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    Curious George

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  1. No, I don't think so. I agree things are hazy, but I think definitions can be handy, even hard ones to come up with. The "mass being within the heaviest body or not" (used by IAU) is a very fine line to draw. So is "A twice as massive as B". I'm fine with both really. 1/25 is not random, it corresponds to the point beyond which Lagrange points 4 and 5 become unstable. Since the matter is the trajectory of bodies, my slight preference would go to any criteria which has a bearing with gravitiy. 1/25 has, 1/2 and center of mass within heavy body haven't (the gravity field of nearly spherical objects only depends on their mass, not their size/density), hence 1/25 has my slight preference. If you can come with an other number related with gravity fields and behavior, it would have my preference as well. I'd rather have a line drawn than none, but I could tolerate hearing that the Earth and the ISS orbit each other, or that the Sun and the Tesla car orbit each other.
  2. Near the end : In a sense, A and B are always orbiting each other, but looking at the frame of reference centered at their mass barycenter, it makes sense and is more descriptive to say B orbits A when B is massless, and say that A and B orbit each other when they are the same mass. Where should we go from one to the other is up to debate, but some value, such as 1/25, make sense.
  3. Do we really have to put a mass at a pseudo SOI to fake Lagrange points? We do know closed form solutions (solutions with a formula, which require less or no integration) for a lot more problems than the 1/R² 2-bodies problems, isn't there one of them that would be more suitable ? That would better approximate what happens in the vicinity of Lagrange point ? At least better than 1/R^2 ? I haven't looked closely at the question, but what first comes to mind is a first order approximation of both body influence. I might be overly optimistic as it likely does not have any closed solutions, but if they do, first it could allow to have not only Lagrange points but also halo orbits (and to not have orbits we're not supposed to have), and second, it might be a strict step up from patched conics realistically speaking, which is less clear with a fake mass.
  4. Expanding on Luna's DMP and ideas read here and there, there could be 2 kinds of multiplayer modes. The first one assume players collaborate with each other, and that space is big so that 2 craft never cross path at random, and it takes both craft to agree to meet for a meeting to take place. There is a minimum time and a maximum time. Each craft has a time attached to it, in addition to its position and velocity. This time corresponds to the last time this vessel was interacted with. It can only go up. When launching a new craft, a player also chooses when it is launched (no sooner than minimum time). It can be done through timewarp from the KSC, including negative timewarps. When flying a craft, its time advances so as to reflect the time you are flying it in. When leaving a craft, its time freezes. When taking control of an existing craft, you can choose when you take control of it (but no sooner than the time of the craft). You are seeing other on-rail* crafts where they are supposed to be at the time of flight : a craft with a time inferior to your flight time is in your past, its future position can be predicted and plotted as a predicted ghost*; a craft with a time superior to your time-flight has its trajectory already determined, and can be shown as history ghost (ghost that can no longer be interacted with) l as long as the trajectory has been saved, which can be done by saving only change of SOI, and state at the end of each flight*. Future crafts that were on-flight during your flight are not shown, or in a special way, which does not need to save the actual flight portion (eg an interpolation between start of flight and end of flight). Such craft are shown on the map, but can also be shown in real, optional (in any case, they are on rail and physically transparent). You can coordinate 2 or more crafts to be in your flight time. Necessary for rendez-vous and docking. It also loads them and starts calculating physics on them regardless of distance. Once you uncoordinate them or end the flight session, their time freeze much like with one craft. Funds expense and revenue, Science recovery, reputation, building upgrade, kerbonauts recruitment, ... are all discrete events which are easy to store with the time they occurred at. Some care has to be given to ensure a present expense does not lead to a future deficit due to a future expense, but there is nothing algorithmically expensive or difficult in that. Optionally, minimum time advances slowly, or faster according to a master warp. The advance of minimum times allows