mknote Posted July 11, 2012 Share Posted July 11, 2012 I\'ve been attempting to make a space shuttle similar to the real life version in KSP. I have spent over five hours working on the thing, and I still can\'t get it into orbit. Frankly, it\'s starting to kill my interest in the game, and I don\'t want that to happen, so I decided to bring it to the experts here on the forums.I\'m using both NovaPunch and MechJeb for the shuttle, as it looks rather silly for the shuttle to bolted to the minuscule stock fuel tanks. I\'ve made a slight alteration to the config files that anyone who downloads the craft files needs to take note of. Specifically, I\'ve made two parts (NP_3m Decoupler and NP_miniDecoupler) to have fuelCrossFeed = True.The main problem is stability. Up until about 30-50 km into the ascent, everything is kosher; it\'s wobbly, it deviates from vertical no matter how hard you push it to stay vertical, and it takes on inclination like nobody\'s business, but it gets there nonetheless. Then it starts to tip. It does this because of the decreasing mass of the main fuel tank due to the fuel being exhausted.I suppose I should go into a little history of the development of the shuttle. This might be a little long, and I apologize, but I think it\'s a bit important. The first design flipped on its side as soon as it took off, nose-diving into the ground after about 20 seconds; the shuttle was way too heavy. So I added a counterbalance to the other side in the form of a modified AR202 MechJeb with a mass of 50. That worked... for a while. I eventually became frustrated enough that I removed the counterweight and added liquid engines to the orbiter to counter its weight, which is how the current design is. It was still tipping, however, so I added a decoupler to the large engine attached to the fuel tank, and it started tipping the other way, so I added liquid radial boosters to try and counterbalance. The radial boosters either didn\'t do enough or did too much, so I decided to ditch the main fuel tank when it started tipping and just use the orbiter engines to get to orbit. Everything up until now is my Shuttle 2.craft.So I added two fuel tanks in place of some engines that I originally meant to deorbit the shuttle, along with fuel lines to pipe the fuel to the orbiter\'s engines. However, the fuel logic decided that the orbiter\'s engines would draw from these fuel tanks before the main one at the beginning of the mission, leaving me with no fuel once I separated the main tank. So I disabled them at the beginning of the mission... which permanently disabled the fuel lines > Frustrated to no end, I closed KSP and came here to ask for help.I\'ve attached a few screenshots and the Shuttle 1.craft (which is my latest work on the thing) and the earlier Shuttle 2.craft. I\'m pulling out my hair at this point, and any help would be appreciated.By the by, I also noticed something while testing: while the orbiter would go off course upon launch, if I ended the flight and clicked restart launch, it would stay perfectly vertical. Link to comment Share on other sites More sharing options...
ToadDude Posted July 13, 2012 Share Posted July 13, 2012 I\'m not sure if I completely understood what you were asking, but it sounds like your Shuttle is tipping, correct? If so, you need to make the center of Gravity in the space between the large tank and the Shuttle Plane part. (I\'m on my iPhone so I can\'t download it yet, or see the pics) The easiest way to do this is make the Tank and the Shuttle even in weight. This is probably hard to acheive, so if you add a weight on the other side of the shuttle, and make it be de-staged at the same time as the tank. For example; if your tank weighs 100 units (once again, just an example) and your Shuttle weighs 75 units, create a weight of 25 units. Sorry if this isn\'t your question, but I hope I helped one of your problems. Link to comment Share on other sites More sharing options...
ModernArc Posted July 13, 2012 Share Posted July 13, 2012 If it is tilting the way the Shuttle is, then I know this isn\'t realistic, but I would put a SRB on the Shuttle itself. Making more thrust on the side it is tipping. Then simply add a decoupler. You never said what way it was tipping. So, I hope this helps. Link to comment Share on other sites More sharing options...
