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SAR Water Vessel Construction


Mister_Spaceman
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With the SM Marine mod seemingly defunct, a lack of other civvie ship mods, and a burning desire to bring "Death to the Green Button" (Credit to @RealKerbal3x for the idea), I've decided to start building ships capable of bringing crew capsules back to the KSC. However, I haven't a clue wher to start. I've never built any stock vessels capable of water transportation (not well, anyway), much less pick up a capsule and carry it home. I have an idea of the basic requirements:

  • Bouyant parts (for floating)
  • Non-bouyant parts (far not floating too much)
  • Engines and air intakes (for moving while you float)
  • Some sort of crane system, most likely modded (so the thing can pick up a capsule)

My question is, how does one build a ship with a large enough cargo deck for a crew capsule? What are some tips for proper balance, effecient construction (low part count), and general things to keep in mind for seagoing vessels? I've noticed a thread or two that may help greatly with this, namely some of @Triop's circumnavigation threads. Any threads that may serve for good inspiration? Are there any mods I'm missing that may help with the whole ship thing?

 

Moderators- Feel free to relocate this thread if it belongs elsewhere. I can't tell if it's at home in the questions subforum, or the spacecraft exchange.

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Bouyant parts (for floating) 

Non-bouyant parts (far not floating too much)

Pretty much every part except full ore tanks in buoyant. Interestingly the medium sized rotor sinks while the other two float. Aside from it, I haven't found any other non'ore tank part that sinks. Even structural girders float (hmm, maybe I should try I-beams).

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Engines and air intakes (for moving while you float)

When operating on kerbin, I'd say the best engines for a boat are goliaths, due to their high Isp. Air intakes will work above and below water, as will jet engines (that's KSP for you).

If you want, you can use the breaking ground rotors to make screw propellers:

kLruZdA.png

Spoiler

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But Jet engines are simpler and more powerful, particularly if you don't care about neutral buoyancy as with a sub. Before breaking ground I used them to make subs (wouldn't work on Eve, or a mod world like Tekto though) where the sub would start slightly heavy and would slowly sink when full of liquid fuel, and would slowly rise when empty. The low fuel consumption of jets meant that short trips had very minimal buoyancy changes.

SibS7yU.png

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boats are much easier, just about anything floats. You have to try to not make it float. So just take some mk3 fusalages (high impact tolerance), and put some jets on them... like this without wings, and more efficient jets:

a3WptmK.png

Paddlewheels can work too, but they are slow, as this pre-breaking ground (using the old separate craft for rotors trick) demonstrates.

R4tEbQy.png

2 hours ago, Mister_Spaceman said:
  • Some sort of crane system, most likely modded (so the thing can pick up a capsule

If all you want to do is pick up a capsule, then the current robotic parts are plenty. I tried to make something that could lift a half fueled Rockomax jumbo 64... it was... bendy.

I could have stengthened it, but my design goal was fitting it in a mk3 cargobay:

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A recovery boat doesn't have the same restrictions

 

Edited by KerikBalm
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@Mister_Spaceman

My approach to 'Death To The Green Button' (maybe it should be a challenge :P) uses airships from the Heisenberg mod, rather than boats, because airships are much faster and less hacky (no mucking about with buoyancy). I also use KAS winches to pick capsules from the sea, rather than the DLC robotics. Don't get me wrong, the robotics are awesome, but I don't use them partly because giant claws are a bit unnecessary when the largest thing you'll pick up is a Mk1-3 pod, and partly because the robotic's joint strength is pretty low, leading to some contraptions flopping about and Krakenising (tm).

I've only dabbled in building watercraft in KSP, but if that's what you want to do, good luck. As @KerikBalm said, the ore tanks are pretty much the only things that sink. If you want to get anywhere fast, I'd recommend building your recovery vessel as a hydrofoil, something like this:

 Image result for hydrofoil

These are possible in KSP, it's just like a plane, but in the water. Just add a few wings under the hull near the front and if it's going fast enough the prow of the boat will lift out of the water.