to forget past events and lighten the memory. Then there is ownership and right management to know who is able to do what, but it is the lesser issue. This system might also be used in single player to play through missions sequentially but have them happen in parallel. As far as I know, there are no edge cases. The difficulties come from UI (asking time every time a player wants to switch craft and more), determinism and memory. Determinism issue are denoted with a star : *in order to have an accurate prediction, all the mechanics involved have to be deterministic. Gravity under Newtonian mechanics is very much deterministic, and even time reversible, which should greatly help, but it is not necessarily easy to make practical implementations of it which keep these nice properties. At worse, you could save the whole trajectory of a craft from minimum time to maximum time so as to only ever compute it once, and be able to remain consistent, deterministic. Storing trajectories over year might also create memory issues. Under patched conics, you mostly only need to know the position upon changing SOIs, which should be manageable (mostly because you still need to be careful about precision and determinism in the way you reconstruct the trajectory from a single point). But if you want anything more than patched conics, problems start arising... And KSP2 has already promised binary stars and planets, so they might do away with patched conics. To explain with an example, let's look at 2 potential paradoxes that can arise with asynchronous multiplayer. First example, two players, A and B, want to grab the same asteroid. A makes a quick and dirty maneuver, time warp and grab the asteroid. B plan an interception which should occur sooner than A's. What happen? Answer : A "wins", B cannot interact with the asteroid. As soon as A coordinates the meteorites time with his own, B sees it as a history ghost. If he was already targeting it, he gets a message. Workaround? This is not really an issue with the system itself, as players are supposed to be cooperating, but limitations on who is able to change the time of neutral object can help. Second example : two players, A and B, doing unrelated missions. 10 years in the future, A grabs fuel at a station depot to go to Eve. 1 year in the future, B tries to get fuel from the same station depot. What happens? Answer, B cannot access the station 1 year in the future as the station's time is 10 years after A interacts with it. Workaround? This example shows the limit of this model : commonplaces (stations and colonies) cannot easily be shared, and the order in which players interact with them heavily influences what is possible to do. B is rightfully frustrated because he could have taken the fuel from the station and refuel it before A even needs it. As it happens, there is a workaround for this particular example, but it requires not only cooperation, but also that the players know what they are doing (and even then, they are limited): Instead of docking directly to the station, A can detach a tanker from the station in the present, and dock with it 10 years in the future. In turn, B can send a new tanker to the station in the present (right after A interacted with it) and use it 1 year later. It is not entirely perfect as B might have wanted to first take fuel then send a tanker, but at this point, it is a matter of cooperation : A should have refueled the station.
  5. The big grip I have with the IAU's definition of a planet is that it is a dynamical one. By contrast, a black Hole is a black hole as long s it's smaller than its Schwarzchild's radius A star is a star grosso modo as long as it can sustain fusion. Now one might argue there is something in the etymology or connotation of "planet" which, like satellite or moon, suggest a planet depends on a Star, and even propose an other term for a celestial body that is rounded, but not a star. Term such as Planemo, or the very common but very weird "planetary-mass object" ; "-So you're saying there is a range of mass which define planets? -Yes, but also... no.". And still, the IAU has inconsistency like "rogue Planets", which are planemo not orbiting any star. Now for the definition of orbit, instead of trying to impose a vision and then search for convoluted arguments and twisted definitions to fit it, I think everybody should take a step back and have a look at the most simplistic, indisputable example : A universe with only 2 point-like objects, A and B. A is massive, B is mass less. Then it can be shown that B follows a conical trajectory in the (inertial) frame where A is immobile. In particular, if (and only if) B have not enough energy to escape, its trajectory will be bounded, periodic, and will follow an ellipse. We can all agree to say that B orbits A. In my opinion, a practical approach to enlarge the definition of an orbit is to quantify how much