[1.2/1.3] Real Scale Sea Dragon 0.3.4 (2016-07-12)

[Miuramir]

2 hours ago, NecroBones said:

Guess what? I decided to work on that part first.

That's a cool model, and may be the best Kerbalized version that is practical, but I have a sinking feeling that the original isn't that straightforward.  The more I re-read up on the details, the less it seems like a modern conventional expandable nozzle. 

Aerojet-General Corporation Report No. LRP 297, Volume 1

Page II-A-5 (virtual page 39 in my PDF)

... "The expandable nozzle on the second-stage provides a method of conforming to a simple configuration envelope while still producing a large expansion ration when opened (compared to equivalent fixed nozzles)." ...

Page II-D-15 (virtual page 87 in my PDF)

... "The second-stage thrust chamber and a portion of the expansion section of the nozzle are cooled, using conventional tubular wall construction, with hydrogen from the main tank.  The hydrogen flow is non-regenerative with the heated hydrogen gas being expelled at the open ended tubes into the main gas steam at an area ratio of 6.2:1.  The remainder of the nozzle is constructed of thin stainless steel and is cooled by radiation alone.  This cooling technique is possible because of the low chamber pressure and the resulting lowered heat flux.  The thin sheet metal nozzle is folded about the first-stage tankage during first-stage operation and is expanded to a full conical shape when the second-stage engine fires.  An example of a nozzle of this type is shown in Figure II-D-6." ...

Figure II-D-6 is on virtual page 132 of the PDF, and is a bad scan of an old photo; it's difficult to tell what is going on.  Labeled "Large Expandable Nozzle Currently Undergoing Altitude Tests".  To the left is a vertical cylinder with vertical accordion-pleats or ridges, labeled "Length = 55.0 in, Dia. = 26.0 in"; to the right a smooth-seeming cone labeled "Length = 52.0 in, Max. Dia. 57.75 in".  The picture appears to be outdoors, with a person in a suit for scale. 

All this seems to imply that the expandable nozzle is not only increasing length, but area (diameter), with the significant intended effect of giving a better-expanded vacuum nozzle that is bigger than can be fitted as-is into a 75' diameter rocket body (!).  I'm trying to reverse calculate how big it should be based on the stats they do give, but it's not quite making sense yet... I'm coming up with an effective diameter of 136 feet, which seems too large even for this vehicle. 

P.S.: For those following at home, the best source of "original" info I'm aware of currently is at http://neverworld.net/truax/

[NecroBones]

 

Cool. I have that PDF as well, but hadn't seen that part. The image looks like a plain metal truncated cone, so it's hard to tell what the moving parts are. It's probably some sort of sliding system with a lot of overlap between the plates while stowed.

 

The good news is I can always rework the engine in the future too. Now that the animation will be included (and people start using this version), the saved states for everyone's games will be consistent even if I remodel the engine and animation later.

 

Image:

 

[NecroBones]

 

I discovered that I miscalculated the length of the first stage engine a little bit, so I've shortened it up.

 

Edit: @Red Iron Crown got me thinking about it, but no, he didn't create it.

 

 

 

 

[NecroBones]

 

Rough outline of the ballast tank exists now too:

 

 

 

 

[swjr-swis]

Jeb's first reaction: "We're gonna need a bigger launchpad..."

[NecroBones]

3 hours ago, NecroBones said:

I discovered that I miscalculated the length of the first stage engine a little bit, so I've shortened it up.

 

Now I see what happened. I didn't extend the skirt down far enough on the first stage tank, and measured from the wrong place. I may have to rework the tank slightly.

[NecroBones]

38 minutes ago, NecroBones said:

 

Now I see what happened. I didn't extend the skirt down far enough on the first stage tank, and measured from the wrong place. I may have to rework the tank slightly.

 

Tank skirt extended. Now it looks more like the diagrams, and the ballast tanks can be sized appropriately.

