Devnote Tuesdays: The "Let's Do the Time Warp Again" Edition

[Scoundrel]

I kind of feel a need to weigh in for some stupid reason...

Personally, I am not too keen about the whole equal fuel drain thing for several reasons:

1) The more parts that change weight means balancing becomes a little more challenging. The current way to build spaceplanes involves carefully placing tanks and plumbing them in such a fashion that you can control the COM as the tanks drain (stable for VTOLs, shifting for more controllable spaceplanes), then placing the wings to get the COL to where you need it. If the mass of the wings change as they drain fuel then you end up having to constantly mess around with your wings to get it to the point where the COL and COM stay where you want. It won't simplify engineering (unless the fuel is simply drained from all the wing bits), it'll actually complicate it unnecessarily as players try to figure out tricks to control when the wing tanks drain. The only way I see it not causing an issue for most spaceplane designers is if wings would be stageable for fuel flow control, or if they're going to make it so tanks can be added to action groups. Perhaps that is something the Devs intend, but I don't know.

2) Fuel draining from LFO tanks on spaceplanes is equally as critical since it means we're going to end up plumbing the wings with fuel lines anyways so that the rocket engines don't end up with tons of O and yet be starved for LF because of the initial ascent stage. Sometimes we build our spaceplanes specifically to drain tanks in a certain order just for that reason. Now, this might just be me thinking that wing fuel flow won't behave like a standard tank, so perhaps my concerns aren't valid, but for some reason I just can't shake the feeling that I'm going to be annoyed by this.

3) Payloads draining as the turbines fail to differentiate between payload and actual craft, thus messing with COM in addition to fuel management. This one may not bother some players (it would me, but nobody cares about me), and it isn't anywhere near an issue that points 1 and 2 are. It just means finicky preflight prep deactivating tanks so our spaceplanes don't drink the fuel intended for our refuelling stations (like RCS payloads) is mandatory.

So, on the whole, I'm not too thrilled about this. I will, however, give the Devs the benefit of the doubt and wait and see how this gets implemented as the QA team will likely have much to say about this when they test it, so it may end up being modified by the time it gets to general release.

[Tex]

Ohoho! Wet wings and even fuel draining! That is awesome, and I don't usually build spaceplanes!

[Red Iron Crown]

From the description of some of the prospective problems of even fuel drain it sounds like some of them could be sidestepped by disabling tanks as needed.

I've been using Goodspeed fuel pump for a while, and TAC fuel balancer before that, so my opinion of this feature may be a bit biased.

[TeMPOraL]

No. You need eleven.

I think this is the closest we'll get to SQUAD admitting Cthulhu plays KSP, and the Kraken is a fan-service character.

Ph'nglui mglw'nafh Cthulhu R'Laythe wgah'nagl fhtagn...

[Alshain]

And finally the thing which concerns me most of all. Space-planes tend to have not only LF tanks but LF+O. Air breathing engines draining evenly from all the tanks will lead to even more plumbing then currently.

I don't think this is going to be a big issue. Bearing in mind that air breathing engines consume so little fuel, your always going to have left over oxidizer unless you test and trim the tank contents down, the leftovers will just be spread evenly where as before they were in the rear tank.

It is going to make it quite a bit harder to trim the oxidizer down though. Instead of pulling it out of the foremost tank, you will now have to adjust the slider evenly on every tank on the plane.

In addition, if your using FAR you will now also be required to use a Fuel Pump mod as the built in interface would be too difficult to move the excess weight forward and back quickly as you move from sonic to subsonic since it will be spread amongst all the tanks. It was already pretty difficult to begin with, but now it will be nearly impossible.

Edited January 21, 2015 by Alshain

[HarvesteR]

I had that thought as well. However, I thought the choice of words: "I also revised the fuel flow logic for air-breathing engines" and "turbine engines now drain resources evenly from all tanks in a stage" was significant. It implies that the choice of engine determines the fuel flow, rather than fuel flow being determined by the resource. As such, 'turbine engines' could draw evenly from LF or LFO tanks.

Or I might be over-analysing...

That's actually quite right. The engine modules are now able to override the default flow logic as defined by the resource with their own, so even though turbines use the same module as SRBs and Liquid Engines, they set up their own flow logic for LiquidFuel, so that in their case, the lookup method used is the STAGE_PRIORITY method.

For other modules/propellant configs which don't define a particular method, the resource default is used.

As for the necessity that prompted this change, other than the improvement in long-term stability as tanks drain out, this is very much essential to support wet wings and drop tanks. Using the default stack-based flow logic means tanks in child parts (as wings tend to be) will be unaccessible unless a fuel line links them to some spot in the drainage route of the engines. Quite a chore for something that would be expected to just work.

