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

[Raptor9]

@Nertea I'm sure a lot of people appreciate your efforts and hard work.  Don't forget to put the keyboard and mouse down for a while for the holidays though.  Have a Merry Christmas

Edited December 21, 2015 by Raptor9

[Captain Sierra]

4 hours ago, Nertea said:

https://www.dropbox.com/s/8ap4qmcmm175z2l/NearFutureElectrical0_6_T6.zip?dl=0

Please work :(. I'm kinda at my wits end. This is a bad hack. For the first few seconds after loading a vessel the reactor is forced to generate no heat (while the stupid catchup occurs). This means there will be a big drop in temp suddenly and it will spool back up later. 

It seems to work in my limited tests and is I guess okay.... I haven't seen any overheats at least.

Seems good enough from a quick shakedown, now go enjoy the holiday and get back to us in 2016. We'll wait.

[Nertea]

Well, I did get this guy unwrapped and diffuse textured today due to happiness at NFE fix. Specular and normal to come, but it looks pretty nice at the moment. It's the ungodly love child of a Vinci, RD0120 and an RS-25. With a nuclear reactor on it. 

Edited December 21, 2015 by Nertea

[Streetwind]

9 hours ago, Nertea said:

It's the ungodly love child of a Vinci, RD0120 and an RS-25. With a nuclear reactor on it. 

That's one of the most badass descriptions of a rocket engine I've ever read

Time to try out that NFE fix...

 

EDIT: it appears to indeed be working for me, too! If I'm fast enough to rightclick the reactor I can even see it in action.

 

Edited December 21, 2015 by Streetwind

[Jimbodiah]

Want... that.... engine....

[Starbuckminsterfullerton]

20 hours ago, Nertea said:

Well, I did get this guy unwrapped and diffuse textured today due to happiness at NFE fix. 

Glad you got to go back to working on the fun stuff!  Engine looks great, matches the cryo engines very nicely, and I think the grey plumbing looks even better than the orange those use. 

[RedParadize]

Thats a awesome looking engine you have there. Hope you release it soon!

[Captain Sierra]

21 hours ago, Nertea said:

Well, I did get this guy unwrapped and diffuse textured today due to happiness at NFE fix. Specular and normal to come, but it looks pretty nice at the moment. It's the ungodly love child of a Vinci, RD0120 and an RS-25. With a nuclear reactor on it.

There are no words .... when can we have it?



But seriously, take the holiday, enjoy it, and come back afterwards. Critiquing the engine, I almost doesnt look like it belongs in a game as semi-silly as KSP, as its a different kind of strange .... That said the model is fricking gorgeous as always and continues to outdo the stock assets.

Edited December 22, 2015 by Captain Sierra
Adding images is damn uninuititive on this forum .... grrr ....

[Starbuckminsterfullerton]

20 hours ago, Captain Sierra said:

[It] almost doesn't look like it belongs in a game as semi-silly as KSP, as its a different kind of strange .... That said the model is fricking gorgeous as always and continues to outdo the stock assets.

With the rise of Porkjet, this can be said for a lot of the stock parts as well. I hope we keep moving in that direction.

[Nertea]

Ok, testing seems to show good results. I'm now down to the description fixing and number tweaking stage, so I can hopefully declare this NFE dev round complete. As usual, I'd really like to thank everyone who helped out. They made this possible. Apply some rep!

I'd like to turn the conversation back to LH2, CryoEngines and AOYUNEM (As Of Yet Unnamed Nuclear Engines Mod), now that LH2 has been cut out of electrical engine balance this might be a little more manageable.

CryoEngines "feels" nice to me right now, but there's always room for changes.

The way it looks to me is that the mass ratio of LH2 tanks just needs to be friendlier. This will likely need some small downward revisions in CryoEngines Isp values, I'm fine with that. I'd like to aim for something slightly lower than LiquidFuel dry mass. The only annoying thing that I see is that the dry masses (and total masses) of some of the smaller LH2 tanks will be ridiculously small. It might be good to fudge the amount of LH2 going into a tank a bit more than it already does. 

This will still "nerf" the LH2 LV-N a little bit with a worse dry mass ratio, but I'm totally willing to buff the LH2 Isp up to a max of 900 and/or decrease the engine mass a bit. Or do nothing, really. The progression for AOYUNEM would indicate that the Nerv is really a bottom tier, entry level nuclear engine, and could be not the end-all be-all that it is in stock.

The other thing to solve is some sort of differentiating factor for the fancy LH2 'orbital' tanks without implementing boiloff, preferably. I'm thinking minor advantages and disadvantages, mostly to discourage atmospheric use and encourage orbital use. Options might include that drag increase (doable for sure), increasing the LH2 volume compared to the basic tanks (but preserving the same mass ratio)... fiddly things like that.

