Gardiner, Robert A

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RESEARCH MEMORANDUM 
A COMBINED AERODYNAMIC AND GUIDANCE APPROACH FOR

A SIMPLE HOMING-SYSTEM
By Robert A. Gardiner 
Langley Aeronautical Laboratory

Langley Field, Va. 
Liii 
EZ CLASSIFIED DOCUMENT 
This material contains information affecting the National Defense of the United States within the meaning 
of the espionage laws, Title 18, U.S.C., Secs. 793 and 794 the transmission or revelation of which In any 
manner to an unauthorized person is prohibited by law. 
'. NATIONAL ADVISORY COMMITTEE . 
FOR AERONAUTI 
WASHINGTON 
November 2, 1953
https://ntrs.nasa.gov/search.jsp?R=19930087905 2020-06-17T11:46:10+00:00Z
NACA EM L5311 	
Pi:.I 1Oa' NP,
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 
RESEARCH MEMORANDUM 
A COMBINED AERODYNAMIC AND GUIDANCE APPROACH FOR 
A SIMPLE HOMING SYSTEM 
By Robert A. Gardiner 
This paper deals with the study of a system in which simplicity was 
achieved by eliminating many components. The basic idea of this system 
involves the use of aerodynamics to help in reducing homing-system com-
plication and aid in increasing missile reliability. By using flicker 
controls operating directly from the target position as a primary refer-
ence, by using the rolling of the missile to scan the seeker field of 
view, and by using a rotating lift vector, several control system and 
guidance functions may be eliminated from an air-to-air missile with a 
corresponding increase, in ruggedness and simplicity. 
This subject will be described in the following order: the air-
frame characteristics, the seeker characteristics, and the combined 
operation of the airframe and seeker necessary to obtain this simplifi-
cation. 
In order to make a realistic analysis of the system, aerodynamic 
and guidance hardware has been chosen on the basis of availability and 
aithplicity. The airframe, shown in figure 1, is a canard configuration 
with the front-end (seeker, control system, and control surfaces) bearing 
mounted free to roll on the aft end. The bearing-mounted front end 
improves the quality of roll control since roll inertia is reduced and 
aerodynamic-induced rolling moments are minimized. 
The control end of the airframe is shown by the sketch in figure 1. 
Two of the canard surfaces are used as ailerons, and the other two are 
used as elevators. The flicker roll control used requires that the 
ailerons be deflected fully in one direction or the other, while the 
elevators are fixed at incidence. 
The nose design has been influenced by the choice of guidance. A 
drag-reducing windshield is supported by a tripod in front of a flat 
pyrex plate-glass window. Behind the window, shown dashed, are the mir-
ror and infrared detector. A lead sulfide cell has been chosen princi-
pally because of its ruggedness and adaptability for test purposes. This 
is followed by the electronic element, containing seven vacuum tubes, and 
power supply. A pneumatic supply and regulator are in the next section 
which also contains the aileron actuator.
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The seeker used with this system must be capable of detecting tar-
gets within a narrow rectangle about 50 long by 10
 wide. The elements 
of this detecting system are boresighted, as shown in figure 2, with the 
missile axis in such a manner as to aline one end of the detecting rec-
tangle with the axis around which the missile rolls, while the other end 
is aimed in the direction of lift. No gimbals are necessary since pur-
suit navigation is used. 
In operation the airframe and seeker function together as follows: 
When the missile rolls, the seeker scans a 12 0 included angle cone with 
about a 20 central dead zone. Figure 3 illustrates this operation. If 
a target is located within the active area of this cone, as the missile 
rolls the detecting area will cross the target and produce a signal. 
This signal is used to reverse the ailerons causing roll In the opposite 
direction. This causes the detecting area to recross the target and 
again reverse the ailerons. Thus, the missile hunts in roll on the 
target. 
As the missile hunts, the flight path of the missile is curved 
towards the target, since the detecting area and the lift of the airframe 
are aimed to produce this direction of flight-path correction. As the 
flight path curves, the relative motion between missile and target causes 
the target to appear to move towards the center end of the seeker rectan-
gle. When the missile is pointed directly towards the target, the target 
moves into the central dead spot of the seeker, the roll control is 
inactive, and the missile rolls continually while moving towards the tar-
get on an effective straight flight path. 
Another way in which the system operation may be described is by 
use of the block diagram shown in figure 1. The blocks representing 
roll response, angle-of-attack response, and flight-path response are 
airframe responses. The optic block and geometry block are guidance 
functions and represent the seeker and the geometry. The feedback indi-
cated from angle of attack to the optic input occurs since the seeker is 
fastened to the airframe without gimbals. The primary feedback of geom-
etry and flight path represents the target motion towards the center of 
the seeker cone. The roll feedback to the-optic input Illustrates the 
roll control system and represents the roll hunting action. An input to 
