[WIP] Nert's Dev Thread - Current: various updates

[helaeon]

I agree too with making the structurally unsound tanks just that. Based on their current model too it would make sense they would have a ton of drag.

This probably won't be a ton of help but: I've thought stock-stockalike KSP wasn't so much about adherance to realistic numbers (like the 3% mass fraction) but illustrating to the player why we would do thing A instead of thing B. Why are NTRs interesting? Why is VASIMR interesting? Hydralox engines vs Kerosene? etc. What are the challenges to using these technologies, what are the trade offs? So, it seems stock should always be the baseline, then your "why" in the real world informs what the Kerbals' numbers need to be.  I think gameplay is always #1 with those above points in mind. What you call it, kind of doesn't matter. Whether the MPDT uses hydrogen or lithium, really doesn't matter. What matters is that you use a different fuel with a different mass or density because for the point of the technology to get across you need to and balancing against other parts that use the same resource doesn't work.

Yes this does sometimes allow some insane ships that there is no way could work in the real world -but that's KSP in general. Unfortunately those kinds of things happen when you're dealing with physics/technology that's different from our world even if just a little bit.

[Streetwind]

9 hours ago, Nertea said:

A thought - what if VASIMRs could no longer use LH2 as a fuel and MPDTs used lithium?

That would allow you to balance the LH2 tanks for NTRs alone, yes. However, you'd still have the problem that as soon as you install CryoEngines, you have a cross-mod exploit because NF tanks are so much better than the fuel-switchable stock tanks. I mean, you don't necessarily have to care that an exploit exists, but it is what it is

 

6 hours ago, Captain Sierra said:

Cryo Engines
If NFP hydrogen tanks cannot be properly balanced to encourage vacuum-only use (low impact tolerance, low heat resist, higher drag if possible), then the next best option in my opinion is to simply not enable fuel switching on those tanks.

Fuel switching on NFP tanks is not the issue, really. You can still switch stock tanks to full oxidizer mode, and then use NFP's tanks to provide pure LH2.

Re: calls to make NF hydrogen tanks somehow worse in the atmosphere:
That is not only extremely difficult to get right, but it also does not fix the cross-mod problem. CryoEngines also has vacuum engines with very high Isp. The credo of CryoEngines is "offers an alternative to, but does not completely replace, stock engines". But in space, you could use NFP's higher mass ratio tanks just fine - and the stock engines would become completely outclassed. Additionally the vacuum engines would encroach on LV-N territory due to having significantly less dry mass and much better TWR while still providing more than enough dV to get around KSP's tiny solar system.

And for the crowd that likes nods to realism: this would actually be the opposite of how it is IRL. Launch vehicle grade LH2 tanks have very good mass ratios, like pretty much all other launch vehicle grade tanks. It's in space, outside of the atmosphere, where real life LH2 tanks suddenly become extremely awful, because at that point you have to start thinking about long-term storage, and LH2 really doesn't want to be stored long-term. (Fun fact: yes, that makes IRL NTRs a lot worse than most of the space geeks think they are. The sobering realization that chemical engines are actually an equivalent or better option for many mission profiles than the LV-N with the hydrogen NTRs patch is technically perfectly realistic, it just isn't suitable for a game like KSP.)

As such, this is not a thing I would consider worthwhile doing.

 

Edited December 5, 2015 by Streetwind

[Nertea]

Helaeon really has the total sum of what I want from everything in his post. I don't particularly care about matching RL numbers, but I would like to match RL challenges in some simplified ways. In my ideal world, every new component in the mods has a specific RL-related challenge associated with it that you have to solve to use it with efficiency. With CryoEngines, it's supposed to be tankage size for the fuels. With reactors, it's heat management... etc. Some of these lead to other challenges (now you have an NEP setup, it has the low TWR challenge). 

So I guess to take this down to basics - what are the design challenges associated with the various combinations of NFP, CryoEngines and the LH2 NTRs?

• Gridded thrusters (Xe): cost
• Hall thrusters (Ar): basic, not a challenge?
• VASIMR (Ar/LH2): ?
• PIT (Ar): heat?
• MPDTs (LH2): extreme power requirements
• CryoEngines (LH2/OX): tankage volume
• NTRs: stock makes the challenge engine mass and heat, which I'm not fully liking
• Xe as a fuel: cost
• Ar as a fuel: basic, not a challenge?
• LH2 as a fuel: tankage volume
• [Li as a fuel?: volatility?]

What are your thoughts on this? I think knowing this would help us work towards a common set of goals for the mods.

