Polecat Aerospace Thumper “Airborne Chris Craft”

Level 3 Construction and Recovery Package

 

 

by

David Randall

NAR #84939 – L2

May 10th, 2008

Introduction

This document comprises the construction package and recovery package for my NAR level 3 certification project.  For my level 3 certification attempt I will be constructing a Polecat Aerospace Thumper rocket from a kit.  This document will outline the materials and techniques I will be using.

This rocket consists of one body section plus an electronics bay.  The four fins are of reasonably standard design, and the nosecone is a mold formed fiberglass 5-1 ogive design.  The coupling and overall construction plan for the main body, electronics bay and nosecone utilizes the manufacturer recommended construction guidelines.

Specifications

            Length:            7’ 6”

            Diameter:        Payload section: 13”

            Weight:           25 lbs. without motor

            Motor:             Aerotech M-1297

            Motor Mount   98 MM (75mm adapter used to size down)

            Altimeters:      GWiz HCX (main)

GWiz HCX (backup)

                Parachute:      Main: Rocketman R19C – estimated descent rate 11 fps @ 50 lbs

                                    Drogue: Spherachute 60” – estimated descent rate 30 fps @ 50 lbs

Construction:  Body Tubes: Cardboard (sonotube)

                                    Fins: 3/8” Birch plywood

                                    Centering rings: 3/8” Birch plywood

                                    Nose cone: Fiberglass

Reinforcement: Airframe – Aerosleeve fiberglass sleeve

Fins – 22” x 3” 2oz fiberglass strips

Airframe couplers – 6oz fiberglass cloth

Nose Cone – Internal centering ring based reinforcement at shoulder

 

See the Thumper dimensions diagram in the Thumper Technical Drawings document for the major dimensions.

Construction Materials

Payload body tube 

The payload body tube will be 10.125” ID cardboard tubing supplied with the kit.  The payload body tube is a total of 13” in length and will be comprised of one piece.  The payload body tube will be secured to the altimeter bay with four #8-32 stainless screws.  The payload body tube will be covered in a single Aerosleeve fiberglass sleeve and epoxied in place.

Main body tube 

The main body tube will be made from 10.125” ID cardboard tubing (sonotube).  The main body tube will be 48” long.  The entire main body tube will be covered in a single Aerosleeve fiberglass sleeve and secured with epoxy.  A layer of decorative “Chromaveil” will be applied to the exterior of the body tube and secured with epoxy.

Fins 

The fins are made from 3/16” birch plywood.  The fins consist of a single piece of plywood each.  The fins will be attached to the body tube using through the wall fin construction and reinforced with an epoxy/chopped fiber fillet on the motor tube to fin attach point, the fin to centering ring attach point, and fillets are used on the fin to body tube outer attach point. Then, 4 oz fiberglass tape will be epoxied to each fillet to motor mount joint for further reinforcement. Dado slots will be made in the centering rings to ensure proper alignment of the fins, and to provide additional epoxy surface area.  Expanding foam will be placed in the fin/body tube cavities to provide additional support and reinforcement.  The fins will be finished with a wood stain and covered with a marine shellac gloss finish.

Centering rings and bulkheads 

All centering rings and bulkheads will be made from 3/8” Baltic birch.  The centering ring and bulkhead schedule is as follows:

• 1 bulkhead plate for the nosecone
• 1 centering ring for the nosecone
• 2 centering rings for the motor mount
• 2 airframe bulkhead plates for the altimeter bay

Rail guides 

The rocket will use (large) Series 1500 5/16” slot rail buttons (www.railbuttons.com) as the launch pad interface. The forward rail button will be secured and epoxied to the forward end of the main airframe at the junction of the forward motor mount centering ring.  The aft rail button will be secured and epoxied to the aft end of the main airframe at the junction of the aft motor mount centering ring.

Reinforcement materials/Adhesives 

As noted in the above tube sections reinforcement will be Aerosleeve fiberglass sleeve.  TAP Plastics 4-1 super hard cure epoxy will be used for securing the fabric as well as all other glued surfaces.  Chopped fiberglass, West Systems 410 Fairing Filler, Cab-O-Sil and milled fiberglass are all used as fillers or additive reinforcement in the project.

Nosecone 

The nosecone material is fiberglass and pre-made from a mold by the manufacturer.  The internal structure will be reinforced with a 3/8” plywood bulkhead epoxied to the interior of the nosecone.  It is installed forward of the shoulder of the nosecone to provide protection against tearout during an abnormally high speed deployment.

Recovery System

Deployment sequence 

This project will utilize dual deployment for the recovery of the rocket.  Two GWiz HCX altimeters will be used to control chute ejection.  Each unit will be configured for dual deployment and the second HCX will act as a redundant system to the first HCX.

