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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.

Before Reading I'd recommend that you'd watch Bradley Whistance's video on his stock prop speed test. The method he outlines is not relevant to the actual math work, and simply affects the values I will be plugging in. https://www.youtube.com/watch?v=J7oc1FLnWlY&t=438s I will only discuss the resulting data in this thread to keep things simple, if you have specific questions about the math, let me know. With that out of the way, let me preface this discussion. The dominant method of powering stock props is by using RTGs, which makes sense. They continuously generate power, allowing stock props to run forever, this is great for Duna, Eve, and Laythe exploration. However, I commonly see this used on props built for fighter craft, transport aircraft, and others. While there are some cases where endless flight is desirable on Kerbin, such applications certainly do not qualify. Most people don't fly a single stock prop fighter for hours on end (without crashing). This leads to the question, are RTGs the most efficient way of powering these props? Short answer, no, but I'll explain in more detail. I am taking efficiency to mean weight in this conversation, although other uses of the term, such as part count, may also be referenced. First we must establish all of the possible methods of powering a stock prop: RTGs (duh), batteries, and fuel cells. RTGs we already discussed. Batteries would simply run the engine using their stored electric charge, and the flight would end once they run out. Fuel cells would burn LFO (Liquid Fuel + Oxidizer), continuously generating the engines power needs whilst draining LFO from on board tanks. Of course, I wouldn't even consider the fuel cells to be an option unless I had a good reason. Doing some simple math, we can find that all batteries hold 20,000 units of electric charge per tonne. How much electric charge, then, is LFO equivalent to per tonne? It depends on which of the fuel cells you are using, but for the small fuel cells this comes out to 79,934 units of electric charge per tonne of LFO, and for the large fuel cells it is 81000 units per tonne. Looking at the raw data, fuel cells are the obvious winner. However, the additional weight associated with fuel cells throws a wrench into the works, and in either case this tells us nothing about how RTGs stack up. So I will analyze these three choices in an applied setting, where I will test their mettle in a hypothetical prop that utilizes 10 of the 1.25 meter reaction wheels with 2 dumpling fuel tanks used as bearings. I did these calculations presuming that this engine would also utilize the trick described and demonstrated by Bradley Whistance's video. Using this method the reaction wheels consume roughly 2.73 times their normal power (according to my own testing), I'm using ball park numbers so any small discrepancy is irrelevant. RTGS: The 10 reaction wheels consume 13.65 units of electric charge per second, as such the engine would normally require 19 RTGs to run continuously, which themselves would weigh 1.52 tonnes. BATTERIES: To run this engine for 1 hour you would need 49,140 units of electric charge. This would require 2.457 tonnes of batteries, so those certainly aren't the best solution, although using the largest battery bank available, this would only require 13 batteries. Since the weight of the batteries required scales directly with time of flight, they are likely the most efficient in very short flights. FUEL CELLS: The smaller fuel cells generate 79,934 units of electric charge per tonne of LFO, meaning only .615 tonnes of LFO is required to run the engine for 1 hour. This amount of LFO is almost perfectly held by the 2 dumplings in the bearing, plus two oscar tanks which altogether hold .62 tonnes of LFO. In total the tanks would weigh .698 tonnes (including dead weight), and this engine would require 10 of the small fuel cells to run continuously. This adds another .5 tonnes to the total weight, bringing it up to 1.198 tonnes. As well as 14 parts, but really that's 12 since the dumplings have to be there regardless. In every possible way, the fuel cells are more efficient, while the use of dumpling bearings may seem to bias the fuel cells, in reality this does not affect the weight, and only affects part count. Using a different bearing type would only add 1 additional part, making it on par with batteries and superior to RTGs. None the less, it is far superior to both in terms of weight. This leads me to conclude that Fuel cells are the superior method for powering stockprops intended for short to medium flight times. It should also be added that it is of course possible to mix these methods together. In this one instance, it is actually beneficial. While 10 fuel cells are required to meet the continuous power generation needs, this is only by a small amount, the raw value is 9.1 fuel cells. This adds the equivalent of 540 additional electric charge generation required over the hour of flight. Since fuel cells come with 50 units of electric charge storage each, this means that 9 of them would have 450 units total, leaving us 90 units short. These 90 units can be accounted for with a single of the smallest battery pack (which has 100 units). Weighing in at a mere .005 tonnes, this change leaves us with the original part count of 12 and a reduced mass of 1.153 tonnes. So yes, it is possible that adding batteries will lead to a net increase in efficiency, however, the instance described above is the only type of scenario where this is actually the case. So limited is this possibility that even if the real value turned out to be just 9.3 instead of 9.1, then using batteries would result in a net increase in weight. Again, these results may be different for engines of differing sizes. however I can only see fuel cells being knocked from their throne with very different total flight times. For instance, short flight times where batteries' ability to instantly deliver power gives them a major advantage, and long flight times where RTGs' endless power generation eventually overcomes their initial mass costs. This may be obvious already, but just to clarify, the fact that the math above uses reaction wheels affected by Bradley Whistance's technique IN NO WAY affects the actual math or conclusions. The math above is roughly equivalent to if you had simply used 27 reaction wheels functioning under normal conditions. The objective of this thread was to demonstrate that fuel cell powered props are a lighter and more part efficient approach to powering certain stockprops. While it took a decent amount of complex work to arrive at this conclusion, in actual application fuel cell powered props are no more difficult to build or use then RTG props. There's also the small fact that a fuel cell powered prop will not only start out lighter than a RTG powered prop, but it will also get even lighter as LFO is drained throughout the flight, further increasing performance. I appreciate any questions or feedback you may have. If I made any mistakes, please let me know, and I would love to hear your thoughts on the topic. @klond I think this may interest you.

This is a stock 1:1 scale replica of the Pratt & Whitney R-4360 Wasp Major propeller engine. This engine utilizes 40 1.25 meter reaction wheels and produces a modest 230 kN of thrust. The bearing is very strong, and the engine is extremely smooth when operating. Its root-part is a large girder, allowing it to be easily attached to another craft. It should be noted that the thrust value mentioned is when the blades are set to maximize stationary thrust. Download Link: https://kerbalx.com/Kronus_Aerospace/Kronus-R-4360-Propeller-Engine Part Count: 94 (93 without decoupler) Mass: 11.42 tonnes

Yes you read that right, no i don't want to install firespitter. it would be nice to go a bit before the era of jets in ksp, i mean they had rockets in ww2 so it's not something completely stupid i'm saying. I just would like to see vanilla prop engines so we could recreate even more ww2 craft or make a douglas passenger plane. squad senpai please notice this

Hello, im recently working on stock propplanes. Im wondering if there is any way to messure the speed with that a vessel rotates, so i can compare different designs. would be nice if somebody has an anwser.