A quick skim of the list too:

LH2 tanks copying values from ZBO tanks: Interestingly, not actually a thing. It just ended up this way... I really didn't look at any values when determining this.
LH2 tank drag: This is cool, but as Streetwind points out, it only solves a bit of the problem.
Tank costs: fuel costs are the main component - they are CRP based and I would like to keep them that way. They are relatively "correct", that is, they're ratio-correct to an LF-Kerosene equivalency. Tank dry costs are totally open to fiddling with though
Tank dry mass consistency within a fuel: Yes this is not a problem and I support it, I only need to decide on values to use. 
Tank dry mass consistency between fuels: I don't really like this but the argument made is good. I would say go halfway... chemical fuels could have one similar set of numbers and "electric" fuels another.
Keeping the hydrogen NTR patch: Yes. I just want it  Don't ask me to justify!
Lithium for MPDTs: The reason I suggeted this was that 1) I already have some models. 2) It removes one "issue", which is working an electric engine balance thing into a chemical fuel. 3) I planned to do this when I released the fusion pulse propulsion models I made a while ago. It's also the canonical fuel from the test articles that originally inspired the models.

 

[billkerbinsky]

22 minutes ago, Nertea said:

• VASIMR (Ar/LH2): ?

Tankage volume (LH2); extreme power; low-ish TWR once you add reactors or acres of solar; otherwise, reward for slogging deep into the tech tree

[billkerbinsky]

1 hour ago, Nertea said:

Keeping the hydrogen NTR patch: Yes. I just want it  Don't ask me to justify!

How about a fuel-switching variant that allows you to choose (for the solid-core NTR's) between stock liquid fuel at an ISP of around 400-500s and H2 at an ISP of 900s; this (roughly) reflects what you'd get if you attempt to put heavier atomic-weight reaction mass through a solid-core NTR...

[Fraz86]

Quote

• VASIMR (Ar/LH2): ?

The VASIMR's challenge ought to be devising creative mission profiles to capitalize on its versatility. It should never be the optimum choice for any single application, and thus should only be worth using if you can find ways to take advantage of its ability to fill multiple roles.

Quote

Lithium for MPDTs: The reason I suggeted this was that 1) I already have some models. 2) It removes one "issue", which is working an electric engine balance thing into a chemical fuel. 3) I planned to do this when I released the fusion pulse propulsion models I made a while ago. It's also the canonical fuel from the test articles that originally inspired the models.

I'm a bit leery of adding another ion fuel, due to concern for part clutter and lack of benefit to gameplay. It already feels like there isn't a big difference between Xe and Ar other than cost (which is kind of boring). Especially if all "electric" fuels are conformed to a single dry mass ratio, I worry it will be difficult to create meaningful and interesting differences between fuel types. That said, if you could outline what might set Li apart as an interesting fuel, I could certainly change my mind.

Edited December 5, 2015 by Fraz86

[Streetwind]

2 hours ago, Nertea said:

So I guess to take this down to basics - what are the design challenges associated with the various combinations of NFP, CryoEngines and the LH2 NTRs?

• Gridded thrusters (Xe): cost
• Hall thrusters (Ar): basic, not a challenge?
• VASIMR (Ar/LH2): ?
• PIT (Ar): heat?
• MPDTs (LH2): extreme power requirements
• CryoEngines (LH2/OX): tankage volume
• NTRs: stock makes the challenge engine mass and heat, which I'm not fully liking
• Xe as a fuel: cost
• Ar as a fuel: basic, not a challenge?
• LH2 as a fuel: tankage volume
• [Li as a fuel?: volatility?]

What are your thoughts on this? I think knowing this would help us work towards a common set of goals for the mods.

Well the gridded ion thrusters have the lowest TWRs eve among the electric engines. The hall thrusters are better in that regard, but have subpar Isp. The VASIMR is intentionally understatted to balance its versatility (ironically, the unexpectedly high mass ratios on hydrogen tanks effectively nullified that in the current version). NTRs, you probably can't much get around having dry mass as a major downside, because nuclear reactors simply are absurdly heavy...

 

2 hours ago, Nertea said:

LH2 tanks copying values from ZBO tanks: Interestingly, not actually a thing. It just ended up this way... I really didn't look at any values when determining this.

Really? Wow. I could have sworn you did, because you literally hit the mass ratio number from the NASA Mars-with-NTR concept document to the second decimal

 

2 hours ago, Nertea said:

Tank dry mass consistency between fuels: I don't really like this but the argument made is good. I would say go halfway... chemical fuels could have one similar set of numbers and "electric" fuels another.

