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Commissioner Tadpole

Trouble with designing a 95% reusable VTOL SSTO Laythe Lander

Question

I've been planning to establish a long-term colonization on Laythe for a while now, considering so far the only non-Kerbin planet I ever sent Kerbals to was Duna, with a very lackluster base. Because of it being long-term, I plan to have a space station orbiting Laythe with two landers on standby, which must be almost completely reusable and be able to ferry at minimum six Kerbals from the station to the base(s), with maximum efficiency. With those restrictions in mind, and considering that I plan to keep the space station at an altitude of 150-175km(to make the rendezvous easier for me), I managed to design a hefty lander packing 3.8 m/s of dV, space for seven Kerbals, and a jumbo docking port on the bottom, which also counts on being refueled when landing on Laythe by virtue of the base(s) being equipped with fuel refineries and rovers able to ferry the fuel:

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As you can see, the reason for the unusual placement of the docking port(below instead of on top) is in favour of a RealChute parachute, designed to work flawlessy(mostly) on Laythe - which is why the lander is not completely coated in 'chutes. Unfortunately, RealChute has a hardcoded limit of 10 uses per parachute part, after which it will no longer work; as it will have to be replaced by a new parachute part through KIS, this is why the lander is only 95% reusable - and not using parachutes at all is a terrible idea as the lander completely loses control when entering Laythe's atmosphere - being the very first craft I've seen that prefers to fly face-first when I intend it to fly butt-first, while it's normally the other way around. (Re-entry heating is disabled in my save file because I have barely mastered proper drag-friendly crafts, let alone drag-friendly heat-freindly crafts)

Nevertheless, using HyperEdit, I did multiple simulation flights with Laythe and, despite those shortcomings, de-orbiting and landing in Laythe is something the lander can do(with some trouble regarding loss of control; it can end up flying sideways and therefore gliding far away from its intended destination). The true problem is taking off again and reaching orbit: It just doesn't have enough fuel. Sure, it can attain an apoapsis that's above the atmosphere(thanks to a planet pack, the atmo height is raised to 66km instead of 50km; pressure and grav are unchanged), but it will be left with just 900-800m/s of dV left, when over 1100m/s are needed to complete the circularization. And this is without accounting the fact that the lander would still need to rendezvous with the soon-to-be space station at 150-175km of altitude...

Either the lander is fuel-inefficient, or I am doing a wrong ascent profile. And I did check a guide for ascent profiles, but when I tried that, it just resulted in the lander deciding to fly into the ground. (Considering that guide was aimed toward large Kerbin crafts, it's possible its advice just doesn't apply for this situation) Thus, I'm wondering if anyone is able to help me with either/both problems. I'm looking to try and optimize its fuel consumption as much as I can(the aerospikes are the most efficient engines available: the Terrier is too weak, and everything else is either too powerful/inefficient, or has a mismatching size) to be useful in case of an emergency, and find out a more efficient way to get the lander up into Laythe orbit. As well as possibly find out what's causing the lander to completely lose control when braking into Laythe, as that will definitely end up causing problems later on regarding landing precision and the time spent ferrying Kerbals and fuel.

And yes, the Center of Mass is above the Center of Lift, which is above the Center of Thrust. And here is the lander's .craft file, in case you need it or just want it.

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I can't help much with the rocket side of things as I'm the sort of person that'd do that with an aircraft,  but i would say the Apollo Command module style mk2 capsule is a very heavy part, and the margins on rocket SSTOs are razor thin.   So, you could get weight down a lot if you could bring yourself to use probe cores / lighter crew modules.

 

eg.  put mk1 crew cabins on half the aerospike nacelles  ( 6 kerbals)  then use a mk2 lander can on the bottom of the main 2.5m stack, so they have a hatch to get in and out of .

That's a total weight of 5.5 tons for 8 kerbals instead of the 6.5 tons for 7 you have now.

