Jump to content

Search the Community

Showing results for tags 'gravity turn'.

  • Search By Tags

    Type tags separated by commas.
  • Search By Author

Content Type


  • General
    • Announcements
    • Welcome Aboard
  • Kerbal Space Program 2
    • KSP2 Dev Updates
    • KSP2 Discussion
    • KSP2 Suggestions and Development Discussion
    • Challenges & Mission Ideas
    • The KSP2 Spacecraft Exchange
    • Mission Reports
    • KSP2 Prelaunch Archive
  • Kerbal Space Program 2 Gameplay & Technical Support
    • KSP2 Gameplay Questions and Tutorials
    • KSP2 Technical Support (PC, unmodded installs)
    • KSP2 Technical Support (PC, modded installs)
  • Kerbal Space Program 2 Mods
    • KSP2 Mod Discussions
    • KSP2 Mod Releases
    • KSP2 Mod Development
  • Kerbal Space Program 1
    • KSP1 The Daily Kerbal
    • KSP1 Discussion
    • KSP1 Suggestions & Development Discussion
    • KSP1 Challenges & Mission ideas
    • KSP1 The Spacecraft Exchange
    • KSP1 Mission Reports
    • KSP1 Gameplay and Technical Support
    • KSP1 Mods
    • KSP1 Expansions
  • Community
    • Science & Spaceflight
    • Kerbal Network
    • The Lounge
    • KSP Fan Works
  • International
    • International
  • KerbalEDU
    • KerbalEDU
    • KerbalEDU Website


There are no results to display.

Find results in...

Find results that contain...

Date Created

  • Start


Last Updated

  • Start


Filter by number of...


