Design

Guidelines

The design guidelines for Arnor are set by the Hedonic Treadmill project

• The rocket design cannot be based off:
  • Past or present hobby rocket kits (no clones or upscales/downscales)
  • Past, present, or future sounding rockets, missiles, or other military, commercial, or scientific launch vehicles
• The rocket design will be tailored for its missions. Arnor will be designed for:
  • Subsonic speeds
    • The nose cone is a 3:1 Ogive with a phenolic tip. The tip will be slightly rounded to make the nosecone into a roughly elliptical shape
    • Three fins is lower drag than four and there's no need to worry about the trans-mach CP shift
    • The fins will have a true NACA airfoil profile to lower drag and improve force/lift when making aerodynamic corrections
  • G–I motors
    • The motor mount will be designed around an Aerotech 38/480 reload casing
    • Initial flights will be on unrestricted, Hazmat-free, reloadable motors: Aerotech G79W (29/120) ALTERNATIVE: Loki Research G80 (38/120)
    • Certification flight: Aerotech H128W (29/180)
    • Full send: Aerotech I59WN (38/480) (dual-deploy configuration) >7 second burn to >7000 feet
  • Flight as both a Class 1 and a Class 2 rocket
    • The maximum liftoff weight of a Class 1 rocket is 1500g; the recommended thrust to weight ratio is 5:1.
      • An Aerotech G79 has an initial thrust of 92N so it can lift a 1880g rocket at a 5:1 ratio (that number comes from converting N to lb [force], dividing by 5, then converting lb to g—I’m sure there’s a better way to do that calculation)
      • A Loki Research G80 has an initial thrust of 112N so it can lift a 2280g rocket at a 5:1 thrust to weight ratio
  • Single & dual deployment configurations
    • The estimated liftoff weight for the dual deploy configuration is too high to achieve the 35 MPH target airspeed when leaving the launch rail when flying with unrestricted motors (≤80 N average thrust)
    • The booster/fin can is a zipperless design so the single deployment configuration will use a piston to ensure the recovery gear is properly expelled from the airframe
    • In both cases the avionics bay will be “pinned” to the airframe, Jarvis-style, using the heads of socket-hed screws but instead of plywood bulkhead backing they will be anchored with PEM nuts
  • Testing avionics payloads (and LiPo batteries) of increasing complexity towards redundant dual deployment
    • Configurations:
      • Single-deploy with EggTimer Apogee
      • Single or Dual deploy with redundant AltusMetrum EasyMinis
      • Single or Dual deploy with redundant EggTimer Quarks
      • OPTIONAL: Some other configuration of available electroncics:
        • Eggtimer Apogee (1 available)
        • Eggtimer Quark (2 available)
        • AltrusMetrum Easy Mini (2 available)
        • EggTimer Wifi Switch (2 available)
    • The goal is to have WiFi arming for all avionics payloads. All wireless systems will have independent, externally-accessible screw switches (likely FingerTech) for a safety cutoff
    • LiPo batteries will be used throughout but more research on connector, capacity, and care is needed
    • Terminal block design is TBD due to tight tolerances in the avionics bay
  • Testing ejection charge designs
    • Centerfuge tubes for convenience on simpler avionics payloads
    • Jarvis-style elongated charge canisters e.g. ¼” × 5.75” paper straw lined charge in a high-temperature G10 tube