The Missile Works RRC² altimeter is one of the most attractively priced units available to the high power rocket community; my unit was under $100 including shipping. The size (Fig-1), simplicity, features and price contributed to my decision to purchase the RRC²; however reading through the very well done manual convinced me to place an order. The complete RRC² manual is available via downloading from the Missile Works web site.

I placed my order through the Missile Works on line store and received it in less than a week. The RRC² is a well thought out quality product.

The unit is a bit longer than I had anticipated, which ruled out it’s use in one of our rockets. The large screw terminals are easy to use and any small screw driver should fit.

The onboard battery has a clip to make sure it stays where it belongs. A piezo beeper, LED and five dip switches allow you to communicate with the RRC².

The RRC² has all the basic functions you would expect from a reasonably priced altimeter; mach delay setting of four or eight seconds, standard dual deployment with apogee and main chute deployment at 300, 500, 800, or 1000 feet; and a redundant apogee mode which fires the main chute (J2) one second after the apogee chute (J1). This gives you a backup on your rockets not using dual deployment.

A fresh 9 volt battery is always recommended for use with altimeters or timers to assure the flashbulb or electric match fires, but how do you know the state of your battery?

The manual explains the use of a multimeter with a 10 amp DC current measurement. An analog multimeter will work best, my digital meter was not able to perform the test properly. They recommend a current reading of at least two amps when the leads of the meter are connected to the battery; I prefer at least a five amp reading.

Make the measurement quickly; the test is almost the equivalent of shorting out the battery. Check brand new batteries too, they're not always as fresh as you would think.

Before using the altimeter, thoroughly read the manual to become familiar with all the functions of the RRC². Knowing your equipment inside and out comes in handy when your out at the pad; your mind has a way of blanking out just when you need it most, before the launch. Take time to run through the on board diagnostics and fire off a couple flashbulbs or electric matches.

I cut a section of 38mm motor mount tubing one inch longer than the RRC² and put four 3/8 inch holes in it (Fig-2). Each end is plugged with 1/2 inch thick foam pads to help protect the unit. I simply place this tube in the rocket.

The manual gives guidelines for the required static pressure ports which you will need to drill in your airframe. All my larger rockets have an access door to the electronics bay. I have found this to be the only easy method of arming the electronics at the pad.

I have done away with external switches or safety pull plugs; switches can shift from the forces of the rocket; the sockets for safety plugs are usually of poor quality. When I prep the rocket (away from the pad), I first check the continuity of the flashbulbs or electric matches for open or short state; I then connect two wires to the connections for the on off switch and connect the flashbulb charges to the RRC² and power it up by twisting the two wires together (Fig-2).

After the RRC² goes through a fifteen second self test it will beep out it’s status; one beep if only the apogee (J1) is connected. Two beeps for the main chute (J2); and three beeps if both functions are to be used. Assuming the unit is giving you the correct message, separate the wires and put tape on the exposed ends.

When you get to the pad, simply reconnect the wires and tape them together, wait for the self test and double check that you hear the correct number of beeps; close the door, and it’s ready.

My RRC² has performed flawlessly, I have used it for several dual deployment flights (Fig-3) with the main deployments set at 500 or 800 feet. I also have used motor ejection for the apogee and the RRC² to fire a second or backup chute at 500 or 800 feet.

If the design of you rocket permits, you could use the RRC² for apogee only and use the motor with a longer delay as a backup. When you recover your rocket, the RRC² will be announcing the altitude via the beeper.

The RRC² may be missing a few bells and whistles of other more expensive altimeters, however the performance and value make it great buy.

Documents:

Model RRC² - Rev. A (Rocket Recovery Controller) User Manual and Instructions
Model RRC² - Rev. B (Rocket Recovery Controller) User Manual and Instructions
Model RRC² - Rev. C (Rocket Recovery Controller) User Manual and Instructions
Model RRC²X (Rocket Recovery Controller) User Manual and Instructions