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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1997

A Model for Space Shuttle Orbiter Tire Side Forces Based on NASA Landing Systems Research Aircraft Test Results

Forces generated by the Space Shuttle orbiter tire under varying vertical load, slip angle, speed, and surface conditions were measured using the Landing System Research Aircraft (LSRA). Resulting data were used to calculate a mathematical model for predicting tire forces in orbiter simulations. Tire side and drag forces experienced by an orbiter tire are cataloged as a function of vertical load and slip angle. The mathematical model is compared to existing tire force models for the Space Shuttle orbiter. This report describes the LSRA and a typical test sequence. Testing methods, data reduction, and error analysis are presented. The LSRA testing was conducted on concrete and lakebed runways at the Edwards Air Force Flight Test Center and on concrete runways at the Kennedy Space Center (KSC). Wet runway tire force tests were performed on test strips made at the KSC using different surfacing techniques. Data were corrected for ply steer forces and conicity.

Carter, John F.↗

NASA NTRS2013

The unparalleled systems engineering of MSL’s backup entry, descent, and landing system : second chance

Second Chance (SECC) was a bare bones version of Mars Science Laboratory’s (MSL) Entry Descent & Landing (EDL) flight software that ran on Curiosity’s backup computer, which could have taken over swiftly in the event of a reset of Curiosity’s prime computer, in order to land her safely on Mars. Without SECC, a reset of Curiosity’s prime computer would have lead to catastrophic mission failure. Even though a reset of the prime computer never occurred, SECC had the important responsibility as EDL’s guardian angel, and this responsibility would not have seen such success without unparalleled systems engineering. This paper will focus on the systems engineering behind SECC: Covering a brief overview of SECC’s design, the intense schedule to use SECC as a backup system, the verification and validation of the system’s “Do No Harm” mandate, the system’s overall functional performance, and finally, its use on the fateful day of August 5th, 2012.

Reeves, Glenn↗

NASA NTRS1975

Propeller modulation effects on a scanning-beam microwave landing system

The results of a systems study and ground test of the effects of propeller modulation on a time-multiplexed, scanning-beam microwave landing system (MLS) are presented. Propeller modulation effects are analyzed in terms of spacing between receiving antenna and propeller, propeller blade width, and propeller speed. Principal study conclusions: (1) scanning beam MLS is susceptible to errors due to synchronous propeller modulation; (2) the number of synchronous interference multiples increases as the number of propeller blades increases and as the data rate decreases; (3) the probability of synchronous interference decreases at higher data rates; and (4) MLS receiver susceptibility to propeller modulation depends upon the dynamic response of the receiver automatic gain control and the respective tracking loops.

Pope, J. M.↗

NASA NTRS1984

Development and flight test of a helicopter compact, portable, precision landing system concept

An airborne, radar based, precision approach concept is being developed and flight tested as a part of NASA's Rotorcraft All-Weather Operations Research Program. A transponder based beacon landing system (BLS) applying state of the art X band radar technology and digital processing techniques, has been built and is being flight tested to demonstrate the concept feasibility. The BLS airborne hardware consists of an add on microprocessor, installed in conjunction with the aircraft weather/mapping radar, which analyzes the radar beacon receiver returns and determines range, localizer deviation, and glide slope derivation. The ground station is an inexpensive, portable unit which can be quickly deployed at a landing site. Results from the flight test program show that the BLS concept has a significant potential for providing rotorcraft with low cost, precision instrument approach capability in remote areas.

Bull, J. S.↗

NASA NTRS2022

THE NASA SPLICE PROJECT’S TERRESTRIAL TESTING OF EXTRATERRESTRIAL PRECISION LANDING SYSTEMS

The Safe and Precise Landing—Integrated Capabilities Evolution (SPLICE) project continues a NASA legacy of advancing precision landing and hazard avoidance (PL&HA) capabilities. In order to rapidly and cost-effectively de-velop and demonstrate PL&HA systems, terrestrial and suborbital testing of these path-to-spaceflight technologies is commonly used. Creating test envi-ronments on Earth that are sufficiently similar to their intended spaceflight envi-ronment is challenging. This paper will cover the experiences of the SPLICE project across its terrestrial test campaigns in preparation for lunar demonstra-tion missions.

