无人机系统路线图 Unmanned Aircraft Systems Roadmap(86)

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Stand-off. During peacetime, the majority of airborne land and littoral ISR missions are accomplished using standoff techniques.  The standoff mode is also used during military operations when the risk is too great to expose platforms to a high probability of loss, or political sensitivities mandate constraint. Standoff UA designs need to emphasize the attribute of long endurance in order to achieve the effect of persistence.  If broad area coverage and/or extremely long-range sensor performance is required, then high altitude capability must also be emphasized.  Otherwise altitude performance should be dictated by the other requirements factors.  Additionally, while it is possible to equip a large UA with an impressive suite of imagery and signals intelligence sensors simultaneously, the question must be asked if this is the most efficient way to achieve the desired effect.  Lastly, while imagery, signals and measurement sensors generally have performed well in the standoff role, they face limitations against weak signals and very high resolution imagery requirements.  Weak signals are extremely difficult, expensive and possibly unaffordable for stand-off platforms to collect. These type sensors should be employed on platforms that can get close to, or over fly the targets, which can substantially reduce the complexity and cost of the sensing technology used.  Alternatively, small UA could be deployed to get in close and collect the very high resolution imagery and achieve greater success against the weak signals.

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Overflight. As discussed above, there are some cases where over-flight for collection purposes are required. This can occur during peacetime where political conditions support such missions such as, maritime surveillance, peacekeeping or GWOT, or in combat where a sufficient reduction in hostile air defenses has occurred.  There is no over-arching set of capabilities required for overflight, as there is in the stand-off or denied access roles.  If persistence is desired, then typically this would be achieved via long-endurance attributes between airframe shaping and engine choice.  Altitude would likely be dictated by the mission equipment being employed.  For collections against very faint signals, or requiring very high degrees of resolution, then medium to low altitude UA are probably the better choices. However, this introduces weather as a design consideration since medium to low altitude aircraft must operate in areas often plagued with icing and turbulence.  Once again, small UA should be considered in trade analysis because they can maneuver “under the weather” as well as get very close and use low cost technology to get high resolution results.  

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Denied access. In limited cases, access to denied areas is required to support combat or national requirements.  Generally this is achieved from space; however it is advantageous to have an airborne penetrating capability that arrives “unwarned” to prevent an adversary from denying collection due to the predictable nature of orbiting systems.  Previously, the DoD used manned platforms, most notably the U-2 and SR-71 although many other manned platforms of various types have been used on occasion. Clearly the disadvantage of manned platforms in a denied access collection role is the potential for loss of the aircrew and the diplomatic situation that would result (e.g., EP-3 incident).  As a result, UA are better suited to this mission area and have seen limited action in the past (e.g., D-21 and AQM-34 Firebee drones).  In the 1990s, the DarkStar UA system was developed using a different design philosophy than its predecessors.  However, it never reached operational capability. system was developed and operated in this environment.  The DarkStar’s primary platform attribute, survivability, must be the primary one of any UA designed for use in denied airspace.  Generally this dictates reduced signature with considerations for operating speed and altitude. Designing an ISR system to operate in the denied environment is more difficult than designing a strike system because the ISR system will complicate signature reduction by the incorporation of sensor apertures in numerous places across the platform.  The design of such platforms will have to strictly adhere to system design principles and trades to achieve the desired effect when employed.  The 2003 Defense
　
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