reality differs from the ideal model. In particular, are A and B close enough to be considered isolated? And Is B light enough to be considered mass-less? That's why I don't like K^2's tug-of-war dynamical definition of a planet/orbit. First, it takes no account of the proximity or discrepancy of size (though it could as per my previous post). Second, and most importantly, the absolute value of the Sun attraction plays no role in influencing a system in a way that would invalidate the isolation approximation. To answer "are A and B close enough to be considered isolated from a third body C?", it seems more relevant to compare the magnitude of the forces between A and B to the variation of forces C exerts on the whole system. C might exert twenty Gajilions gs on A and B, if the acceleration of C is the same within the whole A-B system, the frame accelerated by C is as good as inertial, in other word, C makes no difference in the motion of A relative to B. For the example of is Earth-Moon relevant as a system? and how much is it influence by the Sun, it makes a lot more sense to consider the gradient of Sun's attraction, rather than the absolute force. So we should compare: G MEM/REM2 , the force of A and B exert on each other, where MEM=ME+MM the mass of the system Earth-Moon and REM is the highest possible distance between Earth and Moon to be conservative, so the Moon's Apogee, center to center. with : G (2MS/RSE3).DEM where MC is the mass of the Sun, RSE is the Sun Earth distance (in the worse case, so at perihelion) so that (2MS/RSE3) is the typical amplitude of the gradient of the Sun's attraction, to be multiplied by the diameter of the Earth-Moon system DEM. Which gives G MEM/REM2 = 6.674*10^-11 * (5.9724 + 0.07346)*10^24 / (4.067*10^8)^2 = 2.4 * 10-3 m.s-2 as already computed by K2 here (they find 3 likely because they take the average Moon Earth Distance) and G (2MS/RSE3).DEM = 4 * 6.674*10^-11 * 1,989*10^30 / (1.471*10^11)^3 * 3.84*10^8 = 6.4 * 10-5 m.s-2 In other words, the attraction of the Earth over the Moon* is at any time at least 37.5 times bigger than the biggest variation in of the Sun's attraction over a revolution of the Moon around the Earth (or 75 times higher than the tidal Forces of the Sun at any given time). Such a high ratio tends to show that "Earth and Moon orbit their barycenter of mass, which in turns orbits the Sun" is a valid and more accurate description than "Earth and Moon both Orbit the Sun". Btw, this criteria does not depend on the size of the bodies, just their mass. We can use similar reasoning to say that the Earth does not orbit Jupiter. This time, take them at their closest. Look at their mutual attraction force. Compare with the variation of the Sun force (eg Sun force exerted over Earth minus forces exerted over Jupiter). As computed by K2, the Sun exerts an acceleration of a =6 . 10-3 m.s-2 over the Earth. Jupiter is about 5 times further away from the Sun, so the Sun exert on It an acceleration of a/25. At their closest, Jupiter and Earth are 4 AU apart. Jupiter is about 1000 times less massive than the Sun. So the attraction of Jupiter over Earth is a/16000 So we are comparing a relative acceleration of 24/25 a caused by the Sun to a Jovian acceleration of a/16000. We can safely say that the Earth does not orbit Jupiter. Now as to whether we can say that the Moon orbit the Earth, I think the second question, "is B light enough to be considered mass-less?" is the most relevant to the matter. For example, if B's Hill sphere is smaller than B itself, B will have negligible gravitational effect. For example, an astronaut cannot orbit the space station as the Astronaut's Hill's sphere would be 120cm. In particular, such objects are necessarily held together by a force other than gravity. When B is heavier than 4% of A's mass, L4 and L5 are no longer stable. So that could be a sensible limit between considering one body clearly orbit the other and a pair of bodies orbiting each other, as the simplified 3 body mechanics resulting by adding a third mass-less point (eg. a spacecraft) start to really differ. For reference the Moon is 1.23% the Mass of the Earth. By the way, I don't know whether KSP2 will stick to patched conics, I doubt they would if they are introducing a bunch of pairs of bodies, but these kind of questions can directly translate into practical choices of modeling. If A and B are isolated enough, one can assume 2 body mechanics and put A and B on rails around their barycenter. If B is smaller than its hill's sphere, one can consider it mas-sless, for the purpose of interaction with player's craft. If B is small enough, B can be on rails around A and A can be the barycenter instead of orbiting around it. If B is big enough, some 3 body mechanics might be needed in some regions; some of these 3 body mechanics might be split into 2 cases depending on the value of the mass ratio compared to 25.
