European Launcher Challenge: Detailed Specifications for All Launch Vehicles Selected

Key Takeaways

• New European rockets prioritize cost efficiency and flexibility over pure lift capacity
• Competition drives diverse propulsion choices like methalox, bio-propane, and hybrids
• Commercial providers seek autonomy from legacy institutional systems through vertical integration

Introduction

The landscape of space access in Europe is undergoing a fundamental shift. For decades, the continent relied on a consolidated institutional model, primarily centered around the Ariane and Vega families. This paradigm ensured independent access to space but faced increasing pressure from agile commercial competitors abroad. In response, the European Space Agency (ESA) and various national bodies initiated a shift toward a competitive service-oriented procurement model. This initiative, often referred to as the European launcher challenge, invites commercial entities to develop independent launch systems.

These vehicles are not mere paper concepts. Hardware is being manufactured, tested on test stands, and prepared for orbital flights. The technical specifications of these rockets reveal a divergence in engineering philosophy, utilizing different propellants, structural materials, and recovery strategies. This article examines the detailed technical makeup of the primary contenders in this new European space race.

The Engineering Context of the Challenge

The European launcher challenge operates on a premise distinct from previous ESA programs. The agency acts as a customer rather than a primary architect. This allows private companies to optimize their designs for market needs rather than purely institutional requirements. The vehicles emerging from this process generally fall into the micro-launcher to mini-launcher class, with payload capacities ranging from 150 kilograms to 1,500 kilograms to Low Earth Orbit (LEO).

Design choices in this sector are driven by specific physics and economic constraints. Engineers must balance specific impulse (engine efficiency) with density impulse (propellant storage volume), manufacturing complexity, and supply chain availability. The following sections analyze the specific launch vehicles that define this competitive field.

Isar Aerospace – Spectrum

Isar Aerospace operates out of Munich, Germany. The company focuses on a vehicle named Spectrum, which is designed to serve the small satellite constellation market. Spectrum distinguishes itself through a high payload capacity relative to its competitors in the micro-launcher class and a heavy reliance on vertical integration and automated manufacturing.

Spectrum Vehicle Architecture

Spectrum is a two-stage launch vehicle. The design philosophy centers on maximizing payload volume and mass to orbit while maintaining a diameter that fits within standard logistics chains.

• Total Height: 28 meters
• Diameter: 2 meters
• Payload to LEO: 1,000 kilograms
• Payload to SSO: 700 kilograms

The structural system utilizes carbon fiber composite materials. Carbon fiber reinforced polymer (CFRP) offers a high strength-to-weight ratio, which allows for lighter tank structures compared to traditional aluminum-lithium alloys. This mass saving in the structure translates directly to increased payload capability. The tanks are linerless, meaning the carbon composite itself holds the cryogenic propellants, a technically challenging feat that reduces weight further by eliminating the need for a metal or polymer liner.

Propulsion System: The Aquila Engine

The core of the Spectrum vehicle is the Aquila engine. Isar Aerospace utilizes a cluster of engines on the first stage and a single vacuum-optimized engine on the second stage.

• First Stage Configuration: 9 x Aquila engines
• Second Stage Configuration: 1 x Aquila Vacuum engine
• Propellant: Propane and Liquid Oxygen (LOX)

The choice of propane as a fuel is significant. Propane (C3H8) offers a higher density than methane, allowing for smaller tank volumes for the same mass of propellant, while burning cleaner than RP-1 (refined kerosene). Clean combustion is vital for engine reusability and minimizes soot accumulation in the turbomachinery. The engines operate on a gas-generator cycle. While slightly less efficient than staged combustion, the gas-generator cycle reduces plumbing complexity and development risk.

The Aquila engines are manufactured using extensive 3D printing (additive manufacturing). This allows for complex internal cooling channels to be printed directly into the combustion chamber wall, optimizing thermal management without the need for brazing hundreds of separate cooling tubes.

