First the Zeus-1 Cruiser is launched.
Then a fuel tug with fuel.
Connected the tank and undocked the tug.
The fruit of project Oceanus is launched, the Poseidon hybrid lander. Which means this thing can be going only to one place, Laythe. 3 volunteers are also transported aboard it.
BTW I attached 3 more tanks before the lander docked with the Cruiser. Since Laythe is orbiting the largest planet which also happens to be the furthest away I needed a lot of fuel, although it turned out that I could have used one less. Due to the way the rocket equation works I was getting serious diminishing returns and that last one added barely jack to the total delta-v budget anyway.
Also I was too stubborn on insisting on having a cupola on the front. Sure the view is great, but having to detach empty tanks, swing them around with the lander and then dock back with just the lander sans the dead weight was a bit tedious and unnecessarily risky. The burn to Jool wasn't even done yet and already two tanks went dry.
After 414 days in space, including assembly, the cruiser enters Jool's system of moons. The plan was simple, save a ton of fuel by decelerating using aerobraking at laythe. First a burn was made so that a close Jool flyby would bend the trajectory right into Laythe, the innermost moon of Jool and the missions target.
434 km above the "surface" of a green gas giant, Laythe and Tylo are visible. Tylo is actually on a 4 times more distant orbit than Laythe, it's simply quite large (and in a good position)
Disappointingly enough the atmosphere starts way too low on Jool (still higher than elsewhere in KSP but not even by twice compared to the second tallest atmosphere), hopefully that gets changed in the future.
The target, Laythe, arguably one of the most popular celestial bodies in Kerbal. Also one of the hardest "land there and get back" targets the 3rd hardest IMO. Although the two harder ones, Tylo and Eve, are in a whole different league by themselves. Well and technically you can't really land on Jool or the Sun, but if you could either of those would be the hardest.
You can probably see why Laythe is so popular. It's an ocean world with probably liquid water and definitely with oxygen in the atmosphere, dotted by volcanic islands (the volcanism has yet to be added) and heated by tidal forces from Vall and Tylo which are in laplace resonance orbits relative to it (just like Io is in real life although the result is a bit more lethal). Probably sterile as fuck because a Jupiter-wannabe like Jool should be pounding it with killer radiation all the time.
I turned the ship around in preparation for Aerobraking to have the parts generating the most drag in the back, solar panels have been retracted. Otherwise the whole thing would try to violently turn around and spontaneously disassemble itself. When actual heat and heatshields get added pulling off something like this will be a lot harder.
Success! After several attempts which resulted in either the ship crashing or flying away on an escape trajectory I found the right altitude to kill about 3,5km/s of delta-v and enter an unstable orbit around Laythe. Just needed to burn adding a measly 100 or so m/s to stabilize it and thus avoid entering the atmosphere again.
The lander undocks, Poseidon-1 is away!
The reentry is not as spectacular this time around.
Parachutes slow the lander down but not enough by themselves, not when the ground is over 4km above sea level at the predicted landing site. Luckily though Laythe has oxygen so it is possible to use jet engines on it, hence the hybrid design of the lander since jets have decent thrust and are extremely efficient. This makes them perfect for climbing through the thick parts of the atmosphere.
The SPESS TRANSPORTATION CORPORATION proves once again that they can plant flasg whenever the hell they want, that's the power of capitalism at work folks! Got better at drawing flags although I made Jool look like a watermelon.
Sadly it landed away from a sandy beach and on the far side of Laythe. That means no beach shot and since Laythe is tidally locked no ominous giant green ball hanging in the sky as it isn't visible on this side of the moon.
Did get to see a partial solar eclipse caused by Vall, the second moon of Jool. Tylo is also visible in this shot.
After spending a day or so the dolts attempt get back into Laythe orbit. I had to fire the rocket engines for a moment as the ground was titled and the marginal positive TWR of the jets made the thing flip and crash before it could point itself straight up.
After the atmosphere gets too thin to supply oxygen to the jets, at an about 15 km altitude, the rocket engines ignite. This thing is single stage to orbit even on Kerbin, Laythe has 80% the gravity and pressure of it so anything that's SSTO on Kerbin should work even better on Laythe. Could build an actual spaceplane and fly it there but this thing is a bit easier to land and dock than a plane would be.
Back in orbit, docking took a while but wasn't too hard. Had a decent amount of fuel to spare, although paradoxically launching from sea level would be better as more jet fuel would get burned. Also fucked up and got flameout but managed to get back into orbit despite launching west (and not east which is better as the cruiser entered a retrograde orbit) and loosing speed before I regained control and fired the rocket engines.
After docking the remaining fuel got drained from the lander into the Cruiser's last tank. Left the lander in orbit as it is still fully reusable, future missions can launch from Kerbin just with the crew thus saving on fuel by not having to drag that dead weight all across the system.
Because the launch window for a return trip was about half of a year away I decided to raise orbit by doing gravity slingshots, so I could fast-forward time faster and save some fuel. First the cruiser used a boost from a second encounter with Laythe (after first leaving its orbit) to raise it's orbit to Vall's eventually getting an encounter with it after two dozen or so orbits. Vall is overall an icy rock and the smallest of the three bigger moons of Jool, the two smaller moons are captured asteroids on crappy distant orbits which I have yet to visit.
Vall is fairly easy to land on, although I only send one lander probe to it. Good place for mining for Kethane if you have that mod and want to colonize Jool's moons or just mine kethane for refueling.
Since it's not really that big (about the size of Kerbin's Mun or slightly bigger) the gravity slingshot is meh. Not sure if it was worth adjusting the trajectory just for it. But the view was.
The close 40km altitude Vall flyby raised the orbit to Tylo's. Getting an encounter was easy as Tylo is the biggest moon in the game and bigger than all but two or three of the planets in the game. This thing is basically Kerbin without an atmosphere, thus it is a bitch to land on as you can't save fuel by aerobraking and using parachutes. Return is fairly easier since you don't waste fuel on fighting atmospheric drag. Still needs a monster of a lander though, which you need to drag all the way across the known solar system, but at least it isn't as much of a nightmare for a return trip from the surface as Eve is.
After over 803 days in space the cruiser returns to Kerbin with still one orange tank left. Even if it went dry the thing has about 3000 m/s of delta-v in it's gray tank. Aerobraking gets it into an orbit around Kerbin killing off about 2 km/s of velocity for the price of just 200 m/s to adjust the trajectory to perform the aerobraking. Now I need to to launch a shuttle do dock with the cruiser and get the crew out of the hitchhiker hab module they spent the last year or so in and back to surface.