Aesthetics noob attempts spaceplane makeover

[AeroGav]

Hi all,

up till now, my biggest concern has just been making stuff that works.   But seeing some of the stunning ships folks are now putting out, I've realised I can ignore this no longer.      The starting point is my Penta Star mk2 spaceplane,  an existing design that's probably my best all rounder.

https://kerbalx.com/AeroGav/PENTA-STAR-REDUX

The first flight in this incarnation reached orbit with >1500LF.   A second flight went better, with 1700 remaining.   _{Please note, it's not a true SSTO in that there are a pair of Whiplash booster jets mounted to the back of the NERVs with decouplers.  It can launch from Laythe and from Kerbin without them at lower gross weights,  but it really goes a lot better with them.   There's a small delta wing section attached to each Whiplash (0.5 lift rating) keep the relative CG/CoL the same whether Whiplashes present or not.}

A major consideration was to have the middle of the cargo bay over the plane's CG, that way the balance is the same full vs empty.  To get it there, we can only have one rapier at the back, with the weight of the cockpit balancing that out.    The two nukes have to be mounted alongside the fuselage close to amidships.

In turn, this means the wings have to be mounted to the outside of the engine nacelles in order to be outside the exhaust plume.  Appearance wise, this is something of a disaster, and creates what appears to be an obvious weak spot in the structure.

It's not the only part of the craft that's aesthetically challenged however.  I'm not convinced about that shock cone nose.  The four pairs of canards make it look like a UHF aerial.  We have a patchwork quilt of wings with the outermost set with gull-wing dihedral to provide a bit of roll stability.  Decent min-maxing but it looks like a badly assembled model, 

I eventually hit upon the idea of using modular wing connectors to box enclose the engine area, demoing the technique on my self launching, SSTO "skylab" aka "flylab".

https://kerbalx.com/AeroGav/flylab

The rectangular sections at the top of the engine tunnel are flat, and the main wings shifted up to mount flush with them.   The rectangular sections enclosing the engine tunnel from below are canted upwards to meet the main wing.  This provides the dihedral and roll stability a design needs without "gull wing" outboard sections like a Ju87 Stuka.  The additional lift from these modular wing sections means we can drop down to just two big S delta wings, which is good because beyond the back to back "rhombus" arrangement i am not sure of how to include more, sensibly.

Elevons at the front of this "engine tunnel" eliminate the need for a "UHF nose".  

When applied to the original Penta Star design, the shallower mk2 fuselage meant incorporating a flat bottom plate :

 

Now that looks a lot better ! Like a cross between a Venture Star and a 5th gen fighter.  _{I had to leave a "slot" in the bottom of the aft section of the engine tunnels so our Whiplashes can decouple without the whole ship undergoing self disassembly.}

Of course, we're now using fewer "wet" Big S wings and more "dry" modular sections to get our lift.  This means that we've got less LF capacity for no reduction in dry mass.

To an extent, this is compensated for by the use of big - S strakes agglomerated into rectangles rather than rectangular wing connectors to form the top of the engine box.   Big S strakes hold quite a bit of fuel.  Also,  I had to add another two pairs of strakes to the trailing edge of the wing to get the CoL where it needed to be , and also supply sufficient fuel capacity aft of CG (the craft would become increasingly nose heavy as the tanks were filled).   This version made orbit with 1931 LF out of 3550.

However,  it now had a fairly major handling problem.    The engines are mounted exactly halfway between the top and bottom of the fuselage, but the wings and strakes are all mounted above them.   When fully fuelled, CG is well above the engines causing a tendency to pitch up under power.  This is not so noticeable on the deck,  but at altitude the air becomes too thin for the tendency to be suppressed by aerodynamic stability.  In fact in orbit, it was impossible for capsule torque to overcome this effect and going to 100% on the NERVs would cause the ship to tumble end over end.

To compensate, I decided to build the bottom of the engine tunnel out of stakes as well. Not having cargo doors to worry about enabled me to fit 4 pairs of strakes ahead of cg, but only two pairs could go aft thanks to the space that had to be left for engine decoupling.

Still, we now had some kind of balance, in terms of strakes -

Above & behind CG  |Above and ahead CG
8 strakes          |2 strakes
------------------------------------
Below & behind CG  |Below and ahead CG
2 strakes          |8 strakes

The fuselage tanks are also perfectly aligned, height-wise, with the engines.   That left just the 2 pairs of Big S delta wings , mounted above the engine, to cause a problem.    So,  I used the new feature of 1.2 to give these a higher fuel tank priority, meaning they drain first.   By the time you're getting up to altitudes where off-axis thrust is more problematic, these tanks will be mostly used up.

Final version -

https://kerbalx.com/AeroGav/Pentastar-Santos-II

 

Umm, what the heck ! Where's all this extra delta V coming from ?