Frontier authentication station, grown from a relay

The Cairn

A road-marker that people moved into. Four pressure cans and a man selling filter tape became a city of forty thousand at the only authenticated door into a reach, and it is still built around the relay it grew on — plated to about the height of two men and bare above that, where nobody has ever got round to it.

Operator: The Cairn Compact — nine founding signatory parties
Series: The Cairn
Drawn as: As at 2330, the year of the census — twenty-three sealable sectors, 37,400 people in 41,000 places, and Ring Eleven fitted, lit and empty beside them.

Sheet 1 Ring plan — looking down, throat side to the top 13 rings · 26 sealable sectors

Sheet 2 Section — looking in, showing the vertical stack Core height 96 m

Sheet 3 Sector schedule — capacity against occupancy 37,400 in 43,400 places

C The core district 3,560 / 3,790

C-N Core-North — the relay heart core pressure doors published S13 B3 SECTOR-ROSTER; B1–B4 passim
Certified 1,960; 1,840 in 2330. The civic floor: market pitches to the wall on three sides and barrows down the fourth, the freight lane painted on the deck in yellow and repainted by the traders out of their own pockets, the drift-board by the south stair posting the Vekhol day-market's twenty-five-hour clock, the shrine with its relay-era tokens, the claims desk, the exchange, the node room that seats nine at a pinch and whose shutter does not shut. The oldest frontages have the south stair and the light.
C-S Core-South — administration core pressure doors published S13 B3 SECTOR-ROSTER; B2 ch01, B3 ch20
Certified 1,830; 1,720 in 2330. Two levels above the heart the noise falls off to nothing, which is what the old core paid for and got. The Assembly hall is a bonded store off the administration stair with the racking scars still up both long walls — and it is not a boundary: the seal is at the core pressure doors up the stair, so if this sector goes, everybody in that room is in it.
C-2 Ring Two core pressure doors fixed author ruling 2026-08-01
AUTHOR RULING. Ring Two is inhabited and leased in published prose — a fence-line dispute between two households over a laundry, a stripe painted down the middle of a corridor, a woman with a child under a year — but it holds no seat and appears on no roster line. The ruling: Rings One and Two are the original volumes grown against the relay core, not independently sealable, and therefore inside the core's seal. That keeps the published count of twenty-three exact and keeps the prose true. Ring One is never named in any book.

D12 Deck Twelve 780 / 890

12-A Deck Twelve — feedstock and cultured lines plant boundary published S13 B3 SECTOR-ROSTER; B1 ch02, ch21
The only numbered deck in the franchise, and it is used as a sector name rather than as a position in a sequence. Five six-hundred-litre vessels drawn in rotation, each killable alone by one person at one switch — because two hundred cubic metres of bay water cannot be cooked by anything on the Cairn, so the plant is small and there are five of them.
12-S The Sethlan sector plant boundary published S13 B1 ch02, ch08; B2 ch26
Through a stepped lock, and inside three metres the temperature and the light change: dim, wet-warm, the air heavy enough to sit on the skin, a degree and a half warmer than any human keeps a room. Four hundred and six people, two sittings a day, four low tables end to end down the commons and the cord frames racked along the far wall. Something grows on the damp of the outboard walls that the Sethlan strip and braid, and the cord it makes does not rot in a wet void — so the reclamation crews buy it hand to hand, off the books. The entry arch shows low amber off the east curve, dimmer than every door beside it.

V The maintenance voids 460 / 490

V-1 The voids — sections eight through twenty service isolation published S13 B3 SECTOR-ROSTER; B1 ch11, ch15, ch16; B4 ch07
DRAWN AS A BAND, BUT THEY RUN UNDER EVERYTHING. The voids are not a ring at one radius; they are the service level beneath every ring walk, from the core out, and this sheet shows a representative band because a plan cannot draw a floor that is under all the other floors. Eleven rungs down from the heart into cold. On your heels for the first twenty metres, then two hundred metres of crawl under a metre high; nine hundred millimetres under the spine frames. Twelve metres past the pinch the void forks — one leg inboard toward Twelve's service side, one outboard along the trunk toward the trade-side holds. The reclamation crews write on the plating in wax pencil, and at the third frame somebody has drawn a dog. Four hundred and sixty people, one member, and one road out.

