SpaceFrog

Please, rotor.02 keeps getting tagged as mod part. I don't know who did it, but it is so annoying! All my stock+ uploads with that part are flagged as having been modded

Thanks you! I'm not that great making videos. But if people struggle to use my craft, I will be releasing a video to show how it's done! :-)

Thanks for the tips, Mk2 part are extremely draggy when placed horizontally, but I discover that the vertical placement reduce the drag by a whole lot. I probably won't swap out any part on this SSTO. One reason is that "if it ain't broken, don't fix it", I also just love the aesthetics of the Mk2+ Mk3 part design. I generally have more fun piloting a craft that looks pretty too, and I am more than willing to accept the tradeoffs that come with using these parts. I get more enjoyment out of the process when I limit my self to only design crafts that are aesthetically pleasing. In the future, If I were to make a SSTO using Mammoth engine to carry ISRU components, I will definitely consider the 3.75 and 1.25 parts.

As many have realized already, sending Kerbals to EVE can easily become a one-way-trip. The high gravity and thick atmosphere present formidable challenges to anyone that wishes to take on the challenge of returning from Eve surface. It requires a staged rocket a stunning 8000dv to even reach the low orbit. So, naturally the question comes to everyone's mind, if SSTO can use Kerbin atmosphere against Kerbin gravity, is there a way to use the EVE atmosphere against its dreaded gravity? As many have already proven, it is possible, but how does one build a craft that accomplishes that and pilot it safely into low orbit? And that is what I will try to explain here. First of all, the Eve Effect. Due to its gravity and atmosphere, even adding the payload by just a tiny bit, the amount of fuel and thrust power increases at a stunning rate. So, when building your first EVE SSTO, most of the weight should come from engines and fuel tanks, anything else should be minimized. One common theme among the Eve SSTO design is that the Kerbonaut is uncomfortably squeezed into a tine service bay with the tiniest probe core alongside a tiny reaction wheel. Another alternative approach to this is the Mk1 cone shaped command pod. It has space for 1 Kerbonaut, capable of storing data, a reaction wheel, and a tiny battery. Be sure to empty out the monopropellant if you choose the Mk1 pod. Weight management and resource management lies at the center of Eve SSTO. The desired result that everything is about just enough for things to function, and the only thing that doesn’t really contribute to the craft’s orbital entry should be the Kerbonauts on board. In order to utilize Eve's atmosphere against its gravity, one must first understand the unique properties of Eve atmosphere. Generally speaking, based on altitude the Eve atmosphere can be divided into 4 parts. Each part has distinct properties which we aim to exploit accordingly. 0m-15000m the thickest of the thickest. High atmospheric pressure renders most rocket engines useless with the exception of KS-25 Vector, Mammoth, and the Aerospike. However, the smarter way is to completely forget about rocket engines. With Breaking Ground DLC installed, using propellers powered by electricity is by far the most efficient way to lift anything from sea level to 15000m. 15000m-40000m the atmosphere is still there, but it is only as thick as Kerbin atmosphere. This means that rocket engines used to lift craft from Kerbin sea level start entering the optimal range. While the usage of propeller starts to require larger and larger wing surface that will generate too much drag later on. 40000m-80000m the atmosphere is even thinner, with a thinner atmosphere, accelerating horizontally would face far less drag. LV-Nerv nuclear engines are starting to become Extremely efficient. Any other rocket engine pales in front of its 800 Isp. 80000m-90000m the atmosphere is almost non-existent. If your AP is above 100000m and your PE is within this range, the atmosphere will barely drag your AP back into the atmosphere. This is almost the equivalent of being in orbit. In the First Phase, electric rotors and propeller blades are used to lift the craft from sea level to an altitude around 15000m. Rotors are best used in pairs; therefore, they can cancel out the torque generated on the craft. Rotors are like engines that don’t consume fuel, even if fuel cells are used to power them, no rocket engine can lift your craft to 15000m consuming less than 1000 units of fuel. They are the key to any Eve SSTO that doesn’t take off from the highest peak. Among all the setups, the R-25 propeller blade and the EM-32 rotor combination is the one that works the best. 8 blades symmetrically attached to the EM-32 rotor provide the best propulsion force while consuming a minimal amount of electricity. Another thing worth noting is that the weight of the rotors can be reduced at the cost of torque. Since we don’t need this craft extremely fast, the rotors can be set to 55-70 percent depending on the total weight of the craft and the wing area. To optimize the propellers, it is crucial to bind the propeller blades to action groups to adjust the pitch angle. Pitch angle slowly goes up throughout most of the first phase. 