TECH FOCUS AREAS: General Warfighting Requirements (GWR) TECHNOLOGY AREAS: Air Platform OBJECTIVE: This topic seeks to develop energy deposition technologies for scramjet ignition and combustion augmentation using only on-board vehicle resources (e.g., vehicle fuel, air, and electrical power). DESCRIPTION: The U.S. Air Force has invested in scramjet ignition technologies from both a fundamental [1 4] and applied perspective. Specifically, focus has been on Insensitive Munitions compliant ignition systems for missile platforms, which has allowed for accelerant-type systems to be used, such as pyrophorics/hypergolics, alternative oxidizers, etc., as well as consumables, such as compressed fuels or oxidizers. While many of these systems are suitable for packaging and application to expendable hypersonic systems, some are not ideal for reusable hypersonic platforms. In addition, moving away from systems with accelerants and other consumables would reduce the complexity in expendable systems. Therefore, there remains a desire to develop/mature scramjet ignition systems that only use on-board resources, such as the vehicle fuel (e.g., JP or RP-type), air, and electrical power. In addition to ignition, there is a desire to augment combustion processes in scramjet engines via energy deposition. By strategically depositing energy within an engine, combustion can be accelerated, therefore enhancing overall engine performance during off-design conditions. These combustion enhancement technologies also need to only use on-board vehicle resources but have the additional constraint of high duty cycle or continuous operation during certain portions of a flight profile. This topic seeks to produce new or mature existing energy deposition methods for scramjet ignition and combustion augmentation only using vehicle fuel and/or air and/or electrical power. It is envisioned the developed energy deposition technologies may be suitable for ignition or combustion augmentation, but do not have to be applicable to both because of the different operational requirements set. Specifically, ignition systems typically require operation for short duration (or order milliseconds to seconds) and should be focused on the spatial extent of influence from the electrical and/or chemical energy deposition. Combustion augmentation systems require long duration operation and, therefore careful considerations of power efficiency, thermal management, and repeated cycling. Specific focus on the applicable technology development should be placed in the areas of power and fluid requirements, as well as the spatial and temporal distribution of electrical and/or chemical energy. The energy deposition devices should try to avoid physical protrusions from the wall where it is expected to be inserted within a combustor (either in the subsonic flame holder region or in supersonic flow). Experience has shown protruding devices have limited cycle/lifetimes. Rather, it is desired any developed devices can either deposit the electrical and/or chemical energy in a large volume near the wall, or project it away from the wall by fluidic or other means. The larger the volume/region that the energy can be deposited, the greater chance of ignition success or combustion augmentation. If the developed systems are successful, the government may choose to test in relevant scramjet environments. The effort will culminate in an energy deposition system for hypersonic platforms that uses no consumables beyond the fuel and electrical power already on-board a vehicle and bleed and/or ram air. Proposals detailing systems that require/store additional fluids will not be considered. PHASE I: Selected efforts will conceive and develop energy deposition technology and show capabilities versus baseline spark discharge systems, typically localized energy deposition of order of several Joules with specific parameters provided after award. The device requirements of power/energy, fuel and/or air pressure and flow rates, volume and mass packaging constraints, as well as the spatial and temporal distribution of the energy from the device need to be well documented. Phase I deliverables will include a final report containing the preliminary system design, estimated performance results, scaling to different device size or energy output, and/or proof-of-concept of the device operation. PHASE II: Companies selected for Phase II will complete development of the energy deposition technology and perform bench testing of the system to demonstrate performance results. If successful, application and demonstration in a relevant scramjet environment at a government facility is desired depending upon testing availability and priority. Focus should be on validation of the system in harsh environments experienced by hypersonic vehicles and packaging to meet power, volume, and mass constraints. Phase II deliverables will include the energy deposition system and a final report that documents the demonstration results. PHASE III DUAL USE APPLICATIONS: Phase III efforts would optimize the design of the energy deposition system for application to different engine types (reusable or expendable), different engine scales, or mission profiles. It would also involve performing engine testing of the packaged system in relevant scramjet environments to validate performance. NOTES: The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the proposed tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the Announcement and within the AF Component-specific instructions. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. Please direct questions to the Air Force SBIR/STTR Help Desk: usaf.team@afsbirsttr.us REFERENCES: [1] L.S. Jacobsen, C.D. Carter, T.A. Jackson, S. Williams, J. Barnett, C.-J. Tam, R.A. Baurle, D. Bivolaru, and S. Kuo, Plasma-assisted ignition in scramjets, Journal of Propulsion and Power, Vol. 24, No. 4, 2008, pp. 641 654. ; [2] T.M. Ombrello, C.D. Carter, C.-J. Tam, and K.-Y. Hsu, Cavity ignition in supersonic flow by spark discharge and pulse detonation, Proceedings of the Combustion Institute, Vol. 35, No. 2, 2015, pp. 2101 2108. ; [3] D. Cuppoletti, T. Ombrello, C. Carter, S. Hammack, J. Lefkowitz, Ignition Dynamics of a Pulse Detonation Igniter in a Supersonic Cavity Flameholder, Combustion and Flame, Vol. 215, 2020, pp. 376-388. ; [4] S. Hammack, T. Ombrello, Spatio-Temporal Evolution of Cavity Ignition in Supersonic Flow, Proceedings of the Combustion Institute, Vol. 38, 2021, pp. 3845-3852. KEYWORDS: scramjet ignition; turbine-based combined cycle; missile; hypersonic; ignition; combustion; air-breathing propulsion
