Project Objectives

The Pulse Detonation Engine Technology (PDET) Project within the Propulsion and Power R&T Base Program will evaluate the application of pulse detonation combustion technology to hybrid subsonic and supersonic gas turbine engines for commercial and military applications and combined cycle propulsion systems for access to space applications. This will be accomplished through the conceptual design of a number of possible system configurations followed by the "breadboard" demonstration of the critical sub-system(s) of the best candidate system(s). This propulsion system development process will be supported by the development of and demonstration of advanced detonative and non-detonative components required for system operation.

High frequency (>60 Hz) pulse detonation combustors have been developed over the past 5 years by several commercial firms and government laboratories in configurations consistent with aerospace propulsion applications. These combustors have an advantage over traditional near-constant pressure combustors in being more thermodynamically efficient by approximating constant volume (pressure gain) combustion. At the same time, engine systems based on these combustors are expected to be significantly simpler than current engine designs due to reduced air and fuel inlet pressure requirements.

Pulse detonation based propulsion systems can be broadly classified into three categories. "Pure" PDE's are the simplest systems consisting of an array of detonation tubes, an inlet, and a nozzle. Combined-cycle PDE systems consist of a PDE combined with a ramjet/scramjet flowpath or other propulsion cycle where each cycle operates in a different speed range to optimize overall system performance. Hybrid PDE's make use of detonative combustion in place of constant pressure combustion, usually in combination with turbomachinery. For any of these systems, the requirements for the components external to the detonation tubes are not well understood. The use of an unsteady detonative combustor will have major impacts on those components which need to be evaluated. The overall system performance is by the same token poorly characterized because of the unknown component performances. The PDET project will address these issues for combined-cycle and hybrid engine concepts, while the GRC/DFRC PDE Flight Research Project will be addressing these issues for the pure PDE intended for primarily military applications.

The development of pulse detonation based propulsion supports the following AT goals.

Revolutionize Aviation (Goal One)

Protect Local Air Quality and Our Global Climate - Reduce NOx emissions of future aircraft by 70% by 2007 and by 80% by 2022 (Baseline: 1996 ICAO standard). Reduce CO2 emissions of future aircraft by 25% by 2007 and by 50% by 2022

Hybrid pulse detonation systems are thermodynamically more efficient than standard gas turbine systems as well as being more light weight, thus reducing CO2 emissions. Pulse detonation also offers new solution space in which to pursue reduced NO emissions.

Improve the Mobility of U.S. Citizens by Reducing Travel Time for Both Short and Long Journeys by Air - Reduce inter-city door-to-door transportation time by half by 2007 and by two-thirds by 2022. Reduce long-haul transcontinental travel time by half by 2022.

Hybrid and combined cycle pulse detonation systems are expected to be efficiently operable to Mach numbers as high as 5 at a significantly lower cost than gas turbine engines due to simplified designs, lower part count, and reduced engineering material requirements.

Advance Space Transportation (Goal Two)

Make Space Travel as Safe as Today's Air Travel - Reduce the incidence of crew loss by a factor of forty by 2010 and by a factor of 100 by 2025.

The potential for increased performance at reduced weight will provide additional vehicle weight fraction available for increasing health monitoring and more robust structural designs.

Reduce the Cost of Taking Payloads to Orbit - Reduce the cost of delivering a payload to Low Earth Orbit (LEO) by a factor of ten by 2010 and reduce the cost of inter-orbital transfer by a factor often 2015. Reduce costs for both by an additional factor of ten by 2025.

The combination of pulse detonation cycles with other air-breathing and rocket cycles offers increased overall system performance at lower weight and cost for access to space applications.

Pioneer Technology Innovation (Goal Three)

Engineering Innovation - Develop the advanced engineering tools, processes, and culture to enable rapid, high-confidence and cost efficient design of revolutionary aerospace systems.

The mechanical simplicity of pulse detonation propulsion systems will enable shortened design cycle times. The system and cycle analysis tools being developed under this project will also aid in the design of new systems employing pulse detonation.

Technology Innovation - Develop the revolutionary technologies and technology solutions that enable fundamentally new aerospace system capabilities or new aerospace missions.

Pulse detonation engines operate on a different thermodynamic cycle than conventional gas turbine engines, offering different operational modes and performance levels at various flight conditions. Mission-specific PDE designs could enable new aerospace missions, depending on requirements.

Support of DOD Goals

Provide fundamental technology development, world-class facilities, and technical expertise to maintain the operational dominance of U.S. military aircraft while reducing their life-cycle costs by 25 percent within 10 years, and by 50 percent within 25 years.

The technology developed within PDET will be broadly applicable to single cycle "pure" PDE systems under consideration for a variety of DOD missions including missiles and tactical aircraft.

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Technical Summary

The development of pulse detonation based propulsion systems presents a series of difficult technical challenges due to the unsteady nature of the flow processes and the severe pressure/thermal environment created. Current design and analysis methodologies need to be significantly modified, or discarded altogether. The PDET project will look at those technologies critical to the successful design and demonstration of a viable PDE-based propulsion system consistent with NASA's aerospace propulsion goals.

The major deliverables at the end of the 3-year project duration are as follows.

Analysis of pulse detonation based propulsion system options completed and downselect to most promising configuration(s)
Demonstration of a "breadboard" pulse detonation propulsion system and/or sub-system for a NASA application.
Experimental and analytical evaluation of environmental compatibility of pulse detonation based propulsion systems completed with mitigation strategies identified.
Small scale pulse detonation test bed operational for the evaluation of fundamental issues relating to pulse detonation combustion such as heat transfer, measurement techniques, and injector/combustor configuration.
Multi-cycle systems analysis tool completed and validated.
Evaluation of material/structural concepts for long-life pulse detonation combustors completed and downselected configuration demonstrated.

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Milestones

Milestone	Output	Outcome
PDE-based System Conceptual Design	Design concepts for hybrid and combined cycle propulsion utilizing pulse detonation complete with 1st order system performance analysis and component performance sensitivities.	Credible understanding of potential system performance levels and the ability to target component research to critical system performance issues.
PDE-Based Propulsion System Sub-System Test	Critical sub-system (multi-component) performance of 1 or more best available PDE propulsion system concepts.	Quantitative assessment of the performance potential of PDE hybrid/combined-cycle propulsion including non-idealized loss mechanisms.