Launch Operations

Isar Aerospace has secured launch infrastructure at the Andøya Spaceport in Norway. The location at high latitude is advantageous for reaching Sun-Synchronous Orbit (SSO) and Polar Orbits, which are the primary destinations for Earth observation constellations. The vehicle is transported in standard shipping containers, minimizing specialized ground handling equipment.

Rocket Factory Augsburg – RFA One

Rocket Factory Augsburg (RFA), based in Augsburg, Germany, approaches the launcher challenge with a philosophy derived from the automotive industry. RFA One is designed to be a high-volume, low-cost launcher, utilizing serial production techniques to drive down the price per kilogram to orbit.

RFA One Vehicle Architecture

RFA One is a three-stage rocket, a configuration that differs from the two-stage standard of many small launchers. The three-stage design allows each stage to be optimized for a specific portion of the flight regime, potentially increasing overall efficiency at the cost of added complexity in separation events.

• Total Height: 30 meters
• Diameter: 2 meters
• Payload to LEO: 1,300 kilograms
• Payload to SSO: 850 kilograms

The vehicle structure employs stainless steel for its tanks. While heavier than carbon composites, stainless steel is significantly cheaper and more robust. It handles cryogenic temperatures well and requires less specialized manufacturing environments than composites. This choice reflects the company’s focus on cost reduction over pure mass optimization.

Propulsion System: The Helix Engine

RFA employs the Helix engine, which utilizes a staged combustion cycle. This is a sophisticated engine cycle rarely seen in small commercial launchers due to its complexity. In staged combustion, the propellant used to drive the turbine is not dumped overboard but is injected into the main combustion chamber.

• First Stage Configuration: 9 x Helix engines
• Second Stage Configuration: 1 x Helix Vacuum engine
• Third Stage (Orbital Stage): Fenix engine (Hypergolic or specialized propulsion)
• Propellant: RP-1 (Kerosene) and Liquid Oxygen (LOX)
• Engine Cycle: Oxygen-rich Staged Combustion

The oxygen-rich staged combustion cycle provides higher specific impulse (efficiency) than gas-generator cycles. This efficiency helps offset the heavier stainless steel structure. The use of RP-1 and LOX is a standard, well-understood combination, ensuring a reliable supply chain for propellants.

Orbital Stage Versatility

The third stage of the RFA One acts as an orbital transfer vehicle. It can perform precise maneuvers to deploy payloads into distinct orbits. This capability is particularly relevant for rideshare missions where different customers may require separation at different altitudes or inclinations.

MaiaSpace – Maia

MaiaSpace is a subsidiary of ArianeGroup. This relationship provides MaiaSpace with access to established industrial capabilities and legacy technology, specifically the Themis reusable booster demonstrator and the Prometheus engine program. The Maia launcher is designed from the outset with reusability as a core requirement.

Maia Vehicle Architecture

Maia serves the mini-launcher segment but is designed to be scalable. The architecture is modular, allowing for different configurations depending on mission requirements and whether the first stage is being recovered.

• Payload to LEO (Expendable): 1,500 kilograms
• Payload to LEO (Reusable): 500 kilograms
• Propellant: Liquid Methane and Liquid Oxygen (Methalox)

The vehicle structure borrows heavily from the technological maturation done for the Themis program. Methane is the fuel of choice for reusable rockets because it burns clean, leaving minimal residue in the engines, and has a boiling point closer to oxygen than kerosene, which simplifies thermal insulation between tanks (common bulkhead design).

Propulsion System: Prometheus

The Prometheus engine powers the Maia vehicle. This engine was developed by ESA and ArianeGroup as a low-cost, reusable successor to the Vulcain family.

• Engine Type: Gas-generator cycle (optimized for cost)
• Propellant: Methalox
• Thrust: Variable/Throttlable

Throttling capability is essential for the landing phase of a reusable rocket. The engine must reduce thrust significantly as the vehicle consumes fuel and becomes lighter, ensuring a soft touchdown. Prometheus features extensive use of additive manufacturing to reduce part count and production time.