 

 

[Fraz86]

 

1 hour ago, Nertea said:

The way it looks to me is that the mass ratio of LH2 tanks just needs to be friendlier. This will likely need some small downward revisions in CryoEngines Isp values, I'm fine with that. I'd like to aim for something slightly lower than LiquidFuel dry mass.

Looking at this in terms of "massPerUnitLH2" (the variable in the fuel switching config), the current values of 0.000035 (for stock tanks) and 0.000025 (for cryo tanks) give dry mass ratios of 2.02 and 2.83, respectively. A value of 0.00001 would give a ratio of 7.09, just below LiquidFuel's ratio of 8 (the difference would be trivial in gameplay). If you want a slightly more meaningful difference, a massPerUnitLH2 of 0.000015 would give a ratio of 4.72.

Quote

The only annoying thing that I see is that the dry masses (and total masses) of some of the smaller LH2 tanks will be ridiculously small. It might be good to fudge the amount of LH2 going into a tank a bit more than it already does.

The current "LH2FudgeFactor" is 1.5, meaning that a given volume of tank is allowed to hold 1.5x as much LH2 as it should. In LH2/OX tanks, this means that LH2 occupies ~55% of the tank's volume, whereas (without fudging) it ought to occupy ~65% of the tank. Increasing LH2FudgeFactor to 1.8 might be a reasonable bump, with a corresponding increase of mixOXProportion to 0.5 (meaning that, with 180% LH2 density, the volume of LH2/OX tanks would be evenly split between LH2 and OX).

Quote

The other thing to solve is some sort of differentiating factor for the fancy LH2 'orbital' tanks without implementing boiloff, preferably. I'm thinking minor advantages and disadvantages, mostly to discourage atmospheric use and encourage orbital use. Options might include that drag increase (doable for sure), increasing the LH2 volume compared to the basic tanks (but preserving the same mass ratio)... fiddly things like that.

I like the possibility of increased drag, however, I hesitate due to concern for consistency. If LH2 'orbital' tanks are given higher drag, what about other skeletal parts that also look like they should have higher drag? For example, what about Xe, Li, and Ar tanks? What about Octo-Trusses? You could give them all higher drag, but then it becomes a rather far-reaching solution, which I suppose is fine if you're comfortable with it. It's also quite tedious to implement because it requires defining custom drag cubes for each part, unless you've found an easier way to do it. On the other hand, I worry that options other than increased drag will fail to provide the 'orbital vs atmospheric' differentiation that you're hoping for, so I don't know what to suggest as an alternative.

[Nertea]

Thanks for the notes. The consistency is indeed a problem - the drag cubes not so much as they really only need to be overridden once, so one chunk of annoying work then it's over. I don't really like the idea of sticking a bunch of new fuel tanks with no advantages or disadvantages in for no reason though, which is a bit of a pain. 

I guess having boiloff would be the best differentiator to be honest. If there's a nice, player-friendly, transparent way of doing this, I'm all ears. 

[Kerbas_ad_astra]

To help differentiate lightweight "orbital" tanks from heavier "stack" fuel tanks, you could make them bulge out from their stack connections (see e.g. RoverDude's Kontainers).  So, their cap ends would be 2.5m (or whatever size), but the spherical tank itself would be wider.

I realize that this might raise the question of "why not just make the sphere 2.5m wide" (to which I guess the answer might be "that would require a heavier structure"), but they certainly wouldn't look like they're meant to be used in a rocket.

[Fraz86]

Another thought regarding buffing LH2 density:

The "mixOXProportion" of stock LF/OX tanks is 0.55 (i.e., 0.55L OX per liter of tank volume). If we're increasing the mixOXProportion for LH2/OX tanks (due to increasing LH2FudgeFactor), perhaps we might as well go to the point of matching the stock LF/OX proportion at 0.55. The corresponding LH2FudgeFactor would be 2.22. This would provide a nice symmetry when switching between LF/OX and LH2/OX configurations, in that OX would remain the same. I can't think of any reason why this is particularly important in terms of actual gameplay, but it might slightly improve players' ability to compare the different fuel configurations.

 

Here are a few thoughts regarding relatively simple implementation of boiloff:

'Atmospheric' tanks - Boiloff occurs at a fixed rate (e.g., 0.1% of the tank's total volume per minute) and nothing can be done to mitigate it. The rate is low enough that the impact on lifting stages is trivial. The part descriptions of these tanks would need to be addended to make it very clear that they are not intended for prolonged use.

