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Hello everyone! The capstone of stock KSP missions is the “grand tour” - landing on every planet and moon in the Kerbol system. (You can technically land on Jool but that’s not traditionally counted). A single launch grand tour is a feat of precision engineering, careful mission planning, and the dedication to actually fly fifteen landings and return safely. The first mission I'm really proud of was a grand tour mission (which was also my first ever Eve return), and I posted an album of it on this forum. The mothership looked something like this: And this was the entire craft: Like most grand tours, this is a very large rocket, and I completed this mission mostly through pure brute force. I did use some gravity assists, but this rocket absolutely conforms to the "More Boosters" philosophy more than anything. This was done in October of 2020, shortly after I started playing the game, and you can see that in the distinct lack of optimized craft design. But that was two years ago, and since then I've gotten much better at craft optimization, gravity assists, piloting, and the game in general. Probably the best example of this was the Eve lander of this early mission, which looked like this: It’s a pretty large lander and way overbuilt for Eve, but it got the job done. And then a while ago I did a 7.5 ton Eve mission, which I later cut down to just under 7 tons. This is still the record for lowest mass kerballed Eve return without abusing “magic wing” type glitches, even without ISRU. It gave me an idea - since this Eve lander was so much smaller than my first one, could I make a grand tour mission, but this time putting a special focus on minimizing mass? I first started thinking about a minimalist grand tour in February of 2022, but exams prevented me from doing much more. I revisited the concept in June, and managed to cobble together something vaguely resembling a craft - but I was occupied with graduating college, and it never flew. Here’s a picture of it anyway - it is similar in concept to my final design: This was only part of the final craft, and was already projected to be much smaller than my previous grand tour - at the time I estimated a final mass of around 20 tons. As far as I’m aware, this would still be the lowest mass grand tour ever, as the lightest I know of is Brad Whistance’s 25 ton craft which made heavy use of ISRU. But this was unsatisfying - I was still leaving a lot of mass on the table. My original grand tour mission used Mammoth engines on the first stage. I wanted to have the mass of my entire craft be less than the fifteen tons of a single one of those engines. About a month ago, I finalized the design of the craft: 14.45 tons - well within my mass goal of 15 tons. As you’ll see, I could have pushed this even lower, but I chose not to because I had already met my goal. A breakdown of the craft design is below. I made a video showcasing this mission, also. I've put my comments on it (time stamped) in a spoiler box below.

The challenge was to make an entirely rocket based SSTO that launches vertically. I added another element of challenge which is that I only used 1.25m parts. This means that I can't get the same performance as if I used a Mammoth and a cluster of nuclear rockets, but this approach keeps part count and mass down. The rocket consists of a Vector engine for Kerbin takeoff and landing, and two Nerv engines for everything else. Inside the fairing are a command seat, reaction wheel, battery, and a bunch of Mk 0 fuel tanks. This rocket is very aerodynamic so I take a shallow ascent profile. At 1500 m/s I shut off the Vector engine and let the Nervs continue. I'm not using all the oxidizer here because I need it for the landing back on Kerbin. In Kerbin orbit I use the same sequence of Mun assists that I always use for an Eve transfer. Mun assist brings me into an orbital resonance that gives me a better assist three orbits later, which brings me into an orbit that gives me a final assist 3/4 of an orbit later. This flings me onto a 6:5 resonance with Kerbin, where I intersect Kerbin for another Mun assist, which drops my orbit down and gives me a plane change, where I get an intersection with Eve's orbit. I don't have enough Eve relative velocity to do a Kerbin-Eve-Kerbin-Kerbin-Jool route. So I do a Kerbin assist, followed by another Eve assist, to get greater Kerbin relative velocity. This gives me a Kerbin assist that puts me onto an orbit intersecting Jool's orbit. I need to intersect with Jool's orbit at the ascending node of Eeloo with Jool, but Jool is in the wrong place. So I swing by Kerbin one more time to adjust my orbital period. My problem now is not too little energy, but too much energy. I have to eject from Jool in a nearly prograde direction in order to reduce my Eeloo relative velocity, but that would put me on an escape trajectory. Instead, I use a Laythe assist to bleed off velocity relative to Jool and also do a plane change to line up my descending node with Eeloo's apoapsis. Doing this reduces the capture burn significantly. Laythe assist Only 35 m/s to capture around Eeloo. That's quite good In low Eeloo orbit, and I've got plenty of fuel to land and take off again. This rocket is tall so landing was a bit of a challenge. I had to quickload a bunch of times. Eventually, I found a flat enough place to touch down. The question is, is 1403 m/s enough to get home? Eeloo ascent In Eeloo orbit with 820 m/s remaining. This should be enough, as long as I remember to save enough liquid fuel for the powered landing on Kerbin. Jool transfer. As you can see, I can't get a Kerbin transfer orbit directly from a Jool transfer. Instead, I use a Tylo assist to build up relative velocity to Jool. The problem with this is that I can't eject from Jool at the right angle. Closeup of Tylo assist. 570 m/s left. I definitely have enough to make it home at this point so I accept a less than optimal correction burn. I solve the problem of ejection angle by setting up a second Jool assist at a better angle. Kerbin encounter plotted. I use Kerbin and Eve to slow down, and thanks to the double Jool assist I have more than enough energy to do so. Using the body lift of the near empty fuel tanks to slow down Terminal descent using the last of the oxidizer. Landed back on Kerbin.