 

 

 

[NecroBones]

 

I won't be surprised if we find problems, since I got this out the door kinda quickly. But I wanted to let people start using the new edits to the existing parts, and try some sea launches.

 

0.2 (2016-03-28) - The Sea-Launch Update.
 - Increased crash tolerance considerably on all parts, to allow bouncing around in the water.
 - Added attachment node at bottom of first stage engine to allow attaching the ballast tank.
 - Extended first stage tank's lower skirt, and removed extraneous attachment node corresponding to it.
 - Shortened first stage engine length (and updated sample rocket accordingly), after discovering miscalculation.
 - Reworked colliders for first and second stage main engines, and first stage tank.
 - Added ballast tank for sea launches.
 - Added SPH sample rocket with ballast tank.
 - Updated VAB sample rocket to ignite the verniers at launch in the staging.
 - Added an animated bell extension for the second stage engine, and updated sample rockets to use it (action group 1).
 - Added custom smoke trail for first stage engine (known issue: runs regardless of air pressure).
 - Removed smoke trails from upper-stage engine + verniers (hydrogen burns cleanly).

 

Screenies:

 

 

[Miuramir]

 

6 hours ago, NecroBones said:

 It's probably some sort of sliding system with a lot of overlap between the plates while stowed.

Still trying to figure out how this is supposed to work.  What if it works somewhat like an inside-out version of the "petaled" exhaust system on a afterburning turbojet?  Instead of more or less being designed with a cylinder that can close down into a cone, it starts as a 60 degree cone around the 1st stage conical top, which expands in flight to a bigger cone. 

If you're looking for visual reference, this video of a J79 (used by the F-104 Starfighter, B-58 Hustler, F-4 Phantom II, A-5 Vigilante, and the IAI Kfir) on a test stand with the petals being exercised has some great closeups, starting around 5 minutes:

https://youtu.be/x5ccK94IvsA?t=300

[kiwi1960]

No...... no no no no no no no no no no no no no no no no....... this is just...wrong...... very very ....wrong.

 

I must have it. I simply must... it will still be wrong, but at least, I will have it....

 

[lurkoholic]

Maybe it functions similar to a turbojet nozzle, but it starts as a cylinder (or a cone with a very small angle) and expands out to a cone shape. Maybe the exhaust pressure alone could cause it to expand, as long as the ambient pressure is low enough? Although that might leave it vulnerable to drag forces affecting its shape.

The nozzle is shown as the horizontal lines that cover most of the lower stage (to the 421 ft mark) on the diagram in the OP. I assume the lower stage attaches to the upper stage fixed nozzle somehow, but i can't tell if the the interstage on the diagram is external to the nozzle or not.

@NecroBones any plans to make the inflatable bladder (?) that allowed the lower stage to land safely at a mere 100 m/s?    Thanks for all the awesome mods!

Edited April 1, 2016 by lurkoholic
Misplaced comma

[boomchacle]

that... is big.

[NecroBones]

4 hours ago, lurkoholic said:

@NecroBones any plans to make the inflatable bladder (?) that allowed the lower stage to land safely at a mere 100 m/s?    Thanks for all the awesome mods!

 

Hehe, I'm not so sure I could make that work.

 

[Miuramir]

41 minutes ago, NecroBones said:

 

Hehe, I'm not so sure I could make that work.

 

Page I-16-17 (virtual page 31-32):

"The ability of the pressure-fed stage to survive intact water impact velocities between 300 and 600 ft/sec, combined with a sea-going design that will survive immersion without requiring extensive refurbishment, makes a simple drag type recovery system most attractive. Without auxiliary drag devices, the impact velocity of the Sea Dragon first stage is supersonic. It is fairly certain that the current design will not survive such an impact without damage. It is possible that a redesign, incorporating a different nose shape, a larger nozzle area ratio, structural strengthening in key spots, and some repressurizing of the forward tank, would result in a vehicle capable of withstanding its normal impact. Because definitive feasibility could not be shown in the time available, it was decided to incorporate an inflatable drag skirt. This drag skirt reduces the impact velocity below 300 ft/sec, low enough to prevent damage to the structure as designed. The weight penalty of the drag skirt is less than 2% in payload."

