Thermal and Environmental Control of the Crew Transport Vehicle 972314
Following the objectives of the European Space Agency, specific studies have been performed concerning a Crew Transport Vehicle (CTV) based on the Ariane 5 launcher. This vehicle is designed to transport a maximum crew of 4 members to/from the International Space Station, with a limited amount of payloads. It is mainly composed of:
Crew Module (CM), capable of withstanding the severe environmental conditions of the atmospheric re-entry, offering an adequate habitable environment for the crew all mission time long.
Resource Module (RM), where most of provisions and electrical equipment (e.g. batteries) supporting the vehicle orbital life is stored; the truncated cone shape external surface of RM is entirely exploited for mounting dedicated fluid radiators.
Transfer Vehicle (TV), a propulsion module designed to supply means and resources for the vehicle orbital manoeuvres and attitude control from launcher separation up to de-orbitation, when the RM + TV composite is jettisoned.
The thermal control of the CTV requires the adoption of technical solutions compatible with extremely different environmental conditions (ranging from the cold boundaries of orbital exposure to the high aerothermal fluxes during re-entry) and various operational modes (the vehicle is fully active in free-flying phases, but it is in dormant mode when ISSA docked, with most of equipment switched off). Temperature and humidity in the habitable compartment are controlled by a dedicated section of the Environmental Control and Life Support Subsystem. An air loop is designed to collect the cabin heat loads due to crew metabolism, external environment and part of the spacionics dissipation. These loads are then transferred via a Condensing Heat Exchanger to a couple of hot redundant water loops (Active Section of Thermal Control Subsystem) which also receive the thermal power released by the electronic equipment mounted on cold plates. The resulting global heat loads are transported to the available heat sinks, which may be different depending on the various mission phases. During ascent and re-entry, waste heat dissipated by means of evaporators and / or managed through the vehicle thermal capacitance. In orbital conditions a set of radiators, connected to a low freezing temperature coolant loop, provides the necessary rejection to space. Passive thermal control provisions are complementarily adopted, including Multilayer insulation, foam blankets and heaters.
The major design features of the CTV Thermal Control are highlighted, taking into account the interface subsystems (e.g. Electrical Power Supply, DMS / GNC, Thermal Protection), the mission timeline, and the constraints related to the failure tolerance criteria adopted.