R3 Ring Three 1,050 / 1,180

3 Ring Three ring boundary published S13 B3 SECTOR-ROSTER; B2 ch04
The oldest let. Lease forty-one is here — a good door on a dry row, and the whole row re-papered inside a season when the block was bought. At the quiet hour Ring Three sounds of its own ventilation and nothing else.

R4 Ring Four 1,350 / 1,460

4 Ring Four ring boundary published S13 B3 SECTOR-ROSTER; B1 ch08, ch21
Nine blocs, nine boundaries, eleven hundred people on the far end of the same pipe. The reserve bunker is nine hours and it starts the minute you open it. On the spine wall at the boundary hangs a laminated board marked up in wet pencil going back a year, and along the bottom in the same hand: REFUGE CAPACITY 480. Ring Four was three frames and a tarpaulin once.

R5 Ring Five built 2319 3,990 / 4,200

5-A Five-A ring boundary published S13 B3 SECTOR-ROSTER
Certified 2,120; 2,010.
5-B Five-B bloc doors published S13 B3 SECTOR-ROSTER
Certified 2,080; 1,980.

R6 Ring Six built 2319 5,550 / 5,780

6-A Six-A ring boundary published S13 B3 SECTOR-ROSTER
Certified 1,980; 1,900.
6-B Six-B — the bypass sector bloc doors published S13 B3 SECTOR-ROSTER; B2, B4 ch01
Certified 1,940; 1,860. The emergency cross-feed of 2322 was laid along a residential corridor here because there was no time to go through the trunk, and the corridor never got its width back. Twelve years on it is different plating, four courses of it, and a narrow part that takes people single file. Nobody explains the name any more.
6-C Six-C — the plant face plant boundary published S13 B3 SECTOR-ROSTER; B4 ch03, ch13
Certified 1,860; 1,790. The industrial face, and where the trunk was cut. The only gang on the station that can plate to a wound rating works here, which is why every other job on the Cairn queues behind this arc.

R7 Ring Seven built 2320 5,040 / 5,340

7-A Seven-A ring boundary published S13 B3 SECTOR-ROSTER; B4 ch13
Certified 1,820; 1,730. Its landing is thirty paces by about twelve, with the sector office at the ramp end and the ward store at the other — and after the twenty-eighth of 2334 there are households living the length of it and forty paces into the walk beyond.
7-B Seven-B bloc doors published S13 B3 SECTOR-ROSTER; B4 ch07, ch10
Certified 1,780; 1,670. Its inboard walk is wider than Ring Six's and has never been narrowed, and it runs flat and unbroken from the landing to the turn at the plant face. Four bloc doors on the line, and they are not all handed the same way — which is the only reason anyone came off this walk alive.
7-C Seven-C plant boundary published S13 B3 SECTOR-ROSTER; B4 ch10, ch29
Certified 1,740; 1,640. Lost in 2334. Its returns ran through the plant face, and the face had been carrying above its rating for three days when it stopped. The roll at the twenty-eighth was 1,680; the sheet closed on the forty-fourth at twenty-three. There is no volume behind that door that a person is going to sleep in again.

R8 Ring Eight built 2320 3,800 / 4,040

8-A Eight-A ring boundary published S13 B3 SECTOR-ROSTER
Certified 2,040; 1,920.
8-B Eight-B bloc doors published S13 B3 SECTOR-ROSTER
Certified 2,000; 1,880.

R9 Ring Nine built 2325 4,130 / 4,800

9-A Nine-A ring boundary published S13 B3 SECTOR-ROSTER; B3 ch23
Certified 2,420; 2,080 — the largest constituency on the station, and 4.52 of it to one of the voids. Built 2325, and the first ring on the Cairn built two-path from the drawing, because of what happened in Ring Six three years earlier.
9-B Nine-B bloc doors published S13 B3 SECTOR-ROSTER
Certified 2,380; 2,050. Its second gallery takes displaced households after 2334, with one wash-house between them.

R10 Ring Ten built 2328 3,930 / 4,920

10-A Ten-A ring boundary published S13 B3 SECTOR-ROSTER
Certified 2,480; 1,980 — the newest occupied ring, and the only one with real slack in it.
10-B Ten-B bloc doors published S13 B3 SECTOR-ROSTER
Certified 2,440; 1,950. Stood empty a season after it was finished.