The Colibri Kick Stage

To maximize mission flexibility, MaiaSpace includes a kick stage named Colibri. While the main stages handle the heavy lifting to orbit, Colibri provides the final orbital insertion and circularization. This allows the reusable first stage to separate earlier and at lower velocities, easing the thermal protection requirements for reentry.

PLD Space – Miura 5

PLD Space, based in Spain, recently achieved a milestone with the launch of their suborbital demonstrator, Miura 1. The data and experience gathered from that program are directly applied to their orbital vehicle, Miura 5.

Miura 5 Vehicle Architecture

Miura 5 is an orbital micro-launcher designed to launch small satellites from the Guiana Space Centre. Like Maia, it incorporates reusability into its design concept, intending to recover the first stage via a splashdown in the ocean rather than a propulsive landing on a barge or pad.

• Total Height: 34 meters
• Diameter: 2 meters
• Payload to LEO: ~900 kilograms (Equatorial)
• Payload to SSO: 540 kilograms

The recovery strategy involves parachutes to slow the first stage before it impacts the water. This method saves the fuel mass required for a propulsive landing but introduces the challenge of salt water refurbishment.

Propulsion System: TEPREL-C

The engines powering Miura 5 are the TEPREL-C engines. These are an evolution of the TEPREL-B used on Miura 1.

• First Stage Configuration: 5 x TEPREL-C engines
• Second Stage Configuration: 1 x TEPREL-C Vacuum engine
• Propellant: Bio-Kerosene (Jet A-1) and Liquid Oxygen

The engine uses an open cycle (gas generator). PLD Space designs and manufactures these engines in-house. The use of bio-kerosene aligns with wider European goals for sustainability, though the primary performance characteristics mimic standard RP-1.

Launch Site and Operations

PLD Space operates from the Guiana Space Centre (CSG) in French Guiana. This provides a significant geographic advantage. Launching from near the equator allows the vehicle to leverage the Earth’s rotation, granting an extra velocity boost for equatorial orbits compared to launch sites in northern Europe.

Orbex – Prime

Orbex is a UK-based company operating out of Scotland and Denmark. While the UK is no longer in the EU, it remains a member state of ESA, making Orbex a relevant participant in the broader European launcher ecosystem. The Prime rocket focuses heavily on environmental sustainability and carbon footprint reduction.

Prime Vehicle Architecture

Prime is a smaller vehicle compared to RFA One or Spectrum, targeting the dedicated nano-sat launch market. Its architecture is optimized for efficiency and minimal environmental impact.

• Total Height: 19 meters
• Diameter: 1.3 meters
• Payload to SSO: 150 – 200 kilograms

The fuselage is constructed from carbon fiber and aluminum composites. A unique feature of the Prime architecture is the absence of explosive bolts for stage separation. Orbex utilizes a “zero-shock” staging mechanism, which protects sensitive payloads from the high-frequency vibrations typically associated with pyrotechnic separation events.

Propulsion System: 3D Printed Engines

Orbex uses a 3D-printed engine that burns bio-propane.

• First Stage Configuration: 6 x Coaxial engines
• Second Stage Configuration: 1 x Vacuum engine
• Propellant: Bio-Propane and Liquid Oxygen

The bio-propane reduces carbon emissions by roughly 90% compared to fossil-fuel-derived kerosene. The engines are printed as single pieces, eliminating joints and welds that are common failure points.

Sutherland Spaceport

Orbex intends to launch from the Sutherland Spaceport in northern Scotland. This site is dedicated to vertical launch of small rockets into polar and sun-synchronous orbits. The proximity of the factory to the launch site simplifies logistics and reduces transport costs.

HyImpulse – SL1

HyImpulse, a spin-off from the German aerospace center DLR, takes a different technological path by utilizing hybrid propulsion. Their vehicle, SL1, avoids the complexities of complex turbopumps needed for bi-liquid engines.

