Capability Snapshot

Current Strengths

• Energy conservation – 0.000 % drift over 1 000 orbits in benchmark runs.
• Integrator stability – RK45 adaptive integrator already delivers excellent accuracy and performance.
• Multi-body gravity – Solar system perturbations supported out of the box.
• J2 oblateness – Physically accurate zonal harmonics implemented and validated.
• Atmospheric drag – Exponential atmosphere with planetary co-rotation.
• Performance – 1 000-orbit regression executes in roughly 2 seconds on a modern laptop.
• Web-native experience – Real-time visualisation, scripting, and collaboration in the browser.

Critical Gaps vs STK

Physics Model	Darksun Status	STK Capability	Impact	Priority
Solar Radiation Pressure	❌ Missing	✅ Advanced	High	Critical
Higher Harmonics (J3+)	❌ J2 only	✅ J20+	High	Critical
Relativistic Effects	❌ Missing	✅ Relativity	Medium	High
Advanced Atmosphere	✅ Basic	✅ NRLMSISE-00	Medium	Medium
Maneuver Planning Tools	⚠️ In progress	✅ Astrogator	High	High
Conjunction Analysis	❌ Missing	✅ Advanced	Medium	Medium

Closing the SRP and gravity gaps gets us most of the way to STK equivalence for Earth-orbiting missions; the remaining items track toward high-precision and interplanetary scenarios.