  • Start



Website URL



About me



Found 20 results

  1. I've always been a fan of @Overengineer1's GravityTurn (see original thread). Unfortunately it wasn't updated for a while, so I thought to take care of that myself . Also thanks @sarbian for all the useful MechJeb code of which parts were/are incorparated into this plugin. So this is what it does: Launch a craft into a low orbit with a few customizable settings. Performing a Gravity Turn is arguably the most efficient launch procedure. The plugin will take care of the entire ascent for you by maintaining a strict hold to prograde (as much as possible) and varying the throttle to keep the desired ascent curvature. The circularization burn will be up to you, but it's normally less than 50 m/s. The "First Guess" button tries to find the best settings for a particular rocket. After the trajectory reaches the destination height and the vehicle leaves the atmosphere, you can revert back to launch and use the "Improve Guess" button to get a better set of parameters. Do this multiple times and you will get a very efficient launch. Download the mod here Source on GitHub License: GPL V3 V1.7.7: recompiled for KSP 1.4. ATTENTION: not compatible with 1.3.1 or earlier any more! Feature requests are welcome, but of course subject to spare time restrictions and personal taste... Disclaimers: This mod does not work well with Realism Overhaul because of the way GT uses engine throttling. For scaled up solar systems the calculated launch parameters (and iterations) might not be suitable, so don't expect it to work unless you know how to "guestimate" the parameters yourself. Next on the plan: Reworking UI Adding KSPedia support (maybe) Storing an loading a set of default launch parameters.
  2. First up, here's how to gravity turn in under 60 seconds! Later this will I'll upload the full video. Hope it helps!
  3. This is an in-depth tutorial, but still directed to beginner-intermediate players, on how to do a proper launch and gravity turn with the new aerodynamic model introduced as of version 1.0. This tutorial works for versions 1.0 to 1.3. More than giving a script or set of instructions, my goal with this tutorial is for you to gain an understanding of the factors that affect your rocket's behavior during launch, so that you can apply it to any rocket you fly. For that, you'll need to go through the entire post, but I'm also including a TLDR as a "cheat sheet": TL;DR (courtesy of @kBob) 1. Turn ON SAS and set throttle to give TWR of ~1.5. 2. Launch! 3. When your speed reaches 50 m/s, perform a pitch over maneuver (tip towards the East until pointing between 5° to 10°). 4. When SAS stabilizes (i.e. the control input arrows on the bottom left are all centered), turn it OFF. Avoid control inputs and use only throttle to control your gravity turn (throttle up to turn slower, throttle down to turn faster). 5. When your altitude reaches ~40 km, turn SAS ON. Start pitching down manually towards the horizon and adjust throttle to keep your Ap around 45 seconds in front of you. 6. When your Ap reaches the desired altitude, cut your engines, coast to Ap and circularize. ========================================================================================== General Notes on Gravity Turn You all probably know by this point that to get into orbit you need to go up, above the atmosphere, but you also need to go sideways (i.e. horizontally) very fast. To do this, we could launch straight up until we're out of the atmosphere, then point sideways and accelerate to orbital speed. But that would be very inefficient. We want to launch in a way that we gradually turn sideways while we ascend. This is called a gravity turn. The best way is to do a real gravity turn; that is, a turn caused by gravity and aerodynamic forces, rather than one achieved by actively turning the rocket. It is important to keep this in mind. Design Items Before even launching, you need to take these design items into consideration when building your rocket: TWR: Your thrust-to-weight ratio (TWR) at launch should be relatively low, around 1.5. A higher TWR at the beginning of the launch makes it harder for your rocket to turn naturally, as gravity will have less influence on its trajectory, making it fly straight and screwing up your gravity turn. Keep in mind that drag losses are almost negligible in the new aero, unless your rocket is shaped like a brick or you are going extremely fast in the lower atmosphere. Thus, a slightly higher TWR of around ~2.0 in theory is more efficient, but only if the launch profile is flown correctly. The drawback is it makes your rocket less forgiving in terms of control during ascent, and it shortnes your widnow to make a pitch-over maneuver. What usually ends up happening is that you have to force the gravity turn manually, which does generate significant drag (because you expose the sides of your rocket to the airstream anytime you deviate from your prograde vector), and causes steering losses (Dv wasted on changing direction rather than gaining velocity). This reduces overall efficiency and defeats the purpose of having a higher TWR to begin with. A higher TWR also causes increased stress to the craft, inducing wobble and risking a RUD, especially when trying to maneuver. You may experience