  6. Well, the mass of the candidate planet does factor. So you could do the computation for both, and call the pair planet and moon if only the most massive passes, planets pair if both pass, and proto-planet or planetoid pair or whatever if neither passes (proto Earth and Theia probably were like that once, both orbiting the Sun but not so close to each other).
  7. Can't this be handle with good balancing? Or is there an inherent flaw with a recovery system? For example if we assume you recover resource and funds for the empty craft, what would you say about 100% recovery within 2 km, then 1% less every 2km further away, as the preset of default difficulty, fully customizable, with strategies influencing it? Also, unless I missed something, you are the first one to actually look at a concrete example for recovery. And that makes me realize the question : "what should be the cost of an imperfect landing?" hasn't been raised yet. It could be a fraction of its cargo, like in your example, but it could also be funds, or work-time of a colony building. I don't like the % of the cargo approach, probably for the same reason as you : you spend a whole lot of effort to go through the solar system, and the whole mission performance rely only its very end (also, missions that are not about cargo don't care about precision). IMO, one thing the recovery should strive to achieve, is to allow to manually deliver, automatic recover, and flying the ship again from the colony, refilled and possibly with another cargo. Which means if colony recovery make the ship disappear and grants fund, I expect to be able to spend funds to build ship on colonies. All in all, the recovery cost/benefits I would like the most would be the following : spend a small amount of funds or building work-time (eg a big rover hangar) proportional to weight and distance to teleport (possibly with a small delay) the craft to (one of) the colony launch pad(s), from which you can interact with its resource, inventory and crews from the colony screen.
  8. Absolutely no. I hate to break it to you as I don't want to influence negatively the way you play the game, but the very challenge of partial recovery is already present in KSP1 (career mode), and as far as I know the average player isn't trying to pinpoint the launchpad or the runway for every single one of their Kerbin reentry. Heck, even most veteran aren't always trying. A 90% recovery at 10 or so kilometers away is pretty damn good enough that most players would only try to land closer it they find pleasure in the challenge. I'd expect the average player would be very satisfied with a good enough result, especially for a mission that is subsequently repeated for free in the background. And in the remote possibility recovery scaling on proximity from KSC in KSP1 career mode was news to you, I strongly advise you against changing your play-style for a handful funds you did not notice until then and which the game in normal difficulty gives you in near infinite abundance already.
  9. I like that best actually. kind of the price of he man hours (Kerbal hours?). With automatic convoys later bringing resources to colonies (and space stations?), I don't think it would be a distraction from gameplay, or be that complicated. In any case, I don't think the players have to worry about item 1 through 7, these are more a myriad of ways in which the developers could address the "set up production and time-warp" issue, and they are not needed all at once, one or 2 on their own could be largely enough. I think 3 to 5 are probably too much for base game. If I had to bet, the devs will go for mostly 1 ("it's ok to use timewarp to get rich") with a tiny bit of 2 and 6 naturally occurring. 7 could be very simple to set up and powerful, but unnecessarily confusing and punishing to the player. Without money, you would still have similar issues but with resources, but I guess not as important as you would still have to move them around, or organize their moving around (in other word, you have to play the game, under hopefully interesting constraints).
