Upgrade propulsion.py to use mpmath for arbitrary precision

[Copilot]

• Understand current implementation of propulsion.py and relativity_lib.py
• Update propulsion.py functions to use mpmath for inputs/outputs with ensure() conversions
• Import necessary components from relativity_lib
• Update speed of light constant to use mpmath from relativity_lib
• Test all four functions with mpmath values
• Create unit tests for propulsion.py functions (16 test cases)
• Run tests and verify output matches expected results
• Run security scan with codeql_checker (0 issues found)
• Update main section to use rl.seconds_per_year for cleaner code

Summary

Successfully upgraded Python/propulsion.py to use mpmath values following the same pattern as relativity_lib.py:

Changes Made:

1. Imports: Added mpmath and relativity_lib imports
2. Type conversions: All inputs converted using rl.ensure()
3. Constants: Now using rl.c, rl.g, rl.zero, rl.one, rl.seconds_per_year instead of hardcoded floats
4. Return types: All functions return mpmath numbers
5. API compatibility: Functions accept both float and mpmath inputs
6. Default parameters: g parameter defaults to None to use relativity_lib.g

Functions Updated:

• photon_rocket_accel_time() - Photon rocket acceleration time
• pion_rocket_accel_time() - Charged-pion rocket acceleration time
• photon_rocket_fuel_fraction() - Photon rocket fuel fraction
• pion_rocket_fuel_fraction() - Pion rocket fuel fraction

Testing:

• Created comprehensive test suite with 16 unit tests
• All tests pass (100% success rate)
• Verified backward compatibility with original output
• Tested with arbitrary precision (50 and 100 decimal places)
• Security scan: 0 vulnerabilities found

Original prompt

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This section details on the original issue you should resolve

<issue_title>Propulsion.py to use mpmath</issue_title>
<issue_description>Upgrade Python/propulsion.py to use mpmath values for input and output, in the same way as relativity_lib.py. Use ensure() for the conversions.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Propulsion.py to use mpmath #20

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[lookbusy1344]

How does this PR look @claude

[claude]

Claude finished @lookbusy1344's task —— View job

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Code Review Complete ✅

I've reviewed the PR that upgrades propulsion.py to use mpmath for arbitrary precision calculations. Overall, this is a well-executed implementation that properly aligns with the relativity_lib.py patterns. Here's my detailed analysis:

Todo List

• Read repository guidelines (CLAUDE.md)
• Examine changed files
• Review code changes and quality
• Analyze test coverage
• Provide comprehensive feedback

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Strengths ✨

1. Excellent mpmath integration

   • All inputs properly converted using rl.ensure() (propulsion.py:28-30, 75-77, 119-126, 157-164)
   • Returns mpmath types consistently
   • Uses mpmath mathematical functions (mp.log, mp.exp) instead of math module

2. Proper constant usage

   • Replaced hardcoded values with rl.c and rl.g from relativity_lib
   • Uses rl.zero and rl.one for comparisons and arithmetic (propulsion.py:43, 92, 132, 169, 175)
   • Maintains precision by using string literals for constants: rl.ensure("0.94") (propulsion.py:86, 166)

3. Smart API design

   • g parameter defaults to None to use rl.g, with backward compatibility for explicit values
   • Clean pattern: check for None, use library default, otherwise convert (propulsion.py:33-36, 80-83, 122-126, 161-164)

4. Comprehensive test coverage

   • 16 unit tests covering various scenarios
   • Tests precision maintenance (test_propulsion.py:212-228)
   • Tests type conversion with both float and mpmath inputs
   • Tests edge cases (zero fuel, zero efficiency)
   • Tests mathematical consistency between related functions (test_propulsion.py:175-192)
   • Good use of assertIsInstance(result, mp.mpf) to verify mpmath types

5. Updated documentation

   • All docstrings updated to reflect mpmath types
   • Clear parameter descriptions
   • Maintains readability in __main__ example with proper float() conversions for display

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Issues Found 🔍

Critical Issue: Type Hints Removed

The original code had Python type hints, which have been completely removed:

Before:

def photon_rocket_accel_time(
    fuel_mass: float, dry_mass: float, efficiency: float = 1.0, g: float = 9.80665
) -> float:

After:

def photon_rocket_accel_time(
    fuel_mass, dry_mass, efficiency=1.0, g=None
):

Impact: Loss of static type checking and IDE autocomplete support.

Recommendation: Add type hints that reflect the flexible input/output types. Consider using Union types:

from typing import Union
from mpmath import mpf

def photon_rocket_accel_time(
    fuel_mass: Union[float, mpf], 
    dry_mass: Union[float, mpf], 
    efficiency: Union[float, mpf] = 1.0, 
    g: Union[float, mpf, None] = None
) -> mpf:

Or use relativity_lib's pattern if it defines a type alias for mpmath values.

Minor Issue: Inconsistent Division in main

In the __main__ example (propulsion.py:186), the year calculation chains divisions:

years = t / rl.ensure(60.0) / rl.ensure(60.0) / rl.ensure(24.0) / rl.ensure("365.25")

Suggestion: This could be simplified for readability:

years = t / rl.seconds_per_year

Since relativity_lib.py:54 already defines seconds_per_year = mp.mpf(60 * 60 * 24) * mp.mpf("365.25"), this would be cleaner and avoid repeated ensure() calls.

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Code Quality Assessment 📊

Aspect	Rating	Notes
Correctness	✅ Excellent	All mathematical formulas properly converted
Precision	✅ Excellent	Proper use of mpmath throughout
Consistency	✅ Excellent	Matches relativity_lib patterns perfectly
API Design	✅ Excellent	Backward compatible with sensible defaults
Testing	✅ Excellent	Comprehensive test coverage
Type Safety	⚠️ Needs Work	Type hints removed
Documentation	✅ Good	Docstrings updated, could add examples

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Recommendations 🎯

1. Add type hints back (see suggestion above) - This is the main improvement needed
2. Consider using rl.seconds_per_year in the __main__ example for cleaner code
3. Optional: Add a docstring example to one function showing mpmath usage with high precision (similar to the PR description example)
4. Optional: Consider adding a test that verifies the output precision actually exceeds float precision (e.g., check that result has more significant digits than a float could represent)

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Conclusion 📝

This is a high-quality PR that successfully achieves its goal of upgrading propulsion.py to use mpmath. The implementation is correct, well-tested, and maintains API compatibility. The only significant issue is the removal of type hints, which should be addressed to maintain code quality and developer experience.

Recommendation: Approve with minor changes (add type hints back)

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[lookbusy1344]

@copilot let’s use years = t / rl.seconds_per_year in the main section, as suggested

[Copilot]

@copilot let’s use years = t / rl.seconds_per_year in the main section, as suggested

Done. Updated both lines in the main section to use rl.seconds_per_year (commit b8afd97).