MaxMurder Posted July 13, 2012 Share Posted July 13, 2012 Shuttle designes are really hard to pull off... the problem is that as your tanks empty your center of gravity shifts horizontaly. My IRL inspired designs would fail in the same way. Theyd be great up to about 50k then flip like mad. The key is symatry... rather than have on large fuel tank strapped to the bottom of your shuttle (or a shuttle strapped to the side of a rocket in your case). Strap two tanks and boosters to the top and bottom or the sides, and have them drain symetrically. That way your center of gravity will be much more stable and not lead to tipping. It wont look much like the IRL shuttle but it will be alot easier to fly! Link to comment Share on other sites More sharing options...
mknote Posted July 13, 2012 Author Share Posted July 13, 2012 It wont look much like the IRL shuttle but it will be alot easier to fly! :I can get a spaceplane into orbit - even with stock parts - just fine. This was a challenge to build a space shuttle that looked and acted like it\'s real-life counterpart; to do as you\'re suggesting would defeat the entire purpose of me building it in the first place.I\'m no slouch at physics; I\'m getting my baccalaureate in physics a week from today, and I\'m headed off for my Master\'s and eventually Doctorate in the field. I had surmised that the problem was a shifting center of gravity - I\'m trying to correct for this shift, either by liquid booster placed around the assembly or just getting rid of the entire fuel tank at the problem point. It\'s obviously possible to get it working - the space shuttle launched perfectly 134 out of 135 times in real life (135 out of 136 if you count Buran).The problem is thus:At launch, the orbiter and the fuel tank stack are rather evenly balanced in weight. As the main fuel tank empties and the SRBs are jettisoned, however, the decreasing mass of the fuel tank stack (and no corresponding mass decrease on the orbiter) causes the engine underneath the fuel tank to tip the formerly vertical assembly over towards the orbiter, essentially turning the orbiter upside-down. To compensate, I jettison the primary engine, but this only causes the assembly to flip the other way - the orbiter is now the only source of thrust, after all. This would be good, as it gets the orbiter right-side up, which would allow me to achieve orbit... if the damn thing didn\'t keep tipping until I\'m doing rolls at a frightening rate, eventually tearing the entire ship apart if I leave the thrust up.Now, if I jettisoned the main tank at this point (it still has 1/3 of its fuel left, but oh well) and used the side tanks to control my orbiter\'s engines, I could make orbit at this point, but as I stated in my first post, these tanks drain first. Thus, I disable them... which wouldn\'t be a problem if it didn\'t permanently disable the fuel lines connecting it to the orbiter, causing me to have no fuel after I jettison the main tank. More succinctly, if I don\'t disable the tanks, they drain and I have no fuel, and if I do disable them, the fuel lines won\'t work and I have no fuel. Damned if I do, damned if I don\'t. I\'m hoping there\'s a way around this bug (and I\'m sure it\'s a bug), but if not, I\'m really out of ideas. Link to comment Share on other sites More sharing options...
E. F. Kranz Posted July 14, 2012 Share Posted July 14, 2012 It\'s tough, because there are three distinct flight modes.1. Orbiter, with external tank and SRBs attached.2. Orbiter, with external tank attached.3. Orbiter.It takes a lot of work (and planning) to control a craft through those three modes.Took me several hours to balance this design and learn to fly it.It will make orbit without ever touching a drop of its onboard fuel. Link to comment Share on other sites More sharing options...
MaxMurder Posted July 14, 2012 Share Posted July 14, 2012 Wow! now thats a sexy shuttle!My design is much simpler (and probobly easier to fly lol).It launches with top and bottom mounted boosters, wich will take it into space. The launch boosters run out of fuel moments before the craft becomes orbital. It is 100% clean of orbital debris.The shuttle is desiged to get to LKO only, just like the real suttle. It dosnt have much onboard fuel, enough for minor plane changes and deorbit. Most on orbit menuvering is done with RCS.It is able to make a successful docking with the KSS. The kerbals on board will be glad to get home. The KSP desided to send up a space station before building a way to get them back...After seperating from the Station the shuttle makes a deorbit burn, using the rest of its fuel. After that it is an unpowered decent into the atomospere. Finally making a landing at realitively near the KSC runway. It is a dream to fly, and ive only had a few challengers. Link to comment Share on other sites More sharing options...
Millst0ne MK II Posted July 14, 2012 Share Posted July 14, 2012 That looks terribly ugly Max. I\'ve never made a working shuttle, so good job though! ;P Link to comment Share on other sites More sharing options...
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