Engineering topics

Stalmach, C. J., Jr.

Publications and source records attributed to Stalmach, C. J., Jr..

6 records

NASA NTRS1977

Effects of scaled heatshield tile misalignment on Orbiter boundary-layer transition

The article addresses the problem of assessing the sensitivity of the heat transfer rate of a Space Orbiter windward surface and boundary-layer transition data to surface features, or 'roughness elements', characteristic of randomly misaligned heat shield tiles. Selected heat shield tiles were precision-formed on the surface of a 0.0175-scale Orbiter model. Selective electroless plating and selective electrochemical etching techniques were employed. Effects of roughness on the location of boundary-layer transition were markedly influenced by the wall-to-total temperature ratios, according to wind-tunnel test results.

Goodrich, W. D.↗

NASA NTRS1977

Aluminum transfer method for plating plastics

Electroless plating technique produces plate of uniform thickness. Hardness and abrasion resistance can be increased further by heat treatment. Method results in seamless coating over many materials, has low thermal conductivity, and is relatively inexpensive compared to conventional methods.

Goodrich, W. D.↗

NASA NTRS1976

Aeroheating model advancements featuring electroless metallic plating

Discussed are advancements in wind tunnel model construction methods and hypersonic test data demonstrating the methods. The general objective was to develop model fabrication methods for improved heat transfer measuring capability at less model cost. A plated slab model approach was evaluated with cast models containing constantan wires that formed single-wire-to-plate surface thermocouple junctions with a seamless skin of electroless nickel alloy. The surface of a space shuttle orbiter model was selectively plated with scaled tiles to simulate, with high fidelity, the probable misalignments of the heatshield tiles on a flight vehicle. Initial, Mach 8 heating results indicated a minor effect of tile misalignment roughness on boundary layer transition, implying a possible relaxation of heatshield manufacturing tolerances. Some loss of the plated tiles was experienced when the model was tested at high heating rates.

Stalmach, C. J., Jr.↗

NASA NTRS1975

Developments in convective heat transfer models featuring seamless and selected detail surfaces, employing electroless plating

Several model/instrument concepts employing electroless metallic skin were considered for improvement of surface condition, accuracy, and cost of contoured-geometry convective heat transfer models. A plated semi-infinite slab approach was chosen for development and evaluation in a hypersonic wind tunnel. The plated slab model consists of an epoxy casting containing fine constantan wires accurately placed at specified surface locations. An electroless alloy was deposited on the plastic surface that provides a hard, uniformly thick, seamless skin. The chosen alloy forms a high-output thermocouple junction with each exposed constantan wire, providing means of determining heat transfer during tunnel testing of the model. A selective electroless plating procedure was used to deposit scaled heatshield tiles on the lower surface of a 0.0175-scale shuttle orbiter model. Twenty-five percent of the tiles were randomly selected and plated to a height of 0.001-inch. The purpose was to assess the heating effects of surface roughness simulating misalignment of tiles that may occur during manufacture of the spacecraft.

Stalmach, C. J., Jr.↗

NASA NTRS1972

Effect of mass-addition distribution and injectant on heat transfer and transition criteria.

Surface pressures, heat-transfer rates, and transition locations for a sharp cone (whose semivertex angle is 12 deg) were obtained in a hypervelocity wind tunnel at a free-stream Mach number of 12 and a free-stream Re/ft range of 3,000,000 to 6,000,000. The effects of injecting either methane, nitrogen, or Freon-22 (at rates up to 2.1% of free-stream rate) were studied for a uniform injection-distribution and for a variable injection-distribution. Gaseous injection had little effect on the surface pressure measurements. For a given mass injection distribution, the laminar region heat-transfer decreases as the injection rate increases or as the molecular weight of the injectant decreases. For a given mass-injection rate (integrated over the surface of the entire cone), the transition location and heat-transfer rates were sensitive to the injection distribution. The transition Reynolds numbers were significantly greater when the local injection rate was constant over the surface of the cone.

Bertin, J. J.↗

NASA NTRS1971

A study of boundary layer transition on outgassing cones in hypersonic flow

Surface heat-transfer rates and pressures were measured at hypersonic speeds on sharp cones at zero angle of attack with and without gas injection. Using the non-injection results for reference data the effects on heating and transition location of surface roughness and injectant rate, distribution and composition were determined. The transition location was sensitive to the injectant distribution. The transition Reynolds numbers were significantly greater when the injectant distribution was constant than with a variable distribution. The measured heat-transfer distribution were also strongly dependent upon the injectant distribution. Transition Reynolds number results obtained during this program with a variable injectant distribution were correlated with a limited amount of data available for a degrading model tested in a different facility. Transitional data with constant injectant distribution were correlated with earlier results. An empirical correlation of heat-transfer reduction due to gas injection in turbulent flow was developed for both distributions tested. Several effects of mass addition on heating and transition, which have been earlier reported, were observed.

Stalmach, C. J., Jr.↗