Mechanical and Civil Engineering Seminar

  ATA Engineering is an engineering services and consulting company that develops and applies engineering methods to design highly engineered structures such as launch vehicles, satellites, and other spacecraft, as well as theme park rides and medical devices. ATA has had significant roles in the design of the space shuttle, the space station, the MER and MSL rovers, and the James Webb Space Telescope.  As an introduction, I will briefly describe the formation and history of ATA, some of our significant projects, and the way we collaborate with universities to introduce new methods to industry, NASA, and the Air Force.

A salient example of work done in recent years involves the design of new liquid-fueled, upper-stage rocket engines. Many engine manufacturers are adding nozzle extensions (NEs) to increase the ratio of exit diameter to throat diameter and thus increase rocket performance; however, the weight of the NE and of the nozzle itself can become a concern. Optimization of the nozzle and NE structure to reduce the weight requires a good understanding of the dynamic and thermal loads. I will describe the methods we use to obtain more weight-efficient engines.

Of particular interest to the weight-efficient design is what environments can excite the nodal diameter modes of the NE. During main stage operation, the forces that act on the NE include distributed dynamic pressures. These environments will excite the nozzle nodal diameter modes only if the fluctuations in pressure occur in such a way that the distances over which the pressures are correlated to each other are small compared to the wavelengths of the nodal diameter modes. This effect will be illustrated by comparing stresses from a fully-correlated, spatially uniform, fluctuating pressure application to stresses from fluctuating pressures that are highly uncorrelated or spatially random. More generally, I will describe the sources of nozzle dynamic excitation and our attempts to fill in missing pieces of knowledge about the overall dynamic loads on a liquid-fueled rocket nozzle.