John Rudolf Lewis
JohnRLewis@gmail.com
TRA# 15019

This is my documentation package for a Tripoli level-3 certification attempt. This project is based on the 4″ Fiberglass Frenzy XL kit from MadCow Rocketry.

Specifications

Length:  92″
Diameter:  4″
Weight:  14 lbs without motor (24 lbs with first launch motor)
CP:  77″ from nose tip
CG:  65″ from nose tip
Motor:  75mm Aerotech M1297W
Parachutes: Main: Fruity Chutes Iris Ultra 84″ compact
Pilot:  Fruity Chutes Eliptical 18″
Drogue: 24″
Electronics: Primary: Altus Metrum Telemetrum
Backup: Altus Metrum Easy Mini

 

Detailed Information

Parts Included in Kit

  • (1) Filament Wound Nose Cone w/ Metal Tip
  • (1) Nose Cone Coupler (8”)
  • (1) Pre-slotted main body tube (46”)
  • (1) Payload section body tube (22”)
  • (1) Switch Band (2”)
  • (3) Centering rings
  • (1) Coupler (12”)
  • (5) Bulkheads
  • (1) 75mm Motor tube
  • (6) 3/16” G10 fins
  • (3) Forged Eyebolts
  • (9) Nuts and
  • (9) Washers
  • (1) Nylon shock cord
  • (2) Rail buttons,
  • (2) screws
  • (2) Threaded Rods

Parts Provided by Builder

  • (1) AeroPack 75mm Quick-Change Retainer for Fiberglass Tube
  • (1) Fruity Chutes Iris Ultra 84″ compact main chute
  • (1) Fruity Chutes Eliptical 18″ pilot chute
  • (1) Fruity Chutes 4″ x 9″ deployment bag
  • (1) Unknown Brand Nylon 18″ drogue chute
  • (1) 1.375″ ID Stainless Steel Slider Ring
  • (6) 1/4″ Stainless Steel Quick Links
  • (1) Altus Metrum Telemetrum
  • (1) Altus Metrum Easy Mini
  • (2) 850 mAh Polymer Lithium Ion Batteries
  • (8) 4-40 x 3/16″ nylon 6/6 screws
  • (8) 4-40 nylon 6/6 nuts
  • (8) 4-40 x 3/8″ nylon 6/6 standoffs
  • (1) Mobius Mini Action Camera
  • (1) 1000 mAh Lipo battery for camera
  • (1) model airplane plywood avionics sled
  • (1) model airplane plywood camera bulkhead
  • (3) Phillips Machine Screw, 8-32 Thread, 5/16″ Length (for avbay to payload bay attachment)
  • (3) Tab Base Weld Nuts, with Low-Profile Barrel and Weld Nibs, 8-32 Thread Size (for avbay to payload bay attachment)

Ground Support Equipment

This rocket will require one of the standard launch towers with 1010 rail along with one of the remote launch controllers that are typically provided at F.I.T.S. launches. It will need to be launched from the away cell.

Recovery System

This project will utilize dual deployment for the recovery of the rocket.

Parachutes

Electronics

  • Altus Metrum Telemetrum
  • Altus Metrum Easy Mini

Pyrotechnics

The pyrotechnic ejection charges need to separate the avionics bay from the fin can, and the nose cone from the payload bay. The amount of black powder needs to be enough to break the shear pins, separate the airframe sections, and expose the parachutes.

Calculations

The shear pins are #2-56 nylon screws. Online sources list their shear strength between 31 and 46 pounds. Taking the average and rounding up to 40 pounds each, the three screws per joint would require approximately 120 pounds of force. Increasing that value to account for enough force to push the sections apart, eject parachutes, plus a safety margin, 200 pounds is a good nominal value to calculate for.

