Gyroc 1 was the first actively stabilised model rocket developed and flown in the UK (to our knowledge). Using a custom gyroscope to give an inertial platform, a digital flight computer and a gymbal-mounted rocket motor, Gyroc 1 was able to remain vertical whilst under power. The project has been predominantly developed by James Macfarlane and Michael Procter, although others have also made valuable contributions.
My involvement with Gyroc 1 began in 1996, a few weeks before the International Rocket Weekend in Largs. Prior to this, James had already developed much of the hardware and mechanics. Hoping to complete the maiden flight at the IRW, he enlisted my help for the software. The first flight computer was built and the majority of the software was written in one rather frantic weekend. Subsequent refinements took place (particularly of the software, which I had hacked together somewhat too rapidly for bug-free maintainable code to emerge) before and during the IRW. Finally, we were in a position to launch the rocket. In what was to become the traditional launch schedule for Gyroc, the launch pad was set up as dusk started to fall. All but the most foolhardy (myself and James) were sent to retire at an extremely safe distance, and the countdown began.
The first flight was made on a D12, giving an initial peak thrust of around 12-14 Newtons, tailing off to just under 10 Newtons. The all-up mass of Gyroc was around 1kg. Consequently, Gyroc managed to clear the 1-foot launch rail, but only just. It managed to hover next to the rail until the motor burnt out, whereupon it fell to Earth. The crowd cheered - we had all just witnessed the first amateur actively stabilised rocket to be launched in the UK, and the flight had been a success.
This pattern was not to be repeated for several more launch attempts. James and I accepted that the first flight was probably more down to luck than judgement, and various changes were made to improve the reliability and repeatability of stable flight. With hindsight, it seems clear that if that first flight had not been a success, we may not have had sufficient confidence in the approach to make it work. But with the tantalising carrot of that first flight, we continued developments over the years.
Gyroc 2 was first flown in February 2002. Whilst externally, little appeared to have changed, there were some substantial internal developments. The most significant change was the removal of the custom gyro and the installation of 2 commercial solid-state gyros (at a not inconsiderable expense). We had come to the conclusion (correctly, as it turned out) that many of our problems could be traced to the mechanical soundness (or lack of) of the custom gyro. Repairing the graphite bearing and containment box after every flight should have been a warning that the structure was not ideally suited to the task in hand. Replacing the gyro was a major step forward in the development of Gyroc.
In addition, the avionics was rebuilt around a PIC16F877, thus removing the need for an external ADC. Since the custom gyro was no longer fitted, the gyro spin-up circuit could be disposed of. Finally, the original parachute timer was removed and firing the parachute was entrusted to the microcontroller. The final change was to enhance the gymbal motor mount to support larger motors. Now, with Aerotech 32mm motors, high altitude (>20') testing was possible.
After another frantic weekend of software development (changing the processor, adding calibration offset code for the gyros, implementing a small integrator), Gyroc 2 was ready to fly. As was customary, the launch took place as late in the day as the RSO would permit. All the extra development proved to be worthwhile, as the flight appeared to be almost flawless. The rocket ascended gently under power, drifting slightly downwind. It remained pointing vertically throughout the burn, with barely discernable deviation. The parachute deployed on schedule, but failed to deploy completely due to the presence of excess masking tape. Since that flight, Gyroc 2 has flown twice more. An mpeg of one of these flights is linked below.
Since we are now in the rather pleasant position of having achieved our primary goal (namely to actively stabilise a model rocket), we are able to decide where we wish to take the project from here. There are one or two obvious directions that could be taken, but only tentative plans have been made at this stage.
I have omitted much technical information concerning Gyroc from this page, for two reasons. Firstly, I didn't have all the details to hand during the initial composition, and secondly because a friend has already recorded much of the information on another site. Over time, I anticipate adding more material to this page, as I remember and also as I scan suitable pictures. In the meantime, a large MPEG of Gyroc 2 in flight is available. This flight was made in February 2002 in Lincolnshire. Many thanks to David Warman for providing me with the footage.
Many people have commented about the enormous amount of time that has been spent over the years developing Gyroc. It is true that the first flight was in 1996, and reliable stable flight only achieved in 2002. However, it is not true that the intervening five and a half years have been spent slaving over the development. I would estimate my total development time on Gyroc to be in the region of 2 weeks (two weekends, a day or so at each IRW, and a few miscellaneous evenings). James has certainly spent longer on the project, but I wouldn't guess more than a couple of months. The total elapsed time on the project has not been excessive.
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