SL1 Vehicle Architecture

The Small Launcher 1 (SL1) is a three-stage vehicle. The hybrid propulsion technology allows for a simpler, safer, and potentially cheaper vehicle design.

• Total Height: 32 meters
• Payload to LEO: 600 kilograms
• Payload to SSO: 500 kilograms

Propulsion System: Hybrid Motors

Hybrid rockets use a solid fuel grain and a liquid oxidizer. HyImpulse uses paraffin wax (candle wax) as the fuel and Liquid Oxygen as the oxidizer.

• Propellant: Paraffin Wax (Solid) + Liquid Oxygen
• Mechanism: Electric pumps or pressure-fed systems

Paraffin wax has a high regression rate, meaning it burns fast enough to generate the high thrust levels required for launch, a historical problem for other hybrid fuel types like rubber. The system is safe to handle because the fuel is inert until the oxidizer is introduced. This eliminates many of the explosive handling safety requirements on the ground, streamlining operations.

Latitude – Zephyr

Latitude, a French startup based in Reims, is developing the Zephyr launcher. Zephyr targets the lower end of the payload spectrum, focusing on dedicated launches for nano-satellites that would otherwise fly as secondary payloads on larger rockets.

Zephyr Vehicle Architecture

Zephyr is a compact vehicle designed for high cadence and rapid manufacturing.

• Total Height: 17 meters
• Payload to SSO: 100 kilograms (initially), targeting up to 200 kilograms in future iterations.

The small size allows for simplified transport and integration. The vehicle is designed to be responsive, meaning it can be readied for flight in a short window to meet urgent customer demands.

Propulsion System: Navier Engine

The Navier engine powers the Zephyr.

• Propellant: RP-1 (Kerosene) and Liquid Oxygen
• Engine Technology: 3D Printed, electric-pump fed (battery powered pumps).

Using electric pumps (e-pumps) instead of turbopumps simplifies the engine significantly. Turbopumps require a gas generator or pre-burner and complex turbine machinery operating at high temperatures. Electric pumps, powered by high-discharge batteries, are mechanically simpler and easier to control, though the battery mass penalizes performance for larger vehicles. For a vehicle the size of Zephyr, the trade-off is favorable.

Comparative Analysis of European Propulsion Strategies

The diversity in the European launcher challenge is most visible in the propulsion choices. No single standard has emerged, indicating a robust exploration of the engineering trade space.

Cryogenic Liquids vs. Hybrids

The majority of contenders (Isar, RFA, Maia, PLD, Latitude) use bi-liquid designs. This technology is mature and offers high performance. However, HyImpulse’s bet on hybrid propulsion offers a compelling alternative. Hybrids are inherently safer; cracks in the solid fuel grain do not lead to catastrophic explosions as they might in solid rocket motors, and the oxidizer flow can be terminated to shut down the engine. The trade-off is often a lower specific impulse and difficulties in maintaining a consistent oxidizer-to-fuel ratio as the solid grain burns away.

Methane and Propane vs. Kerosene

The shift away from Kerosene (RP-1) toward light hydrocarbons like Methane and Propane is evident in the designs of Isar Aerospace, MaiaSpace, and Orbex. Kerosene is energy-dense but produces soot (coking) which complicates reuse. Methane and Propane burn cleanly and have higher specific impulse. Methane is also widely considered the fuel of the future for space exploration (e.g., SpaceX Starship), creating a gravitational pull toward this technology. RFA and PLD Space retaining Kerosene suggests a prioritization of density and proven handling procedures over the theoretical benefits of methalox reusability in the short term, although PLD is using a bio-derived version to meet sustainability goals.

