It'snorocketscience

After 15 craft iterations, plus weeks of crashes and learning and tuning, I finally completed my own challenge. The "Duna Phantom" Duna-capable SSTO is here: While it was exceptionally hard to build, I think it shows that prop planes can be a viable way to explore other atmospheres. As far as Duna planes go, this plane is a dream to fly at both Kerbin and Duna... relatively speaking. Not many kerbals were killed in the making of this craft. I'm happy with how this spaceplane turned out. The props and wings save about 550 m/s of dV when leaving Duna! (A normal Duna ascent to orbit costs 1450 m/s, but this plane only needs 900 m/s when starting from a 6km cruising flight.) But Kerbin ascent is a different story. I have no idea what is the optimal SSTO path you guys use. This thing barely escapes Kerbin on its way to Duna, even with 4850 m/s of dV. Could someone tell me if using one nuke for a 15 ton plane is bad? Image album: Stats and optimizations: I'll post a video and .craft file later. Right now I've got to simplify the plane so you can fly it without reading the instructions.

I think you have to offset the blades outside so that they are mostly outside of the fairing (be careful not to offset them too far—that will cause the blade tips to blades to break the sound barrier = bad). I believe KSP decides whether if a part is "hidden" by checking if its center of mass is inside a fairing/payload bay, or not. AFAIK the prop/rotors must produce drag if they are able to produce thrust, but fairings still have the benefit of eliminating drag caused by the electric motor.

I've spent about a week (15-20 hours) improving the same design and learning new things to improve it. It seems like each day I learn something new and use it to fix a problem, only to encounter the next problem and fail again. I finally realized why getting to orbit is so hard with props and rotors. Props suffer from huge drag loses as you approach the 300 m/s zone just before breaking the sound barrier. (Drag naturally spikes near the sound barrier, but spinning wings suffer even more as their rotation speed causes different parts of the blades to break the sound barrier before other parts.) Helicopters have it worse—Google "helicopter speed limit". Even if you shut off your rotors and props and adjust blade pitch during rocket flight, they still produce a lot of drag. At 15000m on Kerbin, 16 stationary large fan blades produce about 5-8 kN of drag altogether around the 350 m/s sound barrier. To put that number into perspective, each wing board and fuselage part produced 0.5-2 kN of drag each during the same conditions. That's awful—the rotors doubled the drag on my small craft. Thankfully there's an easy solution. Place some hinges on your rotors, put the props on top, and set things up so that your props fold back (preferably into a fairing that encloses the rotor) at the push of a button. That should fix things, but I'll have to try it out tomorrow...

Some people were saying that props and rotors aren't worth carrying around to and from Kerbin—a normal SSTO with a detachable Duna plane would be better, they said. Maybe. Maybe not. A good prop plane setup will get you to 15k on Kerbin at 200 m/s or so. I will figure out how much dV that saves empirically tomorrow... But what I love about the "prop SSTO to duna" concept is that the props are not dead weight on Duna. I've done some tests and found that, during ascent from Duna surface to orbit, a prop setup saves 200~300 m/s of dV, plus another 25-100 m/s depending on your engines (engine efficiency increases as atmosphere pressure decreases). There's also the bonus of props boosting your rocket TWR in the lower atmosphere, and the benefit of free Duna landings—no suicide burn or parachute spam required to come to a safe stop. (The dV estimate was determined empirically. It assumes you have a propeller plane that can reach 200 m/s at 7.5k on Duna, and that you manage propeller blade pitch and drag very carefully.) But there's a lot of room for improvement in that estimate. I made that estimate with a craft that had too many wings and fans for Duna. You read that right, I over-engineered my first Duna plane. The plane carries 7 tons of wings and propellers to haul 8 tons of fuel up to 7.5K (19.5 tons total), but a full load of fuel is complete overkill in my case—I only need full fuel tanks to escape Kerbin. Those extra wings and props added a fair amount of drag, which could've messed up my dV estimate.

