Christopher Stone, “a space/missile officer with Air Force Space Command-Reserve Component”, has written an article in the Space Review blaming “certain circles” and “political” reasons for the lack of orbital strike weapons.

Stone omitted, as a reason, the laws of physics, which presumably also hate our freedoms.

Fortunately, David Wright and Laura Grego have penned a response elucidating those relevant laws:

Briefly, for a space-based weapon to be able to reach a ground target rapidly, it must be positioned close to the ground, in low Earth orbit (LEO) at an altitude of several hundred kilometers. However, satellites in LEO move quickly with respect to the ground, and to ensure that one is in the right place at the right time, a constellation of many satellites would be necessary. Timeliness and number of satellites required play off of each other, but to be competitive with ground-based systems and have a response time of about 30 minutes, one would need some 100 satellites in orbit. Those 100 would provide for a single satellite to cover a target; to have two-on-one targeting or allow two nearly simultaneous attacks on nearby targets would require doubling the size of the constellation, and so on.

While Mr. Stone correctly notes that three satellites in geostationary orbits (GEO) can view the entire equatorial regions of the earth, GEO satellites are 100 times farther from the earth than LEO satellites—much too far to be able to strike the ground rapidly. In reality, space is already used for those tasks it is best suited to, and not those it isn’t. Basic physics dictates this.

Moreover, the intuitive appeal that bombing from space has for many people—that weapons can be “dropped” from above a target—is simply wrong. Objects in orbit stay in orbit unless there is a force to push them back toward the ground. Not only do orbiting ground-attack weapons require a large rocket to get them into space in the first place, they must carry large amounts of fuel (essentially another rocket) to accelerate them back out of their orbit and down to earth. Since launching mass into orbit costs oughly $10,000 per pound, such a constellation becomes very expensive. Moreover, since the weapons and their rockets are orbiting in space for years, reliability becomes a concern.

David and Laura were much more moderate in tone that I was, after Taylor Dinerman incorrectly reasoned that intercepting a missile in the boost phase would cause the warhead to “fall back on the nation that launched the missile”.

For the full scoop of orbital strike weapons and other flights of fancy, check out Wright, Grego and Gronlund, The Physics of Space Security.

Late Update: I overlooked a great report by the late Bob Preston and his colleagues at RAND.