camacju

Does EVA propellant count as monopropellant?

That name's fine, thanks! (:

This should count for something, I think. SSTO to Moho and back, with a bonus stop at Minmus, using only one orange tank as fuel.

I've cheesed a similar challenge like that before but I suspect that with sufficient aero mechanic (ab)use, a significantly better result is possible.

Are aero exploits allowed? If so, electric props will *probably* be the best option.

Root fairing produces a ton of drag only if the front and back faces aren't properly occluded, which may have been your problem. This bug has not been fixed as of 1.12 so it likely never will be.

There's an interesting bit of KSP tech called "Root fairing body" that I use frequently to squeeze a little bit more out of my missions. If the root part of a vessel is a fairing, the fairing shell produces no drag - it can be any shape you want - and only the fairing base will produce any drag. The fairing will still shield any parts inside it from aero heating or drag, making it perfect for a cargo SSTO. This means that if the fairing's front and back nodes are fully occluded, which you can check using the aero debug info (enabled from the debug menu), the entire fairing will produce very low drag. In fact, if you've heard of "magic wings," a properly angled root fairing will have a weak magic wing effect. I haven't gone far enough into optimization to need this yet, and it results in pretty odd looking crafts. So I have the Rapier, the shock cone, and a few random structural parts attached to the fairing's main node and interstage nodes to provide an extremely low drag craft. Once I leave Laythe's atmosphere I can pull off the occludor parts since I don't need any special aero properties anymore.

I actually didn't think people would appreciate the details! I'd be glad to go into the mission. The challenge here was to land the Jool-5 using only one engine. I decided to not go with a mammoth + mining setup because I don't like mining, so the obvious choice was the Rapier (Rapier craft have a max payload fraction somewhere between 50 and 60 percent, but a Mammoth can get maybe 25% if you're lucky). The main design constraint here was to get a craft that could do the Tylo landing using one Rapier engine. I decided pretty early on that a single stage design would be really massive and maybe not even possible, so I came up with something pretty similar to the final craft - having a single drop tank that's dropped on descent, detaching more tanks with EVA construction on the Tylo surface, and doing the ascent on one stage. Another design constraint was to get a plane that would be balanced with cargo and without cargo. Normally this would mean putting the engines and cargo at the center of mass, but this obviously wasn't possible. This meant that I had to deal with some center of mass shifting between ascent and descent. I minimized this by using the fuel tank cage design that you see in the final mission, so the payload can fit between the Oscar tanks and sit nearly at the center of mass. This made docking a bit harder, but it made the ascents much easier. The plane itself is a pretty standard root fairing body SSTO, except the fairing is wide so it can fit the payloads. I always use the Big-S wing strakes for a craft because they have a free fuel tank, which saves some dry mass. Now for the actual mission: I launch six modules into low Kerbin orbit - five fuel tanks and one service module (containing a probe core, the Tylo drop tank, and some liquid fuel for Laythe). I probably could have gone with four fuel tanks instead of five, but I wanted to be safe. The first and most of the second fuel tanks are used for a Mun transfer. The path to Jool is similar to what I normally take. I use gravity assists off of Mun to get an encounter with Minmus, use Minmus to increase Mun relative velocity, and use Mun to eject into a resonant orbit of Kerbin. Then, I pass by Kerbin and Mun one more time to get enough energy to get an encounter with a different planet. I tried a different gravity assist route after getting the final boost from Mun, just because I wanted to have a little fun with it. I went Kerbin-Duna-Kerbin-Eve-Kerbin-Jool, as I've never seen anyone use a Duna assist while outbound to Jool. Normally you would use an Eve assist instead, but it's not actually that much more effective because your Duna/Eve relative velocity is pretty low on the first encounter, so you don't make full use of Eve's deeper gravity well. Additionally, Duna's inclination relative to Kerbin is smaller, so it's easier to set up an assist in the first place. Upon encountering Jool, I use an assist from Tylo to capture around Jool, then Laythe and Vall assists to put me onto a Tylo intercept with very low relative velocity (~6 m/s capture burn). I leave three full fuel tanks in elliptical Tylo orbit and take the mostly-drained fuel module through a Vall assist to aerobrake around Laythe. Then, I leave it in elliptical Laythe orbit. This will again enable extremely small transfer burns. After the Laythe landing, I pull off all the unnecessary parts from the craft using EVA construction, transfer to the fuel tank, and pull as much fuel as I can from it. Then. I do the Vall landing before transferring to Tylo. The reason for this is that a Vall->Tylo transfer needs much less of a capture burn than Laythe->Tylo, and I have enough fuel to do the Vall landing without needing to drag another fuel tank along with me. The Tylo landing is the hardest part of the mission. I take two fuel modules down to low Tylo orbit (in retrospect I probably could have used just one) and then do the Tylo landing. Then I bring the fuel tanks back to an elliptical Tylo orbit and dock with the final fuel tank in elliptical Tylo orbit. The other two landings are pretty trivial, as I don't do any fancy docking stuff again. I did do multiple Pol flybys to correct inclination and relative velocity, but I had enough spare fuel to not need this and this was just for fun. If you've got any more questions about it, please let me know!