And yes, closing off tanks does still work as always. If you don't want a tank being used, you can close the valves and it'll be left unused.

Cheers

[CaLVin-K]

A bit of topic but relevant none the less, would it be possible to select a fine print orbit as sort of a target in order to establish the ascending/descending nodes? This would be a great help in precisely lining up with target orbits and simplify the whole process. Thanks for the devnotes:D

[Red Iron Crown]

For reference, the STAGE_PRIORITY flow logic HarvesteR refers to is the same as that currently used for monopropellant, tanks in the same stage drain evenly, with "stage" being determined by the number of decoupler between the tank and the root part, no fuel lines necessary. (From memory, may be wrong about the decoupler thing)

[Nemrav]

Il enter this fuel flow debate, but, I'm not too great in my flight knowledge so have mercy on me when I get something wrong *picks up squirt gun*

Aren't we all assuming that these vessels have a fuel pump ? Rockets don't normally have them because gravity and velocity do the plumbing instead.

The same thing goes for planes, fuel drains downwards, to the bottom of the aircraft first (gravity) and then back (but not compressed back, due to a low-ish speed).

So, strictly for doing low altitude planes, wouldn't this be what you'd expect anyways ? Even early Hurricains had trouble due to not having a fuel pump.

Tweakables maybe ? set an option for one part and also have a button to "set config for all tanks in this stage" ?

Or of course we could have a fuel pump part to change this and make the realism party happy with something they didn't expect...

[Alshain]

Il enter this fuel flow debate, but, I'm not too great in my flight knowledge so have mercy on me when I get something wrong *picks up squirt gun*

Aren't we all assuming that these vessels have a fuel pump ? Rockets don't normally have them because gravity and velocity do the plumbing instead.

The same thing goes for planes, fuel drains downwards, to the bottom of the aircraft first (gravity) and then back (but not compressed back, due to a low-ish speed).

So, strictly for doing low altitude planes, wouldn't this be what you'd expect anyways ? Even early Hurricains had trouble due to not having a fuel pump.

Tweakables maybe ? set an option for one part and also have a button to "set config for all tanks in this stage" ?

Or of course we could have a fuel pump part to change this and make the realism party happy with something they didn't expect...

I don't think anybody has said a thing about realism. I don't know why it's always the "realism party". This is about gameplay and challenge. One of the plane building challenges is balancing the craft. To me it simply feels like dumbing down the game and eliminating the challenge. Like I said before it's not the end of the world or anything, there are those that argue maneuver nodes were the same, but you have the choice of not using those.

[FleetAdmiralJ]

That's actually quite right. The engine modules are now able to override the default flow logic as defined by the resource with their own, so even though turbines use the same module as SRBs and Liquid Engines, they set up their own flow logic for LiquidFuel, so that in their case, the lookup method used is the STAGE_PRIORITY method.

For other modules/propellant configs which don't define a particular method, the resource default is used.

As for the necessity that prompted this change, other than the improvement in long-term stability as tanks drain out, this is very much essential to support wet wings and drop tanks. Using the default stack-based flow logic means tanks in child parts (as wings tend to be) will be unaccessible unless a fuel line links them to some spot in the drainage route of the engines. Quite a chore for something that would be expected to just work.

And yes, closing off tanks does still work as always. If you don't want a tank being used, you can close the valves and it'll be left unused.

Cheers

Interesting explanation, and I generally don't have a problem with the change, but I do have some thoughts:

1) Drop Tanks - generally my idea for these is fuel would be used up in them FIRST and then dropped off (hence the name). But if fuel is removed evenly, wouldn't that defeat the purpose of even having them? Unless there is something I'm missing?

2) LF being drained evenly on jet engines, but then the fuel NOT being drained evenly on rocket engine assists into orbit seems like it could be a problematic issue. Or is that just something someone is going to have to keep in mind when designing planes?

[JimmyAgent007]

1) Drop Tanks - generally my idea for these is fuel would be used up in them FIRST and then dropped off (hence the name). But if fuel is removed evenly, wouldn't that defeat the purpose of even having them? Unless there is something I'm missing?

I think you are. If I understand correctly, you stage your drop tanks to drop at some point. So they get used first before the drop stage, then you let them go and then the plane uses everything else. So if you have tanks in the first stage, they drain, then 2nd stage, then 3rd and so on assuming you have that many stages.

[Rakaydos]

So basically, Jet engines now use Xenon/Monoprop fuel logic.

