The Attached Pressurised Module (APM) is the European element of the NASA Space Station Freedom (SSF). The environmental control of the APM is obtained through the combined effort of the Water Loops of the Thermal Control Subsystem (TCS) and the Cabin and Avionics Loops of the Environmental Control and Life Support Subsystem (ECLSS). Although the specific functions of ECLSS and TCS are separately verified at subsystem (S/S) level, their overall qualification is completed only after having carried out the functional and performance verification of the integrated Environmental Control System (ECS) inside the APM. To this purpose too, an APM Engineering Model (EM) development has been included in the programme.
The Engineering Model is the element prototype, fully representative of the APM Flight Model (FM) but for the quality of the EEE components, as they are requested to be MIL-grade but not Hi-Rel.
Due to the unavailability of adequate environmental facilities, thermal vacuum tests will not be run on the APM. In accordance with the NASA SSF programme guidelines, an analytical approach will be applied. The results of the development and qualification tests to be performed in ambient conditions on the ECS, on its separated subsystems and on it as integrated into the European module, will be taken and correlated to the predicted flight environment. On their side, the above tests will be supported by detailed test predictions.
The validation of the Thermal Mathematical Model will be achieved via test prediction analysis against test results, and post-test correlation. Methods of simulation of the SSF supporting functions related to the subject are also illustrated.
The test approach selected for the ECS on the APM is herein detailed. Its basic peculiarity is that while the ECLSS is tested, at the Subcontractor site, as an integrated subsystem by using load simulators and a boiler plate, the TCS is tested as an integrated EM subsystem only after APM EM integration completion. This because Alenia Spazio in-house development activity of the TCS at subsystem level provides sufficient confidence to allow its functional and performance qualification with a dedicated test on the element EM. Moreover, the actual external interfaces of the subsystem provide realistic boundary conditions, without reduction of testing capability.
On completion of the verification test on the ECS, an Integrated System Test will be carried out, including the combined verification of the ECLSS and TCS as a complete ECS, in terms of functions, performances, interfaces. This will take into account the operational constraints and the foreseen failure cases.