The aim of this article is to provide a review of the architecture and business for the first commercial propellant depots to be deployed in space within a decade. The capability to refuel spacecraft in low Earth orbit (LEO) underpins a paradigm shift that considerably decreases cost and increases the mass of spacecraft hardware possible per launch because of the reduction of onboard propellant requirements. This same refueling capability also enables repeated long-duration high-thrust missions for commerce, exploration, and security to be carried out at superior price-performance, resulting from extensive reuse of in-space vehicles and systems. Shackleton Energy Company is establishing initial propellant depots in LEO using propellants launched from Earth to commence sales and deliveries within 5 years from program start, followed by deliveries of water-derived propellants from the lunar poles within an additional 5 years. By sourcing the propellant from the Moon's lower energy gravity well, significant reductions in operating costs are possible, with additional infrastructure costs amortized over multiple sales cycles. The most readily accessible and operationally robust source of cryogenic liquid oxygen and liquid hydrogen is from the craters situated at the poles of the Moon, in the original form of water ice.

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