Title: "Support of Pratt & Whitney TBCC Vehicle Analysis Effort"
Sponsor: Pratt & Whitney, East Hartfort, CT
The next generation of high-speed air vehicles will likely be powered by a combination of turbojet engines (TJ) for the subsonic to mid-supersonic flight regime, and Ram- or Scramjet engines (RJ/SJ) for higher Mach numbers. In addition to enabling long-range transportation, reconnaissance and force projection missions, long-term sustainable access to space will also benefit from vehicle concepts utilizing reusable launchers with air-breathing lower stages that can reach hypersonic speeds. However, due to their complexity and the shortage of flown precedents, the conceptual design of such vehicles poses an extraordinary challenge.
The Pratt & Whitney Advanced Program Office has been looking at efficient ways to understand the impact of some of the key design parameters for such vehicles, in order to guide Pratt & Whitney’s technology investment decisions. Such parameters are expected to include the transition Mach number, i.e. the Mach number at which the ram/scramjet takes over from the turbine engine, and the sizing of the thermal system that will have to manage the expected high thermal loads. While the transition Mach number is a key driver in the selection and design of the propulsion system, the vehicle’s heat balance will affect the design of the thermal protection system as well as the vehicle’s take-off gross mass.
In addition to the impact of key design parameters such as the ones mentioned above, the assumptions underlying the analysis also have to be understood and managed as well. Determining the impact of aerodynamic drag, aeroheating, dynamic pressure, vehicle size and other parameters plays an important role in this context.
Achieving these objectives is facilitated by a parametric environment that provides decision-makers with a rapid-turnaround, interactive means of exploring the design space and predicting the impact of technologies, well before significant investment and design decisions are made. The related approach must also take into account the inevitable uncertainties that affect any assumptions at the early stage of the design process.
The Aerospace Systems Design Laboratory (ASDL) of the Georgia Institute of Technology was contracted to support the Sponsor in this effort. Its experience and expertise in the areas of design methodology, stochastic approaches, technology analysis and selection, and hypersonic vehicle modeling and simulation was combined with the Sponsor’s own methods and tools for the design of advanced propulsion systems and vehicles.
The effort was divided into the following tasks, which were executed sequentially:
At the beginning of the period of performance, ASDL collaborated closely with the Sponsor to refine and coordinate the planned effort. Tools and processes in use by the Sponsor were analyzed, Sponsor-side contacts were identified, and a more detailed set of requirements was generated.
ASDL created a customized modeling, simulation and analysis process derived from its proven approaches, based on the Sponsor’s needs as identified during Task 1. The process was designed to utilize the parametric environment to be created under Task 3.
Task 3 was focused on establishing the parametric environment that enables the process defined during Task 2. The main ASDL tool adapted for use within the scope of this project was a rapid design space exploration tool. The modeling of the vehicle propulsion system was a key part of the proposed creation of a robust, rapid-turnaround capability. ASDL provided the Sponsor with the appropriate Design-of-Experiments tables that enabled the Sponsor to perform the necessary runs of its in-house tools. The resulting data was then used by ASDL to create surrogate models through Response Surface Equations and other techniques.