Standard Liquid Rocket Design

For the purpose of making liquids as accessible as possible, Half Cat Rocketry has created a standard design for bipropellant rockets. Much in the same way that there are particular styles of solid and hybrid motor construction which are widely favored and recommended for their simplicity, this architecture gives a baseline of success from which anyone can copy, modify, and improve.

The standard design is sometimes called a “Half Cat style” rocket. The articles below dive into detail on the Half Cat standard liquid rocket design, which is codified in HCR-1100. The relevant portions of the standard are included in each page. The standard is intended to provide guidance and a bounding framework for maximizing probability of success, based on years of experience. However, these are merely guidelines. Experienced readers may choose to operate outside of them, making specific and intentional choices for potential benefit in exchange for an increased chance of failure.

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Propulsion System

Propellant Tank

The propellant tank stores fuel and oxidizer, and eliminates the need for inert pressurant gas through the use of a sliding piston. The propellant tank includes the following:

• Tank casing

• Bulkheads

• Piston

• Static vent

Thrust Chamber Assembly

The thrust chamber injects, combusts, and exhausts propellant. Several design options are available to mitigate the extreme heat produced during operation. The thrust chamber assembly includes the following:

• Injector

• Chamber

• Nozzle

• Igniter

Fluid System

Propellant is controlled and plumbed from tank to chamber through the fluid system. The fluid system includes the following:

• Main valves

• Feed lines

• Quick disconnect

Vehicle Architecture

Fuel and Oxidizer

Fuel and oxidizer are chosen to provide the simplest, most accessible, and least costly liquid propulsion system.

Interfaces

The standard method for integrating standard Half Cat style rockets provides a robust, reliable structure. Critical interfaces include:

• 2x2 attachment of thrust chamber to propellant tank

• Clean airframe mating to propellant tank

Motor Design

Liquid bipropellant rockets can be easily scaled and customized to a degree largely unattainable by other propulsion systems. To aid in this process, Half Cat Rocketry has laid out guidelines and recommendations, and developed a simulation program to streamline standard liquid rocket design.