The Museum of HP Calculators

# Planet Lander for the HP-41C/CV/CX

This program is Copyright © HP and is used here by permission. It was originally printed in the Games Solution Book. This program was entered and uploaded by Tony Duell. The documentation was entered by Dave Hicks. The Barcode for this program was provided by Brian Ward.

This program is supplied without representation or warranty of any kind. Tony Duell, Hewlett Packard and The Museum of HP Calculators therefore assume no responsibility and shall have no liability, consequential or otherwise, of any kind arising from the use of this program material or any part thereof.

## Overview

The object here is to perform a vertical descent ending in soft landing on the planet of your choosing. You select the planet before you begin by specifying the acceleration of gravity in feet per second per second. Some values are given below:

```Body             g(f/s2)
Earth            32.2
Moon              5.32
Mars             12.3
Ganymede          5.25
Pluto             7.25
Icarus (asteroid) 0.394
```

For interest, zero and negative values of g are allowed. The fuel allocated, as calculated from g, is more than adequate for a minimum use landing. At least twice as much fuel as needed is given. Although it takes longer to calculate, 3 seconds is the time your burn is stretched over. You can only key a burn in during the zero of each three second count down.

Note that if zero or negative g is selected and you run out of fuel, you may not impact. In this case you will see "DEEP SPACE. . ." instead of the normal "VF=" for final velocity.

## Instructions

 Step Instructions Input Data/Units Keys Output Data/Units 1 Enter program 2 Key in gravity. g(f/s2) [XEQ] GRAVITY G= 3 FUEL= *V= A= THREE... TWO... ONE... ZERO... 4 You have one second during the "ZERO..." prompt to key in a fuel burn. burn 5 Go to 3 for next status. 6 For a new game with the same g go to step 3. [A] G= 7 For a new game with a different g go to step 2. * When you see "VF= ", this is your landing or crash velocity.

## Example

Try a landing on the moon (g = 5.32 f/s2).

```   Keystrokes:          Display:
[XEQ] [ALPHA]
SIZE [ALPHA] 007
5.32 [XEQ] [ALPHA]
GRAVITY [ALPHA]         G=5.32
FUEL=5456
V=-500 F/S
A=5000 V
THREE...
TWO...
ONE...
ZERO...
(to free fall, just do nothing)
FUEL=5456
V=-516 F/S
A=3476 F
THREE...
TWO...
ONE...
ZERO...
20                      FUEL=5436
V=-512 F/S
A=1 934 F
THREE...
TWO...
ONE...
.
.
.
```

How to get this Program to your Calculator (via HP-IL, disk, wand, and fingers)
Download Binary (.raw) program for disk or PC HP-IL Card download
Download Hexadecimal (.dat) program for Serial Port download
Display the Program Barcode (.pdf) for printing and scanning

## Program Listing

```LINE  KEYS
01 LBL "GRAVITY"
02 SF 27
03 STO 01
04 ABS
05 800
06 *
07 1200
08 +
09 STO 05
10 LBL A
11 5000
12 STO 06
13 -500
14 STO 02
15 RCL 05
16 STO 03
17 "G="
18 FIX 02
19 CF 29
20 ARCL 01
21 AVIEW
22 PSE
23 FIX 00
24 LBL 09
25 "FUEL="
26 ARCL 03
27 AVIEW
28 PSE
29 RCL 02
30 RND
31 RCL 06
32 .5
33 "V"
34 X>Y?
35 "F"
36 "="
37 ARCL Z
38 " F/S"
39 AVIEW
40 PSE
41 X>Y?
42 RTN
43 "A="
44 ARCL 06
45 " F"
46 AVIEW
47 PSE
48 RCL 03
49 X=0?
50 GTO 02
51 "THREE..."
52 AVIEW
53 PSE
54 "TWO..."
55 AVIEW
56 PSE
57 "ONE..."
58 AVIEW
59 PSE
60 CLX
61 "ZERO..."
62 AVIEW
63 PSE
64 CLD
65 STO 00
66 ABS
67 RCL 03
68 X>Y?
69 RDN
70 ST- 03
71 RCL 00
72 SIGN
73 *
74 3
75 /
76 RCL 01
77 -
78 STO 04
79 RCL 06
80 *
81 2
82 *
83 RCL 02
84 X^2
85 X<>Y
86 -
87 SF 00
88 X<0?
89 GTO 01
90 SQRT
91 RCL 02
92 +
93 CHS
94 RCL 04
95 X=0?
96 GTO 01
97 CF 00
98 /
99 3
100 X<>Y
101 X>Y?
102 RDN
103 LBL 01
104 FS?C 00
105 3
106 STO 00
107 RCL 04
108 *
109 RCL 02
110 +
111 X<> 02
112 RCL 00
113 X^2
114 RCL 04
115 *
116 2
117 /
118 X<>Y
119 RCL 00
120 *
121 +
122 ST+ 06
123 GTO 09
124 LBL 02
125 "DEEP SPACE..."
126 RCL 01
127 X#0?
128 GTO 03
129 0
130 STO 06
131 RCL 02
132 X<0?
133 GTO 09
134 PROMPT
135 LBL 03
136 RCL 01
137 RCL 06
138 *
139 2
140 *
141 RCL 02
142 X^2
143 +
144 X<0?
145 PROMPT
146 SQRT
147 RCL 02
148 +
149 RCL 01
150 /
151 X<0?
152 PROMPT
153 RCL 01
154 *
155 ST- 02
156 0
157 STO 06
158 GTO 09
159 END
```