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 7 hours 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 wouldn’t seem so great if I first took a smaller step. Thus was born the second rocket in the GLYPO series, the 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 makes 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.
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 the Enguage Digitiser. It now better represents the AeroTech data, with near identical impulse. I have included the RASP file should others wish to use it.
AeroTech F40-7 (White Lightning) – The Winner
The F22 seemed like a great motor sitting midway in the F impulse class, but the 22 Newtons 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 Newtons 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 the blue. I have also included my profile below.
OpenRocket Design & Analysis
With the motor choice settled, the design commenced. One again I looked for a simple design with trapezoidal fins. I was able to quickly settle on the following design using a 2.1″ phenolic body tube, the AeroTech F40, birch plywood centring rings & fins, and a PML 2.1″ ogive nose cone .
| Length: | 67 centimetres |
| Mass with motor: | 482 grammes |
| Stability: | 1.22 cal |
From experience, I know there can be a big 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 metres / 1,780 feet |
| Time to apogee: | 9.5 seconds |
| Flight time: | 85 seconds |
| Max 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.
Leave a Reply