Apollo 11 ignition
A routine in the lunar module, named like a radio shout, lit the engine.
Don Eyles and Peter Adler, 1969. Routine BURN_BABY_BURN.
The lunar module did not land the way a helicopter lands, with a hand on a collective and a view of the ground. It landed because a small computer ran a program and decided when the engine should light. The computer was the Apollo Guidance Computer. The program, for the lunar module, was called Luminary. Both came from the MIT Instrumentation Laboratory, the group that later took the name of Charles Stark Draper. The machine was slow, and its memory was small. The fixed program lived in core rope, wires threaded through tiny magnetic cores so that a bit was a path a needle had taken. The changeable memory was a couple of thousand words. Into that space the laboratory put the navigation, the guidance, and the burns.
Luminary had a sibling. The command module flew Colossus. Astronauts spoke to either program through the display and keyboard, the DSKY, in a dialect of verbs and nouns. A verb was an action. A noun was the thing the action concerned. The crew did not edit source in flight. They called routines that people on the ground had already argued over, line by line, in a listing.
Margaret Hamilton led the software engineering effort that made those listings into a discipline. Don Eyles worked on the powered flight the crew would trust in the last minutes of the descent. Peter Adler worked with him on the routine that starts a burn. They gave it a name that does not sound like a NASA form: BURN_BABY_BURN. Eyles has traced the phrase to Magnificent Montague, a disc jockey whose shout left the radio and landed in a guidance computer. The name is a joke that survived because the listing was the program. A comment in that listing was not decoration. It was how the next reader, years later, would know what the table was for.
The routine is the master ignition sequence for several lunar-module burns, landing and ascent among them. Callers do not hand it a loose list of numbers. They hand it a table of constants and transfers. The code indexes the table. It begins its checks well before time of ignition, on the order of three quarters of a minute, and it stays with the burn through the moment, a few tens of seconds later, when a descent engine is allowed to throttle up. There is no tidy return to a caller that then goes on with other business. The burn is the business.
That is why the picture is tall. The bars start at those tables, the ones tied to the programs that request a burn, and they run into the label BURNBABY. Each bar is one line of the assembly listing. A comment takes one color, a name another, an opcode another. Indent is the column the printer already used. No letter survives onto the ceramic. The story of the name stays here.
People sometimes fold this routine into a different famous episode. During the landing the computer raised program alarms, 1201 and 1202, because the executive was being offered more jobs than it could schedule. The rendezvous radar was adding work. The software shed the less important jobs and kept the guidance that was flying the vehicle. That recovery is not BURN_BABY_BURN. It sits in the same body of code, written by the same kind of people, under the same constraint: if the computer restarts, the engine must not become a mystery. Readers still open the listing because both stories are in it. Eyles later set his own account down in a book. The mug does not carry that book either.
NASA software of that era is in the public domain. The piece is marked clear for that reason. A visitor who buys the mug is buying the color of the listing, not a plaque with the DJ's name on it. The credit, the public-domain status, and this history stay on the page. The object gets the bars.
A buyer does not need the assembly manual to see the structure. Long runs of similar lines are the tables. A break in the rhythm is a label or a call. The colors separate comment from instruction without restoring the words. That is the whole offer of the object: the listing as a woven pattern, readable as architecture, not as a program you could type back in. The public-domain listing is still in the libraries and on the web for anyone who wants the opcodes. This page tells you whose joke the name was, and whose laboratory flew it.