Unmanned Aircraft Systems Roadmap 2005-2030 - Federation of ...
Unmanned Aircraft Systems Roadmap 2005-2030 - Federation of ...
Unmanned Aircraft Systems Roadmap 2005-2030 - Federation of ...
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UAS ROADMAP <strong>2005</strong><br />
technology program the best that can be hoped for are mediocre solutions that meet some <strong>of</strong> our<br />
requirements, but fall significantly short in providing the true solution needed.<br />
Propulsion – Electric and Alternative Technologies<br />
Many <strong>of</strong> the smaller UA (mini- and micro-UA) use battery power instead <strong>of</strong> two-cycle engines. Low<br />
noise signature makes these electric drives attractive in many situations, despite the low efficiency and<br />
low power-to-weight ratios compared to reciprocating engines. Recent improvements in the ability to recharge<br />
lithium based batteries have resulted in significant logistics improvements for users in the field.<br />
Further improvements are needed in power-to-weight ratios for the next generation <strong>of</strong> batteries to improve<br />
the performance and endurance <strong>of</strong> these small platforms on a single charge. Currently, most batteryoperated<br />
MAV have a fraction <strong>of</strong> an hour <strong>of</strong> endurance, while mini-UA fair only slightly better, only<br />
because they can carry larger numbers <strong>of</strong> the same lithium-based batteries.<br />
Future-looking efforts for UA propulsion include the use <strong>of</strong> fuel cell- or nuclear-based power schemes.<br />
NASA has pushed fuel cell development for use in UA and by the Army's Natick Laboratory for soldier<br />
systems (i.e., small scale uses), and specific energy performance is approaching that <strong>of</strong> gasoline engines.<br />
The gaseous hydrogen fuel cells being used on NASA's Helios UA in 2003 have over 80 percent <strong>of</strong> the<br />
specific energy <strong>of</strong> a two-cycle gasoline engine (500 vice 600 Watt hours/kilogram) and 250 percent that<br />
<strong>of</strong> the best batteries (220 W hr/kg); further improvement is anticipated when liquid hydrogen fuel cells are<br />
introduced. Still in development by NASA are regenerative power systems combining solar and fuel cells<br />
in a day/night cycle to possibly permit flight durations <strong>of</strong> weeks or longer. Additionally, several<br />
commercial aviation initiatives are exploring fuel cells for both primary propulsion and auxiliary power<br />
units (APUs), see Figure D-4. In the nuclear arena, the Air Force Research Laboratory has studied the<br />
feasibility <strong>of</strong> using a quantum nucleonic reactor (i.e., non-fission) to power long endurance UA. However<br />
this remains a concept study, no prototypes or flight worthy hardware are currently planned.<br />
FIGURE D-3. ENGINE EFFECTS ON TAKE-OFF GROSS WEIGHT FOR A DESIRED MISSION<br />
ENDURANCE.<br />
APPENDIX D – TECHNOLOGIES<br />
Page D-5