How to anchor an airplane on board?

[Sharpy]

So, I have this huge, MK4 based VTOL craft, which will be carrying a small spaceplane in the cargo bay, for launching at a good altitude. Using Airpark, the VTOL "parks" at some 20km altitude, then opens the cargo bay/ramp, and the airplane is launched, using carrier catapult.

Problem: "park" the airplane until launch. The VTOL will be doing quite a bit of maneuvering between loading up the plane and the launch. I can't just let the airplane loose in the bay. It must be docked somehow.

Nose - can't, need clear way for launch.

Tail - all occupied by engines.

Bottom - how? Extended landing gear, lift or lower it somehow onto a port? I could retract the gear to lower the plane to the port, but then going in reverse, after undocking the plane will be tossed up with gear retracted. Or if I extend the gear before undocking, the airplane will definitely jump up as soon as dock is released, with the force stored in wheel springs.

Top? Similar problem.

KAS pipes would work except you need an EVA kerbal to unlink them. And I really don't want to send a Kerbal on EVA into the cargo bay at 20km altitude.

KAS winches? The 'unplug' would kinda work, but the connection is not rigid until the winch fully retracts - and once it does fully retract, any minuscule imprecisions get corrected within a single frame time... meaning often RUD-inducing jerk.

 

The screenshot below is not the actual craft, but treat it as a situational sketch of what I'm dealing with.

 

...any ideas?

[swjr-swis]

13 minutes ago, Sharpy said:

Tail - all occupied by engines.

A docking port at the back node of a rapier can be offset into the rapier but left with its docking edge just barely sticking out, without the rapier exhaust affecting it. That way it can dock from the back and the engine will still work at full thrust.

[Magzimum]

With rovers or hoppers, I use a top or bottom docking port. I lower the hoppers onto the docking port by retracting the landing gear... or I attach the rover to an overhead docking port by extending landing legs (which are longer than the wheels its on).

[klesh]

Can you flip the cargo bay so it opens to the bottom, dock the small ship to the (now) top of the cargo bay, and let it fall out to deploy?

[Sharpy]

16 minutes ago, klesh said:

Can you flip the cargo bay so it opens to the bottom, dock the small ship to the (now) top of the cargo bay, and let it fall out to deploy?

Technically, yes, but I'll be losing a lot of altitude before I right it and get it going upwards, and I really don't want that. The atmosphere below is MURDEROUS to ISp. (Eve).

30 minutes ago, Magzimum said:

With rovers or hoppers, I use a top or bottom docking port. I lower the hoppers onto the docking port by retracting the landing gear... or I attach the rover to an overhead docking port by extending landing legs (which are longer than the wheels its on).

If I attach the landing legs to the deck, it might work. I really, really don't want to drag extra landing legs attached to the fuselage with me. The very fact I need to climb another 70km and gain good 3500m/s of horizontal velocity is enough of a challenge without landing legs slowing me down.

 

[bewing]

Do you need to do this procedure once? Or many times? If it's just once, then all you need is a decoupler.

 

[Palaceviking]

How about on the outside (yes,i know about eve drag)on the top (with a docking port)like the Virgin spaceplane first concept and maybe use a large nosecone to occlude the contraption. 

Alternatively(and far more kerbal), have it like the picture but put a large stack of decouplers underneath it to literally blast it out of the bay and upwards!  

[Allocthonous]

Stick a grapple node to a girder segment so that it can fit between the nukes and grab onto the rapier?

Are you loading the plane in strictly by the tail door? If so, a pair of docking ports on the top and bottom of that rear fuel tank that connect to ports on girder arms sticking out of the front of the cargo bay might work. Having two opposed should counter the spring force, you'd just have to set them on an action group for decoupling/undocking. Be a bit tricky to dock with, but should still be doable.

[Sharpy]

10 hours ago, bewing said:

Do you need to do this procedure once? Or many times? If it's just once, then all you need is a decoupler.

 

Fully repeatable. The airplane might be single-use, but the launches will be repeated and the large craft will be a permanent (though mobile) Eve base.

 

9 hours ago, Palaceviking said:

How about on the outside (yes,i know about eve drag)on the top (with a docking port)like the Virgin spaceplane first concept and maybe use a large nosecone to occlude the contraption. 

Alternatively(and far more kerbal), have it like the picture but put a large stack of decouplers underneath it to literally blast it out of the bay and upwards!  

Outside would be okay if I had means to attach it there "out of VAB". The whole procedure of placing the airplane needs to be performed on Eve surface (or if I'm really insane, mid-flight.) Drag during the lift to 20km is non-issue; the "mothership" will be quite draggy, using either electric turbofans (with a nuclear reactor) or a blimp for lift; it's not meant to be fast and its lift is nearly free. But it won't have very much ground clearance to drive the airplane under the hull, nor a tall crane to place the plane on top of the hull.

And I won't be able to set up staging reliably; this will have to be activated through right-click menu, so no blowing up a stack of decouplers.

7 hours ago, Allocthonous said:

Stick a grapple node to a girder segment so that it can fit between the nukes and grab onto the rapier?

Are you loading the plane in strictly by the tail door? If so, a pair of docking ports on the top and bottom of that rear fuel tank that connect to ports on girder arms sticking out of the front of the cargo bay might work. Having two opposed should counter the spring force, you'd just have to set them on an action group for decoupling/undocking. Be a bit tricky to dock with, but should still be doable.

That's actually a very good idea! Nothing to add to the airplane surface (no extra drag) and I think I have just the right part for the job.

Buffalo Grappler Arm, acts just like the Klaw, except it's a small grappler on an extendable arm. There should be no problem grabbing the plane. (although driving it into the bay will still be fun, especially if the bug of the game crashing when docking active craft to a Klaw was not fixed.)

[bewing]

3 minutes ago, Sharpy said:

especially if the bug of the game crashing when docking active craft to a Klaw was not fixed

It was fixed in 1.1.0

[Palaceviking]

So to clarify,  is the space plane already on eve?

[Sharpy]

15 minutes ago, Palaceviking said:

So to clarify,  is the space plane already on eve?

Nothing (save from one entirely unrelated lander) is on Eve right now.

Nothing is totally set in stone.

The Eve mobile base is about 70% complete. Today I was experimenting with trying to construct the plane.

It would be awesome if the plane was totally reusable on Gilly-Eve route: Launch from Gilly, enter Eve, land near base, load the plane, exchange cargo in/out, refuel, fly the base up to 20km, launch plane, fly it to Gilly.

That goal is quite unrealistic though. Good 5000m/s at Eve gravity's TWR>1 in SSTO small enough to fit in the MK4 cargo bay is quite hard, even if launching from 20km. That means it will likely not be SSTO; not reusable.

Fallback plan:

Both bases have the Extraplanetary Launchpad capabilities, so the plane can be built on site and optimized for ascent without worry about reentry, it can also use staging. Gilly launches a 'drop pod' lander with Eve inbound payload. Lander lands, Base flies to pick up payload, scraps the lander, manufactures plane, loads up outbound payload, rises to 20km, launches plane to Gilly. Gilly receives payload, scraps whatever remained from the plane.

 

tl;dr the plane is currently a vague concept.

[Palaceviking]

Spoiler

 

Now i understand the complexity of your problem.