Double-walled tube segment suitable for underpressure applications or near vacuum applications comprising elongated curved outer shell parts, interlayer shell parts and an inner wall, wherein - the elongated curved outer shell parts form the outer wall of the double-walled tube segment and consist of thin sheet, wherein the elongated curved outer shell part comprises a curved central portion and a flange along one of the long edges (3b, 3c) wherein the flange is folded towards the interior of the double-walled tube segment and wherein the centre of the radius of curvature R of the elongated curved outer shell parts lies inside the double-walled tube segment; - wherein the interlayer shell parts consist of thin sheet and comprise a rectangular portion having short edges (4b, 4c) and long edges (4f, 4g) and a flange on at least one of the short edges (4b, 4c), wherein the flange is folded towards the exterior of the double-walled tube segment, wherein the flange has a curved upper edge with the same radius of curvature as the radius of curvature of the curved central portion of the elongated curved outer shell parts, and wherein the curved edge is provided with an additional flange with the same radius of curvature as the radius of curvature of the curved central portion of the elongated curved outer shell parts; - wherein the inner wall of the double-walled tube segment is a regular N-facetted polygonal tube consisting of thin sheet; - wherein the rectangular portions of the interlayer shell parts are fixedly connected to the facets of the outside of the IW; - wherein the inner surface of the curved central portion of the elongated curved outer shell parts are joined to the interlayer shell parts at least at the additional flange of the interlayer shell part to form the outer wall. - the elongated curved outer shell parts form the outer wall of the double-walled tube segment and consist of thin sheet, wherein the elongated curved outer shell part comprises a curved central portion and a flange along one of the long edges (3b, 3c) wherein the flange is folded towards the interior of the double-walled tube segment and wherein the centre of the radius of curvature R of the elongated curved outer shell parts lies inside the double-walled tube segment; - wherein the interlayer shell parts consist of thin sheet and comprise a rectangular portion having short edges (4b, 4c) and long edges (4f, 4g) and a flange on at least one of the short edges (4b, 4c), wherein the flange is folded towards the exterior of the double-walled tube segment, wherein the flange has a curved upper edge with the same radius of curvature as the radius of curvature of the curved central portion of the elongated curved outer shell parts, and wherein the curved edge is provided with an additional flange with the same radius of curvature as the radius of curvature of the curved central portion of the elongated curved outer shell parts; - wherein the inner wall of the double-walled tube segment is a regular N-facetted polygonal tube consisting of thin sheet; - wherein the rectangular portions of the interlayer shell parts are fixedly connected to the facets of the outside of the IW; - wherein the inner surface of the curved central portion of the elongated curved outer shell parts are joined to the interlayer shell parts at least at the additional flange of the interlayer shell part to form the outer wall.