Samuel Pedrotty↗

NASA NTRSDate not supplied

The NASA SPLICE Project’s Terrestrial Testing of Extraterrestrial Precision Landing Systems

Ron Sostaric↗

NASA NTRS1978

The effect of landing system coverage and path geometry on lateral position errors at the runway threshold

The results of an analytical study performed to determine the effect of the azimuth coverage of a Microwave Landing System (MLS) on the ability of an airplane, with an initial navigation position estimate error, to navigate to the runway threshold are presented. The test path chosen for this study consists of an initial straight segment leading into a 130 deg turn with a 2286 m radius and ending in a straight-in final approach segment. The test path configuration was varied by changing the MLS azimuth coverage angle and the final approach length. The aircraft was positioned with an inital offset to the left or right of the desired path along the line of intersection with the MLS azimuth coverage. A fast time computer simulation program, using a simplistic point mass model of the airplane, was used for this study. The data from this study indicates that the lateral position errors at the runway are primarily a function of the final approach length. The effect of the azimuth coverage on the lateral position errors was restricted by the turn characteristics of the horizontal steering control laws.

Vicroy, D. D.↗

NASA NTRS1986

Flying complex approach paths using the microwave landing system

A piloted simulation study was conducted to examine the requirements for using electromechanical flight instrumentation to provide guidance for manually controlled flight along complex, curved approach paths within the microwave landing system signal coverage. The data from these tests indicated that flight director guidance is required for the manually controlled flight of a jet transport airplane on complex, curved approach paths. Each of the three guidance algorithms tested could be used to fly the paths. However, pilot comments indicated that the use of guidance based on capturing the next straight path segment may not be acceptable since full-scale lateral deflections normally resulted during turns. Pilot comments indicated that all the approach paths tested could be used in normal airline operations. Approach paths with both multiple, sequential turns and short final path segments were demonstrated.

Knox, Charles E.↗

NASA NTRS1984

Development and flight test of a helicopter compact, portable, precision landing system concept

An airborne, radar-based, precision approach concept is being developed and flight tested as a part of NASA's Rotorcraft All-Weather Operations Research Program. A transponder-based beacon landing system (BLS) applying state-of-the-art X-band radar technology and digital processing techniques, was built and is being flight tested to demonstrate the concept feasibility. The BLS airborne hardware consists of an add-on microprocessor, installed in conjunction with the aircraft weather/mapping radar, which analyzes the radar beacon receiver returns and determines range, localizer deviation, and glide-slope deviation. The ground station is an inexpensive, portable unit which can be quickly deployed at a landing site. Results from the flight test program show that the BLS concept has a significant potential for providing rotorcraft with low-cost, precision instrument approach capability in remote areas.

Clary, G. R.↗

NASA NTRS1982

Terminal area automatic navigation, guidance, and control research using the Microwave Landing System (MLS). Part 2: RNAV/MLS transition problems for aircraft

The problems in navigation and guidance encountered by aircraft in the initial transition period in changing from distance measuring equipment, VORTAC, and barometric instruments to the more precise microwave landing system data type navaids in the terminal area are investigated. The effects of the resulting discontinuities on the estimates of position and velocity for both optimal (Kalman type navigation schemes) and fixed gain (complementary type) navigation filters, and the effects of the errors in cross track, track angle, and altitude on the guidance equation and control commands during the critical landing phase are discussed. A method is presented to remove the discontinuities from the navigation loop and to reconstruct an RNAV path designed to land the aircraft with minimal turns and altitude changes.

Pines, S.↗

NASA NTRS1976

The design, development, and flight test results of the Boeing 737 aircraft antennas for the ICAO demonstration of the TRSB microwave landing system

The Research Support Flight System, a modified Boeing 737, was used to evaluate the performance of several aircraft antennas and locations for the Time Reference Scanning Beam (TRSB) Microwave Landing System (MLS). These tests were conducted at the National Aviation Facilities Experimental Center (NAFEC), Atlantic City, New Jersey on December 18, 1975. The flight tests measured the signal strength and all pertinent MLS data during a straight-in approach, a racetrack approach, and ICAO approach profiles using the independent antenna-receiver combinations simultaneously on the aircraft. Signal drop-outs were experienced during the various approaches but only a small percentage could be attributed to antenna pattern effects.

