TI-BASIC orbital Calculator

[Rory Yammomoto]

I have been developing a method to automatically calculate the orbital elements of a spacecraft with a Texas Instruments TI-84 Plus calculator. My script, which has been posted below, does not need (but can use) the apsides of an orbit to continue, operating on the Vis-Viva Equation. All that is needed is a reference altitude and velocity, the radius of the current body, and the Standard Gravitational Parameter of the current body. After only a week, the script has reached a high level of development, and can calculate Gilly's orbit with a 2%-13% error. As such, I feel it is ready for release and testing.

 

Feel free to change the program however you feel, as I want this script to be the greatest external orbit calculator it can be.

NEEDS:

•  A Texas Instruments Zilog Z80-based calculator (or the means  to emulate one)
• A way to transfer scripts to said calculator

BOSH. Google Drive Link.

Plain Text Code:

Spoiler

 

ClrHome
Disp "ORBIT FINDER----
Disp "VERSION 5.*","","","",""
Disp "***PRESS ENTER**
Pause

ClrHome
Disp "APOAPSIS?-------","([e] IF N/A)
Prompt Y

ClrHome
Disp "PERIAPSIS?------","([e] IF N/A)
Prompt X

ClrHome
Disp "ALT/VEL?--------
Prompt R
Prompt V

ClrHome
Disp "BODY RADIUS?----
Prompt C

ClrHome
Disp "STND GRAV PARAM?
Prompt K

If Y=[e] or X=[e]
Then

ClrHome
Disp "USING VISV CALCS
((2/(R+C))-(V^^2/K))^^-1->A

Disp "SEMIMAJOR AXIS--
Disp A
Pause

Goto N

Else
((X+C)+(Y+C))/2->A
Disp "USING AP/PE CALC
Disp "SEMIMAJOR AXIS--
Disp A
Pause
    
Lbl N
End

2pisqrt(A^^3/K)->P

ClrHome
Disp "PERIOD----------"
Disp P
Pause

((.5(C+R)VP)/(piA))->B

ClrHome
Disp "SEMIMINOR AXIS--
Disp B
Pause
sqrt(1-(B^^2/A^^2))->E

ClrHome
Disp "ECCENTRICITY----
Disp E
Pause
Disp "CALC AP and PE?,"",""
Disp "(F5 TO CONTINUE)
Repeat Ans
getKey->theta
End

P
If theta=15
then
A(1-E)->Y
A(1+E)->X
ClrHome
Disp "ORBIT ELEMENTS
Disp "AP=",X
Disp "PE=",Y
Disp "E=",E
Pause
Goto theta
Else
    
    
Lbl theta
End
Stop

 

Edited October 19, 2016 by Rory Yammomoto

[Snark]

Moving to Tools & Applications, since this isn't an add-on for KSP.

[Rory Yammomoto]

OK, this has a major problem. Eccentricity is not calculated correctly, and when calculating the apsides, the equations given seem to have a tendency to set your current altitude to the periapsis or apoapsis (whichever is closest, strangely; one would assume if its failing it would make a point that your orbit does not reach.) I need some help. I am accepting suggestions for improvements.

EDIT: Turns out that thee equation I am using is used only to compute SMA while at the apsides.

ANOTHER EDIT: the equation was input incorrectly. The program works anywhere now.

Edited December 5, 2016 by Rory Yammomoto