16-15 degrees is good for takeoff, but a rather poor choice when the craft start to climb higher. If you’ve flown propeller planes very high in the Kerbin atmosphere, you would know that the last 2000m before reaching 15000m can be a long and somewhat annoying process. 15000m is just for reference, for some designs, 14000m is enough for entering the Eve orbit, for designs with larger wings, 16000m is the perfect point switching to rocket engines. This is a tradeoff. Larger wings and more propeller blades can bring the craft higher, but larger wings also generate larger drag. Larger wings and more blades also add to the overall weight. In my case, I picked 14500m as the target altitude for my first phase. As mentioned previously, in order to use propellers, there needs to be electricity. Any part used to generate the needed electricity is a part that provides neither lift nor thrusting power. Therefore, we want to generate just about enough electricity for the electric rotor and other components such as the reaction wheel. Solar panels are a poor choice to use, they have to be attached to the outer surface to generate electricity which adds drag to the craft, and it is usually somewhat cumbersome. Isotope rods can be safely stored away, but in order to generate the amount needed to power the whole craft, a combination of battery and isotope rod has to be used. Usually, upon reaching the 15000m mark, the batteries are almost out of juice. This approach requires one to properly time the rate at which electricity is generated and the rate of consumption so that one doesn't run out of electricity before reaching the target height or add way too much battery which is just extra weight, we do not want spend fuel on. Fuel cells can be a good idea, despite the fact that it consumes liquid fuel and oxidizer, but the amount it consumes is extremely low. In the case of my SSTO, the rate is barely 0.01 per second, It takes me about 11units of oxidizer and 9 units of liquid fuel, and that is negligible in comparison to all the fuel and oxidizer I have on board. However, once the orbit is reached, generating electricity using fuel cells becomes rather wasteful. In conclusion, the best option could be a combination of these methods. Solar panel + fuel cells or isotope rod + fuel cells are both viable paths to provide electricity to your rotors. For wings, the options are rather limited. It must be able to withstand the reentry heating and has a rather large lifting surface relative to its weight. If it doubles as a fuel tank that is an extra perk to it (this will be explained later). This narrows us down to the two wings, both of them are from the Big-S Wing series. (This might seem pretty obvious to anyone who has built an Kerbin SSTO, but I want to make this article as informative as possible so that even beginners can learn too). As for control surfaces, Big-S tail fin is a descent choice, but it is way too big and heavy to be placed vertically. The Big-S Elevon on the other hand is a poor choice if one wishes to place it horizontally simply because it has a smaller wing surface relative to its weight (if you do the math 3.49/0.45=7.76 and 1.16/0.23=5.04, just for reference the Big-S delta wing has a lift to weight ratio of 5/0.5=10). So, for horizontal control surface, you actually want to use the tail fin, and for vertical control surface use the elevon. This conclusion seems counterintuitive indeed, but we cannot afford to have parts not optimized for their purposes. Another option for control surface is Advanced Canard. Despite its poor lift to weight ratio, it is extremely light. With such a thick atmosphere, the control surface doesn't have to be very large. Adv. Canard can serve as the perfect tail fin. (confusing huh? we are using these surfaces with complete disregard of their intended functions implied by their names). The wings not only get us through the entirety of first phase, but wings also play extremely important roles in the second phase. In the Second Phase, the main lifting force will come from wings and rocket engines. However, wings also have their negative effect known as drag, and this problem begins to manifest as the rocket engines accelerate the craft rapidly above Mach 1. The amount of drag generated by wing is directly related to the wings’ angle of incidence and the surface area of the wings. But drag isn’t only generated by the wings, every other part on the SSTO can generate drag too and they don’t even provide any lifting force. So, it is better to have the wings angled rather than having the entire craft forming an angle of attack that generates drag everywhere along the craft body. As for a rule of thumb, 5° is ok to start with, but one really needs a mod, the Precise Editor, to adjust the angle of incidence to make the craft more aerodynamic. This angle can range from 1°-5° with most designs have this number lie around 2°-3°. I set the angle to 3.3°. This is another point where trade-offs are made. Greater angle means that the SSTO has a greater advantage during the first phase of the ascension, and it requires fewer wing parts which reduces the total weight; however, the drag is increased. A lesser angle of incidence has another advantage besides