Integrated Rocket Ramjet

Design and model an integrated rocket ramjet. The engine transitions without sacrificial parts from the rocket to the ramjet stage upon reaching the design speed. Key features include a sealing inlet and a liquid fuel ignition source that doubles as a barrier to shield components from the solid rocket propellant.

Background
A ramjet is a type of engine used for supersonic flight. It operates at speeds around Mach 3 but cannot function at speeds much lower than Mach 1.5. Because of this, ramjet engines are typically brought to an ideal speed before activating. Currently this is done in two ways; first being by a booster rocket that detaches after usage, and second by carrying the ramjet engine on a jet plane and dropping it when the engine ignites. The goal for this project is to develop a third way for ramjet flight, utilizing a solid rocket combustion chamber and a nosecone that can function as an inlet at high speeds.

Deliverables
The deliverables for this project include; a detailed design for an adjustable nosecone and diaphragm that utilizes aerodynamics, a quarter cut out model showing the functionality of the integrated ramjet, and a basic model of the rocket that can be used for simplified testing of the nosecone, diaphragm, and other assemblies/components.

Project Learning
Most of the project learning for the integrated rocket ramjet revolved around ramjets and their functionality, as well as solid rockets and how to design them. For this design, in order to get the ramjet to speed a solid rocket will be attached to the ramjet engine. Once the propellant is burned, the rocket will function as the combustion chamber for the ramjet. To make this design possible, research had to be done on both rocket propellants and ramjet engines.

The image on the left below shows different grain geometries for solid rocket propellant. This was useful because it helped us decide which geometry would give us the best thrust pattern to obtain the proper transition speed. We ultimately decided to go with #2, this option provided the rocket with consistent thrust which allows for easier calculations and design.

Along with propellant research we found information on the functionality of the ramjet. Below on the right is a basic image on how a ramjet operates. Using this information we were able to brainstorm ideas on how to create a moving nosecone and where to store the liquid fuel for the ramjet part of flight. We found the best place to store the liquid fuel would be in the extra space by the diffuser (the yellow section of the image).

Concept and Design
To get the Ramjet to its ideal flight path, solid rocket propellant is stored in the ramjet’s combustion chamber and functions initially as a rocket booster. During this stage the nose cone to the ramjet engine will remain shut and a diaphragm will be in place to block any solid propellant from getting into the rest of the engine (this can be seen in the first image below).

Once the solid propellant is burnt, the nose cone and diaphragm open up allowing the ramjet to begin operation. This part of the design is important because it allows for the whole body to become the ramjet, and does not require the rocket portion to drop off. Instead the space where the solid rocket propellant was stored is now the combustion chamber for the ramjet. The ramjet then takes over for the rest of the flight, operating at its design conditions (this can be seen in the second image below).

Nosecone Design
In order to open and close the nosecone between rocket and ramjet flight, a screw mechanism has been developed to close the gap. This system uses a screw and a motor to push the front of the nosecone against the cowling to create an air tight seal, ideal for the rocket portion of flight. Once the rocket stage is complete the screw will spin within the motor pulling the front section of the nosecone back along guides. Now the inlet will be ideal for the ramjet section of flight.

Diaphragm Design
The second crucial component to the integrated rocket ramjet is the opening diaphragm which will take place during the transition to ramjet operations. The diaphragm consists of three bars to support a hinge, three bars to support the ends of the flaps, and the flaps that will open and close themselves. The flaps will remain closed due to the physical pressure of the solid fuel as well as the pressure created when the propellant is burning. Once the solid fuel is completely burnt the air from the moving nosecone will force the flaps open. This transforms the area where the solid rocket fuel was into a combustion chamber.

Machining and Modeling
To properly show the functionality and ingenuity of our design, we have developed a working 3D computer model and a quarter cutout machined model of the integrated rocket ramjet.

The 3D model has been completed and can now be used for further math modeling and testing. The quarter cutout is currently undergoing machining and some images can be seen below.

Below on the left is the rocket nozzle currently being machined using a CNC Lathe. Below on the right is a test for a visual representation of the solid rocket propellant.

Document Archive
[[Media: Meeting_Minutes2.0.pdf|Meeting Minutes]]