Flight Accelerate under Timewarp still not working in some cases (Often in Large SOI's)

jclovis3 · December 22, 2023

What Happened:
While taking off from Minmus in a Northly direction, I used the time warp and noticed my Ap stopped changing. Fuel was still being consumed. The trajectory arc was also not changing.

Evidence:
I tried loading from a quick save and even restarting and this bug persists, so I'm attaching the quick save.

Video:

Included Attachments:

BuggedSave.zip

Edited June 13, 2024 by The Space Peacock
Added video and reformatted text.

ittoscano · January 7, 2024

Hi, i have had and stil have the same problem, when i burn with xenon engine, if i increase the speed of time, the vessel won t accelerate.

Then if i put time back to 1x, i can ' t decelerate and i have message "cannot move thrust over 1x time" (This is ehat it mean, i don t know the real message because i have game language in italian).

i must to reload the game and everything return working, but i cant increase time speed and it is precisely with that type of engine, which doesn't have much thrust, that it would be useful to have timewarp!!

Anyone havehad this problem and have a solution?

Can you increase time speed with Xeno engine?

Update: this happens when i am in a vessel which was generated from a later stage, when the vessel is exactly the big one that i launch it' s work...

Many thanks..

Edited January 7, 2024 by ittoscano

Anonymous Bug Reporter · January 13, 2024

I've encountered the exact same bug as mentioned in this reddit thread only in my case I was using a LV-N "Nerv" hydrogen engine.

Kind regards

Included Attachments:

NewIkeLander.json

DuBisch · January 19, 2024

Still encountering this Issue with 3 Ion Engines while trying to escape Kerbin orbit. It only happens on Ion engines though, not on others.
(also they are build on a multi engine mount, not sure if related though).

pschlik · January 20, 2024

Here to report I am seeing the same thing with ion engines as well. This will make my Jool ion probe far more cumbersome than I was hoping it would be...

The theory that small accelerations are getting neglected due to rounding error makes sense to me, this particular probe was only pulling a pitiful 0.002 G of acceleration, easily low enough to say it's 'close enough to 0'.

Anonymous Bug Reporter · January 22, 2024

Sometimes when you have the engines on to do a manouver and turn on time warp, the DeltaV of the Spaceship wont change anymore although the engines are running and the Ship loses fuel.

Included Attachments:

Ghnuberath · January 24, 2024

I can also confirm this bug. I have a probe with 3x ion engines. It was working fine in kerbin orbit up to about 0.8km AP/PE and then suddenly no thrust in time warp despite fuel consumption. I was doing repeated burns to escape Kerbin SOI.

I have definitely noticed this once with nuclear engines as well. On return from Duna I time warped a few intercept correction burns and ended up with vastly less fuel and unmodified trajectories and didn't know what had happened.

T the G · January 27, 2024

Yep, this bug makes low TWR craft unusable.

The tips reported here (like switching to VAB/tracking station and back again) don't work for me.

I am now doing a 28 (real-life) hour burn, because I really want to get to Jool with my Xenon engine. With timewarp above 1x, fuel and electricity are being consumed, but the orbit does not change.

I cannot seem to attach my bug reports (generated using KSP2_BugPackager), does anyone know how? (Aside from hosting on e.g. Google Drive and adding the link here.)

darude · January 28, 2024

nvm still bugged

Edited January 28, 2024 by darude
i was wrong

Anonymous Bug Reporter · January 28, 2024

I was trying to do a low sun-orbit using the ion/xenon engine because of the high fuel efficiency. but after activating the engine about 1m-km-periapsis from kerbol and then time-warping i noticed that the time-warp broke and the engine produces no trust. Every time-warp stage is 1x. you cant even do things to the craft as time-warp is over 1x (even at the 1x setting) the number under the time-warp bar that recites the current time-warp speed is always at 1x at every time-warp level.

