[1.1.3] Procedural Parts - Parts the way you want 'em - v1.2.5 July 3

[StoryMusgrave]

Big thing to realize...PP under stock conditions matches stock. So PP doesn't have 'serious problems'. Stock does. But that's widely known and accepted.

Pretty sure RO changes it, RF too possibly... @Phineas Freak confirmed.

Just cherry picking a few things here...A PP tank is going to hold 3x the mass of propellant that the ET does. So while cherry picking perhaps one of the lightest tanks ever, besides what maybe old Atlas that required pressurization. Look at it another way. Your PP tank, Empty mass of ~260t while holding over 2100t of fuel...Look at the real Delta IV first stage, granted it's got engine and more than just 'tank', with empty mass around 100kg less than the SLWT while holding only 202t of propellant. That's close to 25% of what the ET does. Remember that tank has to support itself, it's contents and everything above it. So extending that thought out...comparing a PP tank to Delta. Your PP tank of 260t is around 10x that of the delta tank, while holding around 10x that of propellant that the Delta does...numbers are somewhat inline I think.

 

2 minutes ago, SirusKing said:

 That does seem like a much better number.

Imagine that, RO actually overhauling something to be more realistic.

[Phineas Freak]

9 minutes ago, SirusKing said:

If you double the radius, does the mass also double or does it quadrouple?

By increasing the diameter from 8.4m to 16.8m i got a dry mass of 121298 Kg. So, the end mass is closer to the quadruple of the initial dry mass (exact multiplier: 3.69).

@Sol Invictus to remove the version warning the only thing that you need to do is to recompile the PP source with the new revision number. The rest are only needed for updating the distribution metadata.

Edited December 20, 2016 by Phineas Freak

[Sol Invictus]

1 minute ago, Phineas Freak said:

@Sol Invictus to remove the version warning the only thing that you need to do is to recompile the PP source with the new revision number. The rest are only needed for updating the distribution metadata.

I'm sure that's true, but nevertheless it would be nice to get rid of KSP-AVC warnings as well. Anyhow, if anyone was up to the task of recompiling it, here's the patched source again.

[SirusKing]

16 minutes ago, Phineas Freak said:

By increasing the diameter from 8.4m to 16.8m i got a dry mass of 121298 Kg. So, the end mass is closer to the quadruple of the initial dry mass (exact multiplier: 3.69).

Does this keep happening or does the multiplier change? If not, it still suggests a considerable problem with the way its calculated. Making a tank wider, even with supports being included, would always increase the weight to volume efficiency. This problem exists in stock at least. 

 

on an unrelated note, I am assuming you are using a non 1.2 version of RO, so I am unable to test myself.

Edited December 20, 2016 by SirusKing

[Phineas Freak]

21 minutes ago, SirusKing said:

Does this keep happening or does the multiplier change?

Yes it does. But you have to remember the shape of the tank: if you want the math to make any sense then you have to use cylinders.

Doing a quick test with a tank like that (1 m in length) you get:

• 1 m diameter: 675 L / 12.57 Kg
• 2 m diameter: 2700 L / 50.27 Kg
• 4m diameter: 10800 L / 201.1 Kg

The mass and colume values now are exactly quadrupled between the different sizes (at least within the errors of the measurements).

Edited December 20, 2016 by Phineas Freak

[SirusKing]

2 minutes ago, Phineas Freak said:

Yes it does. But you have to remember the shape of the tank: if you want the math to make any sense then you have to use cylinders.

Doing a quick test with a tank like that (1 m in length) you get:

• 1 m diameter: 675 L / 12.57 Kg
• 2 m diameter: 2700 L / 50.27 Kg
• 4m diameter: 10800 L / 201.1 Kg

The mass values now are exactly quadrupled between the different sizes (at least within the errors of the measurements).

So, yeah, the problem still stands. What RO must be doing is just giving it a set multiplier that reduces the mass to more realistic levels for some tanks. Instead of basing it off volume and adding a multiplier, it should be based on surface area with a modifier for a far more accurate model, even in stock mode (just the multiplier is bigger than in RO).

With the whole "supporting its weight" problem, this only really applies to upwards cylinders, meaning that the length of the cylinder effects it much more than the width. This is because pressure=force x area, and since the area increases with radius, the actual pressure being exerted onto the hull would be significantly less than 2x which it currently is. Overall, this model based on volume just doesn't make sense.