Campbell, T. G.↗

NASA NTRS2020

Mitigating Fading in Cislunar Communications: Application to the Human Landing System

NASA’s human exploration program is currently working towards landing astronauts on the surface of the Moon by 2024, close the lunar South Pole. To guarantee astronaut safety and maximize science data return, NASA is in the process of defining the communication architecture that will support all astronaut activities from launch to surface operations. Of particular interest to this paper are links from the lunar surface back to Earth without any intermediate relays. We show that the system geometry is such that antennas on the landing system will need to be pointed at low elevation angles, thus potentially causing multi-path fading effects not typically encountered in space communications. This paper is organized in three parts. First, we characterize the multi-path fading effects expected in links between the lunar South Pole and Earth and show that for moderate data rates (less than 1 Mbps) the links suffer from slow fading. We then show that for this operations regime the performance of forward error correction schemes is significantly worse for traditional Additive White Gaussian Noise channels. Finally, we investigate multi-copy mechanisms to mitigate the effects of fading, most notably repetition schemes and Automatic Repeat Request.

Sanchez Net, Marc↗

NASA NTRS1977

Experimental and analytical dynamic flow characteristics of an axial-flow fan from an air cushion landing system model

An investigation was conducted to compare the steady-state and dynamic flow characteristics of an axial-flow fan which had been used previously as the air supply fan for some model air cushion landing system studies. Steady-state flow characteristics were determined in the standard manner by using differential orifice pressures for the flow regime from free flow to zero flow. In this same regime, a correlative technique was established so that fan inlet and outlet pressures could be used to measure dynamic flow as created by a rotating damper. Dynamic tests at damper frequencies up to 5 Hz showed very different flow characteristics when compared with steady-state flow, particularly with respect to peak pressures and the pressure-flow relationship at fan stall and unstall. A generalized, rational mathematical fan model was developed based on physical fan parameters and a steady-state flow characteristic. The model showed good correlation with experimental tests at damper frequencies up to 5 Hz.

Thompson, W. C.↗

NASA NTRS2012

Lunar Navigation Determination System - LaNDS

A portable comprehensive navigational system has been developed that both robotic and human explorers can use to determine their location, attitude, and heading anywhere on the lunar surface independent of external infrastructure (needs no Lunar satellite network, line of sight to the Sun or Earth, etc.). The system combines robust processing power with an extensive topographical database to create a real-time atlas (GIS Geospatial Information System) that is able to autonomously control and monitor both single unmanned rovers and fleets of rovers, as well as science payload stations. The system includes provisions for teleoperation and tele-presence. The system accepts (but does not require) inputs from a wide range of sensors. A means was needed to establish a location when the search is taken deep in a crater (looking for water ice) and out of view of Earth or any other references. A star camera can be employed to determine the user's attitude in menial space and stellar map in body space. A local nadir reference (e.g., an accelerometer that orients the nadir vector in body space) can be used in conjunction with a digital ephemeris and gravity model of the Moon to isolate the latitude, longitude, and azimuth of the user on the surface. That information can be used in conjunction with a Lunar GIS and advanced navigation planning algorithms to aid astronauts (or other assets) to navigate on the Lunar surface.

Quinn, David↗

NASA NTRS1991

Design, building, and testing of the post landing systems for the assured crew return vehicle

The design, building, and testing of the post landing support systems for a water landing Assured Crew Return Vehicle (ACRV) are presented. One ACRV will be permanently docked to Space Station Freedom, fulfilling NASA's commitment to Assured Crew Return Capability in the event of an accident or illness. The configuration of the ACRV is based on an Apollo Command Module (ACM) derivative. The 1990 to 91 effort concentrated on the design, building, and testing of a 1/5 scale model of the egress and stabilization systems. The objective was to determine the feasibility of: (1) stabilizing the ACM out of the range of motions which cause sea sickness; and (2) the safe and rapid removal of a sick or injured crewmember from the ACRV. The ACRV model construction is presented along with a discussion of the water test facility. The rapid egress system is also presented along with a discussion of the ACRV stabilization control systems. Results are given and discussed in detail.

