Comparison of actual versus predicted lunar surface erosion caused by Apollo 11 descent engine
Lunar surface erosion due to Apollo 11 descent engine
Mason, C. C.↗
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Performance verification of the lunar descent program - P66 auto, task E-72C
Results of simulated runs to evaluate lunar module descent performance of P66 automatic control and guidance system
Dwivedi, N. P.↗
A statistical study of ability of simulated pilots to control the approach and descent of the lunar module to the lunar surface
Statistical analysis of simulated pilot ability to control lunar module approach and descent to lunar surface
Lichtenstein, J. H.↗
Application of the method of steepest descent to laminated shield weight optimization with several constraints: Theory
The method of steepest descent used in optimizing one-dimensional layered radiation shields is extended to multidimensional, multiconstraint situations. The multidimensional optimization algorithm and equations are developed for the case of a dose constraint in any one direction being dependent only on the shield thicknesses in that direction and independent of shield thicknesses in other directions. Expressions are derived for one-, two-, and three-dimensional cases (one, two, and three constraints). The precedure is applicable to the optimization of shields where there are different dose constraints and layering arrangements in the principal directions.
Lahti, G. P.↗
The DOPEX Code: an Application of the Method of Steepest Descent to Laminated-Shield-Weight Optimization with Several Constraints
A two- or three-constraint, two-dimensional radiation shield weight optimization procedure and a computer program, DOPEX, is described. The DOPEX code uses the steepest descent method to alter a set of initial (input) thicknesses for a shield configuration to achieve a minimum weight while simultaneously satisfying dose constaints. The code assumes an exponential dose-shield thickness relation with parameters specified by the user. The code also assumes that dose rates in each principal direction are dependent only on thicknesses in that direction. Code input instructions, FORTRAN 4 listing, and a sample problem are given. Typical computer time required to optimize a seven-layer shield is about 0.1 minute on an IBM 7094-2.
Lahti, G. P.↗
Apollo experience report: Mission planning for lunar module descent and ascent
The premission planning, the real-time situation, and the postflight analysis for the Apollo 11 lunar descent and ascent are described. A comparison between premission planning and actual results is included. A navigation correction capability, developed from Apollo 11 postflight analysis was used successfully on Apollo 12 to provide the first pinpoint landing. An experience summary, which illustrates typical problems encountered by the mission planners, is also included.
Bennett, F. V.↗
Biological effects of fuel and exhaust components from spacecraft descent engines employing hydrazine
The effect of the products of the Viking terminal descent engine fuel upon possible extraterrestrial life at the Martian landing site is examined. The effects of the engine exhaust, the hydrazine fuel, and the breakdown products of the latter on terrestrial microorganisms have been studied. The results indicate that the gaseous exhaust products would probably not be hazardous to microorganisms, but that liquid hydrazine would be lethal.
Lehwalt, M. E.↗
Apollo 16 LM-11 descent propulsion system final flight evaluation
The performance of the LM-11 Descent Propulsion System during the Apollo 16 Mission was evaluated and found to be satisfactory. The average engine effective specific impulse was 0.1 second higher than predicted, but well within the predicted 1 sigma uncertainty of 0.2 seconds. The engine performance corrected to standard inlet conditions for the FTP portion of the burn at 50 seconds after ignition was as follows: thrust, 9839 lbf; specific impulse, 306.9 sec; and propellant mixture ratio, 1.592. These values are +0.34, +0.03 and +0.0 percent different, respectively, from the values reported from engine acceptance tests and were within specification limits. Several flight measurement discrepancies that existed during the flight are discussed.
Avvenire, A. T.↗
Apollo 14 mission report. Supplement 5: Descent propulsion system final flight evaluation
The performance of the LM-8 descent propulsion system during the Apollo 14 mission was evaluated and found to be satisfactory. The average engine effective specific impulse was 0.1 second higher than predicted, but well within the predicted l sigma uncertainty. The engine performance corrected to standard inlet conditions for the FTP portion of the burn at 43 seconds after ignition was as follows: thrust, 9802, lbf; specific impulse, 304.1 sec; and propellant mixture ratio, 1603. These values are + or - 0.8, -0.06, and + or - 0.3 percent different respectively, from the values reported from engine acceptance tests and were within specification limits.
Avvenire, A. T.↗
Emergency descent device
Device includes cable wound on reel; special assembly enclosed in fluid medium controls unwinding speed of cable during descent. Device is compact and reliable. It can be rewound quickly because reel disengages from latches when it is turned in opposite direction.
