However, a shroud adds weight and manufacturing complexity. As a pump spins faster, stress due to centrifugal force in the impeller increases. The weight of the shroud increases the stress and limits the speed at which a pump can operate. A pump impeller without a shroud can operate at higher speeds with lower stress and generate more head. Benefits of the new pump include lower manufacturing costs, reduced weight, and increased payload to orbit.
Comparative data is shown below.
Thrust cells, or thrust chambers, are the parts of rocket engines that really take the heat, and erosion due to the high speed of the exiting hot gasses can limit performance and add to maintenance costs. Under an ASTP task being carried out by MSFC and Glenn Research Center , a new alloy of copper, chromium and niobium is being developed that will enable longer life, lower maintenance costs and higher performance. To get the desired properties, the alloy is produced in the form of a powder, which is then formed into desired shapes under heat and pressure. Under an ASTP task, Glenn Research Center is demonstrating that a heat resistant ceramic composite structure can be hot gas impermeable, and used for an uncooled hot gas generator combustor. NASA's Glenn Research Center will deliver a full-scale, lightweight design of a gas generator combustor assembly, and provide design data based on mechanical and thermophysical properties.