Included Attachments:

SolarAdmiral · February 3, 2024

Reported Version: v0.2.1 (latest) | Mods: none | Can replicate without mods? Yes

OS: windows-11 | CPU: i7-13700 | GPU: rtx-3070ti | RAM: 32,0 GB

I've been doing some Ion probes and I've been getting this. Acceleration under timewarp worked fine at some times, but not at others. When it worked it seemed correct. When it wasn't working, no acceleration at all happened during timewarp even though the ion engine was still using power, the orbit PE didn't move at all. Acceleration started happening again as soon as changing back to x1 speed. It seemed like it didn't work when the probe was heavier. A light Ion probe worked fine while under timewarp. But after editing it, adding a few parts and making it heavier, suddenly it also wouldn't work when warping. Since all the probes only had one engine, the heavier one had a lower acceleration. Maybe this bug is being caused by low accelerations? It did seem like the Ion probes with a higher acceleration were able to timewarp.

Margoth · February 3, 2024

(0.2.1) I'm encountering this randomly with Dawn. E.g. I have a number of identical very light probes (sample return pods), one of them bugged out in the above described way after escaping Eve SOI - worked fine while within SOI. Another probe escaped Eve and did a 90min burn just fine under time warp. Reloading and quitting game don't seem to help. Don't know if related, but the AP/PE reported in lower left seem to be bugged too (reported 0m/0m or -2,088km/20,567m)

SolarAdmiral · February 3, 2024

~~New observation. I'm tending to find the ions work on timewarp while in Kerbol's sphere, but not while in the sphere of a planet or moon.~~

Nevermind. Satuts was, not working at Kerbin, working in Kerbol SOI, not working at Moho, working at Kerbol SOI, but then working second time in Moho SOI.

Edited February 3, 2024 by SolarAdmiral

Anonymous Bug Reporter · February 6, 2024

I've not tried this with any other type of engine, but for sure the problem exists with ion engines. I've got a small probe in an eliptical orbit around Eve and I'm using an IX-6315 "Dawn" engine to slowly work down to a circular orbit I'm having to run the burns in 45min intervals but every time I try to increase time warp above 1x, all thrust stops. The animation continues. And it shows Xenon and EC being used, but PE and AP never change.

Something else I encountered on one test run, I let the EC run out completely but the engine never stopped burning and because the engine was using more EC than my solar panels could produce, I couldn't shut the engine down.

Included Attachments:

kdaviper · February 7, 2024

I noticed the game would not let me adjust throttle at 1x timewarp after trying to burn under timewarp with these engines.

goatduoduo · February 7, 2024

The bug remains unresolved and occurs consistently under specific steps.

1.launch a vessel (especially with ion engine, but other engines still have bug as well)

2.go to an orbit

3.quit game and reenter game

4.control the vessel you launched recently

5.try to burn in time warp

You will see AP and PE do no changes while burining and fuel still consuming as well.

The Aziz · February 11, 2024

This better be in the top5 of next KERB marked as fixed and verified for a hotfix. I'm about to give up on the game. Not only burn doesn't do a thing, but also I can't quit timewarp.

Sun_Serega · February 26, 2024

The technical side of the problem:

When warp is engaged with thrust ON, the game tries to calculate the trajectory ("VesselComponent.HandleOrbitalPhysicsUnderThrustStart" method)

The end of that method has a sanity check, turning off this thrust-on-rails if either the position or velocity calculated for the current point in time (T=0) on the new trajectory is >=0.01 units off the actual current possition of your vessel.

Now, the only way this is telegraphed - is the

Quote

Delta error between patched orbit and NBody orbit too large. Cancelling Thrust under TimeWarp.

error message in the Alt+C.

This makes it extra nasty, because the game falls back to the non-thrust trajectory but doesn't turn off the engines - they keep wasting fuel with no good way to notice this in time.

My solution for myself

For now, I've turned off this sanity check in my "SASed Warp" mod, because this bug was preventing that mod from being useful.

If the Vanila game were to turn off the thrust-on-rails - with my fix you will instead see a debug message in the Alt+C, with pos(-ition) and vel(-ocity) error deltas.

P.S. The same fix was also added to the "Community Fixes" mod starting with v0.13, so having either my mod or CF is enough to fix (hide) this bug.
But if you have both, make sure "SASed Warp" is at least v2.3, otherwise there will be a conflict with CF.

From my experience of flying in and then out of 800k Jool orbit, the position error is usually much larger for than velocity error.
But even with that, it's only enough to lose accuracy over time. There is no noticeable teleportation when warp starts.

Possible vanila solutions

I imagine a very small fraction of players will use mods. And my fix isn't really a fix - it just hides the problem to make it less annoying.
So it's still a good idea to do something official but temporary as soon as possible.

