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Garcia, F., Jr.

Publications and source records attributed to Garcia, F., Jr..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Correlation of predicted and measured sonic boom characteristics from the reentry of STS-1 orbiter

Characteristics from sonic boom pressure signatures recorded at 11 locations during reentry of the Space Shuttle Orbiter Columbia are correlated with characteristics of wind tunnel signatures extrapolated from flight altitudes for Mach numbers ranging from 1.23 to 5.87. The flight pressure signature were recorded by microphones positioned at two levels near the descent groundtrack along the California corridor. The wind tunnel signatures used in theoretical predictions were measured using a 0.0041-scale model Orbiter. The mean difference between all measured and predicted overpressures is 12 percent from measured levels. With one exception, the flight signatures are very similar to theoretical n-waves.

Garcia, F., Jr.↗
NASA NTRS1983

A comparison of measured and theoretical predictions for STS ascent and entry sonic booms

Sonic boom measurements have been obtained during the flights of STS-1 through 5. During STS-1, 2, and 4, entry sonic boom measurements were obtained and ascent measurements were made on STS-5. The objectives of this measurement program were (1) to define the sonic boom characteristics of the Space Transportation System (STS), (2) provide a realistic assessment of the validity of xisting theoretical prediction techniques, and (3) establish a level of confidence for predicting future STS configuration sonic boom environments. Detail evaluation and reporting of the results of this program are in progress. This paper will address only the significant results, mainly those data obtained during the entry of STS-1 at Edwards Air Force Base (EAFB), and the ascent of STS-5 from Kennedy Space Center (KSC). The theoretical prediction technique employed in this analysis is the so called Thomas Program. This prediction technique is a semi-empirical method that required definition of the near field signatures, detailed trajectory characteristics, and the prevailing meteorological characteristics as an input. This analytical procedure then extrapolates the near field signatures from the flight altitude to an altitude consistent with each measurement location.

Garcia, F., Jr.↗
NASA NTRS1982

Preliminary sonic boom correlation of predicted and measured levels for STS-1 entry

A preliminary analysis correlating peaks from sonic boom pressure signatures recorded during the descent trajectory of the Orbiter Columbia, which landed in the dry lake bed at Edwards Air Force Base (EAFB), California, with measured wind tunnel signatures extrapolated from flight altitudes to the ground has been made for Mach numbers ranging from 1.3 to 6. The flight pressure signatures were recorded by microphones positioned at ground level near the groundtrack, whereas the wind tunnel signatures were measured during a test of a 0.0041-scale model Orbiter. The agreement between overpressure estimates based on wind tunnel data using preliminary flight trajectory data and oscillograph traces from ground measurements appears reasonable at this time for the range of Mach numbers considered. More detailed studies using final flight trajectory data and digitized ground measured data will be performed.

Garcia, F., Jr.↗
NASA NTRS1975

Solution of an optimal control lifting body entry problem by an improved method of perturbation functions

This paper presents a solution to a complex lifting reentry three-degree-of-freedom problem by using the calculus of variations to minimize the integral of the sum of the aerodynamics loads and heat rate input to the vehicle. The entry problem considered does not have state and/or control constraints along the trajectory. The calculus of variations method applied to this problem gives rise to a set of necessary conditions which are used to formulate a two point boundary value (TPBV) problem. This TPBV problem is then numerically solved by an improved method of perturbation functions (IMPF) using several starting co-state vectors. These vectors were chosen so that each one had a larger norm with respect to show how the envelope of convergence is significantly increased using this method and cases are presented to point this out.

Garcia, F., Jr.↗
NASA NTRS1974

Control optimization of a lifting body entry problem by an improved and a modified method of perturbation function

A study of the solution problem of a complex entry optimization was studied. The problem was transformed into a two-point boundary value problem by using classical calculus of variation methods. Two perturbation methods were devised. These methods attempted to desensitize the contingency of the solution of this type of problem on the required initial co-state estimates. Also numerical results are presented for the optimal solution resulting from a number of different initial co-states estimates. The perturbation methods were compared. It is found that they are an improvement over existing methods.

Garcia, F., Jr.↗
NASA NTRS1973

Shuttle sonic boom - Technology and predictions

Because the shuttle differs significantly in both geometric and operational characteristics from conventional supersonic aircraft, estimation of sonic boom characteristics required a new technology base. The prediction procedures thus developed are reviewed. Flight measurements obtained for both the ascent and entry phases of the Apollo 15 and 16 and for the ascent phase only of the Apollo 17 missions are presented which verify the techniques established for application to shuttle. Results of extensive analysis of the sonic boom overpressure characteristics completed to date are presented which indicate that this factor of the shuttle's environmental impact is predictable, localized, of short duration and acceptable. Efforts are continuing to define the shuttle sonic boom characteristics to a fine level of detail based on the final system design.

Holloway, P. F.↗
NASA NTRS1973

A wind tunnel flight correlation of Apollo 16 sonic boom

A correlation of sonic boom pressure signatures recorded during reentry of the Apollo 16 command module with wind-tunnel signatures extrapolated to flight distances was made for Mach numbers of 1.83 and 9.71. The flight pressure signatures were recorded by microphones located onboard ships positioned near the ground track, whereas the wind tunnel signatures were measured during a test of a 0.016-scale model of the command module. The agreement between estimates based on wind tunnel data and flight measurements was good at the tested Mach numbers.

Garcia, F., Jr.↗
NASA NTRS1972

Thermal protection optimization for the space shuttle.

This paper discusses optimal entry trajectories for the space shuttle that minimize the weight of an entry thermal protection system. The analysis was made using mathematical models of two types of thermal protection systems that were under consideration for the space shuttle: a metallic thermal protection system, and a reusable surface insulation thermal protection system. Optimal entries were generated using maximum orbiter nose temperature as a parameter. Thermal protection system weights were computed for both fixed and variable angles of attack using three-dimensional entry trajectories. Results indicated that variable angle-of-attack entries require less thermal protection system weight than entries at a constant angle of attack (35 deg) for both systems considered. Results also showed that 95 to 99 per cent of the thermal protection system weight requirement resulted from flight regimes in which the flow was still laminar.

Garcia, F., Jr.↗
NASA NTRS1972

A Wind Tunnel Flight Correlation of Apollo 15 Sonic Boom

A correlation of sonic boom pressure signatures recorded during reentry of the Apollo 15 command module with wind-tunnel signatures extrapolated to flight distances has been made for Mach numbers of 1.16 and 4.57. The flight pressure signatures were recorded by pressure sensors located onboard ships positioned near the ground track while the wind-tunnel signatures were measured during tests of a 0.016-scale model of the command module. The agreement between estimates based on wind-tunnel data and flight measurements was better at Mach 4.57 than at Mach 1.16.

Hicks, R. M.↗