smaller drag. More wings can be a good thing when you need them to function as fuel tanks that generate descent lifting force. Whether the craft is aerodynamically optimal or not directly impact the success of any attempt to enter Eve low orbit. The main body of the craft should point prograde for most of the second phase to reduce drag. Mk2 parts are often regarded as the draggiest parts because their lift generating property comes with extra drag produced as a byproduct. I could not resist the aesthetics of Mk2 parts and placing them vertically would minimize the drag from these parts since they have stopped providing lift. Rotor and propellers must be stored away in cargo bays or service bays to reduce drag after using them to achieve the target altitude and the same goes for any other part that can be stored away. Faring is another option, but anything inside the faring will stay there until the craft is decommissioned. No connection nodes should be left unprotected, even the rocket engines. Using a nose cone to cover up nodes on rocket engines and moving it away from the exhaust vent is an important trick to reduce the drag. The Mammoth engine is an exception because they have one connection node only and that node is already used to connect the engine to the rest of the craft. Lift is the other factor from wings that comes into play. Ideally, there should be just the right amount of lift so that the craft will automatically pitch up when the SAS is set to prograde. The craft needs to accelerate horizontally for a while for this process to happen. Since this horizontal acceleration happens when the atmosphere is still rather thick (around 15000m) the shorter it is the better. A low thrust to weight ratio would extend this process unnecessarily long, making it very inefficient. But the craft also shouldn’t pitch too steeply. A steep ascension would mean that the engines are doing the bulk of the work. In order for wings to contribute sufficiently to this process, this automatic pitching process should not exceed 35° with 30° as an optimal upper bound. On one hand, a very steep angle also means that the craft is not accelerating sufficiently in the horizontal direction. On the other hand, a very shallow angle means that the SSTO has to combat the drag for a longer period. Once again, this is about trade-offs, and one has to weigh the various factors at play carefully. If the TWR is on the higher end, a steep ascension is perfectly fine, with a lower TWR, it is best to let the wings do more of that lifting. A greater wing pitch angle and a faster acceleration process will send the SSTO into a very steep climb. On the contrary, a lesser wing pitch angle and a slower acceleration will keep the craft in the dense atmosphere for a prolonged period. Thus, the wing pitch angle needs to be carefully adjusted according to the TWR of the engine. Speaking of the TWR and the engines, their importance is second only to the aerodynamic features of your Eve SSTO. The smaller and lighter crafts often use the Aerospike. Medium sized crafts use Vectors or a combination of Aerospike and Vector to accomplish the same thing. Vector is more efficient when the atmosphere is denser, but the Aerospike outperforms against the Vector in fuel efficiency when the atmosphere is thinner. Their complementary qualities can be something very desirable when used simultaneously to power the craft. Mammoth is reserved for heavy or super heavy Eve SSTOs, rarely are they used in combination with the Aerospikes. One of the first Eve SSTO ever has been powered by those monstrous rocket engines. Designs utilizing Mammoth often have ISRU capabilities built-in to the SSTO. Both Mammoth and Vector has gimble capacities, this could come in handy since most Eve SSTO only has minimal reaction wheels installed. Most SSTO also need LV-Nerv to enter the orbit. Even though the thrust of LV-Nerv is among the lowest in game, its specific impulse exceeds the ISP of other engines by a long shot. Few Eve SSTO can achieve a dv around 5000 without using nuclear engines, and the one that fly without the nuclear engines are often equipped with the alternative option which is the Dawn ion thruster. Xenon, however, is not a resource that can be generated through ISRU means. Thus, by using Dawn the SSTO becomes more of a non-reusable craft. I personally think that this design is inherently in contradiction with the idea of using SSTO in the first place. In my case, I choose the combination of Vector, Aerospike, and Nerv to obtain a total vacuum dv of 5000. The nuclear stage should never have more than 2000dv. Due to the low TWR of Nerv, it cannot burn that much fuel fast enough to complete the maneuver required to enter low Eve orbit. While in the second phase, the nuclear engine is still not optimal, but one should start the Nervs around 16000m. During this phase, it provides a small but, eventually, crucial amount of acceleration that will eventually send the SSTO into orbit. One cannot simply add fuel to the craft to increase the dv of the stages. There is a point when the TWR of the main stage is simply too low to accomplish anything. The greater the TWR, the faster craft accelerates, and the shorter the amount of time is spent on combating gravity. Once