Cross Sectional Area = Pi * R ^ 2 = 3.14 * 2 ^ 2 = 12.56 in^2

PSI = 200 lbs / 12.56 in^2 = 15.96 lbs/in^2

Volume of Drogue Bay without motor = Pi * R ^ 2 * L = 3.14 * 2 ^ 2 * 18.5in = 232.36 in^3

Volume of Motor Casing intruding into drogue bay = Pi * R ^ 2 * L = 3.14 * 1.5 ^ 2 * 5in = 35.325 in^3

Volume of Drogue Bay = 232.36 in^3 – 35.325 in^3 = 197.035 in^3

Volume of Payload Bay = Pi * R ^ 2 * L = 3.14 * 2 ^ 2 * 10in = 125.6 in^3

BP Weight = (PSI/10) * 0.004 * Diameter * Diameter * Length

Constant = (PSI/10) * 0.004 * Diameter * Diameter = 15.96/10*0.004 * 4 * 4 = 0.102144

BP Drogue Bay = Constant * Length =  0.102144 * 18.5 = 1.89 grams

BP Payload Bay = Constant * Length =  0.102144 * 10 = 1.02 grams

Testing

Ejection charges will be tested and video evidence and narrative description will be included here. Expectation is that the charges have enough power to cause the shear pins to break and the sections to separate with enough force to pull the chutes out and extend the shock cords most of their length without excessive shock at the end.

Tested payload bay. Started with 1gm Pyrodex. It was unable to break the shear pins. Tried 2gm Pyrodex, same result. Tried 1gm 4FG BP, broke the shear pins but did not eject the laundry. Tried 2gm 4FG BP, attained the desired result. I suspect the tightly packed parachute is the reason that more BP than calculated was required. Followed up with a test of 3 grams  BP.

Video of 2 gram main test.

Video of 3 gram main test

Tested apogee charge with 2 grams of 4FG BP. Ejection was forceful, but not enough to fully eject the laundry.

Video of 2 gram apogee test

Rigging

Nosecone to Avionics-Bay

Avionics-Bay to Main Body

  • 1″ Forged Stainless Steel eyebolt (provided in kit) on aft nosecone bulkhead
  • 1/4″ Stainless Steel connecting link (McMaster)
  • 1/4″ Stainless Steel connecting link (McMaster)
  • Unknown Brand 18″ drogue chute
  • 16 feet of 1/2″ tubular nylon shock cord (provided in kit)
  • 1/4″ Stainless Steel connecting link (McMaster)
  • 1-1/2″ Forged Stainless Steel eyebolt (McMaster) threaded into forward closure of motor casing

Deployment Sequence

  • Rocket lifts off and attains apogee
  • Both altimeters sense apogee
  • The Telemetrum fires its apogee charge, 1 second later the Easy Mini will fire its apogee charge
  • The apogee charge(s) will break the shear pins and separate the rocket at the main-body / avionics-bay joint
  • The rocket will descend on the drogue chute at approximately 82 ft/s (simulated)
  • The Telemetrum will fire its main charge at 1,200 feet AGL
  • The EasyMini will fire its main charge at 1,000 feet AGL
  • The main charge(s) will break the shear pins and separate the rocket at the nosecone / payload-bay joint
  • The pilot chute will stretch out the harness and pull the deployment bag off the main chute
  • The main chute will start to open and push the slider ring down
  • The rocket will descend on its main chute at approximately 13 ft/s (simulated)

Build Log

Roughly based on the order of steps in the instructions from the kit manufacturer, I plan to write blog posts chronicling my construction of the rocket. Those blog entries can be found here.

Simulations

Based on the RockSim file provided by the kit manufacturer, I have created an Open Rocket file specific to my own rocket.

Velocity off rod 81.1 ft/s
Apogee: 10,480 ft
Max Velocity: 1,244 ft/s (848 mph) (Mach 1.12)
Max acceleration: 562 ft/s2 (17.5G)
Time to apogee: 22.3s
Velocity at main deployment: 81.8 ft/s
Ground hit velocity: 13.3 ft/s
Flight time: 213s (3m 32s)

 

Checklists

Pre-flight

Motor Installation

CAUTION

  1. Assemble the motor per manufacturer instructions.
  2. Validate that eyebolt is securely attached to forward closure, tighten locknut
  3. Inspect the shock cord for cuts, burns, and tangles.
  4. Attach 1/4″ Stainless Steel connecting link from one end of shock cord
  5. Thread the shock cord through the motor tube and out the other end
  6. Install motor in motor tube
  7. Install motor mount mount closure

