The qualification static load testing of Vega Interstage 1/2 was successfully completed during February and March 2006. The Interstage 1/2, designed and manufactured by Dutch Space, is part of the small launcher Vega for which ELV is Industrial Architect and Prime Contractor. The Interstage 1/2 is assembled by Dutch Space in Leiden where also the equipments, cable harnesses and thermal protection are integrated, so that it can be shipped directly to Kourou as a completely integrated sub-system.
Vega Interstage 1/2 Qualification Static Load Test at TNO. The green parts are test adapter parts, the metallic cone is the actual interstage.
Qualification testing was carried out at TNO Environment and Geosciences facilities in Delft.
The Test Readiness Review was held on 12th January and resulted in a go-ahead to test. The first test run was made on the 17th with the application of an axial compressive load of 410 tons. Thereafter, the test article was reconfigured and eccentric loads, representing launcher thrust and bending, were applied up to yield and ultimate levels. The Interstage 1/2 creaked as loads redistributed but the structure survived, producing beautifully linear characteristics and virtually no hysteresis in the force/strain plots.
The design of Interstage 1/2 posed many challenges for the Vega team. Firstly, Vega must offer a substantial reduction in launch costs, therefore recurring cost is a major design driver. Then there are very stringent requirements for the axial and bending stiffnesses of the Interstage 1/2, and last but not least, the structure must be able to withstand the launch loads. The toughest requirement to meet has been stiffness and this, with low recurring cost, has led to the choice of a monocoque structure for the Interstage 1/2. A thick-skinned (6.3mm) monocoque meets the stiffness requirements and offers lower production costs but has the disadvantage that it compromises strength and is more prone to general buckling than a shell structure with integral stiffeners. For this reason considerable emphasis was placed on buckling and strength analyses, both to reduce risk of structural failure but also to reach an optimum design for stiffness against mass. At the same time, considerable attention was given to the development of a structure which is economical to produce.
Vega Interstage 1/2 Model
This test by no means finished the Vega Interstage 1/2 project, but indicated that a major milestone was reached. No major technical problems were encountered during assembly of the Qualification Model test article and preliminary evaluation of the qualification test results shows that all stiffness and strength requirements are satisfied.
