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  1. I'm thinking about diving deeper into the ion engines of KSP. Not only can I understand them better for KSP fanworks, in which the engine math would be described in great detail, but I can apply these principles for real-life. As a KSP example, the given values of the IX-6315 "Dawn" engine are: Isp = 4200 s Thrust = 2 kN Which is way higher than the real-life ion engines I've been seeing. Values I can easily calculate are: Mass flow rate for xenon propellant (kg/s) Exhaust velocity (m/s) Beam power (watts) Wet-to-dry mass ratios for certain dV requirements For certain phases, some parts will be jettisoned (e.g. I'm not going to carry an Apollo-style landing craft back home if I've already used it). Using this engine as an example, how do I calculate the specific power (W/kg) for it? With that value, I can divide it by the input power to get the mass of the power supply system required. Example: an engine with an Isp=2000s and a Thrust = 0.2 N. A value of 100 W/kg was given for the specific power, but I have no idea how they got it. mass of power supply system = (Power required in W) / (specific power in W/kg) This might not matter so much in KSP, but it does for real-life calculations. Plus, as an aerospace engineering major, I want to better understand what goes into xenon-powered spacecraft. If someone could help me, that would be nice.
  2. It turns out that the large ion array on my WIP Jool5 mothership needs an obscene amount of power, at least relative to stock KSP. We're looking at 24 Dawns consuming a total of 216ec/s at full tilt. Solar obviously isn't an option because the inverse square law is a thing, and since I'm limited to stock parts I can't just slap on a NearFuture fission reactor and call it a day. Currently, I'm considering clipping a ring of 12 RTGs to each Dawn, which should provide enough power to run them all at max throttle. The problem is that the total mass of all these RTGs will be about 24 tons - not huge relative to the rest of the ship, and the Dawns have the ISP to burn, but every ton counts when your TWR is almost non-existent. The alternative is using fuel cell arrays. Each array can pump out enough juice to run two drives, so only about 3 tons would be added in total. But, they consume LFO, slashing the effective ISP of the Dawns from 4200 to 1300ish, and that's before the TWR impacts of all the fuel I'd have to carry with me. So... I'd like to get y'alls opinion. Which one is the better solution for a large ship? Or is there a third option I haven't even considered?
  3. I can mine fuel and mono-propellant, but are there anyway I can mine or get Xenon from space? is there any mod? My ion crew transporter is out of Xenon gas and it's suck in kerbol orbit.
  4. The ion engine uses Xenon as a propellant. What changes do I need to make in the cfg file so that the engine could run on either Xenon or Argon?
  5. I saw this video by Scott Manley where he went over an ion engine that collects air from the upper atmosphere and uses it as fuel to stay in orbit. I think this could have some rather... interesting uses in KSP. Things such as ICBMs and crafts for traveling to and from a planet's moons. It would also be cool if we could store some of the gas in tanks for use in orbit. Here's the video -
  6. After recently sending a probe to the Mun, I have came across some issues regarding the Ion Engine, but rather than list everything bad about it, I've decided to turn this into a conversation. What are your pros and cons of the IX-6315 "Dawn"? Please feel free to post your opinions on this topic below! - Mr_Kerbal
  7. The Latest Innovation from Mintech, urking out concepts from the raycast saga. I hope you all enjoy. GAMMA-C CRAFT FILE: Destination folder "Kerbal Space Program\saves\yoursavefile\Ships\SPH" Gamma-C Craft File
  8. The Story So Far: Prior to KSP v1.0, mass ratios of tanks varied wildly. For some fuel types, there was a consistent progression across tank sizes, for others, there was not; and across fuel types, there was no consistency at all. In KSP v1.0, Squad made the decision to standardize all the fuel tanks in KSP to a mass ratio of 9:1 - meaning one ton worth of tankage holds 8 tons worth of propellant. All the fuel tanks...? No! A small holdout yet remains in the northern reaches of Gaul in the form of the xenon tanks. Their mass ratio still sits at 2.2727:1 - meaning one ton of tankage holds just 1.2727 tons of propellant. It's almost a fifty-fifty split between dry mass and xenon! Why It