Or 

three mk1 crew cabins, and a mk1 lander can at top of main stack 3.6 tons for 7 kerbals

Ship won't look as nice though

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For the atmospheric entry, your rocket is doing exactly what it's supposed to. It doesn't care whether it is entering Laythe or leaving it, the heavy end (command pod) goes first, and the draggy end (with the winglets) brings up the rear. For entry on atmospheric worlds, I combat this problem with drogue chutes. They can open at higher speeds than standard chutes, so it won't matter that you're coming in nose-first. As for the heat, you should be able to turn it back on. As long as you don't try to enter in a steep dive to the surface, you shouldn't have a problem with over-heating. I don't use shields on Laythe and I've never run into a problem. I wouldn't say the docking port is in a strange spot, because that's exactly where I always put my docking ports (and sometimes a standard size on the nose, as well). I feel it allows for much more versatility. In fact, aside from the modded stuff, it looks exactly like one of my own ships. As for a launch from Laythe, I usually takeoff Eve-style. That is, launch almost straight up to get out of the atmosphere as quickly as possible; then coast into the vacuum, turn and burn for orbit. Comparatively, Laythe's atmosphere seems to be thicker higher up than Kerbin's is. I feel like I lose more to drag than I gain with a gravity turn, so I just head straight up. I usually 2-stage it, though. I don't think I ever tried a single stage before. I'd have to look back through some older ships to see.

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The keys with any SSTO, whether rocket or plane, are to reduce mass and drag. Your laythe TWR is 1.81. That is very high, and suggests that you have too many engines. Thus, too many nacelles. Drop from 6 to 4. Or, conceivably, drop to 3 and use Reliants instead of the aerospikes.

Put your Hitchhiker at the bottom, so you don't need the ladders and can get rid of them. Drop from 4 RCS retrothrusters to 2 or 0. Swap the 4K battery for a 1K. Get rid of all the landing legs, and land on your engines.

Swap the 6 solar panels for 2, attached to the core stack. Move them to the bottom, so the drag from them will add to stability in flight, rather than detracting from it.

And as AeroGav said, swap the MK1-2 pod for an  MK1 inline + MK1 crew cabin + 2.5 to 1.5 adapter.

Then, if you can, add another -8 fuel tank to the center stack, I'd say.

 

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3 hours ago, AeroGav said:

 So, you could get weight down a lot if you could bring yourself to use probe cores / lighter crew modules.

It certainly don't hurt, but that seems to not be the issue there.

I build a similar craft and tested it in Kerbin. The main differences are: 1.8t lighter, no fins, Lander can at the bottom, 3xcrew cabin inside a 2,5m fairing (not staged), RCS tank, probecore(okto2) and batteries inside the fairing, 8 unidirectional RCS thrusters for translation only.

Spoiler

uGNN6T8.png

pTy0o6v.png

warX5pA.png

 

Launched it (2degree tilt at the launch pad, full throttle, SAS on {craft in aerodynamic unstable, but has a big reaction wheel to keep it pointed where it should}, at 90m/s SAS to prograde), reached a nice 150km x 150km orbit, said hello to my imaginary station and de-orbited. Re-entered pointing retrograde (aerodynamic stable in that position), coming from 150km(pe 9km) I see a lot of heat bars but nothing went over 75% critical temperature, besides the parachute a small 'suicide burn' was necessary to not touchdown too fast.

I didn't test in Laythe  (honestly, too much trouble just to give advice to someone else) but I don't see reason to believe that it wouldn't be able to do the job there. And, given that Tadpole's craft seem to have similar TWR, deltaV and drag profile, I also expect it to be able to do the job. So, while there is room for improving the design, more probably it's a piloting issue.

 

Now, to lift off from  a body with atmosphere you probably want to do a gravity turn. You know it: a small initial inclination and then follow prograde until you get in orbit. The questions are how much tilt and when start the turn. Simple questions, except that 1° or 1s can make a big difference. It depends on the celestial body, but also on the craft, so you need to experiment  to find the 'ideal' trajectory for  your craft. A steeper trajectory will suffer more gravity losses(more time to reach orbital velocity), a shallower trajectory will suffer more drag losses (more time in atmosphere).

