I've made little more progress in deciphering the operation of Carl Claunch's "Lunar Landing" program, as featured in one of his 1130 YouTube videos. (I'm guessing he's the actual author of the program -- he mentions on one of his blogs that he was interested in space before he became interested in computers.)
Recent (official) bug fixes to SimH have made it much easier to input data to the 1130 console when the GUI is active (you no longer need to type Return first, to unlock the console keyboard). I finally realized that responses to the console's "ENTER ANGLE" and "ENTER VELOCITY" prompts can be left-justified numbers, as long as they're followed by a decimal point. If you make a typing mistake, it would seem that Backspace, <ctrl>H and <ctrl>U all do the same thing -- erase the entire field. The characters already typed don't disappear, the cursor just goes to the beginning of the next line. The data switches mentioned in the introductory console message are switch positions (on the GUI) counting (starting with 0) from the left, not binary numbers. "4 = SKIP TO PLOT OPTION" means "flip up switch #4" -- not, in SimH terms, "deposit ces 4" which would turn on switch #13. If switch #4 is turned on, "examine ces" gives (hex) 800. The switches apparently really do what they're indicated as doing in the introductory console message. E.g., if you turn on switch #1 (TRACE EVERY TENTH ITERATION), then columns of numbers will appear on the lineprinter underneath the headings HOUR MIN 'X' COORD. 'Y' COORD. etc. These seem to show the progress of the flight, about every (virtual) 18 minutes. The ANGLE and VELOCITY values prompted for appear to be **initial conditions** of a flight, so the reappearance of these prompts on the console means that your trip has ended and a new one is beginning (unless switch #6 is turned on, in which case the program exits when the current flight terminates). This only slowly dawned on me -- at first I figured the re-entered values were a means of steering the spaceship, or something. Fine-tuning a flight is apparently done by turning on switch #2 (ENTER MID-COURSE VELOCITY CORRECTION). If this switch is turned on, you get a new prompt on the console, something like VELOCITY IS 27485. MPH, DIST. TO EARTH, 4058. MILES, AND 239034. MILES TO THE MOON ENTER VELOCITY CORRECTION and you type in something like, I don't know, 1000. and the prompt is repeated with the new velocity and recomputed distances. And again, and so forth. You only seem to get a graphical plot of your trajectory when the flight has terminated. Then you see PLOT DIAGRAM IS READY. and the 1130 goes into a wait state. When you continue from there, you get the ENTER ANGLE prompt, etc. The trajectory plot for a given flight doesn't seem to appear on the lineprinter until the **succeeding** flight has terminated. The visible trajectory plot always seems to be one flight behind the one just terminated. I don't know what that's about. Also, the angle measurement described in the console instructions -- "ANGLE IS MEASURED COUNTER-CLOCKWISE FROM THE LINE BETWEEN THE EARTH AND THE MOON" -- doesn't seem to match my trial and error. If I give an angle of 0. and a very large value velocity (say, 100000.) then the trajectory plot goes vertically straight up the page, perpendicular to the line between the earth and the moon. If I enter an angle of -90. and a similarly high speed, then the trajectory goes straight toward the moon. So I don't know if the instruction message is 90 degrees off or if I'm missing something. At least the "counterclockwise" part seems to be right. I don't yet know what causes a flight to terminate, well before it gets anywhere near the moon. Maybe the idea is to try to get a hole-in-one by picking perfect initial conditions. Maybe the flight automatically terminates when the ship is so off course that the program decides the flight has failed. I don't know what's supposed to happen if you actually manage to get near the moon -- whether there's some sort of braking and landing procedure in the program. I am able to run the program using the DMS disk from bitsavers configured for 32kw of memory, the 2501 card reader, and the 1403 printer. (I had to use the "viewdeck" utility from ibm1130.org and some other things, like Cygwin 'dd', to split up the original binary deck into two human-readable pieces and one other component [the "ORBIT" subroutine] that has to stay binary. The main program can be made human-readable, and that's where the Fortran logical unit number for the printer is defined, and can be changed.) I may finally give up and attempt to contact Claunch for hints about how to use his (I presume it's his) program. But I'm reluctant to do so, partly because it's fun to try to figure it out myself, and partly because I don't want to bother or embarrass him. I know he's posted here in the past, though, so he may see this anyway.