• Rocket lifts off and attains apogee

• The first GWiz HCX acting as primary altimeter will sense apogee and ignite the drogue ejection charge. 
• The second GWiz HCX acting as backup altimeter will sense apogee, and after a .75 second pre-configured delay, will ignite its drogue ejection charge.
• The ejection charge will separate the main section and payload section and deploy the drogue chute from the aft payload bay.
• The rocket will quickly descend in a controlled manner to an altitude of 1,500 feet.
• The first GWiz HCX acting as primary altimeter will sense the altitude and ignite the main ejection charge.  The ejection charge will eject the nose cone and the main chute will deploy.
• The second GWiz HCX acting as backup altimeter will sense the altitude and after a .75 second pre-configured delay, ignite the main ejection charge.

Hardware 

3/8” (forward motor mount centering ring) or ¼” (electronics bay and nosecone) U bolts will be used to secure the recovery harnesses to the rocket airframe sections.  These will be mounted to the bulkhead plates on the fore and aft locations of the altimeter bay, the forward bulkhead of the main body section, and the nosecone.  All U-Bolts will use the strap on the underside of the bulkhead or centering ring for maximum tear strength. 5/16” quick links will be used to connect the recovery harnesses and parachutes. 

Parachutes 

The drogue parachute will be a Giant Leap Sphere-a-Chute 60” diameter parachute.  The main chute will be a Rocketman R18C 216” diameter parachute.

Recovery harness 

The recovery harness will consist of 3/8” tubular nylon and ½” tubular nylon.  There will be six pieces totaling 110’ in length.  The ½” nylon harness will measure 10’ and the 3/8” tubular nylon pieces will measure 50’.  The harnesses will attach to the u-bolts and quick links using knots.  The tested peak load of 3/8” tubular nylon is approximately 650 lbs (http://www.rocketmaterials.org/datastore/cord/).

Parachute Bays 

The rocket will have two parachute bays, one each for the main and drogue parachutes. The main parachute bay is formed by the nosecone and electronics bay coupling. The drogue parachute bay is formed by the main body tube.  The joint between the main body tube and the electronics bay will be held together using four shear pins.  The joint between the electronics bay and the nosecone will be held together using four shear pins. The shear pins will be #2 nylon screws.  Ground testing verified the shear pins functioned properly.

The tubular nylon recovery harnesses and parachutes will be protected from ejection charge gasses using an ironing board cover formed into a deployment bag. 

Descent Rates 

The descent rates for the parachutes are based on Rocketman Enterprises Inc and Giant Leap manufacturer’s published descent rates;

• Giant Leap 60” Spherachute drogue: 30-40 fps
• Rocketman R18C main chute: 10-12 fps

Using the descent calculator found at http://www.aeroconsystems.com/tips/descent_rate.htm a descent rate of 11 ft/sec using a weight of 960oz, 216 inches for the diameter of main chute, and 60 inches for the diameter of the drogue as the inputs.

 

Altimeters 

This rocket will use two GWiz HCX altimeters.  One unit will be used to ignite the primary main and drogue chute charges and the second unit will be used to ignite the backup charges.  Each unit uses barometric pressure sampling and accelerometers to sense key events during flight.  The units will be powered by a standard 9 volt dry cell as per the manufacturer’s recommendation.  A brand new battery will be installed in each unit before flight.  The manufacturer’s software will be loaded and connected to each altimeter prior to flight, and the pyro and CPU battery voltages will be read to ensure sufficient power is present with the installed batteries.

Electronics Mounting

A plywood board will be used to mount all electronics and switches.  The plywood board will be inserted into a set of wooden guide rails epoxied to the inside walls of the electronics bay.  Slots in the forward and aft electronics bay bulk plates will receive the plywood to secure the plywood from movement. 

One DPDT switch mounted in the altimeter bay electronics sled will be used to safe the primary and backup main chute ejection charges.  One DPDT switch mounted in the altimeter bay electronics sled will be used to safe the primary and backup drogue chute ejection charges.  One DPDT switch mounted on the electronics board will be used to control pyro power and CPU power to the main GWiz HCX flight computer.  One DPDT switch mounted on the electronics board will be used to control pyro power and CPU power to the backup GWiz HCX flight computer.  The flight computers will be mounted with screws to the plywood inside the altimeter bay. 

The batteries will be mounted in plastic 9V battery cases.  An aluminum strip is mounted to the threaded rods by nuts and washers and pressed against the main battery casing to prevent any side to side movement.  The batteries will rest against a hard rubber stopper mounted on the aft electronics bay bulk plate to prevent any vertical motion.  

