Space-based missile defense systems could jeopardize astronomical research and space exploration

EMBARGOED: Not for release until 11 a.m. Paris Time (5 a.m. U.S. Eastern Time) Friday, April 19, to coincide with Joel Primack's talk at a UNESCO conference.

The Bush administration's plan to develop space-based missile defense systems has generated heated debate, but most commentators have overlooked an important and potentially destructive consequence of placing weapons in orbit around the Earth. The militarization of space could create a permanent halo of orbiting debris that will interfere with important scientific and communication satellites, according to Joel Primack, professor of physics at the University of California, Santa Cruz.

"In science fiction movies like Star Wars there are constant explosions, but a few seconds later the screen is clean. It's not going to work that way near a planet," Primack said.

About 3 million kilograms of space debris (roughly 6 million pounds), from dead satellites to paint chips, already orbit the Earth. The U.S. Space Command tracks over 9,000 objects larger than four inches in diameter, and operational satellites can take evasive action to avoid being hit by one of these larger objects. In the range from four inches down to about the size of a marble, there are relatively few objects now in orbit.

The most serious hazard currently is the non-trackable debris smaller than a marble that orbits the planet at speeds around 17,000 miles per hour, 10 times faster than a bullet from a high-powered rifle, Primack said. A BB-sized fragment traveling that speed has the destructive power of a bowling ball moving over 60 miles per hour, and a marble-sized fragment can do even more damage. Satellites are armored, but they can only withstand BB-sized particles. Even the International Space Station is vulnerable to any debris much larger than a BB.

Space-based missiles will generate huge amounts of small debris particles, said Primack. Some will arise from weapon explosions, but even more will come from the resulting small projectiles hitting larger objects already in orbit and fragmenting them. According to Primack, so many bits of junk could eventually be orbiting the Earth that no satellite or space station could be operated in Low Earth Orbit, 200 to 1,250 miles above the planet. Space shuttles and other space vehicles would need heavy armor to pass through the debris.

Most communications satellites are located in higher orbits that would not be as affected by the debris, but some, such as those for mobile phones, are in lower orbits and already in danger. No methods to remove space debris now exist.

"If we do this, we're going to create a terrible problem there's no easy solution for, but the space debris aspect of a 'Star Wars' missile system is just not talked about in the public arena," Primack said.

Primack will give a talk on this issue on April 19 at the United Nations Educational, Scientific and Cultural Organization (UNESCO) headquarters in Paris during the Science and the Quest for Meaning Conference. The conference explores the connections between science and spirituality.

Primack said it would be unethical and immoral to jeopardize peaceful uses of space for short-term military gains. Like many researchers, Primack relies on data from astronomical satellites in Low Earth Orbit, where missile defense systems would also be located. His theoretical work on the nature of the "dark matter" in the universe, for example, was supported by evidence from the Cosmic Background Explorer (COBE) satellite, which detected fluctuations in the first light of the universe. Space-based telescopes are ushering in a new era in space research, and Primack said he believes researchers will soon be able to answer fundamental questions in cosmology.

"The data from COBE, the Hubble Space Telescope, and other new observatories should at last give astrophysicists a solid foundation on which to construct an overarching theory of the origin and evolution of the universe, an achievement that is also bound to have deep implications for the development of human culture," Primack said.

In 1993, NASA issued the Policy to Limit Orbital Debris Generation, but it has had little impact, Primack said. He hopes that an international treaty prohibiting explosions in space and requiring all satellites to carry mechanisms to de-orbit them safely will be created in the future.

"Every person who cares about the human future in space should also realize that militarizing space jeopardizes the possibility of space exploration," Primack said.

Primack is not new to questions of scientific ethics and policy. He helped to create the American Physical Society Forum on Physics and Society and teaches a course on "Cosmology and Culture" with his wife, attorney Nancy Ellen Abrams, at UC Santa Cruz.

The Science and the Quest for Meaning Conference is sponsored by Science and the Spiritual Quest II and the Université Interdisciplinaire de Paris. More information about the conference is available at


Editor's note: Reporters may contact Joel Primack at (831) 459-2580 or until April 17, or after the conference. To reach him during the conference, contact Tim Stephens in the UCSC Public Information Office at (831) 459-2495 or