angle of attack from roll angle is shown and represents the rotating lift 
vector and illustrates the point that the direction of lift is dependent 
on the roll angle. 
Two modes of operation of the airframe are used to obtain a pursuit 
chase of the target. During search or during "on target operation the 
missile rolls continually while trimmed in a lifting condition. This 
results in a small-diameter (about 3 ft) helical motion, shown in fig-
ure 5, while the missile pursues an effective straight flight path. 
When flight-path correction is needed, a flicker roll system functions 
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to point the airframe lift towards the target path and produce the 
required corrections. The only moving controls are ailerons which are 
actuated by the flicker roll control operating directly from target posi-
tion as the primary reference. 
When a symmetrical airframe is subjected to combined pitching, yawing, 
and rolling motion, as is the case with this system, gyroscopic and other 
coupling between rolling and the other motions can occur. This has been 
demonstrated by Phillips (ref. 1) and by Nicolaides (ref. 2). The effect 
of this coupling is shown by a plot of pitch amplitude ratio against roll 
frequency (fig. 6). For this system the operating point for constant roll 
and for roll hunting has been kept low to avoid undesirable resonance 
effects. 
To determine the limitations of the system and to get a quick view 
of the type of operation which could be expected, a one-to-one time-scale 
simulator was constructed using two moving carts operating on a reduced 
geometry scale of 30 feet equal to 1 mile. Actual guidance hardware was 
used on the missile cart shown in figure 7(a). This hardware was mounted 
on a driving motor chosen to simulate properly the inertia and damping of 
the airframe in roll. This roll simulator was gimbaled and spring-
restrained so that the gimbal inertia, spring, and damping simulated the 
airframe short-period pitch and yaw oscillation. Two gimbals were used 
so that both pitch and yaw were represented. The steering gear was 
directly coupled to .the yaw gimbal so that the steering angle was equal 
to the angle of sideslip. 
An automobile headlamp bulb was mounted on the target cart, fig-
ure 7(b), to simulate the exhaust of a jet airplane target. The missile 
cart was accelerated to a speed representing Mach number 1.6 while the 
target cart ran at a speed representing Mach number 0.8. Various angles 
of launch, from 00, directly behind the target, to 450 off the tail of 
-the target, were tried, as well as several launching ranges. 
Qualitatively, the nature of the system operation was judged from 
this simulator and found to be quite satisfactory. However, due to the 
reducd geometry scale and the physical size of the components, accurate 
measurements at small ranges could not be made. 
In order to provide a more accurate determination a reduced-time-
scale simulation was set up using REAC equipment plus an auxiliary non-
linear device to represent the optical system and roll control system. 
The BEAC was used to represent the airframe and part of the kinematic 
geometry. The remainder of the geometry, the optical system, and the con-
trol system were simulated by a cathode—ray oscilloscope (used to present 
target position), an optical and photoelectric pickup, and an electro-
mechanical roll simulator.
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With this equipment, the missile launching range and angle off the 
tail of the target to assure a successful flight (a hit) could be deter-
mined accurately. These coordinates were obtained for all significant 
position's in the area surrounding the target. This was found to be 
divided into a firing area where a hit was always obtained and an area 
from which a hit is impossible as shown in figure 8. 
The useful area is fairly large considering the type of navigation 
used and almost coincides with the infrared signal cone to be expected 
from jet aircraft. 
It should be noted that this confirms previous work which has been 
done on pursuit navigation (ref. 3); however, it is believed that the 
useful firing area is larger than it as generally been thought to be. 
From this investigation, it may be concluded that a homing system 
has been devised which attains simplicity by utilizing several aerody-
namic properties of the airframe. The possibility that a similar reduc-
tion in complication could be made in the case of other systems should 
be investigated. 
Another conclusion is that a missile using pursuit homing has a use-
ful firing area which may well be large enough to be tactically useful. 
Langley Aeronautical Laboratory, 
National Advisory Committee for Aeronautics, 
Langley Field, Va., August 27, 1953. 
REFERENCES 
1. Phillips, William H.: Effect of Steady Rolling on Longitudinal and 
Directional Stability. NACA TN 1627, 198. 
2. Nicolaides, John D.: On the Free Flight Motion of Missiles Having 
Slight Configurational Asymmetries. Paper presented at 21st Annual 
Meeting, I.A.S. (New York), Jan. 26-29, 1953. (Preprint No. 395.) 
5. Watkins, Charles E.: Paths of Target-Seeking Missiles in Two Dimen-
sions. NACA WE L-735, 196. (Formerly NACA ACR L6BO6.) 
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A combined aerodynamic and guidance approach for a simple homing system

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