When a ground combat vehicle program needs to integrate a new sensor suite, traditional acquisition approaches can add years to the timeline. The platform must wait for the prime contractor to complete design work, conduct integration testing across the entire system, and requalify components that weren’t changed. Meanwhile, the threat evolves and the technology ages.

Modular Open Systems Approach (MOSA) principles address this challenge by designing adaptability into the system architecture from the start. Rather than treating the platform as a monolithic system where every change ripples through the entire design, MOSA establishes clear module boundaries and standardized interfaces that allow new capabilities to integrate without restarting the development cycle.

The Department of War’s recently published Acquisition Transformation Strategy makes this explicit: “Fully implementing Modular Open Systems Approach (MOSA) into acquisition strategies for all programs is paramount for promoting interoperability, competition, technology insertion, performance improvements, and reducing life cycle costs.” For defense contractors, MOSA isn't policy compliance. It’s a design discipline that determines whether programs can field capability on schedule and adapt as requirements evolve.

Why Defense Programs Need MOSA Now

Technology develops faster than traditional acquisition cycles can accommodate. Waiting three to five years for capability upgrades means fielding obsolete systems. Programs need the ability to insert new technology as it matures without redesigning entire platforms.

MOSA defines what stays stable (interfaces, module boundaries, integration rules) and what can change independently (modules, components, subsystems). When a program upgrades computing power, integrates new autonomy features, or replaces obsolete electronics, engineers work within the affected module rather than across the entire system. Testing focuses on the upgraded component and its interfaces, not necessarily the complete platform.

This containment of change delivers real benefits. Programs field capability on schedule because integration work stays bounded. Upgrades happen in months instead of years because teams don’t wait for multi-year Engineering Change Proposals to work through approval channels. Small and nontraditional businesses can compete on specific capabilities and subsystems, opening up greater opportunities. 

Standards Enable the Best of Breed Approach

MOSA works when interfaces follow established standards appropriate for the domain. Ground vehicles typically align with GCIA (Ground Combat Systems Common Infrastructure Architecture) standards that define electrical and data architectures. Survivability systems may reference MAF (Modular Active Framework) for protection system integration. Robotic platforms use RAS-G IOP (Robotic and Autonomous Systems - Ground Interoperability Profile) to define payload interfaces, while SOSA (Sensor Open Systems Architecture) governs hardware modularity for processing and sensor integration.

Software-intensive systems reference FACE (Future Airborne Capability Environment) for avionics, CMOSS (C5ISR/EW Modular Open Suite of Standards) for command and control systems, or domain-specific frameworks for fire control, communications, and autonomy functions. Modern platforms must shoot, move, and communicate using systems that work across multiple standards because these domains weren’t originally designed together. 

Standards make integration predictable by defining the rules both parties must follow. A vendor building a module knows the mechanical envelope, power requirements, data protocols, and software interfaces it must meet. The prime integrating that module knows what to expect. When both sides follow the standard, integration risk decreases, and qualification testing focuses on functional performance rather than basic compatibility.

This supports what the defense community calls a “Best of Breed” approach. Rather than accepting the capabilities a single prime contractor delivers across all subsystems, programs can select the best available solution for each modular element. One firm may lead in electro-optical sensors while another specializes in synthetic aperture radar. We are starting to see this approach take hold in the Army with the recently released Common Autonomous Multi-Domain Launcher (CAML) market survey, where the Army is looking to find the best capability from potentially separate vendors for integration, munitions pallets, and autonomous mobility platforms to comprise the full CAML system.  

MOSA in Practice: Robotic Platforms

GS Engineering demonstrates these principles applied to robotic systems. Building systems with a modular base platform for expeditionary support missions, GS Engineering's unmanned platforms use standardized interfaces aligned with RAS-G IOP requirements to enable rapid payload integration.

The universal baseplate and standardized hydraulic interfaces define clear boundaries between the host platform and mission payloads. Electrical connections, data protocols, and physical mounting follow documented interface specifications that allow different payloads to integrate without custom engineering for each configuration. A bridge-launching payload, material-handling fork, route-clearance grapple, or mobile power generation system can all connect through the same interface.

