GoSlash27

Data, data, data! http://s52.photobucket.com/user/GoSlash27/slideshow/KSP/munar%201 Vehicle cost: $1,188 Vehicle mass: 1.39 Tonnes Supplies expended: Fuel: 33.77 units, Oxidizer: 41.27 units Cost of supplies expended: $27.02 fuel, $2.47 oxidizer= $29.49 Mass of supplies expended: 0.32 tonnes DV to achieve Kerbin periapsis from trailing edge munar surface: 881 m/sec. Bonus: Kerbals killed from over-G: 0. Cheats enabled to disable breaking parts and killing kerbals because I'm accelerating too hard: 0 craft file: http://wikisend.com/download/411660/munar1.sfs Best, -Slashy

Yes, you're correct. My payload will be a Mk.1 lander can, and I will launch it from the location you described on the munar surface. The equipment to place it on the surface and the solar panels will not count towards the cost of the vehicle (unless you just want to include that in the mission profile). Right now, the design is simply a mk.1 pod, t-100 fuel tank, and LV-1 engine, but I may revise the final design to de-pork it a bit. The only requirement for the lifter itself is that it must have a manned Mk.1 command pod and the only stipulation for the test is that debug menu options and kraken drives are illegal. I think that covers it... Best, -Slashy

Fyrem, Sure thing. I'll get it posted here this evening, along with pics from a mission and all figures. Best, -Slashy

arkie, I absolutely agree that we aren't communicating well, but I'm going to continue to participate in your threads until I finally give up in exasperation. *somebody's* got to counter this notion that vertical launch ain't so bad. Now... you've had a lot of people come in here and attempt to explain to you why this whole approach is borked, argue around in circles, and eventually give up in disgust. Are you really certain the problem isn't on *your* end? I mean... just as you get the impression that I'm not reading your posts, I get the impression that you simply don't want to hear any counterarguments. It's not like I have these miscommunications often, but you have had them ongoing in these threads with a lot of people besides me. Isn't at least theoretically plausible that maybe you're not conveying your meaning very well? Sorry -Slashy

Sorry, but that thread has no bearing on this discussion. If you believe that you can make a vertical lifter that is "competitive" in any way, shape, or form to what I have already presented here ($1688, 45 units of fuel burned, total mass under 1.9 tonnes), then by all means, have a go. I think you've over-analyzed it pretty badly if that's the case. Any DV chart will tell you that 850M/sec is plenty for this job. You also know that escape velocity for the Mun is 807 M/sec. Knowing that your goal is to achieve escape velocity and knowing that the gravity is robbing you of 1.63 m/sec during the duration of the launch (1G), you're asking at what point a vertical launch can achieve 850M/sec total expenditure or less. This is actually a very simple problem to solve. (x+1)/x*807=850 Simplifying this to solve for X is x= 807/43, which is 18.8:1 t/w. At that t/w, it will cost you 850 m/sec to achieve escape velocity. As t/w approaches infinity, DV approaches 807. You're welcome I swear I don't mean to be a bastage when I say this, but yeah, you're doing it wrong. Climbing straight vertical and then circularizing is incredibly inefficient. This is actually the same point as the first, and already answered. Whatever payload you choose, you can't make a booster that will launch it at 18.8G that can compete with the mass, cost, and fuel burned by the conventional method. Below this acceleration, you're still heavier, more expensive, and wasteful, but in addition you're wasting DV. Best, -Slashy

Although to be honest, the only time I ever use it now is when I'm working a quick side- calculation and I want to look at a ratio problem because it allows me to see all possible solutions at the same time. Somebody stop me before I calculate again!! -Slashy

Yessir, I've got that... but all these other factors are critical to the comparison between the two modes. I understand you think you've yourself a favor by eliminating the characteristics of the vehicle itself from the analysis, but in doing so you have eliminated all *practical* vehicles from consideration. Your analysis, mathematically rigorous as it is, boils down to this: "If stranded on a desert island, there may be some case where there's a more efficient way to open a coconut than banging it on a rock. You could, for instance, bring an elephant along with you. The math shows that the larger the elephant, the more efficiently it can open a coconut." I think the reason this gives so many people so much consternation (myself included) is that you speak of metaphorically "bringing along an elephant" and efficiency as if they are not mutually- exclusive concepts. Stepping back out of the analogy... Your analysis completely stacks the deck in favor of vertical mode by assuming a vehicle optimized for it while rejecting a vehicle optimized for horizontal launch and erroneously concludes that "there's not much difference between the two modes". You cannot compare the relative merits of the two modes fairly without comparing *all* of the merits. Vertical launch is easier, while horizontal mode saves DV, weight, cost, and fuel. The difference between the two modes *in total* is not minor in any of these categories. Vertical launch from the munar surface is not the preferred option *under any circumstances* from a mission planning, engineering, or fiscal standpoint. As for LD's analysis, the holes in his thinking are threefold: 1) ^This 2) The t/w of the vehicle increases over time as fuel is consumed. and 3) The pilot is going to vary the pitch of the vehicle over the duration of the launch, not keep it at a fixed angle. Best, -Slashy

