In 1929 John Desmond Bernal designed a concept for a visionary form of interstellar space structure. Known thereafter as a “Bernal sphere”, the vessel was essentially constructed from asteroid and Moon material, 16 km in diameter with a population of around 20,000 people. A atmosphere would be provided within the structure so that it became a self-contained habitat. The outer shell would be hard, transparent and thin, preventing the escape of gas and allow for the preservation of a rigid structure. The Bernal sphere was mainly designed as a space habitat, but this visionary ideas laid the ground work for the more rigorous studies that were to follows. The American engineer Gerrard K.O’Neill took this work to a new level in the 1970s when he also designed large human habitat structures that could accommodate tens of thousands of people. O’Neill planned that such structures would be loaced at the L5 point in space, a region where the gravity from the Moon, Earth and Sun is neutral.
The work on large space habitats, laid the groundwork for an even more visionary idea, that of giant World Ships – vesself that would travel the distances between the stars. The motivations for developing world Ships related to the long-term stability of the Sun, the security of the human species against natural of man-made disasters and the undertaking of interstellar exploration for the sake of scientific discovery and human expansion. It was starting from this ground work that in 1984 several members of the British Interplanetary Society dediced to design a credible World Ship concept. In particulr, the time was right to place some focus on slow Starships, instead of the usual fast Starship concepts such as the BIS Project Daedalus study from the 1970s. These World Ships would explore the galaxy on travel times lasting a thousand years or more. The material needed to construct them would come from extraterrestrial resources. The work resulted in the following set of inspirational papers:
- World Ships – Concept, Cause, Cost, Constrution and Colonisation, A.R.Martin
- World Ships – An Effective Assessment of the Engineering Feasibility, A. Bond and A.R.Martin
- The Population Stability of Isolated World Ships and World Ship Fleets, T.J.Grant
- World’s in Miniature – Life in the Starship Environment, A.G.Smith
- World Ships: A Sociological View, D.L.Holmes
In particular, Bond and Martin designed actual World Ship vessesls as an assessment of the engineering feasibility, which are arguably the most detailed consideration of the problem in history. They designed a “Dry World Ship” concept which had a radium of 7.24 km, wall thickness 2.88 m, rotation period 169 seconds. It would require billions of tons of wall mas, regolith mass, atmosphere mass, with the total habitat mass of 168 billions tons. The propellant mass, would be 779 billion tons. The engine would consist of a heterogenous structure called a pulse unit, which would consist of an oblate sphere of frozen hydrogen with a solid deuterium core. Each unit would be ejected from the World Ship, rotating about the flattened polar axis and with its axis along the direction of motion. The pulse units would have small hole leading from the pole facing the world ship down to its core and a metallic slug (the initiator) ejected from the World Ship at about 1,000 km/s would pass down this hold and hit the core. The pulse unit would be several tens of km from the World Ship at the time of detonation. Upon striking the deuterium core a shock system would be established, across which the deuterium would be brough tto self-igniting conditions. Bond and Martin also designed a larger “Dry World Ship” with a radius of 9.66 km, a wall thickness of 5.77 m and a rotation period of 195.3 seconds. The total habitat mass would be around 481 billion tons and the total propellant mass would be around 224 billion tons.
As if that wasn’t enough, they also designed a “Wet World Ship” version. This greatly complicated the engineering problem due to water having a density over 800 times greater than air. The final concept had a radius of 5 km, a wall thickness of 9.15m and a rotation period of 314 seconds. The total habitat mass was 345 billon tons carrying 8,633 billions tons of propellant mass. The ocean mass would total 1,676 billion tons, plenty of water for on board swimming. A modern rendition of the Bond/Martin World Ship concepts is shown in the illustration. This pioneering work also led the way to subsequent papers in the proceeding years, published in the Journal of the British Interplanetary Society, particularly by the American physicist Gregory Matloff on the concept of Non-nuclear Arks.
The special issue of the Journal of the British Interplanetary Society is available as Vol.37, No.6, June 1984 and can be ordered by contacting us here.
Alternatively, the individual papers can be ordered direct from the JBIS web site here: www.jbis.org.uk