Tweakable fuel tanks

[PDCWolf]

By the way, the original tweakables promises were as my picture, not as the final product.

[LethalDose]

Being "Up in arms" is an overstatement of my original post. I am moderately disappointed in how they tweakables for tanks. The game is in development, and things can be change. I'd like them to be changed in a way that I think would improve gameplay, which is more important than realism. The purpose of the thread is bring the issues to the devs, and show that there is community support for the change.

I look at it this way, if I want to modify the fuel capacity or ad NOS to my car, I don't drop out the fuel tank, change its dimensions/add partitions and put it back. I add additional pre-made tanks to the trunk or other open spaces to my car and work on it that way. This is the same approach, but with rocket parts instead of car parts.

This example doesn't work. At all. Your car is mass-produced in a factory. Your car isn't assembled in the VAB or SPH. Your car doesn't land on Mars/Duna.

And beyond the fact that improving gameplay should universally trump realism, there are other, much more massive violations of reality in this game that pretty much render arguments of "realism" moot, for example:

• A star of Kerbol's size can't exist
  
• Kerbin is denser than lead
  
• Jet engines, rocket engines, and nuclear rockets all use the same "liquid fuel" resource
  

Those violations of reality are acceptable, but repartitioning fuel tanks is simply too fantastic?

Gameplay is not all that matters, but gameplay is paramount. Plenty of posters here pointed out how improving how tweakable tanks works would improve gameplay, and, again, that trumps "realism", especially in the face of the existing issues noted above.

So, back to the original point:

Myself and others would like to see the devs revise how tweakble tanks works to improve gameplay.

[InfinityArch]

@Wheffle: Nobody is suggesting that it would be easy to modify something like a Saturn V first stage tank to carry only fuel or oxidizer, but it would be doable, and to be completely honest, I don't particularly like the whole "put together from scraps" notion that many people seem to emphasize about KSP.

Furthermore, any complaints about "oh it would be difficult to code" are more or less invalidated by the fact that a mod has done this since before 0.23 was in development, and quite possibly since before SQUAD even started working on it. Now, while it's conceivable that doing it the way modular fuel system does it might be an issue on the dev's end for reasons to do with the game's architecture that wouldn't apply to a modder, but unless a mod or developer wants to confirm that's the case, I would assume there's no technical barrier to tweakables working like this, meaning SQUAD chose not to implement the ability to remove a tanks ability to carry liquid fuel or oxidizer to make more space for the other. Hopefully they're just not interested in diving into procedural modifications to parts just yet, and we might see something like this show up in an update with procedural fairings, heat shields, and so on.

[Firov]

Gameplay is not all that matters, but gameplay is paramount. Plenty of posters here pointed out how improving how tweakable tanks works would improve gameplay, and, again, that trumps "realism", especially in the face of the existing issues noted above.

Though arguably, it's not unrealistic in the least for us to reconfigure the internal geometry of fuel tanks. Indeed, I'd argue that it's unrealistic to have tweakables without that ability. After all, no space agency is going to design a launch vehicle with a large empty tank that they have no intention of using. It's wasted volume, and more importantly, wasted mass. In this case, adding realism would benefit the game play. It's a win/win.

[Anton P. Nym]

What too many people are forgetting here is that KSP is a game. Realism is nice, but not essential. Balance is essential... and that's something folks need to consider. If you do the stretchy tanks thing, what will the in-game role be for the stock tanks? Will it remove the design challenge involved in building a successful spaceplane? Conversely, will it make designing craft too difficult for newer players?

It may be simple to code, but that doesn't mean it's easy to implement in a game. There are other factors to consider.

-- Steve

[PDCWolf]

What too many people are forgetting here is that KSP is a game. Realism is nice, but not essential. Balance is essential... and that's something folks need to consider. If you do the stretchy tanks thing, what will the in-game role be for the stock tanks? Will it remove the design challenge involved in building a successful spaceplane? Conversely, will it make designing craft too difficult for newer players?

It may be simple to code, but that doesn't mean it's easy to implement in a game. There are other factors to consider.

-- Steve

You are forgetting everything in the game is doable without tweakables. User affinity of the game itself stays the same. As for implementation, it's already mostly done. It also doesn't remove any challenge (And they don't seem to care about this, just look at the rapier)

[Firov]

What too many people are forgetting here is that KSP is a game. Realism is nice, but not essential. Balance is essential... and that's something folks need to consider. If you do the stretchy tanks thing, what will the in-game role be for the stock tanks? Will it remove the design challenge involved in building a successful spaceplane? Conversely, will it make designing craft too difficult for newer players?

No.

Because we aren't talking about stretchy (aka procedural) tanks. This would still use all of the stock fuel tanks. It would simply allow more versatility in their deployment. Newer players wouldn't have to concern themselves with it at all, since the default values would remain exactly what they are now.