Yeah, I didn't mean to make everything 8:1 like stock LFO tanks. There's certainly room for variation. For example, xenon and argon can share one ratio, and if LH2 is no longer used by any electric engines, it can do its own thing. As long as the NTR performance ends up similar to stock through a combination of engine stats and tank mass ratios, the player doesn't actually need to look at the tanks. You could even have lithium deviate from xenon and argon as well, if the lithium tanks specifically point out that they are "much better/worse than xenon and argon", and the MPDTs can be balanced accordingly (subjectively they are already outliers, with their giant power draw). Ultimately, that means that despite all the different fuels, the amount of tank mass cross-referencing the player must do is not that large, and that should be acceptable. After all, this is KSP, and the players should be used to complexity

 

Edited December 5, 2015 by Streetwind

[Psycho_zs]

I'm also against adding another fuel. But if you decide to do so, MPDTs could use both hydrogen and lithium, with lithium being more efficient choise for them.

 

[riocrokite]

To add another perspective to the discussion,

I'm working on a basis for my low-tech isru propellants mod which is called 'fuel and isru rebalance'. It is basically reworking fuel mix ratio to 3:1 (Ox:LF) for stock engines and also removing the ability to make anything else than oxidizer from ore by stock ISRUs (vel recent nasa isru papers).

So player can refuel just oxidizer (75% fuel mass) using ISRUs thus increasing lf/lox effective isp by 53% (1 refuel) or 86% (2 refuels). If we take the best isp engine (350) and do 1 or 2 refuels the effective isp will still be much lower than LV-N (535 or 651 isp). Even lox augmented mode for NERVA by porkjet with refuel ability (3:1 ratio, 1 refuelling with isp bumped to 500 will be around 765) will still be below stock LV-N isp.

Thus I'm thinking about switching stock LV-N in my mod to other fuel (CRP LH2) and heavier tanks (or otherwise nerfed tanks) since currently it's just too good even if one cannot refuel it.

Edited December 6, 2015 by riocrokite

[billkerbinsky]

3 hours ago, riocrokite said:

... removing the ability to make anything else than oxidizer from ore by stock ISRUs (vel recent nasa isru papers).

Got a link for the paper?   (There is a plan to include a widget to produce O2 from the Martian atmosphere on the next NASA rover in 2020 as an ISRU test; IIRC the generated oxygen wouldn't actually be used for anything.  Other ISRU proposals involve hauling H2 to Mars and combining it with atmospheric CO2 via the sabatier reaction to produce methane, but modelling that starts to creep into RealFuels-level detail..

 

[Captain Sierra]

On 12/5/2015, 3:58:08, Nertea said:

• Gridded thrusters (Xe): cost
• Hall thrusters (Ar): basic, not a challenge?
• VASIMR (Ar/LH2): ?
• PIT (Ar): heat?
• MPDTs (LH2): extreme power requirements
• CryoEngines (LH2/OX): tankage volume
• NTRs: stock makes the challenge engine mass and heat, which I'm not fully liking
• Xe as a fuel: cost
• Ar as a fuel: basic, not a challenge?
• LH2 as a fuel: tankage volume
• [Li as a fuel?: volatility?]

What are your thoughts on this? I think knowing this would help us work towards a common set of goals for the mods.

To hit these in order:

-Cost
-Basic
-low TWR (due to high power generation mass)
-Power requirement/heat (requires lots of power for decent TWR, engine also outputs high heat at higher thrusts)
-Extreme power requirement
-Boiloff*
-Engine mass/TWR (Engine mass should only become a limiting factor when many are in use but just a few will suffer from TWR issues. TWR, however, is comparatively high when we consider we're comparing against electric engines. Heat shouldnt be much of an issue with a properly engineered heat piping system & radiator array hint hint)
-Cost/weight (heavy, but provides best dV per mass, volume, and cost. More dV per tank because of density & engine efficiency makes xenon a competitive high efficiency option)
-Basic (entry level electric engine fuel. Expensive, but isnt everything with this tech? Not stand-out in any way.
-Tank mass ratio/volume (low mass propellant requires gratuitous tankage to provide sufficient dV. Should be comparatively low cost for this reason)
-Solid core MPDTs? (Having alternate MPDTs that do not required tanked reaction mass but have a hard-limited burn time would be interesting. High cost makes reusability a key factor in this mod and throwing that away to remove the need for lots of fuel tankage could create some interesting gameplay decisions)

Spoiler

*This one is tricky since LH2 boiloff would throw a wrench into NTRs and MPDTs. My solution is as follows: Boiloff is only true for LH2 contained in stock tanks. NFP tanks include Insulation^tm to prevent boiloff. This does not fix the exploit of NFP LH2 tanks plus stock all-oxidizer tanks but if someone is willing to balance the fuel ratios on a setup like that, I think they've earned the right to abuse that.

