Orbital Mechanics software or refresher tutorial

[SpaceBadger]

I stumbled on this, I don't know if this is what you're looking for or not.

http://www.projectrho.com/rocket/supplement/orbitalmech.html

DU is, basically, au (astronomical unit). TU is a "time unit". It's explained in this paragraph:

But it does talk about higher power orbit transfers, and it's step by step.

I don't think it takes in to account things like the gravity effect of other bodies (notably Jupiter -- it's a big hole in our sky). But it might be a start closer to what you were looking for vs my "turn and burn" Flash Gordon technique.

Cool, that is Winchell Chung's website (if you bought any Microgames during the late 70s, or any issues of the SpaceGamer magazine, you probably have some examples of his artwork). I've browsed around it before, but never hit that page you cited. Thanks!

 

[SpaceBadger]

Thanks, whartung; that page does seem to have all of the necessary formulae; now I just need to work on my rusty old brain a bit to understand them! At least, as far as I can tell, there is no calculus involved, only some trigonometry.

Since these look to be some pretty hairy calculations to do off-the-cuff in the middle of a game, I hope that I can gain sufficient understanding to make a nice program to do the calculations, given necessary input as to the trip desired. If I can create something useful, of course I will post it in the file-sharing section here.

 

[aramis]

Cool, that is Winchell Chung's website (if you bought any Microgames during the late 70s, or any issues of the SpaceGamer magazine, you probably have some examples of his artwork). I've browsed around it before, but never hit that page you cited. Thanks!

Winchell occasionally can be found posting around COTI as Nyrath.

 

[whartung]

Since these look to be some pretty hairy calculations to do off-the-cuff in the middle of a game, I hope that I can gain sufficient understanding to make a nice program to do the calculations, given necessary input as to the trip desired. If I can create something useful, of course I will post it in the file-sharing section here.

Yea, I wouldn't do them on the back of a napkin, but you can most likely do them readily on a spreadsheet to where you need only key in the orbits and masses of the planets, and the "width" of the intercept for the second, higher energy style. I'd also suggest a programmable calculator (not that these really exist much any more), or a simple script in a programming language of your choice (Python, Perl, BASIC...).

What this doesn't tell you (or at least me) is it doesn't tell you the vector of the delta V (either for the initial impulse or for the arrival burn (though I ideally the arrival burn is simply breaking -- i.e. applied directly backward on the object itself.

It seems to imply, to me, that the original vector would be in tangent to the solar orbit. The premise being that the radius of your orbit determines your orbital speed. If you accelerate in tangent to the solar orbit, you are increasing your orbital speed, and therefore your orbit will basically adjust to where it needs to be (this is a simplistic explanation). The arrival burn corrects and stabilizes the orbit. I'd have to play with the simulation to figure that out.

However, the other thing that this does not tell me, is WHEN to apply the arrival burn. At what point in the flight. I suppose the burn should apply simply when it reaches the correct orbit, or perhaps it's simply timed to correct the overall velocity so that it is the proper orbital velocity by the time it arrives. To do this properly may well involve calculus.

Finally, the equations do no compensate for the other bodies in the system. This may well not be really germane, and rather an over complication.

It also doesn't really consider the coordination of orbits. The premise being that these techniques allow us to change orbits. However, it doesn't say anything about the destination actually being at the proper place along the orbit. So, I don't think it's a particularly good technique (with the information that we have) to get from planet A to planet B, but rather the orbit of planet A to the orbit of planet B.

 

[SpaceBadger]

It also doesn't really consider the coordination of orbits. The premise being that these techniques allow us to change orbits. However, it doesn't say anything about the destination actually being at the proper place along the orbit. So, I don't think it's a particularly good technique (with the information that we have) to get from planet A to planet B, but rather the orbit of planet A to the orbit of planet B.

Hmm, if so it would have one thing in common w Hohmann transfers: a narrow launch window. You would have to figure out the time taken for the transfer, and when your starting planet is in the right place relative to the destination planet to get you to the destination orbit when the planet is in the correct position. Added complication, and like you said, probably requiring some calculus to get right.

 

[whartung]

Hmm, if so it would have one thing in common w Hohmann transfers: a narrow launch window. You would have to figure out the time taken for the transfer, and when your starting planet is in the right place relative to the destination planet to get you to the destination orbit when the planet is in the correct position. Added complication, and like you said, probably requiring some calculus to get right.

It's pretty clear with these mechanics that they only work if you want to move radially in orientation to the center you're orbiting (the star in this case). Either inwardly or outwardly. That's why the narrow launch windows. Also the nature of the system is that if you get to the desired orbit, but the target is not there, you can't really "speed up" to catch the object or "slow down" to wait for it. When you do that, your orbit changes. Clearly you can do this, but it's not like waiting at the corner for your friend to catch up.

This also helps show, I think, why "turn and burn" is so empowering for space flight. It solves a lot of these window problems. You simply go faster than the gravity wells allow and cut across all of those problems. But we here on Dirt, we don't have that power yet, so we're still at the mercy of the Sun and planets when plotting our travels. Much like in the past where the tall ships were mostly traveling at the whim of the winds vs today where we just power through all that.

We're in the Age Of Sail still when it comes to space flight.