**Swiss
Micros DM42 and HP 42S: Moon
Landing Simulator from
the HP 33-E Applications Book**

**Landing
the Rocket**

The goal is to provide enough fuel to get the rocket to land on the moon safely. The use of fuel pushes the rocket away from the surface and slow down the descent. Don’t crash or use too much fuel to escape into space.

Variables:

X: Position

V: Velocity

F: Fuel

G: Gravity

B: Amount of Fuel to burn

Initial Values (from the HP-33E Applications):

X = 500

V = -50

F = 120

G = 5

I wasn't sure about the win condition (X = 0, V = 0?).

I show the position, velocity, and fuel after each successful turn. Enter the amount of units to burn at the burn prompt.

Download here: https://drive.google.com/file/d/1YsYzIMxALuRx_MHSSzGFFEQJdrN656DS/view?usp=sharing

**DM42
and HP 42S Code: MOON**

00 { 184-Byte Prgm }

01▸LBL "MOON"

02 500

03 STO "X"

04 -50

05 STO "V"

06 120

07 STO "F"

08 5

09 STO "G"

10▸LBL 01

11 "POS:"

12 ARCL "X"

13 AVIEW

14 STOP

15 "VEL:"

16 ARCL "V"

17 AVIEW

18 STOP

19 "FUEL:"

20 ARCL "F"

21 AVIEW

22 STOP

23 RCL "X"

24 X=0?

25 GTO 07

26▸LBL 02

27 "BURN?"

28 PROMPT

29 STO "B"

30 RCL "F"

31 X<Y?

32 GTO 05

33▸LBL 03

34 RCL "B"

35 STO- "F"

36 RCL- "G"

37 STO "A"

38 RCL "V"

39 RCL+ "X"

40 RCL "A"

41 2

42 ÷

43 +

44 STO "X"

45 X≥0?

46 GTO 04

47 GTO 06

48▸LBL 04

49 RCL "V"

50 RCL+ "A"

51 STO "V"

52 GTO 01

53▸LBL 05

54 2

55 RCL× "G"

56 RCL "V"

57 X↑2

58 +

59 SQRT

60 +/-

61 STO "V"

62▸LBL 06

63 "VEL:"

64 ARCL "V"

65 AVIEW

66 "YOU LOSE"

67 AVIEW

68 RTN

69▸LBL 07

70 "SUCCESS!"

71 AVIEW

72 .END.

**Example
Game**

XEQ "MOON"

Initial Turn

POS: 500

VEL: -50

FUEL: 120

BURN? 0

POS: 447.5

VEL: -55

FUEL: 120

BURN? 0

POS: 390

VEL: -60

FUEL: 120

BURN? 0

POS: 327.5

VEL: -65

FUEL: 120

BURN? 5

POS: 262.5

VEL: -65

FUEL: 115

BURN? 0

POS: 195

VEL: -70

FUEL: 115

BURN? 5

POS: 125

VEL: -70

FUEL: 115

BURN? 10

POS: 57.5

VEL: -65

FUEL: 100

BURN? 12.5

"YOU LOSE" -3.75

So close. Good luck!

**Source**

__HP-33
Applications__.
Hewlett Packard. Corvallis, OR. February 1978

Eddie

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