LAS
The Launch Assist System (LAS) is the core water-based thermal propulsion technology behind EcoRocket’s first and second stages
Conventional orbital rockets rely on polluting, highly explosive, corrosive, and toxic chemical propellants. At liftoff, a single heavy launch vehicle can release atmospheric pollutants equivalent to nearly one million combustion vehicles operating simultaneously.
To solve this, ArcaSpace developed a clean, water-based thermal rocket booster. By utilizing hot water as a safe, eco-friendly propellant, LAS enables a 25–50% reduction in chemical propellant consumption or boosts payload capacity by up to 30% with zero emissions during the initial ascent phase.
Operating Principle & Thermal Cycles
The LAS propulsion system operates through a high-efficiency electrical thermal cycle:
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Primary Heating: The composite propellant tank is loaded with a blend of 98% water and benign phase-destabilizing agents. The water is electrically heated onboard to 250°C (482°F). Because the heated water generates its own internal vapor pressure, external high-pressure helium bottles, turbopumps, and complex pressurization valves are completely eliminated. For example, at 200°C, the internal vapor pressure naturally maintains a stable 16 bar.
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Phase Transformation & Injection: When injected into the engine manifold, the superheated water partially flashes into high-pressure vapor.
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Secondary Phase Heating (Reusable Variant): In the reusable version, high-discharge Lithium-Polymer (LiPo) batteries power a second-stage heating grid directly inside the engine chamber. These are derived from the high-power battery technology engineered by ArcaSpace for the 700kW ArcaBoard. At 21 MW for the LAS 25R engine, the instantaneous power output exceeds that of a small nuclear reactor.
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Expansion & Thrust: The superheated steam expands through the nozzle at supersonic velocities to produce thrust. Following flight recovery, onboard battery arrays can be fully recharged using solar or wind power for zero-emission operations.
Technical Innovation: High Thrust-to-Weight vs. Specific Impulse
Initial engineering assessments raised a fundamental question: How can a propulsion system with a specific impulse (Isp) of 50–60 seconds contribute effectively to orbital launches when traditional chemical engines deliver four times higher impulse?
The answer lies in lessons learned from orbital heavy-lifters like the Space Shuttle and Ariane 5 Solid Rocket Boosters (SRBs):
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Thrust-to-Weight Primacy: For atmospheric launch assist and first-stage acceleration, Thrust-to-Weight Ratio (T/W) is the dominant performance factor, while specific impulse is secondary.
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Ascent Acceleration: As long as the booster's T/W exceeds that of the primary stage, it delivers immediate kinetic energy and rapid acceleration through the densest atmospheric layers.
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Operational Envelope: Designed to transport orbital launch vehicles to altitudes of approximately 3,000 m (10,000 ft) and speeds near Mach 2 (in a single stage configuration), LAS significantly reduces gravity losses for the core orbital stage.
Engine Variants: Bell-Nozzle vs. Toroidal Aerospike
LAS technology was engineered in two distinct engine configurations:
1. Expendable Version (Bell-Shaped Nozzle)
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Designed for low-cost, high-volume manufacturing as strap-on boosters for third-party launch vehicles.
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Features a simplified single-phase thermal cycle (tank heating only) to minimize unit production cost.
2. Reusable Version (Toroidal Aerospike)
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Built exclusively for ArcaSpace vehicles and premium integration partners.
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Incorporates a composite toroidal aerospike nozzle and a secondary LiPo-powered heating system inside the engine chamber for maximum expansion efficiency across varying atmospheric pressures.
Direct Comparative Testing
ArcaSpace conducted head-to-head ground test firings comparing both engine geometries on the same test stand using identical propellant tanks, feed architectures, and sensor suites.
Key Test Result: Initial hot-fire data confirmed that the toroidal aerospike configuration yielded a 15% increase in specific impulse over the conventional bell nozzle using superheated water propellant, with further efficiency gains projected at higher operating chamber pressures.
High-Temperature Composite Manufacturing
The entire LAS airframe and propellant tank structure is manufactured from advanced composite materials.
To overcome the thermal limits of standard aerospace resins at 250°C, ArcaSpace engineered a dual-layer composite tank architecture:
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Internal Thermal Liner: Acts as a high-performance insulator, protecting the structural layers and maintaining external wall temperatures below 140°C.
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Structural Filament Overwrap: Glass fiber fabric wound with specialized high-temperature epoxy resins to withstand internal operating pressures.
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Geometry Optimization: Expendable variants utilize high length-to-diameter aspect ratios for aerodynamic efficiency, while reusable variants feature a wider base and lower center of gravity to optimize landing stability and accommodate the aerospike engine.
Integration with EcoRocket
In November 2020, ArcaSpace introduced EcoRocket, an orbital launch vehicle utilizing Launch Assist System technology for its fully reusable first and second stages.
The toroidal aerospike water propulsion system integrated on the EcoRocket Second Stage completed its inaugural flight test campaign at the end of 2021 during Mission 10D.
Submerged LAS Type Rocket Engine Launch (Mission 13):
During Mission 13, a bell-nozzle Launch Assist System (LAS) rocket engine was successfully test-launched from an underwater position, validating the sea-launch, submerged start capability for the EcoRocket platform.