The single engine Jool-5 is finally complete! It's kinda hung out in the limbo of incomplete KSP missions for a long time now, but I finally dredged up the motivation to complete it.

There aren't really any high-pressure engines from the DLC (I believe Vector beats the Mastodon anyway). However, Breaking Ground is super useful for Eve ascent vehicles because you can use props. If I remember correctly, I've gotten an electric helicopter up to 45 km on Eve, and nearly 40 km carrying a payload. This significantly reduces the required delta-v - you're higher and thus have more potential energy, and you also have higher specific impulse because there's basically no atmosphere anymore.

RSS is significantly harder to do this than OPM. I think these should at the very least be on different leaderboards.

Funnily enough, many designs are even more optimized than this. Some plane designs can't quite maintain level flight at the end of the runway, so you have to dive down to sea level to pick up the required amount of speed. Going further into optimization land, there are planes that can't take off from the runway at all, so they accelerate on the flats around KSC. Even further are the hills near KSC, where you roll down the hill and accelerate across the flats, picking up speed. And finally, for when you really really need minimal wing area, I've seen people use the polar ice caps as an incredibly long runway, where the plane can only attain level flight after accelerating across the entire ice cap. If you're just talking about lift, a 5 degree angle provides a great lift to drag ratio, so it's great if you don't need higher lift than that. If you do, then it might be better to use more wing and fly at a lower angle of attack, knowing that you can pitch up and get lots of lift for a good L/D ratio, like you said for Laythe. (My most recent Laythe SSTO struggles for this reason - I have to dive down the slope of the crater lake island, and use the nuclear engine as a bit extra thrust, in order to pick up enough speed to stay level).

very impressive!

https://imgur.com/a/DFyKE42 Here's a mission like this I did a while ago - Duna and back using only the Pods and Engines categories. I use Twin-Boar and Poodle engines, plus some SRB for decoupling purposes.

Yes, it's when you have a well balanced wing area. For a super high performance craft, you'll want at least 6 tons per unit of wing area. I'm not aware of one - maybe @Lt_Duckweed could make a video about advanced SSTO design for his next Kerbal University video? He knows this stuff better than I do.

5 nukes for 8 rapiers is actually a little low. I tend to use between 2/3 and 1 nuclear engine per rapier, so I would suggest adding another Nerv. The reason is that you don't have much TWR on the Nerv so you do need quite a few for a large craft. The Big-S wing parts in general have good heat tolerance plus a "free" fuel tank (zero extra dry mass). The strake in particular is useful because, as Duckweed pointed out, it has a better fuel capacity per mass than the large delta wing, but also because you can fine-tune wing area more easily (increments of 1 wing area rather than 5). Smooth angle snap isn't really necessary unless you are squeezing out the very last drop of performance from a design, and then as you go further down the optimization rabbit hole, you begin to find that lower wing incidence can perform better in some situations. So I think just a 5 degree incidence is perfectly fine until you go very far into optimization land. (If you're not doing some funny stuff with fairings as your craft's hull, you always want a 5 degree incidence, since that gives the best lift to drag ratio. If you are doing funny stuff with fairings then technically -22 degree wing incidence is "best" but that's probably outside the scope of this thread)

