capi3101

And you do that.........how? I'm not trying to be smart; I genuinely would like to know how to do this. Let's go with the demo. Kerbin, Mün, Kerbol. On my map, I want: a) delta-V required to make Kerbin orbit delta-V required to transfer to the Mün c) delta-V required for Münar orbital insertion at 14 kilometers d) delta-V required to land on Mün. Now, I assuming the Hohmann Transfer and Orbital Velocity equations in the wiki's Advanced Rocket Design tutorial have something to do with this, and so what you would need is the distance between the two bodies, the radii and their respective gravitational parameters. Some other factor is involved with Kerbin launch though (the atmosphere, I'd wager), which is why it takes ~4550 to make orbit instead of ~2250. Is that even remotely close to being correct? Can anyone walk me through the calculations?

Yeah, this thing has pulled to the side during take off before, usually to disastrous effect (the "too low to eject" kind). That's not a consistent problem, though.

So how does one go about calculating the numbers to place on the map? I assume that NASA had some notion of the delta-V requirements to make a full trip from Earth to the Moon, or to make a trip to LEO. Hell, I imagine the Soviets had some notion of what they needed for Sputnik I... Seriously, does anybody know the methodology involved? I'm with the OP - I'd like to know how it's done.

D'OH!!!! Well, there's a novice mistake on my part. Thanks. I imagine that's why the center of lift indicator also has a slight tilt to it as well. Okay...what exactly would twisting the gear 180 degrees do? I see where that would put the wheels themselves in closer proximity to the center of mass...is that the idea? Well...the elevons are probably about as far from the center of mass as I can comfortably get them. I suppose I could adjust the position of the stabilizers, but they're more of a rudder than anything. "Control surfaces -to- lifting surface ratio". That's a new one; could someone help explain it? How much lift do you really need anyway? I haven't found much in terms of guidelines on that topic. Alrighty: summing up the suggestions so far -- I'm at work now; won't be able to try these changes out until after I get home later tonight (probably around 02Z) Also, would there be any benefit to putting more distance between the back wheels? I know that a wider axle track makes a rover less likely to flip - can the same be said for aircraft? Not that big of an issue; just curious...

OP: You're missing standard gravity in the equation you wrote down in the original post - it should read: ÃŽâ€v = ln(Total Mass/Dry Mass) * Isp * go That might explain some of the problems you've been having with getting correct values. And you usually just press the ln button once you've got the mass ratio calculated. For example: lessay you've got a Mk16 Chute, Mk1 Command Pod, LV-T30 and 9 FL-T200 fuel tanks in your rocket. The chute weighs 0.1 tonnes, the command pod is 0.8, the LV-T30 is 1.25, and each tank is 1.125 tonnes full and 0.125 empty. The total mass of the rocket full is therefore 12.275 tonnes, empty it's 3.275 tonnes. The launch Isp of the LV-T30 is 320 So you just plug all that in: ÃŽâ€v = ln(Total Mass/Dry Mass) * Isp * go ÃŽâ€v = ln(12.275/3.275) * 320 * 9.81 ÃŽâ€v = ln(3.74809) * 320 * 9.81 ÃŽâ€v = ln(3.74809) * 320 * 9.81 ÃŽâ€v = 1.32125* 320 * 9.81 ÃŽâ€v = 420.79898 * 9.81 ÃŽâ€v = 4,147.658 m/s And there you go. Incidentally, you'll wind up with slightly higher delta-V than this in practice, and that's because your Isp is in fact going up as you ascend. The design I described actually has the delta-V necessary to obtain a stable orbit with enough leftover to de-orbit afterwards. Take that rocket, aim it poleward, do EVA reports as it passes over various biomes and you've got yourself a Tier 0 single-stage rocket...not quite reusable as you will crunch the engines and a few tanks on landing, but......