[Phineas Freak]

The model is an approximation (as others have mentioned) but this does not mean that you don't get accurate results. When doing replicas for example i end up within 5% of the overall dry mass of a launch vehicle. And that discrepancy is not caused by procedural parts but from other, unrelated parts.

I recall making an Agena D that it ended up having the exact inert and gross masses as the real thing, along with exact volumes of the tanks.

[SirusKing]

24 minutes ago, Phineas Freak said:

The model is an approximation (as others have mentioned) but this does not mean that you don't get accurate results. When doing replicas for example i end up within 5% of the overall dry mass of a launch vehicle. And that discrepancy is not caused by procedural parts but from other, unrelated parts.

I recall making an Agena D that it ended up having the exact inert and gross masses as the real thing, along with exact volumes of the tanks.

I only noticed this when making an SSTO for real solar system which obviously needs big fuel tanks, and so hovers near the asymptote-like part of the Delta-V graph, where the initial mass of the rocket actually matters a lot. On these, most of the mass does actually come from the tanks, with crew and engines only adding a small portion of the mass of the rocket. I wondered why my designs didn't match my estimates back when I did use RO on a previous version and I realise now its because the mass of the tanks was still about 50 tonnes out. I could double the size of the tanks, but because it was so close to that pseudo-asymptote of the delta V graph, it would only give it an extra 150m/s. Halving the initial mass of the tanks however gave me an extra 2000m/s.

Edited December 20, 2016 by SirusKing

[nanokarlo]

Hello everyone want to add Lenght tweak for procedural heatshield Can anybody help ? What I have to add in cfg ?

Edited December 20, 2016 by nanokarlo

[Starwaster]

10 hours ago, SirusKing said:

Then the aproximation is horrible. 

 

Then come up with a better system, code it and do a pull request.

Edited December 21, 2016 by Starwaster

[SirusKing]

Just now, Starwaster said:

Then come up with a better system, code it and do a pull request.

I can't code for excrements, but I did suggest a pretty simple method already; Surface area multiplied by thickness, thickness is a function based on a tiny portion of volume. Hell, just basing it off surface area would still make it better than current.

[Starman4308]

1 hour ago, SirusKing said:

I can't code for excrements, but I did suggest a pretty simple method already; Surface area multiplied by thickness, thickness is a function based on a tiny portion of volume. Hell, just basing it off surface area would still make it better than current.

You could at the very least do the research, and come back with said function that has to deal with:

Pressurant tanks

Structural support

Strength against aerodynamic forces

Fuel lines for bipropellant tanks

Insulation and venting

Sensors for telemetry

Attachment points for radially mounted equipment such as SRBs

Etcetera, etcetera, etcetera.

If you come back with a mathematical model that you can show is a more realistic approximation of real fuel tanks and back it up with references to real tanks for a variety of sizes and purposes, people might be willing to even code it up for you. The current model, while a hackjob approximation, has the advantages of sheer simplicity and doing a reasonable job of approximating fuel tanks over a wide range of sizes.

[Rafael acevedo]

I have read, the discussions of today. Here are y to cents worth.

i wish, I could recompile to solve the 1.2.2 issues, and also include the three github pull request, but it exceed my capability. Hopefully otherbarry , will be able to do so soon. 

 

As as per the voulume discussion. It was very interesting. However my rule of thum when i did the cfg file for usi ls was that the pp tank capacity would match as close as possible the usi ls stock tanks for the Same size.  I have not tried to do this but I would suggest one of us compares a stock tank capacity vs a same sized pp tank.

[Maxsimal]

@SirusKing

If you want people to take you seriously, you need to start reading their replies more closely, you just seem angry and willing to jump on everything as being broken without much thought.

Edited December 21, 2016 by Maxsimal

[SirusKing]

5 hours ago, Maxsimal said:

@SirusKing

If you want people to take you seriously, you need to start reading their replies more closely, you just seem angry and willing to jump on everything as being broken without much thought.

If I came across as angry, I apologize. I've pointed out the flaws I thought it has and I stick with it, though.

 

Edited December 21, 2016 by SirusKing

[SirusKing]

5 hours ago, Maxsimal said:

@SirusKing

If you want people to take you seriously, you need to start reading their replies more closely, you just seem angry and willing to jump on everything as being broken without much thought.

If I came across as angry, I apologize. I've pointed out the flaws I thought it has and I stick with it, though.

8 hours ago, Starman4308 said:

You could at the very least do the research, and come back with said function that has to deal with:

 

Etcetera, etcetera, etcetera.

