Why can’t we put a space cadet from the newly formed Space Force in the nose of the interceptor, and have him shoot at the warhead as he zooms by? Intuition fails us with the speeds and acceleration. The space cadet would be mashed flat in the high-g blast-off. The speed of his bullets is 1/10 the speed of the target, almost as slow as the mail.

The hit-to- kill vehicle  is  devastating in head-on collision. The energy delivered to the target is the kinetic energy of the vehicle,   much large than the energy of an explosive charge. Purity of the concept is of no concern,  so one of the ways to turn a miss into a hit is an explosive charge that fragments the kill vehicle in front of the warhead.  Another enhancement, workable only outside the atmosphere, is an extensible “cow catcher”.  Both replace the head-on collision with smaller but sufficient mass to break  the target. Aerodynamics and the heat of air friction do the rest.

What kind of fragment, or other small object, is sufficient to destroy a warhead just from being in the right place at the right time? At collision speed, the kinetic energy is about the same as equivalent weight of TNT. But our study so far has been amenable to napkin calculations because of the binary definition of success, hit or miss. Materials lack that certainty. We don’t theorize about tank armor versus penetrating round; we try it out. The behavior of materials in extreme conditions is an experimental science.

Space junk and micrometeorites pose a threat to satellites. Shielding is thought to be practical up to an asteroid size of 1 cm. The shield is a double wall. The first wall shatters the asteroid into smaller pieces that cannot penetrate the second wall. But an asteroid is not engineered material. The toughest asteroids are nodular iron, which isn’t very tough.  Most are chondrites, made of small grains cemented together by pressure. A shield may be effective against the bulk of satellite debris. But a  titanium bolt, left over from an anti-satellite missile test, is an engineered material, with far greater penetrating power than a clod of dirt.

The small chance of a  pure hit-to-kill against a maneuvering target might be improved by release of a cloud of small engineered objects, with sufficient density  to insure destructive impact. The calculation of Part 4 can be repeated with a “hit” expanded  to the vicinity implied by the size of the cloud. This is standard with anti-aircraft missiles. But aircraft are the ultimate soft targets. It doesn’t automatically imply destruction of a warhead hardened against reentry. We have to think about it.

If a pack of high-tech BB’s were released in front of a hypersonic vehicle, would destruction result? Unlike the hit-or miss proposition, it depends upon details: shape, material, thickness, internal structure, and warhead vulnerability at point of collision. The BB’s could be the densest, meanest BB’s imaginable, tungsten with a depleted uranium center, yet success is not assured.

If a BB craters the surface, or puts a hole in it, it could disrupt aerodynamic control, or cause local heating, leading to destruction. Some obstacles to success:

• As soon as the BB’s are released, they are blown backwards in the air stream, losing kinetic punch.
• A hypersonic warhead has sharply sloping sides. Like the sloping glacis of a armored tank, the impact energy is reduced by the sine of the impact angle.
• The properties of carbon fiber plastics, of which Avangard is said to be made, can be vexing, as the Russians have discovered. But they also offer complex opportunities for manipulation, of strength and cleavage properties that vary sharply with angle.

Once the rivalry gets going, Avangard, or other hypersonic vehicles, could be equipped with “spare parts.” If there’s a lucky shot to the tip of the nose, it falls off, revealing — another nose. Unlike the original missile race, the Russians have plenty of throw-weight, which can be diverted to armor Avangard, and descendants, against threat.

A counter to plastic armor could be an ingeniously engineered micro-projectile.  A pointed shape, concentrating impact force, might be stabilized in the right orientation by a dispenser that imparts spin, or by a magnetic pulse.

Suppose we pass over the idea of a penetrating BB in favor of gumballs.  I’ve spent my life scraping these things off my shoes.  A gumball is a projectile with a soft core,  still very massive, to resist the aerodynamic forces of the slipstream.

When it hits Avangard, the gumball goes “splat!”, and  the soft, chewy core sticks on it, quickly setting to an adherent, thermally conductive ceramic. This disrupts the crucial thermal balance of the surface. Frictional heating does the rest, burning a hole, or causing thermal-mechanical stress fracture, a virtual guarantee of destruction.

Without frequent access to a test article, ie., a stolen Avangard, we’re working in the dark. But it is at least conceivable that a micro-projectile could,  by a chain of effects, be as damaging as a direct hit.

Next: Beyond kinetics: directed energy, nukes, and hybrids.