HyPrSpace, a Bordeaux-based aerospace company, is developing hybrid rocket propulsion technology for small satellite launches through its Baguette One demonstrator program (Editors Note: We did fact check the name – honest). The company has completed preliminary design reviews for both its suborbital Baguette One rocket and the larger Orbital Baguette One (OB-1) micro-launcher, entering the critical design phase where detailed engineering plans are finalised.
Founded in 2019, HyPrSpace secured €35 million in funding through France’s development initiative, with 60 per cent provided by the Government and the remainder from consortium partners, including Telespazio and CT Ingénierie. The funding supports the PADA1 project, which aims to complete detailed design work and conduct the first suborbital flight.
The company has signed an agreement with France’s Direction Générale de l’Armement (DGA) to launch the Baguette One demonstrator from a missile testing site in mainland France. If successful, this would mark the first rocket launch from metropolitan France, with the flight currently scheduled for 2026.
HyPrSpace’s hybrid propulsion system combines liquid oxidiser with solid fuel, specifically recycled high-density polyethene. This approach eliminates the need for turbopumps, which are costly components in conventional liquid rocket engines that pressurise propellants before injecting them into the combustion chamber.
“Solid is cheap and simple to use, but pyrotechnical, and you can’t modulate thrust,” explained Sylvain Bataillard, HyPrSpace’s co-founder and chief strategy officer. “At the opposite end, you’ve got liquid propulsion, with which you can modulate thrust-it’s really effective. However, it’s extremely complicated due to turbo pumps, and it’s extremely expensive.”
The hybrid system offers throttling capability while maintaining simplicity in its design. The 10-meter Baguette One demonstrator is designed to carry payloads of up to 300 kg, while the larger OB-1 rocket, standing 17 meters tall, targets payloads of 250 kilograms to low Earth orbit.
Cost projections suggest that the technology could deliver launches at approximately €20,000 per kilogram, positioning it between traditional heavy-lift launchers (under $10,000/kg) and current micro-launchers ($40,000-$ 50,000/kg).
Engineering Deep Dive: Hybrid Propulsion Systems
Hybrid rocket engines represent a middle ground between solid and liquid propulsion systems, combining aspects of both technologies to address specific engineering challenges in small-scale launch vehicles.
Combustion Chamber Architecture
Traditional hybrid rockets face a fundamental scaling problem: as engine size increases, the fuel mixing becomes less efficient and combustion stability decreases. This occurs because the oxidiser injection pattern and fuel regression rate become mismatched in larger combustion chambers.
HyPrSpace’s solution involves a toroidal (doughnut-shaped) combustion chamber that surrounds a cylindrical oxidiser tank. The chamber walls are lined with solid fuel blocks, creating a thin annular combustion zone. Liquid oxidiser is injected into the space between the fuel walls, ensuring the flame remains close to the fuel surface, regardless of the engine’s scale.
This geometry addresses the mixing problem by maintaining a consistent oxidiser-to-fuel ratio across the combustion surface. The thin combustion chamber ensures rapid heat transfer to the solid fuel, promoting efficient fuel regression and vaporisation.
Fuel Regression Mechanics
In hybrid systems, the solid fuel burns from the surface inward, creating a regression rate that determines thrust characteristics. The regression rate depends on the mass flux of oxidiser over the fuel surface and the heat feedback from the flame zone.
The equation governing classical fuel regression is: r = a(G_ox)^n
Where r is the regression rate, G_ox is the oxidiser mass flux, and a ‘ and ‘n’ are fuel-dependent constants. HyPrSpace’s architecture maintains optimal G_ox distribution by controlling the gap width between fuel blocks, ensuring consistent regression across the entire fuel surface.