I'm sure we're all familiar with the "Tylo flyby to perform a Joolian Capture" For whatever reason, this is extremely easy to perform. I suspect this has to do with the orbital period of Tylo. Any longer and there's a solid chance we'd end up missing it sometimes (if I'm correct) Now, how about the opposite? Using Tylo from Laythe to boost yourself down to a Kerbin encounter? Now, I want to preface this by saying I've accomplished this 2 times before, so I know it's possible–people have mentioned to me it wouldn't be possible before. See here for an example of a successful demonstration. And here's the resulting solar orbit. I am also able to add about 0.5m/s at Laythe and reach Eve as well, if I wanted. Now, how about the opposite? Using Tylo from Laythe to boost yourself down to a Kerbin encounter? Now, I want to preface this by saying I've accomplished this 2 times before, so I know it's possible–people have mentioned to me it wouldn't be possible before. Theoretically, it's completely possible, and I have proven I can do it. The issue comes from the compounding variables involved. If we don't enter a parking orbit around Jool, we're tethered to Laythes orbital period. We need to perform a minimum magnitude of a maneuver to encounter Tylo with enough energy so that when we eject solar retrograde out of the Joolian system, we end up with a low enough periapsis that we can encounter Kerbin. The problem begins to compound here. We have to encounter Tylo such that our ejection angle if we were to lower our periapsis of Tylo to around 10,000 or slightly higher (for greatest affect) results in a solar retrograde ejection. In order to do this, we have to change our magnitude and maneuver time in order to adjust this. But we cannot go below a certain magnitude. As you can see, this has resulted in me (over the course of a few months) spending hours and hours (sometimes 8 in a day during the summer) fiddling with maneuvers and getting what is basically chance encounters with Kerbin. I have been searching for a way to make this consistent, but have not been able to. Mainly, I end up restarting and eventually I end up choosing a good enough place and amount of orbits to start my encounter and things go smoothly. If I restart, I can't usually replicate it for a while. This maneuver will take me more than an hour to plan because of this, if I'm lucky, I might get it in half hour. I thought maybe a parking orbit would make things easier, but that adds extra Delta V to the requirements of the maneuver and results in me getting less Oberth effect bonus. (But you can lower your orbital period to add more opportunities/more accuracy) This is all before, by the way, lining up the maneuver duration to actually make the transfer window. This is complex and adds to the issues, but I feel this can be optimized once a consistent method for planning the maneuver setup can be achieved. Some people have said to me this is too specific to even be possible. But others have casually mentioned the ease of execution of a Tylo>Kerbin. I am at a loss. I spent another 4 hours yesterday after work trying some different methods, and I found Bradley Whistance's video on Gravity Assists. He states that step 2 is to achieve the magnitude required to "place your apoapsis" by adding prograde and then moving the maneuver forward in time to continuously add energy into the maneuver. But this hits diminishing returns with Tylo (since it seems I need an apoapsis between Tylo and the next moon Bop in order to get to Kerbin) and I haven't been able to even get close with his method (he used the Kerbin system for this demonstration) If anyone else can provide some help on the issue, that would be greatly appreciated. I definitely need some other opinions right now.

This I call an episode of Accidentally going to Space I was surveying for my Mun city, and adjusting some terrain on the mun using kerbal konstructs, and accidentally lifted the ground above the kerbal's head. I decided to see where this would go. It speeds were moderate at first: But a few minutes later, as I approached the core, things really picked up. Note the Gs KER is reporting. Suddenly, the direction fliped. We'd flipped round the core, and were now shooting out the other side. I was thinking he might impact on the surface from below, but that did not happen, weather because that's not possible, or we were just going to fast. But nope, Lanbro was rappidly making his way to the stars. I soon discovered I could not timewarp at all. Or leave the space center. I checked the log, and it didn't yield anything I found useful Interestingly, all along the game treated him like he was ragdolling across the surface. I had little control over his actions. According to the EVA report, he was in Kerbin's desserts. I assume because he's now considered landered, but in the Kerbin soi Eventually, I got bored of waiting with nothing new happening, and no time warp - so I called it in and looked at the F3 details. Take a look at those Gs. And so, I have a proposal for you. Mine down to the core of the Mun. Maybe Kerbin Even. Start dropping spacecraft down there. The planet cores could be a source of infinite delta V. Or perhaps repeat the experiment with something that has instruments.

Dear Everyone, I need some advice on gravity assists, I have already tried twice to get a correct encounter from Pol to Tylo to Tylo to Kerbin. Whenever I get out of Jool's Sphere on influence the craft always going the wrong direction. At what time and place does the moons need to align to guarantee that my ssto will go the right direction back to Kerbin. Sincerely Mk3 Maniac.