Abstract
The rapid expansion of the space sector is creating an urgent need for resilient and sustainable propellant supply chains. Current architectures, however, is highly costly, safety, and incompatible with a circular space economy, calling for the in-space manufacturing of green propellants from local resources. This perspective frames in‑space propellant manufacturing as a grand challenge for chemical engineering, in which reaction, separation and systems design must be re‑imagined. We map space‑accessible feedstocks to feasible reaction networks and identify key challenges imposed by extreme space environment. These challenges, in turn, open new opportunities for chemical engineering and technology research. Sustainable reaction technologies, microstructured reactors, space-environment-assisted processes, spacecraft-inspired thermal and radiation management, and AI-enabled autonomy deserve particular attention for enabling in-space propellant factories. Their space-oriented developments can follow a research roadmap that couples fundamental studies of multiphase reaction and transport in microgravity with scale‑up methodologies, digital twins and ground‑to‑orbit validation strategies. By positioning in‑space propellant manufacturing as a new frontier for chemical engineering science and practice, this perspective aims to catalyze cross‑disciplinary efforts towards a sustainable in-space chemical supply and to position space as a proving ground for future net‑zero, resource‑lean chemical manufacturing on Earth.
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•In-space propellant manufacturing is discussed from a chemical engineering perspective.•Reaction networks and the space-imposed challenges are analyzed.•Key enabling technologies from the reaction to system levels are proposed.•More experimental data is required to improve the mechanistic understanding.