August 2005, Issue 181

Flight Computer for High-Power Rocketry

ZSAT I TEST

I used the Mini-Me mission for more than my certification. I also used it as a test flight for my ZSAT I payload bay. Still buzzing from the flight, I ran down to vendor row and bought another motor reload. For the second flight, I put my ZSAT I flight computer in Mini-Me’s payload bay. This time I had an H248R. (I just love all this code stuff. The R stands for Redline). I saw a red flame as that baby burned. Cool.

I used the Z8F08200100 development kit for the ZSAT I. One of the microcontroller’s coolest features is its IrDA function. I cut out a small window in the payload bay so I can whip out my Palm OS cell phone on the launch pad and arm ZSAT I for flight.

On the launch pad, I loaded the igniter, hooked up the igniter clips, and then pulled the “remove before flight” pin. (I love this added touch.) On ZSAT I, I connected the 9-V battery’s positive terminal to the control electronics and took the negative terminal to the other side of a power jack mounted on the side of the rocket. The other side returns ground back to ZSAT I. When the flight pin is installed, the ground point is cut and the 9-V battery is disconnected from the electronics. Pulling the flight pin connects the battery to ZSAT I.

Now came the cool part. I whipped out my Palm OS cell phone, launched my Palm application called Launchpad, and beamed a control message via the IrDA port that told the ZSAT I to prepare for flight. ZSAT I returned with an acknowledgment and flashed the launch LED. The control firmware then started looking at the accelerometer and waiting for a change in its output, thus indicating Launch Detect. When Launch Detect is triggered, the control firmware samples the three sensors and saves the data in an SPI EEPROM device until it’s full.

I armed ZSAT I on the launch pad with my Palm OS cell phone, waited for my launch slot, and then let her go (see Photo 3). After takeoff, I tracked Mini-Me on foot. When I reached it, I saw a flashing LED sequence indicting that the EEPROM storage was full. Again, I whipped out my cell phone and asked the rocket for flight status over the IrDA port. The system quickly returned a snapshot of the rocket’s altitude, speed, and temperature: 3,400’, 620’ per second, and an average payload temperature of 83°F, respectively. The firmware can display only one value on the screen, but I plan to upgrade it in the near future so it will display a flight graph.

The launch at Black Rock was awesome. Because everything went as planned, I immediately started thinking about a Level 2 mission and a bigger, better IrDA flight computer: ZSAT II.