 

On 12/5/2015, 3:58:08, Nertea said:

A quick skim of the list too:

LH2 tanks copying values from ZBO tanks: Interestingly, not actually a thing. It just ended up this way... I really didn't look at any values when determining this.
LH2 tank drag: This is cool, but as Streetwind points out, it only solves a bit of the problem.
Tank costs: fuel costs are the main component - they are CRP based and I would like to keep them that way. They are relatively "correct", that is, they're ratio-correct to an LF-Kerosene equivalency. Tank dry costs are totally open to fiddling with though
Tank dry mass consistency within a fuel: Yes this is not a problem and I support it, I only need to decide on values to use. 
Tank dry mass consistency between fuels: I don't really like this but the argument made is good. I would say go halfway... chemical fuels could have one similar set of numbers and "electric" fuels another.
Keeping the hydrogen NTR patch: Yes. I just want it  Don't ask me to justify!
Lithium for MPDTs: The reason I suggeted this was that 1) I already have some models. 2) It removes one "issue", which is working an electric engine balance thing into a chemical fuel. 3) I planned to do this when I released the fusion pulse propulsion models I made a while ago. It's also the canonical fuel from the test articles that originally inspired the models.

To hit some of these too.

Tank Costs: Given how far off KSP is from reality, we cannot assume the economic structure of kerbal society anywhere mimics ours, or that resource availability does either. I think fuel costs are a solid balancing tool. Fuel cost as well as tank dry cost are two different components that can be used to balance things. Example: LH2 is cheap but the tankage is expensive because you'll be refuelling it a lot and you want to encourage reusing infrastructure or recovery rather than single use.

Tank dry mass consistency between fuels: I dont particularly mind this change. I dont think its overly necessary but as long as you dont go to the atrociously heavy stock standard, I have no objections.

Keeping the hydrogen NTR patch: I think I have a better solution. Instead of trying to force an existing part balanced to a completely different paradigm to convert to your system, why not make some purpose built NTRs? You showed us a long while ago some hand sketches of gloriously badass rocket engines. I'd happily use those if only for their superior appearance. Your own NTRs can then be balanced from ground up around using LH2 and being competitive, rather than trying to pigeonhole already-existing items into the same role. Also, Near Future NTRs would be a great concept since technological extrapolation could put them as high as 1400Isp (which should more than compete with the LV-N even burning hydrogen).

Lithium for MPDTs: Again I think the solution here is more options, rather than changing the existing. (If you want to move the existing models to the new parts and whip up some new hydrogen MPDT models thats cool too, up to you). Adding solid core MPDTs, as I outline above, has the potential to create a very interesting tradeoff of a magnitude yet to be seen with any other thruster type.

[Streetwind]

3 hours ago, Captain Sierra said:

Keeping the hydrogen NTR patch: I think I have a better solution. Instead of trying to force an existing part balanced to a completely different paradigm to convert to your system, why not make some purpose built NTRs? You showed us a long while ago some hand sketches of gloriously badass rocket engines. I'd happily use those if only for their superior appearance. Your own NTRs can then be balanced from ground up around using LH2 and being competitive, rather than trying to pigeonhole already-existing items into the same role. Also, Near Future NTRs would be a great concept since technological extrapolation could put them as high as 1400Isp (which should more than compete with the LV-N even burning hydrogen).

Does not work out. It simply gives the player the utterly confusing scenario where they go "wait, so you want me to research this technologically advanced NTR, which comes later in the tech tree, costs more than the stock one, requires dedicated new tanks that also cost extra to unlock and are both more expensive and far less convenient to use than stock tanks... and gives me less dV, despite having 600s Isp more? What the...?"

Yep, less dV. 1,400s Isp is not enough to reach parity to the stock LV-N's 800 Isp, if you use a mass ratio of 3 for the tanks compared to stock 8. You need a minimum of 15,100s to reach parity, and thus a minimum of probably 1,800s to have a meaningful advantage that's worth the investment and the downsides of the much larger, much more expensive tankage. And every increase in Isp just increases the player's confusion.