Avionics Bay

  1. Disassemble
    1. Remove aft bulkhead
    2. Pull sled out
    3. Remove camera bulk plate
  2. Attach lipo battery connectors
    1. to primary altimeter
    2. to backup altimeter
    3. to camera
  3. Test primary altimeter
    1. plug TeleDongle into computer
    2. verify configuration
      1. turn on primary altimeter while in a horizontal position
      2. From AltosUI, click on Configure Altimeter, then choose TeleDongle
      3. Main Deploy Altitude(ft): 1200
      4. Apogee Delay(s): 0
      5. Apogee Lockout(s): 0
      6. Frequency: Channel 0
      7. Telemetry: Enabled
      8. Telemetry baud rate: 38400
      9. APRS Interval: disabled
      10. Callsign: N0YPR
      11. Igniter Firing Mode: Dual Deploy
      12. Pad Orientation: Antenna Down
      13. Beeper Frequency: 4000
      14. turn off primary altimeter
    3. confirm telemetry working
      1. Turn on primary altimeter while in a vertical position
      2. From AltosUI, click on Monitor Flight, then choose TeleDongle
      3. Confirm Battery Voltage Green
      4. Confirm On-board Data Logging Green
      5. Wait for GPS Locked
      6. Wait for GPS Ready
      7. Turn off primary altimeter
  4. Test backup altimeter
    1. plug backup altimeter into computer
    2. verify configuration
      1. turn on backup altimeter
      2. From AltosUI, click on Configure Altimeter, then choose EasyMini
      3. Main Deploy Altitude(ft): 1000
      4. Apogee Delay(s): 1
      5. Apogee Lockout(s): 0
      6. Igniter Firing Mode: Dual Deploy
      7. Beeper Frequency: 4500
      8. turn off backup altimeter
  5. Assemble Avionics Bay
    1. Install camera bulk plate
    2. Install sled
      1. ensure that main altimeter antenna is straight
    3. Attach aft bulkhead
  6. Build ejection charges  – CAUTION
    1. Common Procedure
      1. Drill hole in end of plastic snap top vial
      2. Thread leads of e match out the hole in the vial
      3. Ensure the ends of the e match are shorted to each other
      4. Pour measured amount of BP into the vial
      5. Close the vial
      6. Tape over the opening and around the sides twice with a single long piece of electrical tape.
    2. Primary drogue charge, prepare as above with 2 grams BP
    3. Backup drogue charge, prepare as above with 3 grams BP
    4. Primary main charge, prepare as above with 2 grams BP
    5. Backup main charge, prepare as above with 3 grams BP
  7. Attach ejection charges – CAUTION
    1. Cut leads to desired length (< 6 inches)
    2. Strip the ends of the leads 1/4″
    3. Connect the leads to the appropriate terminal (see step 6)
  8. Test ejection charge continuity – CAUTION
    1. Turn on Primary altimeter while in a horizontal position
    2. confirm beeps,
      1. First beeps are battery voltage. Should be 3 beeps followed by greater than 7 beeps for 3.7 volts
      2. Next is continuity check. Should be dit dit dit for both apogee and main
    3. Turn off Primary altimeter
    4. Turn on Backup altimeter
    5. Confirm beeps
      1. First beeps are battery voltage. Should be 3 beeps followed by greater than 7 beeps for 3.7 volts
      2. Next is continuity check. Should be dit dit dit for both apogee and main
    6. Turn off Backup altimeter

Drogue Chute preparation

  1. Inspection and attachment of aft end shock-cord was done as part of motor installation
  2. Validate that one end of the apogee shock-cord was securely attached to the eyebolt on the forward closure of the motor.
  3. Attach the other end of the apogee shock-cord to the aft bulkhead of the avionics-bay.
  4. Attach the drogue chute  to the loop midway on the shock-cord
  5. Insert the avionics bay into the main body and align the shear pin holes
  6. Insert shear pins into holes and confirm a secure fit