Electronics Wiring

The main GWiz HCX altimeter is powered in a dual battery configuration.  The positive lead from each 9V battery runs through a DPDT switch.  The negative lead from each 9V battery runs directly to the altimeter.  There are three pyro outputs wired to the altimeter.  The first pyro output is for apogee deployment, and one lead of the e-match is wired through a DPDT switch for mechanically disabling current to the e-match.  The second pyro output is for low altitude main chute deployment, and one lead of the e-match is wired through a separate DPDT switch for mechanically disabling current to the e-match.   The third pyro port is used for a smoke canister ignited by electric match.  It will ignite at 2 seconds after motor burnout for tracking purposes.

The backup GWiz HCX altimeter is powered in a dual battery configuration.  The positive lead from each 9V battery runs through a DPDT switch.  The negative lead from each 9V battery runs directly to the altimeter.  There are two pyro outputs wired to the altimeter.  The first pyro output is for apogee deployment, and one lead of the e-match is wired through a DPDT switch for mechanically disabling current to the e-match.  The second pyro output is for low altitude main chute deployment, and one lead of the e-match is wired through a separate DPDT switch for mechanically disabling current to the e-match. 

Wiring Diagram

 

Figure 1 – Wiring Diagram – Altimeters

 

Pyrotechnics

The purpose of the ejection charges is to separate the payload bays from the main and nose cone and deploy the parachutes.  The amount of black powder needs to be enough to break the shear pins, separate the airframe sections, and eject the parachutes enough so they inflate and slow the rocket for a safe recovery.

The rule of thumb for sizing ejection charges is to generate 15 psi of force acting against the bulk plates to separate the components of the rocket.  However, for larger rockets this amount of pressure will be too much since the area this pressure acts on increases with the diameter.  The target force required to separate components of the rocket is 350 pounds of force.  Assuming 15psi were generated by a charge.  Because the 10” airframe sections have 78 square inches of area at the ends, the total applied force would be 1,170 pounds of force (78 in² * 15psi).  This is too much, and may result in high speed separation or failure of the airframe, rather than proper separation.  In solving for the amount of black powder to use, a target of 350 pounds of force will be used rather than pressure.

 

There will be four ejection charges used in this rocket; one primary charge each for main and drogue chute ejection and one back up charge each.  The size of the primary ejection charges is calculated using the below equation to solve for the amount of force needed.

                       

m=F*(L)/R/T/12 * 464

           

• m = mass of BP needed in grams
• F = specified force in lbf
• L = length of pressurized compartment in inches
• R = Gas constant = 22.16 ft*lbf/lbm
• T = combustion temperature constant = 3307

Using this equation the ejection charge sizes are:

• Drogue chute:  F = 350, L = 20
  • m =  (350*20)/22.16/3307/12 * 464 = 3.7 grams
  • Main Chute: F = 350, L = 7
    • m =  350*(7)/22.16/3307/12 * 464 = 1.3 grams

 

Using a simplified equation found at http://www.vernk.com/EjectionChargeSizing.htm verifies this amount.

 

N = 0.00052*FL

 

• N = grams of black powder
• F = Specified force in pounds
• L = Length of pressurized compartment

 

• Drogue chute:  F = 350, L = 20
  • N =  .00052 * 350 * 20 = 3.64 grams
  • Main Chute: F = 350, L = 7
    • N =  .00052 * 350 * 7 = 1.27 grams

Each of the ejection charges will be ignited using e-matches.  The backup ejection charges will be increased by 50% to add an additional margin of safety.

Stability Evaluation

Ground Support Equipment

The estimated minimum velocity for stable flight is 44 ft/sec and using Rocksim 8.0 the rocket will achieve this velocity at 45” or just under four feet.  Since eight feet is the minimum distance for minimum stable velocity, a standard eight foot launch rail will be used.  The estimated velocity at the end of an eight foot rail will be 75 ft/sec.  These calculations are based on an Aerotech M1297 motor.

Center of Pressure/Center of Gravity

The calculated center of pressure using Rocksim v8.0 is 64.3”.  The measured center of gravity is 43 inches without the motor which results in a static margin of 2.1 calibers.  Loaded with an AT M1297 the static margin drops to 1.37 calibers which still provides for a stable flight.

Flight Profile

Launch Weight:                                      47 lbs.

Motor:                                                   Aerotech M1297W

Calculated Launch velocity:                     63 ft/sec

Maximum Calculated Velocity:                 657 ft/sec

Maximum Calculated Altitude:                  5497 ft

Maximum Calculated Acceleration:           1022 ft/sec/sec

Rocksim v8.0 was used to calculate the flight parameters.