300 to 600 ft/sec is impact of about 91 to 182 m/s.  So the first stage tank and engine should be rated for impacts of over 100 m/s in KSP terms, probably somewhere in the 150 range? 

Page II-C-2 (virtual page 66) points out that a fully expendable variant gets 30,000 lb. extra to orbit; that's counting both the lack of the inflatable conical flare itself, and some missing structural reinforcement designed in for the "usual" water landing. 

Page II-D-40-41 (virtual page 112-113) has some more details; they rejected parachutes or an even *larger* engine bell for the inflatable flare decelerator.  "This device is attached, in deflated package form, to the first-stage thrust chamber. When inflated, it takes the form of a large conical flare 300 ft dia with a half angle of 55 °.  The flare is made up of a large, [30] ft dia torus rigidized with a smaller inflatable tube I0 ft dia and covered with a surface generating outer skin. The torus and supporting tubes are constructed of rubberized nylon-dacron reinforced fabric and are protected from thermal environment by the outer skin. The outer skin is an ablating rubberized asbestos fabric and is sacrificial; that is, it is replaced for each flight. " ...

This didn't quite make sense, until I found the drawing; Figure III-C-3 (virtual page 229) is a fairly nice drawing of the Re-entry Flare Design.  The 30-foot torus above is a typo, and should be 300-foot torus, as is clearly dimensioned on the drawing. 

It occurs to me that with 1.1 we are supposed to get a stock inflatable heat shield, which looks rather similar to the Sea Dragon's design; while I'm not really a modeler, it seems that one could repurpose some of the stock mechanics and art to pull this off.  Another possible real-world source of art, textures, and ideas is the NASA / JPL Low-Density Supersonic Decelerator (LDSD), specifically the Supersonic Inflatable Aerodynamic Decelerator (SIAD) portion of the concept. 

[Jay Mission]

16 hours ago, NecroBones said:

It's probably some sort of sliding system with a lot of overlap between the plates while stowed.

I was wondering if you had considered that the nozzle is all one piece like in the photo with the gentleman in the suit. Maybe think of the nozzle extension less as "turkey feathers" like you would see on a jet engine, and more like "umbrella". Or, maybe even more accurately, (I'm going to loose my man card for even mentioning this) a woman's pleated skirt. The nozzle extension looks to be on the outside of the first stage tankage, represented by the dark grey texture applied to your model. The blueprint also shows what appears to be three (pyrotechnically released?) straps that hold the nozzle closed against the first stage until staging occurs. If Sea Dragon has a diameter of 75 feet, then my math comes out to be about 166 feet for the nozzle exit diameter when open. Anyway, just my 2 cents, could be wrong. Feel free to ignore if you already knew this.

Edited March 29, 2016 by Jay Mission
typo

[NecroBones]

8 hours ago, Miuramir said:

...

300 to 600 ft/sec is impact of about 91 to 182 m/s.  So the first stage tank and engine should be rated for impacts of over 100 m/s in KSP terms, probably somewhere in the 150 range? 

...

Page II-D-40-41 (virtual page 112-113) has some more details; they rejected parachutes or an even *larger* engine bell for the inflatable flare decelerator.  "This device is attached, in deflated package form, to the first-stage thrust chamber. When inflated, it takes the form of a large conical flare 300 ft dia with a half angle of 55 °.  The flare is made up of a large, [30] ft dia torus rigidized with a smaller inflatable tube I0 ft dia and covered with a surface generating outer skin. The torus and supporting tubes are constructed of rubberized nylon-dacron reinforced fabric and are protected from thermal environment by the outer skin. The outer skin is an ablating rubberized asbestos fabric and is sacrificial; that is, it is replaced for each flight. " ...