No, I could imagine something more like this...

Current Poodle: 250 kN, 350s, dV ceiling ~7,100m/s, TWR ~14.5, using LF/O (mass ratio 8:1)
Current LV-N: 60 kN, 800s, dV ceiling ~16,300m/s, TWR ~2.0, using LF (mass ratio 8:1)
Patched LV-N, mode 1: 180 kN, 550s, dV ceiling ~11,200m/s, TWR ~6.0, using LF (mass ratio 8:1)
Patched LV-N, mode 2: 90 kN, 1,100s, dV ceiling ~15,000m/s, TWR ~3.0, using LH2 (mass ratio 4:1)

Design Reasoning:
- New engine option in the middle large TWR and Isp gap between the stock LV-N and the stock chemical engines; also further differentiates LV-N from electric engines
- LH2 tanks still feel markedly different from stock LF tanks when given a mass ratio of 4:1; this of course implies such a number does not cause issues with electric engines
- Drop in dV ceiling in LH2 mode compared to stock LF is balanced out with thrust bonus, but with the price and volume of LH2 tankage factored in, is still ostensibly a nerf vs. stock
- The mode 2 stats could probably stand alone, but the multimode thing is interesting?
- Doubling/halving of various values as tradeoffs between modes is easily understood by the player
- Downside: all other modded NTRs that the patch should affect will require a complete stat redo for potentially two modes each
- Individual values are over-the-thumb, open for tuning

 

3 hours ago, Captain Sierra said:

My solution is as follows: Boiloff is only true for LH2 contained in stock tanks. NFP tanks include Insulation^tm to prevent boiloff.

If I recall correctly, Nertea has been very disinterested when asked about implementing boiloff in the past.

 

Edited December 7, 2015 by Streetwind

[Streetwind]

I just had another thought. Come KSP v1.1, we'll have the "KSPedia", where we can add help and info pages. We could use that to give the player a primer on the different fuels, explaining roughly what they can expect from engines that use any given fuel, and even point out the mass ratios.

For example:

"Xenon is a high performance fuel for electric engines, especially when it comes to Isp. However it is also very expensive, making it unwise to burn through large amounts of it. Engines using argon will be a bit less efficient, but the much lower price point ensures that higher thrust rates, which go through comparatively larger amounts of fuel, do not become prohibitively uneconomical. Both of these gaseous propellants come in tanks with low mass ratios of 2:1."
"Liquid hydrogen is the economy fuel of choice for nuclear thermal rockets, due to hydrogen having the lowest molecular weight of all possible propellants, which results in the highest exhaust velocity. Unfortunately, hydrogen's exceptionally low density results in comparatively large and unwieldly tankage, even when the propellant is cryogenically liquefied. Due to the sheer size and extra insulation required, the mass ratio of these tanks is somewhat worse than normal liquid fuel tanks, at 4:1."

And so on and so forth. This is just a first brainstorm draft, with example numbers. Exact wording is up for debate, too, and a more noticable difference between xenon and argon engines can, if/where necessary, be implemented to match.

Of course, this is something for KSP v1.1 only, which may not be here until January or February. Perhaps the whole tank dry mass redo is best left for that version, while a simple bugfix update for 1.0.5 will suffice. Oh, that reminds me, I'll toss another minor bug up on github later, which I had forgotten until now.

[Nertea]

11 hours ago, Streetwind said:

Does not work out. It simply gives the player the utterly confusing scenario where they go "wait, so you want me to research this technologically advanced NTR, which comes later in the tech tree, costs more than the stock one, requires dedicated new tanks that also cost extra to unlock and are both more expensive and far less convenient to use than stock tanks... and gives me less dV, despite having 600s Isp more? What the...?"

Yep, less dV. 1,400s Isp is not enough to reach parity to the stock LV-N's 800 Isp, if you use a mass ratio of 3 for the tanks compared to stock 8. You need a minimum of 15,100s to reach parity, and thus a minimum of probably 1,800s to have a meaningful advantage that's worth the investment and the downsides of the much larger, much more expensive tankage. And every increase in Isp just increases the player's confusion.

No, I could imagine something more like this...