Rocketeer, Actually, it's still more efficient to launch horizontally from the trailing edge. Doing so will put you in an apoapsis with near-orbital velocity overhead the leading edge, with only a small burn necessary to escape munar SOI. This is still a cheaper proposition than burning vertically from the trailing edge. Were one to increase the t/w enough, I think eventually you could find a point where vertical launch is competitive. Reduced eccentricity due to having been in near-orbit and a small loss in Oberth effect for having drifted to the apoapsis do create a small, but tangible loss in efficiency. I don't believe that they are large enough to overcome the 9m/sec advantage from having launched with the surface rotation, but I might be mistaken on that point. Assuming I *am* mistaken, then it is theoretically possible that, with enough thrust, one could design a vertical launch vehicle that could edge out the horizontal mode total DV... But that point is moot because nobody would ever design such an inefficient vehicle, drag it's bloated carcass to the mun, and wrestle it down to the surface. Best, -Slashy

I'm not sure what the heck he was saying, other than he clearly doesn't like me (not an unusual circumstance ) My entire point (and you may as well get in on this) is that a vehicle that departs the Mun eastward with sufficient DV to return to Kerbin can easily be made for $1,688 (not bothering to drop the cost for 5 solar panels), carrying 45 units of fuel, weighing 1.9 tonnes, and capable of achieving 1,290 m/sec DV can be easily created just by using a Mk.1 command pod, an FL-100 tank, an LV-1 engine, and a handful of solar panels. There's no vehicle, no matter what the acceleration, that can get anywhere close to these figures when designed to depart upward, so speaking of the efficiency differences as if they are "minor" is frankly bizarre. And this craft isn't even optimized to the task. It's got way more DV than the mission calls for and the Mk.1 pod isn't the most efficient option. The math would be DV=9.82*290* ln(1.39/.890)= 1270 and T/w= 4/(1.39*1.63)= 1.77 The in-flight test is that I slapped it together, hyperedited it to LMO, and was able to land it on the surface with about 1/3 of it's fuel still in the tank as proof-of-concept. That, and the fact that people use this combo *all the time* for this job. So unless there exists a high-g vertical munar departure vehicle that can get anywhere near any of these numbers in any category.... what do we mean by "marginal" when comparing the efficiency of the two departure modes? As a practical matter, they're not even on the same planet, let alone in the same ballpark. *That's* what I'm saying. Best, -Slashy

haha, Oh, God! My house is *littered* with papers like these! Sketches, DV estimates, notes... It's frankly embarrassing... The first step is admitting you have a problem... -Slashy

LD, Fair enough. You and I simply won't converse. I think that's best for all the users on this forum. But a Munar ascent vehicle that falls within the limits I outlined isn't "boastful", it's common practice. Not even optimized. If you slap together a Mk 1 command pod, an FL-T100 tank, and an LV-1 engine, it's completely adequate to get you back to Kerbin from the Munar surface with plenty of DV to spare. Not like that's any huge engineering miracle. There's no high- acceleration monster that's ever going to beat that in a vertical departure when it's departing east for any measure of efficiency. It's lighter, cheaper, burns less gas, and expends less DV. A *lot* less in all categories. Sorry we couldn't get on the same page, -Slashy - - - Updated - - - Agreed, and no hard feelings. All it *really* means is that we miscommunicate frequently I will leave you and 5thHorseman to sort out your challenge. When you want to discuss vertical vs. horizontal munar departure, I'll pick it up there. Best, -Slashy

Yes you did. *After* you had already concluded I was trolling you and berating me for it, not before. At the time, I was operating under the assumption that you were referring to a departure from the Mun, which is not unreasonable given the vague nature of the post and the topic of this thread. Not belaboring the point, just making absolutely sure that you understand: I've got better things to do with my time than troll you. If you're under the impression that I'm doing that, then it's due to some confusion in our communication, *not* an intentional effort on my part. Best, -Slashy

Aye, and I read it in full, but if you read it, you will see that there's absolutely nothing in there that would lead a reader to conclude that you were talking about departing from Kerbin instead of the mun. Easy mistake to make, given the circumstances. Best, -Slashy

