Spricigo

Bewing already pointed the hard facts of life using subassembles. Since there's nothing else to say, I will use the opportunity yo shameful self-promotion: https://kerbalx.com/Spricigo/Selene easy-to-use, 5seat tourist bus to Mun/Minmus orbit.

If your mining base is also the refinery you may consider using fuel cells to provide the energy. As for the ideal location for ore production. The quick answer is where you get better yield (higher ore concentration). However a closer look will tell that a initial high 'efficiency' will quickly become moot if you need to transport it vaste distances deltaV to where it will be used. So we are usually looking for low gravity celestial not far from where the fuel will be used, but for places where we will land/liftoff a lot producing the fuel locally may be the best solution.

Does kerbals in the bottom of the crew roost that never get used count? Does kerbals in the mid of mission when abandoning a save (like when update hits) count?

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.

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 .

^This. @renhanxue you talk about other people options being 'unnecessary' and without 'real advantage'. The fact is: your options are also just a preference and may be as 'unnecessary' and 'impractical' from their perspective. Simple, already have a bunch of stuff orbiting low(ish) every planet. Add a HG-5 and now it is a relay.

[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).

Answer is obvious. I can instead launch 2 satellites with HG-5s and double my surface coverage. And no, it's not difficult to find a good orbit for the HG-5 operate. e.g. In my save more than half of the relays have a single HG-5 In it.

Ritual cannibalism, they smoke their deads.

I know that NASA is more catchy, but...

That's is why I design mine to be tilted in the launchpad. Then at the appropriate velocity* I just need to change SAS to hold prograde (excerpt a few that are launched Osumi style). *easier to watch than time.

Of there is reasons to use the HG-5. In fact you described very well one use: put it in orbit so it reach the craft in the surface. You may need a stronger relay to get in contact with Kerbin, but after that there's little reason to use anything but HG-5s to fill the gaps.

Reaching Duna with only Hg-5 will take a obscene amount of antennas even at the shortest distance. So unless are you planning to have a relay with 100 antennas or so you need stronger ones. there some useful links https://wiki.kerbalspaceprogram.com/wiki/CommNet

I think I'll start to use that to distinguish craft that are something but not the usually expected kind of this something. I often build FIC spaceplanes and FIC SSTOs and not much interested in explaining they are FIC every time.

So you can imagine how I feel when I have to explain that my SSTO is don't have wings and jets, or that its not 100% recoverable, or ... well, you got the idea. The fact the first stage is a pair of Jet Boosters is just a detail you need to explain because is not what people are expecting. So, combining what regex and Gaarst already said, is a JATO TSTO Spaceplane. BTW you mention "Space Shuttles" which is not the proper term for this kind of vehicle. This catchy name comes from a particular vehicle of this kind.

Yet another issue with suggesting a 'best' TWR is the inability to cover all possibilities of how that TWR will evolve. SRBs on light craft? TWR raise superfaster. Dropped the boosters? TWR decrease instantly. Large craft with heavy payload? TWR will increase slowly. The list goes on, there is just so many variable to consider it all.

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)

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'.

Unfortunately, nothing of this solves your issue. Will you try to move some mass and drag or not?

No, the steereable fins are not a problem. They are just unecessary and ineffective (thus a problem ). One possibility. But there is a few other ways to screw a nice gravity turn, those may be happening too.

That remark always annoys me*. I know that it is correct but the solution is so simple: place the landing gear so the plane is already with the nose a bit up when landed. Really, I don't even remember when was the last time I had a plane that needed pitch to take off. *mildly, but it annoys me.

The point is: the wing is not far behind the CoM. Maybe slight behind, but in no way behind enough to compensate all the drag in the nose. Where is the geometric middle of the craft is irrelevant for aerodynamic stability. You cant/don't want to change the nervs and the main wing? Ok. How about those other engines? How about changing the fuel tanks? If nothing can be changed the 'solution' become more drastic, we need to add things, things your craft don't need and will make it heavier and draggier (IOW: things that make your craft worse. )

Yes. But it may also make things worse. Thing moving in the air want to go heavy part in front, draggy part behing. Your may force the heavy part to stay behing (reaction wheels, RCS, control surfaces) but it become more and more difficult as drag increase. You may use a cannard to try to stop the flpping, but, without adjusting other thing to make the craft more ballanced, it increase the drag in the front even more. So, use it if you want, but move the main wing further behind and some of those heave engines further ahead.

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. 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.

Not useless but redundant. Anything you can remove and still do you mission without issues should be removed. So, do you need the intake air from pre-coolers? Do you need the fuel form pre-coolers? (Even if you need, that's the best way to havevit?) For what is worth: I like how your craft looks. Not 'nice' but 'functional'.