GoSlash27

Your numbers from KER are misleading you. FAR requires a minimum of 3,500 m/sec to establish orbit according to the wiki. What was your vehicle's total mass during launch and at cutoff? I'll figure it for you.

'Zackly. Which is why I keep asking for the DV expenditure and why he won't say. If you launch a drag- monster horizontal instead of vertical, then naturally it will lose a little more in drag. Still not enough to cover the inefficiency of going vertical, but closer. And then he launches into his (incorrect) spiel about "terminal velocity" and how accelerating at a kajillion gees is supposedly more efficient... but if that were true, why does his DV suck so bad? I ran the same test with an efficient rocket and efficient profiles, and found a huge cost for going vertical. Best, -Slashy

No, the reason you've reposted it here is the same reason you've been reposting it all these other times; you don't want to accept that your "vertical launch" theory is incorrect. It may be easier and even more reliable, but it is not ever, under any circumstances, more efficient. Now that's 5 times I've asked you for the numbers. We could clear this up if you'd just tell me, but you haven't said what they are. Do you not know, or do you just not want to say?

Yes, that's what I'm asking you. How much DV did your ascents take total? You posted them and you have the video. How much total DV did they take? I posted the numbers for my tests in stock KSP. What were they for your test in FAR?

Your argument is incorrect, so it doesn't matter how much it's "enhanced". This is a very simple matter to correct if you'll just answer the question I've asked you twice: How much DV did it take for you to establish your periapsis? <-- that makes 3 times

This would be resolved by you going back to one of your other threads on this subject where I've already debunked that notion. *this* thread is dealing with airless bodies where "terminal velocity" doesn't exist. And vertical escape isn't more efficient here under any circumstances either. -Slashy

No, we had not resolved this, which is why you now have 3 different threads arguing the same fallacious theory. How much DV did it take you to achieve apoapsis in your tests? *edit* sorry, 5? We're up to 5 threads now? I'd lost count... /edit

Just noticed that the OP was mistaken about a critical item. My numbers were not derived from some software. They were empirical results from actual flights. So when I reported a 340 m/s difference, I wasn't saying that I plugged some numbers into a piece of script and it said "340". I *personally* flew these profiles in a very efficient rocket in KSP and recorded how many m/sec it took. Best, -Slashy

Either a failure to clarify on my part or a failure to comprehend on your part... I'm talking about prograde escape vs. vertical in terms of efficiency. Vertical is not ever going to be more efficient than horizontal. It should be self- evident that smacking into terrain is *not* an efficient escape profile. Best, -Slashy

Yeah, his engines are lit, yet his resource panel shows no draw. I think his infinite fuel is on. Best, -Slashy

Utilitarian. My designs are all about doing the job as reliably as possible with the least fuel and cost. I let form follow function. Best, -Slashy

Well, what I mean is that bit in the middle: "gravity will continue suck down your velocity when going straight vertical". There is no speed at which Oberth suddenly comes into play. The fact that you expended all that fuel at a lower velocity the entire time means that you didn't get as much kinetic energy out of it as you otherwise would have. The fact that you had less velocity at the end of it all also means that any subsequent burns would not give you as much kinetic energy as they could have. Best, -Slashy

Arkie, You missed the actual reason why your vertical profile showed smaller losses as compared to prograde, and I had specifically told you in that thread: You had accelerated at a wastefully- high rate, and your drag losses were exorbitant. This gave you a greater DV drag penalty in the prograde gravity turn than in the vertical, and made the vertical escape seem less wasteful in comparison, when in reality both of your launches were terribly inefficient. How much DV did you expend total in your prograde ascent? *edit* on the subject of munar escape, prograde acceleration as rapidly as possible. Always and no matter what circumstances. Vertical costs you more in gravity losses, robs you of free velocity from rotation, and kills your Oberth effect gains. Best, -Slashy

None of what you said here conflicts with the reasoning used in stock aero, or my own. The change between stock lumberwagondynamics and FAR has not made a change in the ideal t/w at launch. It was around 1.6 before and it's still 1.6 now. I personally use something much closer to 1. Best, -Slashy

You're actually saying the exact same thing I am. In FAR, an efficient launch profile has a gravity kick almost immediately (because more streamlined=less drag=less DV losses) and t/w is still where it has always been; about 2 in theory and lower in practice. Entirely my point, so maybe I'm not the one you should be arguing with Best, -Slashy

