Recent measurements of pre-equilibrium neutron and proton transverse emission from 112,124 Sn+ 112,124 Sn reactions at 50 MeV/A have been completed at the National Superconducting Cyclotron Laboratory. Free nucleon transverse emission ratios are compared to those of A=3 mirror nuclei. Comparisons are made to BUU transport calculations and conclusions concerning the density dependence of the asymmetry term of the nuclear equation-of-state at sub-nuclear densities are made. The double-ratio of neutron-proton ratios between two reactions is employed as a means of reducing first-order Coulomb effects and detector efficiency effects. Comparison to BUU model predictions indicate a density dependence of the asymmetry energy that is closer to a form in which the asymmety energy increases as the square root of the density for the density region studied. A coalescent-invariant analysis is introduced as a means of reducing suggested difficulties with cluster emission in total nucleon emission. Future experimentation is presented.PACS numbers: 25.70.Mn,21.65.+f,26.62.+c The nuclear symmetry energy increases the masses of nuclei with very different neutron and proton concentrations and limits the neutron concentration and maximum neutron number N of any element. In the interior regions of neutron stars, where neutrons may comprise over 90% of the matter, the symmetry energy may contribute the bulk of the pressure supporting the star [1]. The nuclear equation-of-state at densities of 0.5≤ ρ ρ0 ≤10 (where ρ 0 is the nuclear saturation density) governs many of the neutron star macroscopic properties, including radius, moment of inertia, core structure [2], cooling rates, and the possible collapse of a neutron star into a black hole [3,4,5].Constraints on the symmetry energy at sub-saturation density have been obtained from measurements of the diffusion of neutrons and protons between nuclei of different asymmetry δ = (N-Z)/(N+Z) in peripheral collisions [6,7]. (Here N and Z are the relevant neutron and proton number of the nuclei.) Measurements of nuclear masses, isovector collective excitations and neutron skin measurements may also provide constraints at densities less than ρ 0 . Nevertheless, the density dependence of the symmetry energy is not known well enough to constrain the relevant neutron star properties. Using an alternative approach to improve present constraints, new measurements of the ratios of neutron and proton spectra in central heavy ion collisions are presented and compared to transport theory calculations. These calculations display a strong sensitivity to the density dependence of the symmetry energy, from which additional contraints may ultimately be derived [8] Using proton and neutron densities calculated from the non-linear relativistic mean-field theories as inputs, the dynamics of nucleon-nucleon collisions are calcuated. These calculations utilize nucleonic mean field potentials corresponding to an equation-of-state that can be expressed (at zero temperature) in terms of the mean energy of a nuc...