Search NASA⌕ Search

Engineering topics

Sobota, Thomas H.

Publications and source records attributed to Sobota, Thomas H..

Analysis and demonstration of a Scramaccelerator system

The Scramaccelerator, a novel type of supersonic-combustion, tube-based launcher has been developed that can accelerate almost any mass to velocities of 3 to over 7 km/sec. This paper describes the technology demonstration of the concept by firing 120-g projectiles into a 38 mm barrel at 2.8 to 3.2 km/sec. The results from the technology demonstration are presented along with calculated performance of the demonstration tests. Critical test issues discussed include sabot separation, venting requirements, and test performance. The results, obtained during testing indicate projectile accelerations were achieved of approximately 5000 g. Hence, these tests demonstrate successful Scramaccelerator operation and acceleration at approximately 1.95 times the Chapman Jouguet detonation velocity, far greater than the 1.15 to 1.3 times previously demonstrated. In addition, the tests demonstrate hypersonic propulsion at Mach numbers above 8, acceleration at greater than 3 km/s, and system integration technology sufficient to accomplish this success.

Humphrey, Joseph W.↗

Numerical simulation of fluid flow around a scramaccelerator projectile

Numerical simulations of the fluid motion and temperature distribution around a 'scramaccelerator' projectile are obtained for Mach numbers in the 5-10 range. A finite element method is used to solve the equations of motion for inviscid and viscous two-dimensional or axisymmetric compressible flow. The time-dependent equations are solved explicitly, using bilinear isoparametric quadrilateral elements, mass lumping, and a shock-capturing Petrov-Galerkin formulation. Computed results indicate that maintaining on-design performance for controlling and stabilizing oblique detonation waves is critically dependent on projectile shape and Mach number.

Pepper, Darrell W.↗