AN ANALYSIS OF FREE-FLIGHT CIRCUMLUNAR TRAJECTORIES
Determination of free-flight circumlunar trajectories, from orbital launch to reentry into the earths atmosphere
CIRCUMLUNAR TRAJECTORY↗
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Conflict Probability Estimation for Free Flight
The safety and efficiency of free flight will benefit from automated conflict prediction and resolution advisories. Conflict prediction is based on trajectory prediction and is less certain the farther in advance the prediction, however. An estimate is therefore needed of the probability that a conflict will occur, given a pair of predicted trajectories and their levels of uncertainty. A method is developed in this paper to estimate that conflict probability. The trajectory prediction errors are modeled as normally distributed, and the two error covariances for an aircraft pair are combined into a single equivalent covariance of the relative position. A coordinate transformation is then used to derive an analytical solution. Numerical examples and Monte Carlo validation are presented.
Paielli, Russell A.↗
Status Report for the Hypervelocity Free-Flight Aerodynamic Facility
The Hypervelocity Free-Flight Aerodynamic Facility, located at Ames Research Center, is NASA's only aeroballistic facility. During 1997, its model imaging and time history recording systems were the focus of a major refurbishment effort. Specifically the model detection, spark gap (light source); Kerr cell (high speed shuttering); and interval timer sub-systems were inspected, repaired, modified or replaced as required. These refurbishment efforts have fully restored the HFFAF's capabilities to a much better condition, comparable to what it was 15 years ago. Details of this refurbishment effort along with a brief discussion of future upgrade plans are presented.
Cornelison, Charles J.↗
Free Flight and Self-Separation from the Flight Deck Perspective
The concept of "free flight", while still being developed, is intended to emphasize more, flexibility for operators in the National Airspace System (NAS) by providing more separation responsibility to pilots, New technologies, procedures, and concepts have been suggested by the aviation community to enable this task; however, much work needs to be accomplished to help define and evaluate the concept feasibility. The purpose of this simulation was to begin examining some of the communication and procedural issues associated with self-separation in the enroute environment. A simulation demonstration was conducted in the Boeing 747-400 simulator at NASA Ames Research Center. Commercial pilots (from a U.S. domestic carrier) current on the B747-400 aircraft were the participants. Ten flight crews (10 captains, 10 first officers) flew in the Denver enroute airspace environment. A new alerting logic designed to allow for airborne self-separation was created for this demonstration. This logic assumes automatic dependent surveillance broadcast (ADS-B) capability and represented aircraft up to 120 nautical miles on the display. The new flight deck display features were designed and incorporated on the existing navigational display in the simulator to allow for increased traffic and maneuvering information to the flight crew. New tools were also provided to allow the crews to assess conflicts and potential maneuvers before implementing them. Each of the flight crews flew eight different scenarios in the Denver enroute airspace. The scenarios included eight to ten other aircraft, and each scenario was created with the intent of having one of the other aircraft become an operational conflict for our simulator aircraft. Different types of conflict geometries were represented across the eight scenarios. Also, some scenarios allowed for more time to detect a potential clearance, while others allowed for less time for'detection. Additionally, the crews were asked to a ply the Visual Flight Rules (VFR) right of way rules when determining who should maneuver in a conflict situation; therefore, the scenarios were designed to test different applications of those recommendations, Data analyses include an evaluation of crew procedures and communication. The application of the VFR right-of-way rules are being explored. Timing variables are being examined to determine potential efficiency differences between scenarios and conflict types. Proximity of aircraft will be assessed as one indication of the operational safety. The intent of these evaluations is to help provide definitions and guidelines of negotiation procedures in a self-separation environment assuming automated data link technology (ADS-B). Also, definitions of likely flight crew maneuvers and application to current VFR right-of-way rules may be obtained, along with guidelines for negotiation procedures between flight crews.
