FAQ

FAQ & gameplay tips

"Why can't I stop?!"

Because braking is an engine burn, and near c all engine thrust is crushed by 1/γ³ - braking is exactly as feeble as accelerating (The Physics#1-thrust-falls-as-1γ3-the-light-wall). At 0.9c you have ~8% of your thrust; at 0.99c, ~0.3%. You have to start decelerating absurdly early - often a light-year or more out. Watch the ⚠ decel now cue on the Dashboard, and set a target in the Trip Planner so the cue knows the real distance. And remember you must turn around first, which is also slowed (The Physics#4-attitude-turning-slows-as-1γ) - leave lead time even to point retrograde.

The nothing happens until I'm going really fast

That's intended. The layer gates on betaMin and in-system speeds are ~10⁻⁵ c, so it stays fully idle until interstellar cruise. It ships no drive - you need a high-ΔV torch/fusion/antimatter/warp drive from another mod to reach a relativistic β at all. See Installation#verifying-it-works.

My crew barely aged but the mission took decades - bug?

No - that's the point. The crew clock runs slow by 1/γ, so a 50-year outside trip can cost only ~24 years of crew time and supplies. The gap is permanent; slowing down doesn't undo it (the twin paradox). The two clocks and their difference are shown on the Dashboard.

So supplies are basically free at high speed?

Not free - radiation is the catch. Dose is not dilated (it's external, coordinate-time), so a fast crew ages less but soaks the same dose. On a long relativistic run, radiation, not starvation, is what kills you. See The Physics#3-the-twist-radiation-stays-on-coordinate-time. (Requires Kerbalism to model dose.)

MechJeb / kOS mis-times my burns near c

Known limitation. The mod cuts thrust with a corrective force, leaving the engine's advertised thrust/ISP unchanged - so tools estimating from reported thrust don't see the reduction and under-estimate burn time. Measured-acceleration executors self-correct partially. A proper fix (exposing an effective-thrust value these tools can read) is on the v0.2 roadmap. See Compatibility#autopilots--time-warp.

Does this work with Principia?

Yes - that's the headline feature. It modulates force and rate only and never touches the integrator, so Principia is unaffected (and even supplies the barycentric velocity). Just don't expect orbit-editing warp mods to work under Principia - that's a Principia limitation independent of this mod.

Does it break my existing saves / non-relativistic play?

No. Below betaMin everything is identity - the mod does literally nothing to normal in-system craft. It only adds a per-vessel crew-clock value to the save. Still, back up before a long relativistic mission - it's a long mission.

Can I make the effects turn on earlier / turn attitude slowdown off?

Yes - edit GameData/Relativity/relativity.cfg. Raise betaMin, set attitudeExponent = 0 to keep turning instant, toggle kerbalismDilation, etc. Every key is documented on Configuration.

The dashboard won't appear

It auto-opens only when the layer is active (β above the gate) - i.e. during relativistic cruise, not in normal flight. If you pinned it, an idle layer shows off (sub-relativistic). If you think it should be active, check KSP.log (and see the diagnostics in Installation#diagnostics).

Persistent Thrust while time-warping doesn't get the thrust penalty

Correct, in this release. PT applies thrust as an orbit edit that the loaded force hook can't intercept, so the 1/γ³ cut for unloaded PT is deferred (the crew clock still tracks it). It's on the roadmap, paired with Principia's own persistent-thrust work. See Compatibility#propulsion-what-gets-you-to-relativistic-speed.

Why is the sky changing colour at speed?

That's the relativistic visual layer (Visuals): forward blueshift + brightening, aft redshift

• dimming, star-bunching aberration, and a Doppler-shifted sunflare - what your crew would really see. It's cosmetic only and gates exactly like the physics (off below betaMin, under warp, and in map view). dopplerVisual = false turns all of it off.

The ship's outline shimmers/sparkles at high speed

Almost always TUFX/PPv2 TAA - temporal reprojection fights the screen-space warp (no motion vectors) and is documented unsupported. Switch your TUFX profile to SMAA or FXAA; both are verified fine. Scatterer's own TAA is handled automatically. See Visuals#anti-aliasing.

Does the visual layer cost performance?

Only while it's actually on screen: everything engages with the layer (β above the gate), the plume mask only runs while thrust is flowing, and the rear sky camera only above β ≈ 0.5. Normal in-system play renders exactly stock. If you need frames at cruise, see Visuals#performance.

How do I report a bug?

File an issue with your KSP.log (bundle it with KSPBugReport) at https://github.com/Vannadin/Relativity/issues. The most useful reports: does thrust visibly fall near c, do supplies slow ~1/γ while dose does not, does attitude get sluggish, and - for RP-1 - does a returning relativistic crew keep their career.