heating issues too. For these reasons, in my experience, a TWR of ~1.5 is a good sweet spot between efficiency and controllability of the rocket. Smaller and lighter rockets handle higher TWR's better than big and heavy ones and each craft will have its own sweet spot; you are encouraged to experiment. If you find your TWR at launch is too high, either use a smaller engine or just throttle down, and vice versa. As a final note, all rockets will have their TWR go up as the launch progresses due to shedding weight by burning fuel. This is normal and you should manage by reducing throttle throughout the ascent as needed (more on this below). You can check your TWR with the Kerbal Engineering Redux mod (KER) or with MechJeb, or if you're running a stock game, the G Force meter roughly doubles as a TWR meter (if the G Force meter is pointing at 1 your TWR is roughly 1, and so on). Aerodynamic Stability: You want your rocket to be aerodynamically stable. That means that it will have a natural tendency to fly straight, instead of, say, sideways. Any object that flies through the atmosphere will naturally orient itself with its center of mass (COM) facing forwards relative to its trajectory and its center of drag (COD) facing backwards. You can see this in darts, arrows, badminton cocks, etc. Similarly, you will want to have your rocket's COM in front of your COD. To ensure this, add 3 or 4 winglets or wing surfaces with radial symmetry at the base of the rocket, and if possible cover your payload in a fairing to make it more streamlined. If your rocket insists on flipping, you need to add more/larger wings at the bottom. If that still doesn't fix it, it means your COM is shifting back too much as fuel is burnt. The heaviest part of a rocket in KSP is usually the main ascent engine(s), so the COM will tend to move back as fuel is spent. The easiest way to fix this is to add a small fuel tank at the top of the stage that's experiencing the problem and lock the tank in the VAB (right click on the tank and select the green arrows for both fuel and oxidizer). This fuel tank will act as ballast keeping your COM forward. You can unlock it manually in flight when the rest of the stage's fuel is gone so as to not waste it, and then stage as normal. Ascent Profile Once you've implemented the above design items, follow these steps for your ascent: 1. Turn on SAS and set your throttle to whatever will give you a TWR of ~1.5. 2. Launch! 2. As soon as your speed hits 50 m/s, perform a pitch-over maneuver to begin your gravity turn. To do this, tip your rocket towards the East slightly, until it is pointing between 5° to 10°. Don't start pitching over before your speed is ~50 m/s, otherwise you will likely find yourself horizontal within a few seconds, as your winglets won't be biting into the air hard enough to provide stability. The higher your thrust, the more you need to pitch over initially, because higher thrust makes the rocket want to go straight. If you're using a TWR higher than 1.5, your pitch-over should be to at least 10°. 3. As soon as your SAS stabilizes (i.e. the control input arrows on the bottom left are all centered) turn off the SAS. Watch closely for this moment, as you will have only a small window of a few seconds at most before the SAS starts trying to resist the gravity turn. Turning SAS off while it's trying to steer will cause your rocket to become unstable and lose its heading or possibly break up. You should be done with your pitch-over maneuver and have your SAS turned off by the time your velocity is around 100m/s. If you take too long and your rocket is going too fast by the time you're done, it won't want to continue turning (fast rockets like to go straight, remember?) and you'll have to force the turn manually, which is inefficient and causes stress on your craft. As mentioned above, a gravity turn should happen on its own and not as a result of control input. For particularly unwieldy rockets, you can lock SAS to prograde instead of turning it off during this phase. However, stock SAS is far from perfect and it's best to let gravity and aerodynamic forces do the steering for you. If you do use SAS, be sure to disable it before you hit 35 km to avoid you craft from jolting down suddenly when the navball automatically switches to orbit mode, which happens at around 35 km. 4. Enjoy the view while your prograde marker gradually sinks towards the horizon; your rocket will follow on its own thanks to gravity and aerodynamic forces. Try to avoid control inputs during this phase (i.e. no AWSD), just let it fly. If you need to make adjustments, use throttle. Remember, lower thrust means the rocket turns more, higher thrust makes it want to go straight. At about 10 km altitude, you should be pointing roughly to 45° and your speed should be around 500 m/s. If at 10 km altitude you're still pointing above 45°, your TWR was too high and you went too fast and/or your pitch-over maneuver was too gentle. Next time throttle down more or make a more aggressive pitch-over maneuver. On the other hand, if you're pointing below 45° at 10 km, you went too slow and/or your pitch-over maneuver was too aggressive. Next time use higher thrust or do a gentler pitch-over maneuver. If your rocket flips on its end at any point, it's not aerodynamically stable enough. See above under "Aerodynamic Stability" for possible solutions. 