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Found 7 results

1. ## How to calculate dV for other planets?

Hello guys. I am an amateur Kerbonaut and I want to start to calculate dV by hand since it is so nice and fancy to do. When I looked up, I came across this formula: dV = Isp * gravity * ln(m0 - mf) Everything is fine, but when I utilize this equation and check the results with VAB, I get HUGE differences for other planets. Currently I am trying to visit Eve and comeback. My lander should have God knows how much dV. So, for a stage (mid), I put: Rockomax 32 (x1) FL-A215(x1) FL-A151S(x1) Skipper The upper payload is 4.090t. Therefore, according to the equation: Isp = 280 Gravity = 16.7 m0 = 32.740t mf = 9.940t and dV should be 280 * 16.7 * ln(32.74/9.94)= 5579.9 m/s but VAB says it is 666m/s. What I am doing wrong? Good luck in your space journeys

Edit: this is a dumb suggestion and i didn't phrase it the way I want. old title: Engine-ers should be able to tweak engine trust/ISP/etc. (see desc) Engineers (mid-high xp level) should be able to tweak engine ISP for more thrust and vice versa. E/C alternators in engines could be disabled for more thrust, or cranked up to produce more electricity at the expense of more fuel or less thrust (like a crappy low-tech fuel cell). Of course, the "tweakability" of everything should be limited so we can't have mainsail engines replacing nukes and vice versa. Maybe this could be balanced with an overheat mechanic: increasing thrust/ISP causes overheating and require radiators. At one point the rocket will reach a hard limit.
3. ## 0 Isp No thrust Engine?

Simply, I am working on my physics thesis and I need to observe the effects of gradual change in mass of a rocket in orbit without any force being applied, namely thrust. For this I need fuel consumption, the rate of which I can modify but no thrust. The only thing that comes to my mind is using a 0 Isp engine but I don't know how to change the files. Do you have any suggestions other than a modified engine? If not, how do I change the Isp and thrust values of engines in the game? Is there a mod I can use?
4. ## Isp in m/s?

Hey guys, after screaming at my screen for 5 minutes because my calculations didn't make any sens whatsoever I realized that the Isp in ksp is in [m] not in [m/s]. So I wanted to ask if there is a mod which automatically calculates the Isp in [m/s]. Because viva la metric system!!! xD Thank you for your help in advance.
5. ## Check my combined Isp formula?

So I'm putting together a spreadsheet - in part because KER is not up to date yet, in part for learning experience. Something I've meant to do for a while. Need someone who knows what they're doing to check my math logic here. What I've got going on: I've got a table of engine data and rather than make a user type in their vessel's Isp, I have them place a quantity next to each engine type. These quantities are 0 if none. Might put down they have 1 skipper and 2 thumpers, though. So from what I can tell, the way to measure combined Isp with combinations of engine types is a thrust-weighted average. I guess because thrust and isp are both in relationship to exhaust velocity? Check me here. The formula I've found is: thrust / (thrust 1* isp1 + thrust2*isp2 ...). Since I'm factoring in the quantity of these engines as well, I fist multiply thrust1 by quantity1, so if quantity is 0 the thrust and isp of that engine is removed from the picture. And if they have 2 or 3 of an engine, thrust is doubled, tripled, etc, affecting the weighting of the isp. So where T= total vessel thrust, Tx, Qx, and Ix are thrust, quantity used, and isp of engine number x, this is my formula... T/(T1*Q1/I1 + T2*Q2/I2 ...) (formula runs through every engine in the list this way so it changes as soon as engine count changes) If I tell it I have 1 terrier or 100 terriers, it correctly tells me my Isp is 345, can someone give me test cases and answers to run through my formula?
6. ## 2 Rocket equation questions

Hello! I have some math questions. So if you don't like math, well, I do. Kinda. I consider myself an intermediate experience player, currently getting on just fine with the numbers kerbal engineer gives me. I hate actually doing math so I'm not likely to give that up any time soon, but I am comfortable with mathematical concepts. In fact, I have some interest in getting a grasp on themathematical science behind simple rockets....But I never learned logarithms. And the rocket equation involves a natural logarithm. Question 1: what are logarithm and natural logarithm, and how to do them? For the second question: the rocket equation traditionally appears using exhaust velocity. I have read it can also use isp. But I haven't seen the version of the rocket equation that uses isp, that I could plug in the stats we get in KSP. Also, I know isp is counted in seconds and relates to the engine efficiency. As I understand Newtonian physics, exhaust velocity IS your efficiency, so.... how is isp calculated and why is it more popular than exhaust velocity (other than because that's what SQUAD gave us).
7. ## Rocket Engine Efficiecny

Hi in new to forums I have been playing Kerbal for some time just noticed that all rockets have Specific Impulse (Isp) always lower for Above Sea Level (ASL) than (Vac.). From what I know rockets are quite efficient and the only difference is mostly in the nozzle design. https://en.wikipedia.org/wiki/Rocket_engine_nozzle See ideal expansion. Hence it must be possible to have rockets that are designed to be more efficient in atmosphere. Seems like this has not been implemented. It would be nice to see some lower stage rockets/engines.