New space debris mitigation guidelines require satellites in low Earth orbit to de-orbit within 25 years after end of life. This effectively limits the orbital altitude of conventional CubeSat satellites to 400-700 km. For CubeSats employing the generic inflatable de-orbit device discussed here, this range is extended to 910 km by increasing the frontal surface area of the satellite. The device essentially is of the attached ballute type and consists of a thin membrane covering an inflatable structure, which is chemically rigidized after deployment. Coatings are applied to the structure to provide protection against the hostile low Earth orbit environment and to manipulate the temperature of the inflatable. The inflation gas is stored in solid form inside a so-called Cool Gas Generator. A preliminary design of the pyramid-shaped device is performed for a 1-unit CubeSat of 1 kg mass, with focus on ease of integration. Initial results of the physical development of the structure are shown. A development model of a flexible connector piece is constructed to which five inflatable tubes are attached at right angles in a leak-tight manner. The method used to bond the tubes to the connector piece as well as attachment of the membranes to the inflatable structure is outlined. Lastly, stowage and deployment of the inflatable structure are discussed. The results indicate that the mass and stowed volume of the complete de-orbit system remain within 9.4% and 10.3% of the CubeSats' total mass and volume.