IronMaiden

As far as design goes, you have too many engines. 2 RAPIERs is more than enough for a plane this size. You've also got way too much oxidizer for a RAPIER/Nerv plane. A good starting point is about 10:1 liquid fuel to oxidizer. Also, angle your wings up at least a few degrees to minimize body drag and swap radial monoprop tanks for an inline one to decrease drag. As far as the ascent goes, fly at sea level til super sonic then slowly allow the nose to rise and the plane will climb. Your pitch shouldn't go much above 15°. Just to be clear, angle of attack is not the same as pitch angle. Angle of attack is how far your prograde marker is from your pitch angle, your pitch angle is how far your control point is angled up from parallel to the surface. Your angle of attack shouldn't ever be much more than a few degrees off of zero and ideally less than 0.01° from zero once past 15km or so (this requires wing incidence as explained in the design part above.) Once your plane has climbed past 10km start leveling out. You want your pitch and angle of attack to be about 0° by the time you reach 15km or so. Here you want to accelerate on air breathing mode as you very slowly climb. A good target is 1700m/s at 22km. NEVER PITCH ABOVE 5° ONCE PAST 15KM! Once you've reached mach 5 and your acceleration in airbreathing mode is starting to peter out, activate your Nerv and continue accelerating up to mach 6 (should be close to target above). Once there switch to closed cycle for the final acceleration to orbit. DO NOT PITCH UP. KEEP PITCH BELOW 5° ALL THE WAY TO ORBIT! Wait for your apoapsis to get to 70km or so (by this point your periapsis should be close to if not already above sea level). Circularize (should take less than 100m/s). If you do this right you should easily have 5000m/s+ left once in LKO, probably closer to 10,000m/s.

Hopefully this answers all of them :P

I made an SSTO a while ago literally called "5 Orange" that does exactly this.

KSP is awesome, KSP2 should be awesome too. Take all the time you need to make it right, we still have KSP.

Don't get me wrong, wing area is very important, but the Albatross's is way overkill. In my experience, a wing area of about 1m^2 per 5-6t of plane and 5° of incidence seems to be a good start. The Albatross has 1m^2 per 1t, that's 5x more than you need! That's a whole lot of unnecessary drag and mass. If you're looking for an early game SSTO, here's an example of a Juno-Terrier design that doesn't require any building upgrades.

Vastly improved weight distribution dude, well done!

What do you mean fly without any pitch? You mean that it takes off the runway without any input? That's because it has a built in pitch of 7° on the runway due to the placement of its landing gear and 4° wing incidence on top of that. So yeah, you're not going to need to pitch up when your wings already have an AoA of 11°. It still requires lots of pitch control once airborne. The easiest way to get a plane to require barely any pitch control is to put the CoL right on the CoM and use wing incidence. And by CoL I mean true center of lift, not the one in game that only acknowledges wings and control surfaces. The albatross is a poor model for an SSTO because it has way too much wing area. Yeah you can make it work, but you could make it so much better as an SSTO by using less wing and surface attachments.

Your problem here is as Jonny0than mentioned, your CoM is too far back. That's an inherent problem with putting engines on the back of your plane. It gives your cockpit way too long of a lever arm to torque your plane around and it gets even worse as you drain fuel. The problem is hidden by the fact that the game only used wings and control surfaces in the calculation of the CoL. Mk2 parts are considered wings as far CoL is concerned but they create more drag than regular wings and that's not accounted for. It is a center of "lift" after all, not a center of "pressure" which is what we're really after. The best way to accommodate for this is to put your CoM in the middle of your plane so that your fuselage is neutrally stable. Here's a little guide which goes more in depth on this issue. There is a way to help the design a bit if you absolutely must keep the engine in the back aesthetic. That is to move your main wings further back and use wing incidence to move the CoL forward at low angles of attack, and backwards at high angles of attack. Wings further forward should have higher angles of incidence and the angle should get closer to 0° as you move back. Now at low angles of attack CoL moves forward for efficient and balanced flight, but if you try to pitch up or down too much the CoL will move backwards to put a stop to runaway pitch. It is self correcting and the plane will tend towards a few degrees of prograde. This is not as efficient as having a properly balanced plane but it's not bad for hamfisting some stability on to an aesthetically pleasing but not necessarily aerodynamically pleasing design

