Jane's Defence Weekly
High-Altitude Nuclear Explosions: Blind, Deaf And Dumb
A new threat based on Cold War nuclear knowledge has US defence analysts concerned. If a high-altitude nuclear explosion were launched by a rogue state, most satellites in low earth orbit would cease to function within weeks. Ian Steer weighs up this asymmetric threat
If stable states and rational dictators can be deterred from using nuclear weapons, as current wisdom has it, then the main nuclear threats are from terrorists with suitcase bombs and lunatic autocrats with missiles. This is based on a limited idea of what one can do with a small nuclear weapon.
However, blowing up targets on the Earth's surface is only part of the story. According to Dr Dennis Papadopoulos, from the Department of Physics, University of Maryland: "If someone were to explode a 10kT nuclear weapon at a high enough altitude over their own territory, 90% of the world's low earth orbit [LEO] satellites would be lost within a month."
In addition to the electromagnetic pulse (EMP) phenomenon, generally understood, satellites are vulnerable to the 'Christofilos Effect'.
When a high-altitude nuclear explosion (HANE) is detonated at about 100km altitude, the Earth's magnetic field accelerates the large cloud of electrons and protons released by the blast. The radiation particles speed up, spread out, all the while accelerating, circling the globe until racing around it at speeds approaching the speed of light. This effect is named after Dr Nicholas Christofilos, who predicted this phenomenon.
The detonation "produces an artificial radiation belt that, within weeks to at most months, delivers a 'lethal' dose of radiation to [LEO] satellites," said Dr Papadopoulos, who worked with Dr Christofilos at what is now the Lawrence Livermore National Laboratory.
The superpowers conducted six scheduled nuclear explosions in space during the Cuban Missile Crisis. These HANEs damaged or destroyed all seven satellites then in orbit. These tests, conducted before the 1963 Atmospheric Test Ban Treaty, provided the only experimental data on the vulnerability of satellites to nuclear detonation.
Today, the implications of a HANE are far greater, as millions use the 250-plus satellites in LEO. "As for the military satellites, it is likely they have been hardened well enough to survive the duration of any war," said John Pike, president of the GlobalSecurity Organisation, a beltway-based think-tank with an anti-proliferation agenda. "But it's certainly too great a risk to ignore because of the increasing reliance of the military on civilian systems, which are not hardened."
"We don't see it as a high-probability threat, but the effect would be so devastating we have to take it seriously and be prepared to act," said Dr Papadopoulos.
Armed forces have long relied largely on civilian satellites to relay military communications, navigation, weather forecasting and imaging information. Satellite telephone systems, for example, are essential for peacekeepers who operate regularly in remote areas or in locations where infrastructure has been damaged or destroyed. The US military has also relied on National Aeronautics and Space Administration (NASA) civilian satellites to help plan for its continuing operations in Afghanistan and present and possibly future operations in Iraq.
The International Atomic Energy Agency (IAEA) also uses civilian imaging satellites to monitor states' compliance with the Non-Proliferation Treaty (NPT).
By using a HANE, a country does not need an intercontinental ballistic missile (IBCM) to launch a strategic attack on a distant country, nor does it need to invite annihilation by targeting population centres. A HANE would damage and/ or destroy a country's national investment in space.
According to the US Department of Defense (DoD) Threat Reduction Agency's (DTRA's) HALEOS (HANEs against Low Earth Orbit Satellites) study published in 2001, it would cost more than $100 billion to replace civilian satellites operating in LEO. This includes around $30 billion for the International Space Station, $10 billion for the Hubble Space Telescope and another $10 billion for space shuttles and other astronomy and research satellites.
Every individual and business that relies on basic communications technology would be affected. A more sinister consequence of HANEs is that they amplify the Earth's Van Allen radiation belt to levels that remain high enough to damage satellites for up to two years. So, a HANE would affect many people and systems while they waited for the radiation level to fall to a point when new satellites can be launched.
A HANE would directly affect military operations both in and out of theatre. Traditionally US soldiers fight far from home. But now, if Iraq or North Korea, for example, launched a HANE above their respective countries, it would cause collateral damage on home soil. Although a HANE launched overhead in Iraq or North Korea during operations in the area might not stop the US military in its tracks, it would cause serious damage and confusion. In the case of Iraq, US Central Command's core headquarters is based in Tampa, Florida, USA. Its forward-deployed headquarters is in Qatar. Similarly, the US core headquarters for North Korea is based in the USA. Its forward-deployed headquarters is in South Korea. In both cases, a HANE would make communications via civilian satellite impossible. If a HANE occurred over a military theatre, much would come to a halt. HANEs release a high-altitude electromagnetic pulse (HEMP) which is deadly to electronics within line-of-sight of the blast.