BTW: get rid of those steerable fins.At the time you need, it don't work. (that is when you will start the gravity turn, at this point you are at low speed, so low aerodynamic force which is what fins use to steer your craft.)  At the time it work, you don't need. (after initiating the turn you want to stay pointed to prograde to minimize drag and cosine losses, the last thing you need is a deployed fin steering you in a different direction).  If aerodynamic stability become a issue without it, use fixed winglets(/wing parts) that have better lift/mass.

In any case,  like others pointed, drag and mass reduction are key factors. pay attention for the opportunities to do so.

 

 

 

 

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@Commissioner Tadpole: Figured I'd see if I could make it work with the Mk1-2 that you're using (which happens to be my favorite command module). This thing's ugly but, believe it or not, it actually works. It doesn't need fins to keep it stable. The body itself is draggy enough. And the Vectors are insanely powerful. There's not a lot of room for error (and it doesn't have RCS for docking), but it got me into a stable 75km x 75km orbit.

 

screenshot557.png

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3 hours ago, Spricigo said:

BTW: get rid of those steerable fins.At the time you need, it don't work. (that is when you will start the gravity turn, at this point you are at low speed, so low aerodynamic force which is what fins use to steer your craft.)  At the time it work, you don't need. (after initiating the turn you want to stay pointed to prograde to minimize drag and cosine losses, the last thing you need is a deployed fin steering you in a different direction).  If aerodynamic stability become a issue without it, use fixed winglets(/wing parts) that have better lift/mass.

I really doubt steerable fins are the problem.    IF you are that worried about drag, he should probably take a hard look at the fuel ducts and the solar panels not in service bays.

As you can see here, one solar panel produces 40% of the drag of a Big S wing.    

nmeKQWx.png

I suspect the issue is more to do with either the lardiness of the crew accommodation or his launch profile.   Sounds like he's trying too hard to avoid drag.   Mach 1 below 5km would be bad, but otherwise he should be accelerating horizontally soon after launch and not waiting till "out of the atmosphere".    The closer you are to orbital velocity the  less gravity pulls you back down, so you really want some horizontal speed on from 10km upwards.

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No, the steereable fins are not a problem. They are just unecessary and ineffective (thus a problem :P).

24 minutes ago, AeroGav said:

  Sounds like he's trying too hard to avoid drag.   Mach 1 below 5km would be bad, but otherwise he should be accelerating horizontally soon after launch and not waiting till "out of the atmosphere".    The closer you are to orbital velocity the  less gravity pulls you back down, so you really want some horizontal speed on from 10km upwards.

One possibility. But there is a few other ways to screw a nice gravity turn, those may be happening too.

 

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I think you're approaching this a little wrong.   Your stated goal is:

two landers on standby, which must be almost completely reusable and be able to ferry at minimum six Kerbals from the station to the base(s), with maximum efficiency. 

Ok, so why not make them (SSTO) planes?  I'm currently doing an MKS base for Laythe and every vessel I'm using is a plane - and I have around a dozen of various different designs.  Any SSTO plane that you build for Kerbin will also work for Laythe - with the caveat that the plane must be able to land safely at around 3000m on Kerbin - roughly the same air pressure of Laythe at sea level.  You can even add parachutes if your landing skills aren't brilliant - and as long as you're using Medium landing gear or below it'll be steerable and driveable on the ground so you can park up next to your base.  You'll also probably find that the eventual 6-man craft is lighter than the vessel pictured - as it's going to use an air-breathing engine for most of the ascent, it needs significantly less fuel.

That said, I know that SSTO planes are somewhat tricky to build, and attaching a jumbo docking port to one will make it a lot less aerodynamic - I have done this successfully in the past, but for my current Laythe mission all the SSTO planes have shielded docking ports rather than the Jumbo one.

