Salami Rocket

WTF?

Hybrid rocket propulsion system conceptual overview

Oxydizer

I chose N₂O over O₂ because although N₂O carries a lot of conjectural inert nitrogen (64%) oxygen is much harder to handle (tank filling, storage & injection). Additionally the nitrogen, though not participating in combustion, raises the fuel erosion rate and cooles the nozzle enough to reuse it many times. Since the alternatives i found are quite expensive, i use the nitrous oxyde of whipped-cream chargers. By the way, never search for "Sahnespender" at google.

Fuel

Salami: High efficency hydrocarbon based fuel ;)

Simulation

Im using RockSim to simulate the flight stability of the rocket. The behaviour of the N₂0/ hybrid motor is simulated by an external model programmed in C++.

Parts

Overview of the rocket parts

All parts directly participating in the combustion would have to sustain at least 51 bar (vapor pressure of N₂0 at 20°C) but for reasons of safety i assume 200bar as the minimum.

• Run Tank: A light-weight container for the oxydizer capable of sustaining enough pressure
• Throttle Valve: A valve to allow precise regulation of the oxydizer flow from the run tank to the combustion chamber.
• Injector: Aids in vaporizing the (still) liquid oxydizery.
• Combustion Chamber: Where the oxydizer/fuel mix burns. Additionally to pressure (same amount as for the run tank) it has to sustain heat.
• Nozzle: An opening that dramatically accelerates the hot gas escaping the combustion chamber.
• Ignitor: Preheating the fuel and initializing combustion.
• Body tube: Enhances airodynamic properties of the rocket and encapsulates the motor.
• Motor mount: Anchors the motor within the body tube
• Fins: Enhances airodynamic/stability properties of the rocket.
• Recovery System (parachute): Enables slow decent after burn-out for safety and reusability
• Tail camera: It's all about the nice view
• Altimeter: Measurement concludes the fate of the cat
• Electric beacon: Transmits a signal to ease finding the landing site.
• Filling system: Pipework to fill the run tank with nitrous oxyde from whipped cream chargers.

Run Tank

Run tank

Smart Parts C02 aluminium tank for paintball guns with on/off valve.

• Capacity: 591ml (20 oz)
• Connector: 1,27cm (1/2")
• Max Pressure: 200bar

Throttle valve

Throttle valve

An adjustable throttle valve ([1]) intended for use in hydraulics.

• Connector: 1,27cm (1/2")
• Flow rate: 45 l/min
• Working pressure: 350 bar

Injector

Injector

SKR-54UC

• Diameter: 54mm

Combustion Chamber

Combustion chamber

C02 aluminium tank for paintball guns without on/off valve.

• Capacity: 255ml (9 oz)
• Connector: 1,27cm (1/2")
• Max Pressure: 200bar

Nozzle

Nozzle

SKR-54NZL graphite nozzle

• Diameter: 54mm

Ignitor

None selected yet.

Body tube

Body tube

Cardboard tube, intended for postal delivery.

• Dimension: 1000 x 140 x 3 mm

Motor mount & Fins

Motor mount and fins

Wooden centering rings and perspex fins, precisely milled with a CNC machine.

Recover System

None specified/selected yet.

Links

• Basic concept of hybrid rockets at wikipedia
• Excellent tech papers on calculating, planing and building hybrid rockets
• Very helpful articles of Richard Nakka about his experimental rockets
• Rocketry know-how DB (DE)
• Model Rocketry Tips
• Building a Model Rocket Parachute Recovery System by Dr. Jean Potvin
• Rocket thrust Equations