 The basic layout of the rocket follows a fairly typical configuration for a single stage high power rocket with dual parachute deployment. The main airframe tube comprises the largest single item in the weight budget. Consisting of 11.4" phenolic tubing laminated with a single layer of 6 oz. fiberglass, it is expected to weigh in at 340 oz. The nose cone is a fiberglass part fabricated by Performance Rocketry, and weighs in at 100 oz. To save weight, the three scale fins are fabricated from 1/2" thick Giant Leap honeycomb composite board, and built up to scale thickness with foam and covered with glass. The weight of the three-fin set is projected to be 55 oz.
Further details of the layout and construction are provided by the accompanying diagrams. On the layout diagrams, the following specific items are called out:
- Fiberglass nose cone
- Payload airframe; 11.4" phenolic w/6 oz. fiberglass
- Storage compartment for drogue and shock cords
- 3" phenolic tube/coupler ejection stuffer tube
- 11.4" phenolic coupler
- 4" phenolic external conduit for scale appearance and housing for electronics bays
- Storage compartment for main parachute and shroud lines
- Main airframe; 11.4" phenolic w/6 oz. fiberglass
- 11.4" phenolic coupler
- 4" motor mount tube
- 54 mm motor mount tube (3)
- Honeycomb composite fins
Actual weights of various components are (before painting):
- Nose cone: 93 oz.
- Payload section: 198 oz.
- Midframe assembly: 227 oz.
- Fin can/propulsion assembly: 407 oz.
- Drogue and main parachutes: 64 oz.
- Total: 989 oz. = 61.8 pounds
The principal structural centering rings are made of 1/2" birch plywood and will be located in the fin can region and in the recovery compartment/separation region. In addition to these main rings, a number of secondary lightweight rings and gussets are provided for internal support of the motor tube and ejection piston against lateral forces.
The rocket will be recovered in two pieces. The nose cone/payload section will descend separately on its own Rocketman RC-12 parachute. The remaining airframe and propulsion section are recovered by dual deployment; a Rocketman R9 Pro-Ex ballistic drogue chute for initial deceleration, followed by a Rocket Rage RRQS100 Quantum chute for terminal descent. 1/2 inch tubular nylon shock cords with custom sewn loops are used for recovery harnesses. . Triggering of a pyro release mechanism will cause the drogue chute to pull out the main from its compartment in the upper part of the booster. Conventional stainless steel U-bolts and hardware are used for attachment to the bulkheads.
Flight avionics consists of the following, providing redundant function for all flight critical events:
- Altimeter #1: Perfectflite MiniAlt recording altimeter; provides apogee detection for separation charge firing; second channel provides backup for main chute pyro release. Also provides onboard recording of flight altitude history for post-flight computer readout.
- Altimeter #2: PML/Missileworks Co-Pilot altimeter; provides redundant apogee detection for separation charge; second channel provides drogue ejection firing approx. 1 second after separation charge firing.
- Timer: Missileworks PET timer; triggered by pull-pin on payload separation event; first channel provides redundant drogue ejection firing; second channel provides primary main chute pyro release at pre-programmed time after separation (TBD).
The lower end of the electronics conduit contains arming switches and safeing shunts which are to be accessible while the rocket stands at the pad. Shorting plug shunts are provided for safety across all circuits that activate black powder charges. Shunts are to be removed at the pad when the area is clear and the rocket is ready for arming.
Using the layout and fin dimensions detailed, the Barrowman center of pressure was calculated. The calculated CP is found to be 156 inches from the forward tip of the rocket, which is approximately 10 inches forward of the top edge of the fin roots. Once the internal construction was finalized, the center of gravity was accurately calculated, and adjusted as necessary with the addition of nose weight for 1.5 to 2 calibers of stability margin
Peak altitude anticipated with a full M hybrid motor is between 4000 and 5000 feet. At apogee, a black powder charge inside the 3" booster/payload ejection piston forces these sections apart. The drogue chute is attached to the booster section, but housed within the payload tube. When the sections are forced apart, the drogue is pulled free and inflates while the payload section falls away attached to the booster by its own shock cord.
At a lower altitude (to be determined) a Tether (Defy Gravity) pyro release mechanism will be used to sever the connection between the drogue and its hard attachment point, allowing it to pull the main chute from its compartment in the upper booster.
|