Evening all. Tonight I launched my first successful SSTO spaceplane, the mighty Auk I: Pretty much a no-frills spaceplane, though it does have an ejectable command section for emergencies, a probe core for unmanned flight and a reaction wheel for better overall control (which I'm not convinced is necessary/useful for the design I have). She made orbit and I even managed to land it back at KSC intact (at night no less and in a save game without my ground beacons) afterwards. She had achieved orbital velocity around 30,000 and still had some minimal thrust capability on the jet around 50k. I do have a problem with the design, and it's one that I need some help overcoming. I can't get this thing to take off prior to reaching the end of the runway. I mean, she'll accelerate the whole way but I can hold down the S key to no effect until after the runway drops out from beneath me. She flies great after that point. So how do I set it up so she'll take off sooner? Also, what's up with my center of lift and center of thrust indicators? By which I mean why would the center of thrust be pointed slightly downwards? Also, anybody got any ideas on "where I should go from here"? I mean, I what do y'all typically do with your spaceplanes? I'm also finally beginning to understand why folks think the terms "spaceplane" and SSTO are synonymous - given what I've learned so far, it'd be difficult (though not impossible, I'd wager) to build a spaceplane that couldn't achieve orbit.

I generally shoot for about 125% of the indicated delta-V, and then thanks to the method I use to determine the number of "FL-T100 Equivalents" required I often wind up with a little bit more than that. Sometimes its enough. Sometimes it isn't. I have found that the latest iteration of the delta-V map is a bit more accurate than previous versions; the nice thing about it is that it also includes the amount of delta-V required for orbital plane changes. Every bit of info helps. I'd link it but I don't remember where I first saw it.

Continued my misadventures with spaceplanes this evening. Referenced The Drawing Board for the first time - I figured some of the folks there would know what they were talking about. Attempted to apply their principles; still didn't design a plane that would take off before it reached the end of the runway, though I did get one up to 25,000 and almost orbital velocity. Might've made it had I assigned my twin rocket engines to fire simultaneously. Flat spin and out. Luckily I'd added an ejection system so Thomemy lived to crash again. Learned that raising the gear before take off is a bad idea. Barely had time to eject on that one... EDIT: Have had success since my last post. Even managed to land it on the runway intact afterwards, at night and without proper ground markers (wasn't in my main save game).

With Tier 0 tech, you can build an SSTO rocket - just a chute, a command pod, 9-12 FL-T200 tanks (fewer is better but go with more if you're not comfortable with your piloting skill) and a single LV-T30. Launch into polar orbit and do EVA reports over as many biomes as you wish. Come back down when you're ready. Expect to lose the engine and about half your fuel tanks when you finally land - your command pod should survive. That'll get you a goodly amount of science right off the bat. So....that was not your question. #facepalm Tier 2 techs I recommend in this order: Survivability, General Rocketry, Stability (radial chutes allow you to make bigger constructions - read moar goo pods in polar orbit; the Mk1 Command Pod has sufficient torque thrust for steering most of the rockets you'll be building at this level unless you go ape, and about the only thing moderately useful Stability offers is the TT38-K, which is quickly outmoded by the TT-70 with General Construction). I do recommend you get them all before moving on to Tier 3. Likewise I recommend you get all Tier 3 techs before moving on to Tier 4. I recommend Science Tech (batts!), General Construction (struts!), Flight Control (Stayputnik!) and Advanced Rocketry (not much!), in that order. Tier 4 is where your options open up. Go first for Electrics (solar panels), then Fuel Systems (fuel ducts = asparagus staging). From there it's really a matter of what you want to do next. In general, though, I'd recommend Heavy Rocketry and Advanced Construction next on Tier 4, then jump to Specialized Control and Heavier Rocketry on Tier 5 before hitting Nuclear Propulsion on Tier 6. That gets you nuclear engines, which is generally what you need to go interplanetary. You don't necessarily have to do that to max out the tech tree, of course, but like I said it really matters what you want to do most. EDIT: I suppose once you've got Electrics, you could go Electrics -> Advanced Electrics/Advanced Exploration -> Electronics -> Advanced Sci Tech. That way you unlock the rest of the Science instruments.