This modularity delivers operational flexibility. Units can reconfigure the platform for different missions in the field rather than maintaining separate vehicles for each role. From a program perspective, the modular architecture supports capability growth without platform redesign. New payloads can integrate as mission needs evolve or technology advances. Testing focuses on the new payload and interface compliance rather than requalifying the entire platform. 

The model-based systems engineering approach GS Engineering uses during development captures module boundaries, interface requirements, and compliance criteria within a structured framework. This documentation provides the foundation for qualifying new payloads and maintaining interface discipline as the platform evolves.

Breaking Vendor Lock Through Interface Control

Vendor lock occurs when a single contractor controls the technical information required to modify, upgrade, or replace system components. Even when a design appears modular, a lack of access to interface specifications, integration procedures, or test artifacts can prevent competition and force programs to accept sole-source pricing for all future work.

MOSA addresses this through deliberate data rights strategies and interface control. The government asserts rights to interface definitions, module boundaries, and integration documentation that enable competition. Proprietary implementations can remain protected as long as they comply with interfaces.

This changes competitive dynamics. The government can integrate best-available solutions from multiple vendors rather than relying exclusively on the prime contractor. Small businesses and non-traditional defense companies can compete on specific capabilities where they have expertise. 

The XM30 Infantry Fighting Vehicle program illustrates this vision. As a next-generation combat platform designed with MOSA principles from the start, the XM30 aims to enable small and non-traditional businesses to improve specific subsystems for realistic integration into the prime contractor’s platform. A company with advanced sensor technology, innovative fire control algorithms, or novel survivability solutions can compete to provide that capability rather than bidding on the entire vehicle.

Future combat systems may integrate modular lasers for directed energy, modular weapons for kinetic effects, modular computing hardware for processing, and modular sensors that upgrade independently as detector technology improves. Software updates can add capabilities without hardware changes. This vision depends on the interface discipline established during initial system design.

Testing Benefits and Faster Fielding

The testing advantages compound over time. When a program upgrades a single module, qualification focuses on that module and its interfaces. The fire control system doesn’t require resetting when the communication system upgrades. The mobility platform doesn’t need requalification when sensor suites change. This reduces test time, lowers cost, and accelerates fielding schedules

Programs field capability faster because they test what changed, not what remained the same. This matters when technology develops rapidly and operational needs shift. The alternative (requalifying entire systems for every upgrade) guarantees obsolescence. 

MBSE as the Foundation for MOSA Execution

Model-based systems engineering provides the structure MOSA requires. By capturing system architecture, module boundaries, interfaces, and dependencies in a coherent model, MBSE helps teams maintain design discipline as systems evolve.

For MOSA programs, MBSE documents which components can change independently, what interfaces govern their integration, and how requirements trace to implementation. When a vendor proposes a new module, the model shows which interfaces must be satisfied, what dependencies exist, and where integration risk concentrates. MBSE also supports standards compliance verification by capturing interface specifications with testable criteria.

The framework maintains shared understanding across engineering teams, contractors, and government stakeholders who must execute MOSA principles over multi-decade program lifespans.

Designing Systems Structured to Change

MOSA demands up-front investment in interface definition, architecture discipline, and data rights strategy. Programs that treat modularity as an afterthought create systems that appear modular on paper but remain rigid in practice.

The investment pays dividends when programs need to adapt. Technology insertion happens in months instead of years. Obsolescence management becomes an engineering opportunity rather than a program crisis. Competition drives performance improvements and cost reduction throughout the lifecycle.

At GS Engineering, MOSA principles guide architecture from initial concept development. By defining module boundaries, documenting interfaces, and establishing governance structure early, programs gain the flexibility to evolve while maintaining system integrity.

The question isn’t whether modularity adds value. The question is whether programs can execute the interface discipline, data rights negotiations, and governance structures that effective MOSA demands. For programs willing to make that investment up front, adaptability becomes engineering reality. Defense programs can get capability to warfighters faster because systems are designed from the start to change.