The final frontier is set to become a battleground. How will the superpowers fight it out for space supremacy, asks James Oberg

IN A remote valley in New Mexico's Manzano Mountains, the US is tooling up for war. Here, in a four-storey building with walls more than a metre thick, it runs a secret particle-beam project. The weapons it's developing will never be used on Earth because they only work in a vacuum. But that's no problem--the idea is to fire them in space.

Once, space was empty and there was nothing there worth fighting for. Now it's teeming with valuable equipment and tensions are mounting. The US believes a war in space is a virtual certainty--just last month defence secretary Donald Rumsfeld announced plans for upgrading its military presence there. Russia and China are also preparing for combat. And while there are no offensive weapons in orbit today, there's nothing to stop nations from putting them there tomorrow. True, particle beams and other sophisticated weapons are at least a decade away. But some space weapons are so simple that dozens of nations are already capable of building them.

Military strategists have been thinking about orbital combat since the launch of Sputnik 1 in 1957. For the first few years of the space race, their ideas were hopelessly impractical and neither side sent weapons into space--although cosmonauts carried handguns in case of an emergency landing on enemy soil. But soon they began to design, build and test various pieces of anti-satellite (ASAT) weaponry. The US focused on guided missiles, launched from the air and designed to ram the target directly. The Soviets preferred "killer satellites"--orbiting spacecraft armed with shrapnel charges that could disable enemy craft. Both sides also dabbled in nuclear warheads. All were decommissioned without being fired in anger.

The end of the cold war killed off most of the systems, but the threat of space war hasn't gone away. In fact, it's worse than ever. Occupation of space is no longer a two-sided affair. Any government, private organisation--or terrorist group--can buy off-the-shelf satellites and launch them for a few million dollars apiece. Space has become valuable territory, both commercially and strategically. Many nations rely on it for intelligence, and space is teeming with privately owned communications satellites. Taken together these have enormous potential to cause offence. No nation likes to be spied on, and some governments see TV satellites as a weapon of cultural aggression against which defensive measures are justified. Some time soon, someone will be tempted to have a pop.

Analysts agree that the first move will probably be a ground-based electronic assault on a satellite. Some say this kind of attack has already happened. A British military communications satellite was reportedly kidnapped and driven off course by hackers, though officials denied it. Nation states have also been getting in on the act. The pro-government Saudi newspaper Al-Watan has been running a series of articles on communications satellites, in which it accuses broadcasters of spreading "political sedition". The newspaper advocates silencing the offending satellites. And the government of Nauru has accused its neighbour Indonesia of jamming a commercial satellite in orbit over its territory. Indonesia denies the charge.

Jamming a satellite hardly constitutes an act of war, but a more aggressive approach is technically possible and also desirable--the threat of physical damage has always been a useful negotiating tool. The trouble is there's little to stop threats from escalating into violence. Just like the high seas, space is a region beyond national sovereignty. While we have treaties banning weapons of mass destruction in orbit, international law has nothing to say about ordinary space weaponry.

What's more, the fact that space-based technologies are vulnerable to attack hasn't gone unnoticed. As one Chinese newspaper commented in July last year: "For countries that could never win a war by using tanks and planes, attacking the US space system may be an irresistible choice."

The US certainly expects that to happen. Last year a special commission on the military aspects of space concluded that a conflict in space was "a virtual certainty". And during the intelligence community's annual "world threat" briefing in February, the heads of both the CIA and the Defense Intelligence Agency openly voiced their concerns about an attack in space. DIA director Thomas Wilson warned that several foreign governments were experimenting with space weapons. He named China and Russia as the biggest threats and predicted that by 2015, they would be capable of blowing big holes in the US space programme.

In January the US even held a war game based in space. The scenario was set in 2018 and involved an enemy state attacking US satellites that were supporting a military operation on the ground. The results are classified, but the military made its conclusions clear: without more funding for space defence, the US faces a Pearl Harbour in orbit.

Independent experts believe there are no weapons in space at the moment, apart from a gun in the Russian emergency kit on the International Space Station. There's also very little on the ground that could do harm in space. But the technologies to make highly destructive weapons already exist or are in development.

The simplest way to attack a satellite is with weapons launched from the ground. That's the principle behind the "poor man's ASAT" (see Diagram). The idea is to use a small missile to deposit a cloud of sand, ball bearings and other hard objects in the path of an oncoming satellite. The target's own velocity provides the impact energy. It's unreliable, but it poses a credible threat. A dozen countries without space capabilities could build such a system, although none claim to have done so yet.

But there are problems with ground-based weaponry. You can only strike while the target is in range and it takes time for your missile to climb into orbit. That gives the satellite time to take evasive action. For this reason, some strategists want to arm the satellites themselves.

One approach is "parasite satellites"--orbiting limpet bombs that attach themselves to enemy craft for detonation at a later date. The Chinese say they can do this already, though the claim is hard to verify. A simpler method is to disable your enemy with a high-speed projectile. In other words, shoot at it. This was tried in 1974 when the Soviet Union launched Salyut 3, the first crewed military reconnaissance outpost in orbit. In anticipation of an attack by the US, the Soviets mounted a modified machine gun on the satellite so they could greet any hostile approach with a hail of bullets. The attack never came. Salyut 3 proved to be a white elephant and was quickly decommissioned, although not without a shot being fired. After the two-man crew had left, the ground crew fired a few rounds by remote control. It must have been quite a sight.