Lozito, Sandra↗
Conflict Probe Concepts Analysis in Support of Free Flight
This study develops an operational concept and requirements for en route Free Flight using a simulation of the Cleveland Air Route Traffic Control Center, and develops requirements for an automated conflict probe for use in the Air Traffic Control (ATC) Centers. In this paper, we present the results of simulation studies and summarize implementation concepts and infrastructure requirements to transition from the current air traffic control system to mature Free Right. The transition path to Free Flight envisioned in this paper assumes an orderly development of communications, navigation, and surveillance (CNS) technologies based on results from our simulation studies. The main purpose of this study is to provide an overall context and methodology for evaluating airborne and ground-based requirements for cooperative development of the future ATC system.
Warren, Anthony W.↗
Development of a Free-Flight Simulation Infrastructure
In anticipation of a projected rise in demand for air transportation, NASA and the FAA are researching new air-traffic-management (ATM) concepts that fall under the paradigm known broadly as ":free flight". This paper documents the software development and engineering efforts in progress by Seagull Technology, to develop a free-flight simulation (FFSIM) that is intended to help NASA researchers test mature-state concepts for free flight, otherwise referred to in this paper as distributed air / ground traffic management (DAG TM). Under development is a distributed, human-in-the-loop simulation tool that is comprehensive in its consideration of current and envisioned communication, navigation and surveillance (CNS) components, and will allow evaluation of critical air and ground traffic management technologies from an overall systems perspective. The FFSIM infrastructure is designed to incorporate all three major components of the ATM triad: aircraft flight decks, air traffic control (ATC), and (eventually) airline operational control (AOC) centers.
Miles, Eric S.↗
Supersonic Free-Flight Dynamics Testing in the Stratosphere
A new technique for obtaining stratospheric free-flight dynamics data for atmospheric entry capsules is described. The Stratospheric Projectile Experiment of Entry Dynamics (SPEED) represents a new approach to characterizing the free-flight dynamics of vehicles in the supersonic and transonic regime of flight. The SPEED test architecture leverages a stratospheric balloon and 3D-printed flight system in a novel two-stage configuration to deliver test articles to supersonic conditions in the atmosphere which achieve dynamic similitude with a full-scale vehicle. Designed to address the limitations of existing test facilities, SPEED captures the complete time evolution of a vehicle’s dynamic state while producing a statistically significant number of observed flight trajectories to address the stochastic nature of the wake-driven dynamic stability phenomenon. SPEED was developed over two years at NASA Ames Research Center. The inaugural flight of the SPEED test platform was conducted in the summer of 2024 where scaled capsules of the Mars Sample Return Earth Entry System and Dragonfly entry vehicle were tested. This paper describes the motivation for a new test architecture, operational constraints and achievable flight test envelopes, the design and development of the SPEED concept, and results from the demonstration flight. Techniques for estimating the dynamic aerodynamic characteristics and atmospheric conditions for each test article individually and as a collective are also discussed.
Entry Vehicle↗
Recent free-flight boundary-surface aerody- namic noise measurements
Free-flight boundary-layer aerodynamic noise measurements
FREE FLIGHT↗
Free-flight telemetry testing in the jet propulsion laboratory wind tunnels
Free flight telemetry testing in hypersonic wind tunnel for obtaining interference-free base pressure data
BASE PRESSURE↗
Comparison of the Drag of a Fin-Stabilized Body of Revolution and of a Complete Airplane Configuration as Obtained at Transonic Speeds in a Slotted Wind Tunnel and in Free Flight
A comparison of the zero-lift drag coefficients at Mach numbers from 0.81 to 1.41 of a fin-stabilized parabolic body of revolution as measured in the Langley transonic blowdown tunnel has been made with measurements obtained in free-flight on a larger but geometrically similar model. The absolute values of drag coefficient obtained in the slotted wind tunnel were equivalent to the free-flight drag-coefficient values up to a Mach number of 1.4 when adjustments were made for the effect on viscous drag of differences in Reynolds number between the two test conditions. Excellent agreement was obtained between the two tests for the pressure-drag variation with Mach number, regardless of whether the scale effect on skin friction was considered. Favorable agreement was also obtained between the pressure-drag increments due t o the presence of the stabilizing fins as determined in the wine tunnel from fins-on and fins-off tests and as obtained by a different method in free flight. Tests of a specific airplane configuration to obtain an indication of the problems involved in the construction and tests of small-scale (approximately 7-inch span) complete airplane configuration with internal air flow indicated that reliable zero-lift drag-coefficient measurements at Mach numbers up to 1.4 can be attained with such models, provided the model is constructed with a high but not an unreasonable degree of accuracy.
