Project West Ford

West Ford Needles versus a postage stamp

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

Working principle

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

A total of 480 million of these wire dipoles were embedded in a naphthalene matrix. The cylinder-shaped naphthalene needle block, known as the dispenser , was set in rotation and ejected by the launch vehicle. In a vacuum, the naphthalene sublimated in a short time and released the dipoles, which were repelled by the rotation at different speeds. As a result, the dipoles were distributed over the entire orbit. The mass of the 480 million dipoles was only about 20 kg.

The West Ford Dipoles were deployed in the orbit of the parent satellite. In the two tests, these were polar orbits between 3500 and 3800 km orbital height and inclinations of 96 ° and 87 °. The dipoles were distributed in a belt about 15 km wide and about 30 km radial extension along the orbit. The average distance between the dipoles was about 400 m.

With this system, all active devices required for transmission were located in the ground stations. The electromagnetic waves emitted by the transmitting station were reflected by the dipoles and received by the other station.

Starts

Start of the first West Ford experiment on an Atlas Agena rocket

During the first attempt to distribute the West Ford dipoles in space, the distributor successfully entered orbit together with the MIDAS-4 satellite, but the dipoles were not distributed. The launch took place on October 21, 1961 on an Atlas Agena B rocket from Vandenberg Air Force Base . Due to a malfunction of the MIDAS-4 satellite, the dispenser was ejected but not set in rotation, so that a large number (around 40,000) of needle clusters formed, which did not spread over the entire orbit as planned.

The second attempt on May 8, 1963 was successful. The dipoles entered orbit along with MIDAS-7 and were successfully distributed. Over a period of about 40 days, the dipole needles spread to form a belt that spanned the earth.

Results

Communication experiments on the not yet fully distributed dipole clouds achieved data transfer rates of up to 20,000 bps shortly after the start  . After four months, however, when the dipoles were evenly distributed, only 100 bps could be achieved. This rapid loss of transmission capacity, along with advances in the construction of active communications satellites, was one of the reasons why no further experiments of this type were carried out. The last transmissions were in 1965, and most of the dipoles had re-entered the earth's atmosphere by the late 1960s.

When the dipoles were released, the individual dipoles clumped together so that an optimal distribution could not be achieved. These clusters, known as clusters, consisted of both parallel and serial arrangements. The compact parallel arrangements had a more favorable ratio of mass to air friction, so that they had a significantly longer orbital life than the individual needles.

criticism

Already during the planning phase, the project encountered considerable resistance from areas of astronomy, which feared an obstacle to astronomical observations in the areas of optical astronomy as well as radio astronomy. Another point of criticism was the endangerment of other spacecraft by the large number of particles released in Project West Ford. With 480 million objects released each, the West Ford experiments were one of the main sources of space debris at medium orbit altitudes. In 2006, numerous needle clusters were still in orbit, even if the number is steadily decreasing due to reentries.

The international protests against the West Ford experiment led to the insertion of a consultation clause in dangerous space experiments in the 1967 adopted Outer Space Treaty . The final end for the West Ford technology came through the active communication satellites, which proved to be superior and offered significantly better transmission performance.

Web links

• Article about Project West Ford (English)
• Gunter's Space Page: articles with pictures (English)

Individual evidence

1. ^ II Shapiro , HM Jones and CW Perkins: Orbital properties of the West Ford dipole belt . In: Proceedings of the IEEE . Volume 52, No. 5, May 1964, pp. 469-518 (abstract, English)
2. ^ ^{A b} Donald Martin, Paul Anderson, Lucy Bartamian: Communication Satellites . 4th edition, The History of Satellites - West Ford
3. ^ ^{A b} C. Wiedemann, H. Krag, P. Wegener and P. Vörsmann: The orbital behavior of clusters of copper needles from the West Ford experiments ( Memento from January 8, 2010 in the Internet Archive ). In: DGLR yearbook 2002 . Volume II, pp. 1009-1017
4. ↑ ^{a b} SP-4217 Beyond the Ionosphere history.nasa.gov
5. ↑ Anthony Kendall: Earth's Artificial Ring: Project West Ford ( Eng. ) DamnInteresting.com. May 2, 2006. Retrieved October 16, 2006.
6. ↑ ^{a b} The Air Force Role in Developing International Outer Space Law (PDF; 533 kB) page 63, Chapter 4 project West Ford
7. ↑ Position Paper on Space Debris Mitigation - Implementing Zero Debris Creation Zones (PDF; 753 kB) International Academy of Astronautics, October 15, 2005
8. ↑ RAE Table of Earth Satellites ( Memento from September 29, 2007 in the Internet Archive ) (MS Word doc; 140 kB) 2000, Extra-page-1 to Extra-page-4, "148 pieces, 92 have decayed"