Tarmenius

closette- I\'m trusting you for three reasons: 1: Your reputation on these boards warrants it in my view, 2: PakledHostage (who made the challenge that inspired this one) did as well, and 3: My true goal for this challenge is to establish the most efficient descent method that anyone who wants to can duplicate. Competition and placement on the Leaderboards is of lesser importance. At least, that\'s how I see it. Have you tried assigning the throttle controls to different keys, freeing up CTRL? I haven\'t needed to re-map any, so I don\'t know if certain functions are locked to certain keys. On somewhat of a side note, I got real curious about how closely our descent paths matched those of the Apollo missions. I found the NASA Technical Memorandum 'Apollo Lunar Descent And Ascent Trajectories,' March 1970. There\'s some very interesting stuff in there. http://www.hq.nasa.gov/alsj/nasa58040.pdf Of particular relevance, the 2nd and 3rd pages describe the descent.

Congratulations on taking the lead, JellyCubes! And an impressive show of mathmatical force as well.

Excellent work as usual, closette; that chart will come in very handy. As for the calculations of delta-v, don\'t worry about not going through the steps. It looks a little beyond what I\'d be comfortable doing anyway. Though I\'ll still be trying to reach for that 162.5kg mark And to BlazingAngel665, I would also be very interested to hear how it goes using KSP in the classroom. Had this been around when I was in high school, my Applied Physics teacher would have loved it. That was the best class ever. [EDIT]: In my most recent attempt, I set my Pe to 2500m. I came very close to being a crater on some mountain, so I decided to land. After some pretty sloppy maneuvering, I still touched down with 143.9kg in the tank.

Nice results everyone! I\'ve updated the Leaderboards accordingly. Thanks! And good work with the mathmatical analysis. If you feel like making that chart, I think it would be interesting and helpful for anyone who wants to get the most out of their landers. The deeper into this game I get, the more I want to brush up on my Advanced Algebra. Ten years of not using it has really taken its toll. On a related note, how hard is it to convert fuel spent into delta-v? And with good reason! Congrats on performing above and beyond! And with practically only fumes left in the tank, too. No need to open it. First move your existing persistent.sfs file from the 'KSP/saves/default' folder to somewhere outside KSP so you can keep any ongoing missions you may have. Then copy mine and paste it where yours was.

Zephram, that\'s pretty much the same result I\'ve been getting. With MechJeb, the LAND button does a mostly-direct descent and the results there were equally bad. I\'m going to play around with the Landing Autopilot a bit more before posting an official entry. My initial attempt was to select a landing site a good distance away, and MechJeb made a pretty shallow approach, touching down with 130kg remaining. I\'m going to see if distance to landing site determines how shallow the approach is and how that effects fuel consumption. PakledHostage, what do you mean by a 'reverse gravity turn'? Is that where you start out burning horizontally and let the craft slowly drift to vertical? If so, It\'s not a method I\'ve tried yet but can definitely give it a go.

I think you\'ve pretty much got it right already, though I would add that when you point 180o (at the loaction your arrow indicates) it should also be level with the aritficial horizon in the Navball. Keep in mind that you will likely need to re-adjust your AP and Pe afterward. At least, this is how I would do it if I were in your position. Can\'t guarantee it\'s right PS- kudos on illustrating what you\'re trying to accomplish and describing it simply and clearly.

So am I. And if there\'s one thing I\'ve learned about myself, it\'s that I often can\'t deny my curiosity. So as soon as I get back from watching my local fireworks display, I will get the MechJeb version set up. [EDIT] MechJeb version now added. By the way does anyone know how I might list the attachments in such a way that makes it easier to distinguish which is which? I feel as though simply saying 'The first is stock; the second has MechJeb' isn\'t good enough.

Good job! I\'ve updated your position on the Leaderboard. I\'m not going to consider it cheating to use that addon, since the true goal of this challenge is to find the ideal approach method. Having an accurate ground-relative altitude reading will only help make more accurate decisions about when to thrust and therefore a more reliable method. Anyone else who wants to use it is free to as well. [Edit]: In fact, I considered making a persistance file with MechJeb included for comparison. If you guys want, I would be happy to do it.

