. "The Propulsion Gel is a testing element used in the Enrichment Center several decades before Portal, and appears in Portal 2. It is one of three types of Mobility Gels."@en . . "Aperture Science"@en . . . . "The Propulsion Gel is a testing element used in the Enrichment Center several decades before Portal, and appears in Portal 2. It is one of three types of Mobility Gels."@en . . . . . "*Chell\n*ATLAS and P-body"@en . . . . "Liquid fiberglass insulator"@en . "Propulsion Gel"@en . . . . . .