arkie87

Fine. I'll post the image gallery, if that's ok... I was having trouble matching numbers with the design i had on paper... my command pod weighed about 200 kg more than what is written on the wiki... i thought maybe 0.90 updated some part specs... but then i realized i had deadly-re-entry installed and command pod had an additional 200 kg of ablative heat shielding .... once i removed heat shield and monopropellant, i matched paper values quite nicely Also, it feels kinda cheaty that all of us are supposed to get a Kerbin capture but none of us have a parachute... i guess, we'll just have to land Jeb on his head... That still works, right?

I actually PM'ed Ferram and he said something along those lines, though i still dont quite understand it... it has something to do with high AoA's being non-linear... I actually tested this just now, and i think you are right-- when i burned with LFE simultaneously, i definitely did not have more deltaV. I suppose it was a stupid question since dropping the giant masses of the humongous SRB's before burning should be seemingly obvious, since it will be pushing less mass. However, pretending I wasnt allowed to drop those, I wonder if the quoted answer in the OP is correct... I suppose your answer #2 was a bit vague and i interpreted the logic/point incorrectly. sorry for that. However, you do admit your #1 point was misinformed I hear lot's of people on the forums say that and I think its a common misconception

I was in the middle of doing this test as well, but then saw this post, which basically said and did everything i wanted to (and more!)...

Once again you misunderstand me. The challenge is to obtain a munar escape vehicle. There is no requirement of how it got there in the first place. Thus, SRB is perfectly feasible... Nevertheless, I'd rather go with LethalDose's design since it is a more feasible design given the spirit of the challenge (and it also perfectly illustrates the point I was trying to make-- so thank you LethalDose, have some Rep!) I will do Lethal's design and post results... EDIT: Nevermind, he already took care of it! Kerbals will not be killed from over-G in stock (you need to have deadly-re-entry installed for that to happen). Plus, even for TWR = 30 on the Mun (my RT-10 design) will result in 5 g's acceleration, not 30... I don't know why you imply that ill murder Kerbals with my designs... Parts only break in FAR from aerodynamic stresses. There are obviously none of those on the Mun... Suggesting I'm enabling cheats that prevent breaking parts from a mun launch indicates you either arent reading what im saying in full, or have a severe lack of understanding regarding the things I am saying... Frankly, I'm not sure which is more likely...

I think the problem is i'm not being aggressive enough with the turn early on, and too aggressive when its already too late. I'll adjust my methods a little bit.

I readily admitted that my RT10 example is impractical, but that wasn't the challenge posed by Slashy. Nevertheless, that is just one example of many I've given. Furthermore, LethalDoses is both practical and advantageous in every way. Second, are you saying that the 487s is better than lv909 as the final stage lifter? Isp difference is 4/35 while mass is only 4/60.? Please explain....

If you answer my questions

Very good point. I dont know why i didnt see that, but thanks for pointing it out. besides, as far as i know (i could be wrong) you cannot place just one LV-1 since it is a surface-attach engine... TWR of 12 is not enough! Let's go to 100 Either way, i think LethalDose and I have provided enough examples that show that it is possible to obtain a higher TWR, deltaV and reduced cost all at the same time. The three are not always mutually exclusive, (since they are arbitrary functions of the part specs in KSP...) On the plus side, this thread seems to be back on track... (not to jinx it or anything)

I know. But that wasnt my question. My question is better or worse than the direct vertical launch? My guess is better, since it is somewhere in between vertical and horizontal... Maybe it will only cost 10% more...instead of 20% A good measure of how good your gravity turn is is horizontal velocity at apoapsis... do you by any chance know how much horizontal velocity you had by the time you got to apoapsis? Or alternatively, the approximate angle your prograde vector had with the horizontal... i can never get mine anywhere near 45 degrees with my rockets when i try a gravity turn... Is that what you found too? If so, why wont my rockets do a gravity turn... By atmospheric efficiency you mean terminal velocity, i presume? And it sounds like you had more fun using my rocket

Yeah, but in stock the extra dV is gonna be a lot higher since terminal velocity is a lot lower... Our dV's are within 2.5% of each other... But i see your point... if 20% is too much for you, then it's too much... I'm not saying its not for me, but at present, since i cannot do a gravity turn in FAR reliably, 20% extra might be worth it to not kill Jeb.

Why is it cheating? If you want, he could "attach" it with a strut or two... no need for a full fledged decoupler though, since it will be decoupled with the stack, not individually.

An alternate launch approach I would like to investigate is first using a stage (or two) to blast vertically out of the atmosphere, and then burning horizontally into orbit, and then periapsis transfer to Mun... (i.e. "the gravity turn" that couldnt or didnt happen in atmosphere) What do you think of that? Will extra cost be more or less than straight vertical approach? Also, have you tried flying my craft horizontally? Does it work for you?