Of course, leave it to him/you guys to have done everything possible in the game already. Nice work. I haven't watched it yet but I wonder how far the part clipping goes... Does the craft use the R-25 ducted fan blades, or regular props? It's hard for me to tell which type is used on my mobile screen, but if you guys didn't use fan blades then you're missing out on a lot of performance.

I checked the community delta-V map, and if you start from LKO, landing on Minmus costs about 1270 m/s of dV. Meanwhile, it costs only 1080 m/s of dV to fly on a trajectory through Duna's atmosphere, at which point you can aerobrake to a landing. My prop design can land in Duna's atmosphere without burning fuel, so flying straight to Duna and refueling there is the cheapest way. Oh hey, I actually tried implementing a tilt rotor on your helicopter that you posted to Reddit, and it's quite hard. Mounting rotors on top of a hinge will cause it to buckle and bend under aerodynamic forces, but I bet the alligator hinges won't flex as much like the normal ones do. No, unfortunately, as it requires undocking/refueling. But you can tow asteroids in this challenge, so it might be possible (albeit insane) to tow one to low Eve orbit for refueling. That would count as a self-sufficient SSTO design. I guess it really depends on the craft. In my minimal 21~24 ton build, empty fuel tanks add up to about 1.25t, about 9-12% of my craft's dry weight, so it's not that bad. My prop setup, while about as heavy as a jet setup at ~4.75 tons, is not dead weight on Duna. The craft doesn't need to burn any fuel on landing (I think a Duna suicide burn costs a few hundred m/s of dV), and the props have saved me at least 300 m/s during my sloppy Duna ascent test. Even then, it's probably not as efficient as reusable stages, but I'm going to settle this matter by building a reusable stage mission after I finish this SSTD craft. Another small benefit of building an all-in-one Duna SSTD instead of a detachable helicopter is that I can haul the craft's ISRU module to a location with high ore concentration. It's not super useful as I could just use a scanning satellite to pick a good landing/refueling site, but if I was too lazy or poor to launch relay/scan sats ahead of time, or didn't have the scanning tech, there's that.

Dang, it's embarrassing to not have the first entry in my own challenge. But I'm getting close. Here's a sneak peek of the UNFINISHED "Duna-Phantom IIX": I didn't just name it "Phantom" because it sounds cool—the craft file corrupted and disappeared twice during my tests, like a ghost! Thank goodness I made backups. After three days of work and 8 (IIX) iterations, I would've lost my mind. An ISRU, radial ore tank, and fuel cell array are crammed into that middle fairing (see spoiler). Those three bays at the front hold one little drill, solar and radiator panels, science experiments, and one Kerbal in a chair. It's rather cozy (read: cramped as hell), but I managed to fit everything in with almost no part clipping. The floating landing gear is fixed in the next iteration. Click the spoiler below for more specs and tricks I used (they might help you in getting your crafts to work): I'm trying to squeeze out more delta-V from my design - anyone know how much dV you can save with a Mun, Minmus, or Ike slingshot?

Well, an all-in-one prop/rotor SSTO can use its rotating wings to assist landing from and ascend to orbit. I'll admit that that point is kinda moot on Kerbin (jets work) and Duna (barely any atmosphere), but on Eve or Jool, I think it's safe to say that props and rotors one of the most efficient ways out of the lower atmosphere. But even in Duna's case, rotating wings could help save dV. I need to test my 24~30 ton design to measure savings on ascent (probably not much), but I know that a suicide burn on Duna costs a few hundred m/s of dV as the thin atmosphere and parachutes don't slow you down a whole lot. Meanwhile, my winged prop SSTD can land without burning any fuel—it lands like a plane and then uses thrust reversers to stop before the bumpy terrain kills it. Fair point, although a reusable/recoverable stage isn't perfect as it requires extra mass in the sense that it requires another engine, probe core/batteries, reaction wheel/RCS setup, landing gear/chutes, and docking ports. It also adds piloting time/complexity to a mission, which is another moot point, but some people really like the "cool factor" and design challenge of a spaceplane that drops nothing except for its payload. But ultimately, the goal of my challenge, besides being a challenge, was to encourage players to push the limits of rotary-wing crafts, and to develop a Eve/Jool SSTO, if rotating wings can make such a feat possible. That would be quite the achievement.