 

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44 minutes ago, bigcalm said:

I think you're approaching this a little wrong.   Your stated goal is:

two landers on standby, which must be almost completely reusable and be able to ferry at minimum six Kerbals from the station to the base(s), with maximum efficiency. 

Ok, so why not make them (SSTO) planes?  I'm currently doing an MKS base for Laythe and every vessel I'm using is a plane - and I have around a dozen of various different designs.  Any SSTO plane that you build for Kerbin will also work for Laythe - with the caveat that the plane must be able to land safely at around 3000m on Kerbin - roughly the same air pressure of Laythe at sea level.  You can even add parachutes if your landing skills aren't brilliant - and as long as you're using Medium landing gear or below it'll be steerable and driveable on the ground so you can park up next to your base.  You'll also probably find that the eventual 6-man craft is lighter than the vessel pictured - as it's going to use an air-breathing engine for most of the ascent, it needs significantly less fuel.

That said, I know that SSTO planes are somewhat tricky to build, and attaching a jumbo docking port to one will make it a lot less aerodynamic - I have done this successfully in the past, but for my current Laythe mission all the SSTO planes have shielded docking ports rather than the Jumbo one.

 

Before everyone else jumps on you,  I'll point out as a Spaceplane fanatic myself, not everyone wants to play that way.   In career games you need to invest in unlocking tech nodes a rocket only player wouldn't have bothered with , as well as upgrading the runway/sph with precious funds.   I'm not much good with docking and have no experience assembling large interplanetary ships and stations in orbit,    so I wouldn't use the OPs approach if I just wanted to get in the Jool system as quickly and surely as possible.   But the OP might have no interest in/no experience in building high efficiency aircraft in KSP,  so for them it's easier to just persist with the rocket SSTO approach.      Who cares if you or I could build him a lighter airplane that does the job,   he can always throw moar boosters on the launch from Kerbin.

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38 minutes ago, AeroGav said:

 But the OP might have no interest in/no experience in building high efficiency aircraft in KSP,  so for them it's easier to just persist with the rocket SSTO approach.

Or he may even have some experience with/interest in aircraft but just happens that for this mission he want a rocket. Not everything is about 'efficiency'.

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I wonder how Rapiers would perform in a rocket-style craft on Laythe.   They're not great for this role on Kerbin because they don't really get going fast enough before the air thins out too much.   But on Laythe, the lower gravity, lower orbital velocity and  higher usable atmosphere might address those problems.    They are fantastic on Laythe planes, so might be usable on a rocket.   Though you might need to start in rocket mode for a few seconds before they get up to speed. 

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Yeah apologies - perhaps the OP wants to use a rocket as you say.  Certainly there was a time in KSP when I would find an interplanetary gravitational assist maneuver easier than building a simple plane that could take off and then land again, let alone an SSTO, so I realise that these things are not easy at all - and yes, it does require unlocking of a bunch of extra tech tree nodes.  In addition, assuming you want it to start fully fuelled in orbit of Laythe, launching planes on top of a rocket from Kerbin is always a pig of a job.  I'll dig out a pic of my six man Laythe SSTO plane and post it here as it's relatively simple.

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A spaceplane is actually the first thing I thought of as well. Just because I don't like them doesn't mean I don't respect their capabilities. I despise the Nerv, but I know that it's a superior long-range engine

In this case, a spaceplane really would be superior (I've seen how well they operate on Laythe) but, for all the reasons already mentioned, I assumed the OP just didn't want one.

9 hours ago, AeroGav said:

 

I suspect the issue is more to do with either the lardiness of the crew accommodation or his launch profile.   Sounds like he's trying too hard to avoid drag.   Mach 1 below 5km would be bad, but otherwise he should be accelerating horizontally soon after launch and not waiting till "out of the atmosphere".    The closer you are to orbital velocity the  less gravity pulls you back down, so you really want some horizontal speed on from 10km upwards.

