Hard science fiction · Matthew Mills
Reusable steel ships, orbital fuel depots, and working crews who mine the asteroids for a living. A near future that works.
Book One · Out now
Jack and Gus Calloway left Earth to mine asteroids, not to rewrite history.
Two brothers, one ship, and a lifetime of family legacy have brought them to Vesper-7, a carbonaceous rock rich enough to make them wealthy. Their operation is routine until an anomaly buried in the southern hemisphere forces them to confront something no survey drone was ever meant to find.
What they uncover is older than humanity, sealed with intention, and impossible to ignore. As the artifact begins to reveal its purpose, the Calloway brothers must decide what to do with the most valuable discovery in human history — and whether some knowledge should remain in the dark.
In the deep, the past has weight. And some foundations were never meant to be moved.
Choose a format · Amazon
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“The ship was a Starship because everything out here was a Starship; every truck in a boomtown had once been the same truck.”
“The world had changed because the machines had finally gotten good and humanity, against the predictions of half its philosophers, hadn’t been replaced by them. It had been amplified.”
“Nothing came up from Earth to carry the metal back. The rock paid its own freight, in ships built from the rock itself.”
Book trailer · 1:04
The world of the Firmament Line
No warp drives and no collapse. The Firmament Line runs on hardware you can trace from today’s launch pads: methane rockets, propellant depots, fission power, and metal printed from the rock itself. The constraints are real, and they drive the story.
Starship V4 · bought used · 11 flights logged
An early-production Starship Version 4, bought at a fleet auction with patched plating and a scar on the docking collar. A fourteen-month refit stripped out the passenger fittings, flaps, and tiled heat shield, and added drone cradles, an assay lab, a metal printer, and recyclers for a year without resupply.
Methane / LOX · 6 vacuum Raptors
Six vacuum Raptors sit on the aft ring, fed from an orbital depot. On the departure burn, the ship’s intelligence, HARLAN, shuts them down in pairs to hold acceleration near two g. With no tiles, the hull is laced with pores that can sweat methane through the steel to carry heat away.
Low Earth orbit · propellant depot
Every run starts at the depot: a ring of Starship hulls docked nose to tail, turning just fast enough to settle propellant, trailing an acre of solar array. From there it is 62 days out, eight months on site, and 51 days home. A year, door to door.
2031 VK-7 · ~900 m · carbonaceous
A near-Earth asteroid darker than old asphalt, cratered on its craters, with boulders perched loosely on the surface. It holds water locked in clay, a lens of nickel-iron along its equator, and platinum-group metals worth the trip.
40 drones · ~2 km² · tethered
Forty drones anchor in a spiral across the regolith, linked by tethers, with the Argo moored a few hundred meters off the rock. Nothing walks on Vesper-7; people and machines move hand over hand on lines. A sealed micro-reactor supplies the heat.
Water → hydrolox · nickel-iron → hardware
Reactor heat bakes water out of clay, and electrolysis splits it into hydrogen and oxygen. A school-bus-sized printer turns asteroid nickel-iron into tanks, trusses, and engine bells. A vacuum still boils off the iron and nickel and leaves platinum, rhodium, and iridium behind.
Pump-free hydrolox kick stages, printed on site, throw 100-tonne ore canisters onto a fourteen-month coast home to waiting catcher tugs.“Solar had built the depots. Fission ran the mines.”
Book Two · Coming next
The second book of the Firmament Line is in proof now. A release date will be announced here.
About the author
Matthew Mills is a Colorado author who writes hard science fiction. The Firmament Line is his series about a near future that works, where machines amplify the people who build with them and working crews push out into the dark to keep the future fed.
The Cornerstone, Book One, was published in July 2026. Book Two, The Candle, is in proof.
[One or two sentences about you in your own words: background, what you do when you’re not writing, where in Colorado you live, and what pulled you toward hard SF.]