By the way, does your craft have a name? Also, what's the launch cost? I just want to know for leaderboard ranking purposes. Is it capable of carrying any tourists (I see it can carry one Kerbal in a capsule, but does it have a probe core if that 1 kerbal is a tourist)? I assume it's not capable of carrying a payload, which is fine (I'm beginning to suspect a payload-carrying prop SSTO is a bit too much to ask for).

Congratulations @xendelaar! Your entry is the first to make it on the list. Well, I might just be able to prove you wrong . I was about to give up on my sub-30 ton plane design when I discovered ducted fans. They are so much better than the normal props I've been using.

Found this handy forum post for Duna planes: Also, here are some tips gathered from my own experience and from the thread above: Lift: Drag: Thrust: Edit: Don't use normal props—ducted fans are actually a game-changer. They produce a lot more thrust, significantly increasing effectiveness on Duna and max operating height.The shrouds also come in handy for protecting your props during landing.

Not to mention that BG rotors and props are easier to adjust mid-flight than stock props. To get the most thrust, your prop/rotors must have adjustable pitch. (I don't remember the explanation in real life, but for KSP, just experiment with linking blade pitch to throttle or two keys using the KAL-1000 controller and use advanced tweakables to view rotor/prop thrust so you can fine tune the blade pitch at different speeds). Stock props (that use control surfaces) can adjust their blade pitch mid-flight, but not as much as BG props and rotors can.

The same guy (Reddit user u/Chagaran) I linked in my post who built an orbital chopper SSTO actually built a Duna helicopter, but unfortunately it required orbital refueling. Now, he didn't use ISRUs, nor nukes or ion engines, and his design did have some aerodynamic flaws (mk2 fuselages used as a cool-looking cargo bay at the expense of creating negative lift), but I bet he came close. Link: https://www.reddit.com/r/KerbalSpaceProgram/comments/fi03d8/upgraded_orbital_helicopter_now_duna_capable/?utm_source=share&utm_medium=web2x I just realized something about Duna props—Normally, on Kerbin, large props and rotors require large motors to turn at full power against the drag created by the blades. But in Duna's thin atmosphere, drag is very low, so you can get away with strapping 8 medium or large props on smaller motors, and then add duplicate the setup to create the necessary thrust. If your props and rotors can reach the maximum 460 RPM easily, you need to make them work harder (attach more/larger props) or downsize the motors to save weight. Of course, these overworked props and rotors will struggle on Kerbin, but if you add more of them (you'll need several for Duna, anyway) I think it might just work. I'm getting close to succeeding with my sleek 23 ton MK1 design. It uses an ISRU and is very drag-optimized—the 2 Jr. drills, solar panels, radiators, and science parts are crammed inside 3 small service bays, thereby eliminating much drag. Plus, I've crammed one small converter, radial ore tanks, and fuel cells inside a fairing, eliminating even more drag. Finally, I've got the wings angled up at 5 degrees so the plane can stay level without having to pitch up (which would expose the plane's body to the airstream and cause drag). So it's a really slippery plane—you guys should definitely try to minimize drag in your own builds as well. But all the optimizations in the world can't replace the fact that I need more props. Two props barely even register in Duna's atmosphere. Forget "optimizations", It's time for MOAR BOOSTERS!

You are right in that props have limited performance, but I've been toying around with low-tech jets in SSTOs. If the prop plane can get above 10k, nuclear and vacuum rockets will work at nearly full efficiency. If your craft is drag-optimized, one nuclear engine (or 60KN of thrust) for every 14 tons of weight will be just enough to push it into orbit, at least when starting from 14k at 750 m/s. (That speed wasn't obtained on my challenge craft, I discovered that my prop craft was flawed...) I realized that my Duna verification attempt was flawed (I used stock parts but some mod in that savegame altered the stock parts ), so I'm going to try again in a fresh install to make sure Duna is possible. But I'm fairly sure it is possible—I've built many low-tech SSTOs before that use the "wheesly" jets, and those are only slightly better than props. While we can't use wheesly jets, it should be safe to say that props will get you above the worst of Kerbin's atmosphere (10km). The hard part seems to be being able to take off on Duna on prop/rotor power alone.

