on super-heavy air-breathing (space)planes

[Cirocco]

As for lift, if you make your wings double thickness, you'll get acceptable lift and the wings themselves will look more realistic due to looking thicker.

how do you mean? Just layering them one on the other and slightly clipping them into one another with the gizmo's?

I must admit I've been considering doing things like that. Enveloping the entire plane tructure in a big delta wing was another idea I was toying around with.

[MockKnizzle]

Larger planes will always struggle thanks to the square-cube law. You need proportionally much more wing for a Mk3 spaceplane compared to something smaller. Additionally, the big parts don't have any body lift to help out.

[Hodo]

Hello all,

so I've come back to KSP after a few months of dry spell and as I always do when I'm given new spaceplane parts, I immediately went to work on heavy-duty, interplanetary SSTO spaceplanes. A ton of people have used the Mk III parts for space shuttles (and I don't blame them, space shuttles look awesome), but I haven't seen many people using them for air-breathing SSTO spaceplanes.

And then I found out why.

The new Mk III parts are REALLY heavy when compared to the Mk II parts. That also means that in comparison, turbojet thrust is REALLY low. Seriously, even small Mk III spaceplanes immediately go over 80 tons and require 8 or more turbojets.

So I'm wondering: what have you guys built in terms of the heavy and super-heavy (90 tons and up) air-breathing spaceplanes?

Also: that bug that reverses the pitch on control surfaces placed near the CoM of a plane is really annoying. Anyone know any fix to that?

I have been building heavy SSTO space planes since well before the new MK3 parts came out. And it isn't much different with a 300+ ton SSTO that can haul 108tons to orbit then it is with a 30 ton SSTO that hauls itself to orbit. The thing is you have to keep your TWR at the right areas and you L/D ratio perfect for most of the flight. After you get to a certain speed and your rockets take over you are no longer concerned with your wings or your intakes and you are now just a heavy rocket with a considerable speed advantage.

The hard part is finding the time to launch things like that now....

[Cirocco]

After you get to a certain speed and your rockets take over you are no longer concerned with your wings or your intakes and you are now just a heavy rocket with a considerable speed advantage.

Well yeah, once you hit the upper layers of the atmosphere and switch ot rocket engines you're basically flying a rocket. What is becoming hard for me in the heavy and super-heavy airbreathing SSTO's is getting to that height and speed efficiently. I could easily build a rocket-powered spaceplane and fly it up to orbit, but then I'm basically building a rocket with wings. If I do that I think it would be far easier and more efficient to go the way spaceX is going and use a rocket which I can bring back through powered landing. The goal here is to reduce flight cost even further by eliminating the need for oxidizer and using very efficient engines for a large part of the ascent.

The small radius tanks and MkII spaceplane parts both don't weigh that much for their volume. So a fairly large plane built with those was still within acceptable weight class and a decently sized wing meant you could get away with a fairly low TWR. With the MkIII parts however, these things weight a bloody ton and pack a huge amount of fuel. That's great for when you're building cargo haulers which have a large bay and no too much room for fuel tanks, but it becomes a pain when designing large, interplanetary ships without cargo bays: you have a really heavy and compact ship requiring huge wings (or more thrust to make the smaller wings more efficient) and a lot of small engines (seeing as we don't have 2,5m airbreathing engines at the moment). That's a lot of stuff to be attached on a compact ship.

Note that I'm not saying the Mk III parts are unbalanced or that I want them changed in any way, they just pose an engineering problem that I haven't yet learned to work around in KSP.

[Van Disaster]

does this work with far?

No, that will definitely not work with current FAR - it'll think there's two wings stacked on top of each other and apply biplane effects, and you'll lose a lot of lift.

[DunaRocketeer]

how do you mean? Just layering them one on the other and slightly clipping them into one another with the gizmo's?

Yep, that's what I end up doing.