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[1.2 - 1.4] Real Scale Boosters, 0.16 (2018-03-12)


NecroBones
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1 hour ago, NathanKell said:

The sea level Isp of a modern RL10 is...basically non-existent due to extreme flow separation. A nominal 10 or so would be fine IMO.

Please point me to a web page or book where I can learn more about this? I googled "rocket flow separation" and got back a metric ton of links to sites and PDFs that all promise a very technical look at one aspect of the problem, especially for those educated about such matters already -- which I am not.

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Alrighty, here's 0.4. I'm expecting this to be the last update this week, unless something really pressing turns up today.

 

0.4 (2016-02-02) - Alpha Development.
 - Enough changes since 0.3 to call it 0.4.
 - Atlas V CFLR adjustments:
    - Re-added thruster capability to Altas V CFLR, default 0 propellant.
    - Corrected direction of standard ejection charge on Atlas V CFLR.
 - Re-tuned PLF (payload fairing) ejection:
    - Re-tuned ISP (and thus total impulse) of the ejection thrust.
    - Defaulted propellant to 50% (so user can tweak up or down).
    - Added standard ejection charge, proportional to mass.
 - Radial Decoupler adjustments:
    - Increased standard ejection force, considerably.
    - Defaulted thrust propellant to 50% (so user can tweak up or down).
 - Updated sample Atlas V and Delta IV rockets with the above.
 - Added struts to sample Atlas V 500 series rockets, connecting CFLR to PLF, to stabilize PLF & Centaur.
 - Added DIRECT v3 Jupiter engine enclosure. Still incomplete vehicle, but somewhat usable now.

 

Edited by NecroBones
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OK, total brain-dead mistake... quick hotfix. lol....

 

0.4.1 (2016-02-02) - Alpha Development. 
 - Enabled fuel crossfeed in the DIRECT v3 Jupiter engine enclosure. Derp.

 

KSP%202016-02-02%2018-22-11-74.jpg

KSP%202016-02-02%2018-25-10-34.jpg

12 minutes ago, JedTech said:

@NecroBones, I can't stop drooling over this mod. Any plans to downsize it for stock Kebin?

Possibly, but I'm not sure how that would work yet. It would have to be an optional config, but I'm not sure if it would be a straight percentage rescaling of the part sizes or not (in addition to stockifying the stats). It's something to think about for down the road.

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2 hours ago, NathanKell said:

@Felbourn then it probably doesn't and I'm imagining things. :]

I'm just going to read the whole damn website again since I have learned SO much since the last time I did that. :P 

47 minutes ago, JedTech said:

@NecroBones, I can't stop drooling over this mod. Any plans to downsize it for stock Kebin?

I might consider helping with this. I love working with balance data, and doing something like "make this mod work in Stock with the same balance characteristics as the default" is something that is very appealing to my puzzle-solving-game-designing-engineering brain.

In fact, I may just try it out with ONLY the Atlas V 401 as a test and see how hard it would be.

Edited by Felbourn
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1 hour ago, Felbourn said:

I might consider helping with this. I love working with balance data, and doing something like "make this mod work in Stock with the same balance characteristics as the default" is something that is very appealing to my puzzle-solving-game-designing-engineering brain.

In fact, I may just try it out with ONLY the Atlas V 401 as a test and see how hard it would be.

 

Cool, let me know how that goes.

 

Usually when I'm setting stats for fuel tanks, I compare the cylindrical volume to existing stock tanks (or stock-alike tanks I've already made) and just scale up from there. Engines are a little trickier. I tend to aim for a "diminishing returns" sort of sliding scale. So each diameter tier up, I don't scale the thrust with the cube of the diameter, but rather something above the square. I don't have a fixed exponent, but I suspect a lot of them fell somewhere in the 2.25 or 2.5 range. TWR versus ISP is something I just tend to make up as I go along. Heh. ;)

 

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1. Yep, I do the same thing you described re: KSP game balance. In this case a rough approximation probably comes from just pretending the RD-180 is similar to something you can set up with 2.5m parts, like a Mainsail or two Vectors on a bi-coupler, or something slightly in the middle. It just depends on what the final stats are that we need for a KTO, which is what I was going to use as the baseline (a satellite of almost 1 ton with dV achieve KTO, because a real 401 can put a bit more than that -- scaled up to RSS size -- at GTO). We'll see how it goes. I am going to test this out right now after I reply.

