Going into Jool (and returning) | KSP

Added: 2026-05-12

[00:00:00]This is Jool, the largest planet in all of Kerbal Space [music] Program, and the only gas giant in the game.

[00:00:06]Today, we will be attempting a mission that almost nobody has ever completed before.

[00:00:11]>> [music] >> In a single launch, we are sending three Kerbals into Jool, getting them all the way to the lowest point possible, and then we're bringing them all the way back up and back home to Kerbin.

[00:00:21]And this is the rocket responsible for getting us to Jool and back. This 100-m high rocket has 45 Mastodon engines spread across five boosters to get us into orbit. The second stage has four Rhino engines and will be used to transfer to [music] and capture around Jool. And above that, we have a nuclear stage housing seven Kerbals, which will be responsible for getting the crew back home to Kerbin. And lastly, we have the lander, or rather, the Jool descent and ascent vehicle. It has one Vector sustainer engine and eight Aerospike booster engines on the first stage, and another two Aerospikes on the second stage. And of course, at the core of it all, 16 heavy-duty rotors that will handle nearly half of the ascent back out of Jool's atmosphere. We are now on the pad during a transfer window, and we have a gas giant to defeat.

[00:01:06]Let's go to Jool.

[00:01:12]>> [music] [music] [music] >> And off we go. We have lifted off the pad and are headed towards space. Our ascent is well underway, and because this rocket's boosters are so incredibly big, we won't see booster separation until we have pretty much left Kerbin's atmosphere altogether. There go the side boosters, and we are now flying on the power of only the remaining nine central Mastodon engines. After a few minutes, the first stage engine shut down for just a little while as the rocket coasted up to apoapsis before re-lighting and doing a final circularization burn to get this massive rocket into Kerbin orbit. Now, as we wait for our Jool transfer burn, we can jettison the very scuffed fairing and expose the lander as well as the rest of the vehicle to space. And yeah, for simplicity's sake, I will be calling it the lander. The solar panels are deploying now, too. And I even put a little extra ray in the service bay at the top of the lander so it can be provided of two. And I think that we are now configured and ready for Jool transfer.

[00:02:31]So, as the sun sets below Kerbin's horizon on our second orbit, we light the first stage engines for one last time, starting our 1,900 m/s burn to get us to Jool. The first stage propellant tanks are now empty, so we drop off the excess mass and light the four Rhino engines on our second stage.

[00:02:47]After around 100 seconds of burning, we get our Jool encounter so we can shut down the engines and coast away from Kerbin.

[00:02:54]And I'll keep saying this in every video, but wow, Blackrack, you have truly outdone yourself with these volumetric clouds. And of course, all the other modders working to make KSP as realistic as possible, you are what make this game great.

[00:03:06]Anyway, by now we are already a few years into the mission and are currently doing a small trajectory correction burn to set up an encounter with one of Jool's moons, Tylo, which will help us capture around Jool for way less fuel.

[00:03:18]And there we go. Now, all there's left to do is wait.

[00:03:32]>> [music] >> And here we are, the Jool system. In my opinion, this is one of the most photogenic locations in the entire game.

[00:03:44]So, you probably saw that we just flew past Tylo. That gravity assist slowed us down enough to capture us into Jool's orbit, and it will slingshot us toward a Laythe encounter, whose gravity we will use to lower orbit even [music] more.

[00:03:58]Once we are past Laythe, we'll do a 300 m/s burn at periapsis to enter a highly elliptical, but stable, orbit around Jool.

[00:04:11]This is one of the very few cases where you really get to see Jool from this close.

[00:04:16]One of the last steps before entering Jool is getting the crew on board the descent vehicle. Three of the Kerbals on board will go on EVA to transfer into the lander, leaving the nuclear stage to be guided by the remaining four Kerbals on board. Now, to get an idea of what exactly is about to happen, after the lander detaches, the nuclear stage will do a burn at periapsis to achieve a circular low Jool orbit in preparation for the later rendezvous and docking.

[00:04:40]The lander will then swing around one more time, and then go straight in.

[00:04:44]All right.

[00:04:45]Let's go make history.

[00:05:34]>> [music] [music] [music] [music] [music] [music] >> Welcome to Jool.

[00:06:45]We have entered the upper cloud layer, the layer with the lowest visibility on the entire planet, and we will continue sinking further and further into the atmosphere [music] for at least another 50 km.

[00:07:25]>> [music] >> We have now reached the lowest point possible in Jool's atmosphere at 230 m below the game's defined sea level and only 20 m above the kill sphere, where any craft is instantly crushed.

[00:07:41]The rotors will now spin and the fuel cells will start generating power as we enter a hover inside of the gas giant.

[00:07:48]One of these scientists on board is now going on EVA to perform and collect some experiments that we have brought along with us in the service bay.

[00:07:55]And look at how many science points that is delivering us.

[00:07:58]And this is still nothing compared to what we will get when we work it out in the science lab aboard the nuclear stage.

[00:08:04]This craft is using fully stock plus of course DLC parts, but even in a 100% unmodded instance it works. So, I hereby challenge you to also reach Jool sea level and return to Kerbin. Now we have enough fuel to power the rotors to stay at Jool for several hours at least, but let's not waste any more time down here.

[00:08:22]Let's jettison the large inflatable heat shield and go home.

[00:08:27]We are now rising back through the awesome volumetric storm structures still at a fairly decent speed and eventually we are back at the thick upper cloud layer.

[00:08:45]After nearly 15 minutes and 70 km of ascending, Jool's gravity finally starts to overcome its thinning atmosphere.

[00:08:55]And this is when the real challenge starts.

[00:09:41]>> [music] >> And there we go. Orbit has been achieved. The entire powered ascent is actually really difficult to get right.

[00:09:55]I reached orbit with less than 200 m/s left. So, we'll have to use the nuclear stage to set up the rendezvous with the ascent vehicle. And we still have plenty of fuel in the nuclear stage, so that's not going to be a problem with docking or anything like that. So, we are approaching the ascent vehicle now.

[00:10:10]We don't have any proper RCS thrusters, so I'm just going to point the two craft at each other and fire. There we go.

[00:10:17]And we are now docked.

[00:10:19]So, the Kerbals will transfer back into the nuclear stage and we'll even transfer all of the remaining fuel from the ascent vehicle into the nuclear stage just to be safe. It's not really necessary.

[00:10:28]And after waiting a few months for a Jool to Kerbin transfer window, we are going to separate from the ascent vehicle and when the time is right, we're going back to Kerbin in one giant 14-minute burn. So, there we have ignition with all five nuclear engines at full thrust.

[00:10:44]After a few minutes of burning, the fuel of the booster engines runs out, so we ditch those and are now left only with the central Nervas. And after a massive burn, we escape Jool's gravity and get an encounter with Kerbin. There goes Jool. What an awesome planet. I actually really had fun designing the lander and also figuring out how the rotors work in this game. I'd never really used robotics before, so this was yeah, pretty cool.

[00:11:07]Anyway, we are now on a trajectory into Kerbin's atmosphere and I'll let you enjoy this re-entry in typical Kerbal fashion.

[00:11:41]>> [music] >> And that is a wrap. For one of the first times in documented KSP history, three Kerbals have been successfully returned to Kerbin after reaching Jool sea level.

[00:11:52]This was a very fun mission and I hope you enjoyed it as much as I did. In the description, I have a video of the entire mission to prove its legitimacy.

[00:12:00]And yeah, if you like this video, please consider subscribing to my channel. And if you really want to support me, you can become a channel member where you get exclusive video status updates, shout-outs in every video, and you also get to fly on potential future KSP missions. Okay, thank you for watching.