A solid approach, but rockets don't always fly as well as spaceplanes (at least mine don't, anyway :)). My designs are never going to win any "aerodynamic" prizes but, when launching from Kerbin, I do try to keep a standard launch profile of getting horizontal. However, landers for Duna and Laythe are usually not optimized for the atmosphere (not that it matters much on Duna), so I generally just try to get out as quick as possible. If you see the big, clunky thing I put in my last post, it makes orbit as long as I launch at about 70 degrees (which is what it wants to do on its own; I don't really try to steer it). Then coast into space and circularize. If I try to go horizontal, it does not go well. Mainly, I guess, because it's not meant to. I was trying to keep the same body that the OP used (Mk1-2, which I love; Hitchhiker storage facility, which I never use unless I have to). I stripped off the winglets, but kept the ladders and solar panels (I didn't wanna add a service module cuz the thing is already huge) and used the smaller battery. I dumped the Rapiers (which is what I normally use on Laythe, but I don't SSTO, so they get staged; which makes things easier), and went with the all-powerful Vector instead. I know there are those who despise them for being OP but, if you want to get something big and clunky off an atmospheric world, they're often your best bet. So, the thing turned out ugly as all hell, but it works just fine and is reusable. I'm not suggesting the OP use such a thing (it was thrown together in about 5 minutes last night), just showing him that his design will work just fine if he's willing to make a few changes to it.

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2 hours ago, Cpt Kerbalkrunch said:

 If I try to go horizontal, it does not go well.

To be fair you shouldn't go that much horizontal. Without lift, is thrust that provide the upward momentum to get you out of the atmosphere. OTOH , given Laythe's atmosphere characteristics,  make sense to 'go horizontal' at a bit higher altitude. (e.g lets suppose at Kerbin you are at 45° at 10km, the same craft at Laythe will reach that inclination at 15km and pitch down more after that)

 

 

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I'm sorry for the late response, but: Yes, I did think of spaceplanes; I didn't choose them because I'm not exactly stellar in flying and designing spaceplanes, or planes at all. :P

However, when analyzing the situation more closely, I do think that a spaceplane carrier would be more efficient than a rocket-lander, considering its higher fuel efficiency and precision. I just hope it won't be too extraordinarily hard to pilot(and perform rendezvous with the station)

Edited by Commissioner Tadpole

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1 hour ago, Commissioner Tadpole said:

I'm sorry for the late response, but: Yes, I did think of spaceplanes; I didn't choose them because I'm not exactly stellar in flying and designing spaceplanes, or planes at all. :P

However, when analyzing the situation more closely, I do think that a spaceplane carrier would be more efficient than a rocket-lander, considering its higher fuel efficiency and precision. I just hope it won't be too extraordinarily hard to pilot(and perform rendezvous with the station)

The hardest bit is undoubtedly making something ground dock reliably with your surface base.   Even with your original capsule design i don't think that's going to happen and if you did manage,  it'd be like poking the Kraken with a stick every time you switch to the base.

A spaceplane would have a lot more fuel margin than a rocket SSTO so it would be much easier to just put a small drill and converter on the plane,  and forget about ground docking, park next to the base while the plane refuels and let the kerbals walk over.

Docking to the orbital station is the next thing i'd worry about.    Even the shielded docking port adds a lot of drag, inline docking adapters are best for efficiency but is that going to make it impossible to dock the station?   It's trivial to stick extra reaction wheels on a spaceplane (very little drag penalty),  vernor ports for translating do add more drag and are best hidden in a service bay if possible.

What does your tech tree look like? 

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[Docking at surface]

Looking to the original design I instantly imagine a low rover that go bellow the rocket to dock (then refuel and reposition it) . I found it to be an excellent solution for all ground docking needs. (Also the rover can double as a 'forklift' that move StuffTM around)

Now , for a plane It's kinda tricky to accommodate a underbelly senior docking port. Exposed it adds drag,  it don't fit inside a Mk2 cargo bay and Mk3 seems to be excessive for the task at hand. Still doable, but I'd go with a MK2 Clamp-O-Tron if that is an acceptable option.

