Comparing Trash Disposal to Use as Radiation Shielding for a Mars Transit Vehicle

A round trip to Mars will require lots of supplies and will generate lots of trash. Mission studies and technology development are underway for this and other human space exploration missions, and what to do with the trash is more than a casual question. Supplies regularly come to the International Space Station in a variety of visiting vehicles, and trash leaves in the same way. Separate disposable logistics module(s) could also be used with a Mars transit vehicle, but there may be better options. The benefits of using logistics items such as food and other supplies have been recognized for solar radiation event shielding. To maintain this benefit throughout the mission, used logistics that become trash must also be used for shielding. This paper explores the competing benefits of trash disposal during the journey versus keeping the trash on board to maintain radiation shielding for the crew. Periodic disposal options include bulk jettison via an airlock and gas venting after a trash-to-gas process. If the trash is kept on board, it could simply be stored with considerations for control of odor and gas production. Alternatively, trash could be processed with heat melt compactor technology to create radiation shielding tiles from all eligible waste material. In addition to listing qualitative benefits for various options, such as reduced smell or littering, quantitative mission benefits are calculated. Disposal of trash prior to key points in the mission such as Mars orbit insertion and trans-Earth injection can save significant propellant. Alternatively, use of trash as radiation shielding could reduce the need to launch dedicated shielding materials and allow recovery of additional resources such as water. All options explored, except for storage of raw trash in the vehicle, also free up habitable volume.