ClF3 as a replacement for Oxidizer

[Guest]

ClF3 can be stored in most ordinary structural metals, provided they are is a metal fluoride passivation layer present, which is a pretty standard thing for storing things this reactive, actually. If it involved quartz tanks nobody would have built an engine running on it (they did, and it was tested). It is possible, though hopefully not easy, to buy ClF3 cylinders. Handling and storage instructions for them are a rather interesting read.  It's actually used on industrial scale in nuclear fuel processing.

[KSK]

4 hours ago, Brikoleur said:

Thanks @KSK, that answers my main objection to having more fuel types.

That still leaves my secondary one however: what's the point? If all fuel and oxidant types can be produced with ISRU, then what gameplay benefit do the additional fuel types bring? As far as I can tell the only outcome is that you have to check that your fuel tank type matches your engine type, and refuelling missions become more fiddly since you have to haul up the correct types of fuel and build your tanker to match it. That... does not strike me as fun, just fiddly. It still violates KSP's "Lego principle" -- that almost any parts are compatible with each other. (There is one outlier already, the DAWN electric propulsion system -- and tediously long burns aside, that's the main reason I almost never use it.)

There is the progression that @Dragon01 discussed, but that can be perfectly well abstracted out as it is now -- to thrust, weight, and Isp, with higher tech levels unlocking more powerful and more efficient engines. 

That said, if the ISRU obstacle is removed, I could live with multiple fuel types -- it wouldn't be a showstopper, just a minor feature I dislike. 

---> There is one way I think fuel variety could become an engaging and interesting gameplay element, but that would require an entire new system and level of abstraction. Namely, let us be the engine designers. Instead of engines, give us engine parts: nozzles, combustion chambers, pumps, housings. Let us combine them as we see fit to make our own engines. Naturally you could still have a bunch of pre-built engines giving a similar selection as we have now. Fuel type would fit into this type of gameplay very well, and would give us the flexibility to make exactly the kind of engines we want. But that's a big new system, an entire gameplay dimension in fact, and I'm not sure it's realistic to ask for something like that.

Well the point is that not all fuels and oxidants can necessarily be produced with ISRU at a given location. Duna is pretty generous in that regard, giving you access to hydrogen, hydrocarbons and LOX but (again, assuming it's a decent Mars analogue)  it doesn't have easy access to nitrogen, so making hypergolics would be more difficult to flat out impossible to make, depending on how you implement it.

So, at least for propulsion systems, you'd have subsets of your Lego blocks that would be quite flexible to use around a given planet because you can generate the required propellant using ISRU. Using the rest of your propulsion systems would require you to bring the propellant with you from Kerbin, or somewhere else where you can manufacture it using ISRU. In this case, perhaps Ike has some locations which are rich in ammonia ice and can be mined to produce nitrogen based propellants. 

My feeling is that to make this work well, it would really need to be properly baked into the game design from the outset and would require a little less abstraction. As an illustrative, off-the-top-of-my-head example (so I fully expect one could poke holes in it), I would go with three propellant classes:  kerolox (aka LFO), hydrolox  (no direct KSP1 analogy) and hypergolics (functionally equivalent to monoprop in KSP 1). Each fuel has matching engines and tank types and each propellant type has distinct advantages and disadvantages in terms of cost, tank capacity, engine weight, thrust, ISP and ISRU requirements.  So it's a wee bit more involved than KSP1 but hopefully a bit more logical too because you're not trying to make some mysterious LFO run everything from SSME analogues to F1 analogues to tiny probe engines.

E.g.      Hydrolox.  Good ISP,  reasonable thrust, reasonable engine weight, poor tank capacity, expensive. Simplest ISRU with the raw material (water) available almost anywhere.
             Kerolox.  Reasonable ISP, reasonable thrust, good engine weight, reasonable tank capacity, reasonably priced. Moderately complex* ISRU with the raw materials in shorter supply than hydrolox, due to the need for water and carbon dioxide.
              Hypergolics.  Poor ISP,  relatively poor thrust, good tank capacity. Price and weight are inversely correlated, reflecting the fact that you can have pressure fed engines which are mechanically simple but heavier, or turbopump driven engines that are lighter but more complex, although this level of detail isn't directly exposed to the player. ISRU here is interesting and very situational. Icy moons have a decent chance of containing accessible ammonia ice (raw material for hypergolics), rocky planets and atmosphere-less bodies have almost no chance.

* complex in this context could refer to price, energy consumption or location in the tech tree.

Yes, that's a bit more fiddly than stock KSP1 but I don't think it's ridiculously over-fiddly either. Ideally it should mean that there's no 'obviously right' choice of engine for a given situation, so your designs don't feel too railroaded but some engines might need a bit of creative design work in the rest of the craft, or need more infrastructure in place to really shine.

