Problems With Orbit
Space-based weapon systems suffer from the same problem as any object in orbit. They can't swoop about like a TIE bomber in Star Wars. Orbital mechanics and environment impose restrictions that are utterly ignored by this article, including:
- Satellites can't hide. Every rocket launch can be tracked, and every payload of sufficient size can be followed. A Rods of God system, which could be the size of a school bus, can be tracked in a good scope-dope's sleep.
- Satellites fly predictable paths. Because they have limited onboard fuel, and because of high traffic, satellites limit maneuvers to station-keeping and dodging space junk. A rival could purchase basic flight maps of enemy satellites, then use dead reckoning techniques to anticipate when and where that Kinetic Bombardment platform is overhead.
- Due to limited maneuverability, Rods from God platforms will also need to ride higher orbits: to avoid ground based anti-satellite missiles, to avoid orbital denial conditions (such as the growing volume of space junk in lower orbits), and to hide from less sophisticated trackers. This increases the flight time of the projectiles.
And that leads me to...
Problems With De-Orbit
Orbital based projectiles are subject to the same laws of physics as meteorites, space capsules and shuttles. One can't just "drop" them or "nudge them" straight down.
- A successful, direct insertion will require burns, requiring a larger and more complicated launch assembly producing a visible infrared signatures (IR). This is hypothetically easier to detect than an ICBM, because ballistic missiles mainly ignite in the ascent, where they can be partially cloaked by various atmospheric effects on the horizon. Missiles may also be able to spoof as civilian rockets. Finally, ICBMs typically coast by the time they reach apogee, whereas a Rod from God is firing away at apogee for the whole hemisphere to see.
- Note that this maneuver is simply to overcome angular momentum and set course. The projectile may lose velocity to atmospheric drag. This means the projectile will need to accommodate aerodynamic controls to correct drift and speed.
- Hull ionization will also generate an IR streak in space. A big hail of steel and tungsten, as described, would also likely appear on magnetic anomaly detectors. Don't forget that an ionization bloom can be picked on radar, too. Under certain conditions and altitudes, this ionization may actually scatter radio waves and thus reduce radar contact--but I think it is more likely to be quite visible.
- Finally Rods from God will take much longer to reach the surface than it's starry eyed proponents propose. Remember, they have to be released from an orbit considerably higher than an ICBM--because you gotta protect your launch platform from anti-sat missiles, space junk, casual observation, and orbital decay. It could take roughly 10 to 45 minutes to descend to the surface, depending on the insertion method.
Overall, the article is quite wrong in asserting that Rods from God will be less detectable than that of an ICBM. It will actually be greater, due to the combination of a exposed altitude, sustained burn, and sustained descent signature. Then of course, there's the separate problem of the lower atmosphere...
Problems With Terminal Descent
You know, the stuff we breathe? The stuff that burns up meteorites, space shuttles, and hypersonic test drones? To maintain the velocity discussed by many novelists and theorists--to hit at specific bunker at Mach 25--is to introduce all sorts of aerodynamic complexities:
- The least of which may be even more rocket burns to counteract drag and shear. In general, a projectile will need some sort of flight control system or it will go off course--especially if the target is moving. Perhaps it can be integrated, but this still means increased bulk, cost, and complexity of the system.
- All of which has to be shielded from the friction generated by the atmosphere at the proposed speeds! Remember, we are talking about a hypersonic kill vehicle here, and it is notoriously difficult and expensive to get anything to travel faster than about Mach 3 in the Troposphere without dispersing into a less destructive and accurate cloud of debris. The density of the stratosphere, too, might possibly shatter a space-born projectile travelling at orbital velocity.
- Fortunately, a projectile does not need to be traveling at orbital velocity to make a big impact. A dense or massive projectile could transfer enough energy at about 3 kilometers per second to effect a kinetic strike. All this crap about orbital velocity is just that. Needless complication of an already complex weapon.
Problems With Fire Control
Finally, such a projectile is not going to be self-guided as Jerry Pournelle and other authors like to imagine. Such a sensor:
A) has to be covered by the aforementioned heat/friction shield, B) or it will be ablated by the friction of re-entry in the lower atmospher, unless it is made out of some exotic material. C) or will obscured by the ionization of re-entry for the duration of the descent.
The idea of dropping a bunch of "crowbars" from 300 to 600 km and trying to shower an armored column strikes me as wishful thinking, especially if that column is moving and spaced like all modern formations should be. It made for an exciting scene in Pournelle's
Footfall, but hardly likely. Even if it does work, it would be a hell of a lot more expensive than to deploy a few attack planes or long-range guided missiles. If America ever loses the air edge to the point that we need Orbital Strikes to stop a tank battalion, we are in El Deep Shito.
Such a projectile will require range safety devices. Because the cross-range of an orbital projectile might be severe compared to an ordinary bomb, it will need measures comparable to that of an ICBM or at least a cruise missile. If the Chinese are pissed about one embassy accidentally bombed in Yugoslavia, imagine an entire neighborhood wiped out by a stack of telephone poles. More expense. More complexity. More mass.
Problems of Cost
Everything thus far means money, time, and resources. Tungsten is not that cheap or readily available, even if it is relatively stable in re-entry. A single bundle of telephone poles could consume enough tungsten to armor a dozen tanks, or to form hundreds of cannon shells. And they will not necessarily be cheaper per unit, nor more cost-effective in combat. You have to de-orbit, shield, propel, and correct a dumb projectile as much as a smart one.
Conclusion
I don't know for sure that all of these problems are severe, or even likely, and that's part of the problem too--people aren't considering the challenges. You don't have to be an engineer or a weaponeer to see unanswered questions and basic physical challenges.