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are available to perform the mission. If one or more of the assets are destroyed, the mission can still
accomplished at lower life-cycle cost. A more critical mission in a higher threat environment increases
the importance of survivability design features. If few assets are available, completing the mission the
first time and with a single vehicle may be imperative. It is important to weigh all the factors in
determining how “survivable” a UAS must be to fulfill its specified functional capability.
By considering survivability early in the design process one can make design trade-offs and minimize the
potential cost and performance impacts. Modifications later in the design cycle will always come with
increased cost and performance penalties. If survivability is considered early in the design process there
are “no cost” design practices that will enhance a system’s survivability. An example is the placement of
critical systems to shield them from ground fire. No matter what decisions are made, considering all
facets of the design early will decrease the overall system life-cycle cost. For combat aircraft,
survivability must be a part of the trade space.
UNMANNED AIRCRAFT SYSTEM SURVIVABILITY CONSIDERATIONS
Regardless of size or cost, all UAS have the following functional components: (1) one or more aircraft,
(2) a system for command and control of the aircraft and associated payloads, (3) payload(s) and (4) a
means of disseminating the information obtained by the payload. Each of these functional components is
addressed separately below.
Aircraft
UA range in size from under one foot flying at 100 feet at 20 knots to those with wingspans over 130 feet
flying at 60,000 feet at 340 knots. A standard survivability approach will not work for all aircraft because
of this wide range of sizes and performance. Passive susceptibility reduction measures, such as visual and
acoustic signature reduction, may be the only way to increase the survivability of small aircraft due to
their limited size. Larger aircraft can support the introduction of active susceptibility reduction measures
UAS ROADMAP 2005
APPENDIX K – SURVIVABILITY
Page K-3
such as flares, chaff, other decoys, and/or traditional aircraft vulnerability reduction design concepts. The
cost and intended purpose of the unmanned aircraft system will inform the decision to invest in the
survivability of the aircraft.
Command and Control System
All current UAS have a command and control system for preprogramming the flight and/or direct remote
piloting. The sophistication of the command and control system varies, but generally consists of uplink
and downlink communications, navigation equipment and Global Positioning System, applications
software to control the aircraft and the payload. These links may be encrypted, but often are not. UAS
have a ground station that may range from a laptop in the hands of a soldier or Marine in contact with
hostile forces to a fixed plant installation within the continental United States. The physical threat to the
ground station varies according to size and employed location. The uplink transmits command and
control information from the ground station to the UA while the downlink provides health and status
information from the UA to the operator. Information for the control of the payload can also be
transmitted in the downlink. Generally, these communications channels emit continuously, thereby
allowing radio direction finding techniques to be employed against the ground station and its UA.
Depending upon the UAS, the command and control links may be interleaved with the payload (i.e.,
information dissemination) data link or there may be two separate links.
Data links are susceptible to jamming and intrusion by hostile forces. Jamming may degrade the ability
of the system to transmit signals between the ground station and the UA, especially if the antenna on the
UA is omni-directional, vice steerable. UA operating within radio line of sight from their control stations
are more likely to use an omni-directional antenna approach, while UA operating through communication
satellites are more likely to employ a steerable dish antenna with a relatively narrow beam. Unintentional
jamming from friendly or neutral communications emitters may also degrade the UA’s capabilities.
Hostile forces may intrude into either the C2 or the data link in order to take over the UA or degrade the
UA control or payload data reception so that it cannot carry out its intended mission.
Navigation equipment, often augmented by GPS, and mission management software provide the UA the
capability to fly a given route and collect the desired information. Because such navigation systems are
　
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