That is all true. But when conventional wisdom says "vertical is much worse" I dont think they mean by 25% or 33%. I think they mean by 100%+, no? Besides, I might have an idea or two of how to further improve it... And regardless, I have mentioned other advantages that vertical might have over horizontal, such as, (if it's stable during ascent) it is more foolrpoof/harder to mess up, but maybe i just need to learn how to do a proper FAR turn...

As another example, if you have a vehicle landed on the Mun made out of Mk1-2 command pod and a rockomax X200-16 fuel tank, what engine should you strap on it: The two most obvious are Rockomax 48-7S and the LV-909. In this case, the lighter engine does not result in more deltaV due to it's reduced ISP. Furthermore, in this instance, choosing the LV-909 results in both more deltaV and more TWR, which is why it is a good example...

Even in terms of burn time, RT-10 is better: Two RT-10's have more thrust, but reduced burn time. Even if you reduce thrust such that thrust is equal to that of one BACC, burn time will still be faster, which means you can drop the mass earlier...

Against my better judgement, I am going to post these results. The top part is your results, the bottom is mine: My design is cheaper, has more deltaV, and higher TWR... (high TWR enough, in fact, that you would kill your kerbals with the acceleration), and I can even forgo some of the fuel mass since i dont need all that deltaV, which would make my design cheaper still... Now granted, it is a solid booster, so you cannot turn it off mid burn, so you would have to land it on the Mun with something else that you would jettison; however, that wasnt part of the problem description. For a heavier lander, this type of vehicle might be more practical...

I dont think that link worked the way you intended... but i'm glad you understand my sentiment.

That is a factor as well, but I am approaching from a theoretical standpoint, not necessarily a practical one. I am wondering if maybe the science labs are a better home for my threads... since i am more interested in the theory than the practice Speaking of which, i was wondering what about FAR's change in aerodynamics makes rockets unstable. I'd prefer as specific/detailed reason as possible, not just something vague like it changes the aerodynamics. I imagine it has something to do with the changing lift and drag coefficients vs. AoA, but i cannot figure out how this would make the vehicle flip around, rather than get forced back to pro-grade direction...

Can you please repost your lifter design? I want to design my own (on paper). Just to clarify, we are referring to your craft taking off from the Mun, leaving Mun's SoI such that it gets an aerobreaking encounter with Kerbin, correct? Edit: nevermind. I found it.

Are you sure its linear with Data? Shouldnt it be Data^2?

I appreciate your desire to help and willingness to do so until you give up in exasperation. I recommend you have a look at http://forum.kerbalspaceprogram.com/threads/103449-A-New-Thread-to-Discuss-5thHorseman-s-Challenge as well where i have provided a 11 k$ ship which can do the same task as 5thHorseman's 9k$ ship (which is only 20% increase in price...), so while you might believe vertical ascent is much worse, that thread provides information that says otherwise. I do appreciate you actually quoting my position more correctly (i.e. saying that vertical launch might not be so bad vs. saying that it is always better). If you read the OP, you will see that I do not actually have an opinion. I am looking to find more information, not expressing an opinion. I will readily admit that the problem can potentially be on my end. But i read, and re-read your posts before i respond. When i respond, i cite what i'm responding to so there is no confusion and try to be clear as possible. When i get my responses (from you, and plenty other), i see things that immediately indicate to me that the responder did not accurately read my statements (like the whole confusion over the mun lander vs the horseman challenge which i repeatedly tried to clarify...) or that discredit my arguments without giving any reasoning. In general, I've noticed you dont provide counter arguments, just counter-opinions. Even if these opinions are correct, you seldom provide proof to back them up. If the logic i present is wrong, explain what is wrong about it, not merely *that* it is wrong... i dont really understand why this is so hard to understand or accept....

Yes, i built an 11k$ ship with nearly the same performance. http://forum.kerbalspaceprogram.com/threads/103449-A-New-Thread-to-Discuss-5thHorseman-s-Challenge

Not sure what you are trying to add that wasnt already said by me or someone else, but i think it seems like you are agreeing with me, so i'll take that... Anyway, the first two points made by Starman are flawed: (1) Reducing thrust when below terminal velocity is not optimal (2) If the drag is so low in FAR, then that is a reason to TURN ON the LFE, not leave it off...

Yes, exactly. i might try to think about this... but i suspect there is no analytical answer i.e. it requires numerical simulation (for which, i have already made one in Matlab-- i assume you snicker whenever you hear matlab, since you studied scientific computing hehehe)...

Thank you for actually addressing and answering the question I asked. So it seems like firing up the liquid engine during ascent will be beneficial... Thanks!