[Docking at space]

For me that is easy, you need matching docking ports positioned in such way that the other parts of your station and craft don't collide.; a good RCS (/Vernor) system that don't induce (too much) rotation; some reaction wheels. The possible lack of docking skill need to be solved with docking practice (I know, sound like a catch-22, but its not).

 

 

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I use a mod(KAS) that adds fuel hoses, trivializing the refuel process. You can see the hose part attached to the z4k battery in the side-view of my lander prototype.

I play on Sandbox, so the tech tree is maxed out.

The docking port does not need to be a Senior; the space station is not even designed yet. :P I made it a Senior port so I could attach it directly to the bottom of the lander without having to make adapters.

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1 hour ago, Commissioner Tadpole said:

I use a mod(KAS) that adds fuel hoses, trivializing the refuel process. You can see the hose part attached to the z4k battery in the side-view of my lander prototype.

I play on Sandbox, so the tech tree is maxed out.

The docking port does not need to be a Senior; the space station is not even designed yet. :P I made it a Senior port so I could attach it directly to the bottom of the lander without having to make adapters.

KAS will make life so much easier.    I already have a plane that could do this job on KerbalX, though it is overkill for your needs -

https://kerbalx.com/AeroGav/MK1-Griffon-Deep-Space-Crew-Shuttle

IvW69G8.png

It has an inline clamp o tron and reaction wheels but no RCS system,  so rather than try adding one it'd just be easier to stick on a KAS fuel filler cap and get hosed.

37 tons, 11 seats.  3000dv after reaching kerbin orbit so it can basically do the transfer to laythe itself after taking on a little more fuel in orbit.   Low stalling speed.  Nuke engines.

Instructions - fly with SAS on and set to Prograde hold when shooting for orbit, this gives lowest drag.     Only use manual control to correct heading.   

Action group 1 deploys trim flaps in a nose up position - this raises the nose slightly.  Action group 2 sets neutral trim.  Action group 3 sets nose down trim.   

Action Group 4 toggles nukes on and off.   Remember you can get a burst from them to help you through the sound barrier if you think you need it.   Action group 6 toggles economy mode (RAPIER off, afterburner off) for cruising at low speed.

 Use the action groups to manage climb rate at low altitude and to level off for penetrating sound barrier and the speed run.     Climb to 5 or 10km before trying to go supersonic  for best delta V.     For optimum delta V,  try to level off around 20-21km and get at least 1400 m/s out of the air breathing engines before starting the nukes - on Laythe this "Speedrun altitude" might be 5km or so higher but TBH on Laythe you'll have so much excess delta V it doesn't really matter.  Once you are on nuke power for the final run to orbit,  just stay on PRograde hold and keep the trim set to neutral (Action group 2) though you can press 1 if you really think you're overheating (it won't).   When the Navball switches to Orbit mode, toggle it back to Surface mode or you'll fly slightly nose-down through the upper atmosphere.

 

Be aware I've found the trim flaps can be buggy when importing craft files, sometimes they move in the wrong way - if this proves to be the case,  toggle the deploy direction on the outer canards and elevators to get desired behaviour.

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2 hours ago, Commissioner Tadpole said:

I use a mod(KAS) that adds fuel hoses, trivializing the refuel process. 

If you really want to make it trivial use EVA resource transfer. Two advantages:

1.You don't need to dock, the crafts remain separated the whole time. 

2. A nice UI to tranfer resources between crafts without dealing with individuals tanks .

 

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7 hours ago, Commissioner Tadpole said:

I use a mod(KAS) that adds fuel hoses, trivializing the refuel process. You can see the hose part attached to the z4k battery in the side-view of my lander prototype.

I play on Sandbox, so the tech tree is maxed out.

The docking port does not need to be a Senior; the space station is not even designed yet. :P I made it a Senior port so I could attach it directly to the bottom of the lander without having to make adapters.

