camacju

Also - the series of gravity assists to get to the Mun is ripped off from inspired by a post by PLAD, but I use fewer gravity assists. An 843 m/s burn gets me an orbit that just reaches Mun's orbit and pulls me up into a higher orbit. After 7 orbits I get another Mun assist that pulls me up into an orbit higher than Mun. This gives me a Mun encounter after one more orbit that is pretty much an ellipse and only requires 205 m/s to circularize instead of 250 m/s. I had enough fuel that I didn't need to do this but it's useful for saving those last droplets of fuel. Some further thoughts: The lander consumes 34 funds worth of fuel and uses 2543 m/s of delta-v. I bet I could get delta-v usage under 2500 with more careful flying. The SSTO consumes 146 funds worth of fuel. 88 in rocket mode and 58 in jet mode. Since rocket mode is the biggest part of the mission, it could potentially be useful to add a spark engine or two onto the ship and use that for circularizing the orbit. It'll barely affect dry mass but it will increase specific impulse. Another possible way to increase savings is to use the lander for the final circularization and fly an orbit-once-around with the SSTO, saving the fuel needed to boost the heavy SSTO up to orbit and then pull it back down again.

Another entry, this time showing the true costs instead of using fuel cost (spoiler alert: it's the same number lol) https://imgur.com/a/Vmb2H8f Cost is 180 funds - 18250 in VAB and 18070 recovered The goal here was to have a SSTO and have the lander be able to fit into a service bay. I unclipped the parts from one another as you suggested. Potential areas for improvement: -I could take a more efficient ascent profile - during previous runs I was able to orbit and land the SSTO with more than twice as much oxidizer remaining at the end. Flatter ascent will probably be better in this case -Time the Mun descent better and take a flatter descent - landing on the crater rim instead of in the crater will probably save about 25 m/s both ways -Use the EVA pack more. For example the kerbal and lander could brake into Mun orbit separately and rejoin each other in low Mun orbit. Similarly, the kerbal's EVA pack could be used for small course corrections as well as the Mun ejection. This could be a source of significant delta-v savings since the kerbal is a large portion of the lander's dry mass. -Figure out how to go without reaction wheels and use a spider engine instead of ant engine - but the higher vacuum ISP of the ant will counteract that. I wish ksp had smaller reaction wheels as the tiny size reaction wheel is way overkill for such a small lander @ManEatingApeis this one acceptable?

https://imgur.com/a/wAWNXAS Here's a submission I did for an orbital relay race challenge. The two outer boosters can reach orbit and get back to KSC three times in a row before their fuel is depleted. The center core can orbit four times in a row.

I think the record for lowest dV from LKO to EVE is 873 m/s using many Kerbin-Mun assists. Theoretical minimum is 840 m/s because that's the minimum you need to escape from Kerbin. And if you can get to Eve you can bounce between Kerbin and Eve until you escape Kerbol, for practically no delta-v cost at all. I bet escaping Kerbol using less than 900 m/s is possible.

This was going to be an entry for a low cost Mun mission challenge but the rules changed to disqualify this run. SSTO booster puts a lander in LKO and returns to the KSC. In total this mission used 180.4 funds worth of fuel and was 100% recoverable, for a net cost of 180.4 funds. Name: "cheap mun"

With the current lander it took me 623 m/s to land from a low Mun orbit, and the theoretical minimum (assuming infinite TWR and perfect timing) is 574. So I'm losing about 50 m/s to gravity losses. If you double the TWR then you'd expect to halve the gravity losses to save 25 m/s total. And I would have enough margin in this kind of mission to prefer the ease of the reaction wheels over a 25 m/s savings which represents less than 10% of my margin

@OutInSpace All you need is 1600m/s for a Laythe transfer, which can get you on an escape from Jool. Then get a Jool assist to bring you down to Kerbin. I had 400 m/s more than that - I docked with 2026 m/s remaining

https://imgur.com/a/UPfPgno Year 1, Day 234, 2:37:31, no ions This is a decent mission profile - I timed the aerobrake so I would get an encounter with the station within one orbit. Around Jool maybe two hours could be shaved off but I doubt it. This is probably pretty close to the earliest possible entry under 100 tons with nuclear engines.

100 tons seems like a reasonable limit. Thanks!

So are we allowed to start with our craft edited into orbit? I'm asking for two reasons: 1. Your example submission starts with your craft edited into orbit 2. My computer isn't the best so it'll chug a bit if I have to slap a heavy launcher onto my spacecraft Also from what I understand this is more of an orbital maneuver and spacecraft efficiency design challenge, not a piloting challenge? @OutInSpace

https://streamable.com/trowtq I know that this challenge is over but I wanted to add this submission. With a bit of lateral thinking, I got this nuclear powered waverider all the way up to 25780 m/s under 50 km. https://imgur.com/a/3qiPMQ6 Here's an imgur album detailing the first part of the challenge and to prove that all the rules were met. The mothership has four rapier engines and is a single stage. At 20 km, the waverider is dropped and continues the rest of the way to orbit. *** Some time later, the waverider arrives back at Kerbin with 21 km/s of relative velocity, at which point it expends the 4500 m/s it has remaining and speeds through the top part of the atmosphere. It doesn't spend long enough in the atmosphere for heating to have an effect.