To be fair, I use a spreadsheet myself. And I have it set up so that one one workbook it tells me how much delta-V I have given x amount of fuel, and on another I have it set up to tell me how much fuel I need to get x-amount of delta-V. Forwards and backwards. To get the "backwards" to work, I make the assumption that a full fuel tank weighs nine times as much as it does when it's empty; true for every liquid fuel tank in KSP except the Oscar-B and Round-8. I also have it shoot out results in factors of "FL-T100 equivalents", since that's the smallest tank for which the assumption holds true and the other tanks are basically multiples of it. Gravity: g=GM/R^2. Your rocket's mass wouldn't factor into that particular calculation, but its altitude would. ...you also asked me about dry mass, and yes, that's the mass of a stage when it's out of fuel. Seret is also right about TWR; it is worth keeping an eye on during your launch. Ideally, you want to keep it somewhere between 1.8 and 2.2 or so; that minimizes fuel losses to gravity and drag. In the vanilla game, the gee meter gives you a rough indication of how that's going: during the vertical part of the launch, you generally want to keep the gees about halfway between the first and second mark (i.e. between 1-2G); my own observation has been that this should be closer to the one gee mark. Once you make your gravity turn, you want it to stay roughly at the top of the green zone. If it climbs out of the green, throttle back a bit to minimize fuel losses to drag.

Just did the scoring based on my original Constellation mission for the lulz. 4.036032 if I did the math right: Launch: 0.8 (working escape system plus a ship constructed in orbit - the lander rendezvoused with the command pod) Flight Plan: 1 (free return to Mün) Kerbals: 6 Kerbals in Command Pod: 0.7 (base, plus no Kerbal left behind) Kerbals landed: 1.3 (0.3 base plus everybody down) Rovers: 1.2 (two working manner rovers) Science: 1.1 (.5 base plus .6 for two biomes visited - on two separate landings) Landings: 1 (base plus two stage landers) Return: 1 (water landing) Debris: 0.7 (the upper stage of the crew launcher stayed in orbit; never did fix that one) Survival: 1 (everybody came home) Still think I'll do a seperate entry solely for the challenge - I just wanted to see if I was scoring everything right.

Decided to go ahead and start braving the frontier of spaceplane design. Am learning that generating lift is trickier than it looks...my designs so far can take off but not before they reach the end of the runway and once they're off they don't climb worth a good fart. Will probably go back to rockets soon.

I have set up a formula to compare engine efficiencies before (in that case, it was a question of at what point the 48-7S became more efficient than the LV-909) and I've gone ahead and applied the necessary data for comparison (mass of the engines and their respective vacuum Isps) to the same formula to try and figure out where the "tipping point" is (i.e. the deadmass - anything other than fuel tank or engine - at which point, regardless of the amount of fuel involved, the heavier engine is more efficient). The idea is to see how much delta-V the heavier engine generates given the same payload and same amount of fuel and then to see how much fuel is required by the lighter engine to produce the same amount of delta-V. If the lighter engine requires less fuel, it's more efficient; if it requires more, the heavier engine is more efficient. The tipping point in the case of LV-909-vs-LV-N is 0.87065 tonnes, so if you're pushing anything heavier than that, you're generally better off with the nuke.

Getting to Eve orbit from Kerbin orbit = easy. Getting back to Kerbin from Eve orbit = easy. It's just like going to Duna - in fact I maintain it's easier than going to Duna, as you need less delta-V to get to Eve and there are in general more launch windows per Kerbin year. Landing on Eve = easy. Just pack chutes. Drogues are useful on Eve, I've learned... Taking off from Eve = insanely difficult. But that's the only bit and if I were to guess, that's the real question you want to have answered. Having yet to do it my own self, I can't really help you there.

