The Methalox Engine Race: Qingyu-11, YF-209, Raptor, BE-4, and Why Methane-LOX Won the Reusable Era

Methane-liquid oxygen ('methalox') engines have become the dominant propulsion choice for new reusable launch vehicles globally in 2026. SpaceX's Raptor (Starship/Super Heavy), Blue Origin's BE-4 (New Glenn and ULA's Vulcan Centaur), Landspace's TQ-12 (Zhuque-2 and Zhuque-3), CASC's YF-209 (commercial sale variant tested by Cosmoleap), Cosmoleap's in-development Qingyu-11, and a long list of additional methalox engines now power most credible new reusable launch programs. Cosmoleap's $73 million funding round on April 29, 2026 is the latest in a long sequence of methalox-engine programs receiving major capital, and the moment is right to explain why methalox won the reusable era over the previous-generation kerosene-LOX standard.

Why Methalox Won Over Kerolox

Through approximately 2010, the dominant rocket propellant combination for medium and heavy launch vehicles was kerosene-LOX (RP-1 / liquid oxygen) — the propellant used by SpaceX's Merlin engine, Russia's RD-180, and many predecessors. Kerolox is dense, well-understood, and has decades of operational heritage. The shift to methalox over the last fifteen years was driven by reusability requirements that kerolox could not satisfy economically. Kerosene burns 'dirty' — its complex hydrocarbon chains deposit coking residue inside engine flow paths, requiring expensive refurbishment between flights of any reusable engine. Methane burns far cleaner, dramatically reducing the per-flight refurbishment burden and enabling the rapid reuse cadence that makes reusable launch economically transformative. Methane also has higher specific impulse than kerosene at the same chamber pressure, providing a small but meaningful performance advantage. And methane is producible from atmospheric carbon dioxide and water via the Sabatier process — a critical capability for in-situ propellant production on Mars, which underpins SpaceX's Starship architecture and is incidentally a useful long-term consideration even for Earth-orbital programs.

These advantages collectively shifted the propellant selection consensus for new clean-sheet reusable launch programs from approximately 2018 onward. SpaceX bet on Raptor methalox for Starship; Blue Origin developed BE-4 methalox for both New Glenn and ULA's Vulcan Centaur; Chinese commercial launchers (Landspace, Cosmoleap, and others) and CASC have followed the methalox path; Relativity Space, Stoke Space, and most U.S. emerging launch programs have also chosen methalox. Kerolox remains the operational standard for legacy and near-term programs (Falcon 9 Merlin, Soyuz, and various others), but is no longer the propellant choice for new reusable clean-sheet designs at meaningful scale.

Comparing the Leading Methalox Engines

The leading methalox engines span a wide range of thrust classes, cycles, and operational maturity. SpaceX's Raptor — particularly the latest Raptor 3 generation in the 230+ ton sea-level thrust class — is the most operationally proven and the highest-performance methalox engine in production, powering both Super Heavy (33 engines per booster) and Starship (six engines per ship). Blue Origin's BE-4 (~550,000 lbf or ~250 tons sea-level thrust) powers both New Glenn (seven engines per first stage) and ULA's Vulcan Centaur (two engines per first stage), and is the second methalox engine in operational service at major-launcher scale. Landspace's TQ-12 (~80-ton class) is the operational engine for Zhuque-2 and Zhuque-3, validated through multiple flight campaigns. CASC's YF-209 (~80-ton class) is the state-developed commercial-sale methalox engine, tested by Cosmoleap as a backup engine for Yueqian-1. Cosmoleap's Qingyu-11 (~100-ton class, in development) is the proprietary engine intended to power Yueqian-1 in primary service, with deep-throttling variable-thrust capability essential for tower-catch recovery.

Variable Thrust: The Tower-Catch Requirement

An important sub-requirement that shapes engine design for tower-catch reusable rockets specifically is variable thrust capability. Tower-catch recovery requires the descending booster to throttle down to a precise hover-and-catch profile in the final seconds of flight — fixed-thrust engines cannot perform this maneuver. Cosmoleap's Qingyu-11 is being designed with deep-throttling variable-thrust capability for exactly this reason. SpaceX's Raptor is also variable-thrust, with deep-throttling capability validated through the Starship test campaigns. The engineering challenge of high-performance, deep-throttling, variable-thrust methalox engines is substantial, and the operational demand for them will continue to grow as more reusable launch programs adopt tower-catch or precision propulsive landing. The combination of methalox propellant choice and variable-thrust deep-throttling capability is becoming the default specification for the next generation of reusable launch first-stage engines.

What Comes Next

The methalox engine race will continue to define reusable launch architecture for the next decade. Performance benchmarks will keep rising — SpaceX's Raptor 3 has set a new bar for thrust, throttling range, and reusability that competitors will need to approach. Variable-thrust deep-throttling capability will become a baseline expectation rather than a differentiator. Production scaling will become the operational challenge — SpaceX is producing Raptor at high rate to support Starship and Super Heavy cadence, and Chinese commercial launchers will need to scale Qingyu-11, TQ-12, and YF-209 production proportionally to support their own vehicle cadence ambitions. For founders and investors in adjacent space sectors, the methalox engine commercialization wave is one of the most structurally important technology transitions of the 2020s, and the cohort of operational methalox engines and the launch vehicles they power will define what reusable launch can deliver — and at what economics — through the rest of the decade.

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