Your problem has piqued my interest a bit; I think because (even including my Jool 5) I've only landed and returned from Laythe maybe 4 or 5 times. I'm not a spaceplane guy, so I don't go there as often as I probably should. Wanted to take another look at this, so I threw another rocket together. And I know you said you don't need a Docking Port Sr, but I was messing around with a design that would carry 7 Kerbals like the ship in your OP, and came up with this. Sadly, I had to dump the Mk1-2 (which pained me), but I kept the Sr Port. I like them for their stability when docked, and their ease of use when docking. This does not need to refuel on the surface. With aerobraking and parachutes, it doesn't need much fuel to deorbit and land. I actually landed in the water and, once the ship stabilized, I was still able to make it back to orbit (and in a retrograde orbit, at that: not purposeful, of course; when it left the water, it was already turned toward the West, so I just let it do what it wanted instead of fighting it). It has a mix of retractable and stationary ladders for Kerbals (on each side for symmetry). A bit of a crazy design, but I kinda like it. I'm using something similar for a challenge; which is what made me think of it.

 

screenshot2.png

 

It has RCS ports for docking and, inside the service module, a battery, a monopropellant canister, and 2 solar panels. I have the doors and panels set to action groups for ease of use when the batteries need to recharge.

 

screenshot3.png

 

As far as efficiency goes, a rocket still won't be able to match a good spaceplane on Laythe. I just wanted to show that, like everything else in this game, there are multiple ways of going about solving the same problem.

 

Not sure if you can tell from the pic, but those are Dart engines.

 

Edited by Cpt Kerbalkrunch

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1 hour ago, Cpt Kerbalkrunch said:

 

 

OMG,  ladders !     That's another unexpected problem you get clobbered with.    Never really have to bother on spaceplanes, since they orient horizontal and sit low on the ground when you retract the gear,  but my Tylo lander rocket failed here.  It was a 2.5m design but no matter what, the Kerbal would fall off when they reached the seam between the lander can and the habitat module.

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6 hours ago, AeroGav said:

OMG,  ladders !     That's another unexpected problem you get clobbered with.    Never really have to bother on spaceplanes, since they orient horizontal and sit low on the ground when you retract the gear,  but my Tylo lander rocket failed here.  It was a 2.5m design but no matter what, the Kerbal would fall off when they reached the seam between the lander can and the habitat module.

It's definitely a problem. I only use them on Tylo, Laythe, and Eve so I don't have to deal with them unless I absolutely have to. I always run into the same problem you described. Specifically, getting the ladders right when the fuselage changes diameter. I'll test it on Kerbin, and it works fine, but when I land, my Kerbal either can't get down or can't back up. I end up having to go back to the VAB to move the ladders a bit. It can be irritating.

I still think the OP is better off with a spaceplane in this instance. It's tough to compete with their abilities on Laythe. Especially when you're talking about reusability and efficiency. Not to mention that it's quite a bit easier to choose your landing zone.

However, I'm a stubborn rocket guy. Even if it's more difficult and doesn't make any sense, I'll still find a way to make it work. Eventually, I'll start messing around with spaceplanes. Until then, they are strange, alien craft to be viewed with suspicion. :)

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3 hours ago, Cpt Kerbalkrunch said:

I still think the OP is better off with a spaceplane in this instance. It's tough to compete with their abilities on Laythe. Especially when you're talking about reusability and efficiency. Not to mention that it's quite a bit easier to choose your landing zone.

It all depends on how much importance is given for each factor. There is no question that almost reaching orbital velocity in jet power is a big advantage (and I'd not hold my breath in doing so without wings) but if you have plenty of fuel available from ISRU you may start to worry more about  time than fuel consumption. And wings are great when picking your landing spot but not necessary if every time you get 'close enough' without it.

I'm under the impression the decisive factor is coming to flying to orbit 'close enough' to ideal ascent profile. And, oddly to me, the spaceplanes seems to have the upper hand.

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