Without even looking, the engineers knew full well why engine no. 2 had self-destructed: It had become infected.
You need to understand how spacetime engines operate. They don't really exist. They do and they don't. They're housed in a metal sphere about ten feet in diameter. Attached to this sphere are any number of cables. No drive shaft, nothing of that sort. Just inputs and outputs. Information in, information out.
And if you unbolt one of the engine's exterior panels and look inside, you won't see anything. There's nothing to see. You would expect it to be full of all kinds of modules and wires and circuits. There's not even plasma. There's nothing in there.
...nothing you can see, anyway...
...Because the very act of looking verifies the reality that the engineers expect: that there is nothing inside. It is designed to be empty. It is nothing and everything at once. Obviously, then, it cannot be something.
The engine's function, as you might expect, is to propel the ship. But it does not do this by moving the ship through 3-space. Instead, the engine collapses successive wave functions so that reality is altered in such a fashion as to place the ship into the desired location in four dimensions.
That's how the ship "moves."
"But how is the engine constructed? How does it do anything?"
You will notice a packet of schematics pasted on the outside of the engine. If you examine these schematics, you will see that they detail all the circuitry that is contained within the engine. The schematics represent the informational content of the engine.
"But there's nothing in the engine."
...Nor will there be while you are looking. It's nothing and everything at once, remember?
So the engineers already knew what happened to engine no. 2: It had become infected by foreign information, a virulent meme. The intention watchdog had failed and the engine never properly shut itself down. It self-destructed. But since the time of the ship's original construction, the engineers have beefed up the watchdog circuitry. It's on the list for the overhaul.
We're working on the one functioning engine right now. That one had an infection as well, though nowhere near as advanced. We know it's infected because when we run a test pattern through it, what we get out is some distorted version of expected reality. It shouldn't be distorted. Its fidelity should be perfect. With the engine in diagnostic mode, what we put in is what we should get out.
What is this test pattern? If you remember the old days of the electromechanical Teletype printers, they operated by sensing a pattern of electrical signals --varying voltages, say, of a particular duration, kind of like the audio sounds of a fax machine, maybe-- and then relays and switches and gears and pulleys inside would all work together to cause a metal letter to strike the paper. The test pattern used was the quick brown fox jumped over the lazy dogs back. You will notice that this sentence is the shortest phrase that uses all twenty-six letters of the alphabet. Every teletype repairman used this input to check a printer's output. He made adjustments on the printer while this phrase was input on a repeating loop of punched-paper tape.
The engineers are repairing engine no. 1. They make their adjustments on the engine while inputting a repeating sequence. This sequence is the shortest meme that exercises a spacetime engine's ability to transduce intention into usable energy. They are tweaking function collapse.
