The Monocoque Tank Analysis Spreadsheet System (MONTASS) computer program is an integrated system of Microsoft Excel worksheets and Visual BASIC functions. It was developed as a preliminary design tool that enables quick turn-around design and analysis of structural domes and truncated cone sections. MONTASS performs both design and analysis by (1) calculating the minimum skin thicknesses required by the components to withstand design temperatures and loads (such as a proof test), and then (2) running stress and buckling analyses under operational temperatures and loads. Although MONTASS was developed to analyze monocoque propellant tanks, it may also be used to analyze non-pressurized conical structures.
The MONTASS system can be run easily from the user-friendly, three page interface worksheet that controls the propellant tank analysis system. Two other visible worksheets contain material properties versus temperature and a table of stored fluids and densities. The data on both worksheets may be customized by the user. The six component worksheets and two Visual BASIC functions that comprise the MONTASS system are hidden from sight but can be easily viewed by following directions given on the interface sheet.
Design and analysis inputs include geometry, minimum allowable skin thicknesses (constraints imposed by manufacturing or fracture mechanics), fluid properties, safety factors, a choice of the max principal or von Mises failure criteria, loads, and temperatures. Material properties are interpolated from the database for the input temperatures specified by the user. The user may also choose to design the domes with either a constant or tapered skin thickness distribution.
The primary design products from MONTASS are internal volume calculations, skin thicknesses, and a summary of masses. Using this design, MONTASS then performs a stress analysis for all components and a buckling analysis for the truncated cone section. Analysis load sets may include bending moments, axial forces, ullage pressures, hydrostatic pressures, longitudinal acceleration, and rotations. MONTASS checks for material failure and for critical buckling in terms of elastic stability. The primary analysis products from MONTASS are a summary of radial and vertical deflections, material failure margins of safety for all components, and buckling margins of safety for the truncated cone section. If the tank has failed in buckling, MONTASS will also calculate the amount of pressure required to stabilize the tank.
Stand-alone MONTASS components are included to provide users the option to run the tools without the interface that is integral to the MONTASS system. An additional Excel worksheet calculates the equivalent skin thickness in monocoque cylinders which yields the same moment of inertia as a cylinder reinforced with internal, integral T-stiffeners.
MONTASS carries the NASA case number MFS-31223. It was originally released as part of the COSMIC collection.