Designing for Reuse: Technical Challenges and Performance Trade-offs for Reusable Liquid Propellant Rocket Engines
- Paper ID
97222
- DOI
- author
- company
Massachusetts Institute of Technology (MIT)
- country
United States
- year
2025
- abstract
Over the last decade, the emergence of efficient reusable launchers has revolutionized the economics of spaceflight. Between 2000 and 2012, the average cost of a Space Shuttle launch was approximately \$1 billion (FY2012), translating to around 50,000 \$/kg (FY2024) to send payloads to Low Earth Orbit (LEO). By contrast, in 2024, SpaceX’s Falcon 9 standard launch cost was \$69.75 million, or about 3,000 \$/kg. Unlike the Shuttle, which incurred substantial refurbishment expenses, SpaceX maintains significant profit margins through an optimized reuse strategy. The cost of launching a Falcon 9 rocket with recovered boosters was estimated between \$15 million and \$20 million, accounting for the recovery and refurbishment of the first stage and fairing, as well as the production of a new second stage. This effectively translates to a launch cost of less than 1000 \$/kg to LEO and a net margin of over \$50 million. In the next decade, this cost reduction trend is set to maintain momentum, with the deployment of SpaceX’s Starship and its projected per-kilogram cost to LEO in the hundreds of dollars. However, realizing the economic potential of reusable launch vehicles poses great engineering challenges. Not only must reusable rockets produce sufficient thrust to achieve orbit insertion and recovery, but they must also endure the harsh liftoff and re-entry conditions across multiple cycles. This demands additional hardware, including grid fins and landing legs, as well as the lifecycle optimization of critical components, such as heat shields and engines. Consequently, reusability requirements introduce new system trade-offs, most notably with regard to performance. This paper presents qualitative and quantitative insights into the technical challenges and trade-offs of rocket reusability, focusing on the design of Liquid Propellant Rocket Engines (LRPEs). The study relies on a modular simulation architecture developed in MATLAB Simulink, designed to model major LPRE components under steady-state and transient conditions. By varying design parameters such as propellant selection and oxidizer to fuel (O/F) ratio, the trade-off between performance and reusability is quantitatively assessed. Results are extrapolated to the broader vehicle architecture and evaluated in terms of economic viability, offering a comprehensive understanding of the technical and financial challenges that will shape the next generation of reusable rocket systems.