Assuming "LFO rocket" means using stages, then that design is not an SSTO. SSTOs look cool, but practically speaking, they're cheaper to use multiple times because you can recover most of the craft's value upon returning at Kerbin. If you were asking "why build an all-in-one prop SSTO when you can build a normal SSTO with a detachable drone", I imagined that a prop SSTO could return to orbit more efficiently than a normal SSTO (jets are deadweight whereas props/rotors are not). Okay, maybe a prop SSTO would be less efficient on Duna because the props would be useless in a thin atmosphere, but on Eve or Jool, the props would be the only way to escape the thick atmosphere. Another practical goal of this challenge was to encourage innovation and find the limits of props and rotors. Just how fast and high can a prop craft travel? I've seen stock props by Brad Whistance travel up to 1000 m/s, although those crafts did employ a few (legitimate) tricks... Fuel cells tucked inside a payload bay are pretty handy for saving battery weight while maintaining sleek, low-drag looks and decent EC production... have you tried that? RTGs and extra batteries get heavy fast, and solar panels add extra drag at high speeds, not to mention that the deployable ones break at high speed obviously Are you using a helicopter or plane design? I've found that helicopters are just too inefficient and heavy - they need rotors with a TWR above 1 while a plane can take off with something well below that. Helicopters also produce more drag and struggle during rocket-powered ascent—pointing the nose up towards space (to use rockets) will cause the rotor blades to pull your craft backward (and upward) unless you shut them off, at which point they become inefficient wings. Meanwhile, a prop plane during atmospheric ascent into orbit can run its props and rockets at the same time, increasing ascent TWR without much issue.

I didn't add Laythe to this challenge because I didn't think it would be practical... why be forced to use props or rotors if jets work on Laythe? With Duna/Eve/Jool there's no other option but to use props and rotors in the atmosphere, and jets would be dead weight.

Jool actually has less gravity on the "surface" than Kerbin does, and the atmosphere thickness at 120k is about the same as 7.5k on Kerbin, but Jool has a mad orbital velocity of 6745 m/s, if I recall correctly. That's going to be a long burn, especially with NERVs, and the drag from the upper atmosphere and gravity losses are really going to add up. So even though I really don't like part clipping, I decided to keep the rules as minimal as possible since the Eve/Jool levels of the challenge are already hard enough as it is. I think the transfer from low Jool orbit to Laythe is around another 3000 m/s of dV, too (I think?).