[FleetAdmiralJ]

I think you are. If I understand correctly, you stage your drop tanks to drop at some point. So they get used first before the drop stage, then you let them go and then the plane uses everything else. So if you have tanks in the first stage, they drain, then 2nd stage, then 3rd and so on assuming you have that many stages.

Yes, but you typically stage engines, not tanks, right? So you could have a decoupler on the tanks to have them in a different "stage" so does the plane use fuel from the farthest stage to the nearest stage if there are multiple stages then?

[JimmyAgent007]

Yes, but you typically stage engines, not tanks, right? So you could have a decoupler on the tanks to have them in a different "stage" so does the plane use fuel from the farthest stage to the nearest stage if there are multiple stages then?

Rockets stage engines, planes stage tanks. Thats the way I look at it. So if you have one set of drop tanks, then main tanks, you stage to turn on the engines, the next stage is to drop tanks so it drains them first, then drains the rest. The way I understand it is the answer is yes.

[pellinor]

I'm worried more about transferring fuel between vessels. Like between a Spaceplane with lots of wing pieces and a large space station, both having lots of small tanks. KSP still lacks a good interface to deal with many small tanks.

It might be useful to transfer fuels between stages (with docking ports also counting as seperators), each stage being accessible like a single large tank.

[Navy2k]

@Jim (Romfarer): Maybee you could check if dockingports having their "nondocking" side connected to another docking port or a decoupler. This indicates that there could be a docking port mounted the wrong way, and it would be nice to get a recomendation from the Engeeniers like: "There was found an unusual docking port configuration. Please check before launch."

- - - Updated - - -

It might be useful to transfer fuels between stages (with docking ports also counting as seperators), each stage being accessible like a single large tank.

I could live with having a button in the context menu of each docking port to "start/stop pump" and "in/out".

Greetings

Ben

[pellinor]

@Jim (Romfarer): Monoprop without RCS-Thrusters. I always forget to remove that stuff from the pod when I don't need it.

[klgraham1013]

That's actually quite right. The engine modules are now able to override the default flow logic as defined by the resource with their own, so even though turbines use the same module as SRBs and Liquid Engines, they set up their own flow logic for LiquidFuel, so that in their case, the lookup method used is the STAGE_PRIORITY method.

For other modules/propellant configs which don't define a particular method, the resource default is used.

As for the necessity that prompted this change, other than the improvement in long-term stability as tanks drain out, this is very much essential to support wet wings and drop tanks. Using the default stack-based flow logic means tanks in child parts (as wings tend to be) will be unaccessible unless a fuel line links them to some spot in the drainage route of the engines. Quite a chore for something that would be expected to just work.

And yes, closing off tanks does still work as always. If you don't want a tank being used, you can close the valves and it'll be left unused.

Cheers

Doesn't this mean that this could be modified in the config file? If so, couldn't there also be a toggle on the engine?

Also, Crossfeed Enabler seems to handle the wet wings fuel flow just fine. Not sure why Squad needed to implement a fuel balancer to solve the problem.

Honestly, I'm still not sure what I think about it. I'm not sure the argument that "it makes building simpler so it's bad" holds much water with me.

[monstah]

So if you ever decide to add in-flight Action Group editing without needing a Mod, you'll make a lot of folks incredibly happy.

Oh, so much. And a Delta-V reader would also be Golden.

[KerbMav]

Regarding fuel-flow, if the new logic respects locked fuel tanks - which can be a hassle to undo right before switching to rocket engines - than maybe there should be marker to indicate tanks available for jet engines/even draining? (Default on for all jet tanks, default off for LFO tanks.)

Alternatively this might be a reason to introduce jet fuel?

[Moon Goddess]

Just please make the Engineer report modable, I'd like TAC to be able to list when I don't have enough life support, or DRE to tell me I don't have heat sheilds.

[NFUN]

Don't know if it has been mentioned, but Squad should work on making it easier to click on the right part of an orbit when an intercept is achieved.

[bdito]

Jim (Romfarer): This week I’ve been focusing on the new Engineer’s Report app which will replace the Craft Info app. We are keeping everything in the old app, changing the app name and adding a new feature to it: Design Concerns. This is a list of possible problems for your vessel all ranging from simple possibly unimportant issues to crucial errors which will render your vessel unflyable. We already have a list of design concerns in the works but we are always looking for suggestions. So what are the things you “always†forget about when designing a vessel?

What the heck is the Craft Info app? Is it just the craft information at the bottom of the VAB/SPH?

[ArcFurnace]

What the heck is the Craft Info app? Is it just the craft information at the bottom of the VAB/SPH?

Yes, precisely. The one that tells you part count/mass. It's in the AppLauncher (the stock toolbar), so it's an app.