Calculating most efficient ascent profile by hand.

[OxalysResourceConsortium]

Disclaimer: I apologize if I posted this in the wrong section mods, if you could, please move it to the correct one.

I'm looking to use kOS to write scripts to automate my craft. I'm an engineer not a pilot Jim! I love designing rockets and whatnot but hate actually piloting them, and feel like using MechJeb is kinda boring, especially given that this could be a chance for me to learn useful skills to help me further my education while having fun doing it.

I flunked out of Calculus III so I'll need to brush up on my maths but I feel like if there is anything I need to learn maths-wise I can just watch KhanAcademy videos or something similar and teach myself. I still have some old Calculus textbooks with practice problems I can work with.

What I want to learn to do first is how to calculate the ideal ascent profile by hand. I'm sort of debating with myself whether I should install F.A.R. or not but I'm thinking not as it would just eat up more of my RAM than I'm comfortable with. Right now I'm not going for a 100% realistic career. Once I feel more comfortable that I know what I'm doing and that I'm up to the challenge I might go for the realism overhaul, but not yet.

I know that using kOS I can probably guesstimate the best ascent profile by trying out different ascent profiles for every new rocket design, but I just don't have that kind of time. Plus, I figure I probably have the smarts to learn the physics and math needed. This is probably a good way to motivate myself to finish the education I initially completely wasted being a lazy college student so any help would be appreciated .

[FenrirWolf]

I don't imagine FAR uses much memory at all. It's not like it adds a ton of models and textures like some other mods.

[OxalysResourceConsortium]

Thing is with stock aerodynamics there all sorts of neat tools and charts and guides and delta-V maps available for my disposal. Given the challenge I'm setting myself up for I have enough to deal with as it is without adding in more workload, though I may change my mind later on if I feel that I'm not being challenged enough.

[nhnifong]

I think you absolutely should install FAR! It makes KSP a lot more realistic, and tends to make ascent paths simpler. In addition, it has a lot of awesome readouts that you will probably find useful.

The optimal ascent is the one which reaches the target orbit with the least propellant, so another big factor in what your answer comes to is whether or not you install a mod that fixes KSP's totally unrealistic fuel flow rate based on ISP. in a real rocket, I believe, fuel flow rate is constant but thrust changes. The reason anything is changing at all is that the air pressure is dropping and so the rocket is getting more efficient as it goes up. I don't know what the current mod for that is though.

[Rokker]

Well, the thing is that, quite honestly, there isn't necessarily a single correct answer here. As far as I can tell it all depends on things like the changing TWR and staging and things like that.

[Rokker]

I think you absolutely should install FAR! It makes KSP a lot more realistic, and tends to make ascent paths simpler. In addition, it has a lot of awesome readouts that you will probably find useful.

The optimal ascent is the one which reaches the target orbit with the least propellant, so another big factor in what your answer comes to is whether or not you install a mod that fixes KSP's totally unrealistic fuel flow rate based on ISP. in a real rocket, I believe, fuel flow rate is constant but thrust changes. The reason anything is changing at all is that the air pressure is dropping and so the rocket is getting more efficient as it goes up. I don't know what the current mod for that is though.

Use ferrams ISP difficulty scaler mod it allows you to choose either stock or ferram based ISPs and a number of other things.

Edited April 20, 2014 by Rokker

[Jimbimbibble]

The trouble is that there are just too many variables to get an explicit solution. However, if you make a few assumptions, you might be able to do the calculation. You can assume that the throttle stays at 100% and that you fly a perfect gravity turn (research gravity turns). You would also have to make some assumptions about the aerodynamics (many more assumptions with FAR.) Then, you would varry the initial angle that you launch at and iterate until you find the best one. You will probably need to know about differential equations to write this program. Good luck.

[Rokker]

Well with FAR, you can get a decent number of rockets that follow a relatively efficient path by themselves with SAS off due to the angle between the blah and the somethingorother vectors, cant quite remember at the moment.

Edited April 20, 2014 by Rokker

[FenrirWolf]

Either way, the decision to use FAR or not merely changes the problem domain for the question you're asking. There exists an optimal launch profile for a given rocket in stock, and the same rocket would have a different one in FAR

[mhoram]

Calculating it by hand is not easy.

If you don't use FAR, then you can find good information in these threads:

• I need someone help me do some math for launch optimization
  
• Finding the best ascent path for rockets
  
• Launch Efficiency Exercise V0.21.1
  
• Ascent Komputron (Standalone Software, not open-source, did not try it myself)
  

Edited April 20, 2014 by mhoram

[MarvinKitFox]

You want to formulate a general procedure, for manually calculating optimal ascent profile for a generic spacecraft?

.

Wot, are you tasked with inventing a new Labour for Hercules?

There are SO many factors, not least of which sillyness such as

"this rocket design *must* fly vertically until stage 1 drops, else the dropped stages will contact and RUD my ship"

Actually, about 7/8 of my designs that mass over 2000 tons fall under this rule..

[Cakeofruit]

i just started to us kos too and the idea i got to get the best ascent is a kos script that make a log file to every launch to track data !

With those data it will change some correction values and see if the ascent is better.

I want to write a launch program to LKO for a shuttle under ferram to get my playload without any intervention just plug the altitude.

[rkman]

Calculating an efficient ascent profile by hand is apparently extremely complex:

I need someone help me do some math for launch optimization

http://forum.kerbalspaceprogram.com/threads/46194-I-need-someone-help-me-do-some-math-for-launch-optimization?highlight=ascent