Matters: The rocket equation consists of two parts that are multiplied with each other. One is the effective exhaust velocity, which we know in the derivative form of specific impulse (Isp). The other is the vessel's mass ratio. Therefore, the mass ratio is at least as important as Isp for the performance of a rocket. You can argue that it is even more important, because while Isp only defines the rocket's dV, the mass ratio defines the rocket's dV in the same way as Isp does, and in addition to that, also defines the rocket's TWR. A better mass ratio gives you both more dV and shorter burns. Another consequence of the mass ratio going into the rocket equation lies in the maximum dV any given rocket stage can achieve with a specific engine (more precisely, with that engine's Isp). Because even if you add the entire observable universe's mass in terms of fuel to a rocket that somehow weighs zero kg despite having an engine and other stuff, you could still not exceed the mass ratio of the tanks you are using. Therefore there's a hard limit of dV you can never exceed with any given engine, and it depends entirely on the tank's mass ratio - and the way it curves towards that limit with increasingly diminishing returns depends on it, too. Why It Should Be Addressed: In real life, the mass ratio of a fuel tank depends on a great many factors, including the physical properties of the propellant itself. So you could argument that it is realistic that different fuels have tanks with different mass ratios. However, for xenon specifically, real life tanks are not anywhere near that low. In addition to that, as mentioned above, Squad made the conscious decision to remove all tankage mass ratio differences from the game (except xenon, which as it would appear was forgotten). And there's good reasons for doing this, reasons I've experienced myself multiple times while helping out with the mod Near Future Technologies. One pack in this suite of mods introduces new engines, which run on several different new fuels. I'm doing the balancing of those engines, and over time, I've tried various different approaches. Among them were approaches that had all the fuels at different tankage mass ratios. Although this offered increased freedom in assigning stats and part niches, it also made everything a whole lot more complicated to manage and balance properly. But that's not the main reason it was a bad idea. No, the main reason is that none of the players noticed it. None whatsoever. Not a single person who hadn't followed the dev thread discussion ever admitted to being aware of these differences. And, I mean, why would they? Fuel tanks are just fuel tanks. When you build literally any other spacecraft in KSP, you plop down the payload, you plop down a number of fuel tanks, and then you sit down and start comparing engines for thrust and Isp. Engines, not tanks. So the only thing those players noticed was: some engines just had better stats than others, no matter how you turned it. And these players then came to the mod thread and complained that their favorite engine was underpowered, or that another one was really broken, and that our balancing was super bad. All in all, mucking with tank mass ratios turned out to be unnecessary complexity that didn't add any depth, only confusion. Squad, I wager, knows this full well, for they have a forum full of active users who love to discuss engine balance while equipped with many different variants of half the data. And with the introduction of such things as the monoprop engine, and the move of the LV-N to be liquid fuel only, KSP moved rapidly towards a situation where engines could not be directly compared to each other anymore. So they made LF/Ox, LF-solo and Monoprop tanks all have the same mass ratios. Voila, engines could now be compared again! Except, you know, the often-forgotten Dawn ion engine. What The Actual Effects Are: The Dawn has so wildly different stats from all other engines, both in thrust and Isp, that comparing it to other engines is fairly straightforward on the surface: the dV you get is simply just "higher", and the thrust you get is simply just "lower". It clearly gives the Dawn its niche. However, if you sat down and compared the actual stats, you'd quickly discover that this engine doesn't perform the way you think it does. Namely, it always significantly underperforms compared to what your on-paper math says it should do. And the more fuel you add, the worse it gets. To illustrate, I've done some math on a vessel that is comprised of 10 tons of dry