DAF27TX02-DV502 — Next-generation Green Monopropellant Gas Generation

Develop a low-power, real-time precision liquid-to-gas phase-change feed system featuring active molecular feedback control to enable the seamless integration of liquid propellants (including next-generation green liquid propellants such as ASCENT and LMP-103S) with high-efficiency in-space plasma propulsion systems. While legacy propellants like hydrazine vaporize with relative ease, next-generation green propellants possess near-zero vapor pressures that streamline ground operations but make efficient vaporization and stable gas-phase molecular composition extremely difficult to control. Proposed solutions must actively monitor and modulate the vaporization process in real time to deliver precise molecular species fractions under tight power constraints, ultimately establishing a versatile, fuel-agnostic propellant conditioning capability to support dynamic space operations and emerging in-space refueling architectures.

The USSF has a desire to use liquid monopropellants for high thrust propulsion (natively in chemical thrusters) and for low-thrust, very energetic missions (in electric propulsion thrusters) - so called Multimode Propulsion (MMP) capabilities - to support Dynamic Space Operations. Such MMP capabilities have a number of very favorable characteristics including high propellant density, reduced need for high pressure storage systems, continued need for chemical propulsion on DoW assets for high thrust prompt maneuver, and compatibility with future on-orbit liquid propellant refueling capabilities. One critical capability gap is an energy efficient, precision propellant feed system which efficiently converts next-generation liquid monopropellant into non-reactive vapor phase products which can be fed into the electric propulsion (EP) thruster. Key challenges arise from the fact that next-generation monopropellants have negligible vapor pressure and are extremely difficult to combust at low temperature and pressure. The desired technology should present a solution for a feed system capable of supporting sub-kW to 100 kW class EP systems: - Operation at minimum on ASCENT propellant (T) or on ASCENT and other monopropellant formulations (O) - Realtime telemetry, including mass flow rate, species composition, and temperature as inputs to the EP device - Maintain consistently characterized molecular composition (T) and extremely stable molecular composition (O) of the output vapor and support both steady-state and pulsed operation at frequencies greater than 5 Hz - Minimal SWaP with particular focus on low power consumption - Incorporate fluid/vapor facing materials that can reliably withstand long-term exposure to green monopropellants and their breakdown products over the required lifespan. Potential issues also include condensation or freezing for long-duration propellant storage in ullage and plenums if these or similar components are used - Demonstrate rapid warmup/gas generation in less than 10 minutes (T) or on-demand (O) - Ensure lifetime design consideration for future multiple refueling opportunities This work directly supports the Contested Logistics Technologies (LOG) Critical Technology Area with respect to space mobility operations.

As this is a Direct-to-Phase-II (D2)2) topic, no Phase I proposals will be accepted and no Phase I awards will be made under this topic. Offerors responding to this topic shall demonstrate “Phase I-type” technical feasibility through prior research, development, laboratory validation, commercial development, or operational demonstrations performed outside of the SBIR/STTR program. Phase I proposals will not be evaluated and will be rejected as nonresponsive. For this D2P2 topic, the Government expects that the small business would have accomplished the following in a “Phase I-type” effort via some other means (e.g. IRAD, or other funded work). It must have developed a concept for a workable prototype or design to address at a minimum the basic capabilities of the stated objective above. Proposal must show, as appropriate to the proposed effort, a demonstrated technical feasibility or nascent capability to meet the capabilities of the stated objective. Proposal may provide example cases of this new capability on a specific application. The documentation provided must substantiate that the proposer has developed a preliminary understanding of the technology to be applied in their Phase II proposal to meet the objectives of this topic. Documentation should include all relevant information including, but not limited to, technical reports, test data, prototype designs/models, and performance goals/results.

The rapid advancement of plasma thruster operation on next-generation molecular propellants is currently bottlenecked by the lack of an energy-efficient, precise, real-time vaporization solution. While previous research has explored thermal and catalytic vaporization strategies, existing options suffer from high power consumption, ill-defined operational lifetimes, inconsistent vapor-phase molecular output, and a total lack of real-time compositional feedback to the thruster. To bridge this critical technology gap and enable commercial transition, Phase II efforts must focus on developing a robust, energy-efficient liquid-to-gas propellant conditioning system when operating on both legacy and next-generation green monopropellants. Proposals must deliver a low Size, Weight, and Power (SWaP) vaporization solution capable of providing a well-quantified, repeatable vapor stream to high-efficiency plasma thrusters, such as Hall Effect Thrusters (HETs) or Magnetoplasmadynamic (MPD) thrusters. Key technical requirements include the ability to deliver real-time feedback on the actual molecular composition being provided, and the capacity to actively modulate operation to target and maintain specific molecular species fractions. While the target operational envelope spans plasma propulsion systems from <1 kW to 100 kW, a single hardware unit is not expected to cover the entire spectrum; rather, performers must demonstrate actual performance across a subset of this range alongside a credible, physics-based pathway for modular scalability. To maximize commercial transition and support the emerging in-space refueling architecture, Phase II projects must focus on developing flight-like engineering development units (EDUs) designed for integration into existing and future plasma propulsion systems. While formal spaceflight qualification (e.g., strict shock, vibration, and radiation acceptance testing) is not required during this phase, performers are highly encouraged to team with established thruster manufacturers. This collaboration will ensure that relevant aerospace engineering best practices, interfaces, and integration protocols are incorporated into the design, positioning the technology for rapid transition.

This technology is directly applicable to both defense and civil spacecraft, delivering a hybrid propulsion capability that enables both prompt, high-thrust maneuvers (e.g., threat and debris avoidance) and high-efficiency, low-thrust orbital transfers. In the near term, the primary market is centered on Department of War (DoW) applications to meet critical requirements for Dynamic Space Operations (DSO), enhanced space warfighting maneuverability, and the rapid emergence of tactical in-space refueling architectures. The primary Phase II deliverable-an Engineering Development Unit (EDU) gas generator-is optimized for direct integration into various molecular plasma thrusters currently under development by commercial space partners. Although final flight qualification must be accomplished on the integrated, combined propulsion system (thruster and gas generator), the Phase II EDU serves as the critical hardware stepping stone. Depending on future government and commercial funding profiles, this technology is well-positioned for independent maturation as a standalone, platform-agnostic product through a follow-on Phase III contract or Tactical Funding Increases (TACFI) effort.