 

Construction Techniques

Motor Mount/Fin Assembly

The motor mount/fin assembly will be built and then slid into the main body tube as a single unit.  This method of construction will allow easy access to apply epoxy fillets and internal reinforcement to all fin/motor mount joints.  Fin mounting will be through the wall construction.

Materials

1 – 48” 98mm motor mount

2 – 3/8” x 10.125” O.D. x 4” I.D plywood centering rings

1 – Aero Pack 98mm motor retainer

4 – 22” x 11” main fins

Chopped Fiberglass Fibers

4 oz Fiberglass cloth tape

TAP 4-1 Super Hard Epoxy

Fin Can Sub-assembly

1)    For the fins and centering rings I used the parts included with the kit, but performed a minor modification.  Each centering ring was slotted for the fins to provide additional rigidity and ensure a true 90° alignment. – See Error! Reference source not found. and Figure 2 – Fins in Dado Slots for alignment. I prepared epoxy with chopped fiberglass and applied it to the tab and slots of the pieces for each of the four fins.  I applied the epoxy with chopped fiberglass as fillets to all the joints. The assembly was set aside to cure at room temperature.  I applied 4 oz fiberglass “tape” to the fillets to provide additional joint strength.  See Figure 3 – Fiberglass tape applied to fin mount points. The assembly was set aside to cure at room temperature. 

 

 

Figure 2 – Fins in Dado Slots for alignment

 

 

Figure 3 – Fiberglass tape applied to fin mount points

Motor Retention

1)    At the end of the motor mount tube I secured the 98mm Aero Pack motor retainer using the supplied screws and manufacturer instructions. 

 

Body tube

Materials

1 – 48” x 10” airframe

Aerosleeve 6 oz fiberglass sleeving

Chromaveil decorative fabric

West Systems 410 fairing filler

1 – Motor Mount assembly

TAP Plastics 4-1 super hard epoxy

Airframe

1)    The main airframe is composed of one piece of 10” ID airframe tube.  The length is 48 inches.  The entire length of the main was reinforced with a single length of Aerosleeve 6 oz fiberglass. See Figure 4 – Applied epoxy and fiberglass sleeve.  The tube was wrapped with a 1 mil acetate film and wrapped with stretchable plastic wrap.  This was set to cure for two days.  The 1 mil acetate was removed and a mixture of West Systems 410 fairing filler and TAP Plastics 4-1 super hard epoxy was applied with a spreader directly to the tube to fill in any pinholes or ridges left from the stretchable plastic wrap.  This was set to cure for 2 days.  Next, a layer of Chromaveil (decorative cloth finish) was applied and a second coat of epoxy applied to the Chromaveil.  The tube was wrapped with a 5 mil acetate film, excess epoxy was squeezed out, and the tube was set to cure.  The 5 mil acetate film was removed after the epoxy had fully cured.

 

 

Figure 4 – Applied epoxy and fiberglass sleeve

 

Fin Slots

1)    Once the main airframe lay-up had fully cured, four 3/16” slots were cut from the aft end for the fins.  A router jig was used to ensure the slots were true and the tube remained stable through the slotting process.  See Figure 5 – Router jig for fin slots .

 

 

Figure 5 – Router jig for fin slots

 

 

Figure 6 – View of 4 fin slots

Final Assembly

1)    After the epoxy had cured the fin can sub-assembly was inserted into the body tube.

2)    Epoxy fillets with milled fiberglass, fairing filler and Cab-O-Sil were formed on each of the four fin to body tube joints.

3)    TAP Plastics Two-Part Expanding foam was poured into fin cavities through holes drilled in the aft centering ring to provide additional rigidity.

Electronics Bay

The electronics bay will hold the two altimeters needed for the certification flight.  For a complete wiring diagram please see Figure 1 – Wiring Diagram – Altimeters

Materials

1 – 13” x 10.125” airframe coupler

1 – 9” x 10.125” airframe

2 – 10” coupler bulk plates

4 – 3/8” x 15” threaded rod

16 – 3/8” hex nuts

16 – 3/8” washers

4 – 3/8” U-bolts

4 – DPDT switches

1 – Aluminum retention strip

2 – Four node terminal blocks

4 – Schedule 40 end cap

4 – #6-32 x 1” bolts

4 – #6-32 nuts

1 – 8” x 6” x ¼” plywood electronics board

1-6” x 7.5” fiberglass Aerosleeve

6oz fiberglass

West Systems Epoxy

24 gauge solid copper wire

Bulk plate assembly (see Figure 7 – Electronics Bay Bulk Plate)

1)    Four holes were drilled for the U-bolts and one hole was drilled for the pass-through of wiring to the terminal block.