"When the lights went out in Hawaii after one of the 1962 nuclear tests, scientists began to make a connection between nuclear weapons and EMP," said Dr Robert Norris of the US global watch organisation the Natural Resources Defense Council. "Theoretically, one nuclear weapon detonated high over the central USA would fry a vast amount of computers and communications equipment, including all radio and television over a wide area."
Any aircraft, civil or military, caught within the line-of-sight of a HANE could lose all electronics. The effect depends on range and if the aircraft is hardened. The US Air Force's E-8C Joint Surveillance and Target Attack Radar System, a key element to the USA's current battlefield reconnaissance architecture would likely fall victim to this. Based on an old Boeing 707 airframe, it is unlikely it is protected against such eventualities. Other tactical communications linkages such as air-to-ground tactical radios would also be affected.
Any nuclear-armed state capable of launching a satellite could detonate a HANE. For a state to launch a HANE it must, however, have both intent as well as capability.
The 2001 HALEOS studies considered various threat scenarios. The primary concern was that HANEs could be launched as a warning shot. A nuclear-armed state facing military defeat could, for example, detonate a HANE in LEO as a demonstration of capability and resolve.
Another scenario involves an accident. A country like North Korea might launch a nuclear-tipped Taepo Dong missile at a ground target like Seoul only to have it intercepted by a US anti-ballistic missile (ABM). It might then, either accidentally or due to salvage fusing, detonate as a HANE at an altitude of between 120km and 150km.
Given a plausible scenario, which players have the capability; missiles and fissile material; but no satellites of their own to lose?
North Korea demonstrated its missile prowess two years ago when it launched its Taepo Dong intermediate-range ballistic missile (IRBM) over Japan. Iran and Iraq are developing longer-range, higher-payload IRBMs of which at least some flyable examples likely already exist.
All three states have or have had newer, improved model 'Scud-C' short-range ballistic missiles (SRBMs) with a range of 500km and 500kg payloads. This raises the idea that even SRBMs could be a future threat.
The amount of 90% pure plutonium (Pu239) required to make one 20kT nuclear bomb, known as a "bare" critical mass, is known to be 10kg. The most basic plutonium-based atom bombs, however, surround the plutonium sphere with a beryllium neutron reflector to enhance the nuclear reaction. As a result, they can use less Pu239.
Because the design is so basic and beryllium is so easy to acquire, most defence analysts now use the reflected critical mass figure, 5kg, as the minimum reaction mass in a nuclear device.
The same is true for a uranium device. It takes 52kg of pure U235 to make one 20kT atom bomb. The reflected critical mass surrounded by beryllium is only around a third as much, or 15kg.
"US intelligence agencies now believe North Korea may well have one or two nuclear explosives already," said Matthew Bunn, senior research associate in the Project on Managing the Atom at the Belfer Center for Science and International Affairs at Harvard University's John F Kennedy School of Government.
Corey Hinderstein, assistant director of the Institute for Science and International Security (ISIS), estimates that "North Korea could have between 30kg and 40kg of weapons-grade plutonium". The ISIS estimate credits North Korea with enough plutonium to make six or eight atom bombs. Most of the material is under IAEA safeguards, but one or two atom bombs-worth is not. Following a 1994 agreement with Washington to comply with IAEA and NPT requirements, IAEA inspections in North Korea are to begin in 2004.
Current estimates indicate that Iraq has no fissile materials. But as IAEA inspectors have been expelled since November 1998, it will be some time before the real situation in Iraq can be verified.
Assuming a country has the materials, can it quickly turn them into nuclear weapons? In the past it was generally believed this would be difficult. Now that nuclear proliferation has spread beyond the five main nuclear powers - China, France, Russia, the UK and the USA - the 'know-how' hurdle does not look so high.
The most obvious solution to HANEs is to harden civilian satellites. In fact, this is not an option with current technology. More shielding means more weight.
There are two methods to prevent HANEs: military or political. Israel demonstrated the military option in 1982 by destroying Iraq's Osirak nuclear reactor. The USA employed the same technique in 1991 against other weapons of mass destruction sites in Iraq. The alternative route is to stiffen the NPT. Certain 'research' reactors and nuclear facilities, like uranium enrichment plants, are not subject to IAEA safeguards. "The greatest danger facing the NPT is new technologies not envisioned when the treaty was signed," as Colin Hunt of the Canadian Nuclear Association told Jane's Intelligence Review in 1998. "It is now possible to make certain kinds of weapons proliferation extremely difficult to detect and prevent."