Ultimately, I think whether you enjoy this sort of thing depends where you find your creativity. If, as I think it is for you (although please correct me if I'm putting words in your mouth here) , the 'Lego' aspect of KSP is really important and you want the maximum flexibility to use any engine for any purpose - then the kind of system I'm describing above probably won't be as appealing. However, if you're the kind of player that likes Career Mode because of the imposed design choices at different stages of the game (and I'm not being contrary here I don't think - I've seen that sentiment expressed plenty of times on this forum), then maybe that it would appeal.

Me - I'd find it to be a deeper and more engaging version of Career Mode that I'd find more fun than the current offering but reasonable players may reasonably disagree!

Edited October 1, 2019 by KSK

[harrisjosh2711]

@Brikoleur part proliferation is an issue for me as well. The best way to implement a variety of fuels is by slightly modifying ksp1 mechanics, texture/model variants for tanks/engines, tied to tech level. Which means you could still use every engine/tank to your hearts content. But, (game play mechanic here) you would need to send a probe and possibly a rover first to decide the best variant. Colonization is major selling point to ksp2. I exspect mining and isru to be a large part of that. If not wouldnt colonization be redundant, considering we have orbital construction yards and can transport supplies?

 

@Brikoleur part proliferation is an issue for me as well. The best way to implement a variety of fuels is by slightly modifying ksp1 mechanics, texture/model variants for tanks/engines, tied to tech level. Which means you could still use every engine/tank to your hearts content. But, (game play mechanic here) you would need to send a probe and possibly a rover first to decide the best variant. Colonization is major selling point to ksp2. I exspect mining and isru to be a large part of that. If not wouldnt colonization be redundant, considering we have orbital construction yards and can transport supplies?

 

[Guest]

2 hours ago, Dragon01 said:

A nuclear tug blows every space-oriented craft larger than a probe out of water, because the Nerv is just that good. If you're roleplaying anti-nuclear activists banning it, then it's the Vector. Only landers and spaceplanes have more than one viable design, and that's mostly due to aerodynamics being a tricky beast. Admittedly, part of the reason for all this is that KSP's toy solar system doesn't even really need all that extra performance LH2 can provide, but with more places to get to, this will stop being the case. With multiple propellants, even lifter design becomes much more interesting. 

I disagree. The Vector is only useful for very large craft, and the Nerv for large-ish craft (plus it's annoying to use because of the low TWR and consequently long burns). I don't think I've ever used a Vector for a deep-space craft, and I only end up using Nervs for a few exceptional missions, such as delivering an interplanetary space station or big base components. Most of my craft aren't big enough to justify it. My go-to engines for deep-space craft and landers are the Poodle, Terrier, and Spark, plus Wolfhound and Cheetah when I reach them.

2 hours ago, Dragon01 said:

Except that them being similar is a failure in Squad's part, and part of the problem I'm trying to fix here. Fuel tanks, for instance, should be visually distinct, according to their purpose (and in Nertea's mods, they are). Same with engines, most of them should have something unique about them, despite having an overall similar role.

If you have three types of fuel tanks, and they're provided in more or less the same form factors as currently, you're going to have a lot of fuel tanks. Same with engines: if you have three different fuel types, and a relatively broad range of sizes and powers for them, that's a lot of engines. Clustering would certainly help, but that would only slightly mitigate the problem, not actually solve it.

I still think a better solution would be to break down the engines into components which we can then combine to taste, with fuel type being one of the choices made when assembling the engine. Fuel tanks could be handled with part variants; cryo tanks of a given volume would have slightly lower capacity due to the insulation. 

Even so... yeah, I think it would be possible to make fuel types work and not be a chore, but I'm not convinced the gameplay payoff is worth the effort: it's a quite a lot of added complexity that ultimately doesn't really change all that much. But you have shifted my position, I'm no longer categorically against it, more neutral-negative. 

[harrisjosh2711]

@Brikoleur part proliferation is an issue for me as well. The best way to implement a variety of fuels is by slightly modifying ksp1 mechanics, texture/model variants for tanks/engines, tied to tech level. Which means you could still use every engine/tank to your hearts content. But, (game play mechanic here) you would need to send a probe and possibly a rover first to decide the best variant. Colonization is a major selling point to ksp2. I expect mining for fuels and isru to be a large part of that. If not, wouldnt colonization become redundant, considering we have orbital construction yards and can transport supplies? The only use i can think for a colony under this scenario is: if you, by choice, want to launch from outside the kerbol system. Generally, i buy a prequel because it comes with a new story. Ksp doesnt have a story. Therefore, without some signifigant changes i would view ksp2 more akin to dlc than a new game.

