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1 hour ago, THE NARWHAL said:

Usually SSTOs are fast and lean. Those two things do not go well with 'flying boat.' However, i have to give you points for originality. Maybe a modified Sea Dart lookalike could work?

Entirely possible.

So build it and post the pics. :)

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Good timing on this post - here's one I've been working on for quite some time.  Capable of landing and take-off on sea fully loaded with fuel on both Kerbin and Laythe.  Massive flaps with appropriate deploy limits give it huge low-speed lift, no stall at full back stick, then retract to zero AoA so the ~3deg AoA on the main wing can finish the burn to orbit with minimum drag.  Runway takeoff at around 40m/s, water takeoff about 50m/s on Kerbin.  Laythe with its thinner atmosphere can require a small surface dive-climb maneuver, or a pulse of rocket power to get out of the water drag.  Reaches 1490m/s on jets, and attains orbit with 800m/s in the tank for rendezvous maneuvers at Kerbin.

It has some odd features because this is part of a flexible Grand Tour plan - the wing and engine modules undock for stowage in a Mk3 cargo bay.  Its alternate configuration is for vacuum operations - vertical landing on a Terrier and wide landing leg module at the rear, with optional fuel tank and boost engine modules for Tylo (design still underway but it looks good so far in testing).  I'm also testing putting the rear control surfaces below waterline (along with front wet canards) to use the hydrofoil effect to lift the main fuselage out of the water - in testing this looks like it'll let me get away with less mass in flaps and safer fully-laden water landings (the shock cone is fragile if you don't get the speed and AoA at splashdown just right).

Edited by fourfa
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My first and only, a hydrofoil based seaplane ssto.   Packs a fair bit of delta V, should be interplanetary.

https://kerbalx.com/AeroGav/K133--Curlew

 

20170101143853_1_zpsngsd7hah.jpg

I had a brain fade when i created this aircraft,  I deliberately added more lift on the front hydrofoil than on the rear, thinking this would encourage it to plane.     In fact i think I just made a craft that has negative pitch stability when in the water (CoL in front of CoM) , it always either tries to bury its nose (on landing - fortunately landing speeds are so low there is no damage, but not elegant)  or it pitches up as far as it can (with the front foil just starting to come out the water and the tail still dragging).

If i had my time again, i'd design this out. 

Also,  i added two Junos for extra propulsion.  Yeah, Junos !     Perhaps a larger, mk2 seaplane would use two panthers and one rapier, but Junos are the only jet engine small enough to supplement the RAPIER when mounted in pairs  - saves having to worry about off axis thrust.

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Gav if you play with hydrofoil forces some more - you might find that you don't need nearly so much surface area.  The hydro-lift generated (it's hard to quantify because AFAICT there's no readout in any of the deep menus) is much, much larger than aero force.  I have been able to lift a similarly-sized plane out of hydro drag with just front and rear pairs of Elevon-4s, mounted at 45 degrees like a V, set to deploy in water (at only 30-40%!) and retract to 0 AoA in takeoff.

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So this one's not an SSTO, but it could easily be made to be by dropping one of the passenger compartments, adding oxidizer and switching the Wheesley for a Rapier (I've done this). I'm going to post it here because it's fun. It was designed to fit in a MK3 cargo bay for transport to Laythe where it was to be used as a commuter / transport for ferrying kerbals between surface outposts.

https://kerbalx.com/NoobTool/Stinger

4rciqbJ.jpg

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S9OWvnz.jpg

Can land on and take off from land or water.

uSkTNtR.jpg

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It's remarkably stable on the water. I've achieved speeds of nearly 270 m/s before the craft spontaneously lifted off the surface on its own accord. This is pure dumb luck, I haven't been able to replicate this type of performance in any of my other hydrofoil designs.

ETdKcsz.jpg

It's also stupid fast in the air for something powered by a Wheesley. It can reach speeds in excess of 600m/s, though this is not recommended. The engine overheats at this speed and that heat is transferred through the fuel tank to the passenger cabins. Exceeding recommended cruising speed (~510m/s) for long periods can void warranty.

uAKZPel.jpg

It also has quite a range. Flying at cruising speed at >8000m altitude, it circumnavigates Kerbin with a comfortable fuel margin. I've had a lot of fun with this little craft, and probably spent way more time "testing" it than could ever be justified. Funny how the simplest designs can be the most rewarding.