Manufacturing: The Additive Revolution

Almost every participant in the challenge utilizes additive manufacturing (3D printing) for their engines. The traditional method of building rocket engines involved casting, forging, and brazing thousands of distinct parts. 3D printing allows the combustion chamber and nozzle, including the intricate cooling channels within the walls, to be printed as a single unit or very few units. This reduces the “part count” drastically. Lower part counts correlate with higher reliability and lower assembly costs.

Launch Infrastructure and Geography

The specifications of the rockets are intrinsically linked to their launch sites. The European launcher challenge has catalyzed the development of spaceports across the continent.

The Northern Spaceports

Andøya (Norway), Esrange (Sweden), and Sutherland (Scotland) serve as the primary launch pads for Isar, HyImpulse, and Orbex respectively. These high-latitude sites are physically ideal for launching into Polar and Sun-Synchronous orbits. A rocket launched north from these locations flies over open ocean, minimizing safety risks to populated areas. However, launching from high latitudes requires more energy to reach equatorial orbits compared to launching from the equator.

The Guiana Space Centre (CSG)

PLD Space and MaiaSpace leverage the historic European spaceport in French Guiana. Located near the equator, this site provides a significant velocity bonus from the Earth’s rotation (approx. 460 m/s). This allows vehicles like Miura 5 to carry heavier payloads to equatorial orbits than they could from Europe. The infrastructure at CSG is also mature, with established tracking stations, payload processing facilities, and security protocols.

Market Positioning and Service Models

The specifications detailed above serve distinct market strategies. The European launcher challenge is not merely about building a rocket; it is about building a sustainable business case.

The Constellation Deployment Model

Vehicles like RFA One and Spectrum are sized to deploy entire planes of small satellite constellations or serve as heavy-lift options for single large microsatellites. Their payload capacity (around 1,000 kg) hits a “sweet spot” where they can aggregate several commercial payloads, offering a lower price per kilogram than smaller rockets while offering more scheduling control than rideshares on heavy lift vehicles like Falcon 9.

The Dedicated Access Model

Latitude and Orbex target the dedicated launch market. While their price per kilogram is likely higher than larger vehicles, the value proposition is “premium service.” A customer with a specific orbit requirement and a strict timeline may prefer to pay a premium for a dedicated Zephyr or Prime launch rather than waiting for a rideshare slot that might be delayed by the primary customer.

Summary

The European launcher challenge has catalyzed a diversification of European space access capabilities. Moving away from a monolithic reliance on institutional launchers, the continent is fostering an ecosystem of commercial providers. The vehicles – Spectrum, RFA One, Maia, Miura 5, Prime, SL1, and Zephyr – represent different answers to the same question: how to transport payloads to orbit efficiently. From the high-efficiency staged combustion of RFA to the simplified hybrid engines of HyImpulse, and from the carbon composite structures of Isar to the stainless steel of RFA, these specifications reflect a sophisticated industrial base making strategic engineering trade-offs. The coming years will determine which of these technical specifications translates into commercial viability and reliable service.

Appendix: Top 10 Questions Answered in This Article

What is the European launcher challenge?

It refers to the shift in European space policy toward competitive, commercial procurement of launch services, moving away from sole reliance on institutional rockets like Ariane. This initiative encourages private companies to develop independent launch vehicles.

What are the primary differences between Isar Aerospace’s Spectrum and RFA One?

Spectrum uses a carbon composite structure and gas-generator cycle engines fueled by propane. RFA One uses a stainless steel structure and oxygen-rich staged combustion engines fueled by kerosene (RP-1).

Why do some European launchers use propane or methane instead of kerosene?

Propane and methane burn cleaner than kerosene, producing less soot, which is beneficial for engine reusability. They also offer higher specific impulse (efficiency) and simplify tank design due to similar boiling points with liquid oxygen.

Which European commercial launcher is designed to be reusable?

MaiaSpace’s Maia launcher and PLD Space’s Miura 5 are designed with reusability in mind. Maia targets propulsive landing, while Miura 5 targets ocean recovery with parachutes.

What is the advantage of the hybrid propulsion used by HyImpulse?

