GLYPO-002 – One small step, one smaller leap
Having now built my Level-1 rocket I set about finding a suitable launch site and an RSO willing to assess my certification flight. My closest club is FOG in Wales but this site limits launches to G-impulse motors. The next nearest site, a mere seven-hour round trip, is Midlands Rocketry Club. I spoke with their Chairman, incidentally also the Chair of the UK Rocketry Association, Paul Carter.
The discussion with the Chair was very helpful. The upshot is that it would probably be best if I focused on a few mid-power flights. The leap from the C–D impulse rockets, that I am very familiar with, to an H-impulse rocket would not seem so great if I first took a smaller step. Thus was born the second rocket in the GLYPO series, GLYPO-002, an F-class rocket markedly smaller than GLYPO-001.
Rocket motors: the driver of design
Learning lessons from the previous build, I started with the motor selection. Having settled on AeroTech motors for my Level-1 rocket, it only made sense to continue this theme. The greater familiarity I gain with AeroTech the better, and to date I have enjoyed the responsiveness of their UK importer, Wizard Rockets.
AeroTech F22-7J (Black Jack) – the runner-up
First I explored the AeroTech F22-7J, which is a Black Jack motor and part of their 29 mm Reloadable Motor System (RMS). With a long burn time it should enable an entertaining long flight, and thankfully Wizard Rockets has the F22-7J in stock in the UK.
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As was the case previously, the thrust curve in OpenRocket (right) does not correspond to that from AeroTech (left). Therefore, I have taken the manufacturer’s curve and digitised it using Engauge Digitiser. It now better represents the AeroTech data, with near-identical impulse. I have included the RASP file should others wish to use it.
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Download F22-7J RASP file |
AeroTech F40-7 (White Lightning) – the winner
The F22 seemed like a great motor sitting midway in the F-impulse class, but the 22 N of average thrust was struggling to give me suitable performance for the size of vehicle that I am considering. The AeroTech F40-7 is also stocked by Wizard Rockets and gives a much heftier 40 N of average thrust.
Satisfyingly, the default thrust curve in OpenRocket is decent, as seen in the image below with my digitisation from the AeroTech website in red, and the in-built curve in blue. I have also included my profile below.
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Download F40-7W RASP file |
OpenRocket design and analysis
With the motor choice settled, the design commenced. Once again I looked for a simple design with trapezoidal fins. I was able to quickly settle on the following design using a 2.1 inch phenolic body tube, the AeroTech F40, birch plywood centring rings and fins, and a PML 2.1 inch ogive nose cone.
| Length: | 67 cm |
| Mass with motor: | 482 g |
| Stability: | 1.22 cal |
From experience, I know there can be a significant difference between as-designed and as-built, thus I am treating the simulation results as purely indicative at this phase. Once I have built GLYPO-002 I will revisit OpenRocket and update the simulations with the true mass values.
| Apogee: | 540 m / 1,780 ft |
| Time to apogee: | 9.5 s |
| Flight time: | 85 s |
| Maximum velocity: | 135 m/s / 302 mph |
I will of course blog in the near future with the build progress. What better way to end this post than with a gratuitous rendering of the rocket in flight.