If you come back with a mathematical model that you can show is a more realistic approximation of real fuel tanks and back it up with references to real tanks for a variety of sizes and purposes, people might be willing to even code it up for you. The current model, while a hackjob approximation, has the advantages of sheer simplicity and doing a reasonable job of approximating fuel tanks over a wide range of sizes.

One of that actually is significant compared to the main hull, and regardless, you can just scale it up as a partial function of volume. I'm not saying basing it on surface area is perfect, just that its better than basing it purely off volume. Doubling the radius will not at all quadruple the weight.

 

The parts do fit fine with stock actually, so they are also likely basing it off of volume, but there are no parts bigger than the 3.75m diameter ones to compare to. 

Edited December 21, 2016 by SirusKing

[Starman4308]

1 hour ago, SirusKing said:

One of that actually is significant compared to the main hull, and regardless, you can just scale it up as a partial function of volume. I'm not saying basing it on surface area is perfect, just that its better than basing it purely off volume. Doubling the radius will not at all quadruple the weight.

Do you have any data for that, or are you just making a bald, naked assertion based on an oversimplified, purely geometric model of what consitutes a fuel tank?

If you're going to claim that a model is more realistic, well, maybe you should check to see that it is, as point of fact, actually more realistic.

[SirusKing]

1 hour ago, Starman4308 said:

Do you have any data for that, or are you just making a bald, naked assertion based on an oversimplified, purely geometric model of what consitutes a fuel tank?

If you're going to claim that a model is more realistic, well, maybe you should check to see that it is, as point of fact, actually more realistic.

I'm actually really damn stupid, wow. Disregard everything I have said. Looking into stress applied to the structure, these rockets actually cut it really close to the plastic deformity region, which I didn't expect at all. I did calculations and from what I can see using cylindrical stress, if the saturn V for example had hull walls 0.3mm thinner it would buckle under its own weight; wow. Since the rockets do actually need to increase wall thickness roughly linearly with weight then, the mass would qaudrouple if you doubled the radius. Welp, my bad. 

TBF, almost none of the mass is in extra stuff like valves and control points, its all in the engines and the fuel tanks.

Edited December 21, 2016 by SirusKing

[nanokarlo]

Hello everyone want to add Lenght tweak for procedural heatshield Can anybody help ? What I have to add in cfg ?

[dlrk]

What's the 1.2 status?

[Rafael acevedo]

20 minutes ago, dlrk said:

What's the 1.2 status?

The current version works on 1.2.2, it still gives and error message but it works , we need to give some time to the mod maintainer to implement the pull request in github and recompile

[dlrk]

Ah, so it's just DR I'm waiting on then

[linuxgurugamer]

Something I'd like to see is along these lines:

• Ablative material can be added to any surface,  and adds weight, the thicker the material, the more it weighs
• As it gets used, it slowly turns darker, and loses weight lighter
• Cannot be repaired, although a mechanism where a base could refurbish the vehicle would be nice

In my opinion, the whole idea behind ablative materials is that they burn up and away, thereby taking the heat away as they vaporize.  

Some of the issues I see are:

• How to add ablative material to one side of a part only
• How to change the surface texture of a part to show the ablative material

I would suspect that it would probably be easier to have a special procedural part which would be an ablator, and could be customized to the surface it is on.

Is this doable at all?

[Starwaster]

@linuxgurugamer

yes it's doable, mostly. Adding ablative to one side would require an extension to the stock ModuleAblator.  And a thermal equivalent to drag cubes to be implemented. (Possibly  the 'cubes' alone might be sufficient)

[Starwaster]

On December 21, 2016 at 10:19 AM, SirusKing said:

I'm actually really damn stupid, wow. Disregard everything I have said. Looking into stress applied to the structure, these rockets actually cut it really close to the plastic deformity region, which I didn't expect at all. I did calculations and from what I can see using cylindrical stress, if the saturn V for example had hull walls 0.3mm thinner it would buckle under its own weight; wow. Since the rockets do actually need to increase wall thickness roughly linearly with weight then, the mass would qaudrouple if you doubled the radius. Welp, my bad. 

Apologies for late reply and not sure how important this really is except as a point of trivia maybe but: 

Saturn tank thickness  actually weren't uniform. It varied being thicker at the bottom. (Stress, again)

not sure how much of that was actual wall thickness vs reinforcement. 

I'd post some links to relevant documents but I'm on my phone, at the mall wrapping presents for the cat shelter