Project West Ford

Project West Ford (also Westford Needles and Project Needles ) was to create an experimental passive space-based communication system, which was conducted by the Lincoln Laboratory of the Massachusetts Institute of Technology on behalf of the U.S. armed forces in 1961 and 1963, an orbital belt of 480 million copper dipole antennas should enable the global radio communications.

Principle of operation

The West Ford dipoles consisted of 1.78 cm long and the first experiment 25.4 microns and 17.8 microns in the second thick copper wires. The length of the needles corresponding to the half wavelength of the 8 GHz transmission frequency used in the program.

A total of 480 million this wire dipole antennas embedded in a Naphthalinmatrix. The called dispenser cylindrical naphthalene needle block is driven in rotation and repelled from the carrier rocket. In vacuo, the sublimated naphthalene in a short time, releasing the dipoles that have been repelled by the rotation at different speeds. Thus, the dipoles were spread over the entire orbit. The bulk of the 480 million dipoles was only about 20 kg.

The West Ford dipoles were distributed in the orbit of the parent satellite. These were polar orbits 3500-3800 km Railway height and inclinations of 96 ° and 87 ° in the two tests. The dipoles were distributed in a belt about 15 km wide and 30 km radial extent along the orbit. The average distance between the dipoles was about 400 m.

All transmission technology was with this system in the ground stations. The radiated electromagnetic waves from the transmission station have been reflected from the dipoles, and receive from the other station.

Starts

The first attempt to distribute the West Ford dipoles in space, the distributor arrived while successfully together with the satellite MIDAS -4 into orbit, however, the dipoles were not distributed. The launch took place on 21 October 1961 an Atlas - Agena B rocket from Vandenberg Air Force Base. Due to a malfunction of the MIDAS - 4 satellite, the dispenser was indeed expelled, but not rotated, so that a large number ( about 40,000 ) of needle clusters formed, although not as planned distributed over the entire orbit.

The second attempt on 8 May 1963, successfully. The dipoles came together with MIDAS -7 into orbit and successfully distributed. The dipole needles distributed to a erdumspannenden belt over a period of about 40 days.

Results

Communication experiments at the Dipolwolken not yet fully distributed achieved shortly after the start data transfer rates up to 20,000 bps. After four months, as the dipoles were evenly distributed, but only 100 bps were achieved. This rapid loss of transmission capacity was, besides the progress in the construction of active communications satellite, one of the reasons why no further experiments of this kind were carried out. The last transmissions arrive in 1965, and a majority of the dipoles was re-entered the Earth's atmosphere by the end of the 1960s.

Upon release of the dipoles, there was clumping of the individual dipoles, so that no optimal distribution could be achieved. These so-called cluster clumps consisted of both parallel and serial arrangements of. The compact parallel arrangements had a more favorable ratio of mass to the air friction, making this a much longer orbital lifetime had as the individual needles.

Criticism

During the planning, the project experienced considerable resistance from areas of astronomy, which feared a disability of astronomical observations in the field of optical astronomy and radio astronomy. Another point of criticism was the risk to other spacecraft through the large number of released Project in Westford particles. With each 480 million released objects presented the Westford experiments one of the main sources for the space debris in the middle path heights dar. In 2006, there were still numerous needle cluster in orbit, even if the numbers are constantly reduced by re-entries.

The international protests against the West Ford experiment led to the inclusion of a consultation clause to dangerous space experiments in the Outer Space Treaty, adopted in 1967. The final blow for the West Ford technology came through to be superior proven active communications satellite, which provided a significantly better transfer performance.