5. At around 40 km altitude, turn SAS back on and start steering manually; use pitch and throttle to keep your Ap around 45 seconds in front of you. Any time you're burning above the horizon, you're wasting part of your thrust to gravity instead of gaining horizontal speed; this is called gravity losses or gravity drag. In the initial stages of the launch, you can't help incurring gravity loses because you need to gain vertical speed to get out of the atmosphere. The atmosphere also means you can't steer away from the prograde vector without inducing aerodynamic drag, steering losses and/or destabilizing your rocket. However, by the time you get to ~ 40 km, you'll have enough vertical speed and the atmosphere will become negligible. Thus, at this point you want to begin gradually pitching down towards the horizon. During this phase, you will also start adjusting your time to Ap. It's most efficient to perform your orbital insertion burn right at Ap, so you want to keep it "hovering" only a few seconds in front of you. Of course, you don't want to it to get too close either, otherwise you risk passing it and falling back down into the atmosphere. A time to Ap of ~45 seconds is a good rule of thumb to balance safety and efficiency. To control your time to Ap, use pitch and throttle. If your time to Ap is more than 45 sec, throttle down a bit and point more horizontal, and vice versa. Avoid pitching below the horizon. Continue adjusting pitch and throttle until your Ap reaches your desired altitude, at which point you can cut your engines, coast to Ap and circularize. Note that as you approach orbital speed, there will be a point when your Ap will begin shooting away even if pointing straight at the horizon and no matter how much you throttle down (unless you cut the engines of course). If you reach this point, just let it go until engine cutoff; any efficiency gains from keeping your Ap near you will be negligible by then. Advanced Mode Try doing the ascent and orbital insertion in a continuous burn. This is the most efficient profile (citation needed) and it's extremely satisfying. Easier said than done, though. To pull it off, you need to allow your time to Ap to creep closer and closer during steps 4 and 5, while not allowing it to get higher than your intended orbital altitude. You do this by reducing throttle and lowering your pitch in a more aggressive manner. The closer you are to orbital velocity, the closer you can allow yourself to get to your Ap. You want to hit orbital velocity exactly at Ap. There will be much trial and error and the exact procedure will vary from rocket to rocket, but give it a try!
  4. So, when I'm doing a gravity turn. I always have SAS on, I know how to get into orbit and do a gravity turn. Though, recently when I've been doing a gravity turn. My pro grade pitches slightly up, note that i'm not giving any input for it to be doing that. Not sure why, and like I said. I've done this so many times before, and i've done it really good. Though now that I do a gravity turn, I have this problem. I usually use stock KSP rockets as I'm not very creative. And if its built by the KSP team, its impossible to be a design flaw. The only thing I add onto the stock ksp rockets is the mechjeb case which I usually place at the command pod. I'm not quite sure as to why this might be happening. I'll be sure to answer any questions you guys have!
  5. Is there a general rule of thumb as to the optimum altitude/velocity/pressure (Q, I think) to jettison fairings-- where the aerodynamic drag reduction is no longer worth the weight/gravity loss? I don't really need the exact equations-- just a general "feel" for the right timing/altitude. Thinking of firing off a series of sounding rockets to test, but I imagine someone else has done a lot more thinking about it already...
  6. First post so apologizes if I did not find a previous thread. Just got the KSP 1.4.0 update and I have noticed that my Gravity Turn Mod (1.7.6) has behaves oddly now. A couple of different times it has missed the destination height because the engines stayed on and I can't abort which causes problems too. For example I don't know if its the update but I can't time warp, and controls won't work until I hit escape to bring up the menu and then hit it again. Anyone else having this problem and did you find a solution or are we crossing our fingers for an update to the mod? Thanks
  7. Or more precisely how do you correct a gravity turn mid flight? So I have started playing with KOS and I am trying to figure out how to do a gravity turn. I am attempting to write a generic script that can work with a range of vehicles. I have written, what I feel, are a couple of really good predictive scripts that use TWR, Dynamic pressure, AP, Time to AP, vertical speed and Burn time. But they keep getting messed up by the changing TWR and staging. When TWR goes up the craft pitches down too early. Then at staging when TWR drops it realizes it has to pitch up a lot. I attempted using a TWR correction factor with little success as it appears the relationship is very non-linear. So I think I need a way to minimize pitching adjustments as TWR departs from average. Perhaps 1/((AverageTWR-TWR)^2+1/TWR). Would average acceleration would be DV/BurnTime? Thus making average TWR = Average Acceleration/9.8. I am just about out of ideas and the last thing I want to do is build a lookup table and fly to that.
