Spinlaunch in KSP? Yes!

[Axelord FTW]

I just saw Scott Manley's latest video on Spinlaunch and I feel like this could make for fun gameplay.
Don't have time to play KSP today but I can easily imagine this will be part of 'What I did in KSP today' soon enough. Anyone got some good ideas as for rule for a challenge? The point of Spinlaunch is to shave off as much energy possible from the total requirement for achieving orbit, so I'm thinking something along putting a particular payload (QBE probe core and four OX-STAT panels, or maybe a single kerbal?) in orbit and seeing who can do it with the least dV. Maybe make it simpler and score by craft mass? Maybe split into single and multi-stage categories?

Most players have spun up their crafts one way or another prior to stage separation to get some velocity going, and I think this is just doing the same, but bigger, and at a place most players haven't. 

EDIT: Following a comment posted under Manley's video, I've also been wondering about trying it out on the Mun, or maybe another celestial body in the Kerbol system. The Mun seems like a fun place to try things on? The return-to-Kerbin dV requirement on Minmus is low enough that I'm pretty sure it could be done entirely with Speen.

Edit: I'll clean up the header post and format it with results later. Progress is described below for now.

Edited November 12, 2021 by Axelord FTW

[AtomicTech]

Matt Lowne did something like this!

 

[Axelord FTW]

Ah, now that you say that I vaguely remember seeing this. I did a quick search on the forums but 'spinlaunch' brought back nothing. Searching for 'centrifuge' brings up a lot of spacehab related discussion.

Lowne's method is just wasteful, and required more fuel than a straight launch would have. I think this is still very much an worthwhile challenge. I'm thinking an EC-powered speen would be the righter sort of stuff.

[jimmymcgoochie]

I distinctly remember someone doing some kind of centrifuge powered launch system on Minmus, but it was a whole ago and I can’t remember who or where that was.

[Axelord FTW]

I might have done such thing back when free-moving joints were only available through mods, and there were probably gruesome, inkerbane experiments done and posted on the forums when free-moving joint first hit stock KSP. It's the sort of thing monsters like us tend to do.

Edit: So far I've got a few ideas to see how far I can push things. I'm hoping fairings can be used the same way Spinlaunch use a quasi-vacuum chamber to dramatically reduce energy loss. I'm also pretty certain I'll have to use auto and placed struts like mad. Rotation speed should be mostly limited to rpm speed of motors, but maybe you can stack them? Testing! Fun!

Edited November 11, 2021 by Axelord FTW

[Staticalliam7]

5 hours ago, AtomicTech said:

Matt Lowne did something like this!

 

Lol beat me to it!

[Axelord FTW]

I'm happy to announce Jeb only died five or six times before I got it to release even vaguely upward.
 

Spoiler

In other words, Spinlaunch in KSP work!
I'll work on it some more.

[splashboom]

11 hours ago, Axelord FTW said:

In other words, Spinlaunch in KSP work!
I'll work on it some more.

That definitely means it works IRL!

Seriously, apart from the release shock its such an elegant idea ..

[Axelord FTW]

I've made a two-stage delivery rocket that can put a very small satellite in a 71km orbit consistently with 20m/s of dV left if it follows a very precise ascent path (MJ was used for this).
Don't have enough time to really experiment but I actually managed to speenlaunch the damn thing in a retrograde orbit, but it was short of 5m/s at the end to truly get it in a stable orbit. It would eventually decay if kept loaded. For a whole rocket and payload with a cost less than 4000, that's good. More testing and results soo.

The high speed at release means control surfaces can't correct the missile's path so I gotta get it perfect, which is a pain. Wish I could think of a way to get consistent separation.

Edit: Guess I'll give Better Time Control a spin. The slow motion tool should help greatly. Next is also trying to add more motors to combat drag. Two big motors could get me about 300m/s at release, from 170 rpm. The loss to drag is also a problem, since the rocket, and especially the final payload stage are so light. I'll also start experimenting with heavier crafts this weekend.

Edited November 11, 2021 by Axelord FTW

[Fraktal]

Stratzenblitz75 already beat you guys to it two and a half years ago. 

Albeit his take was an aerial spinlaunch.

Edited November 11, 2021 by Fraktal

[Axelord FTW]

Comparing anyone's effort to Stratz is kind of a dirt move, brah.

From what I can see on the BTC page, I think I'll be able to achieve consistent launches AND get a higher RPM from the speen machine. One problem I'm facing with higher RPM is the leftover spin on the craft at the moment of release (like Stratz's second spin impulse on his craft for the final orbit). One option is to offset the missile along the arc on the arm, thus offsetting the spin since it is no longer held vis-à-vis the CoM. Again, testing required.

If I can get the RPM over 200, the dV requirement will start dropping significantly. More motors, downsizing back to allow the use of a giant fairing chamber again, and BTC are on the menu next.

Edit: Well, the bad news is that BTC doesn't actually do anything about the speen machine spaghettifying under load. KPS will stretch apart connection under enough force, which makes balancing the apparatus impossible. One side will stretch more than the other, even if they are identical (because any wobble gets accentuated, and any shift is also shifting the CoM from the rotation axis). The motors will top out in RPM when they gain equilibrium with all that energy being lost. Did some more testing with fairings and they absolutely work so there's light on that side of the tunnel. Only way I can imagine to mitigate joint stretching would be to mod in a new, single part that serves as the payload arm and counterweight at once. BTC does allow for more precise release so it's quite obvious I'm saving a 'lot' of dV if my goal is to put a 700kg craft in orbit.

Edited November 12, 2021 by Axelord FTW

[Rocket Witch]

On 11/10/2021 at 11:05 PM, jimmymcgoochie said:

I distinctly remember someone doing some kind of centrifuge powered launch system on Minmus, but it was a whole ago and I can’t remember who or where that was.

Not centrifugal but possibly what you remember or at least related: Nikola Wiche jumped a car from Minmus to Kerbin.

[Axelord FTW]

Well the good news is that Stratz is currently streaming 'Sending a spin-launcher to Minmus' so things are about to get wack!