Stock 100% recovery launchers (aside from SSTOs)

[KerikBalm]

I would like  to discuss launchers that can semi-reliably get 100% recovery of funds (that is, land at a Runway or on a luanch pad, not just somewhere on the KSC grounds) - minus fuel and payload fairing costs of course (and perhaps decoupler cost).

SSTO spaceplanes are obviously one way to do this. I have built 3 categories of such SSTOs: 1) horizontal launch and landing, 2 &3) vertical launch, horizontal landings, with or without air breathers. 

Then, I have also built 2 stage designs.

1) an air breathing horizontally launched spaceplane, that goes suborbital, decouples a 2nd stage that gets to orbit fast enough for me to switch back to the first suborbital stage and fly it back to KSC (must still have enough liquid fuel for its airbreathers). The 2nd stage also glides back to KSC after deploying its payload. This works better (or is more copetitive against pure SSTOs) on scaled up solar systems

2) Vertically launched 2 stage winged rockets, no air breathers. First stage goes up, doesn't tip over more than about 60 degrees. Decouples the payload with some dV remaining (remaining dV goes way up when the mass of the 2nd stage and payload decouple). 2nd stage continues to orbit. Before the 1st stage reaches apoapsis, it must turn retrograde. At apoapsis, essentially "reverse" the surface velocity. If surface velocity is 500 m/s going east, then about a 1000/ms burn is done to change that to 500m/s surface velocity, going west. That puts the trajectory essentially back towards KSC, where minimal glide capability can put the 1st stage over the runway where it can land horizontally, or just pop chutes. One can start orbital insertion of the 2nd stage after decouple, switch to the first for the retro burn, switch back to the orbiter to finish insertion, then switch back to the 1st stage before it goes too deep in the atmosphere. Again, this is more competitive vs SSTO designs as the system scale increases.

Between 1) and 2), 2 is faster total, but payload fraction is much worse, and timing can be more annoying because you need to swithc back to the first stage before apoapsis, and again (if orbital insertion was incomplete) before it gets deep in the atmosphere, vs just getting deep in the atmosphere for 1. Its faster though, because 1) requires flying back on airbreathers to KSC.

I have yet to find any real practical 3 stage solutions (beyond gimmick very short duration boosters that can burn for a few seconds, and parachute to the ground before leaving the physics bubble of the main craft).

 

 

Abyone out there have different ways to go about 100% reusablee/recoverable launchers?

 

 

[juanml82]

You can always try the SpaceX route and vertically land your first stage. In stock Kerbin, I use a large first stage that makes it to orbit, and then deorbits and lands with a combination of parachutes and a rocket burn. You'll need mod landing legs to avoid landing on your engines. Reaching KSC can be hit or miss, though. But the payload fraction is much bigger than spaceplanes.

[KerikBalm]

10 hours ago, juanml82 said:

You can always try the SpaceX route and vertically land your first stage.

I have tried this before

Spoiler

3x scale sytem

1st stage, getting close to KSC, but not 100% recovery:

Less than 100 tons to orbit:

orbiter coming in for recovery:

Another, smaller recoverable booster, failing 100% recovery

I suppose I could mount a part usable as a control point bacwards, and use some control fins to steer it back to the KSC runway if I get the trajectory close enough. Still, given the lack of automation tools, and the differences between KSP parts and real world parts, I find true winged boosters to be easier.

10 hours ago, juanml82 said:

Reaching KSC can be hit or miss, though.

I'm aiming to do more than reach KSC, but to land on the launch pad or runway. These locations yield 100% fund return. Landing at KSC yields only 98%.

(2% of part cost + fuel costs) can be quite a lot more than (0% of part cost + fuel cost). I am looking to reduce launch costs

10 hours ago, juanml82 said:

But the payload fraction is much bigger than spaceplanes.

I haven't found this to be true for stock KSP systems... and for scaled up systems, the spaceplanes are still massively outperforming the conventional rocket systems.