Congrats Apotheosist! You\'ve taken the lead. After attempting a 'direct descent' where I simply cancelled out as much horizontal velocity as I could then fell for 95km, I discovered I\'m not very good at judging distances. It tested my nerves the last few km before I simply could stand it, and I didn\'t quite get the timing right. I ended up having to maintain a small amount of thrust for the rest of the descent, leaving me with about 107kg remaining fuel. So that was no good. Then I tried something close to what the rest of you have done. I even managed to pass through part of that huge Mare-side ravine. 8) Unfortunately, I realized too late that my orbit would take me through one of the peaks at the other end (It\'s that teeny, tiny little bump on the horizon directly above my craft). This occured to me soon after the awe wore off from buzzing that slope to the immediate left of the 'little bump.' I think Bob knew long before I did. So, making sure not to repeat that little accident, I tried again. It was a pretty smooth run, and I ended up with 130.3kg remaining. Bluejayek: Out of curiosity, did you burn all at once just before touchdown, or keep a steady descent rate?

So, a while back I was on my way to the Mun. Everything was going well: I had an efficient ascent from Kerbin, my orbital inclination was as close to the Mun\'s as I could want, and the TMI timing looked good (this was before the patched conics display). In the middle of my Munar Capture burn, my engine cuts out even though I have 4 remaining fuel tanks. Realizing the mission was doomed, I separated my Emergency Return Stage and maneuvered around to get a view of the problem. Here\'s what I saw: Needless to say, I fired the Quality Assurance guy.

Good work, PakledHostage! Looks like I\'m going to have to gather my courage and try for a return trip myself. Has anyone tried a 'direct descent' method yet? I\'d be interested to see how it stacks up. I\'ll be trying it, of course, but I\'m not exactly the most skilled pilot around

I love the smell of results in the morning! Zephram Kerman, I stand corrected and thouroughly impressed that a return to Kerbin has been accomplished! I\'d say Bob should get a stack of lotto tickets. I can just picture the rendezvous crew gearing up, only to have Jeb walk in and say 'You seriously expected me to not to try it?!' tjoreilly, I\'m glad you enjoyed it! Very nice results, indeed. I don\'t intend to stipulate that the craft needs to remain completely intact. Of course, if someone uses the rocket to break their fall and save fuel, that would kind of violate the spirit of the challenge. Even so, I could see myself making an exception for a particularly Kerbal use of that method. And you hit the nail on the head with why I included an ASAS on the lander. Without it, I have a very hard time keeping the lander oriented upright (even with CAPS-lock on) and I figured others might as well. Didn\'t want them to be turned off to this challenge because of a lander that\'s too difficult to pilot.

I\'ve noticed that debris will only ignore atmosphere above 23000m. If you time your stages to be jettisoned when your Pe is just below that, it will not stay in orbit. That\'s where I tend to ditch my final ascent stages (even if they have some fuel left) to avoid clutter.

I didn\'t say it was impossible, just 'unsafe.' Though honestly, 'impossible' was pretty much what I was thinking so you got me there. But I love to be proved wrong, so by all means go for it. Just make sure to record the screenshot showing how much fuel you have left before taking off again. The ASAS is there mainly as an aid to my lack of fine keyboard skills, and I wanted to keep this accessible to anyone. The first lander I was going to use even had RCS to help kill that pesky horizontal velocity while only meters from touchdown. Then it occured to me that without a way to measure how much RCS fuel was left, the results would be less than accurate. I\'m looking forward to seeing what you come up with!

