KSP Orbital Calculator [V0.10.1] - Now with selectable Celestrial Bodies

[kaploop]

I had your first version, and want to use the newest. But I have no clue why it won't run. I download the file, open it, and it shows me a kspcalculator.jar, which I double click and it opens up and shows a ton of different files.

I am frustratedly confused

[Warringer]

Use the .bat file that is included in the zip file.

[XiXLLAMAXiX]

Hey, I've been using your calculator recently, and I think there might be an error in the part that calculates bi-elliptical transfer orbits. I was fiddling around with some numbers trying to find a set of altitudes that resulted in a bi transfer with a lower delta v than an equal hohmann transfer when I realized something. with a lower orbit of 100km and an upper orbit of 1000km, the delta v needed for the transfer orbit injection in a hohmann transfer orbit is about 403 m/s. However, in a bi-elliptic transfer orbit with a lower orbit of 100km, a turnover altitude of 1000km, and a higher orbit of 900km the Transfer Orbit injection required a delta v of about 966 m/s. From what I understand, because both of these injection orbits start at the same altitude and end at the same altitude, the delta v should be the same... I could be misinterpreting something, but I think that it is likely that something is wrong given that there is no altitude change that I could find that makes the bi transfer cheaper.

[Warringer]

Hey, I've been using your calculator recently, and I think there might be an error in the part that calculates bi-elliptical transfer orbits. I was fiddling around with some numbers trying to find a set of altitudes that resulted in a bi transfer with a lower delta v than an equal hohmann transfer when I realized something. with a lower orbit of 100km and an upper orbit of 1000km, the delta v needed for the transfer orbit injection in a hohmann transfer orbit is about 403 m/s. However, in a bi-elliptic transfer orbit with a lower orbit of 100km, a turnover altitude of 1000km, and a higher orbit of 900km the Transfer Orbit injection required a delta v of about 966 m/s. From what I understand, because both of these injection orbits start at the same altitude and end at the same altitude, the delta v should be the same... I could be misinterpreting something, but I think that it is likely that something is wrong given that there is no altitude change that I could find that makes the bi transfer cheaper.

That's the fun about bi-elliptic transfers. In some cases they DO need less Delta-v then a Hohmann Orbit. Which is why they are used.

[starplayer]

Hey mate, I think the Specific impulse of the engines depicted in the stage and multi stage calculators should be in m/s, instead of s. Thanks a lot for your work btw, it helps a lot=)

Edit: Forget it, it's okay in the latest version=P thanks again

[XiXLLAMAXiX]

That's the fun about bi-elliptic transfers. In some cases they DO need less Delta-v then a Hohmann Orbit. Which is why they are used.

oh no, I know what bi-elliptic transfers do. it's just that I couldn't find a set of numbers to put into the calculator that gave that result, and I put forward a theory as to why that was the case...

[Warringer]

Hey mate, I think the Specific impulse of the engines depicted in the stage and multi stage calculators should be in m/s, instead of s. Thanks a lot for your work btw, it helps a lot=)

Edit: Forget it, it's okay in the latest version=P thanks again

Well... There was a small error in my calculations which was corrected. I DID mistake the I_sp for Exhaust Velocity.

oh no, I know what bi-elliptic transfers do. it's just that I couldn't find a set of numbers to put into the calculator that gave that result, and I put forward a theory as to why that was the case...

From Wikipedia:

While it requires one more burn than a Hohmann transfer and generally requires a greater period of time, the bi-elliptic transfer may require a lower amount of total delta-v than a Hohmann transfer in situations where the ratio of final to the initial semi-major axis is greater than 11.94.

[XiXLLAMAXiX]

While it requires one more burn than a Hohmann transfer and generally requires a greater period of time, the bi-elliptic transfer may require a lower amount of total delta-v than a Hohmann transfer in situations where the ratio of final to the initial semi-major axis is greater than 11.94.

1. let's say you want to get from a circular orbit of 100km (semi major axis of 700km due to radius of Kearth) to a circular orbit of 7800km (700km * 12 ratio of semi major axis = 8400km, subtract 600km to account for radius of Kearth) regardless of what I set the turnover altitude to, the delta v value is dramatically lower for the Hohmann transfer than for the bi-elliptical transfer when I enter these numbers into the calculator. From this we can determine that either wikipedia is incorrect, or there is some small error in the calculator

2. Due to my inability to speak words good, I uploaded my next point in picture form. It pretty much outlines the reasons why I started to suspect that there was something wrong with the calculator. This is what I tried (and obviously failed) to explain in my first post....