Here's a basic introduction to the drag model. This was made a few versions ago, so the data is presented in a little different way now, but all the concepts are still true. As for differences between wings, there are none when it comes to creating lift. The only thing the game cares about is the surface area, the angle of attack and equivalent airspeed. The "basic fin" has the best area to mass ratio, but it has the heat tolerance of flash paper so is completely unusable in SSTOs. By far the best wings to use for SSTOs are the Big-S wings, as they have the same mass to area ratio that most of the wings have but can also store fuel for free, the wing strake being able to store more per mass than the delta wing. No, KSP does not model wing sweep or telescoping. It's 100% or 0%. The only way to reduce the drag on a radial part is to put it in a fairing/payload bay. I have done a few experiments in the past and there was no statistically significant difference in any of the wings' lift/drag. Area, AoA and EAS is all that goes in to the lift/drag calculation. Here's a tutorial where I explain and show how to build and fly large SSTOs. The one in the video is 180t and carries 90t to orbit but the design is very scalable and I provide all the math you need to scale it up.

This is a water landing and takeoff SSTO I made a while ago. It can SSTO on Kerbin too, so it's more than capable for Laythe. I've found the best way to do it is to use wing incidence or flaps to create a lot of low speed lift without having to pitch. I.e. your plane can be flat in the water (lowest drag) and still create a lot of lift because you have wings or control surfaces that are angled up into the airflow to create lift. The way this works is you start your engines, begin accelerating and then deploy your flaps (or have wing incidence), these create some lift and get your plane a little further out of the water. This means less drag, which means you can go faster, which means more lift, less drag, more speed, more lift, etc.. until you're out of the water. Only then do you pitch up, if you try to pitch up out of the water you're just jamming your tail down into the water and killing your speed, you need to LIFT out of the water. Once airborne I retracted the flaps for less drag so I could accelerate to orbit. This was a while ago, if I were to make something like this again I'd just use wing incidence and maybe a couple flaps.

Sounds like you're pretty close, retracting your flaps should help a ton lol. I quick thew this together based on your description. I used a couple engine nacelles as well as the circular intakes to make sure there was enough intake. They also provide more than enough liquid fuel so I swapped the mk2 liquid fuel tank for a rocket fuel tank. There's nothing in the cargo bay but based on the Δv remaining in orbit it could probably take a small (<3t) satellite to orbit. Not sure how much drag you're getting at 25km but you can see below that I'm getting about 12kN. It had no problem accelerating between ~12km and 25km.

Try going with less wing area but more incidence, up to 5°. I go with about 1m2 per 5-6t of plane. That should give you the best lift/drag during the most critical part of the flight, when the Terrier takes over. AoA should be negative at low altitude and supersonic speeds since you have excess thrust, you want to optimize the plane for the speed run and the switch to Terrier at higher altitudes. I also wouldn't fly with SAS unless you're using prograde hold, trim results in a lot smoother and therefore less draggy flight.

Oof, yeah you don't want to have that much AoA, ever lol. Use some angle of incidence, that way you can hold prograde for super low drag. You can see my AoA when I switched to the Terrier in the plane I linked above was 0.003° and never went above 0.008°, and pitch never went over 4° until nearing orbital velocity. Don't think of it in terms of giving your Terrier "enough time" to circularize, instead you should take a more shallow trajectory (never pitch over 10° once you get past 10km, preferably never more than 5°), then you just need more thrust than drag and you will go to orbit. Notice when I switched to the Terrier at mach 2 and 10km, I had 25kN of drag, less than half of my thrust. And drag continued to drop and thrust continued to rise the further I got. Down to 10kN at 20km and 4kN at 30km. Edit: I forgot about the new Terrier model. I used the old model Terrier here because the new ones are bugged and create a lot more drag. Same with the Poodle and Spark. Probably the Skipper and Mainsail too but I haven't tested those. You can access the old Terrier through the advanced menu. Wing incidence is more important though.

You can make a good SSTO with Panthers and Terriers. The Reliant wouldn't be a good idea, Panthers can get you up to at least 900m/s and 15km. At this point Terriers are near max Isp and are thrusty enough to get a well designed plane into orbit, the Reliant would just be useless, inefficient mass. Here's an example of a Juno-Terrier SSTO.

Huh, you got me then, that is really weird. I did a mission where I drug a capsule from a previous mission to many destinations, did the ol' release and catch, and got the station/base building milestone every time.