Inherited from the European Automated Transfer Vehicle (ATV) program, the Orion Service Module will provide propulsion and primary life support functions for the American Orion vehicle. This is the first time that NASA has entrusted European industry with such important functions for the safety of its astronauts. Explanations from Dario Saia, Orion service module program manager at Thales Alenia Space.
After giving the floor to Antoine Alouani, propulsion system engineer atOrionOrion at Airbus, who made us discover the incredible complexity of the propulsion system of the service module made by Airbus with audacious design choices, it is the turn of Dario Saia.
This manager of the Orion service module program at Thales Alenia Space, who also contributes to its implementation under the responsibility of Airbus, reminds us that the ESM ” embeds technologies inherited from the ATV program of theEuropean Space AgencyEuropean Space Agency “. This module, which will provide propulsion, power supply, thermal control and vital components to the American capsule, is in the form of a cylindrical structure, ” of which the volumevolume internal is divided into different areas by dedicated panels, where the equipment for thermal control, consumables control, avionics, power and propulsion system are housed “.
The structure of the ESM also serves as a ” support for radiatorsradiatorssolar panels, main engine and thrustersthrusters auxiliaries, as well as all consumable and propulsion tanks “. As for the mechanical interfaces with the crew module and the spacecraft, they are located on the upper and lower faces respectively.
A service module inherited from the European ATV vehicle
The structure of the ESM is not built in steelsteel. Consisting of an assembly of composite parts in alloyalloy ofaluminumaluminum lightweight and carbon fiber (sparssparspanels, supports in aluminum and carbon fibers or in titanium), the massmass entire ESM structure — including fuel tank supports propellantpropellant and life support, radiators and ESM motors — is just over a ton (about 1,100 kgkg). Its size is about 4 meters in diameter for a height of 2.5 meters.
Although this propulsion module is inherited from the service module of theATVATV, it differs on several points. Unlike the ATV, which was a ” pressurized supply vehicle, intended to transport supplies for the ISS “, the ESM is based on a structure “ unpressurized with stringers, bulkheads and shear panels “. The ESM is designed to “ transport engines, propellant tanks, water and gasgasthermal control equipment, electronic equipment to support Orion’s journey and ensure the life of the astronauts aboard the capsule “. The structural design of the ESM is therefore ” optimized for this purpose and therefore does not have a pressurized compartment to be accessible to astronauts “.
“The ESM is designed to support Orion’s journey and ensure the life of the astronauts aboard the capsule”
This explains why it is so light, unlike the ATV whose empty weight was more than 10 tons – it was also taller at almost 10 meters compared to only 2.5 meters. Finally, unlike the ATV which evolved in low orbit inside the magnetospheremagnetospherethe ESM “ will travel beyond this magnetic bubble that protects us from the harmful effects of solar windsolar wind “. Its design takes this strong constraint into account.
Another difference, while the ATV was highly exposed to the risk of collision with space debris, the Orion vehicle will be significantly less so that its “ shield is very different from that of the ATV “.
Manned flights inseparable from European know-how
This module is designed to operate for at least 21 days in orbit. But he “ could support longer voyages, as is the case with this first mission whose durationduration is more than 25 days old “. The ESM is not just the propulsion module of the Orion vehicle. It is also a key element of human life on board as it embarge the reserves in nitrogennitrogen, airair and water necessary for the missions “. These primary resources are sized for “ ssupport a crew of four throughout the mission, they are stored in dedicated tanks and are distributed to the cabin on demand”.
To manage these consumables, Thales Alenia Space provides the control system that “ scontinuously monitors to provide information on the quantities of resources available and the levels of pressurepressure and temperature. It is linked to the ESM command center, in order to be operated remotely and configurable as needed during the different phases of the mission. A number of valves help isolate any failure, ensuring resource availability for the cabin “.
This system is also responsible for provide breathable air to cabin crew by mixingoxygenoxygen (stored in three tanks) and nitrogen (stored in one tank) “. Air exhaust is controlled by regulatorsregulators of pressure and the different sections of the system can be isolated by gas shut-off valves for the purpose ofinsulationinsulation in case of failure. The mixture itself is controlled by valves located in the crew module. Nitrogen also pressurizes potable water stored in four tanks which is distributed to the crew module when needed.
For this first mission, the ESM module has a simplified control of consumables due to the absence of a crew. The number of gas tanks is therefore limited to “ only one filled with nitrogen, instead of the four tanks needed in manned spaceflight “. Mass simulators were therefore used to ” fill the missing tanks in order to maintain the same mass balance of the vehicle “. All water tanks are present but no water will be distributed to the crew made up of models.
Thales Alenia Space also provides the thermal control system (TCS) which has the function of reject the heat produced by the astronauts inside the crew module into space and to keep Orion warm despite the extreme temperatures of space.” This system is also used to reject thermal loads from Orion’s motorized equipment, both in the crew module and in the service module.. The heat generated is transferred by the crew module to the European service module via ” heat exchangers “. This thermal control system mainly consists of two parts, the active thermal control system and the passive thermal control system.