again drag comes into play. If accelerates rapidly, the craft would have to combat extra drag. The lowest TWR around 15000m that I have seen is around 0.40, the highest I have seen is around 0.90, and my SSTO has a TWR of 0.60 at 15000m. The TWR essentially determines how the ascension profile should be tailored to maximize efficiency. After discussing the wings and engines, I can finally go back to the “automatic pitching” process. The lifting force obviously comes from the wings, but there is more to it. The center of the lift and the center of the mass should be extremely close, a lot closer than any other aircraft intended to fly on Kerbin. Throughout the process, the relative position of these centers should stay roughly constant. This can be accomplished through simply balancing the fuel or using a more sophisticated fuel flow priority to establish sequence where the center of mass is unaffected by the burning of the fuel during the second and the bulk of the third stage. Initially, the craft has a positive angle of attack upon entering the second phase. The engine accelerates the craft so that the lift is great enough to initiate this process. By switching to prograde when the angle of attack is 0°, the craft would experience minimal amount of drag during this process. If this ascension were to be done in a manual manner, the drag generated in this process would make the SSTO highly improbable to enter the low Eve orbit. As the atmosphere starts to thin out, the craft will eventually lose the lifting force provided by the wings. This is what causes the craft to pitch down in the process. As soon as the thicker parts of the atmosphere are no longer affecting the craft, the angle should slowly go down, allowing the craft to spend more fuel accelerating horizontally. Thus, we arrive at the Third Phase. At this point, the SSTO has successfully managed to get out of Eve’s thicker parts of the atmosphere. The goal is to accelerate horizontally achieving a target apoapsis height and a target orbital velocity before the main engines shut off due to the lack of oxidizer. I have personally established a few checkpoints to guarantee my ascension path. This is slightly different for every SSTO. Here are my checkpoints. 30° at 30000m, 25° at 40000m, 20° at 50000m, and eventually 15° at 60000m. Depending on the SSTO, this process might or might not happen automatically, but since the drag is getting smaller and smaller, switching to manual pitching wouldn’t create a whole lot of drag either. Feel free to adopt my checkpoints to begin with, and slowly adjust them through trial and error. The main engines should shut off halfway through the third phase. Usually at this point it becomes very clear whether the SSTO has the potential of making it to orbit. There are some parameters that might help. Ideally, when the main stage is done burning, the craft should have an orbital speed greater than 2400m/s and an AP of at least 80000m. If the orbital speed is not high enough, the nuclear stage will not have the time to complete the burn and accelerate into a semi-stable orbit. If the AP point isn’t high enough, the nuclear engines can’t raise the AP high enough so that dense air wouldn’t slow it down preventing it from entering a semi-stable low eve orbit. For the rest of the third phase, a common mistake is to raise the AP above the atmosphere and starting to make a maneuver node. Rather, click to show the in-game orbital info, and keep focusing on the PE and AP numbers. Since the Nuclear stage often has a low TWR, it is important to buy as much time as possible. Raise the AP point and make sure that there is plenty of time to accelerate during the fourth phase. The trick is to keep a positive angle of attack. I usually just leave the direction of the craft unchanged after I reach the 60000m checkpoint. The Final Phase. This is the last phase to enter the low Eve orbit. Unlike other crafts, Eve SSTOs have a unique way of entering stable orbit due to the extremely low TWR of Nerv nuclear engines. As mentioned before, don’t bother setting up a maneuver node. If the AP is around 100000m, it is usually a very good sign. This indicates that it is very possible to complete the entry into orbit in one burn. Even if that is not the case, there is still a chance for a semi-stable orbit. A semi-stable orbit in the case of Eve has an AP above 90000m and a PE between 80000m-90000m. However, there is no guarantee that an orbit that satisfies these conditions will be semi-stable. A semi-stable orbit allows the SSTO to pass through the PE and re-exit the atmosphere. By burning again at the AP point, the PE can be raised above 90000m. So, do not give up just yet if the PE isn’t high enough, there is always a chance. For the entirety of the final phase, keep a positive angle of attack. There is no definitive number as to how high the angle should be. In the most extreme cases, the AoA can be around 75° or even 85° towards the end of the burn. It is all about raising the AP and prolong the time to reach AP. The longer the craft stays above 85000m, the better. Nuclear engines should have plenty of dv at their disposal, all it needs is just a little more time to complete the burn. Quick save the game and practice a few times.

