Can Space Weapons Protect U.S. Satellites?

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Can Space Weapons Protect U.S. Satellites?

By Yousaf Butt

Bulletin of the Atomic Scientists

22 July 2008

http://thebulletin.org/web-edition/features/can-space-weapons-protect-us-satellites

Both presumptive presidential nominees-- Arizona

Republican Sen. John McCain and Illinois Democratic Sen.

Barack Obama--have called for strengthening and/or

increasing the number of international treaties and

institutions to combat proliferation should they be

elected president. An important new pact for them to

consider is an agreement that restricts the

weaponization of space. Not only are space weapons

expensive and provocative, they're also useless: They

simply cannot protect us.

Over the years, many voices in Washington have called

for green-lighting space weapons as a way of

neutralizing the threat to U.S. satellites. For

instance, the 2001 U.S. Space Commission report warned

against a "Space Pearl Harbor " and advocated that, "The

[ United States ] must develop the means both to deter and

to defend against hostile acts in and from space." It

went further to suggest that the Defense Department

"vigorously pursue the capabilities . . . to ensure that

the president will have the options to deploy weapons in space."

Throughout this debate, it's almost taken as an article

of faith that space weapons can be defensively useful.

Yet, there's little technical basis to support this

belief: While certainly offensively potent, space

weapons are defensively ineffective.

First, let me be clear about what I mean by the term

"space weapons." In my definition, I include any weapons

based in space that can attack targets either in space

or on the ground or any land-, sea-, or air-based

weapons that can attack satellites.(1)

Fragile, blind, unmanned satellites are different from

armored and actively piloted tanks, ships, and airplanes

because they move in predictable orbits without

situational awareness of their surroundings, providing

an easy target for an enemy bent on interfering or

destroying them. To save on launch costs, they're

typically built as light as possible with minimal

shielding. And the few evasive actions they can take

greatly sap the limited onboard fuel.

The most optimistic incarnation of a defensive space

weapon is the so-called "bodyguard satellite," which is

designed to protect satellites from ground-based

antisatellite (ASAT) weapons. The bodyguard would shadow

the high-value satellite it's protecting by being in an

identical orbit, typically trailing its "boss" by a few

hundred kilometers. Once cued to a threat, it could

launch an interceptor to impact and destroy the incoming

ASAT kill vehicle. A single bodyguard satellite system

that could intercept an incoming ASAT would have a mass

of about 500 to 1,500 kilograms, including the necessary

housing, solar panels, batteries, station-keeping fuel,

and communication and sensor subsystems.

The problem is that a single bodyguard satellite would

be insufficient to guard its "boss." Even if the

bodyguard successfully intercepted an incoming ASAT, the

adversary could simply try again on a successive orbit--

the so-called "limited magazine" problem. Of course, a

satellite could possess multiple bodyguard satellites,

but the launch costs alone (about $15,000 per kilogram

of payload) quickly become prohibitive for multiple

bodyguards weighing about 1,000 kilograms each in orbit.

At some point, the cost of having many bodyguard

satellites exceeds that of the satellite being

protected. It then makes more sense to simply have a

backup redundant satellite ready to launch rather than

multiple defensive space weapons.

More problematic still is the fact that the attacker can

use simple countermeasures such as decoys and flares to

fool the bodyguard's interceptor. This is the same

reason why ballistic missile defense also doesn't make sense.

Directed-energy weapons such as lasers may be available

in the future, but they run on chemicals as the source

of the laser energy, which also are subject to the

limited magazine problem if the laser is in orbit. And

if the laser is ground-based, its range of lethality is

limited to a small fraction of the globe in the ground-

station's vicinity. Furthermore, ground-based systems

must use complicated and expensive adaptive optics to

compensate for the natural broadening and dimming of the

laser light as it traverses the atmosphere, something

that has not yet been publicly demonstrated over

hundreds of kilometers for a high-power laser. Of

course, the laser ground stations are hostage to

conventional ground attack, and, more prosaically, cloud cover.

Thus, the much feared "Space Pearl Harbor " can happen

with or without space weapons, as they provide little,

if any, effective defense. In fact, introducing weapons

into space that are offensively potent yet defensively

ineffective may actually make a "Space Pearl Harbor "

more imminent. In the eyes of potential adversaries, the

only distinction between defensive and offensive space

weapons would be the unknowable intention behind their

use. A bodyguard satellite, for instance, could easily

be reconfigured to attack other satellites instead of

defending against incoming ASATs.

Fielding offensive space weapons for the sake of

deterrence also doesn't make sense because the United

States relies much more heavily on its satellites than

any of its adversaries. A better way to deter attacks on

U.S. satellites would be for Washington to make clear

that any attack on its space assets would be considered

an attack on U.S. soil and result in a heavy

conventional retaliatory attack.

Ultimately, the protection of the capabilities

facilitated by space assets is needed. For instance,

having a fiber-optic backup system for certain high-

value communication satellites is much smarter than

maintaining many expensive, ineffective bodyguard

satellites. Alternate redundant non-space systems,

whenever possible, are the smartest defense. The United

States could also have redundant satellites ready to

replace any losses in those satellites for which no

land-based backups exist. Temporary and reversible

electronic countermeasures that could throw off the

guidance systems of incoming ASATs are another sensible

defense. Better "Space Situational Awareness" is also

badly needed, if for nothing else, than to properly tell

apart a satellite attack from a satellite malfunction or

natural interference such as a strong solar flare or debris impact.

Most importantly, the United States should be leading

the charge to have an overarching international policy

that restricts the weaponization of space. The United

States possesses the greatest military and civil space

investment; thus, it has the most to lose in an

offensive space war. And since Washington is the most

reliant on its space assets, an arms race in space would

be disproportionately detrimental to U.S. interests.

Instead of relying upon expensive, provocative, and

defensively useless space weapons, the incoming

administration would do well to invest in any of the

other approaches listed above to improve our space security.

(1) Although exo-atmospheric ballistic missile defense

(BMD) interceptors constitute de facto space weapons

under this definition, a treaty restricting space

weaponization would have to go beyond simple

definitions. For instance, while compartmentalizing and

allowing BMD, it may still specifically restrict the use

of BMD interceptors against satellites. There's an

important interplay between definitions, prohibitions,

and verification methods for any sound set of rules to

obtain space security, and this is something that will

have to be negotiated carefully.