...

 

Yeah, I could definitely increase the "crash tolerance". 150 m/s could theoretically work. I'll be sure to take a look at those diagrams. An inflating torus would be very cool. I'm trying to think of methods of attachment. I could always put another hidden stack-node inside the engine. Otherwise, breaking the torus up into a few radial pieces would also be doable. Once we have 1.1 in-hand, I can take a closer look at how the inflatable shield works, and maybe work from there. Great ideas!

 

7 hours ago, Jay Mission said:

I was wondering if you had considered that the nozzle is all one piece like in the photo with the gentleman in the suit. Maybe think of the nozzle extension less as "turkey feathers" like you would see on a jet engine, and more like "umbrella". Or, maybe even more accurately, (I'm going to loose my man card for even mentioning this) a woman's pleated skirt. The nozzle extension looks to be on the outside of the first stage tankage, represented by the dark grey texture applied to your model. The blueprint also shows what appears to be three (pyrotechnically released?) straps that hold the nozzle closed against the first stage until staging occurs. If Sea Dragon has a diameter of 75 feet, then my math comes out to be about 166 feet for the nozzle exit diameter when open. Anyway, just my 2 cents, could be wrong. Feel free to ignore if you already knew this.

 

I was starting to suspect the same thing. I don't see how else it would go from a corrugated cylinder to a smooth cone, short of flexing and "un-pleating" it. I won't be able to animate that, I don't think. Sliding and overlapping pieces, like the jet engine nozzle, would be more possible. I'll give it some thought. Part of the challenge is in having the engine extension protrude between the stages, and still have attachment work as intended. I can change the attachment point on the second stage to be on the engine instead of the tank (right now both the second stage engine and first stage tank attach to the second stage tank, and not each other), but it's unclear if that would hose up any saved vessels people have already made. I don't think it'll screw them up, because it's non-crossfeed node that I'd be removing. But even if it does... well... that's what the "alpha/beta" warning is for.

 

 

 

 

[NecroBones]

 

Thinking some more on the "flare" inflatable drag system--  I'll probably either have to build it into the engine (assuming it could be made non-staging, so it doesn't inflate as soon as you launch), or else fudge its location entirely. Since the majority of the engine model is on a gimbal, I can't make an attachable part that goes onto the combustion chamber. If it's a separate part, it'll need to attach up near the static part of the engine, or as part of the tank's skirt extension. I'm not sure which choice is better right now.

 

For the upper stage's extending engine bell, to make it more like the diagrams, and have it shroud the lower stage tank, I think I'd have to do what I said earlier and make the attachment points use the engine to attach the lower stage to the upper stage engine, rather than tank-to-tank like it is now. Something I could consider doing is having two versions of the engine-- Keep the current one, but also add the variant with the more "realistic" extension, and just space the attachment point slightly differently so there's enough of a gap between the tank skirts (interstage area) to allow the bell extension to protrude through.

 

Thinking aloud here, mostly, but it's also helpful to get feedback before I commit anything to 3D.

 

[Jay Mission]

On ‎3‎/‎30‎/‎2016 at 6:43 AM, NecroBones said:

just space the attachment point slightly differently so there's enough of a gap between the tank skirts (interstage area) to allow the bell extension to protrude through.

To me, this seems like a good direction to go. For the record, I know nothing about Unity and what is/isn't possible. I also don't want to sound like I'm trying to tell you how to build your rocket. I'm just curious. 

Question: how thin do you think you could make the nozzle extension geometry before running into problems with it rendering correctly?

I'm assuming that there has to be some amount of "thickness" so that the texture normals can face their correct ways on the inside and outside of the nozzle. Or is it possible to have a true 2D polygon that can have visible texture when viewed from either side?

Question: Can texture/bump maps be animated in Unity?