  8. I need help... I've been following the advice here: In a ship of this design: Parachute, two mystery goo's, a temp sensor and pressure measure, a service bay with kerbal engineer inside, heatshield. FL-t400 fuel then lv-909, decoulper, then 2x fl-t400 and an LV-t30 - dv 3.8k. I try the method above and I simply go wrong! I just don't make it to orbit! I assume my turn went too fast, as I got heated up too! Any advice other than just practice?
  9. I finally managed to build a reasonable craft for Eve Space Program that can get to Eve orbit with about 1300-1400 m/s dV left. In career mode, with only Tier 3 and 4 parts. Craft file here, uses OhioBob's Eve Optimized Engines. After several attempts, my best effort is in this video here. The biggest challenges of the current incarnation of the Eve Space Program mod are the lack of biomes outside of the KSC, and the distance of most survey contracts; the KSC is a quarter of a world away from where the game puts those surveys. This leaves part tests, science grinding around KSC, and a full fundraising campaign strategy (25% of reputation going to funds) to pay for building upgrades. Otherwise I'd be using a lot better parts for this craft. As it stands, the only remaining source of decent science is Gilly, and I can't reach that and get back on 1400 m/s. I didn't do any dV math really; just tried plotting to Gilly's orbit needing 1425 or so m/s, and came up short just by 20+ m/s. That being said, I remember someone saying that ascending from Eve's surface to orbit needs a launch profile that goes straight up for a large part of the ascent, then starts the gravity turn very high up. With this craft I find I can start my turn just around 20 km, and also before staging away the last of the Adam engines and going to my first non-EoE; the Swivel, close to 35-40 km. Then some careful throttling and I can get to about 1400 m/s orbit speed before staging away the Swivel and going to my Terrier, finally closing my orbit with maybe 2/5th of my fuel. What would be a better ascent profile for launching into Eve orbit? Where to start turning away from vertical? At what altitude and at what speed should I have a pitch of 45 degrees? If you try this craft, note that Eve Space Program's launch pad is only at 450 m altitude, and I'm using tank priorities and decoupler fuel crossfeed to use a hybrid of onion staging and asparagus staging, so watch the tank levels on ascent. [Update 15 APR] There's so much good advice here I can't mark any one answer as correct. I upvoted all of the good answers and gave out likes.
  10. As the name implies, I am wondering what are the most efficient gravity turns for Earth and Mars? I don't know if RSS and Real Life gravity turns are the same, but I am wanting real life and not RSS, unless, of course, they are the same. Lastly, how do I calculate Delta-V?
  11. I'm probably a pain to the KSP Community but I've got another problem, so lets just get this over with. I'll be providing pictures, don't panic xD Pictures of the Payload: Probe Controlled Circulurisation Booster: Ascent Stage: Craft Download: https://www.dropbox.com/s/et6vr9ij4kwnzmp/The Hitchhiker Orbital Station.craft?dl=0 When I try to ascend, it starts pitching over in the wrong direction. I want to pitch over towards 90 Degrees on the Navball but my ship wants to do anything but that, all TWR and Delta-V Costs are provided in the screenshots above. (Ignore the staging, it is a mistake xD) So any help would be appreciated! Ascent Profile GIF (To show you what I mean by how it is pitching in the wrong direction): Thanks KSP Forums (Again) xD EDIT: Please tell me how I can show you the image of the GIF. I'd like help with that, so if anyone can, much appreciated xD
  12. (To tell the truth, I don't know if doing a gravity turn manually on Eve is possible. Maybe it is with winglets, maybe not. Feel free to correct me.) So most of us know that to get to orbit efficiently, you need to do a gravity turn and have an AoA of roughly 45 degrees at 10km on Kerbin. This is done by tipping over gradually while you are ascending. Getting to orbit this way is the most efficient and will get you into orbit using the least amount of DV. However on Eve, such a maneuver is very difficult and most people just go straight up and turn after they have gotten up high enough not to flip over when they turn it the slightest. Doing a gravity turn on Eve like Kerbin is hard and makes getting to orbit not as efficient as on Kerbin. In fact some might say it is impossible to do. Until... now. Before 1.2, using the SAS to point in a certain direction, such as prograde, retrograde, radial and so on could cause an engine to gimbal uncontrollably and force you to keep the ship focused on a certain direction manually. This bug was fixed in 1.2 and now, if you get it right, you can have that... do the gravity turn for you. All you have to do is move slightly to one side while you are firing the engines and the prograde vector will move forward in that direction. Then just hold prograde and you will follow it and keep it moving. Now yesterday, I