Miuramir

Just for some real world reference, diameters of some famous real world airship main envelopes: New Zeppelin NT (such as the newest Goodyear Blimp): 46' dia (~14m) Ex-LZ-120 Bodensee, later Esperia; and Ex-LZ-121 Nordstern, later Méditerranée: 61' dia (~18.5m) Ex-LZ 126, later USS Los Angeles ZR-3: 91' dia (~27.5m) LZ-127 Graf Zeppelin: 100' dia (~30.5 m) LZ-129 Hindenberg: 135' dia (~41 m) R-101: 130' dia (~39.5 m) It seems reasonable to have 10m, 15m, 20m, 30m, and 40m standard envelopes, or at least configurations for TweakScale. (I'm not a fan of TweakScale in general, as historically it's been a bit flaky; but in cases like this it may be useful.) Note that the #1 hangar shed at RAF Cardington is about 812' long x 275' wide x 180' tall (~ 247.5m L x 84m W x 54.5m T), and was specifically designed to hold two R-101 class airships side by side. The shed at Karachi (then part of British India) was nearly identical. Fictionally, the "steampunk" campaign I run puts the airship research much earlier (justified, but long story), and assumes the R-101 didn't crash and the famous "Imperial Airship Scheme" of the 1920s was started on in the 1860s. The logical next development for heavy lift was a "catamaran" design "R-200 class" with two R-101 hulls attached side by side, just able to fit in the existing shed. Subsequently, it was shown to be under-powered (as has happened many times in the history of rigid airships), and a third, smaller envelope was added nestled in between the others along the top. Two nominal 40m envelopes side by side with a nominal 30m envelope along the top would be a reasonable enough match for my purposes.

What I do have: saved copies of the following 1.2 pre-release builds; those in (parens) are zips or patches that I never tested as I didn't have time before the next version was out: 1473, 1479, (1486), 1489, 1509, (1520), (1523), (1532), 1548, 1553, (1564), 1569, (1584), and of course 1.2 "final" release version 1586 (I also still have copies of 1.1.3, and a selection of earlier versions) I've grabbed 1.0.0.4 of @Padishar 's frame rate tool and will give it a whirl. My usual system is an ASUS G55VW-DH71 laptop (Intel Core i7-3630QM CPU @ 2.40 GHz, 8 GB RAM, Win 7 Pro x64, NVIDIA GeForce GTX 660M, main drive replaced with SSD). What I *don't* have is a lot of free time. If folks can agree on particularly relevant test craft, test profiles, and selected versions of interest from the above, I'll see what I can do. Note that given the limitations of stock installs and to reduce variability, some sort of "spacebar and straight up" rocket test is going to be a lot more repeatable (and statistically meaningful) than fiddly space-plane trajectories.

I may be able to help some here; I should have at least four different versions of pre-1.2 beta builds still installed at home, and if I scrounge through my downloads folder may be able to dig up a few more that I didn't get around to testing before the next version dropped. Note discussion above about changes to aero effects and drag; I'm definitely noticing that some of my aerospace planes are harder to push through the "mach wall" region than before, which will have side effects. Also, one of the things I distinctly remember from earlier betas was that at first, auto-strutting seemed to be practically magic. IIRC it seemed like it would turn a plane that would disintegrate half the time at 3x and ran yellow-red, into a plane that ran smoothly at 4x mostly in the green. It seemed closer to part welding than strutting, really. I can't be sure, but I am guessing that something about it has been dialed back or changed; and that has a significant side effect on frame rates, as the game "wastes" a lot of calculation time calculating parts wobbling about subtly, which then causes more aero issues and even more calculation.

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.

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

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/

I've been a fan of Sea Dragon for decades, and I've been wanting a KSP mod for this since KSP has had mods. Major kudos for doing this, and I've got high hopes. For those wondering *why* anyone would do this, one of the points of Sea Dragon was that it would be *cheap* on a per-pound-to-orbit basis. It was as large as it was on purpose, to allow it to be built from (comparatively) inexpensive industrial and shipbuilding materials, in a more-or-less ordinary shipyard. Estimates were $20/pound in 1983 dollars, still less than $50/pound today. From a KSP perspective, it's a small number of simple parts to lift big things, which is also handy. It's also historically been considered as one of the few logical ways to launch a good-sized Orion nuclear pulse drive out of the biosphere for interplanetary use, for those days when alien invasion isn't imminent and you're feeling a bit squeamish about all those nukes going off on the way up. First test, "stock" version: Generally awesome. Stability under physics warp is excellent, and I was wondering whether you'd gotten then nosecone-in-engine-bell working, and it looks like it does! I'm pondering whether the side-mount steering engines should be treated as very large LF+O RCS? Tradeoffs either way; perhaps there should be two versions, one as-is that's throttle controlled, and an otherwise identical version that is hooked into RCS logic?