The saucer with the panels off

The saucer. An octagon of 2020 aluminum extrusion, 87⅛ inches across the flats, a clear 24-inch dome, an alien pilot who has never asked for a raise, and 1,406 LEDs on four data lines from an ESP32-S3 board.

The banner. 1,500 WS2812B LEDs, 300 x 5, serpentine, on a thumbnail-size ESP32-C6 board. A quiet show all year so the neighbors don't get suspicious; a departures board in October.

The garage eyes. Two 16x16 WS2812B panels behind two garage door windows, on their own ESP32-C6 board. They blink. They look around. They know.

Gate 20. A single-board computer and a 15.6-inch USB monitor, held up by an inflatable alien.

Mission control. A web page and a phone app I run the yard from: pin a scene, set the brightness, change the floodlights, feel powerful.

Banner 1,500; saucer 440 + 115 + 480 + 241 + 128 + 2 = 1,406; eyes 2 x 256 = 512.

Before touching the banner again I built a desktop simulator that compiles the real firmware engine against a stub of FastLED and draws the strip in a browser. It models the wire time too. A WS2812B bit is 1.25 µs, so 24 bits is 30 µs per LED, and 1,500 LEDs on one data line is 45 ms plus the latch: about 21 frames a second, flat out. Better to learn that from a chair than from a ladder.

The banner's engine runs in three places: on the board, in the simulator and in the phone app's preview. The phone preview caught a real bug before it reached the wall: after waking up at night, the autopilot stayed asleep. Relatable.

The saucer's show went the other way round. I wrote it first as pure functions in JavaScript, in a 3D browser sim of the saucer, then ported it line for line to C++ for the Nano ESP32 and checked the two against each other pixel by pixel. The sim is where the look got decided. The port is where it got real.

The frame came together on the driveway. Linux, my tiny flight engineer, did the final flight check on the dome. The skin went on the same week: Aluminet, an aluminized shade cloth, top and belly, pulled tight from the rim to the hub.

The fog machine and the beam pods (with their 12 V supply and MOSFET) came off the manifest the same day, and so did the screw terminals. Every part you take out is a part that can't fail at 8 pm with a line of kids watching.

It's two stacked protoboards. Board A holds the Nano ESP32 on headers and a 74AHCT125 in a socket (so the chip is never soldered), with a 0.1 µF ceramic beside it. Board B is where the outside world lands: four 330 Ω series resistors, one per data line, a 100 µF can across the 5 V input, and solder points for four two-wire cables (DATA plus a GND reference) and the 5 V feed from the power box's fuse. Six short wires join the two boards. No screw terminals: every wire soldered straight into its hole, one wire per step, 35 steps.

Why the level shifter: the ESP32 drives 3.3 V logic, and a WS2812B powered at 5 V wants 0.7 x VDD, 3.5 V, for a clean high. Sometimes it reads 3.3 V anyway. Sometimes is not a word you want in a flight record. The 74AHCT125 has TTL input thresholds, so 3.3 V is a solid high, and its outputs swing the full 5 V. The 330 Ω resistors take the ringing off the edges on the way down the cables.

Pixel power doesn't go through the controller at all. The power box feeds each run through its own inline fuse, with a 100 µF capacitor at each strip start. The controller only sends data, plus a ground for the data to be measured against.

The bench test runs test firmware that lights all four lines at once, each in its own color (rim green, dome blue, spokes purple, portholes cyan), with a short test strip moved from cable to cable. Three of the four lit the first time. The rim stayed dark. I went down the chain with a meter, found it at the first resistor, and then everything lit.

I also drew the controller as a proper circuit board, HULL/20 on the silkscreen and all. That drawing is from 17 October, before the screw terminals came off, and it stayed a drawing. The one flying is the hand-wired stack.

The next night it lit up in the garage: 1,406 LEDs. I counted. So did the firmware. We agree.