built an Eve lander, dropped it through Eve's atmosphere and landed it. This was a test run to land and fly to orbit so I used the debug menu to edit it into low Eve orbit. It took me a few tries to get the optimal launch, (i.e make it go straight up and not flip over. ) but I did it and on this one attempt, I was tilted slightly down the navball on the 90 line. My prograde vector was slowly moving down at the same time so I clicked on hold prograde. I then watched it slowly tip over until at 10 km, it was at 45 degrees AoA. Now I know since Eve's atmosphere ends at 90 km and Kerbin's ends at 70 km that this is a less optimal gravity turn maneuver since you are going to want to be going up more and not going sideways as much But I got into orbit with tons of DV to spare and also did what I call an optimal flight to orbit. Sure the nose got hot at one point and almost blew up and as I said previously, this wasn't an optimal gravity turn but it worked. So... what I am wondering is, if you use this trajectory to orbit, how small can you make your landers? Also what are your thoughts on this discovery? And have any of you encountered this yet? Thanks. Fire
  13. Hi! This is a nice rocket that has just enough delta v to get into low Kerbin orbit and back. Can you fligh it into orbit? Have a try .... (if you know how a gravity turne works) File for KSP 1.2.1: https://drive.google.com/file/d/0B4-Q0g-nbUkOSFNNU05iSEdpM0E/view?usp=sharing Reward: For the Kerbonaut how has the most fuel left during the reentry to Kerbin I offer a post flight data and charts like this: http://imgur.com/a/KlGKj But I need the .craft file of the rockte to do a testflight to log the data. Only stock!!! expire date: 15.12.2016 Thanks for your interest!
  14. Save fuel by flying a stock gravity turn to orbit This is a competition in KSP version 1.2.1 to launch the stock "Kerbal 1-5" from the KSC launch pad to low Kerbin orbit, with as much fuel left over as possible. Motivation for challenge My interest for this topic recently rearose when this question was asked and discussed. I haven't played much recently, but I remember how difficult I found it to estimate the fuel needed to get to orbit back in KSP ver. 1.0.4. According to the guides and forum posts you are supposed to fly a gravity turn to save as much fuel as possible. Most of the posts I found however aren't necessarily entirely up to date to the newest KSP versions. We will soon get KSP ver. 1.2, and then while the modders are busy updating mods I thought I would get someone to answer the above question, by kerbally kunningly masking it as a 'challenge'. In short, I am curious how much fuel I should expect to have left once the Kerbal 1-5 reaches LKO. At first I had less than 30 units of liquid fuel left (the near vertical approach). Now I am up to a shade over 40 units. It can probably be improved substantially still. I will soon add detailed rules (none of the easy tricks, like adjusting the thrust limiter, are allowed), and explain the scoring (a slight variation on the number of unused liquid fuel units). Vanilla rules The idea is to find out just how much fuel the stock "Kerbal 1-5" rocket model has left, when flown to low Kerbin orbit as suggested by the design. When I say suggested by the design, I mean that the strange extra docking port should stay on, and the thrust limiters should stay in place too. Attempts should be flown in KSP version 1.2.1 1.2 without any physics changing mods. Difficulty settings that may affect the flight must be at the default values; i.e. re-entry heating must be at 100 %, and changes in the debug menus are not allowed. The launch takes place from the KSC launch pad. Any time of day is acceptable as the launch time. The vessel is the stock "Kerbal 1-5" manned by one kerbal. Changes to staging is not allowed; neither is manually staging/ejecting/activating the staged parts. You may not tweak the stock vessel in any way; in particular you must leave the thrust limiters in place. An exception to the above rule is that you are allowed to lock and unlock the engine gimbals (and/or change the gimbal limits). You are also allowed to change, disable and enable the reaction wheel mode to suit your flying style. You are not allowed to use the RCS; all of the monopropellant must be spared. Neither are you allowed to go on EVA or bump into other crafts. The target orbit is an eastbound equatorial orbit of Kerbin at 80 km ASL. Your orbit is, however, allowed to be any orbit of Kerbin with periapsis and apoapsis both at or above 80'000 m. You may manipulate the throttle as you wish, and you may take any path to space/orbit that you think best, as long as you don't leave the Kerbin SoI. You are allowed to take advantage of SAS, autopilot mods and custom instruments (e.g. time to apoapsis and inclination read outs). Challenge participation reports and scoring When submitting results please report all of the following. The challenge entry category. "Vanilla": The main/nominal category. The one described in this section. "FAR": Using the FAR (aerodynamics) mod. See below. "GOaP": The "Get Out and Push" category. See below. Any control automation used. "AP": If you utilized an autopilot of sorts. Please tell us about the settings you chose, particular if you manage to find a particular