Source: APCL, Aerospace Engineering, SNU, Seoul, The Republic of Korea(Al – Aluminum, Cu - Copper, Ge – Germanium, Si – Silicon) An amount of 273.33 W electric energy is required for melting 1 kg of aluminum in the ISS at a temperature of 750o C and pressure of 96.52 kPa. Additionally, 750-1000° C range heating system is required to retain aluminum in the liquid state at a pressure of 1.03 MPa in the atomization process of 12 liters of water, obtained from the alkaline fuel cell, at an electric energy consumption of 3-5 kW. The potassium hydroxide is used as an electrolyte in the alkaline fuel cells at a temperature of 90o C at a pressure of 101.35 kPa. During this process 9 liters of water and 33.33 kW of electricity are acquired as derivatives for 1 kg of hydrogen. The required amount of water is generated from the Bacon fuel cell for the atomization process. The estimated electric power needed for atomization, dewatering and filtering processes is 1.5 kW. Note that a temperature of 55° C for dewatering [39] and 24° C for filtering must be maintained in the system. The water is segregated into hydrogen and oxygen with the aid of the potassium hydroxide as an electrolyte at an energy consumption of 50 kW for 1 kg of hydrogen at a temperature range of 60-80o C, and at a pressure of 3 MPa. The generated hydrogen and oxygen are permitted to recycle in the onboard system to produce the water continuously for the water atomization process. The required powder, as an end product with desirable size, is obtained through appropriate sieving. Note that, if necessary, hydrogen gas could be either transported from the earth or obtained from space by utilizing the Bussard’s ramjet [40].
The solar energy conversion system is invoked for an efficient power generation, as the ISS has 2,500 m2 solar panel, which could produce up to 84–120 kW [41]. Additionally, the fuel cell could contribute 33.33 kW of electricity, which mainly utilized for the recycling process. In the proposed technique, a total amount of 40 kW is required for processing 1 kg of aluminum. It is estimated that up to 1 kW power can be generated using a solar panel with one square meter area.
The satellite, named SNUSAT-2, a 3 U CubeSat designed and developed by the Seoul National University (SNU), South Korea for remote sensing is selected for our analytical case study. The main elements and the connected materials employed in the SNUSAT are given inTable-2 . It is evident from the component details that once this SNUSAT becomes non-operational, it gives 1350 g of aluminum powder. In the case of a non-operational Vanguard-1 [42] we could collect an amount of 1420 g of aluminum through recycling, which could be converted into fuels for spacecraft propulsion.