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[0.23.5] StretchySRB: A StretchyTanks Continuation v9 Final Pre-PP edition 3/21/14


NathanKell

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Are there any stretchy tanks with independently variable top and bottom diameters (so you can, for e.g., go from 5M to 3.75m). If not do you have any plans to make some? I guerss the volume calculations might get a bit more tricky but it'd be a really handy addition.

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Are there any stretchy tanks with independently variable top and bottom diameters (so you can, for e.g., go from 5M to 3.75m). If not do you have any plans to make some? I guerss the volume calculations might get a bit more tricky but it'd be a really handy addition.

There are not any currently in the mod. Calculations for it would be extremely simple though, assuming that the change in width from top to bottom is linear. It's just

V = (pi*h/3)(R^2 + R*r + r^2)

where R is the radius of the wide end and r is the radius of the narrow end. Details: http://jwilson.coe.uga.edu/emt725/Frustum/Frustum.cone.html

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Yeah but I think it is related to the way the plugin and parts were made, I remember reading Nathan asking about that to AncientG. Not sure if he will implement it one day, would be awesome!

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Is this the right place to ask regular stretchytanks questions? I'm getting no response in the stretchytanks thread, and there's a comment that points people over to here.

Anyhow, I'm getting weird delta-v behavior when resizing tanks. I resize a tank until it's got the delta-v I want. Looks good. Then as soon as I move my mouse away from the tank, the delta-v number drops! (I see the same results in both Kerbal Engineer and MechJeb delta-v panels).

It's not completely consistent, either, meaning that if I keep re-upping the tank size so my delta-v is about 1670m/s and move the mouse away, the delta-v drops down, I stretch the tank back up to 1670m/s (making it even taller), the delta-v drops back down, but it drops back down closer to the original low number despite the tank's size, so the tank keeps grown and growing as I try to hit my target delta-v number. Any idea's what's going on here?

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You're using StretchySRB anyway (although a stretchy tank, not a stretchy SRB), so this is the correct place to ask.

You're using modular fuels. Modular fuels rounds resources to 4 sig figs. Stretchy stretches in hundredths of a percent. The more you stretch, the more rounding error there is; when done stretching you need to go to action editor and remove your bipropellant tanks and then readd them in the correct ratio.

To avoid making the rounding even worse, MFS is told not to round until after you move your mouse away from the tank; before I did that, the errors were _very_ bad. It's the price you pay for getting realtime dV changes; I could avoid all this by only updating fuel quantity after all scaling was done.

Workflow:

1. Add tank.

2. Add engine.

3. Configure for right mixture in MFS GUI.

4. Scale tank until dV approximately correct.

5. Remove the tanks in MFS GUI, re-add with the automatic button (or do it manually). Now they will be correct mixture again.

6. Double check dV is as desired.

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Got it!

There's got to be a way around that. Is there an iterative/additive process you could remove and just replace with a flat calculation of the final rounded value for volume * fuel and the delta-v conversion? You'd still get realtime updates and the value when you let go would remain constant, I think.

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That's...pretty much exactly what I did, and how it works now: you only get your final rounded value when the cursor leaves the tank. (rounding is disabled during stretching, and doubles have enough precision that you won't be getting rounding errors once stretching begins).

I'll see how much better things are without any rounding at all; I may just switch to always having rounding disabled for MFS+Stretchy.

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I'm noticing a weird glitch where a lot of the rockets I build using stretchy tanks exhibits a position error upon loading of a rocket, leaving a gap. I have to unconnect-reconnect the interstage part directly below it. (I'm connecting the interstage directly to the fuel tank to make a 2m -> 1m adapter since I don't have any actual parts that do that for those sizes. The order from top->down is the 2m silver stretchy tank -> 1m-sized procedural interstage -> 1m Optio ® engine.)

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This is due to attach nodes not updating onLoad() (but proc fairings needing them then), and is being fixed this weekend.

W00t! I hate that bug (especially since I like to make multiple launches for testing a design before finally going with it), glad to hear its getting fixed. Good work man...C:

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I'm looking at the exterior thermal fin and it says it has 'Heat Pump' at '50s' and an electrical requirement of '2F/h', so I'm guessing the labels got mixed up? Anyhow, does that mean a single fin uses 50 units of energy per second just to cool something down by 2 degrees Fahrenheit per hour?

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I belive I have an old version and may be fixed in V6, but just checking:

Every time I use strechy tanks/srb on radial copular, each time I reload (aka, say launch, revert to VAB, bam), it moves a few meters away. Visually displeasing but no structural weakness. In fact it could aid in booster sepration... hmmm, I could abuse this...

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drtedastro: Yep! Also, check your PMs for clarification if you haven't already.

Roger that..... That's is good news....

Now we have to workout and get in shape to due justice to the Xmass feasting.....

Hard work, but I am sure we are the correct ones to do it.....

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It's not possible with how stretchytanks works: by altering the transform you can only do uniform scales. However, e-dog is working on such a tank. :)

Good news. It will be a good addition to eventually be able to add to KSP if it's feasible. e-dog's done great things so I expect he can pull it off :)

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Nathan, may I ask how you modified the "stock" stretchy tank side texture when you created the Saturn V like one? I can't find it anywhere and I would like to create a new based on the original you used. If it's not complicated at least.

Edited by Reddragon
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What is up with the tapered tanks in the first post? Is that a new feature, or did I miss that completely?

QawxV1Kl.png

I tried making them myself, couldn't find out how. I think he used procedural fairings to achieve that look.

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