When you say "Mods are not allowed," what kind of mods are you referring to? I assume that part mods are disallowed, which I think is reasonable, but would any of the following also be disallowed? -Informational mods (Kerbal Engineer Redux, Trajectories, etc) -Autopilots (kOS, MechJeb) -Visual mods (Waterfall, Astronomers Visual Pack) -Other utility mods (Kerbal Alarm Clock, BetterTimeWarp) -DLCs

Yes, that's the basic idea. For a bit more complex of an explanation: The craft consists of four "stages." The first stage is powered by two small DLC rotors with a maximum size motor (you can probably get away with a smaller motor, saving mass and cost), each with eight basic fins rotated 20 degrees. Basic fins are great for an Eve helicopter because while they don't have a good top speed, they have much more wing area per mass and per fund than DLC propeller blades, and they don't fall off a cliff once their velocity passes Mach 1, meaning they can spin faster and generate more lift in the thin air. Additionally, centripetal force will pull the basic fins outward when the rotors spin up, meaning I can package the helicopter more conveniently and have it expand later. The ceiling of the helicopter stage is probably somewhere around 36 kilometers, but I found that detaching it at 35 kilometers is sufficient to get to orbit. It's powered by solar panels because it needs to ascend for a long time, and would require too much battery mass. The solar panels double as landing gear. The second stage is powered by three Twitch engines, two Ant, and one Spider. It has a couple clipped Donut tanks and a Dumpling tank. This stage is also very aerodynamic due to the fairing, so it takes a steep ascent in order to leave Eve's atmosphere. It's still able to pick up a good amount of horizontal speed, however. For the third stage, the Twitch engines and fairing are dropped, as well as all the drained fuel tanks and reaction wheel. I guess this is a stage and a half? No electrical systems whatsoever mean that the third stage must be controlled entirely through gimbal of the Spider engine, but I need more thrust than just the Spider, hence the Ant engines which have better vacuum efficiency. This stage is sufficient to get the kerbal almost to orbit. The final stage makes use of the kerbal's EVA pack to finish circularizing the orbit and rendezvous with the return vehicle.

Not only is it kerballed, it's a significantly older version of what I ended up doing. Here's the most recent version of the lander: 4378 funds, 1779 kg, not including kerbal. This can bring a kerbal from Eve sea level to low Eve orbit with about half of a jetpack remaining. This implies further room for both mass and cost reduction but I don't want to do that. I actually abandoned the "lowest cost to Eve" mission in order to do a "lowest mass to Eve" mission. Turns out, a low cost Eve ascent vehicle tends to also be quite low mass. I got the total mass at launch down to 7.5 tons, which I believe is a record (that is, for missions that don't abuse aerodynamic bugs). Here's the video I made about the minimal Eve mission:

I would... except you've already got a great time! 16 minutes is faster than what a jet-only craft can do, and I don't really want to mess with rockets for this challenge

Launch 1: Duna advance team, return module 65492 funds in VAB Duna transfer. The transfer stage is also the Duna return stage, and takes the Duna return module along with the forward operating base. The base is lonely. Let's hope it gets some company soon. An interior view. The four dunatians are having a fun time. Bonus: My provisional design for a Duna ascent vehicle.

Here's the rocket I'm going to be using: The lower stage is a Clydesdale and the upper stage is a Wolfhound plus three of the 1/8 length 2.5 meter fuel tank. It can bring 40 tons of payload to orbit while expending 11015 funds of fuel. Both stages are fully reusable. In practice I'll use a slightly higher fuel load and a slightly lower payload mass for some extra margin, but I don't expect the cost of any payloads to be over 80000 funds.

If your craft is properly drag optimised, 55 tons per Nerv should not be too much to get into orbit, even with zero Rapier closed cycle. I've gotten the best results with 3 Rapiers and 2 Nervs for a 110 ton craft, so doubling it would give 6 Rapiers and 4 Nervs for a 220 ton craft.

Looks fun! Are we allowed to use a recoverable SRB plane for this? It'll probably be the best option for efficiently putting stuff in orbit.

usually it's a good idea to post your own completion of the challenge, just so everyone else knows it's possible