SpaceX Falcon 9
To redesign the Falcon 9 first-stage propulsion system by replacing RP-1/LOX with CH₄/LOX in order to reduce the overall mass ratio, while retaining the baseline second-stage Merlin 1D engine. Core objectives included improving specific impulse (Isp), evaluating turbopump power tradeoffs, estimating propellant tank volumes, and assessing trajectory-averaged performance. This redesign aligns with an industry shift toward CH₄ for cleaner combustion and improved reusability. This team project was completed for MAE 4321: Aerospace Propulsion at UT Arlington.
Project Type: Team
Team Member: Raymond Fisk
Duration: ~4 weeks
Tools Used: NASA CEA, ATMOS (altitude modeling), MATLAB, Excel (performance calculations)
Focus: Nozzle modeling, Isp optimization, tank sizing, and turbopump analysis
Outcome: Reduced mass ratio (25.75 to 22.98) through CH₄ redesign with pump/tank tradeoffs
Replaced RP-1 with liquid methane (CH₄) in the first stage while maintaining Falcon 9’s chamber pressure, nozzle area ratio (ε = 16), and equivalence ratio (Φ = 0.8).
Used NASA CEA to simulate nozzle flow properties (pressure, temperature, Mach number, and velocity), as functions of area ratio and altitude.
Calculated thrust and specific impulse (Isp) variations from sea-level ignition to Mach 10 stage separation (~75 km).
Computed propellant mass flow rates, tank volumes, and turbopump power requirements for both stages.
Simulated both CH₄- and RP-1-based configurations to evaluate design tradeoffs in mass ratio, power consumption, and tank sizing.
Achieved a lower overall mass ratio: 22.98 (CH₄ design) vs. 25.75 (original Falcon 9 configuration).
First Stage Thrust vs Altitude (CH₄ vs RP-1)
Stage 1 Mach Number vs Nozzle Area Ratio
CEA Simulations: Generated pressure, temperature, Mach number, and velocity vs. area ratio plots at various altitudes
Performance Charts: Plotted thrust and specific impulse (Isp) from sea-level ignition to Mach 10 separation (~75 km)
Computed Outputs: Calculated tank volumes, pump power requirements, Isp averages, and mass ratios for both stages
Design Summary:
Propellant Change: CH₄ chosen over RP-1 for higher Isp, cleaner combustion, and improved reusability potential
First Stage: Pc = 95.73 atm, ε = 16, Φ = 0.8
Second Stage: Retained baseline Merlin 1D, ε = 165
Tradeoff Analysis:
Achieved lower propellant mass fraction and pump power in second stage
Accepted increased tank volume in first stage as a design tradeoff for better Isp and mass ratio
Modeled nozzle flow behavior using NASA CEA and ATMOS data across design altitudes
Analyzed specific impulse (Isp) trends to inform trajectory-averaged performance metrics
Calculated turbopump power requirements based on chamber pressure, fluid densities, and mass flow rates
Iteratively balanced tradeoffs between Isp gains and tank volume increases to optimize first-stage performance
This project involved extensive performance modeling, including calculations for thrust, specific impulse (Isp), turbopump power, and propellant tank sizing. Key parameters such as chamber pressure (Pc), area ratio (ε), equivalence ratio (Φ), fuel/oxidizer mass breakdowns, and stage mass ratios are summarized in the final design configuration.
First-Stage Isp: 310.4 s
Second-Stage Isp: 359.2 s
Final Mass Ratio: 22.98
Baseline Mass Ratio: 25.75
Thrust: 7,599 kN
Chamber Pressure (Pc): 95.73 atm
Nozzle Area Ratio (ε): 16 (Stage 1), 165 (Stage 2)
Equivalence Ratio (Φ): 0.8
*Detailed values are available in the submitted Excel design spreadsheet. A PDF snapshot is available upon request.*
Rebalancing engine performance, mass ratio, and thrust requirements required multiple design iterations
Adjusted design point altitude, oxidizer-to-fuel ratios, and tank volume estimates to optimize tradeoffs
Navigated complexity between CEA output assumptions and real-world physical design constraints
Managed tradeoffs between specific impulse (Isp) gains and increased first-stage tank size and pump power
Achieved a reduced overall mass ratio of 22.98, improving upon the Falcon 9 baseline of 25.75
Increased specific impulse (Isp) for both stages, while managing tradeoffs in tank volume and turbopump power
Demonstrated ability to iteratively optimize performance metrics through simulation, modeling, and engineering judgment
Individual contributions included: baseline system analysis, CEA nozzle modeling, configuration summary, pump power/tank sizing, and report delivery
*This project was completed in a team of 2. I contributed to baseline performance analysis, CEA parameterization, design optimization, and full report development.*
NASA CEA · Rocket Propulsion System Design · Nozzle Flow Simulation · Mass Ratio Optimization · Tank & Turbopump Sizing · Specific impulse (Isp) Trade Studies · MATLAB Modeling · Excel Engineering Tools · Technical Reporting & Communication
This project deepened my understanding of propulsion system design by challenging me to evaluate tradeoffs in stage performance, subsystem sizing, and propellant selection. Iterating between design parameters and output metrics strengthened my intuition for how rocket stages respond to changing conditions. Working with NASA CEA introduced me to industry-standard analysis tools and boosted my confidence in interpreting performance data, thermodynamic cycles, and system-level modeling of launch vehicles.
*Note: Detailed CEA outputs, design plots, and configuration documentation are included. Full Excel calculations and trade study spreadsheets are available upon request*
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