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mark in one quarter of that time and the 800,000-hour mark in that same time. However, the Figure
shows that the mishap rates of the recent, larger UA track closely with that of the F-16 fleet at a
comparable point in its career.
Recommended Investment Strategy: See “Recommendations” in Appendix H
Page 53
UAS ROADMAP 2005
28
25
20
15
10
5
0
30
2.5
2.0
1.5
1.0
0.5
0
Specific Power, hp/lb
Efficiency, % (Solar Cells Only)
1950 1960 1970 1980 1990 2000 2010 2020 2030
Silicon Cell Limit
Internal Combustion
Engines
Batteries
Solar Cells
(Efficiency Only)
Specific power of gas turbines
equals 4 to 10, depending on airspeed
VRLA
Alkaline FC
Alkaline
Space Shuttle
NiMH
Motto Guzzi
Rotax 914
GM
Li-ion Li-Poly
GM
GM
GM
Fuel Cells
GM
NiCd
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
Page 54
UAS ROADMAP 2005
0
100
200
300
400
500
600
700
800
900
100 1,000 10,000 100,000
Cumulative Flight Hours
Class A or B Mishaps per 100,000 Hours
Pioneer
U-2
Global Hawk
Hunter
Predator
F-16
Shadow
4.3.5
FIGURE 4.3-2. MISHAP RATE COMPARISON.
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.
The value of survivability in the UA design equation will vary with the mission, but the DarkStar lesson
will need to be reexamined for relevance to future designs. To the extent UA inherently possess low or
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