2)    The terminal block mounting holes were drilled and the terminal blocks mounted.

3)    The electronics wiring was passed through the wiring hole and epoxy was applied to block air passage around the wiring.

4)    The U-bolts were installed into each of the bulk plates with the hex nuts and secured with loctite to prevent them from coming undone.

5)    Each of the airframe bulk plates were coated with epoxy to protect from ejection gasses.

6)    The 3/8” threaded rod was then placed through the holes in one of the bulk plate assemblies and secured with 3/8” nuts and loctite.

7)    Two ejection cups were epoxied in place on each of the bulk plates.  These will hold the ejection charge during flight.

 

 

Figure 7 – Electronics Bay Bulk Plate

 

Coupler Tube

1)    The coupler tube ends were first reinforced with CA glue to prevent fraying and allow sanding of the coupler ends for proper fit-up.

2)    Four ¼” x ¼” x 7” wood strips were epoxied to the inside of the coupler tube.  These are used to hold the altimeter sled in place.

3)    After the epoxy had dried four ¼” holes were cut through the airframe and coupler for the DPDT switches.  These switches will be used to safe the primary and backup ejection charges. 

4)    The airframe was also drilled with two ¼” diameter holes that are used to transfer the LED light from the altimeters to the exterior of the rocket via a Plexiglas rod.

 

Figure 8 – Slotting and Rails for Sled

 

 

Figure 9- Mounting Slots and Rail Guides

 

 

 

Figure 10 – Mounting of Aluminum Stop Strip

 

 

Figure 11 – Hard Rubber Vertical Motion Stop

 

 

Electronics bay wiring

1)    Two sets of wires are used for the main ejection charges.  One pair of wires (orange & brown) is used for the primary main chute ejection charge, the other (red and black) are used for the backup main chute ejection charge.

2)    Two sets of wires are used for the drogue ejection charges.  One pair of wires (orange & brown) is used for the primary drogue chute ejection charge, the other (red and black) are used for the backup drogue chute ejection charge.

3)    The wiring for the main chute ejection charge terminates with connections to a four connector terminal block on the forward end of the forward bulk plate. 

4)    The wiring for the drogue chute ejection charge terminates with connections to a four connector terminal block on the aft end of the aft bulk plate. 

 

 

 

Figure 12 – Mounted terminal block

Figure 13 – Terminal Block Wiring

Electronics board wiring

1)    An outline was first drawn on the electronics board to show the mounting location for the altimeters, batteries, and the DPDT switches.

2)    Each of the components was then mounted to the electronics board.  The altimeters and DPDT switches were mounted to one side of the electronics board.  The batteries were mounted to the opposite side of the electronics board.

 

3)        Figure 14 – GWiz Altimeters (HCX1 – Left, HCX2 – Right)

4)    One wire was run from the main chute terminal on the HCX altimeter to one of the terminal block nodes.  Another wire was run from the main chute terminal on the HCX altimeter to one of the DPDT switches.  Another wire was run from the DPDT switch to one of the terminal block nodes.  Wires were run from the drogue terminals on the HCX in the same manner.

5)    The positive wire from one battery (Pyro1) was connected to one of the DPDT switches.  A wire was run from the DPDT switch to the pyro battery positive terminal on the HCX.  The negative wire from the same battery was connected to the pyro battery negative terminal on the HCX.

6)    The same wiring method was used for the backup HCX altimeter.

 

 

Figure 15 – Altimeter side wiring

 

 

Figure 16 – Battery Side Wiring

Final Assembly

1)    The bulk plate assembly with the threaded rod was inserted into one end of the electronics bay.  The electronics board was then8 slid part way onto the threaded rod.  Each set of wires was then connected to the outward facing nodes of the terminal blocks so that the red and black wires connected to the switches lined up with the red and black wires leading to the altimeters.

2)    The electronics board was then slid all the way into the altimeter bay.  The bulk plate with the threaded rod was then rotated until the DPDT switches on the altimeter board were aligned with two of the vent holes.  These vent holes will also act as the access ports for the DPDT switches.

3)    The remaining bulk plate was slid over the all thread and secured with wing nuts to ensure the proper fit of all the components.

Securing payload and electronics bays

1)    Once the tubes had cured and the tape removed the tubes were placed partway onto the electronics bay and marks were made on the tubes to indicate where the screw holes needed to be.  Then each of the airframes was drilled with six holes each for the screws to secure the airframe sections to the electronics bay.

Testing

1)    The electronics were then turned on through the access ports to ensure the DPDT switches were correctly wired.  The manufacturer’s software was used in conjunction with 12V lamps to verify the proper operation of a sample flight as well as direct manipulation of the pyro outputs.