You could at least reduce thrust down to 0 and display a warning.
And maybe a settings toggle to turn off this sanity check?

As for long term - I think using the "double" type for such calculations was easy but a very bad idea:

Floating point may look like the right thing to use, given how the scale tends to change rapidly.
But when it really matters - is when you make a maneuver that goes through several very different scales.
Like LKO Jool transfer with 2 pre-planned gravity assists: off of Tylo and then Laythe.

Given that, I think a custom fixed-point numbers would be far more appropriate:

    unsafe struct Fixed256
    {
        private fixed uint data[8];

        //TODO

    }

If you properly use 64-bit carries with 32-bit data words - many things fall into place like puzzle pieces, so it's not as scarry as it might look at first.

And I don't think the speed will be an issue, since custom fixed numbers are generally faster (at least when they aren't 4 times bigger) and the "HandleOrbitalPhysicsUnderThrustStart" is already optimized to only be called once in a while.

Edited March 11, 2024 by Sun_Serega
fix the font color, it was black even for dark theme users

val778 · February 28, 2024

I have the same issue

This makes ion engines pratically unusable because randomly you are faced with this bug and either have to delete your bugged ship or have to do your 2 hours burn in x1 speed :mad:

Edited February 28, 2024 by val778

dolphin263 · February 29, 2024

One thing I have noticed is this reliably happens if available delta-v > 64k. It's hard to do that without mods, but with mods can be easy.

20 hours ago, val778 said:

I have the same issue

This makes ion engines pratically unusable because randomly you are faced with this bug and either have to delete your bugged ship or have to do your 2 hours burn in x1 speed

Ah, does your vessel have delta-v over 64k? If so, that's the issue. I forgot about the ion engine, but that has high isp so you probably can get more than 64k delta-v, which is what seems to trigger this.

Edited February 29, 2024 by dolphin263

Sun_Serega · February 29, 2024

2 hours ago, dolphin263 said:

One thing I have noticed is this reliably happens if available delta-v > 64k

No, it's related but not the trigger. I just explained this bug above.
Basically you need high position or velocity. With how floating point numbers work - this lowers precision, triggering that sanity check.
High position is easy to get, for instance teleport to a high circular orbit above Jool, its extreamly consistent there. I casually reproduced it first try at the end of my mod's demonstration video.

Edited February 29, 2024 by Sun_Serega
add link to explanation "above"

ShadowZone · March 3, 2024

Situation: retrograde orbit around Laythe. I want to flip the trajectory, so there is a maneuver plan already set in the attached save game. When performing the burn, the game always refuses to do burn under timewarp in this situation.

Being around Jool generally seems to trigger this bug very reliably.

Included Attachments:

ForSci_Bug42.mov

ForSci_Bug42_noBurnUnderTimewarp_logs.zip

Edited March 3, 2024 by ShadowZone
Request for merge no longer needed. Thanks!

Spicat · March 3, 2024

@ShadowZone, merged your bug report.

val778 · March 3, 2024

When burning with ion engines and the orbit is very eccentric (like when braking to enter orbit after interplanetary transfer), time warping while burning with ion-engine doesn't affect the orbit and still consume fuel. Ion engines thus only work in time warp x1, which is a completey game breaking bug because this make low thrust ion engines completely worthless. I can't make a 1 day burn just to orbit my craft around Jool.

Please fix urgently

Included Attachments:

DibzNr · March 4, 2024

@val778Merged your report with this post

Flush Foot · March 12, 2024

Addition to:

When my ion-propulsed probe was in Kerbolar space, it had no trouble (mercifully) doing acceleration under timewarp (using both Ion-only and Ion + Nuke H2).

Now that I am in Moho's SOI and trying to burn off the last 100 m/s to capture into a reasonable orbit, acceleration under timewarp only results in fuel-burn, not orbital-modification...

Is it possible that the problem has to do either with being in a 'smaller SOI' or having an escaping-trajectory?

Included Attachments:

AccelerateunderTimewarpstillnotworkinginsomecases(Post-v0.2.0)_logs.zip

Flight Accelerate under Timewarp still not working in some cases (Often in Large SOI's)

Bug Report

Link to comment

Share on other sites

58 answers to this question

Recommended Posts

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites

Link to comment

Share on other sites