R11 Ring Eleven built 2333 0 / 2,400

11 Ring Eleven — fitted, lit, empty ring boundary published S13 B4 ch03, ch13, ch29
NOT ONE OF THE TWENTY-THREE. The deck plate along the inboard walk has no wear on it anywhere in its length; the walk light is up the whole way round; and the air comes off the returns at the temperature it would come off them with two thousand four hundred people in there breathing it, because a sector held below that loses its seals and its growth hall inside a season and then has to be paid for twice. Door numbers cut into the frame rather than stuck on, because a stuck number comes off and a cut number is there when the lights are down. Every handle carries an orange fitter's tag with a date and a pair of initials, and the dates run back three quarters. Every notice frame is glass and a clip and nothing behind the glass. It is shut because its second path has not been walked.

DK The dock districts 3,760 / 4,110

TH Throat-side throat isolation published S13 B3 SECTOR-ROSTER; B1 ch07, B4 ch04, ch08
Certified 870; 710 — the emptiest sector on the station and the one everything else depends on. The landing has a ramp down to the works passage and a ramp up to the trade concourse and one turn between them. It runs colder than the trade side and always has, because nothing on this side is heated past what the work wants. The Warden's working room is one deck under the ranging gallery and is the only compartment on the station where nothing is stacked on anything else.
TU Trade-Upper dock boundary published S13 B3 SECTOR-ROSTER
Certified 1,690; 1,590. The post, the vault, the registry counter and the Bench's outer room across the landing from it.
TL Trade-Lower dock boundary published S13 B3 SECTOR-ROSTER; B2 ch02
Certified 1,550; 1,460. The aprons and the dock rows. The berth board runs one to twenty-two down its left edge, white paint on black steel, bolted to the chalk hut at the head of the aprons — fourteen under the Concession's first call, eight in open order.

Seal class — what shuts around this volume

Ring boundary
Bloc doors
Plant boundary
Core pressure doors
Dock boundary
Throat isolation
Service isolation

Grade of every figure on these sheets

published Stated in the books. If a drawing disagrees, the drawing is wrong.
derived Arithmetic on published facts; the working is given.
fixed Canon was silent here and the drawing decided.

Systems

The environmental trunks

published

Twenty-two runs across four rings, on one certificate

One certificate, raised 2320, referencing the ring set's master design by its drawing number and certifying the runs as constructed two-path throughout. It named no run, no frame, no length, no diameter and no gallery. Nineteen of the twenty-two went in single-path underneath it — the form offered the substitution, nine houses took it separately for a saving on each of their own accounts, and the master design was never amended, so every gallery plate in four rings still reads two-path and every plate is correct against the drawing it was printed from.

Runs, Rings Five to Eight22
Built single-path19 B2 canon. Spoken in B4 ch13:103 as 'nineteen of twenty-two off four separate people this fortnight'; the coined form 'a corridor in 2322' was cut at the B4 dialogue pass and is no longer live prose
Certificates1, dated 2320
Re-pathing programme90 days, four runs openable at once

S13 B2 ch21, ch22, ch23, ch27

Trunk Six

published

The shared polishing loop

Takes what three sectors put down a drain, feeds it through the standard cultures, and hands it back clean and boring. The Sethlan draw first on the loop; Ring Four's eleven hundred draw second. There is no third pipe.

Return pH7.4, held 209 days
Turnoverevery 22 minutes
Loop volume140 m³ at temperature
Culture failurestandard cultures quit below pH 6.9 it is in every commissioning file on the station

S13 B1 ch08, ch15, ch17

Bloc doors

published

A rack, a pinion, a crank and one warden

The leaf sits back in a pocket with a fire notice on the frame and a lamp bracket over it. The gear is a plain plate, a cranked handle behind it and a lock through the crank — grease goes on the pinion, never the rack, because the rack is meant to be dry. It opens from the gear's face only; it shuts from either, on a trip on each face and one at the turn. Handedness varies door to door, and the sector office's board draws all four the same way round and has done since the doors went in. There is no remote actuation: the board is a picture of the doors, and it is for the office to look at.

