10REM Program ORBIT 20REM Version B2.0 30REM Author Cliff Blake 40REM BEEBUG March 1993 50REM Program subject to copyright 60: 100MODE7:*FX11 110PROCinfo:g%=GET 120MODE0:VDU5 130REPEAT 140quit%=FALSE 150CLS:PROCplanet:PROCspaceship 160REPEAT 170rerun%=FALSE 180PROCmove:PROCaltitude 190PROCgravity:PROCthrust 200PROCflags 210UNTIL rerun% 220UNTIL quit% 230VDU4:*FX12 240CLS:*FX21 250END 260: 1000DEF PROCmove 1010MOVE Xs,Ys:PRINT CHR$64 1020ENDPROC 1030: 1040DEF PROCaltitude 1050Xd=640-Xs:Yd=512-Ys 1060Rds=Xd*Xd+Yd*Yd:Rd=SQR(Rds) 1070alt%=INT(.2*Rd) 1080VDU4:PRINT TAB(55,2)"ALTITUDE: ";al t%;",000 km";SPC3:VDU5 1090ENDPROC 1100: 1110DEF PROCgravity 1120Xg=20000*Xd/Rd/Rds:Yg=20000*Yd/Rd/R ds 1130Xv=Xv+Xg:Yv=Yv+Yg 1140Rvs=Xv*Xv+Yv*Yv:Rv=SQR(Rvs) 1150vel%=INT(.85*Rv) 1160VDU4:PRINT TAB(55,4)"VELOCITY: ";ve l%;",000 km/h";SPC3:VDU5 1170ENDPROC 1180: 1190DEF PROCthrust 1200Xt=0.05*Xv/Rv:Yt=0.05*Yv/Rv 1210IF INKEY(-103) THEN Xv=Xv-Xt:Yv=Yv- Yt:SOUND0,-7,6,4 1220IF INKEY(-104) THEN Xv=Xv+Xt:Yv=Yv+ Yt:SOUND0,-7,6,4 1230Xs=Xs+Xv:Ys=Ys+Yv 1240ENDPROC 1250: 1260DEF PROCflags 1270IF INKEY(-52) THEN rerun%=TRUE 1280IF INKEY(-17) THEN rerun%=TRUE:quit %=TRUE 1290ENDPROC 1300: 1310DEF PROCplanet 1320Ca=COS(PI/40):Sa=SIN(PI/40) 1330CA=1:SA=0:MOVE 640+40,512 1340FOR A=1 TO 80 1350Cp=CA:Sp=SA 1360CA=Cp*Ca-Sp*Sa:SA=Sp*Ca+Cp*Sa 1370x=40*CA+640:y=40*SA+512 1380MOVE 640,512:PLOT 85,x,y 1390NEXT A 1400ENDPROC 1410: 1420DEF PROCspaceship 1430VDU23,64,192,0,0,0,0,0,0,0 1440Xs=640:Ys=900 1450Xv=3.5:Yv=0 1460ENDPROC 1470: 1480DEF PROCinfo 1490y$=CHR$131:c$=CHR$134:w$=CHR$135 1500PRINT TAB(10,2)y$+"SATELLITE ORBIT" 1510PRINT'c$+"A spaceship is in ellipti cal orbit" 1520PRINT c$+"around a planet. Try usin g its" 1530PRINT c$+"propulsion and retro brak ing units" 1540PRINT c$+"to make the orbit circula r." 1550PRINT'w$+"Gently holding down the < key will" 1560PRINT w$+"fire the retro unit to sl ow the ship." 1570PRINT'w$+"Gently holding down the > key will" 1580PRINT w$+"fire the drive to acceler ate the ship."' 1590PRINT c$+"The smaller the variation s in" 1600PRINT c$+"altitude and velocity, th e more" 1610PRINT c$+"circular the orbit." 1620PRINT'w$+"Press any key to start." 1630PRINT'w$+"Press R to clear the scre en & Repeat." 1640PRINT'w$+"Press Q to Quit." 1650ENDPROC