[Aragosnat]

It seems the OP is asking for a Mod tool to create and add custom fuel tanks in-game. While I don't blame the OP for wanting such and find it would be cool to have... The problem I'm seeing is we don't know what kind of space/volume rocket fuel and oxidiser takes up as well as the mass. As it stands we could have wierd volume preportions of 100:1 ratio (just an example on how it could be extreamly diffrent) or a ratio closer to being equal (which I realize is more likely the case). The current tweakables is a good start though and hopefully they will be able to expand upon it as well as standardize the fuel sizes.

[phunk]

Furthermore, any complaints about "oh it would be difficult to code" are more or less invalidated by the fact

... that none of the "internal tanks" actually exist in the game code. The part configs define what resource a part holds, and it would be no harder to make those tweakable than what they've already done.

If you want an X200-32 full of xenon or something whacky like that, it's trivial to create one. This took me about 2 minutes:

[LethalDose]

It seems the OP is asking for a Mod tool to create and add custom fuel tanks in-game. While I don't blame the OP for wanting such and find it would be cool to have...

No.

No, no, no, no.

No.

Just. NO.

This is not what I'm asking for. Not even a little.

I'm asking to change how the tweakbles work with tanks.

It's not custom tanks.

It's not a mod tool.

It's just a change to a feature that's the devs found it appropriate to add to the game.

[Psycix]

Resizing a fuel tank is not hard.

You use the same end caps, plumbing and intertank structure.

The only thing that is different is the length of the cylinder walls.

You can use the exact same joining techniques and assembly process. All that differs is the length of two cylindrical tubes.

[Eric S]

You are forgetting everything in the game is doable without tweakables.

Except that not everything is possible. The devs have stated that they planned on switching the atomic engine over to using liquid fuel only, but didn't want to have to duplicate all existing fuel tanks in LFO-only variants. Their solution was to wait until tweakables would allow them to use the same fuel tanks either way. Now, explain how this can be done in game still meeting their original specifications of not duplicating all the fuel tank parts without having tweakables be able to go beyond what we've seen so far.

[Alguien]

Honestly, is there any reason for why we won't be able to use the whole volumen of the tank? Realism sounds like a trash excuse when the game already ignores realism in many fronts and it feels like Squad just added the barebones feature and called it a day while the mod does more and better

[PDCWolf]

Except that not everything is possible. The devs have stated that they planned on switching the atomic engine over to using liquid fuel only, but didn't want to have to duplicate all existing fuel tanks in LFO-only variants. Their solution was to wait until tweakables would allow them to use the same fuel tanks either way. Now, explain how this can be done in game still meeting their original specifications of not duplicating all the fuel tank parts without having tweakables be able to go beyond what we've seen so far.

"You are forgetting everything in the game is doable without tweakables." means inside the game, like going to planets and stuff, you know, playing the game.

[Pbhead]

I do find it odd that they didnt take the time to make tanks tweakable, in the idea of an oxidizer only tank, because i find it odd that they didnt take the time to finally make nuclear rockets require special fuel (which, tanks can be tweaked to hold)

[LethalDose]

The problem I'm seeing is we don't know what kind of space/volume rocket fuel and oxidiser takes up as well as the mass. As it stands we could have wierd volume preportions of 100:1 ratio (just an example on how it could be extreamly diffrent) or a ratio closer to being equal (which I realize is more likely the case). The current tweakables is a good start though and hopefully they will be able to expand upon it as well as standardize the fuel sizes.

Just as an example, the densities of Liquid O2 and JP1 are pretty similar:

Density(JP1) = 0.81 kg/L

Density(L O2) = 1.14 kg/L

Ratio JP1:LO2 = 71%

Which is close enough for handwaving.

In all ways that already matter, the devs have already done this. They have to know what the weight of each unit of LF and Ox so they know how much weight is removed using the tweakables now.

Both liquid fuel and oxidizer have densities of 5 kg/L, based on the wiki. And it's safe to assume that is in liters because of how consumption is reported in active engines.

[GROOV3ST3R]

I don't understand why people say that it's ''unrealistic'' to be able to change sizes of tanks... The so called ''stock'' fuel tank represents a blueprint of a tank. You then adjust it to your needs and your specification and make it. What's so god damn unrealistic about that?

Maybe you can't alter existing tanks - but then you can just rip out the internals and manufacture new ones... IS that so far fetched?

[Eric S]

"You are forgetting everything in the game is doable without tweakables." means inside the game, like going to planets and stuff, you know, playing the game.

The problem with that logic is that since everything in game is already doable, it would apply to just about any suggestion/idea.

It also misses the fact that this is something the devs said they want to do. They want to make the atomic engine more realistic. If it weren't for spaceplanes or this planned nerva change, I wouldn't find the idea of taking tweakable fuel tanks to this level very useful.

[geb]

If you want an X200-32 full of xenon or something whacky like that, it's trivial to create one. This took me about 2 minutes:

This is exactly what I want, but more than that, I want it to be a stock option. It's just not as much fun to put up a post saying "Hey guys! Check out what I just did!" when you aren't using the same set of parts as everybody else.