Current Poodle: 250 kN, 350s, dV ceiling ~7,100m/s, TWR ~14.5, using LF/O (mass ratio 8:1)
Current LV-N: 60 kN, 800s, dV ceiling ~16,300m/s, TWR ~2.0, using LF (mass ratio 8:1)
Patched LV-N, mode 1: 180 kN, 550s, dV ceiling ~11,200m/s, TWR ~6.0, using LF (mass ratio 8:1)
Patched LV-N, mode 2: 90 kN, 1,100s, dV ceiling ~15,000m/s, TWR ~3.0, using LH2 (mass ratio 4:1)

Design Reasoning:
- New engine option in the middle large TWR and Isp gap between the stock LV-N and the stock chemical engines; also further differentiates LV-N from electric engines
- LH2 tanks still feel markedly different from stock LF tanks when given a mass ratio of 4:1; this of course implies such a number does not cause issues with electric engines
- Drop in dV ceiling in LH2 mode compared to stock LF is balanced out with thrust bonus, but with the price and volume of LH2 tankage factored in, is still ostensibly a nerf vs. stock
- The mode 2 stats could probably stand alone, but the multimode thing is interesting?
- Doubling/halving of various values as tradeoffs between modes is easily understood by the player
- Downside: all other modded NTRs that the patch should affect will require a complete stat redo for potentially two modes each
- Individual values are over-the-thumb, open for tuning

 

If I recall correctly, Nertea has been very disinterested when asked about implementing boiloff in the past.

 

Yeah I've actually already built an entire set of configs to do this (some time ago), but with the change that the high thrust low Isp mode was LH2/Ox. I stopped doing that because... I think I was busy. Something like that is probably a good idea. However I think I'd also like to slightly modify the mass of the LV-N downwards as well.

I don't like boiloff due to 2 reasons: 1) not transparent to player 2) thermal systems is still not very transparent in behaviour. 1.05 core heat is getting better (tanks could specify a need to keep their core at like 15K or something). The problem is as always knowing how many radiators are needed, which is hard to gamify properly. If anyone has really awesome ideas here I can think about it but that is not something I would do for a 1.05 era update. 

10 hours ago, Streetwind said:

I just had another thought. Come KSP v1.1, we'll have the "KSPedia", where we can add help and info pages. We could use that to give the player a primer on the different fuels, explaining roughly what they can expect from engines that use any given fuel, and even point out the mass ratios.

For example:

"Xenon is a high performance fuel for electric engines, especially when it comes to Isp. However it is also very expensive, making it unwise to burn through large amounts of it. Engines using argon will be a bit less efficient, but the much lower price point ensures that higher thrust rates, which go through comparatively larger amounts of fuel, do not become prohibitively uneconomical. Both of these gaseous propellants come in tanks with low mass ratios of 2:1."
"Liquid hydrogen is the economy fuel of choice for nuclear thermal rockets, due to hydrogen having the lowest molecular weight of all possible propellants, which results in the highest exhaust velocity. Unfortunately, hydrogen's exceptionally low density results in comparatively large and unwieldly tankage, even when the propellant is cryogenically liquefied. Due to the sheer size and extra insulation required, the mass ratio of these tanks is somewhat worse than normal liquid fuel tanks, at 4:1."

And so on and so forth. This is just a first brainstorm draft, with example numbers. Exact wording is up for debate, too, and a more noticable difference between xenon and argon engines can, if/where necessary, be implemented to match.

Of course, this is something for KSP v1.1 only, which may not be here until January or February. Perhaps the whole tank dry mass redo is best left for that version, while a simple bugfix update for 1.0.5 will suffice. Oh, that reminds me, I'll toss another minor bug up on github later, which I had forgotten until now.

Yes, this will be very useful, we'll be able to document a lot of useful things. 

I would like to adjust the tanks now. The update to NFE is almost done so they should release together. What should the numbers look like for Ar? I think it's good to have them a little worse than 

I'll shut up about lithium as it seems a very unpopular thing, but some last notes:

• Would replace LH2 completely (no more LH2 tanks in NFP) so we could treat everything separately. No more NTR patch for NFP at all (comes back somewhere else). 
• Is not a solid core MPDT, it's vaporized lithium.
• The more I think about it, the more I like it, but I guess it is fuel count creep. Unless something more unique is acquired I guess there's no point. 

[Streetwind]

I have no problem with the lithium. And well, if people complain about too many fuels, and you remove one while adding one, there's not really anything to complain about, right? Plus it's your mod, do what the heck you like 64bit native client is coming soon anyway!