Contrary to how I know I probably sound, I'm trying to be helpful =P

edit: I acknowledge the fact that I would be more helpful if I knew what was wrong rather than just the fact that there is something wrong...

[plazmaXIII]

a calculation that shows what angle and speed you will hit the main atmosphere (probably going to need it sooner or later. and its nice to know with space planes so you don't rip the wings off)

[Warringer]

1. let's say you want to get from a circular orbit of 100km (semi major axis of 700km due to radius of Kearth) to a circular orbit of 7800km (700km * 12 ratio of semi major axis = 8400km, subtract 600km to account for radius of Kearth) regardless of what I set the turnover altitude to, the delta v value is dramatically lower for the Hohmann transfer than for the bi-elliptical transfer when I enter these numbers into the calculator. From this we can determine that either wikipedia is incorrect, or there is some small error in the calculator

2. Due to my inability to speak words good, I uploaded my next point in picture form. It pretty much outlines the reasons why I started to suspect that there was something wrong with the calculator. This is what I tried (and obviously failed) to explain in my first post....

Contrary to how I know I probably sound, I'm trying to be helpful =P

edit: I acknowledge the fact that I would be more helpful if I knew what was wrong rather than just the fact that there is something wrong...

I plan to try and rebuild the entire calculator anyway. A bit better then a large set of cleanup...

But at the moment I have to study for a Computer Science test...

a calculation that shows what angle and speed you will hit the main atmosphere (probably going to need it sooner or later. and its nice to know with space planes so you don't rip the wings off)

For that I need a little more math then at the moment. It will go to my To-Do list through.

[Arrowstar]

1. let\'s say you want to get from a circular orbit of 100km (semi major axis of 700km due to radius of Kearth) to a circular orbit of 7800km (700km * 12 ratio of semi major axis = 8400km, subtract 600km to account for radius of Kearth) regardless of what I set the turnover altitude to, the delta v value is dramatically lower for the Hohmann transfer than for the bi-elliptical transfer when I enter these numbers into the calculator. From this we can determine that either wikipedia is incorrect, or there is some small error in the calculator

2. Due to my inability to speak words good, I uploaded my next point in picture form. It pretty much outlines the reasons why I started to suspect that there was something wrong with the calculator. This is what I tried (and obviously failed) to explain in my first post....

Contrary to how I know I probably sound, I\'m trying to be helpful =P

edit: I acknowledge the fact that I would be more helpful if I knew what was wrong rather than just the fact that there is something wrong...

They should NOT require the same amount of deltaV, no. Bi-elliptical transfer orbits tend to require more deltaV, except when the ratio of the final orbital radius to initial orbital radius (assuming you\'re starting from 0 eccentricity orbits, mind) is greater than 15.58. As an exercise, I\'ll let you work out the math, or you can just look this figure up online.

[tofof]

They should NOT require the same amount of deltaV, no. Bi-elliptical transfer orbits tend to require more deltaV....

Yes, they should. Look at the diagram. He\'s only talking about the /first burn/ of either transfer method. These put the craft into the same location (an elliptical orbit with apokee of 1000km and velocity of ~2650 m/s), and should require the same amount of delta V (~400, I get 403 when I use version 0.9.5\'s value for Hohmann, the attached diagram shows values of 404 for Hohmann or 415 for Bi-Elliptic).

For what it\'s worth I get utter nonsense for the bi-elliptic transfer injection in 0.9.5: Initial 2245, deltav 199, final 1847. This is for a low of 100km and turnover of 1000km - high doesn\'t matter. Sure seems like it should be the ~400 number (same as for Hohmann), or that at a bare minimum the initial+deltav=final, but neither of those is true.

[tofof]

Let\'s Experiment: roughly duplicate http://en.wikipedia.org/wiki/Bi-elliptic_transfer#Example.

Experiment 1, in which Bi-Elliptic should barely be more efficient.

Radius of Kerth: 600km.

Starting altitude: 100km. Initial radius, then, is 700km.

Desired final circular orbit: 10000km altitude. This is 10600 radius, or ~15x our starting radius.

Turnover altitude: 28000km. This is a radius of 28600, or ~41x our starting radius.

We\'ll Contrast this with a Hohmann transfer directly to 10000km.