Inspired by the Optimal Ascent challenge (http://kerbalspaceprogram.com/forum/index.php?topic=14571.0), the objective here is to discover and demonstrate the most fuel-efficient method of descending to the Mun\'s surface as determined by amount of fuel remaining. I know there has been plenty of discussion on the subject in the past (and feel free to have more of it here), but I couldn\'t find a previous challenge that singled out this phase of a mission to allow more direct comparison. So, I built a very simple lander and strapped it onto a rocket that would get it into Munar orbit. Once there, I jettisoned and destroyed the TMI/MC (Trans-Munar Injection/Munar Capture) stage then saved my persistance file which I have included below. Simply move your existing persistance file (found in the 'KSP/saves/default' folder) to another location for easy recovery, download mine and place it where yours was. The lander is all-stock (0.15.2) and the only craft in the file. Its orbit is 100km over the equator and has just entered the day side of the Mun, so you won\'t have to wait to find a good landing spot. Also note that you will have to activate the lander stage with spacebar before you can fire the engines. I did this intentionally as a way to demonstrate that you would be starting with a 100% full tank of fuel. My method was to make a fairly steep approach and do most of my burning over the last 2500m or so. I freaked out a bit at around 3500m becasue the ground was coming up way too fast for my comfort level. Thankfully the lander is pretty light so I was able to reduce my descent rate in time. In the end I touched down at ~3.5 m/s with 113.3 Gubs of fuel remaining and everyone\'s just happy to be on the ground. I think I have enough fuel to at least get back into Munar orbit so a rendezvous can be made to get the intrepid crew home, but if someone can land this and get back to orbit around Kerbin I will be impressed (but not surprised given the skills of many forum members). I say 'orbit' because the lander has no parachute or decoupler to provide a safe return. [NEW] In the interest of satisfying curiosity, I have included a version of the lander with MechJeb. It is the second file listed. [NEWER] As JellyCubes pointed out: 'the \'kg\' value seen when right-clicking a fuel tank has absolutely no real meaning.' Knowing this, I have unofficially renamed fuel units for this challenge. They shall now be referred to as 'Gubs,' unless something more amusing is proposed [NEWEST] As this challenge progressed, the optimal descent method became clear. I have added a description of that method to the bottom of this post. Of course, anyone is still free to claim their spots on the Leaderboards as variables like landing location and pilot skill are still a factor. Now it\'s your turn. Honor, glory and bragging rights are at stake here! Claim them if you can! Exemplary Service Medal Awarded to those pilots who succesfully returned the crew to Kerbin. Parades and talk-show appearances are assured. Zephram Kerman BlazingAngel665 (MechJeb assisted) pushingrobot mager42 (MechJeb assisted) Leaderboard (No MechJeb): 1. JellyCubes: 154.5 Gubs 2. Apotheosist: 153.8 Gubs 3. pushingrobot: 150.5 Gubs 4. Kosmo-not: 148.6 Gubs 5. Zephram Kerman: 148.5 Gubs 6. PakledHostage: 147.6 Gubs 7. closette: 144.9 Gubs 8. tjoreilly: 144.2 Gubs 9. Tarmenius: 143.9 Gubs 10. Bluejayek: 141.8 Gubs Leaderboard (with MechJeb): 1. mager42: 147.7 Gubs 2. BlazingAngel665: 144.4 Gubs The Method First a disclaimer: The following demonstrates the most efficient Munar descent method when starting from an already-established orbit. By planning your Munar Insertion properly, it is possible to use even less fuel. But those details will be for another time. Once a rough landing site has been chosen, wait until your orbit has taken you to the opposite side of the Mun from it. Burn retrograde to bring your Periapsis (Pe) as low as you feel comfortable while still above the terrain (this will likely be a guess so don\'t worry too much about precision here). Flip back to prograde then wait until Pe, watching the terrain ahead of your craft to avoid an unscheduled (and destructive) landing and to locate a desirable landing site. Nearing Pe, you should be almost pointed retrograde. Find your landing site and be ready to finish turning retrograde (if you haven\'t already) and burn off your horizontal velocity. Since each lander design will require different burn times to eliminate horizontal velocity, you\'re going to have to make a best guess about when to begin. Toward the end of the burn, when most of your horizontal velocity has been reduced, the retrograde marker on the NavBall will begin to climb toward +90o vertical. At this point you may want to reduce throttle and pitch over to keep up with the retrograde marker, making sure to reduce thrust enough that you are still losing altitude. Ideally, this 'reverse gravity turn' will have you pointed vertical by the time you\'re just about to land. From here, simply control your descent rate to suit the limits of your lander and you should be on the ground with plenty of fuel left (asuming you brought enough in the first place ) Where Do We Go From Here? If you\'ve been reading the posts in this challenge, you should already be aware that the discussion has shifted toward the Insertion phase of Mun missions. That discussion has spawned a new Challenge, which can be found here: http://kerbalspaceprogram.com/forum/index.php?topic=15844.0. I want to stress again that this is not necessarily the end of Optimal Descent and I will still be monitoring for new entries as well as occasionally attempting to improve my own. A huge 'Thank You' to all who participated (and preemptively to those who may in the future); each contribution is a valuable part in finding the answer to this challenge\'s question.

I personally think we\'re all pretty much there. Like I said in an earlier post, all of the non-MechJeb positions are within one second\'s burn time (at full thrust) of each other. Without the use of computer-controlled programs for throttle and heading changes, any ascent profile can only be fine-tuned so far. Of course, despite all that I\'m still going to try breaking the 90kg mark As for your question about the coasting phase, option 'a' seems to imply that your MECO is happening below 30,000m. If that\'s the case, your ascent may be too steep. On my ascents, MECO was around 43,000m and my velocity was about 1400 m/s. While coasting, I would only lose 300 or so meters from my Ap. I\'ll be making another attempt or two in a few minutes to get more exact numbers because my memory could be a bit off and it bothers me some when I\'m that vague . At Ap -20s I would start circularizing, pitching up very slightly to raise Ap if needed. Toward the end of circularization, thrust is minimized then made in quick bursts to prevent Ap from running away from me. The key there is to keep Ap just off the nose of the spacecraft. [Edit]: Fixed the numbers

My first orbital rendezvous, I was able to actually make contact with my target. The middle of a Munar capture burn is the wrong time to notice you forgot to add fuel lines! Leaving the Mun offered a very nice veiw of Kerbin. My favorite little spaceplane from 0.14, the Peregrine. My first real-life plane conversion with the classic 'cloud' effect.

