#rocket nozzle

Rockets operate on a pretty simple principle: if you throw something out the back really fast, the rocket goes forward. Practically speaking, we accomplish this with a combination of chemistry and physics, by burning fuel and oxidizer together and accelerating the exhaust out a nozzle. Solid rocket propellant, like that found in the model rockets shown here, is a combination of fuel and oxidizer that don’t react until they’re ignited. You don’t want your rocket to just explode as soon as it’s lit, though, so solid rocket motors are carefully designed to burn in a particular way. By packing the propellant into different shapes -- and even including patterns of propellants with different burn rates -- engineers can create a rocket that burns with the thrust pattern they want. 

In the case of this model rocket motor, what we observe is not really how it is intended to burn; you can see how some of the combustion products are working their way out of cracks that wouldn’t normally exist. But the video and animation do show how the burn front moves gradually through the engine, allowing it to produce a relatively steady amount of thrust for a longer period before reaching the darker burning propellant on the left, which would normally launch the model rocket’s parachute. (Image and video credit: Warped Perception; via Gizmodo)

Kyll Schomberg’s article “Analysis of a Low-angle Annular Expander Nozzle” was published in Shock and Vibration (dx.doi.org/10.1155/2015/675861), you can read online, no subscription required.

FLIP PhD student Kyll Schomberg reports:

I recently attended the AIAA Propulsion and Energy 2014 forum in Cleveland, Ohio. The event combined both the 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and 12th International Energy Conversion Engineering Conference with participants from a number of international academic and industrial institutions. The event featured a range of plenary panels, keynote speakers, technical forums and paper presentations.

I was fortunate to present two papers on nozzle design and efficiency. One on the Design of High Area Nozzle Contour Using Circular Arcs that highlights the potential for a reduction in nozzle length (and therefore engine weight) without reducing performance and another paper on a Geometric Analysis of the Linear Expansion-Deflection Nozzle at Highly Overexpanded Flow Conditions that identifies the relationship between nozzle geometry and efficiency in the altitude-adaptive expansion-deflection nozzle concept.

Highlights of the conference were Al Romig’s keynote address on the history of Lockheed Martin with a focus on the Skunk Works, the town hall forum with Technical personnel from Blue Origin, Virgin Galactic, SpaceX and NASA Marshall and speaking to one of the engineers that was involved in the development of the Vulcain 2 core stage engine used in the Ariane 5 launch system after my talks.

Some pictures from the event, courtesy of AIAA: