Fuel flow/Prop. requirement issue while redirecting asteroids

[BadOaks]

Hi guys, not sure if this is a bug or a mechanic I'm not aware of, but during my last two asteroid redirect missions the engines have been giving a fraction of the thrust they should be while hauling the asteroid. In the most recent mission the tug had six LV-N's which should be giving 60 kN each, but I'm only getting 20 kN on max throttle. On a previous attempt I had a Rhino engine giving 11 kN when it should have been 2000. Right clicking showed low fuel flow and a "Prop. Requirement Met" of less than 100%.

I've done three successful redirections previously that didn't seem to have this issue.  Is there something that could limit the fuel flow of an engine despite fuel being available? 

Here's a screenshot. I'm nearly out of fuel here but was experiencing the same problem with half tanks.

[sal_vager]

Hi BadOaks, welcome to the forums.

There was a bug that caused one engine of a group to run at a lower thrust but that was fixed, so I think your issue is that there's not enough fuel available when the LV-N's ask for it.

You mention that the propellant requirement wasn't met and I can see the same in your screenshot, so I suggest you let the tanks fill up a bit before making another burn.

Jet engines will also reduce thrust if there isn't enough air available, so it makes sense that fuel is being treated the same way for your engines.

The engines can only use what's available after all.

[Snark]

Are you running ISRU at the same time that you're running the engines?  I've observed that there appears to be a bug that can happen in which an active ISRU somehow causes the engines to get starved (even when there's plenty of fuel in the tanks), and they put out only a fraction the power.

So, if you're running the ISRU, try turning it off-- does that help?

(No idea whether the ISRU bug I described is the same one that @sal_vager just described as having been fixed-- I haven't run into it in a long time, because it was such a showstopper that I trained myself to always turn off ISRU while thrusting, so I don't know if it's still an issue or not.)

[BadOaks]

ISRU seems to be the problem! I toggled it off and on quickly and engine thrust went up and down accordingly. Good to know! Thanks guys.

[Plusck]

The LV-N / ISRU combination is odd for that.

It appears that even though the LV-N generates electricity while running, it also needs to have electricity stored inside the LV-N itself (a tiny amount admittedly) to run properly. For some reason, the ISRU seems to draw the very same electricity that the LV-N needs even if there is electricity available elsewhere on the vessel, so your "Prop" drops.

What is even odder in your screenshot is that the LV-N says its internal storage is full. Whenever I've had the same problem it has been at zero. And also it says 33.93% requirements met, but with me (IIRC) it has always been 50% (on one of a twin- LV-N vessel, so logical there).

[Snark]

19 minutes ago, Plusck said:

The LV-N / ISRU combination is odd for that.

It appears that even though the LV-N generates electricity while running, it also needs to have electricity stored inside the LV-N itself (a tiny amount admittedly) to run properly. For some reason, the ISRU seems to draw the very same electricity that the LV-N needs even if there is electricity available elsewhere on the vessel, so your "Prop" drops.

What is even odder in your screenshot is that the LV-N says its internal storage is full. Whenever I've had the same problem it has been at zero. And also it says 33.93% requirements met, but with me (IIRC) it has always been 50% (on one of a twin- LV-N vessel, so logical there).

I don't think it's the electricity.  LV-N generates electricity, it doesn't consume it.  And the ISRU-strangling problem occurs for other types of engines too, not just LV-Ns.

It's a bug that's been around since ISRU has, really wish they'd fix it.  I'm pretty sure they know about it, apparently it's just somewhat low on the priority list.

[NathanKell]

In fact we thought we *had* fixed it in 1.0.5. It passed our repro cases. >.>

(There was a bug in ALL_VESSEL and STAGE_PRIORITY_FLOW that led to that case.)

[BadOaks]

Hi Nathan, I just checked my version and it's 1.0.5.1028, so it looks like the bug is still alive and well. I just bought the game a week ago on steam and am loving it so far.

Edited January 6, 2016 by BadOaks

[Snark]

1 hour ago, BadOaks said:

Hi Nathan, I just checked my version and it's 1.0.5.1028, so it looks like the bug is still alive and well. I just bought the game a week ago on steam and am loving it so far.

Yup, as fate would have it I actually ran into it today, wasn't even trying to repro... just happened to have a two-engine ship and had forgotten that I'd left the ISRU on.