Honestly a pretty good lander for this challenge, in terms of cost and ease of flying, consists of one ant engine, two oscar tanks, a reaction wheel and a battery. From LKO you can complete a Mun landing and return with about 300 m/s left. The electrical systems aren't strictly necessary but they make the flying considerably easier. Unrelated question - If I recover all parts of my craft on the runway, will I be able to use only fuel costs? There won't be any difference and the fuel cost will be an accurate measure; I just like keeping all my ksp forum challenges in the same save. @ManEatingApe

@ManEatingApe The clipping isn't necessary for the lander to fit into the service bay; I just left the reaction wheel clipped because I forgot about it. Same with the engine. Both sections of the craft landed at the KSC; all parts were recovered at the KSC. So I assumed that I would get a 100% recovery value. If this isn't reasonable then I'm happy to re-fly the mission. I had Mechjeb landing autopilot enabled for the Mun landing but it wasn't managing vertical velocity correctly so I was manually flying for most of the landing. Only at the beginning, before I realized the autopilot wasn't working, and at the end, when I wanted a better suicide burn, did I use Mechjeb.

https://imgur.com/a/xpcgZPK @ManEatingApe Here's my submission under the new rules (just because I don't feel comfortable having a top submission under old, easier rules), so I flew a combination of my 2 part and 3 part designs, spending 179.8 funds. I'm honestly surprised that the rapier alone spends less fuel than the nuke and rapier. I guess the mass of the nuke changes the mass ratio too much in a 5 ton craft.

... I was trying to do a quintuple Mun flyby to save fuel, and I made KSP get a stack overflow. Maybe I'm putting too much effort into this

Another option would be to get into an almost-orbit that's high enough that you can orbit once around, before circularizing with the lander. Then glide back to KSC

https://imgur.com/a/eDGYt8m Instead of doing a full redesign with this lander I took it to Minmus and Gilly for 126.9 funds of fuel. I could probably do a Bop or Pol mission with this thing also.

@IncongruousGoat1.10.1

Well... Unfortunately I was too late to finish this mission before the rule change that pretty much breaks my whole mission (I think just the recovery penalty alone is way bigger than my fuel cost), but here is my mission that uses 128.85 funds worth of fuel. https://imgur.com/a/NnpPUoJ I could have maybe (and this is a big maybe) aimed the last three stages at the KSC but the first stage is a lost cause. At least my first submission with the SSTO and lander works. Honestly I could still pull off some optimizations that I've since made but it'll probably not be a very big difference. This mission will probably be good as a lower bound though. A quick summary of the mission: Boost with rapier until 1700 m/s Get into an almost orbit with the second stage, and decouple to throw the lander into orbit Get a Mun assist that gives us a second Mun encounter - a free return trajectory, to recover the spent oscar tank, and a better encounter in general. The rest of the mission is very standard because I lost motivation to keep saving funds after this mission got borked. Actually I don't know if this is a loophole but I might be able to make this thing work under the new system also. @ManEatingApe Would it be within the spirit of the challenge to launch a recovery vessel with a claw, thereby achieving 100% recovery savings by bringing debris to the KSC? If so, I would like to submit this craft along with a design of such a craft. I'll demonstrate it working on land and water to prove that I could recover debris from anywhere on Kerbin given enough patience.

I'm working on another relatively large design change. It involves a two stage lander mounted sideways in a service bay using one ant engine and two oscar tanks. The ascent profile is pretty much the same. Boost with a rapier, get into orbit with a spark and FLT-100. The orbital maneuvers are different. I'm using a Mun assist to boost myself into an orbit with 1.5x the period of Mun. However the primary reason isn't delta-v savings this time since I've got more than enough margin to do everything normally. The reason for this is so I can get a free return trajectory that's also in a prograde direction relative to Mun's rotation. I drop one of the spent fuel tanks here and let it coast down to Kerbin, while doing the rest with the remaining ant engine and oscar tank. I haven't gotten to the actual Mun landing yet but I should be able to do it. Total fuel cost so far: 63.92 funds for the jet stage 29.12 funds for the spark stage 17.77 funds for the first oscar tank Maximum possible cost from here: 18.36 funds for the second oscar tank Maximum total cost: 129.17 funds I will probably finish the mission later today

ok uh that's quite unfortunate for me since I wasn't paying much (any) attention to where I recovered the stages, so the metric I was using for cost was just fuel cost. @ManEatingApe Can fuel cost be the metric used? It's going to be a lower amount if I don't land at the KSC and now that I'm doing completely unguided reentries I don't want to have to aim all the stuff directly at KSC Also I just realized that KSP doesn't give me the mission reports for recovery in sandbox mode so the only metric that'll be usable for me will be fuel cost

https://imgur.com/a/Iy282kj 168.9 funds used. Looks like I found a way to significantly reduce cost lol The breakdown is 72 funds used on the jet engine stage, 34.5 funds used on the first rocket stage, and 62.4 used on the lander stage. I'm still using more funds on the jet stage than any other, which suggests room for improvement by attaching a Wheesley engine for early slow flight.

I've tried a bunch of non-DLC designs. This is the closest one I could come up with that's remotely capable of going to Mun and back but jetpacking is involved. Those DLC fuel adapters are just too good, lol

Service bay is the same mass as a fairing big enough to hold a kerbal/rocket, and a lot less draggy. I tried using fairing designs but they always had greater drag losses than the service bay - more than enough to overcome any cost savings I could get with the fairing.

https://imgur.com/a/2jXgD8p Here's Lunex 3 - I take a small two kerbal habitation/science module to the Mun and back to Kerbin