Main Chute Preparation

  1. Inspect components
    1. Check shock cords for cuts, burns, and tangles
    2. Check main chute for tears and burns and shroud lines for tangles
    3. Check deployment bag for tears or excessive burns
    4. Check pilot chute for tears and burns and shroud lines for tangles
  2. Pack main chute
    1. Extend shroud lines, pull them taught
    2. Connect deployment bag
    3. Fold each gore flat
    4. Stuff the chute, crown first into the deployment bag
    5. Lace the lines under the elastic straps
  3. Connect and double-check all connections
    1. Nose cone eyebolt to fore quick-link
    2. Main chute harness to middle quick-link
    3. Pilot chute to deployment bag top loop
    4. Avionics-bay eyebolt to aft quick-link
  4. Insert payload bay over avionics-bay
  5. Secure avionics-bay to payload-bay joint with 8-32 stainless pan head bolts
  6. Pack deployment bag, pilot chute, and shock cord into payload bay
  7. Insert nosecone into payload bay
  8. Insert shear pins into holes and confirm a secure fit

Check Center of Gravity

  1. Find the center of gravity of the fully assembled rocket.
  2. Validate that CG is forward of the minimum CG mark 4″ forward of the CP mark

Final Launch Preparations

  1. Load rocket in tower
    1. With the rail tower in the lowered position, slide the rail buttons onto the rail slot
    2. Slide the rocket all the way to the bottom of the rail stop
    3. Erect the tower, align for plumb
    4. Ensure blast area clear of flammable material
  2. Power up primary altimeter
    1. Through the vent hole marked primary, with a small dowel or screwdriver, depress the switch.
    2. Listen for beeps.
      1. 3 followed by at least 7 for voltage
      2. dit dit dit for both apogee and main pyro charge continuity
  3. Power up backup altimeter
    1. Through the vent hole marked backup, with a small dowel or screwdriver, depress the switch.
    2. Listen for beeps
      1. 3 followed by at least 7 for voltage
      2. dit dit dit for both apogee and main pyro charge continuity
  4. Power up video camera
    1. Through the vent hole marked camera, with a small dowel or screwdriver, depress the switch.
    2. Attempt to verify camera is recording by looking into the hole for appropriate lights, Slowly flashing Yellow.
    3. Wave at the camera
  5. Prepare Igniter
    1. Insert igniter. Be sure it is completely forward and touching fuel grain.
    2. Secure igniter in position
    3. Assure that launch controller is not hot
    4. Be sure all connectors are clean
    5. Hook up igniter to launch controller leads
    6. Be sure that leads are not touching each other or anything else metal
    7. Check launch controller box for igniter continuity
  6. Final Launch Sequence
    1. Insure witnesses are in place and ready for launch
    2. Signal LCO that rocket is ready for launch
  7. Misfire procedures
    1. Ensure launch controller is not hot
    2. Remove leads from igniter
    3. remove failed igniter
    4. resume checklist at step 5 (Prepare Igniter)

De-power Checklist

In the event that the rocket needs to be removed from the launch pad before launch.

  1. Ensure launch controller is not hot
  2. Remove leads from igniter
  3. Remove igniter from motor
  4. Turn off primary altimeter
  5. Turn off backup altimeter
  6. Turn off video camera
  7. Remove rocket from launch tower

Post-Recovery Checklist

Post Flight Recovery Successful Flight

  1. Turn off Primary Altimeter
  2. Turn off Backup Altimeter
  3. Turn off Video Camera
  4. Check for and remove non-discharged pyrotechnics
  5. Have certification team fill out post flight checklist
  6. Disassemble the avionics bay
  7. Connect altimeters to computer to download data
  8. Remove SD card from video camera and plug into computer to download video
  9. Celebrate

Post Flight Recovery Failed Flight

  1. Turn off Primary Altimeter
  2. Turn off Backup Altimeter
  3. Turn off Video Camera
  4. Check for and remove non-discharged pyrotechnics
  5. Have certification team fill out post flight checklist
  6. Drown sorrows

Links, references, & useful information