MIL-HDBK-1211(MI)
ble to predict accurately by simple analytical means. The
The inputs and outputs of a missile flight simulation are
most credible means is flight testing, but it is also the most
shown in Fig. 1-1. Inputs are data needed by the mathemati-
costly. Laboratory testing also provides credible informa-
cal models that may change from one computer run to the
tion, but it is restricted mainly to subsystem evaluation. Be-
next. Examples of inputs are initial conditions such as the
tween the extremes of low-cost, low-credibility analytical
positions and velocities of the missile and target at the instant
methods and high-cost, high-credibility testing methods is a
the simulation begins, programmed target maneuvers, and
gap filled by computer simulation (Ref. 1). Clearly, this is a
countermeasure control parameters. If the target model is a
wide gap that leaves room for wide variation in the sophisti-
general one, target signature data are treated as inputs. Data
cation of missile simulations depending on whether the simu-
that seldom or never change are usually built into the mod-
lation user's needs fall closer to analytical estimates or to
els. For example, a simulation of a specific type of missile
flight-test results. For example, a very simple simulation
usually has descriptive data built into the missile model, but
could determine the general size and shape of the area that
simulations of generic missiles or missiles not yet complete-
could be defended by a surface-to-air missile with a given
ly defined may be arranged so that parameters subject to
weight and thrust history. If the effects of seeker range lim-
change are inputs. Environmental conditions, e.g., atmo-
its, gimbal angle limits, and tracking rate limits on the size of
spheric density as a function of altitude, are usually built into
the defended area are of concern, these functions must be
the simulation; however, a nonstandard atmosphere or other
modeled in the simulation. If the contributions of various
variable environmental conditions can be selected by an ap-
missile design characteristics to miss distance are of interest,
propriate choice of input. Typical missile flight simulation
the functions contributing to miss distance must be included
outputs include the missile flight-path history and the result-
in the model, particularly those that relate to missile response
ing miss distance. Depending on the needs of the user, the
times and maneuver limitations. If emphasis is to be placed
time histories of many different missile functions and re-
on target tracking ardor guidance and control, more detailed
sponses may be outputs, such as fin deflection angles, mis-
missile function models are required, even to the point of us-
sile translational and rotational rates and accelerations,
ing actual missile hardware in the simulation and generating
seeker function, and control system function.
scenes for the hardware seeker to view. In general, as the in-
1-1.2 PUROSE OF A MISSILE FLIGHT SIM-
formation needs of the user become more detailed and re-
ULATION
quire greater precision, the simulation must become more
The performance of a missile system is determined by the
complex, refined, and detailed (Ref. 2).
interaction of all of its subsystems. Each subsystem compo-
1-1.3 IMPLEMENTATION OF A MISSILE
nent must perform its own function properly, and the integra-
FLIGHT SIMULATION
tion of all subsystems into a whole missile must be balanced
The performance characteristics of the first guided mis-
and tuned for best performance. Very small variations in any
siles were analyzed by using analog computers. The physical
component can unbalance the system and result in unaccept-
simulation consisted of patchboards with hundreds of wires
able missile performance. Missile designers and evaluators
making the electrical component connections required in the
use a variety of methods to obtain information on the perfor-
computer to solve the differential equations that described
mance of alternative missile configurations. These include
missile behavior. Today, except for some very specialized
analytical estimates, computer simulations, laboratory tests,
applications, analog computers have been replaced by digital
and flight tests as shown in Fig. 1-2. Simple analytical tech-
computers. A digital simulation consists physically of lines
niques provide estimates of missile performance characteris-
of computer instructions, usually stored magnetically on
tics, such as maximum range and time of flight, but the
disks or tape. Hard copy (printed on paper) and cathode-ray
detailed interactions of subsystems are difficult or impossi-
Figure 1-1. Missile Flight Simulation
1-2
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