Wanderfound

Plan on several thousand ΔV for the capture burn, and moderate gravity during landing. Not too bumpy a surface, though. A Kerballed mission to Moho is Serious Business; second only to Eve for challenge. Good luck.

Twenty Kerbals to Minmus surface and back, with a Munar fly-by on the way: Expense is 11,049LF (√8,839) plus 9,104O (√1,639) and 32MP (√39). All up, √10,517, for a ticket price of √526/kerbal.

Dry Panther will extend a glide, but it's not quite enough for sustained flight in stock aero. For a real Laythe cruiser, you want a seaplane. That's surprisingly easy to do once you've got the knack.

* Hinges, bearings. Both for tiltwing/tiltmotor VTOLs, and also to allow fold-out spacecraft designs * 0.625m SRBs * Shielded 0.625m docking ports * Mk2 inline air intake * Mk1 cargo bay * Steerable large nosewheels * Some more options in the Mk3 wings

This 'un is disqualified from this challenge due to the use of Mechjeb, but to demonstrate some possibilities:

If fast is as important as efficiency: tried a three-RAPIER version?

Nukes make a landing & return much easier, but it isn't hard to manage a Mun/Minmus/Duna orbital sightseeing tour on pure LFO. Shave the passenger capacity down a smidge (i.e. replace one passenger cabin with another short Mk3 LFO tank) and a Mun/Minmus landing is doable; cut the passengers down to a minimum and it'd handle Duna as well.

Not sure if I'll have time to race, but an old bike for inspiration: Four wheels for symmetry, but opposed and translated into each other to appear and function as two. Handles like a real bike; lean angle to turn, countersteering to hold the angle. RCS just to pick it up again if you drop it.

Screenshots... Is that 76t with or without fuel?

You want to fire your rockets once the jets begin losing significant amounts of speed. However, you want to plan your flight so that that moment occurs just as you get to the jet altitude ceiling. How to do that varies with the craft; see Generally, I'll be using one of two flight profiles, depending upon available TWR. Low TWR: a low-angle (5° or so) constant-climb ascent, aiming to hit maximum jet speed just as I get to an altitude where the jets begin to fade (around 22km for RAPIERs), adding nukes to buffer the jets through the low-thrust 20-30km zone. RAPIERs switch mode at 29km. High TWR: up to 10km as rapidly as possible, level off and accelerate to 1,500m/s, then pull into a zoom climb to push the apoapsis over 30km. Aim to do this low enough so that the jets can regain the speed lost before reaching 20km. Keep the nose on prograde to minimise speed loss during the 20-30km zone, switch RAPIER mode at 29km. The profiles are much the same with turbojets, just a few kilometres lower and a few hundred metres slower. About 30%. That's an extreme example, though; that ship would normally fly with about half that payload (and a much more comfortable takeoff).

If you want to use a Mk2 you can, but you need to build accordingly. You want to set it up so that the potentially draggy fuselage is always pointed as close as you can get it to surface prograde. The way to achieve this is with wing incidence; angle the leading edge of the wings up a few degrees, so that the wings are at a greater AoA than the fuselage. 17km is way too low to be firing your rockets; you want to be extracting as much speed and altitude from the jets as possible. Mk2 parts have good heat tolerance; use that. Crank it up to edge-of-melting speed while flying level around 10km, then gently pull into a climb to push your apoapsis above the jet ceiling. The more gentle the pull-up, the less speed lost; also, the lower you start the climb, the more time your jets have to recover the speed lost in the beginning.

Craft file at https://www.dropbox.com/s/mkniu3tnpnzd9qc/Kerbodyne Pathfinder.craft?dl=0

Craft file at https://www.dropbox.com/s/mkniu3tnpnzd9qc/Kerbodyne Pathfinder.craft?dl=0

Just to demonstrate that fast ships don't require many engines:

How much are you planning to lift? If it's just passengers, a single RAPIER is adequate and two should make a very quick hotrod. For cargo, you'd be after a minimum of roughly one RAPIER per ten tons of payload. For LKO, stick to pure RAPIER power. Add nukes if you're going interplanetary; darts only really become useful on Eve ascents or if you've got some other reason to want to avoid nukes.

Standard low-drag heat-protected stash spot for batteries, SAS units, probe cores, science gear, RCS tanks and solar panels on landers and Mk1 spaceplanes.

From a strict efficiency POV, yeah. OTOH, there's more to life than efficiency. Given an orbital refuelling depot, that last model of the Minmus Panther I posted could easily clean out every biome on the Mun or Minmus in a single trip, and would work well for Duna and Laythe too. But you could probably achieve the same goals a smidge cheaper if you instead used a cargo SSTO to haul a dedicated space vessel into orbit and bring it back down again (although the size restrictions of Mk2 cargo bays add some complication to that). Taking your wings to Eeloo and back is fun, but all it gets you is style points.

Another option: https://www.dropbox.com/s/eqreh7jzae53mln/Minmus Panther D.craft?dl=0

https://www.dropbox.com/s/eqreh7jzae53mln/Minmus Panther D.craft?dl=0

https://www.dropbox.com/s/eqreh7jzae53mln/Minmus Panther D.craft?dl=0

As ordered: 16 kerbals, one lab, 750 monoprop, 13500 LF, 16500 O, capacity for 3000 ore, one lab, one klaw-tug. Part count at launch is 77, for 123 points. Another 16 for passenger capacity, 37.5 for fuel, 30 for ore, 10 for the refinery, 10 for the tug, plus one each of Sci Jr, Goo Pod, Barometer, Thermometer and Gravioli Detector in the service bay for another 10. No rearrangement for 10, link below for 100. Craft file at https://www.dropbox.com/s/tz4zvdyiuzrey82/Stationish.craft?dl=0 All up, 346.5 if I've figured it right.

Suggestion: if you want this to be a contest of proper aircraft, ban SAS units and cockpit torque, maybe lock engine gimbal as well; require that aircraft are controlled through aerodynamic forces. Otherwise, based on past experience, it's going to be dominated by near-identical minimalist jet bullets with no control surfaces and virtually no wings. EDIT: actually, on current rules, it's going to be rocket bullets. Limiting factor there is thermal; you may want to ban internal heatshields. Eh? Infinite fuel, zero gravity and no heating effects...

Another one: 52 Kerbals to the Mun and back at √158/head √158

Big 'un on just two pair of flat hydrofoils (both activated as flaps when in the water): The floats on that are just to keep the engines above the water while stationary; largely cosmetic. They barely touch the water at speed. A planing hull on a little 'un: The floats on that one are for landing stability; again, not strictly necessary. Similar ship on a single pair of hydrofoils: It usually requires about 30m/s of waterspeed to get up onto the foils or planing hull, but if you can do that it requires very little in the way of foil to lift even a large ship out of the water. Fine tuning of position and deflection angle is required, though. At least one pair of foils under CoM; if you've got a second set, stick 'em as far forwards as is convenient. Tweak the deflection settings so as to trim the craft level while moving over the water. Required settings may change with speed, particularly the balance between front and rear. I have some planes where, for best performance during acceleration, you want to deploy front foils only at first, then both front and rear foils, then rear foils only. I've also had good results come from keeping the front foils active as pitch control surfaces; smooths out the pitch trim in the water, and useful in the air as well. Once you're up onto foils, the only real restriction on your top speed is how long you can keep it stable and prevent it from spontaneously taking to the air. Tweaking foil deflection settings just right can often turn an unstable hydrofoil into a smooth one.

Very possible. As mentioned, though, we need pictures to diagnose issues.