Considerations Using an Expander Cycle

One of the primary goals of our project is to use a turbopump to feed our propellants into the combustion chamber. While there are many different options, a rocket engine that uses an expander cycle is looking to be more viable for our application. 

Expander cycles have a few main advantages:

• They use expanded gas from your regen channels, allowing cooler gas temperatures to be used in your turbine compared to something such as a gas generator
• They scale well for smaller rocket engines
• There are variations that can simplify your turbopump assembly

One such variation is the Open Expander Cycle, in which your propellants are used by the turbine and then dumped downstream of the nozzle exhaust. This has the advantage of using your turbine exhaust gases without also worrying about back pressure on your turbine (if you were to route the exhaust to the chamber).

Credit: NASA/wdgreene

Another variation is the Dual Split Expander Cycle. This has the advantage of keeping both the fuel and oxygen pump separate. This simplifies bearing and seal design at the trade of having more complicated engine plumbing. 

Credit: NASA/wdgreene

It's also worth noting that these engines have been getting more recent attention, with Mitsubishi Heavy Industries producing the LE-5B engine running on a similar expander bleed cycle.

Credit: Mitsubishi

In summary, a trade study is in order to make more informed decisions on what combustion cycling may look like on our engine and if combining the two variations above would work.

-Zach

Brainstorming

INTRO

The goal of our project is to push the boundaries of amateur propulsion. By tackling some of the most complicated systems associated with rocket propulsion, we hope to learn and help others learn what makes a rocket engine a good rocket engine. 

Performance

- 250+ specific impulse 

- 1000+ lbf

Thrust Chamber and Feeds

- pump fed

    - expander cycle? (won't have to worry as much about turbine melting)

        - Expander bleed cycle (only some prop is heated and used on the turbine, which is then dumped overboard)

    - open cycle gas generator?

    - tap-off cycle?

- possibly throttleable?

- regeneratively cooled

    - film cooling? Ablative? Heatsink? WATER?????(jk)

- printed or machined chamber

    - electroplating copper

    - machined jacket

    - composite jacket

    - CuCrZr print

Propellants

- LOX paired with LNG, RP-1, IPA, Ethanol, Methanol (some hydrocarbon)

- GOX/Nitrous for something more tame (should we avoid cryo?) No :)

Igniter

- Acoustic

- Torch

- Hypergols ??? (Turpentine and Nitric Acid)

- Fuse/solid motor 

Injector

- Swirl

- Pintle 

- doublet impinging

Testing

- test out at FAR?! one summer

- LN2 cold flows with turbopump

- injector water flows

Welcome!

 Welcome to Rocket Lads! 

We're a group of students looking to redefine what's possible for amateur rocketry. Check out the "About Us" page to learn more and the "Project Overview" sub-page to get a taste of what we're doing. 

We hope you enjoy this project as much as we will!