 

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I think the ore tanks all have approximately the same density/buoyancy.

Under almost all circumstances MK2 parts have the worst drag in both air and water, vs. their frontal area. MK3 parts are second worst, but if you want to make large craft for aesthetic reasons -- go with MK3. MK1 parts have the lowest drag, and will give you the best overall performance. Of course, if you just want more speed, simply add moar engines.

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I'd say go for Mk3 for the carrier with the crane. It isn't the most hydrodynamic, however it has very good crash tolerance of 50m/s and are larger bulky parts. If a crane is used you need some mass in order not to capsize. This means hitting the water or driving out of the water at speed wont ever destroy the vessel.
Stage activated Vector engines are the best sinkable parts. That means a Vector that is staged sinks faster then one that isn't staged? What?? Yeah, what indeed :) 

Out of all the ore tanks the radial one is the densest, so if you want as much heavier then water mass kg for kg you should use those. For submarines the SM-25 making history service module is the most hydrodynamic. It doesn't sink but you can stuff it full of Vectors or ore ballast. It also fits inside the Mk3 cargo bay. Best would be to emerge from the water inside a center mk3 cargo bay with a piston to tow it back into the cargo bay.

As for engines, I'd go with the Goliath. 2 reasons...

1: It is the most efficient. People want to go very fast on water but the faster you want to go the more power you need exponentially so the less distance capable to travel. Building a high quality hydrofoil or small footprint catamaran will be most efficient when coupling with the Goliath. Best is to make a high quality prop for infinite action radius.
2: The other reason is that the Goliath is very buoyant. So if you place them slightly on top of the water it will help with floating and stability. It will slow down the vessel so only use them when peed is not your goal.

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These are all good points. I'm already learning a bit about Kerbal watercraft. :) I'm considering a either a hydrofoil design with hydrofoils that can fold back into the hull during recovery for hi-speed fun, or a screw-prop design for a challenge. What I'm most unclear on is how to go about the hull. Do traditional "Vee" hulls really work in KSP? Stock ships I've seen tend to look like flat-bottom ships, but perhaps I haven't had a good enough look. From what I understand, MK-2 parts generate the most drag in water, and are thus the most ineffecient for water travel. Is this simply hearsay, ir is it best to build with MK1 and/or MK3 parts? The small radial ore tanks are the most dense ones, right?

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Well, unfortunately, I've discovered that this form recovery is not an option. The game is far too laggy for anyhing seaborne. A testbed I'd made with <30 parts had my game running at less than 10 FPS. :( Thanks for your help, folks. Perhaps it will come in handy when I save up enough for a decent computer. :)

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Particle effects destroy framerate when moving on water. Those nice white splashes. You can adjust those in the settings. Why not give that a shot and try again?

I have a decent computer and the game still chugs whenever something splashes into the water if I have particle effects tuned up to the max. Something SQUAD ought to address... when they get around to it.

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2 hours ago, Brikoleur said:

Particle effects destroy framerate when moving on water. Those nice white splashes. You can adjust those in the settings. Why not give that a shot and try again?

I have a decent computer and the game still chugs whenever something splashes into the water if I have particle effects tuned up to the max. Something SQUAD ought to address... when they get around to it.

Yea, I found that my subs worked fine underwater, but when they were at the surface with the props splashing, the game slowed to a crawl. Oddly, I think it played smoother with scatterer.

If all you want is capsule recover, I'd say fly there in a seaplane with a simple articulated claw on a telescoping hydraulic cylinder

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Good points. I didn't realize that the particle effects are so resource intensive. I'll try turning them down when I get home and see how that goes. Is there a way to only turn off specific particle effects, i.e. the splashes? What do you folks recommend for BG Rotor-powered propellers? I imagine that they're fairly simple, a few stacked rotors for maximum RPM, and slightly angled control surfaces? 

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