The show is a small state machine, the same one in the sim and on the board:

static const float PH_CHARGE = 2.0f, PH_BEAM = 4.5f, PH_LIFT = 8.0f,
  PH_FLASH = 9.6f, PH_BLACK = 9.75f, PH_RELEASE = 10.05f, PH_END = 11.2f;
static const uint8_t IRIS_RINGS[9] =
  { 1, 8, 12, 16, 24, 32, 40, 48, 60 };   // 241 LEDs

Full white on 1,406 LEDs is roughly 87 A on paper at 20 mA a channel (1,291 RGB at 60 mA, 115 RGBW at 80 mA). The supply is a 350 W enclosed supply, 5 V and 60 A, and I'd rather not ask it for everything, so every frame is summed before it goes out and scaled down if it would go over 30 A. From the simulator; the firmware does the same thing, with less commentary:

// ~20 mA per channel at 255
export function frameAmps(buf) { let s = 0;
  for (let k = 0; k < buf.length; k++) s += buf[k];
  return (s / 255) * 0.020; }
export function limitFrame(saucerBuf, cap, limitA) {
  const raw = frameAmps(saucerBuf) * cap;
  const k = raw > limitA ? (cap * limitA) / raw : cap;
  return { scale: k, rawAmps: raw, amps: Math.min(raw, limitA) };
}

The saucer faces the street, so it holds one hard line: no part of it flashes more than 3 times a second, the usual photosensitive safety line. My first version flickered 16 to 30 times a second in places, which is less "visitor from another world" and more "nightclub". Every flicker now steps on one shared clock at 4 changes a second, sparkle became fades, and the turbine tops out at 2 turns a second.

I wrote a flash counter that renders the show at 64 frames a second, measures every rim face, porthole and spoke, and counts flashes in every one-second window, across 300 random seeds and every command the show accepts. It found one I couldn't see: during the charge, a bright comet ran around the eight portholes. Each window flashed slowly, but the ring as a whole pulsed 12 times a second.

The fix is a lobe of ((1 + cos φ) / 2)⁴, the porthole's brightness as a function of its angle from the sweep. Expand it and it's a polynomial of degree 4 in cos φ, so it has no harmonic above the 4th. Sum it over eight evenly spaced windows and every harmonic from the 1st to the 7th cancels, which leaves only the constant: the ring's total brightness stays flat while the lobe goes round. It still looks like it's spinning. The math just stopped it from shouting. Now 0 of 300 seeds go over the line.

// one sweep at 1.5 a second. A cos^4 lobe has no harmonic above the 4th,
// so over 8 evenly spaced windows the ring's total stays constant.
float b = powf(0.5f + 0.5f * cosf(2 * (float)M_PI
  * (frac(st.t * 1.5f) - aw)), 4);
set(o, CYAN, 0.08f + 0.4f * sstep(PH_CHARGE, PH_BEAM, s));
add(o, lerpC(CYAN, HOT, sp), b);

The saucer takes updates over Wi-Fi with a password. In the driveway, inside an aluminum frame, an aluminum box and shade cloth, 11 tries in a row stopped partway, each at a different point. It looks like the board restarts mid-transfer. The one update that ever landed out there had USB power plugged in as well. So updates go over the cable now, and the current firmware turns the Wi-Fi modem's power saving off. In space, no one can hear your Wi-Fi.

Every update lands in the other of two flash slots, so the slot doesn't tell you what's running. Each build now prints its own build id on the serial line at boot, so I always know which version of me wrote the bug.

Every board runs its own show. If the Wi-Fi goes down, the saucer, the banner and the eyes carry on like professionals. A small server in the house sits on top: the control panel and the phone app talk to it, and it talks to the banner and the eyes through a message broker. It feeds the banner live data, like planes and ISS passes overhead, and it runs the four floodlights. A person detector on an outside camera tells the banner when someone walks by, and the banner answers with a soft glow that walks along with them. The saucer doesn't listen to the network at all yet. It runs its show and minds its own business, like a good saucer.