2)    Each altimeter goes through a diagnostic to determine continuity of the ejection charge channels and then beeps out that continuity.  The altimeters were tested with channels bridged, drogue only, and main only to verify the wiring.  This testing should not be confused with the actual ejection charge testing required for level 3 certification.

Payload Bays

The payload bay comprises the section above the electronics bay used to retain the main chute.

Materials

1)    1 – 13” x 10.125” airframe

2)    1 – 13” Aeroesleeve fiberglass sleeve

3)    4 – ¼” tapered machine screws

4)    TAP 4-1 Super Hard Epoxy

 

Reinforcement

1)    One length of Aerosleeve was cut and placed the airframe section.  Epoxy was then applied to thoroughly wet the fiberglass.  A layer of 5 mil acetate plastic was wrapped around the tube.  The excess epoxy was squeezed out by hand and then the airframe was taped to secure the acetate.  The tube was set aside to cure.  After curing, the acetate was removed.

Shear pins

1)    The nose cone was inserted into the main chute payload bay.  Four equally spaced 5/65” holes were then drilled for insertion of the shear pins.

2)    Four pieces of 1” x ½” x .025” brass were drilled with a 5/64” hole.

3)    The brass pieces were epoxied in place over the holes in the nose cone shoulder and serve as a shearing point for the pins. 

4)    The drogue payload bay and the main were fitted for shear pins in the same manner

5)    #2-56 – 3/4” nylon screws will act as the shear pins.

 

Nose Cone

Materials

1 – 10” x 3/8” plywood bulk plate

1 – 7.5” x 3/8” plywood bulk plate

1 – 3/8” U-bolt

4 – ¼-20 T-Nuts

4 – ¼-20 bolts

1 – 3/8” all-thread – 24” length

TAP 4-1 Super Hard epoxy

Fabrication

1)    The nosecone is supplied with the kit.

2)    The finished cone was lightly sanded to even out any high spots.

3)    The bulk plate was pre-drilled with two holes for the U-Bolt.  The U-bolt was secured using the hex nuts and loctite.

4)    The bulk plate was then secured to the aft end of the nosecone with the U-bolt facing out.  This is the connection point for the main chute recovery harness.

5)    Approximately 50cc’s of epoxy was poured into the nosecone.  A length of 3/8” all-thread was inserted into the epoxy and left to cure.  The all-thread is used to secure weights in the nosecone to adjust the CG as required for various sized motors.

Nose Cone Shoulder

1)    The nose cone shoulder had a layer of epoxy with West Systems 410 Fairing Filler applied to approximately a 1/16” depth. This allowed a tighter fit with the payload bay tubing.

2)    One centering ring was installed behind the shoulder and epoxied in place.

3)    Four holes were drilled in the centering ring and 4 blind nuts inserted in the forward end of the holes.

4)    Four holes were drilled in a bulk plate to match the centering ring.  Four ¼” bolts secure the bulk plate to the centering ring. 

5)    Two holes were drilled in the centering ring for the U-bolt.

6)    The U-bolt was installed into the bulk plates with the hex nuts and secured with loctite to prevent them from coming undone.

 

1)   Appendix A – Diagrams

Rocksim CG/CP locations

 

2)  Rocket under Drogue Chute

 

 

3)  Rocket under Main Chute

 

 

4)  Completed Rocket Photograph

 

5)  Appendix B – Flight Simulation

The information in this section shows flight simulation data taken from RockSim v8.0.  The simulation properties were set to reflect an Aerotech M1297W motor used for propulsion and the elevation and location figures matching those of Mansfield, Wa.

 

L3 Thumper – Simulation results

Engine selection

[M1297W-None]

 

Simulation control parameters

Flight resolution: 800.000000 samples/second

Descent resolution: 1.000000 samples/second

Method: Explicit Euler

End the simulation when the rocket reaches the ground.

Launch conditions

Altitude: 2262.00000 Ft.

Relative humidity: 40.000 %

Temperature: 70.000 Deg. F

Pressure: 29.9139 In.

Wind speed model: Slightly breezy (8-14 MPH)

Low wind speed: 8.0000 MPH

High wind speed: 14.9000 MPH

Wind turbulence: Fairly constant speed (0.01)

Frequency: 0.010000 rad/second

Wind starts at altitude: 100.00000 Ft.

Launch guide angle: 0.000 Degrees from vertical

Latitude: 47.800 Degrees

Launch guide data:

Launch guide length: 96.0000 In.