Hauling monopropellant around in Jumbo-64 tanks would be fun too.

[csiler2]

Irrelevant car analogy aside, you must realize that the Saturn V you're talking about was engineered to achieve a specific mission. I've pointed this out before, but the engineers didn't haphazardly grab a few tanks, duct tape them together, and call it a day. The fuel tank ratios were specifically calculated to achieve it's mission. In this case, to be able to achieve orbit with the Apollo missions. It was then constructed to those design specifications. Had they realized in the design phase that they, for whatever reason, needed 20% more oxidizer and 20% less fuel in the first stage they would have adjusted the internal tank geometry to accommodate that alteration. They would not have thrown up their arms and said "Well guys, our pre-packaged ACME brand tanks are the wrong size, somebody better tell Kennedy that we've got to scrap the moon mission." NASA didn't operate that way, the Soviets didn't operate that way, and SpaceX doesn't operate that way.

Again, no one is asking for this to be changeable in flight. That would be completely unrealistic, I agree. However, in the design phase (AKA VAB/SPH), there's no reason that the internal tank geometry couldn't, and wouldn't, be modified to suit the particular mission that tank is intended for within the volume limitations of that particular tank.

Also, consider the possibilities of using a single tank holding liquid fuel, oxidizer, AND monopropellent as a service module, as was done with the Apollo missions. That's what tweakables should ideally allow.

My comments were purely from the construction side, not flight side.

My analogy is not irrelevant. As you pointed out, the Saturn V was designed to achieve a specific heavy-lift role. To that end, its tankage, engines, and electronics were custom made for each rocket in the series as NASA and contractors made small changes. That is not Kerbal Space Program. We take pre-built parts, slap them together and hit the go button for space.

Allowing tweakables to change the internal tank sizes goes against that pre-built mentality that the game is built around. I mentioned the car modifications because I feel this is a similar mindset. Most people don't go to a shop and custom-build their gas tank, even for one-of cars. They buy pre-built fuel cells and find a spot for them in the car. Need two kinds of gas? Then buy two cans, because it's a lot easier and cheaper than trying to split up the one you've already got.

That said, I am for allowing us to change what fuel types are allowed in each tank. You can store almost anything in a tank, assuming that it's been properly purged and filled according to spec (magic handwave), but I feel that changing the internal tank structure gets too far away from the pre-built mentality. If the developers do want to allow changing tank internals, then I hope it costs a boat-load of money, because it would balance out that kind of power.

Edited December 13, 2013 by csiler2
grammar

[Psycix]

But if you are building your own tanks anyways, it's not that hard to change the length of each can.

[csiler2]

Resizing a fuel tank is not hard.

You use the same end caps, plumbing and intertank structure.

The only thing that is different is the length of the cylinder walls.

You can use the exact same joining techniques and assembly process. All that differs is the length of two cylindrical tubes.

IRL rocket tank resizing would be an extremely difficult task. Just building the original Saturn stages required leaps in technology. It's a lot easier now that the techniques are established, but man, it's hard enough to resize things that don't need high PSI seals. I can't imagine doing it with the required precision and scale of a rocket.

Read chapter 6 and chapter 7 of Stages to Saturn if you want to know how those monsters were built.

Edit: Psycix - It's still more expensive to build your own can and ensure it meets spec than to buy a mass-built can that mitigates those costs through sheer production size. Besides, you aren't building your own can. You select one of the pre-built cans provided by KSP's VAB/SPH.

[Psycix]

I think we should stop looking at the Saturn V, and start looking at more modern applications, like the Falcon 9.

The first and second stage tanks of the Falcon 9 use the same design. Most of their parts are the same and the main difference is the length.

With construction techniques like that, changing the length is a piece of cake.

Source: http://en.wikipedia.org/wiki/Falcon_9#Common_design_elements

The Falcon 9 tank walls and domes are made from aluminum lithium alloy. SpaceX uses an all-friction stir welded tank, the highest strength and most reliable welding technique available.[28] The second stage tank of a Falcon 9 is simply a shorter version of the first stage tank and uses most of the same tooling, material and manufacturing techniques. This saves money during vehicle production.[28]

Edited December 13, 2013 by Psycix

[Comrade Jenkens]

With modern techniques resizing fuel tanks would be very easy. I've worked on submarines and parts were often modified very late in the process (including the pressure hull) and its not a very difficult change.

[csiler2]

Psycix, just because they share the same tooling doesn't mean that Space X can just rip the guts out and change the internal structure of their tanks willy nilly. They would probably need to sit down and go through the design process all over again and adjust the tooling to build the proper cylinder side lengths. Let's not forget they'll need to calculate and build properly sized expanders for the nitrogen or helium vessels that will maintain tank pressure. The advantage to their system is that they don't need separate production lines/facilities for each tank or can reshuffle production if machines on one of the tool sets are broken. That's a step towards the standardization route, not the custom innards route.