served as experimental reentry vehicle primarily for technology-proving and data-gathering purposes. In terms of its shape, the vehicle bares an external resemblance to a 70 per cent-scale version of the American Apollo capsule, and considered by the ESA to be a 50 per cent-scale vehicle of a prospective potentially operational transportation vehicle; as such, it is 2.8 meters in diameter and weighs 2.8 tons at atmospheric interface point. The ARD possesses an air- and water-tight pressurised structure primarily composed of an aluminium alloy, which is protected by a layer of Norcoat 62250 FI cork composite tiles across the exterior of nosecone and by an arrangement of aleastrasil silicon dioxide-phenol formaldehyde resin tiles over the heat shield. The vehicle itself can be divided into three distinct sections: the frontshield section, the rear-cone section and the backcover section. The ARD possesses manoeuvrability capabilities during re-entry; a favourable lift-to-drag ratio is achieved via an off-set center of gravity. The guidance law is akin to that of Apollo and the Space Shuttle, being based on a drag-velocity profile control and bank angles manoeuvres in order to conform with heating, load factor, rebound, and other required conditions; according to the ESA, this provided acceptable final guidance accuracy (within 5 km) with limited real-time calculation complexity. In operation, the guidance system becomes active once the aerodynamic forces become efficient and as long as the reaction control system remains efficient. Instead of using flight control surfaces, non-linear control is instead ensured by an assortment of seven hydrazine thrusters which, according to the manufacturer, were derived from the Ariane 5 expendable launch system. These rocket thrusters, each typically generating 400-N of thrust, were arranged in a blow-down configuration and positioned so that three units provide pitch control, two for roll and two for yaw. During its reentry into the atmosphere, the ARD's heat shield is exposed to temperatures reaching as high as 2000 °C and a heat flux peaking at 1000 kW/m2, resulting from the ionisation of the atmosphere, which is in turn caused by the vehicle travelling at hypersonic speeds, in excess of 27,000 km/h during parts of its reentry descent. While the conical area of the vehicle may reach 1000 °C, with a heat flux of 90–125 kW/m2, the interior temperature will not rise above 40 °C. The thermal protection measures used were a combination of pre-existing materials that Aerospatiale had already developed under French military