'Orbital' tanks - Here we have a few options, in increasing order of complexity:

• No boiloff, but the tank otherwise has significant disadvantages (e.g., higher cost, inferior dry mass ratio, lower maxTemp, etc.).
• Constant EC requirement. As long as EC is available, no boiloff occurs. If the craft runs out of EC, boiloff occurs at the same rate as for atmospheric tanks.
• Requirement to maintain a low core temperature using radiators. As long as the core temp of the tank remains below the threshold, no boiloff occurs. If the core temp of the tank rises above the threshold, boiloff occurs at the same rate as for atmospheric tanks.

Edited December 23, 2015 by Fraz86

[billkerbinsky]

48 minutes ago, Fraz86 said:

Another thought regarding buffing LH2 density:

The "mixOXProportion" of stock LF/OX tanks is 0.55 (i.e., 0.55L OX per liter of tank volume). If we're increasing the mixOXProportion for LH2/OX tanks (due to increasing LH2FudgeFactor), perhaps we might as well go to the point of matching the stock LF/OX proportion at 0.55. The corresponding LH2FudgeFactor would be 2.22. This would provide a nice symmetry when switching between LF/OX and LH2/OX configurations, in that OX would remain the same. I can't think of any reason why this is particularly important in terms of actual gameplay, but it might slightly improve players' ability to compare the different fuel configurations.

The space shuttle used a ratio of 2.7l of H2 per liter of lox; that would be a volumetric ratio of 0.27 liters of OX and 0.73 liters of H2 per liter of tank volume.   (On the mass side, because of hydrogen's fluffiness, that inverts to 6kg of oxidizer per kg of hydrogen.  8:1 is the stoichiometric mass ratio, but it looks like the SSME runs fuel-rich).    Hydrolox rockets should have a definite volume penalty - you just need much bigger tanks to contain the needed mass of propellant.

 

 

[Captain Sierra]

6 hours ago, Nertea said:

CryoEngines "feels" nice to me right now

I echo this sentiment. The size of the rockets and the payloads they can orbit feels right.

6 hours ago, Nertea said:

Options might include that drag increase (doable for sure), increasing the LH2 volume compared to the basic tanks

I definitely support this. I'd opt for higher drag, lower dry mass (I'm going to argue for a better mass ratio on "orbital" LH2 tanks, with the concession of them not getting fuel switching), so that they're easier to put in space when inside a fairing.

 

1 hour ago, Fraz86 said:

Here are a few thoughts regarding relatively simple implementation of boiloff:

-snip-

I'd very much like to look into boiloff options myself, but this would likely require further plugin coding that, depending on implementation, is highly intertwined with the ever-changing stock heat system. Nertea probably doesnt want to have to do through the NFE hassle twice every update. While a fun thought experiment, its probably best to keep it that way no matter how cool it may be.

[Fraz86]

9 hours ago, billkerbinsky said:

The space shuttle used a ratio of 2.7l of H2 per liter of lox; that would be a volumetric ratio of 0.27 liters of OX and 0.73 liters of H2 per liter of tank volume.   (On the mass side, because of hydrogen's fluffiness, that inverts to 6kg of oxidizer per kg of hydrogen.  8:1 is the stoichiometric mass ratio, but it looks like the SSME runs fuel-rich).    Hydrolox rockets should have a definite volume penalty - you just need much bigger tanks to contain the needed mass of propellant.

The mass ratio of LH2/OX tanks corresponds to the fuel usage of cryo engines, which burn 10 units LH2 per unit OX. This gives a mass ratio of 7.06kg OX per kg LH2, which is pretty close to your space shuttle example.

In terms of volumetric ratio, however, Nertea and testers concluded that using real-world density for LH2 results in tank volumes that are simply impractical and un-fun. Therefore, the density of LH2 in fuel tanks is "fudged" (currently at 150%) for gameplay reasons.

In Nertea's previous post, he proposed that perhaps this density-fudging should be increased, which of course would result in a decrease in the LH2:OX volumetric ratio. I was merely suggesting that - if we are further decreasing the LH2:OX volumetric ratio - perhaps we should just match it to the LF:OX volumetric ratio. This change would be from 0.55L:0.45L to 0.45L:0.55L, which isn't too dramatic.

Also, as further reassurance, even with LH2 density fudged to 222%, LF would still be 5.78x more dense than LH2, so you would still notice a difference in the tank volume required for hydrolox rockets.

Quote

I'd very much like to look into boiloff options myself, but this would likely require further plugin coding that, depending on implementation, is highly intertwined with the ever-changing stock heat system. Nertea probably doesnt want to have to do through the NFE hassle twice every update. While a fun thought experiment, its probably best to keep it that way no matter how cool it may be.

I understand that incorporating heat mechanics might be asking too much in terms of plugin coding and complexity for players. That's why my suggestion for boiloff in atmospheric tanks does not involve any heat mechanics, nor do the first 2 out of 3 of my options for orbital tanks.