mass, including a Dawn engine. I've added enough fuel to hit several different propellant fraction targets (percentage of vessel mass that is fuel). At each of those targets, I determined how much more dV and TWR the vessel would get if its tank mass ratio was 9:1 instead of 2.2727:1... and then converted that into how much less "effective Isp" and "effective thrust" the Dawn gets compared to a hypothetical LF/Ox engine with the same stats. I also calculated the difference in total mass between the vessel with the LF/Ox tanks and the vessel with the xenon tanks. Spacecraft mass is important when designing your lifter, after all... and that difference is the extra mass you have to lift just because you're using xenon (in addition to being responsible for the drop in effective thrust). Base Stats 4200 s 2.00 kN n/a Propellant Fraction Effective Isp Effective Thrust Vessel Mass Difference 15% 3739 s 1.80 kN 1.38 tons 20% 3564 s 1.73 kN 2.09 tons 25% 3378 s 1.66 kN 3.04 tons 30% 3175 s 1.59 kN 4.36 tons 35% 2952 s 1.53 kN 6.29 tons 40% 2703 s 1.46 kN 9.44 tons 45% 2417 s 1.39 kN 15.45 tons 50% 2072 s 1.33 kN 31.50 tons As you can see, the Dawn effectively drops to barely half the performance a player would infer from looking at its stats alone by the time the propellant fraction hits 50%. This is not the Dawn engine's fault. It's the xenon tank's fault. What I Propose: Simply put, adjust the dry masses of the xenon tanks to fall in line with all the other fuel tanks in KSP. I've even gone ahead and calculated the numbers - you just need to put them into the configs: - PB-X50R: 0.03143 becomes 0.005 - PB-X150: 0.055 becomes 0.00875 - PB-X750: 0.4125 becomes 0.065625 Meanwhile, doing this obviously results in a massive buff to the Dawn engine. But consider the following: because of the poor xenon tanks currently in the game, the Dawn engine needs to have artificially inflated stats (in both thrust and Isp) in order to deliver the performance that it is designed to have in typical usage scenarios. As such, there should be no problem with adjusting those stats down once the tanks are no longer killing it. Since the Dawn engine is a direct nod to the NSTAR ion thrusters on NASA's Dawn spacecraft, currently in orbit of Ceres, why not take the Isp directly from that? Instead of 4200s, it would now have 3120s. Looking at the table above, that falls pretty much straight in the middle of what you effectively get right now anyway, on average... a perfect fit. The thrust could be set at 1.5 kN, a nice round number that's also reasonably near the average effective performance today. 1.6 kN would also be valid, but from my gut, I'd choose the lower value. Xenon-fueled spacecraft are already getting another stealth buff in requiring less lifting power to put them into orbit. In Closing: From my amateur viewpoint, I consider this change to be simple, straightforward and requiring only little testing - it doesn't affect many game systems, and the required changes are so few and simple, a ModuleManager script could do it. I'd love to hear everyone's thoughts and comments on it!
  9. I have noticed that none of the Ion drives that I have seen so far such as the stock "Dawn" or any of the ones from mods like Near Future Propulsion have neutralizers on them. In real life these are essential to the functionality as they ensure that the exhaust gases don't re-enter the engine, canceling out the thrust provided. Modeling-wise it would be easy to implement - just stick a tube on top of the engine that also glows as the engine fires. See pictures This is a very small point but still I think it would add to the realism, which I believe to very much a core value of this game
  10. Version 1: Radial Small Tanks & Rounded Shroud - 4 Nozzles Version 2: Single Large Nozzle Version 3: Cubic Shroud - 4 Nozzles Version 4: Cubic Shroud & Round Magnetic Chamber - 4 Nozzles Version :5 Rounded Shroud & Cubic Shrouds - 4 Nozzles Version 6: Round to Cubic Shroud - 4 Nozzles Version 7: Superstructure & Cubic Shrouds - 4 Nozzles Version 8: Tapered Rounded Shroud & Cubic Shrouds - 12 Nozzles Hello forum people! Please help me decide which of the above engine designs to choose for the new MPD in Kerbodyne Plus V1.1! Please keep in mind that picking a direction should be about the general idea and not about level of detail. The finalized model will receive more detail than even the most detailed sketch presented here. Anyways, thanks to everyone who votes in this poll for helping me decide!
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