This is what I'm talking about; you've conflated the terminal velocity of a powered rocket with the terminal velocity of a falling body of fixed area and drag coefficient. They're not the same thing. The terminal velocity of your ship doesn't mean anything at all in determining the ideal launch profile. What matters is the rate at which atmospheric pressure is dropping. Besides, you can reach terminal velocity in FAR very easily, even in an aircraft that has nearly zero thrust. Just don't climb, and eventually your speed will top out. Best, -Slashy

I assure you I'm not. FAR's aerodynamics do change things fairly radically. All the things you mentioned and more. But it does not change Kerbin. This is a critical point in what I'm trying to explain to Arkie; all of the changes that FAR makes are to properties of the parts, not to the atmosphere itself. The gravity is still the same as it's always been and the pressure gradient is still the same as it's always been. It used to be semi-valid to talk about the "perfect" t/w as being 2 because in that sense an aircraft would maintain perfectly uniform drag. When they spoke of "terminal velocity", they were talking about the atmosphere, not the vehicle. The terminal velocity displayed in KER is of the *ship*, not the atmosphere, and (especially in FAR) it has absolutely no relation to figuring out an ideal t/w on launch. The most efficient launch profile in FAR is not going to be much different than it was all along because the most efficient path off of a planet is determined by the planet itself, not the ship making the trip. You're seeking the absolute minimum drag losses and the absolute minimum gravity losses and neither the air pressure nor the gravity have changed. So there will be differences due to the behavior of the craft, but they won't be huge differences as far as the profile goes. Get into the gravity turn sooner and you might need a little more thrust to get you through the sound barrier. Other than that, it's still the same as it's always been; a prograde gravity turn at 2G (local) initial with the thrust reducing as pitch decreases. It's the same game with every planet with an atmosphere, just as it's the same gameplan with every planet without an atmosphere. Best, -Slashy

All respect, but I'm not misunderstanding it. FAR doesn't change the atmosphere, it changes the parts. The air is not thinner, the parts are less-draggy. The items you mention ( Area and Cd ) are properties of the *parts*, not the atmosphere itself. You hit on it in the last paragraph; "FAR is vastly removed from stock aerodynamics". But FAR's *atmosphere* is exactly the same as stock, so the term "souposphere" is highly misleading. It would be more accurate to say that stock KSP has lumberwagon aerodynamics. Best, -Slashy

Okay, I got official confirmation: FAR doesn't change anything about the atmosphere itself. We speak of the stock KSP "souposphere", but in reality the atmosphere is the same and the *vehicles* are draggy. So in FAR, you're still getting off of the same rock. Same radius, rotation, gravity, air pressure, gradient, and boundary. It's just that your rocket is more aerodynamic for most of the trip and draggier in the transsonic region. Now... attempting to read into terminal velocity in stock is fine, because every vehicle behaves the same AFA drag coefficient is concerned. It's a constant .2. But in your case, your drag coefficient changes radically and thus skews your terminal velocity reading. Were you to drop an object with a constant .2 drag coefficient from altitude, you would find that it falls at the same terminal velocity as it would in the stock game. So what does this mean? Simply that your vehicle is cleaner off the pad, dirtier around Mach 1, and cleaner the rest of the way. It does not, therefore radically alter the ideal t/w or launch profile from stock. It certainly doesn't mean that 5 or 6G acceleration is more efficient. All it really means is that you should do your gravity turn sooner than in stock and that you need more thrust in the transsonic region and can get by with less in the supersonic region. Best, -Slashy

Fantastic! Thanks, -Slashy

I'll need some indulgence here. I'm working to get that pinned down, and don't want to post potentially misleading info based on an assumption. Please bear with me, -Slashy

Sorry, but I need to be very clear on this: what do you mean when you say that? Do you mean that it changes some property of the air, or do you mean that it changes the properties of the parts moving through the air? Sorry and thanks, -Slashy

Because the Vt readout is giving you info about your ship, not the atmosphere itself. If my hunch is correct, I think you've misinterpreted something and it's led you astray. I need that info before I can say for sure. Best, -Slashy

Please pardon me if this question has been asked a million times; I tried to search for it and had no luck. Does FAR alter the scale height and pressure of Kerbin, or does it just alter the aerodynamic modeling? Thanks, -Slashy

Just reviewed the video, and I think I've got it... sorta. What would really be helpful would be to drop that same rocket from space, straight down and record the speed in free-fall vs. altitude. Does anybody have the scale height and surface pressure for the FAR atmosphere? The numbers for stock are 101.3 kPa at the surface and scale height of 5kM Best, -Slashy