N241-012 TITLE: Real-Time Thrust Control of Solid Propellants

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Hypersonics;Sustainment

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 statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop technology to throttle a solid propellant rocket motor where a rocket motor can be fabricated, and the performance (thrust/time) can be selected at ignition or modified during motor operation, allowing for smart/networked weapon systems that can also fill multiple warfighter needs and respond to evolving threats.

DESCRIPTION: Currently, solid rocket motors are designed to achieve a specified thrust profile based on a detailed analysis of assumed mission needs. Over the course of many years and significant investment, the solid rocket motor is designed, tested, and qualified to achieve this predetermined thrust profile. Thus, when a new missile enters the field, there is a precisely known thrust profile and capability; however, this limits the system to specific and planned threat engagements. Changes to the specified thrust profile result in costly grain redesign and requalification. As new gaps are identified, new missiles are developed to fill those gaps. This increases the number of boutique missiles the military must now manage with the associated logistical footprint.

This SBIR topic seeks to develop a solid propulsion system technology that allows for modulation of thrust at time of launch or during flight to optimize missile performance relative to real-time mission objectives. Real-time thrust control of solid propulsion is a game-changing technology that has the ability to enable collaborative munitions where in-flight missiles can be redirected and throttled to engage evolving threats. Throttleable solid propulsion will also allow for mission flexibility or multi-payload, single-motor capability. When a single system is able to support multiple roles, the need for new boutique systems is reduced, as are the associated development costs.

Thrust control of solid propellants has been demonstrated to varying degrees with technologies—including pintle nozzle—to control the nozzle throat area [Ref 1], high-pressure self-extinguishing propellants [Ref 2], pulsed motors [Ref 3], and electrically-activated propellant [Ref 4]. Some of these technologies are currently utilized in fielded rocket motors because of their ability to control thrust, but their use is very system specific and their thrust control is limited. This topic seeks new or evolved approaches to thrust control of solid propulsion systems. The technology may be complimentary to other thrust control solutions to build a more dynamic overall system.

The objective of this topic is to develop a technology that can create effects on an energetic system to allow for the variation of thrust/time within a rocket motor. The developed technology should maximize compatibility/usage of existing rocket motor materials (propellant oxidizers and binders, insulation, liners, motor cases) and existing industry fabrication methods, as well as leverage industrial best-practices and minimize transition hurdles. The technology needs to minimize the size and weight impact on the rocket motor as gains in flexible energy management can be lost to parasitic weight. Additionally, the technology needs to have a path to be usable in the challenging thermal (-65 °F–150 °F) (-53.9 °C–65.5 °C) and mechanical environments (shock/vibe) required to enter military usage. Hardware and software required to integrate with the technology also needs to be considered as the technology matures.

Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. owned and operated with no foreign influence as defined by 32 U.S.C. § 2004.20 et seq., National Industrial Security Program Executive Agent and Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Counterintelligence and Security Agency (DCSA) formerly Defense Security Service (DSS). The selected contractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances. This will allow contractor personnel to perform on advanced phases of this project as set forth by DCSA and NAVAIR in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material during the advanced phases of this contract IAW the National Industrial Security Program Operating Manual (NISPOM), which can be found at Title 32, Part 2004.20 of the Code of Federal Regulations. Reference: National Industrial Security Program Executive Agent and Operating Manual (NISP), 32 U.S.C. § 2004.20 et seq. (1993). https://www.ecfr.gov/current/title-32/subtitle-B/chapter-XX/part-2004

PHASE I: Identify and design a concept for real-time thrust control of a solid propellant rocket motor. Outline how the concept works (how and where effects are placed on the rocket motor to modulate thrust) and identify the individual components needed for insertion into a rocket motor. Maturity of the individual components will be assessed relative to the development needed for use in a solid propellant rocket motor. A notional system will be developed to demonstrate the bounds for thrust control. Lab scale testing and/or analysis will be performed to demonstrate the feasibility of the concept’s ability to control rocket motor thrust. Testing may or may not include energetic material. Prepare a report outlining the findings of Phase I plus a technology maturation plan for Phase II. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop a Phase II series of prototype rocket motors for evaluation. The prototypes will be used to evaluate the ability to achieve a wide variation of thrust/time profiles from identical motors. The prototype rocket motors will all be identical in design and materials (propellant, nozzle dimensions, igniter, etc.), so that testing can be done on any motor to achieve the desired thrust. The motor size will be based on the capability of the small business, but the propellant grain will not be smaller than 2 in. diameter X 4 in. length (5.08 cm diameter X 10.16 cm length). Pretest ballistics will be performed for each test to determine the thrust/time profile. The thrust/time profile will be preprogramed before each test. Post-test comparisons will be conducted to update models and ensure the prototypes are performing in a reasonably predictive manner. The intent is to demonstrate four different thrust/time profiles from identical prototype rocket motors. During Phase II, the sub-components will be identified and tracked for maturity. A final report will be provided that outlines the prototype design, fabrication, and testing. The report will also outline the less mature aspects of the technology and provide a plan to further mature the technology in Phase III.

Work in Phase II may become classified. Please see note in Description paragraph.

PHASE III DUAL USE APPLICATIONS: Mature the thrust control technology, based on the results of Phase II, for higher fidelity static fire demonstrations. The developed rocket motors will be flight representative with subcomponents fitting into the cylindrical rocket motor (motor case and nozzle can be heavyweight if required). It is still allowable to have an external control unit to modulate the thrust. Demonstrate two static firings of identical rocket motors with different thrust/time profiles. Provide a final report that documents the design and testing results, includes a Technology Readiness Level (TRL) assessment, outlines the volume and mass requirements for a thrust-control system in a tactical missile, and outlines a path to further mature the technology.

The development of solid propellant thrust control would have applications to space-based systems including launching of satellites and satellite maneuvering.

REFERENCES:

1. Burroughs, S. (2001). Status of Army pintle technology for controllable thrust propulsion. In 37th Joint Propulsion Conference and Exhibit (p. 3598). https://doi.org/10.2514/6.2001-3598
2. Petersen, E.L., Seal, S., Stephens, M., Reid, D.L., Carro, R., Sammet, T., & Lepage, A. (2012). Self-extinguishable solid propellant (U.S. Patent No. 8,114,229 B1). U.S. Patent and Trademark Office. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/8114229
3. Moore, T. L. (1995). Pulse motor technology (Report No. CPTR 95-60). Chemical Propulsion Information Agency.
4. Sawka, W. N., & McPherson, M. (2013). Electrical solid propellants: a safe, micro to macro propulsion technology. In 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference (p. 4168). https://doi.org/10.2514/6.2013-4168

KEYWORDS: Solid Propulsion; Thrust Control; Throttling Propulsion; Energetic Material; Rocket Motor; Smart Munitions

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