Well, in my limited experience with MechJeb I did notice that if I had a steeper ascent with a Turn Start Altitude above 10km, it would make a small pitch adjustment at first and then the bulk of the gravity turn significantly later. So far, the timing of its maneuvers has been consistent if the settings have remained unchanged. I haven\'t yet used MechJeb on the larger, multi-stage designs, so I can\'t say how it handles them. My next set of trials will use my standard Mun-capable rocket to see whether its ideal profile is much different. It\'ll be interesting to see how different a (relatively) more massive rocket performs.

Thanks, closette. I was actually surprised when it turned out that well. It started as a 'what the heck, I\'ll try again for laughs' sort of thing. I used the Ascent Stats when doing all my MechJeb trials, which is what I would base my decisions on for the following launch. I started with a profile that gave good results, then tweaked it little-by-little to watch the affects and scribble them on the notepad I keep on my desk. The effects were usually something like 'Well, I shaved a couple hundred m/s from the Gravity Losses, but gained it all back with interest in Drag and Steering losses.' Or vice-versa. Of course, like I said in an earlier post, I am still new to using MechJeb so there are quite possibly things I overlooked or failed to account for. For example, it wouldn\'t give the stats for ascents flown manually. I really wanted to know how my own method fared. Anyway, I highly recommend using the Ascent Stats to help figure out where to try and shave off those precious m/s. It was an invaluable tool in my process.

Congratulations! Did the crew make it back home yet, or are they going to stay there and be a monument? And now that you\'ve gotten that accomplished, are you going to do more with only stock designs, or was once enough?

Sounds right to me, in a real-world sense. But if I remember how a craft\'s total drag is determined (the sum of each part\'s rating regardless of position), then the High TWR rocket I used would have also had a higher drag rating than the Low TWR rocket and therefore would have preferred a steeper ascent. But both ended up with the same profile as optimal, though given the fact that my tests weren\'t terribly extensive (six or seven launches each), that conclusion could very well be flawed. Perhaps some further testing is in order... *scratches chin* When you modify your post, there is the option to add attachments. Also, if you have the pictures hosted on a website like imgur or photobucket, you can insert them directly into the post by using the spoiler button (looks like a radioactivity hazard sign) then the image button (looks like a painting). You will end up with this: [ spoiler][ img] link to picture here Also, good job on the 85.5kg remaining! [Edit]: I tried the original craft again without MechJeb. At an orbit of 75,387 x 75,954 I had 88.7kg remaining fuel Of course, without the spaces

Hehe yeah, first time I heard that I thought it was a joke. It\'s one of my favorite classic jets. The 'rocket with a man in it' seemed a pretty appropriate plane to make in KSP. Too bad my version doesn\'t fly so much as goes ballistic

This one should be pretty easy, but it\'s my first accurate-looking replica so I\'m proud of it

Well, after doing several trial launches (nothing so extensive as Zephram\'s ) I found that as far as I could tell, the optimal ascent paths were identical in both the High and Low thrust-weight ratio rockets. The high TWR rocket just burned through fuel too fast. It had a hard time even reaching orbit unless the ascent profile was pretty near ideal. closette- If you pitchover early then reduce thrust through denser atmosphere, you may lessen the force of drag moment-by-moment, but will end up increasing overal drag losses due to being in the atmosphere longer and slightly increase gravity losses due to a slower ascent. Coasting through the denser parts will mean having to spend extra fuel because you\'d end up fighting a certain amount of drag and gravity twice. I have also found that a steeper path out of the air will certainly reduce drag, but will increase gravity losses by even more and typically add some steering losses as well. At least, those are my thoughts based on observations made during my trials in this challenge. Feel free to prove me wrong, it\'s been known to happen ;P Cruisix- You did indeed fair well in your first attempt! Keep in mind that 10kg of fuel goes by in around a second at full throttle (don\'t know the exact time for sure), so we are all pretty close to the same efficiency.

Hmm, you\'re probably right about that. Instead of a two-stage rocket, I think I\'ll test the trust-to-weight ratio variable instead. Have one rocket with a high ratio and one with a low, then see whether their ideal ascent profiles are much different. And I\'ll definitely let you guys know what I find.