Boiloff could be very simple, e.g.: atmospheric tanks continuously lose fuel at a slow rate (e.g., 0.1% LH2 capacity per minute), while orbital tanks never lose fuel but are otherwise inferior (e.g., higher cost, inferior dry mass ratio, lower maxTemp).

Edited December 24, 2015 by Fraz86

[Kobymaru]

Could somebody repost the most recent Dev-build of NFE? It seems that the Dropbox link is down.

[Nertea]

I might cook up a simple implementation of boiloff to see how it works. It would actually require little to no plugin work. 

11 minutes ago, Kobymaru said:

Could somebody repost the most recent Dev-build of NFE? It seems that the Dropbox link is down.

Absolutely not, I'm cleaning out my dropbox because I am making room for official release versions.

[Psycho_zs]

Boiloff may seem like conceptually complex, but it could very logically solve lifter/vacuum tanks balance. Orbital tanks could require some modest radiator power and additional Ec, and lifter tanks would just lack the ability to use radiators.

Edited December 24, 2015 by Psycho_zs

[Captain Sierra]

7 hours ago, Nertea said:

I might cook up a simple implementation of boiloff to see how it works.

Well since thats on the table .... here's my $0.02 on the subject:

 

Possible implementation A (simple version):

Boiloff is per-tank, encouraging fewer larger tanks over many small.
Boiloff is a tank-configurable static rate, unaffected by temperature, radiators, or anything.
Lifter (stock) tanks have boiloff, orbital (NFP) tanks do not.
Lifter tanks have poorer mass ratio (heavier metal for rocket integrity), while orbital tanks have better mass ratio but worse volume ratio (space for insulation, lighter materials; also helps validate the massiveness of some of the LH2 tanks)

Possible implementation B (complex/thermal version):

Boiloff is per-tank, as above.
Boiloff is a dynamic rate as a function of tank interior temperature (lifter tanks have poor (high) skin-int conduction multipliers, while orbital tanks have lower mults).
Lifter tanks lack any form of refrigeration, boiloff is unpreventable.
Orbital tanks require minimal Ec to refrigerate themselves, reducing interior temperature but increasing core temperature (radiators can pull the core heat away).
As above, lifter tanks have worse mass ratio but better volume ratio (heavier structure but no space lost to insulation/refrigeration equipment), and orbital tanks have better mass ratio but worse volume (space lost to insulation & refrigeration systems, but lighter materials not intended to support 120 ton rockets).

 

I'd like to see how your vision of it relates to these two concepts. Is it somewhere in the middle or did I totally miss the mark?

[Nertea]

A is what we will test (I hate the heat system with a passion right now), but with one change:

12 hours ago, Captain Sierra said:

Lifter tanks have poorer mass ratio (heavier metal for rocket integrity), while orbital tanks have better mass ratio but worse volume ratio (space for insulation, lighter materials; also helps validate the massiveness of some of the LH2 tanks)

Same volume ratio, lifter tanks have better mass ratio though.

[Fraz86]

3 hours ago, Nertea said:

Same volume ratio, lifter tanks have better mass ratio though.

I think that's the right way to go. If orbital tanks had the better mass ratio, they would be too attractive for use on lifting stages, or at the very least it would present the player with a confusing tradeoff. It's much more transparent to make atmospheric tanks unambiguously better except for boiloff.

One other point of clarification: will boiloff occur "per-tank, encouraging fewer larger tanks over many small," as Captain Sierra suggested, or will it be "per LH2 capacity," in which large tanks have no particular advantage over small tanks? Personally, I would find the latter to be more straightforward.

Edited December 25, 2015 by Fraz86

[Captain Sierra]

12 hours ago, Nertea said:

A is what we will test (I hate the heat system with a passion right now), but with one change:

Same volume ratio, lifter tanks have better mass ratio though.

Fully support hating of the stock heat system.

So just to recap the pros and cons of the orbital tanks as it stands right now ...

Cons:

• Lower mass ratio
• Higher drag
• Lower impact tolerance
• Lower heat tolerance

Pros:

• No boiloff
• Eye candy

I personally think that's a lot of tradeoff for avoiding boiloff (though I understand the intended goal of it all). 

[Fraz86]

It looks like Nertea decided against higher drag for consistency reasons, and the reality is that lower maxTemp and crashTolerance don't really matter in most situations.

Moreover, avoiding boiloff is extremely valuable. In fact, it's outright necessary if you plan to use the fuel more than a few days or weeks after launch (depending on what exactly the boiloff rate turns out to be). Thus, orbital tanks could have pretty much any list of downsides and they would still have clear use cases.

Edited December 26, 2015 by Fraz86