The future of manned and unmanned spaceflight and exploration depends on economical access to space through multifunctional, lightweight materials. Boron nitride nanotube (BNNT) composites offer distinct advantages for enhanced survivability during long-term flights. A production technique has been developed to manufacture BNNTs that implements laser energy deposition on a boron sample in a pressurized test rig.

Flow in a BNNT production rig was modeled. A laser provides a thermal energy source to the tip of a boron rod in a high-pressure nitrogen chamber, causing a plume of boron-rich gas to rise. The buoyancy-driven flow is modeled as mixture of thermally perfect gases (B, B2, N, N2, BN) in thermochemical equilibrium, assuming steadystate melt and vaporization from a 1-mm radius spot at the axis of an axisymmetric chamber.

The simulation is intended to define the macroscopic thermochemical environment from which boron-rich species, including nanotubes, condense out of the plume. Simulations indicate a high-temperature environment within 1 mm of the surface sufficient to dissociate molecular nitrogen and form B2 and BN at the base of the plume. Modifications to Program LAURA, a finite-volume-based solver for hypersonic flows including coupled radiation and ablation, enable this simulation.

This work was done by Peter A. Gnoffo and Catharine C. Fay of Langley Research Center. LAR-18132-1