How
to Colonize an Asteroid
How
to Colonize an Asteroid
Different weights and lengths of projectiles travel through the accelerator at different speeds. For this reason, we must have a way of detecting the projectile as it enters the next coil. The detector circuit should trigger the next capacitive discharge power supply just as the projectile enters the next coil in line. If the timing is correct, the projectile will be accelerated as it passes through each coil. If the timing is off, the other coils could actually slow or stop the projectile. I even had one shoot backwards out of the tube once - it had actually just passed a coil when the supply was triggered, and the projectile was in just the right position to be fired in reverse. Again, please use caution and common sense if you attempt to build this project!
My detectors pass a pulsed optical
beam through the straw, which is detected by a sensor on the opposite side
of the tube. When projectile breaks the beam, a "missing pulse detector"
triggers the gate of a Silicon Controlled Rectifier (SCR), which dumps the
charge of a capacitive discharge supply through the next coil. I mounted
my detectors on clothespins which allowed me to slide them back and forth
on the wooden guide dowell to adjust the timing of the coil firing. The reason
for using the pulsed beam is to prevent interference from ambient lighting.
My system uses a 555 timer IC free running at around 350KHz (350 thousand
cycles per second). The pulses are fed directly to LEDs on one side of the
accelerator tube.
The pulses of light
travel through the transparent tube and are picked up by a phototransistor
on the other side. The photo transistor feeds the pulses to another 555 timer,
which is set up as a missing pulse detector. The output of the missing pulse
detector is fed into an inverter, and then used to trigger the next
coil.
Another detection scheme would be to use another small coil hooked up to an instrumentation amplifier. When a ferrous object passes through a coil of wire, it induces a small current (this is the basic principle of a generator). If you amplify and condition this signal, you can use it to trigger the next coil.
Whatever you arrive at for a detector circuit must supply a trigger pulse to the SCR on the capacitive discharge power supply.
