A fundamental description of the heat transfer mechanisms leading to the combustion of metals in a pure oxygen atmosphere over a range of levels of gravity is important in understanding spacecraft fire safety. In this study, a new method of metal specimen heating to the point of combustion by focused optical radiation was used. A computational model of the laboratory combustion chamber and specimen heating was developed. Accuracy of the computational software was evaluated with two test cases comparing calculated output with experimental data from the literature. Model accuracy was evaluated by comparing computational output with experimental data at 1.0 g and 0.1 MPa. A range of gravity from 0.0 g to 10.0 g and a range of pressure from 0.01 MPa to 1.0 MPa was then explored. The results indicated that for a constant input heat flux on the specimen, convection heat transfer increased and asymptotically approached a limit for both the increased gravity case and increased pressure case. This limit in convection heat transfer caused a limit in minimum specimen temperature regardless of gravity field magnitude or chamber pressure within the ranges studied. In addition, it has been shown computationally that the microgravity laminar free convection environment can be simulated in the terrestrial laboratory by reducing the ambient pressure.