Live-TV-eye rocket photo.
Live-TV-eye spy camera in testing box.
The guys at work.
THE FLORIDA MOCKING BIRD
This rocket is named after the obnoxious state bird of Florida. The
little pest flies up to harass more refined birds that may happen to be
passing by. And this is what we have tried to do to fixed targets.
Our latest model followed after several earlier versions, always trying
to develop a better guided rocket after having discovered various flaws.
One major problem was visually trying to tell how close the rocket was to
the target at high altitudes. We tried opera glasses, binoculars and even
made an extreme-3D-viewer that used four mirrors to spread the operator's
eyes about 3 feet apart. It helped, but it wasn't the answer. We decided
instead to use the new micro TV cameras and an amateur TV transmitter.
The club also began a study of rockets and guidance. Since we evolved
from using free-rolling visual guidance to the latest version that has sun-eye
roll hold and a live-TV-eye in the nose, we have begun to appreciate the
difficulties involved. Difficulties are very informative!
The use of TV resulted after watching a video taken from a model
plane using tiny live-TV equipment. First, some layout decisions were made.
The camera is in the nose with wires attached. So we decided to put the
chute underneath the camera. The camera stays in place while the chute
ejects out a side port.
We could also have had chute ejection out the side right above the
motor, between the fins. This would use the motor's ejection charge.
This is simpler, saves weight and works even if something goes wrong with
the radio! That's probably best, but you need to be certain the motor's
ejection delay is right for your rocket's weight, and that the motors are
reliable. This rocket weighs 2.4 lbs. We chose 29 mm for our motors but
you can choose any diameter. By the way, you don't want high initial thrust.
Get "long burn" motors with low thrust.
You must have at least a technician class license to use the ham
transmitter, or have a licensed club member or club member's parent
operate it. The picture is received on CABLE channel 60 using a UHF
bow-tie ANTENNA. Be sure to set the VCR for cable reception. The signal
can also be received on an analog-tuner TV up past VHF channel 14 on
SOME portable analog TV sets.
The front of the PNC-70 nose cone was cut off in a lathe. The camera
was fitted inside the rear half. A clear plastic dome from a craft store
is used for the actual nose cone and is taped on.
The configuration is the same as the free-roll rocket and the sun-eye
roll-hold rocket, with large rear fins and canard control fins. There
are two hardwood rails thru the body that wood disks are mounted onto. The
assembly procedure sometimes looks like someone doing a wooden Chinese
puzzle, but we're in no hurry. The servos mount on the rails. Roll
control surfaces are inside the rear fins. The canard fins are the X and
Y control surfaces. The TV transmitter, radio receiver, batteries and
connectors nestle inside the rails, twist-tied in place. Common rocket
and plane model parts are used throughout. Fins are thin ply. They are
interlocked with each other and the body tube is slit for them, sliding
down over them. The base disk and the rails sit firmly on the top of the
fins. No force is put on the lower body tube. There is some thrust force
on the top body tube during acceleration due to the mass of the camera.
The highest voltage needed is the 12 volts for the camera and transmitter.
We use 250 mAh cells. This voltage is dropped down using a voltage regulator
IC to 4.8 volts for the radio and servos. The chute charge is ignited by a
micro servo contacting two wires on it's own channel. Two channels are used
for X and Y motion to match the joystick. The sun-eye roll hold circuit uses a
servo but no radio channel.
We use G motors to put this up 600 feet. There was a lot of extra hassle
to get bigger motors. I understand that now there are fewer restrictions.
You'll need an 8' or longer launch rod. Ours is 1/4" aluminum polished
using soapy steel wool. Stainless steel is best.
Since we built our rocket, there's been a lot of smaller, cheaper
cameras on the market. There are simpler-to-assemble TV transmitter
kits. Ours is a 2-watt version and it was a challenge to assemble and
tune properly. You now can get assembled transmitters. Now there are
more powerful composite rocket motors, or you can make your own.
Black powder has a specific impulse of 80 seconds, but composite's is
over 200 seconds. This is the same propellent used in the shuttle solid
rocket boosters and military missiles. If you want the big motors, the
motor makers and the "prefecture commandos" want you to buy them at launch
sites and use them there. But you can get the materials and make them
TRANSMITTERS AND CAMERAS:
North Country Radio
PO Box 53
New Rochelle, NY, 10804
Articles: 2-watt ATV transmitter:
73 (Amateur Radio Today) Magazine, Aug. '92, pp. 22-29
Sept. '92, pp. 50-56