Space Ocean Corp · open models

Space Water Logistics

Three screening calculators for water in space. Move a slider and the answer updates. Every default comes from a public source, and every number matches the Python models in the repository (a test checks it).

Crew water loop

How much water must be shipped for a crewed mission, and how much does recycling save?

Crew people

Mission length days

Urine recovery % (ISS UPA 85%, with brine processor about 98%)

Hygiene water recovery % (ISS collects none)

O2 made from water kg per person-day (0 if O2 is shipped as gas)

Contingency reserve %

water to ship for the mission

with no recycling

launch mass avoided

demand per person-day

makeup per person-day

Loop closure: share of demand met by recycling

Try this: raise urine recovery from 85% to 98% (what the ISS reached with its brine processor) and watch the shipped mass fall.

Rates from NASA Life Support Baseline Values and Assumptions Document, NASA/TP-2015-218570 Rev2, Tables 4-20 and 4-21. Steady-state mass balance; no storage dynamics, brine consumables or EVA water.

Lunar settlement water

How long does local lunar ice last a settlement, and how much water must be imported to keep it supplied?

Population people

Water use tons per person per year (paper's estimate 500)

Recycling efficiency % (ISS best about 98%)

Local ice inventory billion tons

Lander payload tons

until local ice runs out

water lost per year

landers per day to replace it

Try this: set 1,000,000 people at 98% recycling. That loses 10 million tons a year, about 27 landers of 1,000 tons every day.

Reproduces Elvis & McDowell (2026), "No cities on the Moon", Frontiers in Space Technologies 7:1894104 (CC BY). Linear depletion at constant population and use; no propellant drawn from the same ice.

Earth vs lunar water

To deliver 1 kg of water, how much must already be in low Earth orbit (water from Earth), or be mined on the Moon (water from the Moon, propellant made from the same water)?

Engine specific impulse seconds (H2/O2 about 450)

Stage dry mass % of propellant carried (tanks and structure)

Earth numbers leave out the climb from the ground to orbit, which every kilogram in orbit has already paid for: 9.3 to 10 km/s. Lunar numbers count water mined, not the mining equipment.

Destination	From Earth: kg in LEO per kg	From Moon: kg mined per kg

One ideal expendable chemical stage per leg (rocket equation). Delta-v from the Wikipedia "Delta-v budget" Earth-Moon table; returns to LEO assume aerobraking.