If agreements like the one the USA has with North Korea and Russia with Iran are indicative, the answer may lie in co-operation. It is safer to have such nations producing even more plutonium under IAEA inspection than less plutonium without monitors: it is easier inside than outside a country to keep track of nuclear programmes.
Three weeks ago, Turkish officials allegedly seized 15kg of "weapons-grade uranium". Immediately after the seizure, Bunn said: "Typically, as has been the case in most such seizures in the past, such claims are false, so when the tests on that material are released I'm betting they'll show it wasn't weapons-grade and it probably wasn't that much." In fact, as predicted by Bunn, the contraband was 0.12kg.
With at least 12 IAEA-recognised cases of black-market nuclear weapons materials, could a country simply buy them off the shelf? Estimates of the total amount of weapons-grade plutonium and highly enriched uranium seized during the 1990s amount to less than 15kg; much of it not even weapons-grade. Based on drug interdiction, which catches an estimated 10% of the total traffic, a worst-case upper estimate for the total traffic worldwide in black-market fissile materials (mostly involving enriched uranium) might be around 15kg or enough for one nuclear bomb per year. "The only solution is to have strict controls, monitoring, compliance and enforcement of the NPT," said Bunn.
Proliferation on the black market of already assembled nuclear weapons, including missing Russian 'suitcase' nuclear bombs, is a threat. Unrecognised is the additional proliferation route open thanks to the more than two dozen fully assembled nuclear weapons lost at sea to date. How long will it be before the civilian ocean robots used to find the Titanic 3km deep are able to recover one or more of these 'lost nukes'?
If a HANE were launched today, there would be no way of dealing with it. Instead of focusing on strategic anti-ICBM defences, like the Strategic Defense Initiative, almost the entire thrust of ballistic missile defence spending is devoted to tactical, anti-IRBM missiles, precisely because these are the most immediate foreseeable threat.
First out of the gate to demonstrate limited IRBM interception capabilities and achieve operational status is the Israel Aircraft Industries' Arrow anti-tactical ballistic missile (ATBM) in 2000. Next may well be the US Navy's (USN's) new improved Standard SM-3 surface-to-air missile/ABM missile interceptor, now in flight-tests. Capable of 8km/s or 29,000km/h, this ABM would fire from vessels that could be stationed near Iraq or North Korea.
Few if any of the other continuing programmes seem this close to 'launching'. There is one that could break out of development quickly. Known as the USAF YAL-1A Airborne Laser aircraft, the platform is a modified Boeing 747-400F which will be armed with a high-energy chemical oxygen iodine laser (COIL), and a sophisticated beam-control system. It will be capable of shooting down IRBMs.
The test aircraft is expected to fly within months, but it is unlikely to fly with the COIL and beam-control systems until early 2004 as they are still under development (Jane's Defence Weekly 5 June).
According to the satellite vulnerability study, it might be possible to reverse the Christofilos Effect. "We discovered that if you can produce kilohertz waves and transmit them into space, they cause the radiation which otherwise would remain aloft for years to precipitate or rain out of orbit much more quickly," said Dr Papadopoulos, referring to research supported by Advanced Power Technology, Inc.
The largest radio transmitters in the world are envisaged to lead the project. The USN operates two extremely low-frequency transmitters in Michigan and about 10 very low-frequency transmitters around the world expressly to allow signals anywhere in the world to any vessel, especially submerged USN submarines. "At first, our studies indicated it would take thousands of such stations to return the radiation belt to normal but we discovered an amplification technique that improves this method by a factor of almost 100. So, with only 10 times the number of existing transmitters it might be possible to get the belt to safe levels in a much shorter time, say in a few months," he said.
According to Dr Richard Garwin of the US Council on Foreign Relations, a HANE attack is deterrable. "We do not believe it is something another country would be likely to do, knowing that if they did, their launch would be detected and that if it hurt US interests they would be subject to our retaliatory nuclear attack."
Deterrence in this case, however, is not so clear-cut. Retaliation against people is not necessarily an appropriate response to losing hardware. While it is plausible to suggest that the USA would use a B-61 tactical nuclear weapon to take out the offending missile launch site, that sort of belated counterforce would be small comfort in a world without pagers or CNN. Of those 10 countries with the capability, China, France, Russia, the UK and the USA are the least likely to launch a HANE because they have the most to lose. In the cases of Iran, Iraq or North Korea, a remote launch site may well be a chess piece that a state is willing to sacrifice.
Additional reporting: Melanie Bright, JDW Features Editor, London
Copyright © 2002 JDW