Anderson, Loren A.↗

NASA NTRS1986

Development of a portable precision landing system

A portable, tactical approach guidance (PTAG) system, based on a novel, X-band, precision approach concept, was developed and flight tested as a part of NASA's Rotorcraft All-Weather Operations Research Program. The system is based on state-of-the-art X-band technology and digital processing techniques. The PTAG airborne hardware consists of an X-band receiver and a small microprocessor installed in conjunction with the aircraft instrument landing system (ILS) receiver. The microprocessor analyzes the X-band, PTAG pulses and outputs ILS compatible localizer and glide slope signals. The ground stations are inexpensive, portable units, each weighing less than 85 lb, including battery, that can be quickly deployed at a landing site. Results from the flight test program show that PTAG has a significant potential for providing tactical aircraft with low cost, portable, precision instrument approach capability.

Davis, T. J.↗

NASA NTRS2022

Mars 2020 Entry, Descent, and Landing System Software Implementation

On February 18th, 2021, the Mars 2020 project's Perseverance Rover successfully touched down on the Martian surface after nearly eight years of development. The Mars 2020 Entry, Descent, and Landing (EDL) System largely leveraged heritage from the Mars Science Laboratory (MSL) EDL System while employing targeted technological advancements. The landing process is autonomously directed by a software behavior implemented in the rover's primary flight computer called the EDL Timeline that assumes control of the vehicle six days before atmospheric entry. This paper first walks through the basics of the EDL Timeline mechanics and how the behavior is designed to account for internal system variations and environmental unknowns. It then summarizes the interactions between the EDL timeline and other high-level system behaviors like spacecraft mode transitions and system fault protection, focusing on the complications that arise when passing spacecraft control between executive functions. Although the MSL-inherited EDL System is reliable and capable, targeted updates and a thorough verification and validation program were required for Mars 2020. This paper discusses changes made to close vulnerabilities discovered during both MSL and Mars 2020 development cycles, landing system capability enhancements that were enabling for Mars 2020's mission, and how these updates were integrated with the heritage system. It then describes how both analysis and testing campaigns were utilized to verify and validate all aspects of EDL and system behaviors that run during the six days before landing, as well as the operational workarounds that were needed to address problems found during the development and commissioning process. Finally, this paper imparts lessons learned from Mars 2020 EDL development, implementation, and operations, emphasizing how systems designed to conduct time-critical mission events with low margin of error can be improved in the future.

Stehura, Aaron↗

NASA NTRSDate not supplied

Probabilistic Modeling of a Three-Stage Human Landing System Architecture

Unmitigated uncertainties are known to have previously led to failed development programs; in order to combat these uncertainties, risks and their impacts must be understood and handled to ensure program success. In this paper, a probabilistic methodology to handle uncertainties is demonstrated on a three-element Human Landing System (HLS) concept, which allows tracking of current best estimates of the vehicle’s performance and assessment of its robustness against uncertainties. This methodology has two key parts: ﬁrst, the creation of a dynamic architecture model of a three-element HLS concept; and second, its use with surrogate modeling and range estimating techniques to capture and propagate uncertainties. The DYnamic Rocket EQuation Tool (DYREQT), a space systems synthesis and sizing framework used by NASA, was used as to model the HLS architecture. For the probabilistic analysis, uncertainties of interest within the HLS concept were enumerated and represented as parameters within the DYREQT model as inputs for vehicle stages or mission proﬁle events. Range estimating — a probabilistic method that combines Monte Carlo sampling, focus on critical parameters, and heuristics to assess risk and opportunities — is then adapted with operational parameters as well as vehicle parameters in the DYREQT model to capture mission uncertainty alongside vehicle uncertainty. To perform the range estimation portion of this methodology, the DYREQT model was sampled using a Design of Experiments (DoE) to eﬃciently explore the architecture design space with respect to the set of uncertainty parameters. Then, the results were used to create surrogate models, multivariate regressions that can visualize hypercube trends in the design space, of the architecture with respect to the uncertainty parameters. Using a correlation matrix constructed for the uncertainty parameters, previously independent samples were transformed to perform a Correlated Monte Carlo on the surrogate models. This probabilistic methodology was proved to provide insight into the underlying uncertainties of the three-element HLS architecture.

Stephanie Y Zhu↗