The U.S. Space Force (USSF) is seeking innovative propulsion solutions for Very Low Earth Orbit (VLEO) operations through its Small Business Innovation Research (SBIR) program. The objective is to advance propulsion technologies that enable sustained space operations in the VLEO regime, addressing challenges such as high atmospheric drag and dynamic orbital variations. This initiative is crucial for enhancing the Department of the Air Force's capabilities in space operations, particularly in intelligence, surveillance, reconnaissance, and communications. Interested applicants must prepare proposals demonstrating a proven technology ready for Phase II, with a focus on feasibility studies and integration pathways, as the solicitation opens on May 28, 2025, and closes on June 25, 2025. For more details, visit the official SBIR website at https://www.dodsbirsttr.mil/topics-app/.

## Description

The US Space Force (USSF) looks to accelerate emerging technologies and mature concepts of operations (CONOPs) as it pertains to novel propulsion solutions for the VLEO regime. By advancing these core capabilities, this topic will meet the Department of Air Force&rsquo;s (DAF) Operational Imperative 1 &ldquo;Defining Resilient and Effective Space Order of Battle and Architectures,&rdquo; and 7 &ldquo;Readiness of the Department of the Air Force to transition to a wartime posture against a peer competitor.&rdquo;The Space Force wishes to explore innovative technologies with demonstrated commercial value in the non-Defense sector, i.e., through existing products/solutions, which apply to Space Force applications, i.e. dual-purpose, commercial and military technologies/solutions. It is important that potential solutions have a high probability of keeping pace with technological change. This topic seeks to explore potential commercial products enabling sustained space operations in the emerging VLEO market for potential use in a variety of Space Force missions. Traditional propulsion technologies are not optimized for sustained operations in this regime due to high atmospheric drag, increased atomic oxygen exposure, and dynamic orbital variations. This topic solicitation aims to advance the state of the art in VLEO propulsion, enabling extended mission lifetimes, novel orbit maneuvering concepts, and discovery of future operations in non-traditional orbits.

## Objective

As the space operational environment evolves, there is a need for new technologies and capabilities in non-traditional orbital regimes that allow for a more sustainable and resilient environment. This topic will examine new propulsion technologies and associated mission designs that advance the ability to perform VLEO space operations. The primary intent is to gain significant development in propulsion technologies and capabilities enabling persistent space operations in VLEO. Leveraging these emerging VLEO propulsion technologies will infuse innovation into the traditional space operations framework by reducing reliance on space mission operations in Low Earth Orbit (LEO) and unlocking lower altitude space operations.

## Phase I

This topic is intended for technology proven ready to move directly into Phase II. Therefore, Phase I awards will not be made for this topic. The applicant is required to provide detail and documentation in the D2P2 proposal which demonstrates accomplishment of a “Phase I-type” effort, including a feasibility study. This includes determining, insofar as possible, the scientific and technical merit and feasibility of ideas appearing to have commercial potential. It must have validated the product-mission fit between the proposed solution and a potential Air Force and/or Space Force stakeholder. The applicant should have defined a clear, immediately actionable plan with the proposed solution and the DAF customer and end-user. The feasibility study should have:<ol><li>Clearly identified the potential stakeholders of the adapted solution for solving the Air Force and/or Space Force need(s).</li><li>Described the pathway to integrating with DAF operations, to include how the applicant plans to accomplish core technology development, navigate applicable regulatory processes, and integrate with other relevant systems and/or processes.</li><li>Describe if and how the solution can be used by other DoD or Governmental customers.</li></ol>

## Phase II

Operations in the VLEO regime have potential to be a &ldquo;game changing&rdquo; opportunity that creates the ability to fight through any perturbations that may occur in other orbits during or following a conflict. The project scope will investigate transformative technologies aimed at the development and maturation of propulsion technologies tailored for the VLEO domain. To accomplish this, the topic will focus on the following core technology areas: (1) Enhance Drag Compensation Capabilities: Developing propulsion systems that counteract atmospheric drag at altitudes between 100-400 km, allowing for allowing for an improvement in mission duration over the current state of the art for the selected propulsion concept and space platform in VLEO.(2) Improve Propulsion Efficiency: Advancing VLEO propulsion systems that provide high specific impulse with minimal power consumption to support small satellite and large constellation architectures.(3) Enable Persistent VLEO Operations: Supporting mission requirements for intelligence, surveillance, reconnaissance (ISR), communications, and space domain awareness through sustained low-altitude station-keeping.(4) Leverage Nontraditional Propellant Sources: Investigating air-breathing or other innovative in-situ propellant collection methods to support continuous thrust without onboard propellant limitations, in addition to non-traditional propellants within volume constrained space platforms.Proposals should focus on developing scalable propulsion architectures that allow for precise altitude control, station-keeping, and responsive maneuvering, while also considering the value proposition trade space for low-cost, expendable system designs for rapid response missions with limited-lifetime platforms. Successful Phase II proposals and awards will provide evidence of market fit in a detailed business plan, including total available market (TAM) and served available market (SAM); revenue model and plan; and scaling plan, including supply chain and manufacturing. The successful Phase II capability shall achieve TRL-3 or higher, as documented in a final report with laboratory and/or field demonstrations.

## Phase III: Dual Use Applications

Some solutions may go from Phase II to Phase III as soon as the product-market fit is verified. Potential Phase III awardees will transition the adapted non-Defense commercial solution to provide expanded mission capability for a broad range of potential Governmental and civilian users and alternate mission applications.

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