2. Wouldn't the dry mass of the centaur tank need to be 250 kg lower since the adapter you have is 250 kg? You have this comment:

    mass = 2.076            // 2243kg - 167 (RL-10A-4-2 engine). Lowest mass values could find.
I'm pretty sure adapter needs to count against the centaur dry too.

3. You have 80 kg of RCS propellant loaded, but a real one has 154 kg. "Reaction Control System - A hydrazine reaction control system (RCS) performs vehicle control, thermal roll maneuvers and propellant settling. The RCS uses two bladder tanks with a total of 340 lb and a pressure regulated feed system supplying twelve, 6 lbf thrusters in two 2-thruster modules and two 4- thruster modules." --ULA Centaur Manual

4. If you have the urge to go REALLY crazy... the centaur has a normal mode and an Extended Missions Kit mode (for GTO-type missions). One difference is an added helium bottle (four instead of three) but let's ignore that since KSP doesn't simulate it well. What we could do (but it raises the part count :() is add a battery that is designed to attach to the center forward adapter like a real centaur, right under the payload decoupler on top of the tank. "For missions that require three burns and 5+ hour transfer orbit coasts, an Extended Mission Kit is also added. This kit includes an additional helium bottle, radiation shielding, a liquid hydrogen (LH2) tank anti-slosh baffle, and larger batteries." --ULA Centaur Manual  We could put enough charge in the battery for launch, and users would attach a couple extra of them for KTO missions with enough charge for the KTO coast. However, KSP does not simulate this well either (the fact that real batteries are drained independent of the payload) so I can understanding saying this is a crazy idea.

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Those are 40N thrusters.

"Reaction Control System - A hydrazine reaction control system (RCS) performs vehicle control, thermal roll maneuvers and propellant settling. The RCS uses two bladder tanks with a total of 340 lb and a pressure regulated feed system supplying twelve, 6 lbf thrusters in two 2-thruster modules and two 4- thruster modules. A redundant pyrovalve isolates the thruster loop from the bottles. Redundant pyrovalves also isolate the pressure side of the bottles from the helium system pressure. This system was first introduced when the boost pumps were eliminated in 1984. The pumps were run with a hydrogen peroxide monopropellant system that also provided the RCS. Two bottles with 242 lb capability were used. There were several problems in flight with this old system on Atlas Centaur. The new hydrazine system has been trouble-free on both Atlas and Titan Centaurs."

6 lbf = 26.7 newtons axial and 9 lbf = 40 N lateral

2x axial so technically 53 N per pair and 107 N total for ullage. Lateral would be 80 N per cardinal direction. Split the difference and a ModuleRCSFX would want force=0.093 or maybe just 0.1 for simplicity.

But as a game I sometimes feel RCS needs to ditch reality and go with 10x or force=1 (which actually is what he already did).

Edited by Felbourn
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2 hours ago, NathanKell said:

but even that can't compare to 40N/thruster for its RCS system!

It seems too low but it was very surprising when i got to fly one for an Atlas test. It achieves a very smooth and precise control.

And that was before Felbourn's thrust power breakdown were all thrusters were set to 40 N.

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I did some experiments with how an Atlas V would perform when scaled to Stock sizes.

First, the process: I tried a couple sizes, like making the CCB 2.5m and the Centaur proportional to it. I tried instead making the Centaur 1.25 and the CCB proportional to that. I tried a size in between. In the end it seemed the 2.5m CCB was the best approach. That also meant going 66% of full size which is a common real-to-Stock conversion factor. After that I retooled the engines to approximate specific Stock engines, therefore having the same Stock balance. I also tested all the tanks to make sure their fuel loads were appropriate for Stock tanks of the same size. And finally, I then used Stock-only parts to completely replicate the dimensions of the Atlas V, and of course used Stock engines on it. (Although the 1.25m Stock tank I used for the Centaur needed to be tweakscaled up to 1.875m to be proper.) I compared the two vehicles and messed around with the Atlas some more.

I've sort of done this kind of work before when seeing how a real world rocket might perform in almost-pure Stock and this time was no different. The truth is inescapable. In the end there is just no easy comparison of Stock to real. The problem is in the payloads. This leads to...

Second, the results: An Atlas V 401 can lift 4750 kg to GTO. If we scale an Atlas to 66% then the payload capacity should be 1365 kg. In reality, a totally Stock replica of the same relative dimensions can lift almost 5000 kg to KSO. Using this mod in Stock sizes can therefore lift almost 5000 kg, and of course WAY more to LKO. At the same time, I built a very reasonable 1.25m satellite to lift as an example. It masses in at about 980 kg. The payload capacity of a Stock Atlas is FAR beyond reality, and far beyond what can easily fit into its hard-style fairings. Maybe if we stuck to 501 and larger fairings, then we'd have better results. Maybe it we unrealistically shortened the CCB then we'd have better results. In fact, that's how I normally deal with this problem: I just shorted the stages.

