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Methalox from Titan

The ascent vehicle lifts off at 109 tonnes on 14 tonnes of methane from the sea and 50 tonnes of oxygen from the ice.

See it in the tour: chapter how it survives, shot 7.5.

Two tanks, two sources

The ascent vehicle burns methane and oxygen. Kraken Shore makes both.

The methane comes from the sea. Kraken Mare is a methane-dominated liquid physics, and barges carry it to the plant design. The oxygen comes from water ice. Miners melt it, electrolysis splits it into hydrogen and oxygen, and the town's two small fission reactors supply the power design. The plant has made propellant since 2066, the year the first robotic ascent vehicle reached orbit fiction.

Oxygen is most of the load. One launch takes 14.0 t of methane (35 m³) and 50.3 t of oxygen (46 m³) design. Making the oxygen uses about 57 t of ice physics. The reaction is

CH₄ + 2 O₂ → CO₂ + 2 H₂O

and it balances at 4.0 kg of oxygen per kilogram of methane. The vehicle runs at 3.6 physics. The extra methane keeps the exhaust molecules light, and light molecules leave faster.

The burn

The injector sprays both liquids into a flame physics. A thin flame front turns cold liquid into hot gas, and short-lived radicals, OH and CH, glow blue-violet there physics. Stronger bonds form than break, and the difference is about 800 kJ per mole of methane physics.

Hot gas leaves the nozzle at about 3.4 km/s. That is a specific impulse of 345 s, between the 330 s of sea level and the 360 to 380 s of vacuum physics. As the air thins on the climb, the plume widens and fades to a faint blue-violet above the haze physics.

Storage at 94 K

The tanks stand in air at 94 K. At 94 K and 1.5 bar, liquid methane is stable at ambient temperature and liquid oxygen sits near its boiling point physics. Storage needs far less insulation than on Earth, and no refrigeration for the methane. The vehicle is 26 m long and 4.5 m across design.

Delta-v to orbit

Titan's escape speed is 2.64 km/s, less than a quarter of Earth's physics. A 1,500 km parking orbit, above the bulk of the haze, costs 2.25 km/s ideal physics. Drag and gravity losses add 0.5 km/s, and the design budget of 3 km/s keeps 0.25 km/s of margin design.

At 345 s, 3 km/s takes a mass ratio of 2.427: 109.2 t at liftoff and 45 t of vehicle and payload at the end design. Liftoff thrust is 221 kN, a thrust-to-weight of 1.5 design.

One sea, three customers

The same methane fills the Gateway shuttle, 206.7 t per load (nuclear-thermal). Oxygen goes to the ascent vehicles and to the air indoors. The hydrogen left over from electrolysis becomes reaction mass for the fusion transports design. Saturn exports propellant to the ships that serve it fiction.

Key numbers

Quantity	Value	Basis
Reaction	CH₄ + 2 O₂ → CO₂ + 2 H₂O	physics
Energy per mole of methane	about 800 kJ	physics
Specific impulse (average used)	345 s	physics
Oxygen to methane	3.6	physics
Methane / oxygen per launch	14.0 t / 50.3 t	design
Ideal delta-v to 1,500 km orbit	2.25 km/s	physics
Design delta-v	3 km/s	design
Liftoff mass / thrust	109.2 t / 221 kN	design
Titan escape speed	2.64 km/s	physics