As far as values for tanks, I'm tending towards xenon and argon having the exact same mass ratio - let's just aim for 2:1 right now. Realworld tanks are higher than that, but then again, realworld LFO tanks are also higher than what stock KSP has. Both are gas tanks, so matching ratios are believable to the player (whereas a minor difference in favor of one or the other probably won't be understood for what it is meant to signify). Also, right now the engines are in perfect balance for that, performance wise. Fuel cost is yet unaccounted for, but it's been that way since the introduction of argon, and nobody died In a future pass with the KSPedia available to explain, the engines themselves can be differentiated more depending on fuel type; for example, xenon engines could be allowed to exceed the balance target slightly, but only via means of increased Isp or something.

And vaporized lithium, how would that be stored in tanks? Is that also a gas/aerosol? Depending on how it's stored we can make a rough guesstimate for a suitable mass ratio. Unfortunately I know nothing about lithium in electric engines. What I do know is that lithium has a beautiful, rich crimson glow in a flame (670nm wavelength). Not sure if highly charged lithium from an electric engine emits the same spectrum, but how do you feel about tweaking the current white-purplish color of the MPDT exhaust to something like this? Having a spacecraft in the dark illuminated by that engine glow - like so, but red - would be pretty badass. Though I understand if that eats too much time.

If the VASIMR loses its hydrogen mode and becomes single-fuel argon, I'm going to un-nerf it a little bit because it is less versatile than before. I'll ponder suitable numbers and pass em to you once you've finalized everything (and maybe provided a test build, if lithium does make a grand entrance).

If no lithium, I suppose you'll have to dig up that half-finished patch draft you mentioned and we can finish it together.

[Nertea]

1 hour ago, Streetwind said:

I have no problem with the lithium. And well, if people complain about too many fuels, and you remove one while adding one, there's not really anything to complain about, right? Plus it's your mod, do what the heck you like 64bit native client is coming soon anyway!

As far as values for tanks, I'm tending towards xenon and argon having the exact same mass ratio - let's just aim for 2:1 right now. Realworld tanks are higher than that, but then again, realworld LFO tanks are also higher than what stock KSP has. Both are gas tanks, so matching ratios are believable to the player (whereas a minor difference in favor of one or the other probably won't be understood for what it is meant to signify). Also, right now the engines are in perfect balance for that, performance wise. Fuel cost is yet unaccounted for, but it's been that way since the introduction of argon, and nobody died In a future pass with the KSPedia available to explain, the engines themselves can be differentiated more depending on fuel type; for example, xenon engines could be allowed to exceed the balance target slightly, but only via means of increased Isp or something.

And vaporized lithium, how would that be stored in tanks? Is that also a gas/aerosol? Depending on how it's stored we can make a rough guesstimate for a suitable mass ratio. Unfortunately I know nothing about lithium in electric engines. What I do know is that lithium has a beautiful, rich crimson glow in a flame (670nm wavelength). Not sure if highly charged lithium from an electric engine emits the same spectrum, but how do you feel about tweaking the current white-purplish color of the MPDT exhaust to something like this? Having a spacecraft in the dark illuminated by that engine glow - like so, but red - would be pretty badass. Though I understand if that eats too much time.

If the VASIMR loses its hydrogen mode and becomes single-fuel argon, I'm going to un-nerf it a little bit because it is less versatile than before. I'll ponder suitable numbers and pass em to you once you've finalized everything (and maybe provided a test build, if lithium does make a grand entrance).

If no lithium, I suppose you'll have to dig up that half-finished patch draft you mentioned and we can finish it together.

Well, we should account for costs then at this stage if we can. Argon tankage (with the bugs fixed) is currently slightly cheaper than xenon (realistically it should probably be slightly more expensive but who knows) but the fuel costs are very much lower (also realistic). This is about where I want it in terms of feel (argon is cheaper than xenon, but you get less Isp and density).

And yeah if I swapped to Li, the reddish-pink exhaust would have to happen. If I did switch also, I have half a mind to have the VASIMRs swappable to Xe... mostly just for pretty blue plume effects. MPDTs using Li generally use a solid storage of lithium, gently heated to liquid form for transfer into the pre-reaction chamber, then aersolized using a heating element. So stored in solid form. 

 

Edited December 7, 2015 by Nertea

[Streetwind]

That would definitely suggest a better mass ratio than gas storage... I'll ponder some numbers for tanks and engines.

But come on, the VASIMR is the poster child engine for argon! Or do you mean multi-mode argon/xenon? In that case xenon could almost work as a drop-in replacement for hydrogen, since that mode had the very high Isp.

[Nertea]

I did mean multi-mode drop-in, actually :). 

