Comprehensive Physics Guide for KSP (WIP)

[alterbaron]

I'm working on a guide to the physics behind KSP!

This is for those people who want to get really hardcore with their mission planning, want to develop calculators / programs / mods, or who just want to learn some physics.

Here's a link to the guide so far:

Comprehensive Physics Guide (WIP)

This guide (still incomplete) will hopefully be able to take someone with at least basic proficiency in physics and math to a level where the physics of orbital mechanics don't represent a barrier to doing calculations or developing tools for KSP.

The guide will be focused on using physics equations as building blocks towards solving practical problems. I feel that this sort of approach can help eliminate much of the confusion that inevitably seems to pop up when dealing with physics.

There's still quite a bit to add. I'm planning on adding a section on the vis-viva equation (which was pretty much used and motivated in the section on energy anyway) as well as a few sections on elliptical orbits, eccentricity, .etc

By the end of the guide (once it's finished), I hope to derive and explain the formulas for planetary transfer angles, Hohmann transfers, .etc

Also, more diagrams are needed at the moment.

Please let me know what you think!

[Zanis]

This is a very Interesting idea. Even though i have never used any sort of math in my Space craft creation it would be intriguing to know the physics in the game.

Hope you can Complete this Good Luck!

[The Lone Wolfling]

Perhaps add a delta-v map of the system and talk about the reasoning behind rockets having multiple stages (fuel tanks have a mass ratio of 9:1 wet/dry - lim(m->inf) ln[(M+m)/(M+m/9)] is only ln(9), or something like 2.2, which means that no matter how much fuel you keep adding to a single stage, you're only going to be able to achieve a delta-v of something like 2.2x the specific impulse of the engine.)

Although you may wish to describe it a little more coherently than I just did.

[flightmaster]

Doesn't work for me The URL loads but nothing appears

EDIT: Really? 2 posts? Damn...

[supermap]

this looks like an awesome idea... and it could actually be used for educational purposes

i was thinking about doing something like this but more of a pilot´s handbook illustrating various maneuvers, showing how to calculate dv needed to perform such maneuvers and some mathematical explanation for why use those maneuvers.

i think it could be a cool thing to have a little guidebook for space maneuvers... just in case you ever need those skills

[Malaugrym]

I printed this out after I saw it on reddit a few days ago. One thing I would love to see would be a "walkthrough" of the math for a specific mission. Something like "So you want to go to the Mun? Ok, we need this much delta-v in this many stages with this much mass. This gives us the position at which we drop the first stage, which is this far from over there." And so on and so forth.

[Neici]

Wow quite impressive collection you have here!!

This is really helpful if you don't have to search all those equations in the Wiki.

And another + for really clear and understandable text! Not like Wiki. ^^

The only problem is that is saw this too late for my uses ^^

This is the reason i compare with Wiki

[Neici]

I printed this out after I saw it on reddit a few days ago. One thing I would love to see would be a "walkthrough" of the math for a specific mission. Something like "So you want to go to the Mun? Ok, we need this much delta-v in this many stages with this much mass. This gives us the position at which we drop the first stage, which is this far from over there." And so on and so forth.

Nice idea.

This would be really cool.

It would also be cool to see a formula to calculate the delta V consumptions. Like getting into orbit with a planet of this atmosphere and gravity an so on.

[chainedlupine]

I'm digging this. I think a very basic explanation of Kepler equations are in order, plus a tiny bit about the rocket equations. That would dovetail nicely into the talks about requiring dV for different actions, and the understanding about calculating position/velocity/rate of change, etc. later on.

[TriggerAu]

I Agree, this is great, thanks Alterbaron

[Neici]

If you do this document especially for KSP and mod developers eventually consider adding KSP specific equations with values found in a part file.

For Example see this thread: http://forum.kerbalspaceprogram.com/showthread.php/24733-Calculating-with-the-ratio-value-of-an-engine

[czokletmuss]

Very good idea, I would love to learn something in this way

[alterbaron]

If you do this document especially for KSP and mod developers eventually consider adding KSP specific equations with values found in a part file.

Thanks, that's a really good point!

I'll have to add a section on dealing with in-game units.

[alterbaron]

One thing I would love to see would be a "walkthrough" of the math for a specific mission. Something like "So you want to go to the Mun? Ok, we need this much delta-v in this many stages with this much mass.

That's a great idea, I'll definitely need to add something like that!

[ROFLCopter64bit]

If you want, I can help with the creation of this by making articles, if you want.

[SZDarkhack]

Very nice and useful project for people who don't have the physics background. Some suggestions to add:

- You should add a note at the escape velocity calculation that it's equal to sqrt(2) * the circular orbit velocity at that altitude.

- You could include the derivation of the gravitational potential energy in there as a side note.

- A section on the Oberth effect would be very nice to see (and easy to explain with the energies taken care of already).

- Some visuals would be nice, like some diagrams of the various types of orbits (based on eccentricity).

I'm suggesting these just in case you haven't considered them already (i know it's work-in-progress, of course). Very nice initiative and i'm looking forward to seeing more. I'll definitely be keeping an eye on this

EDIT: And if i can help in any way, i would be glad to.

[Banbite]

Very nifty, useful for newcomers and people who wanna do a more scientific approach.

But shouldn't the unit of specific orbital energy in your examples be J/kg instead of J? Just something I noticed.

[alterbaron]

But shouldn't the unit of specific orbital energy in your examples be J/kg instead of J? Just something I noticed.

Good catch! Added to to-do list.

[NeoMorph]

You do realise that you will have to re-do it when Squad get around to doing a proper physics model. Ferram's Aerospace model is more realistic which I hope will get introduced into the main build.

[Neici]

You do realise that you will have to re-do it when Squad get around to doing a proper physics model. Ferram's Aerospace model is more realistic which I hope will get introduced into the main build.

As i saw in overflying the document nothing has to do with aerodynamics. And this is the only thing that will change in you mentioned update.

Most of the equations actually shown are realworld physics. If not all of them.

[dozer]

Excellent Alterbaron!

I'm in the aviation business, and we always prepare a "data card" before our missions. I'm planning to make something in Excel where you can input the "all" parameters(stages, twr, dV etc.) and your plan(go to Mun with such and such burns etc), and after some autocalcs you can print it out and track your mission status as you go vs planned numbers. Your work really helps!

Also this page is excellent with example calculations! http://www.braeunig.us/space/

Edited April 22, 2013 by dozer
Forgot to add link

[oomrp]

great post thanks. curious about using this as a teaching tool.

[Muffinking]

Perfect timing, I have the huge luck that I am allowed to use ksp for school. I plan on making a mun base and then calculate how to land a lander next to the base, something which is not easily possible in the game due to the rotation of the mun. But i'm kind of stumped how to start, I am allowed to start in an orbit of 100 km, if anyone knows where to start (how to calculate delta-v for reaching mun orbit etc) i would greatly appreciate the help.