With the ever-growing number of spacecraft launching into orbit, alongside the growing desire for propulsion systems on many of these craft, an emerging opportunity is present in the potential servicing and refuelling of these spacecraft. Proposals for propellant resupply services are growing in abundancy, primarily with architectures involving craft launching from the Earth's surface to transfer their cargo of propellant to in-orbit customers. Current state of the art solutions utilise hydrazine, however its popularity is dwindling with the European Chemicals Agency considering outlawing it due to its toxic and carcinogenic nature. For this reason, SolvGE, a start-up based at TU Delft in the Netherlands, has proposed a sustainable architecture involving the production of high concentration hydrogen peroxide (H2O2) from water-ice present at off-Earth locations. While H2O2 does possess a lower specific impulse than hydrazine, it has several other attractive characteristics such as its high density, storability, and nontoxicity. To investigate the viability of such an architecture, a Single Stage to Orbit refuelling craft is sized, showing that with a structural coefficient of 0.3 and an I_sp of 330 s - 340 s, a refuelling craft could launch from the Moon to low lunar orbit, and from Deimos and Phobos to low Martian orbit, to refuel spacecraft with 200 L of H2O2. A trade-off of potential refuelling mechanisms shows that a piston-based system, used in conjunction with pressurant gas, a gas generator, or a pump, is a good candidate for high cycle usage. Comparison of permutations of these systems shows low variation in total system mass (< 2%) over different transfer masses and transfer rates. A prototype test set up of the transfer mechanism using pressurant gas is created to investigate the functioning of the piston system and the relevant pressurant parameters. Transfer tests with and without the piston head show a 17%-25% increase in pressurant mass required when a piston head is added. Testing with the system inverted shows 9% more pressurant is required due to the adverse gravity gradient. Thus, a spacecraft capable of refuelling 200 L of H2O2 weighs approximately the same as the wet mass of the Apollo lunar lander (~16000 kg) and is able to serve customers in low lunar and Martian orbits in a reusable manner. Further research on high cycles of the piston as well as possible mass savings, and actuation using H2O2 gas generators will further assess the applicability of piston transfer systems for in-orbit refuelling.