Reaction cube

The reaction cube, also called the spore cube, was a test chamber aboard Crossfield-class starships. On the USS Discovery it was located in the engineering test bay alpha. (DIS: "Context Is for Kings")

On both the Discovery and the USS Glenn, the reaction cube was used to introduce mycelium spores from Prototaxites stellaviatori to a living host as part of the experimental spore drive.

Before the spore drive was perfected, Captain Gabriel Lorca explained to Michael Burnham the concepts behind the mycelial network by injecting mycelial spores into the reaction cube while she was standing inside of it, showing her different locations across the galaxy. (DIS: "Context Is for Kings")

Burnham and Paul Stamets later determined that the Glenn's spore drive was experimenting with using a tardigrade in the reaction cube to guide the spore drive's navigation. (DIS: "The Butcher's Knife Cares Not for the Lamb's Cry")

The reaction cube was the only place on a spore drive-equipped ship where the mycelial barrier could be safely contacted. (DIS: "Saints of Imperfection")

The spore cube could be magnetized, a fact that was used to great effect to neutralize Leland after he was made an agent of Control. (DIS: "Such Sweet Sorrow, Part 2")

In 3189 as part of the Discovery's refit at Federation Headquarters, Adira Tal designed and implemented an upgrade to the control injectors of the reaction cube, replacing them with nanogel control surfaces making it more efficient and comfortable for Stamets. The Kwejian Courier, Cleveland Booker, was able to use the cube to communicate with the spores. This allowed Discovery to escape from inside the Viridian before its destruction. (DIS: "Scavengers", "That Hope Is You, Part 2")

While escaping from one of Species 10-C's orbs, the spore drive was burned out and, as result, the reaction cube shattered. (DIS: "Coming Home")