Velocity at launch guide departure: 63.8120 ft/s

The launch guide was cleared at : 0.263 Seconds

User specified minimum velocity for stable flight: 43.9993 ft/s

Minimum velocity for stable flight reached at: 45.5677 In.

Max data values:

Maximum acceleration:Vertical (y): 1022.969 Ft./s/sHorizontal (x): 4.145 Ft./s/sMagnitude: 1022.969 Ft./s/s

Maximum velocity:Vertical (y): 657.0833 ft/s, Horizontal (x): 21.8533 ft/s, Magnitude: 658.8812 ft/s

Maximum range from launch site: 4075.29528 Ft.

Maximum altitude: 5467.94620 Ft. 1638.07055 Ft.

Maximum altitude: 6814.06093 Ft.

Recovery system data

P: Drogue Parachute Deployed at : 18.211 Seconds

Velocity at deployment: 30.3129 ft/s

Altitude at deployment: 5467.94620 Ft.

Range at deployment: -470.98753 Ft.

P: Main (low altitude) Parachute Deployed at : 102.734 Seconds

Velocity at deployment: 56.2477 ft/s

Altitude at deployment: 999.98688 Ft.

Range at deployment: 1273.22179 Ft.

Time data

Time to burnout: 4.170 Sec.

Time to apogee: 18.211 Sec.

Optimal ejection delay: 14.041 Sec.

Time to wind shear: 0.912 Sec.

Landing data

Successful landing

Time to landing: 243.421 Sec.

Range at landing: 4075.29528

Velocity at landing: Vertical: -12.5951 ft/s , Horizontal: 0.0000 ft/s , Magnitude: 12.5951 ft/s

 

 

6)   Appendix C – Checklists

Pre-Launch Checklist

This is the pre-launch checklist as required as part of the Level 3 procedures. This checklist is to be used on launch day while preparing the rocket for my L3 certification flight.

1)    Paperwork Preparation (This is needed only for L3 certification attempt)

a)    Confirm L3 Certification Application Form has been filled out

b)    Confirm Construction Package Affidavit has been filled out and signed by a member of the L3CC

c)     Confirm Recovery Package Affidavit has been filled out and signed by a member of the L3CC

d)    Confirm Pre-Flight checklist has been filled out and signed by certification team

e)    Confirm one member of the certification team is a L3CC member

Recovery System Preparation

1)    Electronics

a)  Prepare GWiz HCX1 altimeter

i)      While flight computer is out of the rocket, connect to PC to verify configuration:

(1)   Main at 1500’

(2)   Drogue at apogee

(3)   Pyro port 4 at burnout + 2 seconds (for effect smoke canister)

ii)     Be sure all arming switches are off.

iii)    Install two NEW batteries.

iv)   Secure batteries in place with positive battery retention system.

v)    Check dip switches are set for high current per manufacturers instructions

(1)   HC Switch 1 = on

vi)   Ready avionics bay for altimeter.

vii)  Install altimeter in rocket.

viii) Insure all pyrotechnics are in disarmed mode during electronics final installation.

b)  Prepare GWiz HCX2 altimeter

i)      Be sure all arming switches are off.

ii)     Install two NEW batteries.

iii)    Secure batteries in place with positive battery retention system.

iv)   Check dip switches are set for high current per manufacturers instructions

(1)   HC Switch 1 = on

v)    Ready avionics bay for altimeter.

vi)   Install altimeter in rocket.

vii)  Insure all pyrotechnics are in disarmed mode during electronics final installation.

 

2)    Pyrotechnics

Note: All pyrotechnic devices must remain in an unarmed mode until rocket is on pad ready to launch.

a)  Pyrotechnics, drogue

i)      Prepare drogue deployment pyrotechnic charges and ready for installation into rocket.

(1)   3.6 grams OR

(2)   55 grains

ii)     Connect drogue charge leads to wiring terminals on electronics bay

b)  Pyrotechnics, main

i)      Prepare main deployment pyrotechnic charges and ready for installation into rocket.

(1)   1.5 grams OR

(2)   23 grains

ii)     Connect main charge leads to wiring terminals on electronics bay.

 

3)    Drogue Chute Preparation

a)  Inspect components.

i)      Check shock cords for cuts, burns, and tangles.

ii)     Check all shroud lines — no tangles.

iii)    Check drogue chute for tears and burns.

iv)   Check deployment bag for tears.

b)  Pack drogue chute

i)      Fold drogue chute per manufacturer’s instructions.

ii)     Insure shroud lines are free from tangles.

iii)    Insure all quick links are secure.

iv)   Wrap drogue chute in chute deployment bag.

v)    Insert drogue bag/chute into main compartment

c)   Check all connections.

i)      Electronics bay harness to quick link

ii)     Drogue harness to quick link

iii)    Drogue chute to quick link

iv)   Drogue chute protection to quick link

d)  Secure drogue payload bay

i)      Fit electronics bay on main body tube and line up holes.

ii)     Insert shear pins in holes.