Belew, R. R.↗
Apollo 16, LM-11 descent propulsion system final flight evaluation
The performance of the LM-11 descent propulsion system during the Apollo 16 missions was evaluated and found satisfactory. The average engine effective specific impulse was 0.1 second higher than predicted, but well within the predicted one sigma uncertainty of 0.2 seconds. Several flight measurement discrepancies existed during the flight as follows: (1) the chamber pressure transducer had a noticeable drift, exhibiting a maximum error of about 1.5 psi at approximately 130 seconds after engine ignition, (2) the fuel and oxidizer interface pressure measurements appeared to be low during the entire flight, and (3) the fuel propellant quantity gaging system did not perform within expected accuracies.
Avvenire, A. T.↗
A steepest descents method for reentry optimization
A steepest descents optimization program is applied to the problem of a lifting vehicle entering the earth's atmosphere. The program employs penalty functions representing terminal conditions and inflight inequality constraints. During each iteration, it reduces a single performance measure which is the sum of the performance index and the penalty functions. Therefore, only one set of adjoint equations must be integrated per iteration. Values of weight factors, multiplying the penalty functions, are automatically adjusted before each iteration in order that the penalty functions will approach acceptable values. This method is shown to be a form of the classical Lagrange multiplier methods.
Andrus, J. F.↗
Time-controlled descent guidance in uncertain winds
A procedure has been developed for constructing a statistical model of the altitude-dependent mean wind profile from the historical record of wind measurements at particular locations. The model is constructed by fitting a Markov process, with altitude as the stage variable, to the historical wind data. The wind model, together with the aircraft dynamics and the error characteristics of the navigation system, are incorporated in the design of a state estimator, which gives the minimum variance estimate of the aircraft state and the wind vector. The state and wind estimates are used as inputs to a linear feedback law for guiding the aircraft along the nominal trajectory. An example design of a time-constrained (4D RNAV) descent guidance system is presented, showing tracking accuracy, control activity, and probability of arrival time with and without the wind estimator.
Menga, G.↗
Use of steepest descent and various approximations for efficient computation of minimum noise aircraft landing trajectories
The following areas related to landing trajectory optimization research were discussed: (1) programming and modifying the steepest descent optimization procedure, (2) successfully iterating toward the optimum for a four-mile trajectory, (3) beginning optimization runs for a twenty-mile trajectory, and (4) adapt wind tunnel data for computer usage. Other related areas were discussed in detail in the two previous annual reports.
Cook, G.↗
The design and reconstruction of the Viking Lander descent trajectories
The success of the Viking Mission is truly a major milestone in this country's planetary exploration program. This paper deals with the trajectory characteristics of the Viking Lander descent trajectories, beginning with the imposed requirements and constraints, the final preflight design based on the final hardware and operational capability, and ending with the actual performance achieved. A comparison between the predicted and actual trajectory characteristics is made to indicate the achieved accuracy and modeling fidelity. Also, estimates of the Martian environment derived from the entry-trajectory reconstruction process are presented.
Euler, E. A.↗
Examination of the liquid line of descent of mare basalts in light of data from melt inclusions in olivine
Data on 226 melt inclusions and their host olivines (173 new analyses) are presented and interpreted in terms of general liquid lines of descent and olivine fractionation. The melt inclusions in olivine along with those in ilmenite and late-stage mesostasis in mare basalts define a complex trend. The trend is complicated by the effects of ilmenite, plagioclase, and pyroxene fractionation within the melt inclusions in olivine, the fact that most of the basalts were multiply saturated during olivine fractionation, and the phenomenon of late-stage silicate immiscibility. It is suggested that the first two factors can account for the observed marked divergence of the melt inclusion data from simple early olivine fractionation trends. The elimination of the effects of daughter mineral fractionation by homogenization experiments is considered.
Weiblen, P. W.↗
Spectrophotometric experiment on the Verera-11 and Venera-12 descent vehicles: Some results of the analysis of the spectrum of the daytime sky of Venus
The spectra of the daytime sky of Venus were recorded on the Venera-11 and Venera-12 descent vehicles at various altitudes above the planet's surface, within the interval of 4500 to 12,000 Angstroms. The angular distribution of the brightness of the scattered radiation was recorded and the ratio of water and carbon dioxide were studied, with respect to the cloud cover boundaries.
Moroz, V. I.↗
Flight-Management Algorithm for Fuel-Conservative Descents
Federal Aviation Administration has developed an automated time-based metering form of air traffic control for arrivals into terminal area called local flow management/profile descent (LFM/PD). LFM/PD saves fuel by matching airplane arrival flow to airport acceptance rate through time-control computations and by allowing pilot to descend at his discretion from cruise altitude to metering fix in an idle-thrust, clean configuration (landing gear up, flaps zero, speed brakes retracted).
Knox, C. E.↗