LD, I will happily go through this with you, but if we are to do that, you *must* drop the attitude and conduct yourself in a civil manner. If you can't/won't do that, then I'd just as soon spend my time doing other things. Now with that said, I was not asking you "have you ever launched eastward from the munar surface" trying to be snarky, I wanted to confirm that we had a common basis for understanding, so that we both understand that leaving the surface vertically, then rotating Eastward is *not* a mutually exclusive concept. You have done it yourself, so when I say "leave the surface vertically and depart east", we should not have any confusion about what that means. You attacked me for saying that, as if I can't do both. Now clearly, *you* were referring to something else entirely when you read that, and I'm not sure what it is, but I *suspect* that you were referring to some scenario where you leave the surface heading eastbound and assumed a constant pitch. Now... I promise to be civil and respectful and I ask that you do the same. If you're cool with that, then we can proceed. Best, -Slashy

arkie, Welcome back. Okay, cool... that whole "5th Horseman" thing is between you two and since it requires FAR, I'll happily butt out. But in my defense, 1) You were the one who mentioned somewhere (forget which thread) citing your earlier statements rather than telling someone else to find them and 2) the phrase " We have a lander craft that must be lifted to orbit around the Mun." is sufficiently vague as to make someone *think* that you were referring to the munar surface, given the topic of this thread. I'm trying to follow you here as best I can, so please bear with me. Regards, Slashy

Dammit! Arkie's offline. LD, how would you like to proceed? Do you want to discuss the subject that you and I were discussing in the meantime, or table it? We were both on the same topic (munar surface to Kerbin)

LD, Please hold until Arkie responds so we can all get on the same page. I think you and I are talking about the same subject (escape from munar surface to Kerbin), but I don't think he was. Patience, -Slashy - - - Updated - - - Okay, good. So now let's wait until he responds so we're sure we're not getting crossed-up here.

Fair enough. I don't know what *that* subject has to do with the OP in *this* thread, so please excuse my confusion. Arkie's got a bunch of different threads on this same subject (vertical escape vs horizontal) and I'm having a hard time keeping them all straight, especially when the topics don't match the subjects. Best, -Slashy

LD, Full stop for a second. I don't think we are all on the same subject at the moment. See my previous post. Exactly what are we discussing right now? My impression is that it's getting a lander off the surface of the Mun and back to Kerbin as efficiently as possible. LD, what are you talking about? Likewise you, Arkie.

No, scratch my previous post. *THIS* thread is about your proposed munar departure. Check your OP. Seriously, too many different threads on the same topic and you're confusing yourself along with the rest of us. Your OP in this thread. This one ain't on me, -Slashy

Wait, Scratch everything I've said in the last couple pages. *Which thread are we in again??* Dude, this is too many different threads on the same topic. Is this one about escape from the Munar surface, or escape from Kerbin? I thought this one was about escaping the Mun. I think this is the source of the confusion... -Slashy

All, I have to assume that the failure in communication is on my end. When I say "Launch vertical", I mean that the rocket departs the surface vertically. When I say "depart eastward", I mean pitch eastward after having left the surface so that the vertical component of thrust balances gravity and the remainder is used to accelerate eastward (clearing terrain as necessary) until apoapsis is achieved. I *HAVE* to assume that you guys are talking about something else entirely and I'm just not getting it.

LD, Have you ever launched a lander off the mun? If so, did you launch it vertically and pitch eastward like everybody else? I ask this in all seriousness because I can't fathom any other reason why any of this would puzzle you. Believe me, I'm not assuming that you're clueless. This *HAS* to be a failure in communication. Truly confused now, -Slashy

No, the challenge is to get *your* lander from the surface and place it in munar orbit. (Honestly, I thought that it was to get a reentry to Kerbin). If it's just getting *a* lander, then *OF COURSE* it can be accomplished at my price point, and below that if it's just orbit. Not like it's hard; you'd have to search far and wide to find a lander that someone put on the Mun that was anywhere near $10,000, because nobody would ever over-engineer a lander that badly unless they were just plain awful at engineering. I'm surprised this shocks you, -Slashy

I understand all that, but he's wasting his time. You are not constrained to maintain a single pitch angle during a launch, and your t/w increases as fuel burns off, so launching at 1G vertically means that you *will* rise from the moment the first molecule of fuel meets the first molecule of oxygen. You don't need a huge t/w to get off the mun in an eastbound trajectory, and everyone who's ever played KSP already knows this. Scratchin' mah head, -Slashy