Israel S. Rego

2‐D Airbreathing Lightcraft Engine Experiments in Quiescent Conditions

Ground‐breaking laser propulsion (LP) experiments were performed under quiescent conditions with a 25 cm wide, two‐dimensional Lightcraft model using a Lumonics TEA‐622 CO2 laser emitting ∼ 1 μs pulses. In preparation for subsequent hypersonic experiments, this static test campaign was conducted at ambient pressures of 0.06, 0.15, 0.30 and 1 bar with laser pulse energies of 150 to 230 J. Time‐variant pressure distributions, generated over engine “absorption chamber” walls, were integrated to obtain total impulse and momentum coupling coefficients (Cm) representative of a single propulsion cycle. Schlieren visualization of laser‐induced air breakdown and expanding blast waves was also accomplished. Surprisingly, the Cm results of 600‐3000 Ns/MJ were 2.5x to 5x greater than previous results from smaller Lightcraft models; this suggests that higher static Cm performance can likely be achieved in larger scale LP engines. This research collaboration, forged between the USAF and Brazilian Air Force, was carried...

Experimental Analysis of a 2‐D Lightcraft in Static and Hypersonic Conditions

Aiming at the hypersonic phase of the Earth‐to‐Orbit trajectory for a laser propelled vehicle, a 2‐D Lightcraft model was designed to be tested at the T3 Hypersonic Shock Tunnel at the Henry T. Nagamatsu Laboratory for Aerodynamics and Hypersonics. A high energy laser pulse was supplied by a Lumonics TEA 620 laser system operating in unstable resonator cavity mode. The experiments were performed at quiescent (no flow) conditions and at a nominal Mach number of 9.2. A Schlieren visualization apparatus was used in order to access both the cold hypersonic flowfield structure (without laser deposition) and the time dependent flowfield structure, taking place after the laser induced breakdown inside the absorption chamber. The model was fitted with piezoelectric pressure transducers and surface junction thermocouples in an attempt to measure pressure and heat transfer time dependent distributions at the internal surfaces of the model’s absorption chamber. The 2‐D model followed a modular design for flexibility...

2‐D Air‐Breathing Lightcraft Engine Experiments in Hypersonic Conditions

Experiments were performed with a 2‐D, repetitively‐pulsed (RP) laser Lightcraft model in hypersonic flow conditions. The main objective was the feasibility analysis for impulse generation with repetitively‐pulsed air‐breathing laser Lightcraft engines at hypersonic speeds. The future application of interest for this basic research endeavor is the laser launch of pico‐, nano‐, and micro‐satellites (i.e., 0.1–100 kg payloads) into Low‐Earth‐Orbit, at low‐cost and on‐demand. The laser propulsion experiments employed a Hypersonic Shock Tunnel integrated with twin gigawatt pulsed Lumonics 620‐TEA CO2 lasers (∼ 1 μs pulses), to produce the required test conditions. This hypersonic campaign was carried out at nominal Mach numbers ranging from 6 to 10. Time‐dependent surface pressure distributions were recorded together with Schlieren movies of the flow field structure resulting from laser energy deposition. Results indicated laser‐induced pressure increases of 0.7–0.9 bar with laser pulse energies of ∼ 170 J, o...