4)    Main Chute Preparation

a)  Inspect components

i)      Check harness for cuts, burns, and tangles.

ii)     Check all shroud lines — no tangles.

iii)    Check main chute for tears and burns.

iv)   Check deployment bag for tears.

b)  Check all connections

i)      Nose Cone harness to quick link.

ii)     Avionics bay harness to quick link.

iii)    Main chute to quick link.

iv)   Main chute protection to quick link.

c)   Pack main chute

i)      Fold main chute per manufacturer’s instructions.

ii)     Insure shroud lines are free from tangles.

iii)    Insure all quick links are secure.

iv)   Wrap main chute in deployment bag.

v)    Insert main bag/chute into payload compartment.

d)  Connect nose cone to main chute payload bay

i)      Insert the nose cone into the main chute payload bay and align holes.

ii)     Insert shear pins into holes and confirm a secure fit.

5)    Motor Installation

a)    Assemble motor per manufacturer instructions.

b)    Install motor in motor mount and verify snug fit of motor casing in motor mount tube. Tape motor casing for snug fit if needed.

c)     Install Aeropack threaded retaining ring into motor retainer body.

d)    Tape igniter to airframe away from motor nozzle.  DO NOT install igniter until rocket is secure on the pad.

Final Launch Preparations

1)    Load Rocket on Pad

a)    Prepare launch pad.

b)    Load rocket on launch rod.

c)     Check tower’s position and be sure it is locked into place and ready for launch.

2)    Arm HCX main altimeter

a)    Turn on power to HCX.

b)    Arm drogue and main ejection charges.

c)     Confirm proper settings via audible beeps and visual LED blinking.

d)    Confirm continuity for both channels via audible beeps.

3)    Arm HCX backup altimeter

a)    Turn on power.

b)    Arm drogue and main ejection charges.

c)     Confirm proper settings via audible beeps and visual LED blinking.

d)    Confirm continuity for both channels via audible beeps.

4)    Prepare Igniter

a)    Assure that launcher is not hot. Disconnect battery from relay box. Assure that key IS NOT in the remote device and that arming switch is off.

b)    Be sure all connectors are clean.

c)     Strike the igniter leads together to check for a spark

d)    Hook up the igniter outside the motor and check continuity

e)    Disconnect the igniter leads

f)     Arm electronics

g)    Insert igniter. Be sure it is completely forward and touching fuel grain.

h)    Attach leads/clips

i)      Back everyone away and perform final continuity check.

j)     Hook up igniter to leads OUTSIDE OF ROCKET.

k)    Be sure leads don’t touch each other or that circuit is not grounded by contact with metal parts.

l)      Secure igniter in position.

m)   Connect battery to relay box (if applicable).

5)    Final Launch Sequence

a)    Insure Flight Witnesses are in place and ready for launch.

b)    Ensure one flight witness is a member of L3C committee.

c)     Signal LCO & RSO that rocket is ready for launch.

6)    Misfire Procedures

a)    Safe all pyrotechnic to pre-launch mode.

b)    Remove failed igniter.

c)     Resume checklist at step 2

 Post-Recovery Checklist

This is the post-flight checklist as required as part of the Certification Package. This checklist includes steps required to ensure the rocket is in a safe condition after completion of a flight.

1)    Post Flight Recovery – Successful Flight

a)    Safe all ejection circuits.

b)    Check for non-discharged pyrotechnics.

c)     Remove any non-discharged pyrotechnics.

d)    Have certification team fill out post flight checklist.

e)    Have certification team fill out L3 Certification affidavit.

f)     Rejoice.

g)    Go buy more M motors and fly again.

2)    Post Flight Recovery – Failed Flight

a)    Follow Normal Post Flight Recovery procedures 1 – 3.

b)    Have certification team member fill out L3 Certification Failure Form.

4)   Appendix D – Recovery Electronics Flight Tests

Both the HCX units have been flown and successfully deployed their recovery devices prior to the certification flight.  Each unit has been flown at least two times without incident.

Power supply: 9volt battery

Arming device: battery connector

Altimeter	Most Recent Flight	Rocket	Altitude	Motor	Drogue Deploy Setting	Main Deploy Setting
HCX1 (main)	4/2/2008	Estes Patriot	721 ft	Estes E9-8	Apogee	500ft
HCX2 (backup)	4/2/2008	Estes Patriot	420 ft	Estes E9-8	Apogee	–