Source: SpaceX
SpaceX Starship Overview
The SpaceX Starship is a next-generation spacecraft designed to enable the exploration and colonization of distant planets. It represents a pivotal evolution in spacecraft technology, leveraging the power of full reusability to significantly reduce the costs of space travel. This is achieved through an ambitious design that includes a stainless-steel structure, efficient Raptor engines, and the ability to land back on Earth using retro-propulsion.
SpaceX's Starship consists of two stages: the Starship spacecraft itself and the Super Heavy booster. The Starship spacecraft, which is the upper stage, is designed to accommodate up to 100 people and can carry more than 100 metric tons of cargo. The Super Heavy booster, the lower stage, is responsible for escaping Earth's gravitational pull. After its ascent, the booster returns to Earth, landing vertically for refurbishment and reuse.
Several different variants of the Starship spacecraft are forecast to be built as illustrated below.
This article is focused on the tanker and depot variants.
The Concept of a Space Refueling Depot
The idea is to have a permanent or semi-permanent station in orbit that stores large amounts of fuel, where other vehicles can dock to refuel. This would enable longer journeys in space, as a spacecraft could launch with less fuel, refill in orbit, and then continue its mission.
This strategy offers potential solutions to some of the most pressing challenges in space exploration, including the issue of weight constraints during launch and the high costs associated with sending larger quantities of propellant into space.
Starship Depot
The Starship depot refers to a variant of SpaceX's Starship that is optimized for fuel storage. This Starship depot would be replenished by Starship tankers. The depot is not intended to return to Earth.
The Starship depot would act as a refueling station in space, allowing multiple spacecraft to dock, refuel, and continue on their respective missions. It would serve as a centralized hub that could support a range of activities, from lunar missions to interplanetary travel and perhaps even deep-space exploration.
Starship Tanker
The Starship tanker is a specialized variant of SpaceX's Starship spacecraft. The primary function of this tanker is to carry large volumes of propellant, liquid methane and liquid oxygen, to low Earth orbit (LEO) for the purpose of refueling the Starship depot. The design of the Starship tanker is very similar to the regular Starship, but it is optimized for carrying and transferring fuel.
The Starship tanker would launch from Earth, similar to any other spacecraft, but its sole mission would be to rendezvous with the Starship depot spacecraft in orbit to transfer fuel. The tanker would then return and land, to be reused for future refueling missions.
Artemis III Mission
The Artemis III Mission is planned to use the tanker and the depot variants.
As illustrated in the mission profile below, the depot will be launched to LEO first, followed by four launches of the tanker variant to fill the depot. Subsequently, the Human Landing System (HLS) variant will refuel from the depot before continuing onto the moon.
Challenges and Considerations
Although the concept of in-orbit refueling and the use of Starship as a refueling depot is promising, it's also accompanied by numerous challenges. First, the technology to facilitate in-orbit refueling is still under development and has yet to be proven. It involves complex maneuvers and the ability to safely transfer fuel in the harsh conditions of space, where factors like zero gravity can complicate the process.
Second, there are also logistical considerations. The successful implementation of a space refueling depot requires a significant number of launches to transport and store the fuel in space. This not only increases costs but also raises questions about the availability of launch sites and the potential environmental impact.
Summary
The possibility of SpaceX's Starship serving as a space refueling depot offers a glimpse into the future of space travel. By leveraging in-orbit refueling, SpaceX could potentially reduce the costs and logistical hurdles associated with long-distance space exploration.