Supersonic Retropropulsion Ignition in a Martian Environment

Project Objective

This project addresses the current capability gap of non-hypergolic engine ignition for Supersonic Retropropulsion in a Mars-relevant environment to inform future testing and development of this technology.

Project Description

Supersonic Retropropulsion (SRP) has been identified as a technology gap, and it will be a critical capability in enabling the landing of larger payloads on Mars. Engines used for SRP will be required to operate in complex aerothermal and aerodynamic environments, potentially functioning across multiple phases of flight, including Entry, Descent, Landing, and Ascent (EDLA). Several capability gaps pertaining to propulsion system operation have been identified and will need to be addressed to raise the Technology Readiness Level (TRL) and progress towards an eventual flight demonstration of SRP, including the ignition of cryogenic propellants in a low pressure, CO2-rich atmosphere. The project seeks to test a gaseous oxygen and gaseous methane torch igniter in a vacuum chamber with CO2 used as an inert purging gas to simulate the Martian atmosphere to assess the reliability of non-hypergolic engine ignition in CO2. Preliminary fluid environments modeling will be leveraged to inform the testing environment.

Project Results and Conclusions

In support of the analysis campaign, a relevant Mars lander vehicle and engine architecture requiring SRP in its trajectory were identified. A Computer Aided Design (CAD) model was received and modified to utilize in Computational Fluid Dynamics (CFD) simulations. Initial CFD simulations were completed at conditions along the trajectory set just prior to engine ignition for SRP to assess the environment into which the engines would ignite. Results including the pressure contours inside the engine thrust chamber assemblies and engine section of the vehicle were provided to the team to help inform testing conditions. Based on these results, a representative environmental pressure was selected for targeting in the vacuum chamber testing.

The project completed procurement of traditionally manufactured Compact Augmented Spark Igniter (CASI) hardware. This hardware leveraged an existing design optimized for use with hydrogen. Additional modular igniter hardware assemblies that can be optimized for use with methane were additively manufactured utilizing GRX-810. Facility procurements for additional test setup needs were completed. Test matrices for the both the traditional and additively manufactured CASI assemblies were prepared. The matrices include 3-4 continuous ~10 minute test blocks per test day as vacuum chamber operations allow. Each test block is planned to have 30 ignitions to achieve statistical significance, but this may decrease if additional purge time is needed between ignitions. Hardware and facility supply pressures will vary between test blocks to achieve different igniter performance set points. An additional test block was planned at ambient conditions to compare igniter performance at Mars-relevant and Earth-ambient pressures. The test campaign is on hold while awaiting test facility availability in early 2025.

This project represents an opportunity to pursue a high-priority technology gap that will enable current and future investments into propulsion technologies for SRP. It leverages existing testing capabilities at the NASA Marshall Space Flight Center Component Development Area and propulsion expertise to drive technology development that can expand in the coming years. Additionally, it promotes early career engagement with center strategic priorities, fostering growth and innovation from the individual to the center level.

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