Sealing Technologies Trade-off for a Phobos Sample Return Mission

The Phobos Sample Return Mission (PhSR) is a phase of the Mars Robotic Exploration Preparation program, with the main objective to acquire and return 100 grams of Phobos soil (regolith) on Earth. First, a complete surface map with topographic and mineralogical information will be obtained by the spacecraft. After a successful sampling, an ERV containing the ERC with the regolith sample will head back to the Earth. Following touch-down, the ERC will be retrieved and opened in a dedicated environment. Given the importance and value of such return sample, it must be well protected between the moments when the ERC is closed on Phobos after the sampling operation until landing on Earth surface. Thus, a special containment system is necessary, capable of withstanding the harsh space environment and the mechanical stress occurred during the mission, while preserving the integrity of the regolith sample. Following previous sampling missions (Hayabusa, Stardust) and the problems raised by the contamination, one can say that the sealing system is probably the most important part of a sample containment system, as it shall protect the sample from Earth contaminants, but also to protect the Earth against possible micro-organisms or other hazardous substances found in space. This paper aims to analyse a variety of sealing technologies with importance in space applications like a sample return mission, measuring qualitatively and quantitatively the performance of a sealing technology when it comes to fulfilling a series of requirements imposed by the sample return mission profile. Using these requirements and mission data as inputs, a trade-off analysis was made, to identify the most suitable sealing technology for a PhSR Mission. It was concluded that sealing technologies such as O-rings and Gaskets can be successfully used in these kind of missions, paying also attention to a proper design of the containment system.