Lunar Lander for the HP-55

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The program presented below will simulate a lunar lander on the HP-55. It was written by Ron Emery and John Olglesby and appeared in the V4N4P10 issue of the PPC Journal (April 1977). Thanks Guys!

Instructions:
0) Key the program in. Switch to RUN mode.
1) Store these constants: 500 STO 0, -50 STO 1, 120 STO 2.
2) Set up the display into FIX 0 mode and press the BST key.
3) Key in your one second fuel burn and press R/S.
4) Display will show your new velocity. To see the new altitude, press RCL 0. To see your new remaining fuel, press RCL 2.
5) Continue with step 4 until you land or run out of fuel. The display will go to FIX 9 mode.
6) If the final velocity shown is negative, it means you crashed with fuel remaining.
7) If the final velocity shown is positive, you must calculate the final velocity by pressing *, +, then SQRT.

Program Listing: Note: The keycodes below that are negative are actually GTO commands as part of the conditional test. For example, the X = Y at step 4 shows a keycode of -07. That is saying that if X = Y, execution should continue at step 7. The X < = Y command at step 6 shows a keycode of -35. That means that if the conditional test is true, execution should continue at step 35. Email if you have any questions.
```Line      Instruction  Keycode
01         RCL          34
02         2            02
03         g            32
04         X = Y       -07
05         f            31
06         X < = Y     -35
07         RDN          23
08         STO          33
09         -            51
10         2            02
11         5            05
12         -            51
13         STO          33
14         3            03
15         2            02
16         %            81
17         RCL          34
18         0            00
19         +            61
20         RCL          34
21         1            01
22         +            61
23         STO          33
24         0            00
25         0            00
26         f            31
27         X < = Y     -29
28         GTO 46      -46
29         RCL          34
30         3            03
31         STO          33
32         +            61
33         1            01
34         GTO 48      -48
35         RCL          34
36         1            01
37         g            32
38         X^2          42
39         RCL          34
40         0            00
41         1            01
42         0            00
43         STO          33
44         1            01
45         RDN          23
46         FIX          24
47         9            09
48         RCL          34
49         1            01
```

That's it!
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