Typo correction and naming convention changed for propulsion_design

Description

Typo correction and naming convention changed for propulsion_design

Related Issue(s)

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Other Changes

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Screenshots/Logs

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Testing Instructions

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Developer Checklist

• Code has been tested locally and/or in pipeline.
• (if applicable) documentation updated.
• (if applicable) impact of new dependencies reviewed and included in project.
• Merge conflicts resolved with the target branch.

Additional Notes

Add any information reviewers should focus on, e.g., specific files, functions, or changes of interest.