, on which a high premium is placed. For UA, this equation shifts, and the merits of making them highly survivable, vice somewhat survivable, for the same mission come into question. Insight into this tradeoff is provided by examining the Global Hawk and DarkStar programs. Both were built to the same mission (high altitude endurance reconnaissance) and cost objective ($10 million flyaway price was not achieved by either program); one (DarkStar) was to be more highly survivable by stealth, the other only moderately survivable. Performance could be traded to meet the cost objective. The resulting designs therefore traded only performance for survivability. The low observable DarkStar emerged as one-third the size (8,600 versus 25,600 pound) and had one-third the performance (9 hours at 500 nm versus 24 hours at 1200 nm) of its conventional stable mate, Global Hawk. It was canceled for reasons that included its performance shortfall outweighing the perceived value of its enhanced survivability. Further, the active countermeasures planned for Global Hawk’s survivability suite were severely reduced as an early cost savings measure during its design phase.
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