High Density Expansion Tape is a damage control material used for sealing small to medium hull breaches. Issued in kits of several rolls, plus a staple gun/cutter combi-tool, most ships carry a kit in every compartment.

The tape is non-adhesive. It is placed across the inside of the breach, with the smooth side facing outwards, and stapled in place. Once secure, the combi-tool is used to grab an end of the activation cord running down the inner side of the tape. When the cord is pulled, a chemical reaction causes the compound on the smooth side of the tape to expand rapidly. The expanding foam quickly sets into a rigid, airtight structure, able to withstand pressurisation. A single piece of tape can fill up to 15cm on each side, meaning a gap of up to 30cm between pieces can result in a secure seal. It is recommended to apply cross-bracing tape to larger gaps to make the seal more resilient. HDET should be replaced with a permanent repair as soon as possible; the foam cannot withstand shocks and will degrade over about a week.

HDET kits can easily be applied by a single person, or a drone, even in zero gravity. Combined with their compact size and mass relative to coverage, this makes them an essential part of a ship’s damage control systems.

HDET is colloquially known as “red tape”….because it's red.