Full cycle, hand-crankedunder three minutes two minutes and a bit, with the seat checked
Jacked from the wrong faceone-way a bar in the square socket at knee height; when the mark cut in the bar comes level with the frame the leaf is clear. After that you have not got a door — you have a leaf lying off its seat in a pocket it does not fit, and the boundary is gone.
Reseating a jacked leafa hold on both faces, a gang for a run of shifts, and a name on the test
A ring boundaryan afternoon a ring boundary is not a door

S13 B4 ch07, ch10

The emergency isolation set

published

Four bays in a row along the ring spine

A sealed hold, a kill train, an actuated valve set and its own stack — cut in during the ring build, certified, filled with clean water, and never once used for anything. Three of the four bays' atmosphere skids share a condenser, which somebody did on a quiet shift in the second year and never drew. Bay Three's washdown header has carried a blank flange since it was fitted, because the valve went into a consignment for the fourth ring and never came back.

Bays4
Gross sealed hold, per bay180 m³ the contingency entry reads as a per-bay unit description — a sealed hold, a kill train, an actuated valve set, its own stack: one bay's equipment, listed once
Net working volume, per bay140 m³ gross minus the kill train, valve set and stack — and identically the Trunk Six loop volume, because the recourse was sized to receive the loop. That is engineering, not coincidence.
Set, gross≈720 m³ across the four
Bay One as charged, 2318≈200 m³ the 140 off the loop plus the flush water — the trunk was flushed and re-seeded INTO the bay holding it

S13 B1 ch12, ch21

Load shedding

published

Isolate at nine boundaries; local reserve nine hours; recourse

The contingency schedule reads: loss of primary polishing — isolate at bloc boundaries (nine); local reserve, nine hours; recourse, transfer to the emergency isolation set at the ring spine, by standing arrangement with station environmental. When the set is already committed, the recourse line is a sentence that is not true. Under shed load the spine circuits come down, which puts the powered doors between the seven-side blocs and the Ring Six commercial deck to manual, and corridor lighting drops to the emergency circuits — which on the new rings means a strip of blue at ankle height and nothing else.

Ring Four local reserve9 hours for 1,100 people and it starts the minute you open it
Ring Four refuge capacity480
Domestic respiratory cartridge40 minutes, 20 realistically if it has been in a cupboard

S13 B1 ch12, ch21; B2 ch26

The RING RESERVE plate

published

Stamped at the build; the working figure on a slip

Bolted to the bulkhead over the tap at eye height, where the corridor meets the junction. RING RESERVE stamped into the metal at the build, and the build's figure stamped with it: NINE HOURS. Below the stamp, in the working slot, a printed slip — white figures on a grey slide. It read FOUR, then THREE, then under two. The queue stands under it the way it stands under the light brackets, and the whole corridor goes past it all day without slowing.

Stamped at the buildNINE HOURS
Maximum the plant may postTHREE
Actual, at the worstunder TWO

S13 B2 ch04, ch12, ch19

The anchor-chain shore plant

published

Twelve metres of walk, four doors, four chains

Four doors off the outboard side, one to a chain, a desk at the far end with the round sheet clipped to it and the pin store opposite. In each bay a cradle, a take-up, a brake, a set of load pins, two tell-tales, and a port in the outboard face with nothing to look at through it. Nobody looks through it. A stair at one end comes down off the boundary dock through a code door every hand on the throat side knows; the other end gives onto the works passage, which is how the trolleys come in. Three rounds a day, and between rounds nobody stands the plant, because there is nothing in there for a person to stand at.

The unattended gap1 hour 30 between the second round and the third and there has been nobody in the plant in it since the plant went in
Bay threeon local operation since the winter the key hangs on the frame and the panel at the stair head shows three shut whatever three actually is. It is written on the round sheet in three places.
The attack4 minutes, first tell-tale to last
Aftertwo chains cut, one damaged, one serviceable
Diagnosticdressing bright on one face and dull on the other which is what it does when the pin is going over

S13 B4 ch04, ch08, ch11, ch16

The corridor budget

published

Two hundred and forty hours on one chain

Two hundred and forty hours are scheduled on chain four against this corridor. A passage window is twelve of those hours. That is twenty windows. A hull carries a hundred and twenty places. A window takes the chain from its first hour to its last with nothing across it — and every hour that goes on four for anything else comes out of the two hundred and forty. Twelve of them is a window that is not flown, and a window that is not flown is not made up afterwards.