Edited by NoobTool
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On 16 April 2017 at 2:45 AM, fourfa said:

Gav if you play with hydrofoil forces some more - you might find that you don't need nearly so much surface area.  The hydro-lift generated (it's hard to quantify because AFAICT there's no readout in any of the deep menus) is much, much larger than aero force.  I have been able to lift a similarly-sized plane out of hydro drag with just front and rear pairs of Elevon-4s, mounted at 45 degrees like a V, set to deploy in water (at only 30-40%!) and retract to 0 AoA in takeoff.

Big 'un on just two pair of flat hydrofoils (both activated as flaps when in the water):

kXaeecp.png

ccq1GUD.png

The floats on that are just to keep the engines above the water while stationary; largely cosmetic. They barely touch the water at speed.

 

A planing hull on a little 'un:

eRsODrX.png

uh5XzvY.png

The floats on that one are for landing stability; again, not strictly necessary.

 

Similar ship on a single pair of hydrofoils:

kyEIAmR.png

It usually requires about 30m/s of waterspeed to get up onto the foils or planing hull, but if you can do that it requires very little in the way of foil to lift even a large ship out of the water.

Fine tuning of position and deflection angle is required, though. At least one pair of foils under CoM; if you've got a second set, stick 'em as far forwards as is convenient. Tweak the deflection settings so as to trim the craft level while moving over the water.

Required settings may change with speed, particularly the balance between front and rear. I have some planes where, for best performance during acceleration, you want to deploy front foils only at first, then both front and rear foils, then rear foils only. I've also had good results come from keeping the front foils active as pitch control surfaces; smooths out the pitch trim in the water, and useful in the air as well.

Once you're up onto foils, the only real restriction on your top speed is how long you can keep it stable and prevent it from spontaneously taking to the air. Tweaking foil deflection settings just right can often turn an unstable hydrofoil into a smooth one.

Edited by Wanderfound
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  • 2 weeks later...

Only because I haven't seen a decent one done in a while, I've been working on a Conwing L-16 cargo seaplane. It's not an SSTO, yet... that could be in the works for the future but it'd require quite a bit of redesigning.

 

uhThSON.jpg

 

It's still a work in progress.

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Here is my OPT K76  LF Seaplane tanker (LF for liquid fuel only)

Can take off from ground, max take off weight is 532T with 75500L of liquid fuel, running on 2 OPT J61 Starwaster, 2.6m. Cruise altitude 18-20km at Mach 4.4

The OPT drop tank MK1 at 380%, full of liquidfuel, are the best floating tanks i know. Their limitation is 1200° and that's why mach and cruise altitude are limited.

287017screenshot66.png

Landing is easy, 120m/s V/S around 3-5m/s

The tanker is equipped with fuel pipes and winches to deliver fuel to my "Gliding Cheetah" Catamaran during my Maritime Elcano Challenge. You can see some pics here during refueling mission, there's a short vid , later in the story.

 

Edited by gilflo
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On 2017-4-30 at 3:55 PM, Speed_Kerman said:

Only because I haven't seen a decent one done in a while, I've been working on a Conwing L-16 cargo seaplane. It's not an SSTO, yet... that could be in the works for the future but it'd require quite a bit of redesigning.

 

uhThSON.jpg

 

It's still a work in progress.

 

Minimum change SSTransfOrmation -

  • Whiplashes, swap those for RAPIER
  • Circular intakes, swap for shock cones
  • The floats can incorporate some kind of inline intake so cover the low speed portion of takeoff when the shock cones aren't efficient eg. engine nacelle intake?
  • The bi-adapters they are mounted on, get swapped for tri-adapters and put Panthers on the bottom node.   This ensures it has enough thrust to break free of the water and go supersonic at altitude
  • The tail booms can be made from FT800 tanks instead 
  • Because the oxidizer is stored well to the rear, you'll need some oxidizer up front or the craft will be unbalanced.  Short rocket fuel fuselage behind the cockpit maybe?
Edited by AeroGav
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1 minute ago, AeroGav said:

 

Minimum change SSTransfOrmation -

  • Whiplashes, swap those for RAPIER
  • The bi-adapters they are mounted on, get swapped for tri-adapters and put Panthers on the bottom node.   This ensures it has enough thrust to break free of the water and go supersonic at altitude
  • The tail booms can be made from FT800 tanks instead 
  • Because the oxidizer is stored well to the rear, you'll need some oxidizer up front or the craft will be unbalanced.  Short rocket fuel fuselage behind the cockpit maybe?

