Stealth ablative coating

Stealth Ablative Coating is a material found on UNSC stealth ships. Black in color, Stealth Ablative coating serves to refract both UNSC radar and Covenant sensors, making the ship invisible to radar, similar to the way Active Camo cloaks something from eyesight.

Stealth Ablative Coating must be maintained perfectly, otherwise it will return radar signals, necessitating constant maintenance on the entire coating. Therefore, virtually all UNSC Prowlers are relatively small, so that less has to be maintained. An exception to this is the UNSC Point of No Return, which is a prowler the size of a UNSC Destroyer.

Stealth Ablative Coating can be found on Long Range Stealth Orbital Insertion Pods as well as all UNSC Prowlers.

Strictly speaking, an ablative armor is designed to prevent damage to a ship it covers by being damaged itself through the process of ablation. A stealth ablative coating would therefore mean that once damage has been taken, its stealth features would be useless.

Trivia

 * In real life there are stealth bombers that use this exact same technology. They achieve radar invisibility due to refractive paint which, also, must be repainted every time.