In Space Weapons, Earth Wars, what is the most accurate summary of what Preston and colleagues conclude about orbital lasers for BMD across altitudes?

• A. Orbital lasers would be ideal for attacking hardened targets in fixed locations, but they would not be able to hit moving targets as would be needed in BMD.
• B. BMD with orbital lasers would be impractical because we do not have space-lift boosters powerful enough to put such enormous satellites in orbit.
• C. A high-altitude orbital laser constellation would provide a nearly leak-proof defense against a salvo launch of missiles from North Korea.
• D. Regardless of altitude, such a system would provide only a very limited defense against ballistic missile attack.

Answer: (D)

The key idea is that placing lasers in space to defend against ballistic missiles doesn’t remove the fundamental hurdles in achieving a reliable shield. To actually stop a missile, the system must deliver lethal energy to a moving, fast-flying warhead within a very short intercept window, while also tracking multiple targets, distinguishing real warheads from decoys, and handling saturation from salvo launches. These challenges persist no matter what orbit the laser sits in.

If the laser is lower, the beam has to traverse more of Earth’s atmosphere, so turbulence and scattering degrade beam quality and energy delivery. If the laser is higher, the beam must travel a much greater distance, which dramatically increases the power and precision demands to maintain the same energy flux at the target. Either way, the logistics of power, optics, timing, and target discrimination remain formidable. Add the costs, maintenance, and vulnerability of a space-based system to countermeasures and counterattack, and the overall defense is inherently limited. That’s why the conclusion is that such a system would provide only a very limited defense, regardless of altitude.