Stanford torus

The Stanford torus is a proposed NASA design for a space settlement capable of housing 10,000 permanent residents. It is a type of rotating wheel space station, consisting of a ring with a diameter of about, its rotation providing about 1.0 g of artificial gravity.

History of the concept

The Stanford torus was proposed during the 1975 NASA Summer Study, conducted at Stanford University, with the purpose of exploring and speculating on designs for future space colonies, with the conclusions and the detailed proposal being published in 1977 in Space Settlements: A Design Study book, by Richard D. Johnson and Charles H. Holbrow. "Stanford torus" refers only to this particular version of the design, as the concept of a ring-shaped rotating space station was previously proposed by Konstantin Tsiolkovsky, Herman Potočnik and Wernher von Braun, among others.

Design

The Stanford torus consists of a torus, or doughnut-shaped ring, that is in diameter and rotates once per minute to provide between 0.9 g and 1.0 g of artificial gravity on the inside of the outer ring via centrifugal force.
Sunlight is provided to the interior of the torus by a system of mirrors, including a large non-rotating primary solar mirror.
The ring is connected to a hub via a number of "spokes", which serve as conduits for people and materials travelling to and from the hub. Since the hub is at the rotational axis of the station, it experiences the least artificial gravity and is the easiest location for spacecraft to dock. Zero-gravity industry is performed in a non-rotating module attached to the hub's axis.
The interior space of the torus itself is used as living space, and is large enough that a "natural" environment can be simulated; the torus appears similar to a long, narrow, straight glacial valley whose ends curve upward and eventually meet overhead to form a complete circle. The population density is similar to a dense suburb, with part of the ring dedicated to agriculture and part to housing.
The Stanford Torus design was not conceived for a single, isolated space settlement, but as part of a system for the colonization of space. Part of the people living in the colony would work in the construction of satellite solar power stations and new colonies, so that the habitat would be capable of self-replication, with a full system of multiple Stanford toruses being eventually built.

Chosen shape

The 1975 NASA Summer Study evaluated several options for the space habitat design, including spherical and cylindrical shapes, in addition to the toroidal one. The torus was chosen as the best option, among other reasons, because it minimized the amount of mass required to have the same area and radius of rotation.

General characteristics

Location: Earth–Moon L5 Lagrangian point.
Human population: 10,000.
Total mass: .
Diameter:.
Circumference: 5,623.45 m.
Rotation: 1 revolution per minute.
Temperature:
Radiation shield : thick raw lunar soil.
Components
Habitation tube with a diameter of. 2/3 of its surface consists of aluminum plates and the remaining 1/3 is filled with glass windows mounted on aluminum ribs, to allow sunlight to enter inside the torus.
Non-rotating main mirror that directs sunlight towards the central hub.
Central hub with a diameter of. Secondary mirrors around the central hub direct sunlight towards the habitation tube.
Fabrication sphere, connected to central hub's South Pole, with a diameter of. It is also connected to a solar furnace and the habitat radiator.
Docking module, connected to central hub's North Pole, with a diameter of and a length of.
Spokes: 6 spokes of diameter, connecting the central hub with the habitation tube. They have elevators, power cables, and heat exchange pipes between the torus and the hub.
Area and volume allocation

The circumference of the torus proper would be divided into 6 sections of equal length. 3 of the sections would be used for agriculture and the remaining 3 for residential uses. Agricultural and residential sections would alternate. A central plain would run through the full length of the torus. To gain space, structures would be terraced over the curved walls of the torus, while many commercial facilities would be below the level of the central plain. According to the figures included in the study, the plain's floor would be about 1/4 of tube's diameter over the torus bottom, and each spoke would connect at the center of one of the 6 sections.

Non-agricultural uses

Use	Used land area	Number of levels	Total usable area	Height per level	Volume	Notes
Residential		4				Including dwelling units, private exterior space and pedestrian access space. Modular housing, allowing for one- or two-level clustered homes, as well as grouped apartment buildings with 4 or 5 stories, and terraced homes taking advantage of the edges of the central plain that runs through the torus
Shops		2				The authors of the study determined the space use from recommendations that call for 10 shops per 1000 people
Offices		3
Schools		3				With community multimedia center. The authors of the study calculated the space use for a student population of 10% of total population
Hospital		1				50-bed hospital with all the different needed facilities
Assembly		1
Recreation and entertainment		1				All commercial entertainment, including indoor activities and restaurants
Public open space		1				Parks, zoo, outdoor recreation
Service industry		2				Light service industry of personal goods, furniture, handicrafts, etc.
Storage		4				Wholesaling and storage
Transportation		1				width for typical streets. Ring road around the torus, at the edge of the central plain. Mass transport system consisting of a moving sidewalk, monorail, and minibus
Communication switching equipment		1				Communication and telephone distribution
Waste and water treatment and recycling		1				Including water supply, return and recycling, and sewage treatment
Electrical supply and distribution		1				Including transformer substations
Miscellaneous		2
Total		-		-

Agricultural uses

Use	Used land area	Number of levels	Total usable area	Height per level	Volume	Notes
Plant growing areas		3				List of crops: for sorghum; yield of for soybeans; yield of for wheat; yield of for rice; yield of for corn; yield of for vegetables; yield of. Each of the three agricultural areas in the colony grows the same crops. Part of the plant production is used to feed livestock. Sorghum is used to obtain sugar. Fruit trees are grown in parks and residential areas, providing of fruit per person each day, and also serving as ornamentation.
Animal areas		3				Stable herd of animals: 260,000 fish 62,000 chickens 28,000 rabbits 1,500 cattle. Each one of the three agricultural sections holds around a third of the animals of each species. Flexibility is allowed for other animals to replace parts of these numbers.
Food processing, collection, storage, etc.		3
Agriculture drying area		3

Totals

Construction

The torus would require nearly of mass. Construction would use materials extracted from the Moon and sent to space using a mass accelerator. A mass catcher at L2 would collect the materials, transporting them to L5 where they could be processed in an industrial facility to construct the torus. Only materials that could not be obtained from the Moon would have to be imported from Earth. Asteroid mining is an alternative source of materials.

World ship proposal

The 2012 paper World Ships – Architectures & Feasibility Revisited proposed a generation ship based on the Stanford torus. The Stanford torus was chosen over O'Neill colony designs because of its detailed design that covers in-depth aspects such as life support systems and wall thickness.
Four Stanford torus colonies would be stacked together, each with a population of 25,000, for a total population of 100,000, the minimum population size that the paper considers for a world ship.
For the propulsion system, an upscaled version of the one designed in Project Daedalus was chosen. A single Daedalus-based system, with a mass of around 500,000 tonnes, would be attached to the centers of the four toruses. Daedalus would provide other additional features, such as power generation and a dust shield to protect the toruses from interstellar dust impacts.
The world ship would also need a fully automatic fail detection and self-repair system, to prevent failures from having catastrophic effects.