efficient gravity turn strategy. "SAS": If you did not use an autopilot, but did engage the stock SAS. "Manual": If you flew the entire mission by hand (and without SAS). The number of liquid fuel units left on board, once in orbit. The periapsis and apoapsis of your orbit. Visible heating during flight. I don't think the stock Kerbal 1-5 is prone to heat issues, but maybe visible heat effects are a byproduct of an optimal gravity turn. Please let us know if you notice heat effects, and try to describe their 'severity'. Anything out of the ordinary. Are you for instance launching at a particular time of day to take advantage of the hot (and less dense) atmosphere. Your score is based on the amount of liquid fuel left (in your FL-T400 fuel tank) when your orbit is established. In the nominal category ("Vanilla"), the score is adjusted slightly for your actual achieved periapsis and apoapsis, and given as a percentage. A percentage score is the more action packed option for a competition! The score formula is presented in a thread of its own, so that it may be discussed separately. The score formula for the stock configured Kerbal 1-5 will give you a score of roughly 15 % if you have 15 units of liquid fuel left (poor efficiency), and roughly 70 % if you have 70 units left (outstanding efficiency). The scale is not linear. Getting into (80 km) orbit with no fuel left is enough to score above 3 %, and a shade over 90 units are required to get a perfect, and probably impossible, score of 100 %. [Note: the score formula may yet be adjusted to accommodate changes introduced in KSP ver. 1.2; the score formula is updated for KSP ver. 1.2.1]. The corrections for actual periapsis and apoapsis is given for periapsis above 80 km and below 100 km and apoapsis above 80 km and below 120 km. The idea is that if your gravity turn happens to have a build-in overshoot, then you will not have wasted all of that overshoot energy (i.e. fuel) in regards to your score. All else being equal you will loose some points though, compared to a tighter cheaper alternative. The corrections are made because the challenge should not primarily be about who can hit 80 km with the greatest precision. Entries in the "FAR" and "GOaP" categories are not adjusted for periapsis or apoapsis. The unadjusted scores ("FAR" and "GOaP") are exactly the number of liquid fuel units left in orbit. The percentage score formula is used only for entries in the nominal ("Vanilla") category. FAR ladder rules GOaP intro There are already a few good (and surprisingly sane) entries in the "Get Out and Push" (GOaP) category, so let us write some 'formal' rules for the GOaP challenge part. A group of dry and boring optimizer consultants have visited the Kerbal Space Center recently. Their report suggests to reduce the number of Rapid Unplanned Disassembly events and to layoff Kerbals. After reading the report Max L. Kerman quickly drew up calculations showing that the savings necessary to solve the current funding crisis can be achieved by a combination of flying more efficient gravity turns and a bit of creative tinkering. It is now up to you to show that the Sunday launches of the Kerbal 1-5 are not just leisure trips to orbit, but in fact important "In Orbit Fuel Contingency Reserve" missions. You do that by displaying that the Kerbal 1-5 has a viable amount of fuel, that it may function as an orbital refueler, i.e. have as much fuel as possible left over once in orbit. Not all of the tinkering is quite aboveboard, so there are restrictions as to which actions you may perform below 1000 m above sea level. GOaP rules Leader board (vanilla template) Eidahlil; 39.22 %; KSP 1.2 Gordon Fecyk; 37.66 %; KSP 1.2.1 (video included) tg626; 33.37 %; KSP 1.2 (a touch below 80 km) emaier138; 31.32 %; KSP 1.2 tseitsei89; 41.37 %; KSP 1.1.3 (score suspended) mk1980; 41.29 %; KSP 1.1.3 (score suspended) "Name"; "Efficienty score"; Comment Leader board (FAR and GOaP)
  15. In all tutorials I have seen it says that in order to get to orbit I shall use the "D" key (yaw control) to turn at 10 km so that the rocket's angle is 45 deg and heading is East. The thing is it doesn't work that way, first when I use "D" the rocket almost doesn't react, when I start pressing it continuously at ~5kms all I get at 10 kms is about 6-8 degrees and never heading East, always North. I have to play with roll and pitch in order to get more or less right heading, but fighting with it I either overshoot the orbit (apiapsis ~100kms) or undershoot it (once it was at ~40 kms). What is most mysterious is why the rocket doesn't react to controls. It is almost as if the only thing controlling it was the wheels in the pod, whereas I expected the winglets to have flaps etc. - do they? Can't record a film showing my tries (Corel's Video Studio Pro X9 again crashing on me - don't buy that crap), but here is the pic of my rocket.
  16. The definition of a perfect gravity turn according to Wikipedia (always reliable) is an ascent path such that at any given point (after the pitchover maneuver), your angle of attack is zero. Here's my issue: I want to test using this definition to optimize my gravity turns by keeping my angle of attack at zero, but I have no idea how to calculate the angle of attack for my rockets. Most internet information, such as pages on Wikipedia, focus on angle of attack for aircraft. What is the definition of angle of attack for a rocket? How do I find a rocket's angle of attack using tools in KSP?
