Ablative armor is meant to sacrificed to block an incoming attack. In contrast to current armors that are of a uniform thickness all around the armored vehicle, an advanced ablative armor would anticipate imminent attacks and concentrate its mass appropriately. Because of this futuristic quality, ablative armor is seen more frequently in science fiction scenarios than in real world militaries. However, as conventional weapons become obsolete at the expense of more advanced energy weapons, ablative armor will become very useful. For example, certain reentry vehicles use ablative armor to protect them from the extreme heat of entering earth’s atmosphere.
To serve their purpose optimally, plates of ablative armor would need to be mobilized by some form of advanced robotics in order to be quickly placed in front of an attacker’s blast. Like all forms of armor, ablative armor would need to have strong intermolecular bonds for optimal energy absorption. Fullerene, an allotrope of carbon even more durable than diamond, would be ideal. Some fullerene arrangements would have dozens of times more stopping power than a similar quantity of steel.
Ablative armor would be especially valuable against beam and particle weapons, which might be designed to penetrate conventional armors and kill the occupants. Ablative armor would be useful in cosmic environments, where most of the battlefield is vacuum and clouds of vaporized armor would have a protective effect. There are two types of futuristic craft that could benefit from ablative armor. These are space colonies and relativistic starships.
Outer space is filled with all sorts of radiation, including powerful cosmic rays that are harmful to humans. Human beings cannot spend significant lengths of time in unshielded space habitats. If we want unaugmented humans to have the choice to live in space colonies when they become feasible, then we need to install the appropriate shielding. For large space colonies, ablative shields made of rock or water envelopes have been proposed.
Occupants of relativistic spacecraft, spaceships traveling at speeds close to that of light, would have to deal with the same radiation problems as space colony occupants, but multiplied many times over. Because relativistic spacecraft would be moving through space so fast, they would be certain to collide with large quantities of charged particles at much greater speeds. At velocities close to that of light, even a particle with tiny mass would carry an enormous momentum. Because of this, relativistic spacecraft traveling within galaxies would certainly need ablative armor. Outside of galactic clusters, matter may be sufficiently sparse that a spacecraft could travel close to the speed of light without impacting anything much.