Summary: Flat out resizing the Atlas V to Stock dimensions is not going to give you the same look and feel and payload capabilities of Atlas in real life or RSS.

Edited by Felbourn
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(FYI, I have extremely limited internet access through Sunday)

 

Yep, I did find some info and pictures on the Centaur RCS system, but nothing that showed exactly where they were placed. I get to a point in these projects where I'm happy if some of the larger details are mostly right, and then don't care about the small details at all. That's partly why right up front I aimed to make these "kerbalized" and SpaceY-like, so I have some breathing room to take some liberties.

 

For the RCS strength I've been setting everything to somewhere between 0.5 kN and 1.5 kN, within the same ballpark as the stock RCS thruster block, for a few reasons, one of which is that people won't wonder if it's broken. :) I did a flight test with realistic RCS thrust, where the SAS wobble was enough that after the Centaur engine cutoff, the resulting end-over-end rotation took me two ful revolutions of the Centaur before I could arrest the pitching rotation. And that was without a payload. So for gameplay reasons, I think it's reasonable to default it to something we're more used to, and as part of the RF/RO patching we can probably have it switch to more realistic numbers for those who want it.

 

18 hours ago, Joco223 said:

@NecroBones Can i use your mod to make custom rockets or can you only use them for the pre-built ones?

Yep, you can customize. Some of the parts are kinda specific, like how some interstages are specific to those tanks, and are really needed since the attachment points for them are inside the tank butts. But I've also included some adapters, and you can use different engines, and attach whatever radially you want, and so forth. Nothing is 100% set in stone.

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5 minutes ago, VenomousRequiem said:

@NecroBones, you need to see this immediately!

Oh... my heart... it's so... pretty... It's so big I had to pull it out of the VAB to show everything, and I still had to take multiple shots.

With a little bit of Procedural Parts you can accomplish anything! :3

 

Dang that's gorgeous! :)

 

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I did another Stock-version test tonight and I think I can get a decent lifter by going 50% on X & Z, and 25% on Y for propellant tanks. After that I just use straight Stock balance for all volumes, engine values, and so on. It's still overpowered but not by AS much.

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21 hours ago, NecroBones said:

Yep, I did find some info and pictures on the Centaur RCS system, but nothing that showed exactly where they were placed. I get to a point in these projects where I'm happy if some of the larger details are mostly right, and then don't care about the small details at all. That's partly why right up front I aimed to make these "kerbalized" and SpaceY-like, so I have some breathing room to take some liberties.

Just wanted to add to this to clarify: I didn't intend for it to sound like I don't care about details. But I do have a quick workflow and sometimes get to a point of "OK, not enough info here, I'm making something up"... and I'm OK with that. ;)

 

18 hours ago, Felbourn said:

I did another Stock-version test tonight and I think I can get a decent lifter by going 50% on X & Z, and 25% on Y for propellant tanks. After that I just use straight Stock balance for all volumes, engine values, and so on. It's still overpowered but not by AS much.

Huh, OK. So that puts the Atlas V in the ballpark of being a 1.875m booster, and the Delta IV into the 2,5m range (roughly, for both). How is it looking with the squished Y axis? I'd be tempted to leave it longer, even if it reduces the use cases. But some of these really are long and narrow, unlike most KSP parts.

 

16 hours ago, Felbourn said:

Like this, however what you already did seems fine to me.

ao59Vbv.png

Awesome. Yeah, that photo on the left was one I never found. Most of the ones I looked at didn't have a clear indication on it. I find it interesting that they have the forward thrust applying only at two corners but those corners are doubled up. Bah. I like my solution better. Just one more thing that makes the Atlas V look like it was assembled by a committee that never talked with.each other. :)

 

6 hours ago, KerbonautInTraining said:

"NO STEP"

On what planet would somebody go "hmm yes I'm just going to step on this multi million dollar rocket stage I'm sure it's fine."

I think the Kerbals have influenced our space program.

You know, I just love that. I feel like I need to add some "NO STEP" signs on the bottom of things, and inside the engine bells, etc. LOL.

 

 

5 hours ago, VenomousRequiem said:

I've made a decision! I volunteer to make the RP configs, because I really love this mod and want to contribute.

Give me until I get home, and I'll have them done in just a couple minutes.

Awesome!

 

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