There is no real reason, as it is now, to have fuel/oxidiser as seperate resources

[jf0]

In light of the facts:

1) All rocket engines currently use fuel and oxidiser in the same ratio and all rocket tanks hold it in this ratio

2) There is only one type of fuel and oxidiser (and I think it has been said before that adding different kinds is out of the question)

3) Jets and the nuke use only liquid fuel

4) There is no tank in the stock that can hold only oxidiser

5) all 'rocket proellant' tanks (with a couple of bizzare excepetions) have the same full to empty mass ratio

5) fuel and oxidiser have the same density - therefor the center of mass of a single tank never changes (in real life oxidiser and fuel are in seperate compartments that empty at different rates, so the center of mass will shift: in fact the way the game treats it now, fuel and oxidiser are seemingly stored mixed together in the tanks! :confused:)


There is absolutely no reason what-so-ever to have seperate fuel and oxidiser resources. There should just be one, 'rocket fuel' (along with liquid/jet fuel and mono-propellant). If different engines used different ratios, or there was a tank that held only oxidiser, or they were they were different densities, then it would make some sense or have some function.

What I think would be interesting is have different engines use different ratios, and fuel and oxidiser have different densities. Tanks would have a fixed volume and could be filled with any combination of fuel resources you want upto that volume (this is what would happen in real life anyway). But I'm certain this will [I]never[/I] happen in stock, so why not just scrap seperate fuel/oxidiser and have 'rocket fuel', 'jet fuel', 'monopropellant' etc? Edited November 23, 2015 by jf0

[Temstar]

Because there are situations where after SSTO spaceplanes deorbit itself it would still have some rocket fuel (read: correct mix of oxidiser and liquid fuel) left where it actually wants to use the liquid fuel for its air breathing engines to extend the atmospheric flight range, in addition to any pure jet fuel storage it has remaining after climbing to orbit.

Same with nukes. You miscalculated your liquid fuel requirement on your interplanetary mothership and now don't have enough fuel to get back to Kerbin? Siphon out the liquid fuel from lander tanks leaving behind just the oxidiser.

Back in the days when NTR used a standard chemical rocket fuel mix people were suggesting all day long here on the suggestion forum that we should have separate oxidiser and fuel so that NTR can use just fuel like their real life countepart so we can fine tune the oxidiser to fuel ratio on nuke spacecrafts.

[KerbMav]

[quote name='Temstar']Back in the days when NTR used a standard chemical rocket fuel mix people were suggesting all day long here on the suggestion forum that we should have separate oxidiser and fuel so that NTR can use just fuel like their real life countepart so we can fine tune the oxidiser to fuel ratio on nuke spacecrafts.[/QUOTE]

I am still onboard with that and would even go so far to introduce a seperate jet fuel - then ISRU would even be less like magic, as it could just be called water and not produce jetfuel.

[Red Iron Crown]

It used to be that way, just one resource that all LFEs and jets used. Then oxidizer was separated out and functional intakes were added, with liquid fuel being similar to kerosene that can work in either type of engine. Then 1.0 changed LV-Ns to run on LF only rather than LF+O, to more accurately simulate them.

I find getting the right mix of LF and O in spaceplanes to be an interesting challenge, I would be disappointed if they went back to the simpler system. I don't really see any benefit to switching to a single "rocket fuel" and "jet fuel", if anything it would reduce the utility of the tanks we have now.

[Wjolcz]

[quote name='Red Iron Crown']
I find getting the right mix of LF and O in spaceplanes to be an interesting challenge, I would be disappointed if they went back to the simpler system. I don't really see any benefit to switching to a single "rocket fuel" and "jet fuel", if anything it would reduce the utility of the tanks we have now.[/QUOTE]

Same.

[artwhaley]

I think it's probably best the way it is... but if I were going to change it, I'd change it in favor of a little MORE complexity - make different engines use different fuel ratios and make the fuel tanks fixed volume but all any ratio of fuel to oxidizer... so mission planning requires more thought on how much of each resource you need?

It could even be cool to add MORE fuel choices for different engines... so you would have craft design choices to make based on them. "Well, I could use these inefficient engines on my lander because they use the same type of fuel as my main engine so I can balance fuel back and forth as necessary once I reach my target.... or I could use this more efficient engine and not be able to transfer the excess over...."

Though, like I said, I think the way it is currently is probably best for the stock game... and both your simplification and my overcomplication could be accomplished pretty simply with a module manager script that changed the parts and a resource definition file update.

[Der Kosmos]

I'd separate jet fuel from Cryogenic fuel. Jets use jet fuel, First stage rocket engines use a mix of jet fuel and oxidizer. NTRs use Cryogenic fuel, and vacuum optimized rocket would use a mixture of cryogenic fuel and oxidizer. Cryogenic fuel tanks would also be less dense, and perhaps require electricity or bleed off propellant if they get too hot.

[Frozen_Heart]

The current system works well and is simple enough for newbs to get while showing that rockets use two different chemicals while jets only use one. The only thing I would change would be to make fuel and oxy have different densities.

[swjr-swis]

I would prefer to keep the separate LF/O as it is now. If you start down that route, there probably is a similar argument for doing away altogether with different fuels: why have separate jet fuel/rocket fuel at all? All engines just using 'fuel', period. I don't need KSP to be incredibly (credibly?) realistic, but let's not go too gamey either please.

I would however be all for fuelswitching of tanks to become stock.

Btw, it's simple enough to make an MM patch that makes the LF/O resources and LF/O-using engines behave the way you describe, without needing an actual plugin. So the choice is already there if you want this badly enough. Unlike fuelswitching, which requires a plugin to add that functionality.

Edited December 6, 2015 by swjr-swis

[A35K]

In addition to what others have mentioned, it is also useful to provide compatibility with many mods, such as interstellar, in which it is possible to produce both LF and Ox, but at different ratios.