Would it be possible to model the extension as simple geometry that animates from cylinder to cone while at the same time have the texture/bump maps animate from "pleated" to "smooth"?

Question: how do you achieve the engine "heat glow" effects in Unity? If the extension is part of the engine "part" would it glow as well?

The real-world Sea Dragon nozzle extension was to be radiatively cooled after all. (maybe not enough heat flux to actually make it glow, but for KSP it might be kinda cool.)

[NecroBones]

8 hours ago, Jay Mission said:

To me, this seems like a good direction to go. For the record, I know nothing about Unity and what is/isn't possible. I also don't want to sound like I'm trying to tell you how to build your rocket. I'm just curious. 

...

 

Hi there! I can answer some of that, for sure.

 

Technically, the geometry for the extension could be 2-sided polygons (infinitely thin). Basically in Blender, you just make the same polygons twice, one facing inward, and one outward. Some problems arise in that it's often obvious that it's paper-thin, and also the collision meshes can't be that thin, so if it's going to be collidable, there should be at least some thickness. Also, if panels are going to slide into one another for animating, some parts probably need to be thicker than others.

 

I'm not sure if Unity can animate bump/normal maps, or textures. My suspicion is somewhere between "no" and "it would be really difficult". However, KSP itself doesn't support it.

 

The "heat glow" is just a simple animation that alters the overall color and brightness of an emissive map on the texture. I could either make the engine extension glow, or not, as long as it's part of the engine itself. For instance, if it were a separate part that you stick on in the VAB, there wouldn't be a way to link the animations. But I'm planning to build it into the engine anyway.

 

As an aside, I probably won't be working on these things for the Sea Dragon right away. I'm still working on KSP 1.1 cleanup on my other mods, and also I have no idea when Hangar Extender will be updated for 1.1, and I've already changed my test environment over to 1.1. Worst case, I can still work from a 1.0.5 environment, but I'm trying to keep everything consolidated if I can.

 

[NecroBones]

 

Once this is done processing, you can see a test of the recovery flare:

 

 

 

[NecroBones]

 

I figure we should get the pain of moving around attachment nodes earlier rather than later. Here's 0.3:

 

0.3 (2016-04-02) - The Sea-Recovery Update.
 - Increased crash tolerance of first stage engine and tank to 150 m/s to support oceanic crash-landing recovery.
 - Removed stack attachment node from end of skirt extension on second stage tank, and instead added it to second stage engine.
 - Added inflatable "recovery flare" to the first stage engine, and updated sample rockets to put it on action group 2.

 

[NecroBones]

 

The included sample rockets apparently lock up KSP 1.1 when you try to deploy them. I'm going to post a hotfix shortly that has updated .craft files.

 

In the meantime, here's a new view of two Sea Dragons at KSC.

 

 

 

------------------

 

EDIT:

 

OK, posted.  Version 0.3.1 will work both in KSP 1.0.5 and 1.1, it's just the "craft" files that have changed. If you want those to work in KSP 1.0.5, then you can keep using version 0.3.

 

0.3.1 (2016-04-03) - KSP 1.1 Hotfix
 - Sample rockets were locking up KSP 1.1 when sending to the pad/runway. Updated for 1.1, but are no longer compatible with 1.0.5.
 - Sample rockets saved with fairing settings to use maximum ejection force, and 4-way clamshells.

 

[Vahal]

My first reaction looking at this thing was "mother of god! He lost his mind."  then I read again and well, It's a crazy stuff, but as usual it's really well made!

 

New challenge, transport the Sea Dragon from runway to sea. 

[NecroBones]

 

Minor tweaks today:

0.3.2 (2016-04-22) - Tweaks.
 - Added collider setting for procedural fairing base.
 - Adjusted tech node to play more nicely with Real Scale Boosters.

 

[NecroBones]

Tiny update:

 

0.3.3 (2016-05-11) - Minor hotfix.
 - Corrected staging problems in sample rockets.