As militaries shift toward networked air combat and drone-centric operations, propulsion has emerged as a critical bottleneck. Defense primes and startups alike are racing to develop small jet engines that can power everything from attritable drones to advanced Collaborative Combat Aircraft (CCAs). This propulsion arms race is reshaping the aerospace supply chain—and redefining what’s possible in unmanned flight.
Why Propulsion Is the New Bottleneck in Drone Development
The explosion of interest in uncrewed aerial systems (UAS) across militaries worldwide has created a surge in demand for compact yet powerful jet engines. Unlike traditional fighters or large UAVs like the MQ-9 Reaper—which rely on well-established turboprop or turbofan designs—emerging classes such as CCAs and attritable drones require engines with unique performance envelopes:
- High thrust-to-weight ratio for maneuverability
- Low cost per unit for expendability
- Modular design for rapid integration into new airframes
- Fuel efficiency across varying mission profiles
This combination of requirements has exposed a capability gap. According to Air Force Research Laboratory (AFRL) officials cited by Air & Space Forces Magazine (May 2024), there is currently “no ideal engine” on the market that meets all these needs. As a result, OEMs are either adapting legacy military engines or turning to commercial off-the-shelf (COTS) designs—neither of which fully satisfies operational demands.
Defense Primes Push Adaptive Cycle Engines for CCA-Class Platforms
The U.S. Air Force’s Collaborative Combat Aircraft program—a key pillar of its Next Generation Air Dominance (NGAD) family—is driving much of this innovation. CCAs are envisioned as autonomous or semi-autonomous wingmen that fly alongside crewed fighters like the F-35 or NGAD sixth-gen platforms. To be viable in contested airspace, they must be fast, agile, and survivable—placing significant demands on their propulsion systems.
Enter adaptive cycle engines. Developed under AFRL’s Adaptive Engine Transition Program (AETP), these next-gen turbines can switch between high-thrust and high-efficiency modes mid-flight. GE Aerospace’s XA100 and Pratt & Whitney’s XA101 are leading contenders here. While initially designed for manned fighters like the F-35A Block 4 upgrade path (now delayed), these engines—or scaled variants—are being eyed for future CCAs.
“Adaptive cycle tech offers an ideal compromise between range and performance,” said a propulsion engineer familiar with AETP developments. “The challenge is miniaturizing it without losing those benefits.” Both GE and Pratt have hinted at derivative versions optimized for smaller platforms but have not disclosed firm timelines.
COTS Engines Fill Gaps—for Now—but Limit Performance
In parallel with advanced R&D efforts, several drone manufacturers are relying on modified commercial turbine engines to meet urgent needs. German firm JetCat offers small gas turbines originally developed for model aircraft but now adapted for military UAVs such as Kratos’ XQ-58A Valkyrie testbeds.
The U.S.-based AMT-PulseJet and PBS Aerospace also supply micro-turbines used in loitering munitions and tactical drones across NATO-aligned forces. These systems offer rapid availability but often lack the durability or thermal tolerance required for sustained high-speed operations in contested environments.
“COTS gets you flying quickly,” noted one AFRL official at Wright-Patterson AFB. “But it doesn’t scale well when you need stealthy inlet shaping or variable-cycle performance.” As drone missions evolve from ISR-only to multi-role strike/suppression tasks under JADC2 frameworks, propulsion limitations may become mission-critical vulnerabilities.
A Growing Ecosystem of Startups Targets Niche Propulsion Needs
The propulsion gap has created fertile ground for startups aiming to disrupt legacy aerospace incumbents. Companies like Ursa Major Technologies (CO), Turbotech (France), Wave Engine Corp (NY), and Hermeus Corp have attracted both venture capital and DoD contracts by focusing on high-performance small turbine or hybrid-cycle engines tailored specifically for UAVs.
- Ursa Major’s Draper engine: A liquid-fueled rocket engine targeting hypersonic test vehicles like Stratolaunch Talon-A
- Turbotech TP-R90: A regenerative turbine offering up to 90 kW output with integrated heat recovery system—ideal for long-endurance drones
- Wave Engine Corp: Exploring pulsejet-derived propulsion with no moving parts—potentially low-cost solutions for swarm-class UAVs
This diversification reflects a broader shift toward mission-specific powerplants rather than one-size-fits-all solutions—a trend echoed by DARPA’s Gambit program which seeks modular drone architectures including plug-and-play engine bays.
Sustainment Challenges Loom as Fleet Size Grows
The proliferation of drone types—from Group 1 quadcopters to Group 5 HALE platforms—has created logistical headaches around maintenance training, spare parts inventories, and depot-level repair capabilities specific to each engine type.
This concern is particularly acute with attritable systems designed around low-cost but short-lifespan components. If such drones are fielded at scale—as envisioned under programs like Replicator—they could overwhelm existing sustainment infrastructure unless modularity and commonality are baked into engine design from day one.
The U.S. Department of Defense has acknowledged this risk; Deputy Secretary Kathleen Hicks emphasized during her August 2023 Replicator rollout that “scalability includes sustainment.” Several OEMs now offer digital twin support tools or predictive maintenance algorithms embedded within their engine control units—a nod toward lifecycle-aware design even in expendable platforms.
The Strategic Implications: Propulsion as a Force Multiplier
If autonomy is the brain of next-gen combat aviation—and sensors its eyes—then propulsion is undoubtedly its beating heart. The ability to field fast-adapting swarms of intelligent aircraft hinges not only on AI algorithms but also on whether those airframes can fly far enough, fast enough—and affordably enough—to matter tactically.
This makes small-engine development not merely a technical challenge but a strategic imperative across NATO-aligned defense ecosystems facing near-peer threats from China or Russia. Whether through adaptive cycle breakthroughs or clever reuse of COTS hardware with smart upgrades—the race is on to ensure tomorrow’s drones aren’t grounded by yesterday’s turbines.
Outlook: Modular Powerplants Will Define Future Drone Design Philosophy
A clear trend emerging from current programs is modularity—not just in payloads but also in powerplants themselves. AFRL’s Open Mission Systems architecture may soon extend beyond avionics into plug-and-play propulsion modules where operators can swap between endurance-optimized versus thrust-maximized configurations based on mission profiles.
This vision aligns with broader shifts toward containerized logistics support models seen in Ukraine conflict zones where rapid field replacement trumps depot-level overhaul cycles—a philosophy increasingly mirrored in Western force planning documents post-AUKUS/Ukraine lessons learned cycles.
