36 tanks to Pluto: jump fuel from the rocket equation
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In game, a trip to Pluto would cost the carrier about 36 full tanks of fuel, while a trip to the Moon costs about a tenth of one. Nobody picked those numbers. They fall out of the rocket equation.
Who can jump
Two ships have jump drives today, each with a spool time before it goes:
| Ship | Spool |
|---|---|
| The carrier | 12 s |
| Hawkeye scout | 4 s |
Strikers have no drive. They ride along docked in the carrier. A route over several links is one order: the spool is multiplied by the number of links (a three-link carrier route spools for 36 s), and the route chosen is the one with the least total change in speed.
A jump order doesn’t stop the ship. It keeps its speed, turns toward its destination and goes as soon as the drive is spooled. Nothing holds the spool up, and there is no cool-down. A pulsing ring builds round the hull, and a flash marks where the ship leaves and where it arrives. The flash is what gives a jump away.
Fuel from physics
The first idea was a burn rate per hour. On 25 October 2026 that was replaced by a rule meant to work for every ship: fuel comes from the rocket equation. Only two things are assumptions:
- The ship burns at 1 g the whole way: it speeds up to the halfway point, flips, and brakes. That is a pace a crew can live with.
- The drive is a fusion drive with an exhaust speed of 10,000 km/s. That is in line with the Project Daedalus study, whose two stages were designed for 10,600 and 9,210 km/s[1].
From there it is maths. The change in speed for a trip of distance d is 2√(d·a), the trip time is 2√(d/a), and the fuel burned is the ship’s mass × (1 − e^(−Δv / v_e)). The full explanation is on the rocket equation page.
What it costs, in game
The carrier weighs 100,000 t empty and carries 10,000 m³ of fuel in its tanks, so it starts at about 110,000 t. The Hawkeye weighs 18.4 t and carries a 7 m³ tank.
| Link | Change in speed | Carrier fuel | Hawkeye fuel |
|---|---|---|---|
| Moon far side → Moon east | about 25 km/s | about 280 m³ | about 0.07 m³ |
| Moon east → L1 | about 48 km/s | about 530 m³ | about 0.12 m³ |
| L1 → geostationary 100° E | about 106 km/s | about 1,160 m³ | about 0.27 m³ |
| Geostationary → low orbit over Sumatra | about 37 km/s | about 410 m³ | about 0.09 m³ |
| Low orbit → Bukittinggi, 25 km | about 4 km/s | about 40 m³ | about 0.01 m³ |
A heavier ship burns more for the same trip, so a carrier with a full hold pays about 25 % more per jump.
Why the far trips hurt
Fuel you carry is mass you also have to push, so every extra km/s costs more than the last. For the carrier at 1 g:
| Trip | Change in speed | Fuel | Tanks |
|---|---|---|---|
| The Moon | about 120 km/s | about 1,200 m³ | about 0.12 |
| Mars, at its closest | about 1,500 km/s | about 16,000 m³ | about 1.6 |
| Pluto | about 15,000 km/s | about 360,000 m³ | about 36 |
A flat cost per hour with the same Moon price would have made Pluto only about 11 tanks. The exponent is what makes far trips punishing. Earth to the Moon at 1 g takes about 3.5 hours.
Tanks, containers and the way back
Range is all the fuel aboard: the tanks plus fuel in containers in the hold. A ship tops its tanks up from its own hold on the way. A tank holds fuel in the least space; containers take about a third more room, but that room is cargo space again once the fuel is burned.
Before every jump the game checks whether the fuel left would bring the ship back the same way, remembering that it will be lighter by what it burned. If not, the jump is marked “can’t return”.
Hot drops between height bands and tactical burns cost no fuel. Nobody should waste time saving slivers.
Related
- Why fuel is mass: the rocket equation, explained
- 384,400 km apart: the Earth and the Moon at true scale
- 350 m long, 80,000 hull: the carrier
Sources
- Project Daedalus, Wikipedia.
producing exhaust velocities of 10,600 km/s and 9,210 km/s respectively.