Jon Titus's Nov.16 letter proposes the use of high-altitude electromagnetic pulse (HEMP), caused by detonating a nuclear weapon in space, to halt Iran's nascent nuclear program. Perhaps I am missing some subtle irony or humor on his part, but this is the most ill-advised idea I have ever heard seriously suggested.
A HEMP in space would cause irreparable damage not only to electronics in Iran, but throughout the region, if not the entire Eastern Hemisphere. (Eastern China is less than 800 miles from Iran, and U.S. troops in Afghanistan would also have their electronics knocked out.) It would instantly vaporize or render inoperable literally thousands of satellites already in orbit, potentially including any geosyncronous orbit (GEO) satellites within line of sight. This is because nuclear radiation in space travels much farther than in the lower atmosphere, due to the paucity of molecules to absorb it. This would destroy or degrade space-based communication, TV and radio, navigation and other capabilities upon which the modern world depends.
What's more, it would seriously degrade and disrupt our own global-positioning-system constellation, which requires a minimum of 24 satellites in a particular configuration to operate. Any GPS satellites in view of the burst would be destroyed or at least severely degraded. Banks, stock exchanges and many other time-sensitive enterprises world-wide, which depend upon precise time signals from GPS, would be thrown into disarray and panic, to say nothing of the millions of angry motorists who would have useless GPS receivers in their cars.
Most frightening would be the potential consequences to satellites in low-earth orbit, loosely defined as any orbit below 2,000 kilometers. This is an extremely crowded area of space. Assuming, charitably, that no orbital debris is generated by the proposed nuclear detonation, satellites in this orbit already have to contend not only with each other, but with tens of thousands of smaller pieces of debris, such as that created in 2007 by the Chinese anti-satellite test, or in 2009 by the collision of a defunct Russian spy satellite with an Iridium communications satellite.
It is precisely the ability to maneuver in orbit that prevented these mishaps from destroying even more satellites. But the thousands of dead satellites created by the HEMP could not be maneuvered.
In a nightmare scenario, we would have a "Kessler Syndrome," named after former NASA scientist Donald Kessler, who predicted in 1978 that orbital debris could reach a threshold in which colliding satellites created exponentially more debris, causing a chain reaction of orbital collisions until orbital space became literally unreachable and thus unusable.
Furthermore, those satellites not destroyed by the initial HEMP burst would find their solar panels and internal electronics degraded by the highly radioactive particles trapped in the Van Allen belts, particularly in the South Atlantic Anomaly, a portion of the Van Allen belts that dip into low-earth orbit due to the shape and inclination of the Earth's magnetic field. (Astronauts don't perform spacewalks when passing through it, for example, and many satellites shut down critical sensors and other electronics to avoid damage.)
These and other scenarios denying humans the critical use of space are what keep world leaders and space professionals such as myself up at night. We certainly don't need any of Mr. Titus's kind of help in this regard.
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