[riocrokite]

On 12/6/2015, 8:53:56, billkerbinsky said:

-

Got a link for the paper?   (There is a plan to include a widget to produce O2 from the Martian atmosphere on the next NASA rover in 2020 as an ISRU test; IIRC the generated oxygen wouldn't actually be used for anything.  Other ISRU proposals involve hauling H2 to Mars and combining it with atmospheric CO2 via the sabatier reaction to produce methane, but modelling that starts to creep into RealFuels-level detail..

Sure, there are currently two ideas put forth by nasa:

1) making oxygen from regolith on the moon (so the most similar stuff to stock ore ISRUs) by molten oxide (regolith) electrolysis - http://isru.msfc.nasa.gov/moe.html

IMHO this is by far the most advanced (in regard to studies and experiments) concept with joint research led by mit/nasa jsc and ksc

2) making oxygen from martian co2 - MOXIE 2020 http://mars.nasa.gov/mars2020/mission/science/for-scientists/instruments/moxie/

Other ideas like methane from hydrogen or fuel from water on Mars have been with us long time however from what I read they never got out of theoretical stage. So currently imho they would more qualify to 'near future' stuff than making lox from ore.

 

[Nertea]

I'm going to put out a test release this evening with the following changes, along with 1.05-related fixes:

• Xe tanks normalized to a dry mass ratio of 1.28 (same as large stock tank)
• Ar tanks normalized to dry mass ratio of 1.25 (slight penalty over xenon to make up for Ar's huge cost advantage)
• Ar tank dry cost ranges from 0.0025/unit (2.5m) to 0.005/unit (0.625m)
• Xe tank dry cost ranges from 0.2/unit (2.5m) to 0.25/unit (1.25m) 

Do note with those numbers that a unit of Xe is considerably "larger" than one of Ar so they look weird in the cost department when compared.

I will also put out a quick test for the Li MPDT idea for evaluation. Therefore there will be no LH2 tanks or NTR patch in this test. I'm not committing this permanently, it was pretty easy to do, I'd just like to see how it works out.

• Li tanks have dry mass ratio of 1.5
• Li tankage is very expensive (2.25/unit) but the fuel is relatively cheap
• In the interest of trying more diverse parameters for fuels, Li tankage has low maxTemps and is fragile

If you all see this before I get the tweaks up, please let me know if there's anything else to change...

Edited December 8, 2015 by Nertea

[Streetwind]

Nice, I'll poke around with it tomorrow then. For reference, can you quickly toss me lithium's density and cost per unit? And the cost per tankage for the other fuels? Just so I have all the numbers in front of me.

[Nertea]

Which other fuels? LF and stuff?

Here is my propellant table.

Propellant Name	KSP Density (t/u)	Cost Ratio ($/u)
Ore	0.01
LiquidFuel	0.005	0.8
Oxidizer	0.005	0.18
Monopropellant		1.2
XenonGas	0.0001	4
ArgonGas	0.000001784	0.0105
LiquidHydrogen	0.00007085	0.03675
Teflon	?	?
EnrichedUranium	0.01097	865
DepletedUranium	0.01097	0
Lithium	0.000534	0.27
Tritium	0.000133	188
Deuterium	0.000086	0.256
StoredCharge	0	0
ElectricCharge	0	0

[Psycho_zs]

It would be strange to drop hydrogen. It has its problems, but usually whey you hear "NTR", you think "hydrogen!".

And I have a very warm memories of a swift argon-fueled VASIMR-driven research vessel strapped to a monstrous interplanetary hydrogen 'backpack'. It zipped to Jool in almost a straight line, spending less than a third of fuel. It was a pain escaping Kerbin though. But Persistent Thrust mod may fix that.

[Streetwind]

28 minutes ago, Nertea said:

Which other fuels? LF and stuff?

Nah, argon and xenon. You mentioned how much tankage costs (not fuel costs) for lithium, I thought it would be interesting how the other two were budgeted.

[Streetwind]

10 minutes ago, Psycho_zs said:

It would be strange to drop hydrogen. It has its problems, but usually whey you hear "NTR", you think "hydrogen!".

And I have a very warm memories of a swift argon-fueled VASIMR-driven research vessel strapped to a monstrous interplanetary hydrogen 'backpack'. It zipped to Jool in almost a straight line, spending less than a third of fuel.

As Nertea said, the hydrogen patch will return in some form, just not as part of the electric engines package. And you'll still be able to do the same thing with the VASIMR, just with a different kind of fuel.

The amount of problems that just vanishes into thin air by removing hydrogen is worth it the pain of having to contend with differently colored tanks on your vessel, IMHO.