The name Cirrus is closely tied to the project goal. Cirrus is named for the type of feathery, high altitude clouds comprised of fine ice particles. These clouds, often seen embellished with whimsical-looking "mares' tails", are signs of fair weather, usually seen on sunny days accompanied by blue skies. These clouds inhabit the lofty heights of between 6000 and 20 000 metres. Often, in my childhood, I would glance up at the sky, with my attention focused on the far-off cirrus clouds, and imagine one day launching a rocket that would soar to such great heights. I was reared on the prairies, where the land is unimaginably flat and featureless. However, seemingly to compensate for this, the sky is immense. Coupled with the pure air frequently swept by northern winds, the cobalt-blue prairie sky provides an ideal canvas upon which one's imagination may paint abstract dreams of future endevours....

Cirrus One

View SOAR altitude simulation program output file for Cirrus One:  soar720.txt

Progress to Date:

• The overall geometry of the rocket has been finalized. Preliminary stability analysis with both CG and CP estimates completed (see Figure 1).
• Most of the parachute ejection system components have been made.
• Design of the nosecone has been completed and fabrication has begun. The moulds are currently being produced.
• The fuselage sections have been cut to size and the coupler fabricated (see Figure 2).
• Motor mounting system has been designed.
• All components required for building of the altimeter have been procured.
• The streamer ejection system has been designed. Preliminary testing to determine Cd (drag coefficient) of the streamers was conducted.

Feb. 9

• The nosecone was removed from its mould, completed with a layup of 3 plies of weaved fibreglass. It is now ready for trimming and touching-up of blemishes, as well as installation of the stiffening ring, fuselage mating ring, and ejection system connecting rod and arms. The nosecone is shown in Figure 3.
• The coupler for joining the upper and lower fuselage sections has been installed (see Figure 4).
• All components for the Streamer Ejection System have been fabricated. A full ground test of the system will be performed in the near future. A diagram of the system is shown in Figure 5.

Figure 3 -- Fibreglass reinforced polyester nosecone, as removed from forming mould.

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Figure 4 -- Coupler assembly for joining upper and lower fuselage sections.

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Figure 5 -- Diagram of Streamer Ejection System. The streamer is fired out of the side of the rocket fuselage, forced through the frangible cover by the piston (propelled by the pyro charge). The smoke charge is intended to generate a visible cloud of smoke as a visual sighting aid.

Feb. 28

• Both the Streamer Ejection System (SES) and the Parachute Ejection System (PES) have been successfully ground tested. However, the development of both systems was a lot more involved than anticipated, and both systems required repeated testing and subsequent modifications to the designs. The most significant problem encountered with the SES was leakage of the Ejector Tube at the hatch end, which resulted in failure of the piston to force out the streamer due to insufficient pressure buildup from the pyro charge. Despite attempts to remedy this problem, retesting did not result in successful streamer deployment. As a result, the SES was redesigned with a bulkhead at the end of the Ejector Tube (Figure 6), similar in design to the PES Ejection Cylinder . This eliminated the leakage problem, and the fourth test of the SES was fully successful.
  With the initial ground test of the PES, the ejection charge failed to ignite. Examination of the ignition plug combined with in-depth analysis of the functioning of the electrical system concluded that dual nichrome wire filaments, connected in parallel, was not a good design. Testing indicated that such an arrangement required a particularly large current to heat both filaments. This was something of a surprise, as this arrangement was used repeatedly and successfully in the past with the "C" series of flights. The key difference is with the power supplies used.. Previously, 6 AA cells were used, but the new system uses only 4 AA cells, to reduce weight. To remedy the problem, a single nichrome filament was installed and tested, and found to heat very effectively with the new power supply. A second test of the PES was then performed. Although ignition of the charge worked well, the nosecone only partly ejected, and the parachute did not extract from the rocket fuselage. A detailed analysis of the failure was conducted, and six design modifications were implemented to remedy and improve the system. A further two tests of the PES were eventually performed to maximize the effectiveness of the parachute extraction process.

  The experiences with both of the recovery systems underlines the great importance and essential nature of ground testing any "mission critical" systems or components, especially new designs (such as SES) or significant modification to existing designs (PES). Problems that arise during testing can be a result of unanticipated behaviour (such as pressure leakage) or even through oversight, such as the problem with the PES igniter arrangement. Another thing that showed up during testing was the questionable suitability of PVC in a cold environment. After one of the SES tests was performed, it was discovered that a piece of the PVC fuselage adjacent to the cutout frangible cover cutout had broken off in a brittle manner, clearly due to the cold temperature (-10C) at the time of testing. This is an important consideration for high altitude flights, as the air temperature drops with altitude, at an approximate lapse rate of 2 degrees Celsius per 1000 feet. Thus, at a projected altitude of 10 000 feet, the ambient air temperature would be around 0 C (assuming a ground temperature of 20C). This is probably close to the safe limit for the useage of PVC as a structural material, such as a fuselage, bearing in mind that "thermal inertia" would help maintain the temperature of the rocket greater than ambient.

• Aerodynamic drag force testing of the streamers was conducted. The drag loading was lower than hoped for, although a simple modification to the streamer configuration is being investigated in an attempt to increase drag.
• The altimeter, which activates both the SES and PES, is presently being built.

• The altimeter has been built and has undergone successful preliminary testing. The function of the altimeter is to both record the maximum altitude achieved, and to trigger the two-stage recovery system (streamer at peak; parachute at 700 feet above ground). The altimeter is based on Paul Kelly's design, although incorporates certain modifications, such as FET/reed relays to fire the pyro charges. As well, I did not use a printed circuit board, rather, I built the circuit on prototyping Veroboard. The biggest headache encountered was with programming the PIC16F84 microprocessor chip. I built a NOPPP programming circuit, but could not successfully burn in the code. Apparently, there is some incompatibility between the code, programmer, and perhaps with the parallel port of my Pentium PC, as well. Fellow rocketry enthusiast Andrew Fioretti bailed me out by sending me a PIC chip he had successfully programmed. He was also instrumental in helping me in many other facets of the altimeter construction--thanks, Andy! The completed altimeter mounted in the payload cradle is shown in Figure 8.

• The fins have been completed, and are fabricated from 0.063 inch (1.6mm) 6061-T6 aluminum alloy. All fin edges are tapered on one side only to produce a nonsymmetric airfoil, the intention being to produce lift on one surface. This will induce some degree of roll about the rocket longitiudinal axis, to help nullify any possible veering from the intended flight path due to any slight pitching of the rocket.
  For retention, the fins incorporate integral hooks which mate with slots cut into the fuselage. The fins also incorporate root fairings to reduce interference drag and to provide additional out-of-plane stiffness and strength. An unpainted fin is shown in Figure 9.
• The upper and lower fuselage sections have been completed. These have been painted, together with the nosecone and fins. The assembled rocket "shell" is shown in Figure 10.
• The motor mounts have been fabricated and installed in the lower fuselage.