One should define spaceplanes though. In my 3x KSP system, I mainly use a suborbital spaceplane 1st stage with rapiers, that launches an underslung orbital spaceplane with a Rhino. Both land back at KSC.  It handles a 100 ton payload no problem

Spoiler

Here it is with the 2nd stage replaced with a payload meant to be a SSTO cargo shuttle for... a modifeid duna I think... (3x system)

Its also the only way I've made a reusable EVE orbiter (1x system):

I even made a reusable cargo shuttle work for eve, but I had to reduce the cargo capacity from my standard 40 tons and long mk3 cargo bay to 20 tons and a medium cargo bay:

(was just a test, the real thing would have a shielded docking port)

Works in 6.4 x scales as well:

I've also been trying to make a 2 stage vertical launch, horizontal landing system that can handle 100 tons. So far its total mass is well over twice the mass of my rapier spaceplane, and its not meeting the design goals. It is technically a spaceplane in the same way the space shuttle was. It launches like a normal rocket, but lands like a plane.

The air breathing  (or electric prop) planes definitely get better payload fractions, but need to spend more time flying back, as they don't retrobrun at apoapsis.

[reducing]

The first picture you posted works well for stock size planets. I take a smaller payload so I have some Dv to kill my speed over top of KSC and land in the complex.

With the stock engines it feels like any extra weight ends up killing the capability of the rocket.

Edited June 18, 2021 by reducing

[KerikBalm]

15 hours ago, reducing said:

The first picture you posted works well for stock size planets. 

I found, for stock size, I could just delete the second stage, and use the Ap retro-burn fuel to push to orbit instead. Make it a SSTO, and inly bother with 1 recovery.

Im open to being proven wrong, and seeing significant payload fraction improvement via the 2 stage approach.

15 hours ago, reducing said:

 have some Dv to kill my speed over top of KSC and land in the complex.

I want my 2%, ksc recovery is only 98%

15 hours ago, reducing said:

With the stock engines it feels like any extra weight ends up killing the capability of the rocket.

Yea...

 

 

[reducing]

21 hours ago, KerikBalm said:

I found, for stock size, I could just delete the second stage, and use the Ap retro-burn fuel to push to orbit instead. Make it a SSTO, and inly bother with 1 recovery.

My mistake, I thought it was an SSTO from the picture and wasn't clear on my description. I agree that dealing with 2 stages is too much work and SSTOs are nice and simple. If you want 100% you could use Vernor Engines to push your rocket on to the runway while its gliding down, I think it even works with parachutes.

Edited June 19, 2021 by reducing

[KerikBalm]

So as far as 2 stage 3x system designs for 6 full ore tank payloads (102 tons):

A horizontal launch rapier 1st stage + rhino 2nd stage got the payload to orbit with generous dV margins, below 663 ton takeoff weight.

A vertical launch cross-feeding design with 7 mammoths on the first stage and 5 vectors on the 2nd ( 4 of which fire with the first stage, running off if 1st stage fuel) got to orbit with about 35m/s to spare (went over 90 when the payload was decoupled)... Takeoff weight was over 1750 tons. Also while I was able to switch to the 1st stage, it broke apart on its steep reentry, but I think with some tweaking that I can get the entire contraption fully recoverable without adding anything, but perhaps I will increase lift off mass by up to 100 tons, to 1850 tons.

Fuel costs will go way up (expecting around 3x) but total play time per launch should go down

Edited June 20, 2021 by KerikBalm

[jimmymcgoochie]

Build a big rover-like contraption to drive out, grab your wayward boosters after they land somewhere near the KSC, carry them back to the runway/launchpad then drop them off to be recovered. Saves a lot of effort with trying to do precise landings but you still get the 100% recovery bonus, plus the rover can be parked somewhere on the KSC grounds and used repeatedly.

[KerikBalm]

3 hours ago, jimmymcgoochie said:

Build a big rover-like contraption to drive out, grab your wayward boosters after they land somewhere near the KSC, carry them back to the runway/launchpad then drop them off to be recovered. 

Well, I feel like that would become impractical as the booster size increases.

One thing I did for my spaceplane, was to put a mining rig rover on the peninsula east/north east of ksc. If for some reason I found myself low of fuel for the return, instead of doing a 180, I could turn a bit north and gas up there.

I have thought about something similar for ksc, allowing the stages to hop to a 100% recovery.

Still, I am finding 2 stage vertical launch reusable non-airbreathing craft to be rather hard (that is massive with low payload fraction) at 3x scale. 

 

[cubinator]

I had an SSTO rocket with a recoverable second stage that was pretty large. Since the booster could get to orbit most of the time, you could just point it back at the right time to land near KSC, but the descent was aided by parachute which is not entirely precise.