Scheduled240 hours
A window12 hours
A hull120 places
Flown17 windows, 2,040 names
Standing at the close6 hours ruled off with the reference against the rule, and the hours board taken off its nail and put face down

S13 B4 ch16, ch17, ch24, ch28

Counter height

published

One figure, station-wide

Every counter on the Cairn is cut at human waist height, and all of them are cut to the same figure. The accommodation for anybody built otherwise is a stool, one per post, and nothing else — which Sesk has stooped past for sixteen years. Deck Twelve is the single exception, and it is an exception because the whole sector is built to Sethlan preference and human standard is the odd one out.

S13 B2 ch13; B4 ch05, ch15

What was checked

The books state distances aboard this ship. The drawing has to produce the same ones or it is wrong — so it is made to, and the working is shown. These run again on every build; a compartment moved by a metre fails them.

“Twenty-three sectors, 41,000 certified places, 37,400 people, 91.2 per cent” S13 B3 ch02, ch16

Summing certified capacity across every sector drawn on this sheet: 3,790 + 890 + 490 + 1,180 + 1,460 + 4,200 + 5,780 + 5,340 + 4,040 + 4,800 + 4,920 + 4,110 = 41,000. Summing population: 3,560 + 780 + 460 + 1,050 + 1,350 + 3,990 + 5,550 + 5,040 + 3,800 + 4,130 + 3,930 + 3,760 = 37,400. Both reconcile exactly to the published figures, and 37,400 / 41,000 = 91.2 per cent.
“Nine-A is more than four and a half of mine to one of hers” S13 B3 ch23

Nine-A 2,080 against the voids 460 = 4.52 : 1. Both figures are on this sheet as drawn.
“Ninety-seven point three across the twenty-three — 39,900 people in 41,000 places” S13 B4 ch03

39,900 / 41,000 = 97.3 per cent. The denominator is the twenty-three sectors and excludes Ring Eleven, which is drawn on this sheet outside the roster for exactly that reason.
“Ring Eleven holds two thousand four hundred fitted places” S13 B4 ch03, ch29

Drawn at 2,400 capacity and 0 population, outside the twenty-three. Built capacity in 2334 is therefore 43,400, not 41,000 — and the published 97.3 per cent quietly excludes 2,400 empty rooms two walks and a ramp from a landing where people are sleeping on the deck. No character ever says this out loud. Against the true built figure the station is at 91.9 per cent.
“Every published isolation figure stands — 180, 140 and 200 cubic metres are three different measurements, not one measurement three ways” S13 B1 ch05, ch08, ch12, ch17, ch21

180 m³ is one bay's gross certified hold: the schedule entry lists a single bay's equipment — a sealed hold, A kill train, AN actuated valve set, ITS own stack. Net of that plant, a bay works out at 140 m³ — which is also Trunk Six's loop volume, because the recourse was sized to receive the loop. That is why Bay Two, swept and hosed empty, reads as '140 cubic metres of nothing at all', and why Bay One takes the loop's 140 exactly. Bay One then holds about 200 because ch17 says the trunk was flushed and re-seeded WHILE the bay held it — the flush water joins the charge. And 'exactly one sealed volume big enough' is availability at that hour, not geometry: Bay Two was chilled under lease for the cargo custody, Bay Three's washdown header has carried a blank flange since it was fitted (a bay that cannot wash down cannot take contaminated water), and Bay Four held the clean-side bench. Ch12's 'filled with clean water' is the certified standing state; a bay committed elsewhere is drained first — which is the erosion of the recourse, and is the book's own point.
“The frame edge is at knee height in ch11 and at hip height in ch16” S13 B1 ch11, ch16

Two different frames on the same run. Ch11 names THE FOURTH SPINE FRAME — knee height, scraped bright along forty centimetres, the wool tuft on the bolt head. Ch16 is A spine frame thirty metres in — hip height, bare of lagging. The run crosses several ('at every pinch a case came off the wheels'), and a void whose clearance goes from on-your-heels to under a metre puts the same class of edge at different heights along its length. Both statements stand as written.
“Nine void access points against Milek's dozen” S13 B1 ch13; B4 ch12

