Docking across the atmosphere edge

[Sharpy]

I was thinking of creating a skyhook.

It's unlikely for me to find much success, both due to KSP's inherent limit on spacecraft size, the durability of such construction, and the absolute nightmare of docking at the right place, at the right nick of time, at the right speed. Still, I thought of one more limitation:

Craft A is a 400m tall vertical tower with both root part and CoM placed somewhere at 70.010km orbit. That means top orbits at 70.030km and the bottom at 69.990km. Which means the bottom is in the atmosphere (but the craft considered as a whole is already "in space", no atmosphere rules apply.

There's a docking port on the bottom of the tower.

Now I'm docking another small craft to it. Since it's still "in the atmosphere", atmospheric physics rules apply.

How will the game engine handle this? Did anyone try?

[bewing]

When you dock two vessels togther, the game seems to randomly choose one of the vessels as being the "main" one. So if it chooses the small craft in atmosphere as being the main craft, then the whole craft will technically suddenly be in atmosphere. If it happens to choose the other as the main craft, then everything will suddenly be in space.

[Corona688]

The point of a skyhook isn't to haul you out of the atmosphere but to pull you up to orbital speed.  That's what it's spinning for.

It pretty much has to be spinning.  If it's not spinning, you face the task of meeting an object that's flying by at a good kilometer per second or so, which isn't 'docking' so much as 'colliding hard enough the remaining bits glow red hot'.

[Sharpy]

6 minutes ago, Corona688 said:

The point of a skyhook isn't to haul you out of the atmosphere but to pull you up to orbital speed.  That's what it's spinning for.

It pretty much has to be spinning.  If it's not spinning, you face the task of meeting an object that's flying by at a good kilometer per second or so, which isn't 'docking' so much as 'colliding hard enough the remaining bits glow red hot'.

Yes, that's the purpose of the sky hook. I just reduced the complexity to ask for that particular part of the gameplay mechanics. And as for colliding - that's what speed matching is for. The skyhook doesn't need to reach very far down nor to be very long nor to spin very fast to demonstrate the idea. Sure if it does all these things it's actually useful, but as I said, KSP won't let me create a 500km skyhook anyway.

[Corona688]

My only point is, why not just fly 2km higher and avoid docking in-atmosphere?

[Tyko]

I think I've read that there's a hard limit to the size of contructs in KSP...I think it's around 2Km...not sure how long a skyhook has to be in order to impart enough DV to make it worth while.

[Broco]

On 6.8.2016 at 3:21 AM, Corona688 said:

My only point is, why not just fly 2km higher and avoid docking in-atmosphere?

Because the whole purpose of a skyhook is to pull a payload from the upper atmosphere into orbit and having a working skyhook built in KSP would be absolutely awesome since the system is being tested in real life already.

Of course you could fly 2km higher but where would be the challenge in that?

[Corona688]

Why on Kerbin would you let the skyhook touch the atmosphere?  What possible point?  It's not like there's a lot of delta-v involved in going 2km higher anyway, the vast majority of delta-v is expended getting something up to orbital speed.  THAT is the skyhook's job.

Edited August 9, 2016 by Corona688

[Snark]

The point is obvious:  "to see what happens." 

The experiment that I think would be interesting:  If you can get a tall tower that's in a perfectly circular orbit, such that its CoM is out of atmosphere but its lower end dips below the 70 km limit... and then you mount ladders all along its length... would be interesting to see what happens when an EVA kerbal climbs in and out of the atmosphere while on the ladder, since an EVA kerbal is considered a separate "vessel" even when holding a ladder.

Nothing dramatic, I expect (it's not as though there's significant heating at 69.99 km) ... but at the very least, it would be amusing to see if you can make the transition happen just via ladder activity.