  17. How to measure the efficiency of a gravity turn To make my gravity turn challenge a bit more interesting the scores will be given as percentage scores. I have seen percentage scores used in game reviews, school tests and what not - so it must be a cool score measure right? I post the score description to this separate post in case anyone wants to discuss and/or refine the idea. Gravity turn efficiency score Imagine that we can send our vessel to orbit by doing two short powerful explosion-like burns. First a burn that will shoot us all the way to space, a burn of strength "v" (for vertical) say. Then, just above Kerbin's atmosphere our positive vertical speed runs out, and we do another burn to quickly accelerate to orbital speed, a burn of strength "h" (for horizontal) say. I imagine this 'burn model' as depicted in this (first) figure. Now imagine another way to send the vessel to orbit. Maybe we don't need to shoot the vessel all the way to space with the first burn. Instead we only clear the thicker part of the atmosphere with the first burn, and then we angle the second burn to take care of both the needed "h" (horizontal component) burn and the missing part of the "v" (vertical component) burn. I imagine that this improved 'burn model' looks like this (second) figure. The idea of the score is to make a guess for how much total burn strength it would take to first burn and fly vertical and then burn and fly horizontal. We could call this our worst case budget. Once we know how much burn we actually used in total in some instance, we expect to see that we did better than our worst case budget. Compare the actual total burn (i.e. fuel used) with the burn from the second figure to assess if the saving is large (i.e. a large alpha) or small (i.e. an alpha just barely above zero). Interpretation of alpha We pick some "worst case budget" as a reference and can then assign an alpha to the actual total burn that we record. The interpretation is that a negative alpha value means we used more fuel than our "worst case budget". We should, in theory, avoid this, as it implies we could save fuel simply by flying straight up and then accelerate along the horizon. In practice though, we might fly an inefficient path for non-fuel related reasons. An alpha of around zero percent means that our fuel usage turned out to match our "worst case budget". An alpha of 100 % is interpreted as the theoretically ideal composite of the vertical and horizontal burns. If the gravity turn efficiency is even better than that, then alpha rises to above 100 %; maybe that is achievable for space planes - time will tell. Technically alpha, as calculated by the formula below, can surpass infinity, but that requires a ridiculously cheap launch trajectory to orbit. Formula Label the actual burn strength total as "t", and the vertical and horizontal components of the worst case budget as "v" and "h" respectively. Assuming that "t" is larger than "v", alpha is equal to (h^2-(t-v)^2)/(2*v*(t-v)) . The Kerbal 1-5 case [edit: for KSP version 1.2.1] Let us take a "Kerbal 1-5" budget as an example. I have uploaded a KSP version 1.2.1 budget, that may be used to score the entries in this challenge. Budget and scoring spreadsheet The budgeted vertical and horizontal components are 2239 and 2220 m/s of vacuum delta-V. The delta-V potential of the stock configured Kerbal 1-5 is 4398 m/s, assuming the main throttle is kept closed until the boosters are done. The budget indicates that, if you fly straight up to 70 km before turning, then the rocket cannot make it to orbit. Notice that in practice, even if launching vertically, we probably want to turn the rocket towards the horizon before we reach 70 km, so the budget is really for a quite hypothetical worst case scenario. The threshold for an alpha-score of 100 percent is to get to LKO (70 km) using only 3153 m/s of delta-V. To me that goal seems unattainable. On the other hand, perhaps 3153 m/s is not an unreasonable indication of the upper bound for the gravity turn efficiency of the stock Kerbal 1-5. By the way, the reason the spreadsheet says "NO SCORE" is because the challenge is for an 80 km orbit, so 70 km is too low.
  18. Hello, I was hoping getting MechJeb's ascent guidance module would help me automate the launch but I can't quite follow the ascent path. Seems like my rocket is too powerful so I've tried to limit throttle and/or acceleration during ascent but it's very clumsy and it usually works poorly. http://steamcommunity.com/profiles/76561198276590575/screenshot/499154497084905198 Is this a rocket design flaw or are there smarter parameters in the ascent guidance?
  19. So MechJeb is not turning my rocket no matter how high I allow its angle of attack to be. I have reset all settings to default, please help. When it begins executing a gravity turn, it lights up green as if it is turning it to the max but nothing happens, and I checked, the ship turns and can even make it to orbit just fine so it is a problem with mech jeb. The reaction wheels on the comman pod say idle, I turned rcs on no indication of it working
  • Create New...