ORCUS Level 3 Certification

(This is the original posting, now superseded…)

PROJECT: Tripoli Rocketry Association (TRA) Level 3 Certification Rocket

NAME: ORCUS is named after the Kuiper Belt dwarf planet 90482 Orcus. Orcus was a god of the underworld, punisher of broken oaths in Etruscan and Roman mythology.

TAP Mentors: Ben and Elaine Russell

OVERVIEW

Like many other children of the Space Race, I inhaled everything I could find about Mercury, Gemini, Apollo, and follow-on programs.  I built and launched many Estes models to dizzying heights of 50 or even 100 feet!  By the time I reached high school my interest in model rocketry had faded in favor of other things, though.

Then a series of unexpected opportunities resulted in me becoming the faculty advisor for UVA’s new rocketry team in 2023.  Until then, I was unaware of the existence of high-power rocketry as an endeavor; I thought you either built Estes models or went to work for NASA or SpaceX if you wanted to launch rockets.

I started on my Level 1 rocket and quickly became addicted.  My Level 2 rocket flew beautifully at the first Tripoli Central Virginia launch day on 8 Nov 2024. Now, on to Level 3!

I set about designing ORCUS to be a size and weight that I can carry comfortably by myself during launch setup and recovery.  I also want to keep it light so I can launch on smaller and less expensive motors in the future.  I quickly discovered that ORCUS would go transonic on a small M motor, and that seemed like a worthwhile experience to add to my L3 attempt.

STRUCTURE

Let’s start with the elephant in the room: what is that strange pink thing at the aft end? ORCUS as designed will bust the BattlePark 7000 ft ceiling, and I didn’t want to add a lot of weight. I plan to put a drag skirt at the aft end of the rocket, 3D-printed from PETG or ABS and mounted with the same screws that already go into the aft centering ring. It will not extend past the aft end of the body tube. I couldn’t figure out how to model such a thing in OpenRocket, so I added a boattail with the same geometry as the drag skirt – flared instead of tapered. That holds down the apogee nicely.

ORCUS will be a simple dual-deployment rocket.  It will be 6 inches in diameter, 126 inches long, empty mass about 18 lb, mass with motor about 30 lb (before paint).  It will have four fins with a span of about 20 inches.

The body tubes, motor mount, and avionics bay coupler tube will be Blue Tube 2.0.  The nosecone will be fiberglass with an aluminum tip.  The fins will be 0.25 in G10 fiberglass, with tip-to-tip fiberglass reinforcement. (See the flutter analysis at https://www.kq9p.us/wp-content/uploads/Fin-Flutter-Boundary-Calculator-V1-1.zip.) The centering rings, bulkheads, and avionics sled will be Baltic birch plywood, although I may decide to 3D-print the avionics sled with PETG or ABS.  Thrust will be coupled to the body tube using an SC Precision aluminum thrust ring, and motor retention will be achieved using an Aeropack retainer. West System and US Composites epoxies will be used throughout.

The motor mount, centering ring, and fin assembly will be constructed outside the rocket. It will be removable, fastened to the body tube with four machine screws into tapping inserts in each centering ring.

PROPULSION

ORCUS will have a 75mm motor mount capable of accepting an AeroTech RMS-75/6400 motor casing.  At least one test flight – more, if necessary – will be conducted on a large K/small L motor.  The certification attempt will be on an AeroTech M1500G or similar small M motor.

RECOVERY

Recovery will be black powder dual deployment using the same flight computers tested and proven in my L2 rocket, “Radio Flyer”.  The primary is a Featherweight Blue Raven; the backup is a Missile Works RRC2L.  The drogue parachute will be 15”, deployed at apogee.  The main parachute will be 60”, deployed at 500 feet AGL.  Both will be rip-stop nylon.  The recovery harnesses will be tubular Kevlar, 40-50 feet long.

AVIONICS

SIMULATION

The preliminary model was built in RockSim V11.  Flight was simulated on an AeroTech M1500G motor.

DOCUMENTATION

I will document the design, construction, testing, and launch of ORCUS on this page.

SCHEDULE

• November 2024 – review plan with my TAP Members, modify as necessary; order materials;
• December – construct rocket
• January 2025 – recovery system tests
• January/February 2025 – test flights at TCV BattlePark
• March 2025 – certification flight at TCV BattlePark