Alrighty...well, first and foremost, the most important equation in rocketry is the Tsiolkovsky Rocket Equation: delta-V = ln(M/Mo)*Isp*go Where ln is the natural logarithm, M is the current stage's total mass, Mo is the stage dry mass, Isp is the stage specific impulse of the engines and go is standard gravity (9.81 m/s2) Learn that formula forwards and backwards. No, literally. A key thing about Tsiolkovsky - it's actually Newton's Second Law. It's just been adjusted to account for the fact that the mass of your rocket is not a constant (it couldn't fly if it were). Delta-V is literally change in velocity; integrate it with respect to time and you have acceleration. Thrust to weight ratio is: TWR = Ft / (M * G), where Ft is the current thrust of your rocket, M is the total current mass of your rocket, and G is the surface gravity of the body you're either launching from or landing on. It's less important than Tsiolkovsky, but still important during takeoff and landing. Now, your question is about drag. The formula you found is how KSP currently models drag, and it's one of those formulas whose solution is extremely time dependent. It's dependent upon the craft's velocity, atmospheric density and mass, all three of which are changing with respect to time. Note that if you could calculate the drag force at an instantaneous time you could then estimate your rate of acceleration at that time - it would be a relatively simple force balance equation (between gravity, drag and thrust). I think a practical example is probably in order here; I'll need some time to work one up. Gravity meanwhile is rendered the usual way - g = GM/R2, where g is gravity, G is the universal gravitational constant (6.67*10-11 I forget the units), M is the mass of the body, and R is the distance to the center of mass of the body. (GM) by itself is also known as the gravitational parameter. For Kerbin, this value is 3.5316*1012 m3/s2. The planet's equatorial radius is 600,000 m, so you plug that in: g = GM/R^2 = 3.5316*1012 / (600,000)2 = 9.81 m/s At a 100 kilometer orbit, the gravity is: g = GM/R^2 = 3.5316*1012 / (700,000)2 = 7.207 m/s Incidentally, note that gravitational force is also changing with respect to time. Yet another wrench to throw into the works. ...you are always under the gravitational influence of something in KSP, which is why I always tell people there is no such thing as infinite TWR.

Hmm...I'd use my Constellation hardware as is, but I'd lose points for the launch. Might have to try anyway. Or pull a redesign - maybe use something a little more reliable/sturdy than the Thanatos Heavy booster...

I use KER a good deal. My procedure for getting to orbit is much like Aphobius's, though I tend to follow the prograde vector as long as my time to Apoapsis is between 35-55 seconds. I burn along the horizon once the Ap is above a minute and keep burning until the Ap is where I want it in order to account for what I'll lose to atmospheric drag based on alititude (+10k for 50,000, +30k for 40,000). Might have to try out his method my own self to see if it saves fuel. Usually an orbital insertion burn after a good gravity-turn ascent takes 4-5 seconds, and maybe 50-100 m/s of delta-V, at best. Getting to another planet on that data is another matter. KER is generally helpful for making orbital plane changes; I'll admit that I don't understand the rest of the rendezvous data it provides. I rely on other mods (KAC, Protractor) to make interplanetary burns as a rule.

Yeah...a Mün burn shouldn't take more than a couple of minutes even if you have lousy TWR. Flag in my mind says you need to check to see if you've got a coupler upside down and stuck to the engine; it'll look and sound like it's working but you won't actually be doing anything.

It's likely the Mainsail is outputting more thrust than what you need for your remaining payload. The advice you've got so far - throttling back - is sound. What you need to do once you've separated the last set of boosters (assuming you don't pancake) is look at your gee meter. If you're above the green zone, you need to throttle back even more (and consider swapping out with a Skipper if you want to launch the design again). If not, throttle back up - put your gee meter right at the top of the zone. That'll put you right round that 2.0-2.2 TWR you're looking for when you launch.

Finally was able to come home and play KSP. Decided to try building an SSTO Tier 0 Rocket I suggested a few days ago to make sure I hadn't steered anybody wrong. Flew it up, orbited Kerbin, came back down. Successfully recovered the command pod and five of the nine fuel tanks. Might've been worth a bit had it been a career flight and if I'd shot it poleward... Decided to try my hand at the Kerbal X challenge. I could've sworn I'd flown one of those to Mün and back before...I got it to the Mün but I'm reasonably sure it ain't coming back any time soon.