Gate 20 is a single-board computer running an airport departures loop. From 15 to 31 October, every evening from 6 to 11, it showed a code for that hour's planet, and scanning it put the stamp in a Planet Hopper passport on the visitor's own phone. Six stamps made a Grand Tour. The red flag on the 16th switched it to RED FLAG WARNING, FLIGHTS HELD until 8 pm on the 17th; passport control stayed open, because paperwork waits for no weather.

A spaceport without announcements is just a driveway with ambitions.

The theme. An original 27-second HULL/20 theme, synthesised from scratch in Python with numpy and scipy, no samples: a theremin lead, a walking upright bass, brushes, an FM electric piano and airline chimes, at 100 BPM and cut to the reel's beat grid. Three styles were on the table: lounge, abduction and surf-rocket. Lounge won. It's a spaceport, not a getaway.

The voices. Kokoro text-to-speech, run locally, one voice per role: gate agent, Captain Vrell, passport control, purser, adverts, paging, NAV-20 and the tower. NAV-20 gets ring modulation and a metallic comb filter; the tower is band-limited like a radio. Then every line goes through the same 1960s terminal PA: a narrow band, a horn honk and a slap-back echo off the far wall. Each role has its own chime: a ding-dong for the gate, a bing-bong for the captain, three notes up for passport control, one bell for the purser, a jingle for the adverts, a low two-tone for paging, robot blips for NAV-20 and a squelch for the tower.

The script. 36 announcements. Pluto is still a planet. Flights to Andromeda are cancelled, because Andromeda is coming to us. Lost and found is holding one towel. Abductions this evening are scheduled, not strobed.

Can you hear it? Every line goes through Whisper speech-to-text with the music under it, and anything it mishears gets fixed. Two real catches: "HULL twenty" came back as "Hall 20", fixed by writing it as "Hull, twenty,"; and "Spaceways" lost its final s under the music, fixed by slowing the line, ducking the music deeper and holding the duck past the last word. The spelling you hand a speech engine is part of the mix.

The yard. A wired speaker on the Gate 20 computer's headphone jack. Not Bluetooth: on that board, Bluetooth shares a radio with the Wi-Fi, and the Wi-Fi already has a job. A small Python program plays a quiet ten-minute bed (pads, hall air, the saucer idling overhead) with an announcement every one to two minutes from 9 am to 11 pm, then signs off with "Lights down at eleven." Local files only; nothing goes over the network. The film on the Passenger edition has the sound.

Banner: 1,500 WS2812B LEDs (300 x 5, serpentine), an ESP32-C6 board, a 5 V 60 A supply with power injected along the run. Eyes: two 16x16 WS2812B panels, an ESP32-C6 board. Gate 20: a single-board computer, a 15.6-inch USB monitor. Floodlights: four color floods on my home automation.

Tools: a miter saw with a metal blade, an M6 drill-tap bit, a drill guide, a soldering station, a multimeter, heat shrink and more zip ties than I'd like to admit. Software: C++ on the ESP32 core with FastLED, the desktop simulator, Bun and TypeScript for the control server, SwiftUI for the phone app, Blender for the Plan A renders. The code lives in the hangar for now. If enough of you ask, we'll open the doors.

Boarding passes you can hold, for Gate 20's passengers: a circuit board cut like a ticket. Touch both halves and a Darlington pair, running on what leaks through your fingers, switches on the beam. A hundred assembled boards are on order, which makes us either a souvenir shop or a very small airline.

Saucer control from the browser. It's built; it boards with the next flash over the cable.

Cat eyes. After the season, the big light in the belly becomes one of a pair of cat eyes. It already has a pupil and a blink, so the saucer took the news well.

The fleet's newest ship took its maiden flight. Acid rain or shine. It hung over the garage, lit from below, with the banner and the eyes behind it, and every few minutes it abducted nobody in particular.

That night I held Linux up under the saucer and he reached up and touched it.

First contact.

He has since been abducted by the maker bug. Flight record closed. The ship is still up there.