SACLOS Autonomous Guidance Attempt
Our curiosity about rocket guidance led us to the concept of
semi-automatic-command-line-of-sight, or SACLOS. This is when
a sighting camera is zeroed in on and follows the target. The
system detects a light on the rocket and sends commands to make the
rocket impact the target. The system determines what corrections are
needed to get the rocket to impact the target using a complicated
algorithm based on dynamics. Before we studied it fully , we thought
the idea sounded simple enough, so we developed a circuit to turn the
rocket up if too far down, left if too far right, etc. We also wrote
simple BASIC programs to simulate this type of correction.
The simulations in two dimensions seemed to indicate a widening
weaving path rather than a narrowing one. We assumed we hadn't done
the programming correctly.
We designed and built a simple circuit to detect the flare on a
radio-control model car and send a signal the transmitter to automatically
correct the steering.
We first used a fireworks sparkler on the model at night. Not bright
enough on any camera setting. So we used several sparklers. Nope. So we
tried a very bright light bulb powered by the car's drive battery.
It worked! We were so proud, thinking the whole plan was coming together
already. Fools rush in. Lo and behold, it was doing the exact same thing
the computer simulation showed.
Not to worry. We'd just tweak it a little. We tried having less and
less steering wheel throw as the car moved farther away from the camera.
Nope. We tried more angle as it moved away. Nope. We were about to try
more angle the farther the car was from the sightline. But then we decided
the whole idea was wrong to begin with.
As we read about current military hardware, we noticed that the ones
the military now wanted all home in on an infrared LASER beam reflected
from the impact point. That definitely told us something. As we began to
read about SACLOS in library texts, we discovered it's very involved. It
also doesn't work nearly as well as reflected-beam homing.
But we kept the circuit boards and the three prototypes. We're just
proud of the simple circuit. It will keep a telescope trained on a star
for astrophotography, or any similar task.
The circuit uses all common electrical parts. See the schematic. We
originally had an old black-and-white vidicon TV camera that we tapped
to get the horizontal and vertical synch pulses, in addition to the
video. But it finally died and so we tapped into a 5", B&W, 12-volt
TV set that we had been using for a monitor. It plugs into a car
cigarette lighter. The camcorder we now use for video puts the signal
into the TV via a video modulator.
The tedious part of this project was adjusting the circuit pots so that
the timing of the pulses is right for positive operation.
SACLOS circuit photo.
SACLOS schematic diagram sketch.
The white spot in the upper right on the monitor is the flare. This would
normally be on the vehicle, plane or rocket being guided to the target.
Synch taps on TV board.
The white wire is the vertical pulse and the red wire is the horizontal.
R/C transmitter reed relays on pot wiper pins.