Resolved on the page. Nine is the sweep order's count for sections eight through twenty, off a drawing. A dozen is Milek's count of ways down off the relay-heart floor alone, in 2334 — and she says herself the drawing is from before the vault door went in. The figures measure different things at different dates, and the stale drawing is not an error in canon, it is canon: B4 presents it as exactly that.
“Lifts exist in Book One and no passenger lift appears in Book Four” S13 B1 ch08, ch17, ch21; B2 ch26; B4 passim

Absence of mention is not absence. Book One establishes a lift lobby, a two-level ride, a goods lift on the ring build, and a ring-spine lift out of service since the build. Book Two puts lifts on rotation under shed load. Book Four is set almost entirely under a declared emergency with the station shedding — the hours when a lift is the thing you do not plan on. Kade counting stairs is her knees, not the fabric. Lifts are drawn as they are written: few, mostly goods, unreliable.

Service history

Before the Compact
Four pressure cans and a man selling filter tape out of a crate at criminal prices. Span control at the mouth, made permanent as the reach's standing authentication anchor and logged Cairn Relay.
~2318, Book One
Eight thousand permanent, ten thousand through ration issue in a day. Eleven sectors with signature rights. Ring Four is three frames and a tarpaulin in living memory.
2319–2320
The Concession build. Rings Five through Eight let on forty-year terms to nine houses. One redundancy certificate covers twenty-two runs across four rings.
2322, Book Two
Twenty-four thousand in quarters, thirteen thousand of them in rings that had been lines on a drawing. The Six line fails. Eleven dead. The bypass is laid along a residential corridor on Day 51 and the corridor never gets its width back.
2325 and 2328
Ring Nine — the first built two-path from the drawing. Then Ring Ten, which stands empty a season.
2330, Book Three
Thirty-seven thousand four hundred in forty-one thousand places across twenty-three sectors. The Assembly is elected; the constituencies are the volumes that seal.
2333
Ring Eleven finished, fitted and held at temperature. It does not open.
2334, Book Four
Charges on two anchor-chain shores. Seven-C's plant face carries above its rating for three days and stops; the sector is lost and sealed, 1,657 people displaced onto landings. The relay heart's ledger room is cut at the hinge side and burned; the route ledger is reconstructed by hand from counter copies, and it will not be the same book. Thirty-nine thousand nine hundred in forty-one thousand places, at ninety-seven point three.

What this drawing does not decide

A blueprint that answered everything would be inventing. These are the things canon has not fixed and this sheet deliberately leaves for a book to claim.

Ring One is never named in any of the four books. Ring Two is inhabited in prose and holds no seat; the ruling that both sit inside the core's seal is the author's, made for this drawing, and is not on any page.
Every radius, ring width, arc and deck height on these sheets is the drawing's. Canon gives no diameter, no circumference, no deck count and no core height.
The core's plan geometry. It has four faces and is plated, but is never called round, square or polygonal. 'West curve' and 'east curve' against 'south frame' and 'south brace' suggest a curved floor around a squarer core, and that is as far as the prose goes.
Ring vertical extent. Rings plainly have several levels — a well that carries the smell of onions two levels up, second galleries, landings — but no ring's level count is stated anywhere.
Whether four bloc doors to a line is standard, or particular to Seven-B.
The sector office's bloc-door board is canonically WRONG — it draws all four doors the same way round when their handedness differs. This sheet draws the truth, not the board. Any future drawing must do the same.
The branch plate stencilled six-C sits on the branch the schematic calls six-D, because the fitters cut them in the order the pallets came off the lift. It has never been corrected and is not corrected here.
Book Five is in production. Anything it fixes supersedes anything this sheet decided; the deck field, the ring radii and the Ring One/Two ruling are the first places it could land.

Compiled from

S13 B1 The First Claim — 26 chapters (frozen)
S13 B2 Appetite — 28 chapters (built)
S13 B3 Memory — 29 chapters (built)
S13 B4 Anchor — 31 chapters (complete and gated; author editorial to come)
series-13-the-cairn/book-3/SECTOR-ROSTER.md v2.1
series-13-the-cairn/book-4/B4-SCAFFOLD.md §15 number register
universe-state/locations/stations/the-cairn.md