The Museum of HP Calculators The Museum of HP Calculators
This program is Copyright © 1977 by Hewlett-Packard and is used here by permission. This program was originally published in "HP-19C/HP-29C Applications Book", pages 49 through 51. This program was transcribed by Mark Lynch
This program is supplied without representation or warranty of any kind. Hewlett-Packard Company 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.
Imagine for a moment the difficulties involved in landing a rocket on the moon with a strictly limited fuel supply. You're coming down tail-first, free-falling toward a hard rock surface. You'll have to ignite your rockets to slow your descent; but if you burn too much too soon, you'll run out of fuel 100 feet up, and then you'll have nothing to look forward to but cold eternal moon rocks coming faster every second. The object, clearly, is to space your burns just right so that you will alight on the moon's surface with no downward velocity.
The game starts off with the rocket descending at a velocity of 50 feet/second from a height of 500 feet. The velocity and altitude are shown in a combined display as -50.0500, the altitude appearing to the right of the decimal point and the velocity to the left, with a negative sign on the velocity to indicate downward motion. Then the remaining fuel is displayed and the rocket fire count-down begins: "3", "2", "1", "0",. Exactly at zero you may key in a fuel burn. You only have one second, so be ready. A zero burn, which is very common, is accomplished by doing nothing. After a burn the sequence is repeated unless:
1. You have successfully landed - flashing zeros.
2. You have smashed into the lunar surface - flashing crash velocity.
You must take care, however, not to burn more fuel than you have; for if you do, you will free-fall to your doom! The final velocity shown will be your impact velocity (generally rather high). You have 60 units of fuel initially.
We don't want to get too specific, because that would spoil the fun of the game; but rest assured that the program is solidly based on some old friends from Newtonian physics:
x = x0+V0t + (1/2)at2
V=V0 + at
V2 = V02 + 2a (x - x0)
where x, V, a, and t are distance, velocity, acceleration, and time.
Remarks:
Only integer values for fuel burn are allowed. R/S can be used to stop Moon Rocket Lander at any time.
| Step | Instructions | Input Data/Units | Keys | Output Data/Units |
| 1 | Key in the program. | |||
| 2 | Assume manual control. | GSB 1 | "V.ALT" | |
| "FUEL" | ||||
| "3" | ||||
| "2" | ||||
| "1" | ||||
| "0" | ||||
| 3 | Key in burn upon "0" display: | |||
| Press and hold R/S until | ||||
| blinking stops. | R/S | |||
| Enter burn | BURN | R/S | "V.ALT" | |
| "FUEL" | ||||
| "3" | ||||
| "2" | ||||
| "1" | ||||
| "0" | ||||
| 4 | Go to step 3 until you land | |||
| (flashing zeros) or crash | ||||
| (flashing impact velocity). | ||||
| 5 | If you survived last landing | |||
| attempt, go to step 2 for another | ||||
| try. |
19C 29C LINE CODE CODE KEYS COMMENTS 00 01 25 14 01 15 13 01 g LBL 1 02 05 05 5 03 00 00 0 Store initial conditions 04 00 00 0 05 45 06 23 06 STO 6 06 05 05 5 07 00 00 0 08 22 32 CHS 09 45 07 23 07 STO 7 10 06 06 6 11 00 00 0 12 45 08 23 08 STO 8 13 25 14 00 15 13 00 g LBL 0 ------------------------- 14 55 06 24 06 RCL 6 15 16 13 04 14 11 04 f FIX 4 16 23 33 EEX Divide height by 10000 17 04 04 4 for proper display 18 61 71 ÷ ------------------------- 19 55 07 24 07 RCL 7 20 25 54 15 64 g ABS Build VV.Ohhh display, 21 41 51 + taking negative values 22 55 07 24 07 RCL 7 into account 23 25 41 15 51 g x>0 24 13 04 12 04 GSB 4 25 11 21 x⇔y 26 22 32 CHS ------------------------- 27 16 64 14 74 f PSE Display VV.Ohhhh 28 16 64 14 74 f PSE ------------------------- 29 16 13 00 14 11 00 f FIX 0 30 55 08 24 08 RCL 8 31 16 64 14 74 f PSE 32 03 03 3 Count down for burn 33 16 64 14 74 f PSE 34 02 02 2 35 16 64 14 74 f PSE 36 01 01 1 37 16 64 14 74 f PSE 38 00 00 0 39 16 64 14 74 f PSE ------------------------- 40 25 14 09 15 13 09 g LBL 9 Accept input 41 55 08 24 08 RCL 8 ------------------------- 42 11 21 x⇔y If fuel is gone calculate 43 16 41 14 51 f x>y crash velocity 44 14 06 13 06 GTO 6 ------------------------- 45 45 31 08 23 41 08 STO - 8 46 02 02 2 47 51 61 x Determine velocity and 48 05 05 5 height 49 31 41 - 50 45 09 23 09 STO 9 51 02 02 2 52 61 71 ÷ 53 55 06 24 06 RCL 6 54 41 51 + 55 55 07 24 07 RCL 7 56 41 51 + 57 55 09 24 09 RCL 9 58 45 41 07 23 51 07 STO + 7 59 12 22 R↓ 60 45 06 23 06 STO 6 61 16 52 14 62 f INT ------------------------- 62 25 41 15 51 g x>0 If no impact go for 63 14 00 13 00 GTO 0 another burn 64 55 07 24 07 RCL 7 ------------------------- 65 25 14 07 15 13 07 g LBL 7 66 16 64 14 74 f PSE Flash crash velocity 67 14 07 13 07 GTO 7 68 25 14 06 15 13 06 g LBL 6 ------------------------- 69 55 08 24 08 RCL 8 Fuel exhausted: 70 02 02 2 call free-fall crash 71 63 73 . velocity 72 05 05 5 73 31 41 - 74 45 41 06 23 51 06 STO + 6 75 02 02 2 76 51 61 x 77 45 41 07 23 51 07 STO + 7 78 55 06 24 06 RCL 6 79 01 01 1 80 00 00 0 81 51 61 x 82 55 07 24 07 RCL 7 83 25 53 15 63 g x2 84 41 51 + 85 16 53 14 63 f √x 86 22 32 CHS 87 14 07 13 07 GTO 7 88 25 14 04 15 13 04 g LBL 4 89 11 21 x⇔y 90 22 32 CHS 91 11 21 x⇔y 92 25 13 15 12 g RTN
R6 x R7 V R8 Fuel R9 Acceleration
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