[table]

[tr][td]Burn [/td][td]Hohmann dV [/td][td]Bi-elliptic dV[/td][/tr]

[tr][td]1[/td][td]830[/td][td]632 or 892[/td][/tr]

[tr][td]2[/td][td]374[/td][td]157[/td][/tr]

[tr][td]3[/td][td]-[/td][td]114[/td][/tr]

[tr][td]Total[/td][td]1204[/td][td]903 or 1163[/td][/tr]

[/table]

The struck out values above are given by the program. I believe the first should be 892 (the same as the first burn of a Hohmann transfer from 100km to 28000km). The total, then, also changes, obviously.

Note that, as expected, the Bi-elliptic is slightly more efficient in fuel than the Hohmann. This mirrors the Wikipedia article.

Experiment 2: In which Bi-elliptic should be less efficient

Now, let\'s experiment again, with a destination orbit that\'s lower than the magical 11.8 ratio. Let\'s say 5000 km (for a radius of 5600=8x our initial radius), using the same turnover altitude.

[table]

[tr][td]Burn [/td][td]Hohmann dV [/td][td]Bi-elliptic dV[/td][/tr]

[tr][td]1[/td][td]749[/td][td]632 or 892[/td][/tr]

[tr][td]2[/td][td]420[/td][td]104[/td][/tr]

[tr][td]3[/td][td]-[/td][td]215[/td][/tr]

[tr][td]Total[/td][td]1168[/td][td]951 or 1211[/td][/tr]

[/table]

If the value for the transfer orbit injection in the bi-elliptic calculator is correct, this still takes less delta-v. This can\'t be true for a ratio of the major axes that\'s only 8x. However, if we use the value for the same burn obtained using the Hohmann calculator (the same 892 as before), we see that the bi-elliptic is less efficient.

I think it\'s clear that the program is just giving the wrong values for delta v and final v for the 'transfer orbit injection' on the bi-elliptic page (and consequently also reporting the wrong total delta v needed). Really, the giveaway is the fact that the sum of the initial and the deltav doesn\'t produce the final. It\'s just clearly in error.

[Arrowstar]

Yes, they should. Look at the diagram. He\'s only talking about the /first burn/ of either transfer method.

Oh, I see. That\'s what I get for not reading carefully. My mistaken.

[Skyenet]

Quick suggestion, that may or may not have been mentioned already., since I\'ve been playing with (manned) ICBM experiments. What would be great is a tab in the calculator dealing with ballistic (sub-orbital) flight. It could be done on the very basic level with input of velocity, angle of velocity, height over ground/target and whatever Kerbal\'s g is, at least that is my very basic understanding of ballistic trajectories.

[tofof]

What would be great is a tab in the calculator dealing with ballistic (sub-orbital) flight.

I think that, unfortunately, the drag model would prevent it from being very accurate, since that can vary substantially from rocket to rocket.

[Doomydoom]

It\'s adding incorrectly in the Bi-Elliptic section. It says a 1949.12 m/s initial velocity plus 555.869 m/s of delta-v comes out to 2075.394 m/s, for example.

[Warringer]

I think I\'m going to remove the bi-elliptic transfer again...

Through I will add new options for the central body of the orbit. Well, at least as soon as I know the size of the Mun and its Sphere of Influence. Not to mention that if the Sun.

[Elve84]

This pack sounds intresting, how do i nistall it? Simply copy the files in the KSP_data folder? or somewhere else?

[Warringer]

This pack sounds intresting, how do i nistall it? Simply copy the files in the KSP_data folder? or somewhere else?

My dear friend, this is not an addon pack, but a stand alone java calculator for orbits around KEarth and in the future for the Mun and the Sun. You can put it where you want.

[SchildConstruct]

Added support for more celestrial bodies in the orbit calculations (KEarth, Mun*, Sun*)

Submitted a bug on Google Code about that...

[Warringer]

Submitted a bug on Google Code about that...

Smartass.

[SchildConstruct]

Smartass.

I think of myself more as a donkey.

[Red]

The calculator seems a tad inaccurate for required speed of a circular orbit (In the realm of decimeters per second), since the speed it gives results in an orbit that is off by a couple of km. (Ex: The speed it gives as a requirement of an orbit that is around 2871003 meters from Kerbin is somewhere around 1008.5 m/s, when it seems to be actually at around 1008.67 m/s)

[NovaSilisko]

The calculator seems a tad inaccurate for required speed of a circular orbit (In the realm of decimeters per second), since the speed it gives results in an orbit that is off by a couple of km. (Ex: The speed it gives as a requirement of an orbit that is around 2871003 meters from Kerbin is somewhere around 1008.5 m/s, when it seems to be actually at around 1008.67 m/s)

I believe this was using the old assumption that the mun would have the same ratio as earth\'s moon to earth.