Maybe... I'll work on it this week whenever I fire up the gumption to do it.

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hMM,

 I did have a go to recreate this, but it proved unable to get out of the water.  The oxidizer and extra engines mean the floats are submerged, which probably means drag.   "Moar boosters" doesn't seem right,  because it's already got a TWR of 0.6 yet that only gets us moving at 35m/s through the water.  If you're going for more engines you might as well just add a VTOL.

Making it go fast through the water has to be the hardest part about building a seaplane and i'm not sure what the rules are.   The fact you don't get any helpful indicators in VAB and that water drag doesn't show up in the right click menus doesn't help. 

 

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2 hours ago, AeroGav said:

hMM,

 I did have a go to recreate this, but it proved unable to get out of the water.  The oxidizer and extra engines mean the floats are submerged, which probably means drag.   "Moar boosters" doesn't seem right,  because it's already got a TWR of 0.6 yet that only gets us moving at 35m/s through the water.  If you're going for more engines you might as well just add a VTOL.

Making it go fast through the water has to be the hardest part about building a seaplane and i'm not sure what the rules are.   The fact you don't get any helpful indicators in VAB and that water drag doesn't show up in the right click menus doesn't help. 

 

I agree, the added mass would make a water take off or landing difficult on full tanks. However, that being said, I did design something that can get in to space. Water take off on full tanks is untested, as full of fuel it does weigh over 100 tons... That's quite a weight gain from the 48 tons that it used to weigh.

In a stable 80 km orbit, it had just under 900 m/s Delta-V to play around with. I angled a couple of the Rapier engines I was using downwards to help with getting quick lift from the surface of the runway.

I present, The Conwing L16-S!!

If interest warrants, I'll post a craft file later.

Edited by Speed_Kerman
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  • 2 weeks later...

Has anyone here been able to build one of these with a full size mk3 cargo bay with cargo to orbit capability? I got close, but then realized using the cargo bay as the main boat hull results in the contents being destroyed on landing. The only solution I can think of is to make a double-decker fuselage or have some crazy oversized floats, but both of those options bring more challenges like dealing with a lot of dead weight or figuring out how to load and unload cargo to the second floor.

Any ideas?

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21 hours ago, Skyshrim said:

Has anyone here been able to build one of these with a full size mk3 cargo bay with cargo to orbit capability? I got close, but then realized using the cargo bay as the main boat hull results in the contents being destroyed on landing. The only solution I can think of is to make a double-decker fuselage or have some crazy oversized floats, but both of those options bring more challenges like dealing with a lot of dead weight or figuring out how to load and unload cargo to the second floor.

Any ideas?

I think you are just touching down too fast.  I can land mallards full of science jr. and keep them intact.  You just need bigger wings I guess.

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On 5/17/2017 at 0:12 PM, Skyshrim said:

Has anyone here been able to build one of these with a full size mk3 cargo bay with cargo to orbit capability? I got close, but then realized using the cargo bay as the main boat hull results in the contents being destroyed on landing. The only solution I can think of is to make a double-decker fuselage or have some crazy oversized floats, but both of those options bring more challenges like dealing with a lot of dead weight or figuring out how to load and unload cargo to the second floor.

Any ideas?

I built one a long time ago when the water was first made like it is now, but I abandoned it after I realised that while it could get to orbit it was never going to do anything useful

 

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21 hours ago, selfish_meme said:

I built one a long time ago when the water was first made like it is now, but I abandoned it after I realised that while it could get to orbit it was never going to do anything useful

 

Looks like you lost a docking port there.

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