  10. A lot of great ideas, it's a pleasure reading the thread. About money I think it's still a very necessary resource for KSP. As a min maxer, when I first got my hands on KSP, I optimized my craft by weight, which led me to put tens of jet engines in every first stage, which felt wrong. I know it's on me, but now that we have money, optimizing with it, and with part count constraints as well feels a lot better; it's the sole reason I started appreciating SRBs and stopped putting ion engines everywhere. It makes sense relative to real life and it add really interesting game-play challenges, where cheap and dirty works great for disposable first stages, but expensive and efficient is better for upper stage whose inefficiencies would be multiplied over the whole craft. I don't think we should replace it entirely with resources. In theory, money could be entirely replaced by resources, production chain, logistic systems and time, but a Factorio + KSP most likely makes for too big of a game. I'm pretty sure KSP2 is intended to still put priority on exploration over exploitation. Being able to buy a rocket with a single resource or for free is necessary for a smooth early game and beginner experience, and free rockets just is not good for me, and probably hard to balance against colony resources. Spending money is a non issue, money can simply be made into the resource with which you buy things on Kerbin, in virtually unlimited amount (unlimited as in money being the only limit). The more you colonize, the more in situ resource you use, the less relevant it becomes, and it progressively gets replaced by a more complex resource system. The game would seamlessly transition from simple exploration to exploration + exploitation. In this paradigm, you essentially own every colony. An alternative system could be that you'd have to buy things from the colony you built, but that sounds like actual economy, harder to manage for the player and much harder to code properly. Defining how to earn money is the challenging part, and yeah I think contracts, as good as they are, need an overhaul. However, I do not think automatic infinite money necessarily causes an issue when used along time warp: If a player wants infinite money, let them have it. It's much better than asking them to grind easy contracts that aren't meant to (they are meant to prevent deadlock). Once you start any kind of business requiring upkeep, be it life support or colony/space station maintenance, time becomes a factor you cannot just warp away. Related to 2, one could implement running cost and profit. For an example of running profit: "Set up a satellites mission for coverage around Kerbin" becomes a one time mission, and generate revenue (from TV/com/internet) for ever once completed. No more grind. For example of running cost: number of Kerbonauts, Kerbin's infrastructure, Settlements (you have to continuously pay the first few settlers and after that the administration, in return they pop mission for permanent revenue given some time and infrastructure, mostly resource extraction but possibly tourism as well). Using 3, you can require budget to be balanced, even if you have a huge provision; so you would still have to put efforts into missions before going sandbox mods, mission which let you immerse and prepare meaningful infrastructure for colonies, and entices you to build such colonies. Using 3, make the missions multipart, including some maintenance that you have to do only once, but after a while. For example, it could start with optional experimental contracts, that are trivial and let you test parts teach you the fundamental, and earn a penny; then a setup part where you actually do something that is here to stay or is supposed to be done repeatedly in the background, at the end of which you earn a stream of revenue. Then sprinkled over the years a couple optional routine missions, preferably each unique (eg, slightly alter a satellite orbit, and put a new, more powerful antenna). Routine checks could be used to encourage good practice, they could be situational and not pop at all if you over engineered your craft (eg. put an antenna with a better rating than strict minimum during setup). Finally based on the routine checks you skipped, a single critical failure mission where the money stream halts until you address the issue. Upon earning a stream of revenue, the game warns you that you will have some maintenance to do in the future, and upon completing the last part, it tells you that you no longer have to worry about it. It encourages you to revisit old crafts, and makes it harder to set an easy infinite money scheme. Just make the game incremental. As in Cookie clicker incremental, where the revenues of letting an early game run overnight at max warp are dwarfed by the revenues (and costs) of a few in game days for a late game Space Program. The kind of incremental in cookie clickers is ludicrous, but is actually very fitting in resource game with epic scope, and even KSP1 scope is epic, there is definitely room and justification for huge discrepancy of prices and revenue between early and late game. Inflation. Similar to 6, make it so that there is no easy hoarding money with some sort of inflation, time based, progress based or both. It's a bit less user friendly, but you can easily display kerbucks adjusted for inflation so as to keep prices constant (but have account numbers diminishing on their own).
  11. They will be added to the game, they are already in the making. Being accessible is one of the core goal of KSP2 and they talked about it quite a bit in one of their yt videos, they are going to make a whole bunch of in game video tutorials even for the most "basic" concepts and are literally testing them on 4 years old and the small parts revealed looked really good. So don't worry, quality tutorials will be delivered and veteran can just ignore them.
  12. That is extremely inefficient, and does not even works often times, as falling straight down to the thicker part of the atmosphere burns a craft a lot easier than a shallow reentry.
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