Nefrums

I reused an old design i used on the stock payload fraction challenge. It is a bit smaller than other designs shown here with a takeoff mass of 146t. It spent 6071 LF and 2640 OX, so i guess 5332p

For my entry I used only three engines. By letting the nosecone overheat I was able to reach 1640 m/s in air breathing mode, This greatly reduced the amount of lf/ox I needed to carry. Last entry i made had 13 oscar b tanks, this one needed only 6. I found that the radial ram intake gave better performance then other intakes, they seam to have better drag/intake air ratio then other intakes. I needed 3 of them to avoid the rapier loosing thrust at 15+ km altitude I made LKO -> Laythe for 1024.5 m/s dV by starting with a muun flyby. I used a two stage ion lander for val, That is staged batteries. This allowed me to land on Vall with only one ion engine. Instead of rtg i used one solar panel. This made the battery recharge time go from hours to days. My Tylo lander had only 4k m/s dV but this is enough to land at 9km altitude. The lander will roll over on landing but jeb can flip it. Take of mass is 8.6 t

Well done! I'll post my entry later tonight. I like the trick with the antenna! I opted for just letting the nosecone overheat. And go with the Oscar b in front above 10km. One tip about the fairing. There is a feature/bug in that the part you close the fairing around does not have its drag affected at all by the fairing. And a part will have its drag increased a lot if it is followed by a smaller part, even if that is bellow the fairing. If you where to replace the t200 tank with 2x t100 tanks and close the fairing to the one in front it would reduce drag and allow for greater airbreathing speed. What intake did you use?

Nice! Getting home should take less than 500 m/s dV, when doing a powered tylo assist then going Kerbin->Kerbin->Eve->(2x kebol orbit)->Kerbin.

Fun to see that so many are still trying this challenge, I bet this is the oldest still active challenge on the forum, considering that it was first posted in 2013. I'm looking forward to see what designs you come up with! @Mesklin have you goten that sub 11t entry working?

It is possible with an ssto. if you stack ions inside a cargo bay... 7 Rapiers and 60 ions, and lots and lots of batteries.

As there is basically no atmo at 20km, ions have 98% isp there. Still this is hard, not sure it is possible.

so if we are allowed to start from LKO what max orbit are we allowed to start at?

Starting at launchpad/runway or from LKO? Do you need to orbit jool or is a flyby enough?

He is on a trip wo Internet access. Said he be back on the 20th. Your entry looks fine to me.

This is exactly what happened in my seccond atempt! I spent some time trying to tweak the ion scooter to be able to both land on vall and circulate on Laythe. The simple and lightest solution i found was to instead bring another 50kg of LF for the Rapier on Laythe. I just set a new personal record 1024.5 m/s for LKO to Laythe orbit!

Lots but to keep it simple. Make sure your landers work before starting. Hyperedit is good for testing them. Bring lots of dV Aerobrake at Laythe when arriving at jool. Try to intercept Laythe close to your jool Pe. Use the inflatable heatshield and keep it for the return trip where it will help with aerobraking at Kerbin. Use Airbreathing engins on Laythe. Have a tug to bring your tylo lander to low tylo orbit and leave your mothership in a high eliptic orbit. As going from high to low tylo orbit is ~800dV. It saves a lot of fuel to not drag your entire mothership down to low tylo orbit Make a Vall lander and reuse it for bop and pol. Keep landers as small as possible. Do Laythe and Tylo first so you can discard the heavy landers so you don't need to drag them around the jool system.

It is clearly jool obsession. How far have you come in your attempt I don't have a fully working ship right now, but I think the three engine design could work. I never actually managed to land on vall but it should be possible. The first ship was below 11 t, but that failed Vall, when I fixed the ion lander it could no longer complete the circulation burn on Laythe.. I have learned a lot over the attempts, Optimal ejection time from Kerbin is around y2d155 01:25 at a 2 degrees to prograde. then flying LKO->Muun->Eve->Kerbin->Kerbin->Tylo->Laythe I think this in theory could be done for just over 1k dV. You need more air intakes than you think. I discovered that with two radial ramp intakes the Rapier dropped to 60% in the later stages of the ascent, above 15km. You can see this by right clicking the Rapier and looking at "requirements met". Oscar-B is the best nosecone above 10 km. Fairings are heavy, but it is worth extra mass to make the fairings more pointy. Spark outperforms Ant on Tylo in all my tests. => twr > dV Fun fact: I'm over 200 on the quick save counter in a save crated in 1.1.2 for the Jool 5 attempts

5,4k dV should be enough to do all three in one go. But note that it is relay hard to return and dock with a chip that is in a high elliptic orbit around another moon. You will have to get the intercept just right to avoid spending lots and lots of dV to match orbits. Laythe is the hardest to take of from when not using air breathing engines. But as you can land with chutes you have all of the fuel left for the ascent. I have made no less then three more attempts at this challenge since my last entry, I just cant stop trying to improve my designs. First failed on Vall, second on Laythe, the third had way to much fuel. I just managed to get another ship to LKO after like 20 attempts. Now lets se if I can move it from LKO to Laythe orbit for 1050 m/s dV at 0,03 twr...

More twr is always better! You might be able to use it for all the joolian moons, if you add some chutes on decouplers and do Laythe first. Try adding 2 or 4 aerospikes and see if it makes landing on tylo easier. The increased twr might make up for the loss in dV. It will certainly make Laythe easier.

strange I don't experience that 1.1.2 creches a lot, I have had 2 caches in 20+ hours. Might be mod related. You'll probably have to wait with the rules question until @sdj64 gets back from his trip on may 20. Nice lander, I think you might get better performance with more twr and less dV. I have a working lander now with just over 4k dV + 600 dV from EVA.

I think I figured out how to do this challenge with only 3 engines.

Thanks! I have tried a tiny LF lander for val, but the problem with that is that it get heavier than using the same ion lander for all the small moons. You could maybe reuse the Vall lander as last stage of a Tylo lander,

Good luck! Jool-5 is one of the toughest but most fun challenges there are is KSP. I would recommend having a look at the Precise Node mod. It makes all those transfer maneuvers so much easier to set up.

The heat tolerance of the lander can have never been a problem, the problem was when aerobraking the Laythe lander with the Kerbal in the seat, It was a lot more difficult than i remember it in 1.0.4, And then I had to aim for the island with the big mountain from a high elliptical orbit, It took a couple of attempts to hit it. Edit: I think lower mass is possible, at least a ton lighter is surely possible. I hope someone beats 12,5t so I get to improve my design! "poke" -> @Mesklin, @astrobond

It actually does work..

Here is my fourth entry for this challenge (this time in 1.1). I have improved almost all parts since my last attempt and managed to get the mass down to just over 12.5 t. I used the same 4 engine design as last time. One rapier for Kerbin and Laythe accent, one spark for Tylo and 2 ion engines for everything else. Mods used: KER, Precition node, and mechJeb+module manager to not require the mechJeb parts. (Only Smart S.A.S was used from MechJeb)

I see no problem with having different levels of compilation for isru entries, and @sdj64 is right, it is not worth it for low mass entries. I've been thinking of doing a 1.1 entry. It will not be as good as the 1.0.4 entries (pre aero heating change that made draggy docking port the only viable nosecone). I spent some time experimenting yesterday and managed to build a 1.6t tylo lander that "should" work

yes I did in my first attempt. But the second is to fast and even the docking port overheated, so i had to use the heat shield.

moooooare boster = 32s