Question: In what year did the inventor of the mass driver propose a design for a space settlement?

Context paragraphs:
International Space Settlement Design Competition: The International Space Settlement Design Competition, more commonly known as "Spaceset" or "I-SSDC", is an annual competition founded by Anita Gale and Dick Edwards, and is supported (but no longer sponsored) by NASA (as the competition rents several NASA facilities for use during the competition).  The competition targets high school students and recreates the experience of working on an aerospace company's proposal team.  The teams are asked to envision space colonies in accordance to an RFP (Request for Proposal).

Alliance for Space Development: The Alliance for Space Development is a space advocacy organization dedicated to influencing space policy towards the goal of permanent human settlements in space.  The founding executive members of the Alliance are the National Space Society and the Space Frontier Foundation.  Member organizations of the Alliance are the Lifeboat Foundation, Mars Foundation, Mars Society, Space Development Steering Committee, Space Tourism Society, Students for the Exploration and Development of Space, Students on Capitol Hill, Tea Party in Space, and the Texas Space Alliance.  The primary goals of the Alliance are to elevate the growth of the space industry, reduce the cost of accessing space, and to clearly define space settlement as the reason for sending humans to space.

Gerard K. O'Neill: Gerard Kitchen O'Neill (February 6, 1927 – April 27, 1992) was an American physicist and space activist.  As a faculty member of Princeton University, he invented a device called the particle storage ring for high-energy physics experiments.  Later, he invented a magnetic launcher called the mass driver.  In the 1970s, he developed a plan to build human settlements in outer space, including a space habitat design known as the O'Neill cylinder.  He founded the Space Studies Institute, an organization devoted to funding research into space manufacturing and colonization.

O'Neill cylinder: The O'Neill cylinder (also called an O'Neill colony) is a space settlement design proposed by American physicist Gerard K. O'Neill in his 1976 book "".

Space habitat: A space habitat (also called a space colony, space settlement, orbital habitat, orbital settlement or orbital colony) is a type of space station, intended as a permanent settlement rather than as a simple way-station or other specialized facility.  No space habitats have yet been constructed but many design proposals have been made, with varying degrees of realism, by both engineers and science fiction authors.

The High Frontier: Human Colonies in Space: The High Frontier: Human Colonies in Space is a 1976 book by Gerard K. O'Neill, a road map for what the United States might do in outer space after the Apollo program, the drive to place a man on the Moon and beyond.  It envisions large manned habitats in the Earth-Moon system, especially near stable Lagrangian points. Three designs are proposed: Island one (a modified Bernal sphere), Island two (a Stanford torus), and Island 3, two O'Neill cylinders.  These would be constructed using raw materials from the lunar surface launched into space using a mass driver and from near-Earth asteroids.  The habitats were to spin for simulated gravity and be illuminated and powered by the sun.  Solar power satellites were proposed as a possible industry to support the habitats.

Mass catcher: A mass catcher is a theoretical device envisioned to decelerate a mass of material, usually in the context of outer space transport.  A large object placed in space with a conical shape would stop other objects hurtling towards the center of the back of it.  These other objects would not bounce back into space because small debris from previous impacts with the mass catcher would form a coating similar to regolith, which would absorb the impact and decelerate the object to the velocity of the mass catcher.  Interstellar transport of bulk materials would be a potential source of demand for the construction of a mass catcher (e.g. lunar or asteroidal mined ore originally accelerated into a trajectory intercepting the mass catcher by a mass driver).  This device was proposed in 1978 by Thomas A. Heppenheimer.

International Space Development Conference: The International Space Development Conference (ISDC) is the annual conference of the National Space Society (NSS).  Now in its 33rd year, these conferences connect the general public and the NSS membership with leaders of contemporary space efforts.  The ISDC provides a nexus for industry, government, scientists, advocates, and the public to meet and discuss the latest issues in space technology, science, policy, commerce, medicine, exploration, settlement and much more.  Winners of the annual NASA space settlement Contest annually attend the conference, with several interesting activities and programs.  With National Space Society's major goal being to accelerate the process of space exploration and development they also foster astronautics for students by encouraging them and getting them involved.

NASA Space Settlement Contest: The NASA Space Settlement Contest is an annual design competition for 6-12th grade students sponsored by the NASA Ames Research Center and the NSS (National Space Society).  This contest is open to students ages eleven through eighteen from anywhere in the world.  Individuals compete as individuals or part of a team in two categories, in teams of up to six students, and in teams of seven or more students.

Mass Driver 1: Constructed in 1976 and 1977, Mass Driver 1 was an early demonstration of the concept of the mass driver, a form of electromagnetic launcher, which in principle could also be configured as a rocket motor, using asteroidal materials for reaction mass and energized by solar or other electric power.

Supporting paragraphs: O'Neill cylinder Gerard K. O'Neill
Answer: 1976