Design a SSTO that uses propellers or rotors instead of jets during atmospheric ascent I like useful challenges, and I hope this one may be considered as such. The goal, besides challenging oneself, is to create a new type of SSTO that can explore atmospheres with props or rotors, thereby saving fuel and enabling the exploration of oxygen-free bodies, like Duna. This would enable a craft to biome-hop for science or transport resources much more effectively than slow rovers and fuel-guzzling rocket planes/landers can in said atmospheres. While these kinds of biome-hopping and transport crafts do exist, they don't seem to exist in reusable SSTO form, it seems. Props and rotors, unlike jets and intakes, also have the benefit of not being dead weight on Duna. So while props may offer worse performance on Kerbin, they'll pay you back during Duna ascent. Or at least, that's the theory. Requirements: No airbreathing engines. The craft must be capable of flight using rotor/prop power alone in the destination planet’s atmosphere, but you can obviously use rockets to get to and fly in space. Self-sufficient SSTOs only. So, ISRU mining is allowed, but no assistance from external ships (asteroids are OK). You may not jettison any parts other than payloads that don’t help the main vessel in any way. Normal difficulty or harder, but for convenience, you may ignore commnet—pretend a network is already in place. The SSTO must be useful in career mode. There’s no point in a spacecraft if you can’t bring any Science, Kerbals, or payloads along. Carry at least one kerbal (chairs allowed), OR if you wish not to carry kerbals, carry at least 0.2 tons of parts from the “science” category, OR deliver a payload weighing at least 0.5 tons. You may drop payloads once you are landed at your destination. If your destination is Jool, you may drop it low Jool orbit or into the depths of Jool. Payloads must be attached/detached using docking ports, not decouplers. No mods or part tweaks other than official DLCs, FAR, aesthetic mods, and piloting or planning assists. Challenge Tiers: Tier 0: "Proof of Concept" (Normal): Build a prop/rotor SSTO that makes it to Kerbin orbit. Must be capable of takeoff/landing in Kerbin’s atmosphere on rotor/prop power alone. Example: Reddit user u/chargan’s Orbital Chopper Tier 1: "Practical Problems, Sober Solutions" (Hard): Fly your prop/rotor SSTO to Duna's surface and back. Must be capable of takeoff/landing in Duna’s atmosphere on rotor/prop power alone. The challenge is simple in concept, but hard in practice. But, if you manage to accomplish Duna, there are other destinations to try, where almost no SSTO crafts have ever gone before... Bonus Badges: Within each tier, entries can receive the following awards. Ordered roughly by importance in career mode. (ISRU comes last as you are strongly encouraged to use it.) V: Heaviest payload delivered IV: Greatest tourist capacity (No chairs - tourists can’t go on EVA) III: Cheapest craft II: Lightest craft (Wet mass, excluding payload mass) I: No ISRU (Multiple entries can earn this.) Leaderboard: Good luck! If you have any trouble completing the challenge, browse this thread or just ask for help—there are many posts here with tips and links and instructions.

That's a really cool concept, although the floating control surfaces make takeoff look like witchcraft. Do the surfaces need to be offset that far? Otherwise the rotors/autorotation are great. I'll add it to the list, witchcraft isn't against the rules .

In light of AHTech's press statements, Periapsis Co. would like to remind all builders that auto-strutting to the root part is "not to be trusted" when docking vessels. Consider auto-strutting to the heaviest part, or better yet, the grandparent part. Sorry I had to roleplay lol.

Yeah, the mun's equator is pretty good, although Bob did some math recently - inclined canyons aren't an issue . Obviously many bodies like the Mun don't have a large enough SOI to allow a synchronous orbit, but I can set things up so that after 8 orbits (for example) I'll be over the same canyon. Don't forget to raise your periapsis after the canyon pass lol. To be specific, make the time it takes to orbit (the game calculates it for you) divide nicely into the time it takes for the area (a canyon) to rotate once. The only tricky part is figuring out how long it takes for the planet to rotate at higher latitudes. I used a few sites to help me calculate this, if anyone's interested, let me know.

What planet/moon has the deepest canyons? I'd prefer a planet with no atmosphere, so I can do orbital flybys at very low altitude. Obviously I'd prefer a planet without an atmosphere. I'm thinking Dres' canyon might be an easy place to start, but what about Moho, Eeloo, or Jool's moons? Tylo's strong gravity would make for a very fast white-knuckle flyby, but does it have any canyons?

Of course, that mod is a stage recovery mod, which is allowed. Wow! Congrats on completing the challenge! I'll add you to the list of challenge winners.

Just some food for thought: This isn't my design, but this design (before stock props) is VERY light for a stock Eve SSTO. Pardon the music, not my video. Maybe a reusable Eve shuttle isn't so far-fetched after all? I tried it myself and it does work, although it's very picky with takeoff/ascent profiles.

Well, err... I, uhhh In all seriousness I have a return vehicle, but it only works once, for one kerbal. The landers are currently more expensive than the kerbals. For the purpose of this challenge, you can pretend you already have a orbital and ground-based refueling station. You don't have to manually refuel your craft if you don't want to, since it's already pretty time-consuming designing a reusable eve lander anyway.