qoonpooka

Yeah, I've been doing the 2-degree tip at liftoff since I read that this is how you gravity turn, but then non of my rockets have ever kept tipping. I try to do it slowly, to keep my thrust aligned with my prograde vector, but this seems to involve me not turning fast enough because I wind up with a very steep rise to apo, and exactly the long coasting period you describe as Verrah Bad. I wonder if turning off SAS would let the thing tip on it's own better? But you also say that this is probably the least of my problems so I'm trying to focus elsewhere. It sounds like I may need to just swallow the (much) higher pricetag of liquid stages for lifting and save solids exclusively for kick-starting. - - - Updated - - - https://drive.google.com/file/d/0B7Rn2EgE0DrDYnBUbG9uaU1WcW8/view?usp=sharing Not sure if google drive is the best way, but Dropbox wants money.

I'll give the thing a tweak to 1.7 TWR for the BACC and 1.5 for the RT-10 and report back. Thanks for the advice! EDIT: Did so. Results were uninspiring. So I set the boosters to 1.7 and 1.5 TWR and started my gravity turn gently at 500m. (It takes forever for this thing to pitch over, no fins on it, so it's all the capsule's torque). 45 Deg @ 10k, basically flat @30k....Apoapsis never got above 55km. Ran out of gas @ 32km and drag did the rest. Trying a stronger 'souposphere' stage and toning down the 2nd solid. 2nd EDIT: Same results, except this time, as I'm burning horizontal @30km, my apo is falling very slowly. My prograde direction of flight is horizontal when my thrust is 45-degrees. am I misinterpreting instructions about 'flying horizontal' here, and I should be parking my prograde indicator there? Or my nose there?

This suggests, since I'm using solids, that I'm just gonna lose a ton of dV to either drag or gravity, since I can't throttle them?

My dV map says LKO, in stock, is 4,550 dV. I'm trying to efficiently park a command module in orbit to some early-career science. I've parked satelite contracts around the Mun, landed on the Mun (didn't have enough fuel to escape again, though. R.I.P. Jebediah Kerman), etc. I'm guessing I usually make up for my craptastic launch piloting by my ability to put every maneuver node I fly to 0.0 m/sec without overshoot. So the current vehicle consists of two vertically stacked SRBs (BACC initial stage, RT-10 2nd stage) and then 3.5tons of final stage including a -909, T200+T100 fuel, science jr, quad landing pods, capsule, mk-16, one PV panel, and a 2HOT. KER says 4,878 dV. By my understanding of the dV map, this should give me 328 more dV than I need to attain a 75km orbit. I launch, @2km alt I tip about 2 degrees to start the gravity turn. The rocket does not keep tipping. @~10km I ditch the BACC and light the RT-10. Now I'm tipping the rocket manually towards 45-deg as I accelerate. RT-10 quits @~25km and I light a full-throttle -909. At this point my Apoapsis is nearing 75km so it doesn't need to burn for long. I set a maneuver node for a prograde burn at the Apoapsis to circularize. Burn time comes up: 1m 52s. I have barely that much fuel full. As I climb to apo- my velocity is dropping into the 600m/sec range, and I end running out of fuel before I'm anywhere /near/ circularized. 4,878 dV becomes a suborbital flight. I'm pretty sure I'm flying the ascent wrong, but I can't find any guidance for getting to orbit efficiently - just people saying 'add moar boosters.' Is the dV map wrong? EDIT: Great analysis has helped me adjust the thrust on the solid stages, and change how I'm gravity turning. I was, apparently, making the turn 'too perfect' for stock's drag model as one of my errors. The rest was just the fact that solid boosters are crap and throw off the delta-v calculation in KER.

Ah well. Thanks for the tips, guys. Super helpful. I've got a plane in the air as an engine test bed now, got these contracts done, and I'm being pickier about how I choose them, now.

Awesome, thanks for the tip. The remaining part of my question, then, is if there are tools for, or a tutorial for the maths involved in, predicting a rocket's speed and altitude at any given point during an atmospheric ascent so that I'd know where/how to tweak the thrust before I launch the thing.

Adding to the praise here: The knowledge of both Kerbin aereodynamics and the terran 'model' is plain, the pics are charming, the explanations are useful and replicable. I'm now totally stoked to to go build some aircraft. The only thing I could wish for in a future edition is coverage of payload and fuel considerations. I know, e.g. that rocket fuel tanks are a waste because they pack oxidizer, so how do you build aircraft for longevity inflight, high-capacity hauling (for testing parts under certain conditions etc)... but I'm thrilled to have come upon this guide.

Bah. Thanks for the mis-filing tip. I think I got lost in my searching to see if my question had come up before and didn't remember where I was. My problem, ironically, isn't that the rocket can't make speed. It's actually making speed round 5-6km, and then going too fast through the entire bracket. I might not have described this correctly before, but essentially I hit the speed green-check and then the altitude green-check flicks on just as the speed one flicks off. Normally I'd tweak down the boosters, but kicking out solid boosters while they're under burn destroys everything but the command module in the best of times. I've tried a number of ways to keep the solids away from the main body and coasting to the target (collision/explosion), as well as reducing the solid stage and going with a lower-powered liquid stage (not enough power) to get there. The aircraft suggestion is probably the way I'll have to go. I've never done aircraft design, but then I guess I can grab those visual survey contracts too.

So I've got an example contract, test the -45 liquid engine between 7km and 11km altitude, activating it through staging while at a speed between 300 and 400m/sec. I've built an orbiter that'll complete another contract (get into orbit) and figured I could mod that to also do this engine test since the -45 is perfectly fine for final lift into orbit. I've got 4,700m/sec of Delta-v which is enough for a basic orbit and then some... For the life of me, I cannot get a combination of engines that will get me that altitude and speed combination. The closest I've come is three RT-10s, which get me almost there, but the speed and altitude is wrong and popping those things off under burn is bad for mission health, so throttling them down is no good. Are there tools out there for helping someone figure out delta-v requirements to put a rocket into the conditions required to do these early in-atmo contracts or are they just a waste of resources?