This paper presents a novel layout for a low-cost, tactical one-way Unmanned Aerial Vehicle (UAV) that eliminates all moving parts from its propulsion and aerodynamic control cycles. By utilizing the phase-change expansion of chilled Liquefied Petroleum Gas (LPG) within a front-mounted induction centerbody, the design achieves static thrust generation without a mechanical compressor or a traditional variable-geometry intake. The integration of a co-molded 1.5-meter acoustic-stealth duct and wing-embedded payloads results in a highly scalable, low-observable platform optimized for decentralized Local Manufacturing Systems (LMS).
1. Thermodynamic and Propulsion Architecture
Traditional ramjet architectures require high forward velocities to achieve the compression ratios necessary for self-sustaining combustion. The system detailed here replaces mechanical or ram-air compression with thermodynamic mass entrainment driven by cryogenic fuel expansion.
1.1. Front-Mounted Induction Ejector (FMIE)
The propulsion core consists of a monolithic, centerbody mounted forward of the main duct entrance. The tip houses a high-pressure pre-burner fed by subcooled LPG (stored at -20°C).
Upon localized initialization, the expanded fuel-air mixture exits through a rearward-facing circumferential radial slot around the shoulder of the nose cone. This supersonic sheet utilizes the Coanda effect to skim the centerbody skin, creating a severe localized drop in static pressure at the front intake lip. By ducting incoming ambient air over the cryogenic feed lines, a localized density spike is induced, maximizing the mass flow rate of oxygen entering the induction loop prior to forward vehicle movement.
1.2. Pre-Mixed Carburetion and Tesla Valves
The primary LPG jet is calibrated to achieve a fuel-rich or near-stoichiometric mass entrainment ratio (15.6:1). To eliminate the risk of flash-back or thermal propagation into the intake manifold, a multi-stage Tesla valve array is integrated directly into the internal induction channels of the centerbody.
The fluidic diode configuration allows the forward fuel-air stream to pass with minimal pressure drop, while forcing reverse-traveling combustion shockwaves into self-colliding eddies, quenching the flame front geometrically without mechanical flap valves.
2. Zero-Moving-Parts Launch Dynamics
Unlike traditional ramjets that require an external mechanical catapult or rocket booster to achieve takeoff velocity, this architecture generates autonomous static thrust through internal fluidic induction.
Static Thrust Initialization: While stationary on the launch rail, the nose-cone pre-burner ignites. The supersonic LPG jet sheet sheets out of the radial Coanda slots, violently evacuating the air inside the 1.5-meter duct. This creates an immediate intake vacuum that draws in and compresses ambient air before the vehicle moves.
The Low-Friction Ramp: Because the engine generates its own net static thrust immediately, it requires only a completely passive, unpowered 3-to-5 meter angled rail lined with an ultra-low-friction polymer.
The Launch Shoe: To protect the thin-walled, bottom-mounted chilled LPG tank, the drone rests on a lightweight, matching composite launch shoe that grips the rigid wing-root junctions.
Release and Separation: Once the internal pressure loop stabilizes and thrust exceeds the static airframe weight plus sliding friction, the drone releases autonomously. It slides down the passive rail under its own power, transitions smoothly into free flight, and the launch shoe jettisons naturally via aerodynamic drag.
3. Structural and Structural-Acoustic Integration
The fuselage consists of a passive, hollow 1.5-meter outer duct. The interior volume acts purely as a mixing and diffusion channel, eliminating the need for a necked-down combustion exit nozzle on the centerbody core.
3.1. Dual-Purpose Helmholtz Acoustic and Radar Liner
The exhaust profile exhibits a distinct acoustic frequency dictated by the pneumatic pulse rate of the fluidic loop. The interior of the 1.5-meter duct is co-molded with a perforated face sheet backed by variable-depth internal cavities.
Acoustic Attenuation: The cavities act as Helmholtz resonators tuned to the dominant pulse frequency, forcing out-of-phase wave reflections that achieve destructive interference, damping the exhaust signature into a low-intensity hiss.
Electromagnetic Trapping: The internal cavity partitions are molded as non-uniform geometric wedges loaded with graphene nanoplatelets. Incident low-altitude radar waves entering the open duct are scattered internally within the sub-structure, converting RF energy into thermal dissipation and lowering the static Radar Cross Section (RCS) to < 0.01 m².
3.2. Spanwise Mass Distribution
To preserve the aerodynamic cleanliness of the central duct, the ammunition payload is embedded directly within the leading edges of the short-span, high-aspect biplane wings. Spreading the dead-weight across the lifting surfaces minimizes root bending moments, allowing for a highly optimized, thin-walled composite wing bracket structure. The layout utilizes either Linear Shaped-Charges (LSC) or directional fragmentation matrices, optimizing the terminal effect for spatial probability rather than single-point penetration.
4. Comparative Defense-Penetration Metrics
Evaluating this fluidic flying-tube architecture against traditional loitering munitions highlights a fundamental divergence in survivability and signature management. Standard long-range tactical UAVs rely on internal combustion piston engines or commercial electric motors driving external propellers. These propulsion systems create high-frequency micro-Doppler radar reflections, significant acoustic profiles, and concentrated thermal points from exposed exhaust cylinders. Furthermore, their reliance on extensive digital wiring harnesses and electronic fuel injection blocks makes them highly susceptible to high-power microwave weapons and directional radio-frequency jamming.
In contrast, the fluidic ejector-ramjet architecture eliminates these exploit vectors entirely. By conducting all compression and mixing fluidically within the boundaries of a 1.5-meter outer duct, the platform exhibits zero external rotating components. This completely neutralizes the micro-Doppler spectral signature that modern low-altitude air defense radars utilize to differentiate unmanned aircraft from background clutter or biological entities.
Acoustically, the integrated Helmholtz cavity matrix inside the molded duct dampens the pulsed exhaust frequency via destructive phase interference, preventing ground-based acoustic tracking networks from locking onto a clean engine tone. Thermally, the underbelly-mounted cryogenic LPG tank acts as a localized cold-shield, physically masking the internal combustion core from ground-based long-wave infrared tracking sensors looking upward. The massive influx of ambient bypass air mixed inside the 1.5-meter channel rapidly dilutes the exhaust plume before it exits the rear linear aerospike, reducing the radiant thermal track to near-ambient levels.
Finally, because the pre-mixed carburetion loop is governed entirely by structural geometry and fluid dynamics rather than electronic injectors or electronic speed controllers, the vehicle's propulsion cycle is fundamentally immune to electromagnetic interference and tactical electronic warfare assets.
5. LMS Feasibility and Production Economics
The primary engineering asset of this architecture is the complete decoupling of performance from high-precision machining tolerances.
Because there are no high-speed rotating components or friction surfaces, the entire centerbody can be printed via standard polymer additive manufacturing and converted to a monolithic metal component via lost-wax casting. The 1.5-meter duct requires only two-part split-mandrel composite tooling.
This layout allows a 220 km range tactical platform to be manufactured within decentralized local workshops, bypassing traditional aerospace supply chain bottlenecks while delivering absolute acoustic, thermal, and micro-Doppler signature suppression.
No comments :
Post a Comment