Propellant Selection and Performance
The company utilises recycled high-density polyethene (HDPE) as a solid fuel, paired with a liquid oxidiser. HDPE offers several advantages:
- High density: Approximately 0.95 g/cm³, providing good volumetric performance
- Clean combustion: Produces primarily CO₂ and H₂O with minimal toxic byproducts
- Mechanical properties: Sufficient structural strength to serve as combustion chamber walls
- Cost effectiveness: Readily available as recycled material
The liquid oxidiser (likely liquid oxygen or nitrous oxide, although HyPrSpace hasn’t specified) is stored at moderate pressures, eliminating the need for high-pressure turbopumps typically used in liquid engines.
Thrust Modulation and Control
Unlike solid rockets, hybrid systems can throttle by controlling oxidiser flow rate. The solid fuel cannot burn without an oxidiser, providing inherent safety and restart capability. This allows:
- Variable thrust profiles: Optimising trajectory for specific missions
- Engine shutdown: Stopping combustion by closing oxidiser valves
- Restart capability: Multiple ignitions during flight if required
System Integration Challenges
Hybrid propulsion systems must address several engineering challenges:
Oxidiser injection uniformity: Ensuring even distribution across the fuel surface to prevent hot spots and uneven regression.
Combustion stability: Maintaining steady burning without pressure oscillations that could damage the vehicle structure.
Nozzle design: Optimising expansion ratio for the specific mixture ratio and combustion products.
Thermal management: Protecting the oxidiser tank from the heat of the combustion chamber while maintaining the proper fuel temperature for efficient regression.
HyPrSpace’s toroidal chamber design addresses these challenges by providing mechanical control over the combustion process geometry, reducing sensitivity to manufacturing tolerances and operating conditions.
Hybrid rockets typically achieve specific impulse values between solid and liquid systems:
- Solid propellants: 200-280 seconds
- Hybrid systems: 250-320 seconds
- Liquid propellants: 300-450 seconds
While hybrid systems don’t match the performance of liquid engines, they offer significant advantages in terms of complexity, cost, and safety for small launch vehicles, where absolute performance is less critical than operational factors.
HyPrSpace has conducted three static fire test campaigns of its hybrid propulsion system at the DGA Essais de Missiles facility in Saint-Médard-en-Jalles, Gironde, between 2024 and 2025. These tests validated the combustion chamber architecture and confirmed thrust modulation capabilities.
The testing program focused on demonstrating stable combustion across different throttle settings and validating the fuel regression patterns predicted by the company’s modelling. The cylindrical oxidiser tank surrounded by the toroidal combustion chamber showed consistent performance characteristics during the test series.
Static testing has eliminated one of the traditional barriers to scaling hybrid propulsion. By maintaining mechanical control over the flame-to-fuel distance through the toroidal geometry, the system demonstrated stable operation regardless of variations in chamber size.
The micro-launcher market is expanding rapidly, with industry consultancy Novaspace estimating that more than 26,000 satellites will launch by 2032. This represents approximately eight satellites per day, creating demand for dedicated small payload launch services.
Current market dynamics indicate that SpaceX controls approximately two-thirds of operational satellites, according to satellite tracker CelesTrak. However, the micro-launcher segment addresses different mission requirements than ample rideshare opportunities, offering dedicated orbits and launch scheduling flexibility.
If HyPrSpace’s technology proves successful, the hybrid propulsion approach could provide European access to this growing market. The company’s turbopump-free design aims to reduce manufacturing costs and simplify ground operations compared to conventional liquid-fueled micro-launchers.
The first Baguette One flight will serve as a technology demonstrator, validating the performance of the hybrid propulsion system in flight conditions. Success would position the company for OB-1 development and potential commercial operations in the European micro-launcher market.
TLDR:
- French startup HyPrSpace develops hybrid rocket propulsion using liquid oxidiser and solid plastic fuel
- Turbopump-free design aims to reduce launch costs to €20,000/kg for small satellites
- Toroidal combustion chamber architecture addresses traditional hybrid scaling problems
- Company secured €35 million funding and completed preliminary design reviews
- Baguette One demonstrator scheduled for 2026 launch from mainland France
- Technology targets growing micro-launcher market with 26,000+ satellites planned by 2032