Shooting projectiles is a standard way of doing combat on Earth, but in space it's a little different. For one thing, there's no atmosphere or gravity, so the projectile behaves strangely. In low-Earth orbit, most of your bullets would eventually hit the atmosphere and burn up, though some would settle into a stable orbit. Some of these orbits would intercept yours, so you'd have be careful not to shoot yourself down. The rules of engagement are also completely different. Satellites circle the planet at high speeds, which makes it difficult to take on an enemy craft in a dog fight.

The simplest way to manoeuvre to within shooting distance is to intercept the satellite "in plane". In other words, approach it from behind in a lower and faster orbit and then boost yourself into its path. From the target's point of view, an attack craft would close in from behind and below, and the final few hundred metres of approach would be almost a straight line.

At this moment a burst of cannon fire would be lethal. The impact would cause a shock wave in the satellite's structure, pulverising its electronic equipment, shattering the glass in viewports and solar panels, and cracking open pressurised propellant tubes. A hit to a compartment containing oxygen could start a fire and incinerate the contents. But in the vacuum of space there would be no billowing Star Wars explosions or shock rings, just an eerie silence and tumbling, twinkling space confetti.

The victorious craft would then have to avoid the wreckage. Shooting down a satellite isn't like shooting down an aeroplane, where the engine or wings are so badly damaged that it falls out of the sky. Dead satellites continue to circle the Earth. The same goes for bits of shrapnel.

Debris isn't just a short-term problem. It can stay in orbit for years. Soviet ASAT tests in the late 1960s left behind a dozen clouds of metallic shards which are still a hazard today. The fragments are too small to track and too numerous to dodge, so all space vehicles have to be armoured against them.

For this reason, the US is reluctant to start shooting at things in orbit. After the recent war game, General Ralph Eberhart, commander-in-chief of US Space Command, told reporters he considered it a last-ditch option. But that's not to say space war has been ruled out. In the next couple of decades, projectiles are likely to be replaced by electromagnetic cannons, lasers and particle beams--high-tech weaponry capable of inflicting damage without creating debris.

Electromagnetic cannons are well developed (New Scientist, 1 July 2000, p 20) and are probably closest to being deployed in space. They fire intense bursts of radio waves at their target, jamming or destroying its electronics. At close range, they could permanently cripple a satellite's circuitry. At greater distances their power may only be enough to temporarily paralyse circuits.

Prototype cannons have already been built and tested. The two main types are the high-power microwave (HPM) system and the ultra-wide-band (UWB) system. HPM weapons fire a narrow and powerful beam of high-frequency radiation which can pierce a satellite's armour and fry its circuitry. The UWB beam is more of a scattergun weapon, with a broad beam and wide frequency range designed to knock out any electronic equipment in the vicinity.

Laser weapons dump large amounts of energy onto the satellite's surface, causing violent thermal expansion and setting up shock waves that tear components from the interior walls. People who've seen the damage inflicted by laser weapons say the effect is like a shotgun blast at point-blank range. So far lasers have only been used for rangefinding and guidance, but prototype weapons exist. And if President Bush goes ahead with his plan to revive "Star Wars", they could be in space very soon.

For the past 15 years, the US military has been experimenting with lasers at a test facility in White Sands, New Mexico. This is the home of MIRACL (the mid-infrared advanced chemical laser), a powerful deuterium fluoride laser built about 20 years ago for ships, then transferred to White Sands in the mid-1980s to study its anti-satellite capabilities. In October 1997, MIRACL was test fired into space. Although not powerful enough to vaporise a satellite, most experts believe that MIRACL could disable optical equipment and damage solar arrays and other delicate structures. There are some problems with atmospheric interference, but putting the laser into orbit would solve those.

Particle-beam weapons inflict damage in a similar way. They emit beams of particles, perhaps hydrogen or deuterium ions, at near-light speed. Details remain sketchy, but the principle is essentially the same as in an ion-propulsion system (New Scientist, 21 November 1998, p 22). A working particle beam is believed to have been on board the mysterious Soviet "battlestar" Polyus-Skif, which was launched in May 1987 but crashed during take-off. Polyus-Skif also carried a prototype laser for destroying satellites. In the US, research on particle-beam weapons continues at the High Energy Research and Technology Facility on Kirtland Air Force Base, New Mexico.

It all sounds depressingly familiar. Humans have only been using space for the past 50 years, yet we're already preparing to fight over it. And having concluded that our present weapons are too messy, we're building better ones. There's even the spectre of nuclear arms in space. For rogue states, the threat of a nuclear detonation in orbit would be a powerful bargaining chip.

But maybe there's an upside. Space is a long way off, and a war fought there by remote control would be all but invisible and harmless to those on the ground. Way above your head, right now, two nations could be settling their differences in space. You'd never even need to know.

James Oberg is a space writer and a former space flight engineer based in Houston, Texas. His new book, Space Power Theory, can be downloaded at http://www.jamesoberg.com/books/spt/spt.html

From New Scientist magazine, 02 June 2001.