Hybrid propulsion, using solid paraffin wax and liquid oxygen, is inherently safer than bi-liquid systems because the fuel is inert. It also reduces complexity by eliminating the need for complex turbopumps for the fuel component.

Where will these new European rockets launch from?

Launch sites include Andøya in Norway (Isar Aerospace), Sutherland in Scotland (Orbex), SaxaVord in the UK (RFA), and the Guiana Space Centre in French Guiana (PLD Space, MaiaSpace).

What is the payload capacity of the RFA One rocket?

RFA One is designed to lift approximately 1,300 kilograms to Low Earth Orbit (LEO) and 850 kilograms to Sun-Synchronous Orbit (SSO).

How does Orbex Prime reduce the environmental impact of launches?

Orbex Prime uses bio-propane, a renewable fuel that reduces carbon emissions by roughly 90% compared to fossil fuels. It also features a zero-shock staging mechanism that eliminates orbital debris associated with explosive bolts.

What role does 3D printing play in these new launch vehicles?

Most contenders, including Isar, RFA, and Orbex, use 3D printing (additive manufacturing) to build their engines. This allows for complex internal geometries, such as cooling channels, to be manufactured in a single piece, reducing part count and cost.

What is the “dedicated access” market model?

This model, targeted by smaller launchers like Zephyr and Prime, offers customers precise control over their launch schedule and orbital parameters. It serves clients who cannot afford the delays or orbital compromises associated with sharing a ride on a larger rocket.

Appendix: Top 10 Frequently Searched Questions Answered in This Article

What are the top European space startups?

The leading companies discussed include Isar Aerospace, Rocket Factory Augsburg (RFA), PLD Space, MaiaSpace, Orbex, HyImpulse, and Latitude. Each is developing orbital launch vehicles.

How much payload can the Miura 5 carry?

Miura 5 is designed to carry approximately 540 kilograms to Sun-Synchronous Orbit (SSO) and up to 900 kilograms to equatorial Low Earth Orbit (LEO).

Is the Ariane 6 the only European rocket?

No, Ariane 6 is the heavy-lift institutional launcher, but the European launcher challenge has spawned several commercial competitors like Spectrum and RFA One to serve the small and medium satellite market.

What is the difference between gas generator and staged combustion cycles?

Gas generator cycles dump a small amount of propellant overboard to drive the pumps, sacrificing some efficiency for simplicity. Staged combustion, used by RFA, burns that propellant in the main chamber, offering higher efficiency but higher technical complexity.

Why is launching from French Guiana better than Europe?

French Guiana is near the equator, where the Earth’s rotation speed is fastest. Launching eastward from there gives rockets a significant velocity boost, allowing them to carry more payload than if they launched from higher latitudes in Europe.

What is the status of reusable rockets in Europe?

Reusability is in active development. MaiaSpace is developing the Maia vehicle based on the Themis demonstrator, and PLD Space is working on parachute recovery for Miura 5. Currently, no fully reusable European commercial launcher is operational.

Does Europe have its own SpaceX competitors?

Yes, companies like Isar Aerospace and RFA are often compared to early SpaceX due to their focus on vertical integration, commercial cost structures, and agile development, though they currently target the small-to-medium lift market rather than heavy lift.

What fuel does the Isar Aerospace Spectrum use?

Spectrum uses a propellant combination of Liquid Oxygen (LOX) and Propane. This offers a balance of high density and clean combustion.

How big is the small satellite launch market?

The market is significant and growing, driven by mega-constellations for internet and earth observation. European launchers are designing vehicles with capacities between 150 kg and 1,300 kg specifically to address this demand.

What is the benefit of carbon fiber rockets?

Carbon fiber reinforced polymer (CFRP) is much lighter than metal. Using it for rocket structures, as Isar Aerospace and Orbex do, reduces the vehicle’s dry mass, allowing it to carry heavier payloads to orbit.