Wanted to confirm I wasn't steering anybody wrong with the advice in my previous post, so I built said craft described above and launched it this evening. Actually, I've got a mod that allows KER functionality without KER parts, and it told me that the twelve tanks would give me 5300 m/s (more than enough for an orbit and return). So I started taking tanks off; nine tanks were sufficient to get the craft into orbit with sufficient delta-V for de-orbiting (was left with 60 m/s of delta-V when everything was said and done). The landing was hairy on account of the thing started tipping over rather than land straight up and down, but the important thing is that the command pod/pilot survived. So there you go. Launch a craft like the one I described into a polar orbit (steer north or south instead of east when you make your gravity turn). You should be able to make EVA crew reports over multiple biomes, and then once you're down you can collect a surface sample from wherever you wind up. Should be a worth a goodly amount of science and you can actually go into space rather than muck about the launchpad.

Hmmm...maybe it was another rocket I was thinking about...anyway, I'll probably have an entry for y'all in the near future.

All command pods have SAS capability; they've been that way since 0.22 unless I'm mistaken. Just hit the "T" key before you launch and you should still be able to fly straight. You'll need to push the "F" key for momentary SAS toggling if you make any directional changes.

The ascending node is the point at which a craft's orbit crosses a reference plane moving in a direction normal to the reference plane; the descending node crosses moving in an anti-normal direction. They are the most efficient points at which to align the planes; you do it by burning anti-normal (upside down triangle with spokes) at the ascending node or normal (triangle with a dot in the center) at the descending node. More simply, assuming you're in a 090 prograde orbit (i.e. flying east), burn north at the descending node or south at the ascending node. So for rendezvous, here's what you do: 1) Target your target. This way you'll get the approach chevrons. 2) Adjust your plane until your nodes get to 0.0 degrees - if you get it to NaN degrees, you're spot on. You should have the chevrons for sure at this point. 3) Note the distance of closest approach. 4) At the next apses, set up a maneuver node. Pull prograde and see what it does to your distance of closest approach. If the distance increases, stop and pull retrograde instead. Keep pulling until the distance starts increasing again. If you had to pull retrograde, watch the resultant distance of the periapsis - in Kerbin orbit, you want this to stay above 70,000 m (of course). 5) Repeat this process at the next apsis. Keep this up until you can't make any meaningful adjustments at the apses. 6) If you still don't have an approach within 2,250 m, try making adjustments between the apses, or make a few orbits and see if you can get the distance down. Be ready to adjust at the apses once more. Try those steps and see if that helps you make the rendezvous. If you're trying to dock: 1) Once you make rendezvous, burn to reduce your relative velocity to the target ("Target" on the speedometer) to zero. Try to do this as close to the target as possible. 2) Once zeroed, turn to face the pink meatball on your nav ball. Do this on pod torque only; don't use RCS if you can at all help it for this stage. 3) Thrust ahead and watch your distance. Keep your speed to about 0.1 m/s per 10 meters distance (but don't worry too much about this). 4) At 500 meters, zero your relative velocity, realign on the meatball, and thrust ahead. 5) Do this again at 100 meters and 50 meters. At 50 meters if you have not done so already, target the specific docking port you're aiming for. Start using RCS at this point for velocity changes only. 6) At 20 meters, zero out and realign again. Switch to the target craft, set your control point to its docking port, target your source craft's docking port, and align on the pink meatball. Again, do this on torque thrust if at all possible. One you're on the the money and not moving, set the target's SAS on and switch back to the source craft. 7) Retarget the other craft's docking port and set your control point to your docking port. Once you're aligned, go to 10 meters, zero and realign once again. Do it again at five meters if necessary. Keep it slow and steady. 8) Once you're within a meter or two, your docking ports will start attracting one another (provided they're the same size, of course). They'll pull one another in. If there is any remaining misalignment, the two craft will dance a bit with one another but they will ultimately settle down. When the camera shifts, you're docked.

Naw, just waiting for the next launch window...