I finished making my EVE SSTO. I have never been so exhilarated since I started playing KSP. Download link if anyone needs it https://kerbalx.com/DLQ3987/EVE-SSTO-Akatsuki-with-tutorial

Many has regarded EVE as a formidable enemy due to its dreaded gravity and suffocating thick atmosphere. With Breaking Ground DLC, the propellers have made an SSTO to low EVE orbit possible. I have decided to take this challenge face on over the Thanksgiving break! And, behold, the EVE SSTO AKATSUKI Download link https://kerbalx.com/DLQ3987/EVE-SSTO-Akatsuki-with-tutorial Sorry about the interface which is in my native language, but I'm sure that most of the stuff is pretty self-explanatory. I was told that EVE SSTOs are ugly because they have to optimize according to how the game calculates drag and lift. After days of grinding, I have proven them all wrong! No need to squeeze Kerbonauts inside tiny service bays, no need to awkwardly stacking wings, no need to suffer the eye sore of an ugly craft. I named this SSTO after the fabled Akatsuki lake on EVE. Few have found the Akatsuki lake biome and even fewer people has made an EVE SSTO. I am willing to share all the necessary details about how I made this craft if anyone else wishes to take on the same challenge. Feel free to ask me about anything.

Thanks everyone! I made it! After days of engineering and fine-tuning, I present you all the Akatsuki! https://kerbalx.com/DLQ3987/EVE-SSTO-Akatsuki-with-tutorial

the side view should clear the doubt on that! none of them are actually horizontal hahaha

Update on current progress

currently sitting at a total dv of 4200dv. with the new angled wing design, reaching 90km is fairly easy. But the trajectory is still not optimal, I often end up needing another extra 800dv to circularize.

Great insight, but the thing with EVE atmosphere and gravity is any attempt trying to add more dv makes the ship size grow exponentially. But I do feel that nuclear engines would help greatly toward the end of the burn.

Already doing the reverse cone thing to cover up the connection node! :-) I also put one on the vector, you can kinda see the edge pooping out of the vector engine. I think you are right about the mk2 parts. I went into debug mode, and they are the draggiest parts on this design, so they are definitely getting swapped out! I just had to try them, they are the most elegant parts in game, but I get is comes with a cost using them. I shall consider a different approach then possibly the all mk3 approach!

I have been working on this EVE SSTO for a couple of days. Exploring how aerodynamics work in EVE atmosphere has been a lot of trial and errors. So far, I can get to 12km above sea level using propellers, and from there I switch to the rocket engines. The best I got is about 77km (AP). I have successfully built several SSTOs for Kerbin and Laythe, but EVE is just on a completely different difficulty level. How can I perfect this prototype into an actual EVE SSTO? More dv? Alternative engine setup? Aerodynamics? Better gravity turn? Drag seems to be a major problem the mk2 cargo bay can generate a lot of drag, but switching to service bay also generate quite the amount of drag too. (Don't worry about the change in the center of mass, I have altered how fuel gets drained from each parts. The center of mass doesn't change until the last fuel tank starts draining.) Nov 28 Update: I done did it! Thanks to all your tips, I made it to the low Eve orbit. Scroll down to see the pics and download link

I have found the same thing! In the game if you use 5 Kodiak and 4 Cub vernier (which the Soyuz has) you can deliver much more than just a couple of satellites to LKO. However, just to be fair, the Reliant is cheaper and is more powerful than Kodiak is many ways. So, further nerfing of the Kodiak would render it almost useless by comparison to the Reliant.

If anyone needs localization in Chinese, here it is! 中文本地化内容 [Moderator added translation] Chinese localized content