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Relativity

Relativity is a standalone KSP 1.12.x gameplay mod that adds the sub-light half of special relativity. It makes the light barrier felt — without any faster-than-light cheating — by modulating force and consumption rate as a vessel approaches the speed of light. It never touches the physics integrator, so it rides alongside Principia and the stock flight model identically.

⚠️ v0.1.0-beta. Core relativistic flight is verified in-game; several integrations are built but not yet play-tested. Back up your save before a long relativistic mission.

The idea in two effects

Near light speed, two opposing things happen — and one twist:

1. The faster you go, the less your engine accelerates you. Effective thrust falls as 1/γ³, so c becomes a natural wall you approach but never cross. This is direction-blind — braking is just as feeble, so you must begin arrival deceleration absurdly early.
2. The faster you go, the slower your crew's clock runs → supplies last longer. Proper-time resource burn slows as 1/γ. A 50-year cruise might cost only ~24 years of food and air.
3. The twist: radiation doesn't slow down. Dose comes from outside, on coordinate time, so a fast crew ages less but soaks the same dose. Radiation, not starvation, is the binding constraint.

→ Getting fast is hard, but once you are fast your crew survives far longer. You pick a cruise speed around that tension.

Wiki contents

• Installation — requirements, CKAN / manual install.
• The Physics — the background theory: β, γ, the 1/γ³ thrust wall, proper-time 1/γ, radiation, reference frames, attitude.
• Dashboard — reading the in-flight HUD (Simple/Expert, the two clocks, the brake cue).
• Trip Planner — sizing a ship in the VAB/SPH before you launch.
• Configuration — every relativity.cfg key.
• Compatibility — Principia, Kerbalism, RP-1, life-support mods, warp mods, autopilots.
• FAQ — "why can't I stop?", radiation, and other gotchas.

What it is not

No visuals (no starbow shader — a separate lane), no time-warp/clock manipulation (the crew clock is a passive odometer), no general relativity, and no dependency on any planet pack. It ships no drive or parts of its own — it is a pure layer that does nothing until some other mod's high-ΔV drive actually pushes you to a relativistic speed.

License: MIT. Source: https://github.com/Vannadin/Relativity