The American Institute of Aeronautics and Astronautics (AIAA) holds a propulsion exposition every year. Part of the exposition are ancillary workshops on topics in the propulsion arena. One of these workshops was held at the Zucrow Laboratories on Purdue University’s Lafayette, Indiana campus. I attended this workshop with about 50 other scientists, industry professionals, students, and two hobbyists (one which was me). What follows are some of the highlights from the AIAA Rocket Testing Workshop that interested me as a rocket hobbyist and space enthusiast.
Propellants include fuels and oxidizers. A fuel is also known as a reducing agent whose role is to donate electrons in a chemical reaction. The oxidizer induces the fuel to release the electrons. The reaction creates energy. And, that energy is used to propel the rocket.
The workshop concentrated primary on liquid propellants and the rest of this article will cover topics in this area. However, I did an article on solid rocket motors that you can find here. A lot of factors come into play when selecting liquid propellants. Desirable properties include:
- Physical properties
- High boiling point
- Low freezing point
- High density
- High decomposition temperature
- Low vapor pressure (reduces cavitation)
- Low viscosity
- Ignition factors (both resistance and promotion)
- Human toxicity
Return to Earth Hybrid Rocket Motor
NASA’s Jet Propulsion Laboratory is preparing a new mission to Mars. The mission is to return Martian soil and minerals to Earth. So, they need a rocket motor in the return vehicle. As it is going to be starting from Mars some of the propellant factors mentioned above come into play.
A hybrid motor is the solution. In this case, it will be a solid rocket fuel and a liquid oxidizer. The propellant is manufactured to not crack or decompose in the low temperatures in space and on Mars. Likewise, the oxidizer needs to stay liquid at these low temperatures.
Additionally, the oxidizer and fuel reaction is hypergolic. That means the fuel and oxidizer ignite on contact. So, there is no need for an igniter on this rocket motor. The innovation in this motor is that the researchers found an oxidizer that stores cold and still is hypergolic.
Suitcase Rocket Motor
One afternoon, the workshop observed the firing of a “suitcase” demonstration liquid propulsion motor. The motor was designed and built by the Propulsion and Energy Group of AIAA. Two Purdue University students explained the operation of the motor. After the briefing, they went through the ignition checklist and fired the motor.
The propellants used in the motor were liquid propane and oxygen. It produced a nice plume and gave a great basic example of the plumbing involved in a liquid propellant rocket motor.
Rotating Detonation Engine
I love the name. Rotating DETONATION Engine. It is essentially a trough where fuel and oxidizer are injected into the bottom of it. The mixture is ignited. Based upon the geometry of the trough, (depth, width, and length), a detonation wave is established. Subsequently, this wave moves down the trough consuming the propellant mixture. If the trough is connected on each end (called an annulus), you get a rotating detonation wave, or it long enough a trough, waves. The open end of the trough is the nozzle of the motor.
Although, the detonations rotate around the annulus, the thrust produced is steady and even out of the engine. This type of engine requires less complex pumps and plumbing. The combustion chain is shorter.
On the other hand, there are disadvantages. The combustion can be unsteady as the detonation cycle comes up to speed. The width of the motor will create base drag if used in rocket propulsion. Finally, the technology is still in its infancy and more testing needs to be done.
Apollo 11 Crew Proxies
The schools of the three members of the Apollo 11 mission are represented in the picture above. Buzz Aldrin and Michael Collins are West Point graduates (like your author) and Neil Armstrong graduated from Purdue University (Dr. Pourpoint).
My attendance at the AIAA Rocket Testing workshop was money and time well spent. Notably, I met a lot of very nice and knowledgeable people and learned a lot. One final picture…….