[FinalFan]

5 hours ago, Dragon01 said:

A nuclear tug blows every space-oriented craft larger than a probe out of water, because the Nerv is just that good. If you're roleplaying anti-nuclear activists banning it, then it's the Vector. Only landers and spaceplanes have more than one viable design, and that's mostly due to aerodynamics being a tricky beast. Admittedly, part of the reason for all this is that KSP's toy solar system doesn't even really need all that extra performance LH2 can provide, but with more places to get to, this will stop being the case. With multiple propellants, even lifter design becomes much more interesting. 

I am really surprised that you consider the Vector with its 315 isp to be some kind of overpowered beast for deep space craft.  I'm honestly dumbfounded, actually.  For me the Terrier/Poodle/Rhino triumvirate reign supreme in space among the stock LFO engines, with Cheetah and Wolfhound adding to the mix from MH.  What about the Vector makes it superior to these engines in vacuum in your estimation?  

For the NERV, I don't disagree nearly so much, but I still think you're overstating your case a bit.  Its weak thrust means multiple engines are needed for reasonable TWR on larger craft, which can be annoying and potentially design restricting.  For non-reusable craft, I imagine a staged LFO design might do at least as well as a NERV setup, though I must admit this is a bit outside my KSP experience as I have not done much yet with large, non-reusable interplanetary craft.  

And there's also career mode to consider.  Do you use 6 or 7 NERVs at 10k each, or one Skipper and extra fuel?  

Edited October 1, 2019 by FinalFan
snipped non-relevant parts of quote

[Guest]

2 hours ago, Brikoleur said:

If you have three types of fuel tanks, and they're provided in more or less the same form factors as currently, you're going to have a lot of fuel tanks. Same with engines: if you have three different fuel types, and a relatively broad range of sizes and powers for them, that's a lot of engines. Clustering would certainly help, but that would only slightly mitigate the problem, not actually solve it.

Note that for tanks, the modders already have a solution: part switching. Three types of fuel tanks could be combined into one part for each size, or perhaps lengths could be made switchable instead. With that, a well-ordered part list for fuel tanks only would, IMO, not be a big problem. Tanks, in particular, are a large contributor to a rocket's looks, and if nothing else, more tanks give you more aesthetic options. Especially if clustering them would be a viable approach, as well (though more for use as drop tanks, and an odd Saturn I, than as the primary means of getting large capacities).

Even without that, KSP2 will have to ramp up the tank inventory a lot. That interstellar craft they shown was gigantic, and to get decent size granularity (so that it doesn't go dinkier, dinky, small, big, gigantic), they're going to need a large lineup. So they really should find a way to make a large number of tanks easier to handle.

[Incarnation of Chaos]

7 hours ago, FinalFan said:

I am really surprised that you consider the Vector with its 315 isp to be some kind of overpowered beast for deep space craft.  I'm honestly dumbfounded, actually.  For me the Terrier/Poodle/Rhino triumvirate reign supreme in space among the stock LFO engines, with Cheetah and Wolfhound adding to the mix from MH.  What about the Vector makes it superior to these engines in vacuum in your estimation?  

For the NERV, I don't disagree nearly so much, but I still think you're overstating your case a bit.  Its weak thrust means multiple engines are needed for reasonable TWR on larger craft, which can be annoying and potentially design restricting.  For non-reusable craft, I imagine a staged LFO design might do at least as well as a NERV setup, though I must admit this is a bit outside my KSP experience as I have not done much yet with large, non-reusable interplanetary craft.  

And there's also career mode to consider.  Do you use 6 or 7 NERVs at 10k each, or one Skipper and extra fuel?  

70,000 is jack when you''re deep in career; my current workhorse rocket is around 250,000 when fueled. It's reusable and generally i get back around ~160,000 upon recovery; the upper stage isn't reusable and comes in at about ~15K. So for any launch i'm normally looking at burning 105,000 up in the atmosphere between the upper stage and fuel. The payload normally ends up being the most expensive portion; with me routinely launching 1M and 3M payloads on the stack. 

This all being said; NERVA upper stages aren't really a thing unless you're going interplanetary and planning on ISRU along the way.

In this case the raw efficiency of the NERVA engines, lack of larger electric options or any Xenon ISRU means that NERVA can't be beat. Even considering traditional chemical fuels can be used for ISRU; it's very difficult to break 9K with a single chemical stage (It is possible, mass fractions and all that) While approching 10K-11K with NERVA is relatively easy with 11 being the upper limit.

Now LH2 can be used to run NERVA's (Historically this was the ONLY fuel used) but the "Extra performance" gained by using it often gets obliterated by the extra tankage and volume resulting in needing more rocket to get it up into orbit in the first place. LH2 is also deeply cryogenic, GL keeping that cool without also adding a literal ton of extra weight.