Does Physics Warp 4X affect dV to orbit?

[Jetski]

Patience isn't really my strong suit, and the majority of my ships spend at least some if not all of their time getting to LKO at max physics warp.  It's one of the design constraints for my ships - if they wobble apart at max warp I redesign.  Even some surprisingly large and unwieldy contraptions can do it if you balance right.  

My ascent is nearly always the same: liftoff with TWR>1.5, generally stick to 1.5-1.7 until 25K or so, then 1.7-3 depending on engines.  Straight up until 100ms, tip to 2.5-5 degrees, then follow prograde more or less.  Some ships I can turn off SAS and let it follow on its own, some I steer, some I get really lazy and click follow prograde marker (but I know this wastes fuel from the wobbly steering losses).

My question is this:

Am I losing potential dV savings by using physics warp?

It FEELS like I have a more efficient ascent the few times I lift off at normal speed, generally if I have something REALLY fragile for a challenge or something. 

Has anyone researched this?

I'm considering doing a test rocket series, but wanted to see if this has already been addressed.

[Kyrt Malthorn]

In my experience, x4 physics warp during during an atmospheric launch tends to make my rockets less stable, and aero forces apply much more 'suddenly'.  As weaker joints flex and arodynamic stresses are applied in bigger bites, I believe more thrust vectoring is used to correct, shaving off efficiency and dV.  So I would expect to see at least a percentage of efficiency lost there, but would be interested in a more scientific approach as well.  I'm assuming you'd want to use mechjeb, kOS, or some other autopilot to avoid pilot error skewing the results.

[John FX]

I would say to try launching with MJ at 4x then reverting and launching the same craft at 1x to see if you end up with more or less Dv once in orbit.

You  would probably have your answer before anyone posts another reply...

[Dunbaratu]

2 hours ago, Kyrt Malthorn said:

 I'm assuming you'd want to use mechjeb, kOS, or some other autopilot to avoid pilot error skewing the results.

I don't know about the internals of mechjeb, but I do know that the very same kOS script can end up behaving differently under physics warp than under normal 1x speed.   By increasing physics warp, you're lengthening the amount of game-universe time that passes in-between moments when the universe is frozen.  That effectively makes the simulation more course-grain, and thus makes the control software less quick to react.  I imagine it slightly alters mechjeb's flying too because there's nothing it can do to change the fact that under 4x physics warp, the universe is effectively "frozen" for four times as long in between simulation updates.  The same PID controller that might work well on a deltaT of 0.04s will be a bit more choppy when having to work with a deltaT of 0.16s.  That can cause slightly larger steering losses.  Not by a lot, but by enough to muddy the precision of the sort of test you're proposing.

 

[Kyrt Malthorn]

5 minutes ago, Steven Mading said:

<snip>

Good point.  But it'd be a more reliable test than human piloting, which would suffer the same and more.

[pincushionman]

58 minutes ago, Steven Mading said:

…Not by a lot, but by enough to muddy the precision of the sort of test you're proposing.

…Except that is exactly the phenomenon you would be testing for.

[Dunbaratu]

5 hours ago, pincushionman said:

…Except that is exactly the phenomenon you would be testing for.

Not necessarily.  If you're trying to test for whether the stock game's physics calculation changes things at 4x, throwing in something else that also makes the steering differ too isn't what was being tested for.

[ExtremeSquared]

I wouldn't dare try in atmosphere. Deep space missions seem to turn quickly into that Event Horizon movie at just 2x warp.

[Jetski]

My thought was to design a rocket that doesn't require input to make the gravity turn - SAS turned off, so no thrust vectoring.  A true gravity turn that doesn't need MJ.  I think we can assume that any increase in control movements by a vectored thrust engine is going to use more fuel.  If the rocket isn't pointed straight, part of the thrust and therefore the fuel is going the wrong way and therefore wasted.  Likewise fins/drag control input will cause losses as well.  

My question is whether the physics calculations of the simple act of using the 4X warp is using more or less fuel in a controlled test.

I have a plan for a test rig and a series of launches, tentatively something with fixed fins and no thrust vector, just a reaction wheel to make the initial turn.  Open to suggestions.

But I'm waiting to see if anyone will chime in who has already addressed this in a scientific way 

 

[John FX]

OK then, simple test. Straight up, thrust until empty, observe height.

If warp makes it change then that happens, if not then not.

[hempa2]

1 minute ago, John FX said:

OK then, simple test. Straight up, thrust until empty, observe height.

If warp makes it change then that happens, if not then not.

Isn't there a tiny amount of randomness in the aero forces?

[Jetski]

1 minute ago, John FX said:

OK then, simple test. Straight up, thrust until empty, observe height.

If warp makes it change then that happens, if not then not.

Not a bad idea, really.  My concern was more how it would affect making orbit, but this should give some information at least...

[John FX]

6 minutes ago, hempa2 said:

Isn't there a tiny amount of randomness in the aero forces?

repeat three times to average that out if there is any difference between warp and no warp.