Howell, Robert R.↗
Deployment loads data from a free-flight investigation of all flexible parawings having 371.612 sq meters (4000 sq feet) of wing area
A free-flight test program to determine the deployment characteristics of all-flexible parawings was conducted. Both single-keel and twin-keel parawings having a wing area of 4000 square feet with a five-stage reefing system were tested by use of a bomb-type instrumented test vehicle. Several twin-keel-parawing tests were also made by using an instrumented controllable sled-type test vehicle. The systems were launched from either a C-130 or a C-119 carrier airplane, and a programer parachute was used to bring the test vehicle to a proper dynamic pressure and near-vertical flight path prior to deployment of the parawing system. The free-flight deployment loads data are presented in the form of time histories of individual suspension-line loads and total loads.
Croom, D. R.↗
The NASA Ames Hypervelocity Free Flight Aerodynamic Facility: Experimental Simulation of the Atmospheric Break-Up of Meteors
The Hypervelocity Free Flight Aerodynamic Facility at NASA Ames Research Center provides a potential platform for the experimental simulation of meteor breakup at conditions that closely match full-scale entry condition for select parameters. The poster describes the entry environment simulation capabilities of the Hypervelocity Free Flight Aerodynamic Facility (HFFAF) at NASA Ames Research Center and provides example images of the fragmentation of a hypersonic projectile for which break-up was initiated by mechanical forces (impact with a thin polymer diaphragm).
ballistic ranges↗
Space shuttle engineering and operations support. Separation operational limits for ALT free flights 1 through 5
The orbiter/SCA separation operational limits for the current target conditions of ALT free flights 1 through 5 are analyzed. The separation operational limits are used to verify that no separation design constraints are violated. The operational limits represent the acceptable dispersions in attainment of separation target conditions which assure safe separation. Safe separation is based on satisfying all specified separation design criteria except orbiter altitude at ALT interface airspeed. Separation operational limits are defined for each of the five orbiter tailcones on ALT free flight missions based upon preflight aerodynamics. The effect of carrier pilot steering compensation due to off-nominal flight conditions is determined to be within the separation operational limits.
Seale, R. H.↗
Free-Flight Experiments in LISA Pathfinder
The LISA Pathfinder mission will demonstrate the technology of drag-free test masses for use as inertial references in future space-based gravitational wave detectors. To accomplish this, the Pathfinder spacecraft will perform drag-free flight about a test mass while measuring the acceleration of this primary test mass relative to a second reference test mass. Because the reference test mass is contained within the same spacecraft, it is necessary to apply forces on it to maintain its position and attitude relative to the spacecraft. These forces are a potential source of acceleration noise in the LISA Pathfinder system that are not present in the full LISA configuration. While LISA Pathfinder has been designed to meet it's primary mission requirements in the presence of this noise, recent estimates suggest that the on-orbit performance may be limited by this 'suspension noise'. The drift-mode or free-flight experiments provide an opportunity to mitigate this noise source and further characterize the underlying disturbances that are of interest to the designers of LISA-like instruments. This article provides a high-level overview of these experiments and the methods under development to analyze the resulting data.
The technique of drag-free↗
Nitric oxide molecular tagging velocimetry of a free-flight model in a reflected shock tunnel
Nitric oxide molecular tagging velocimetry (NO MTV) is used to characterize the wake behind a free-flight spherical model in the test section of a free-piston reflected shock tunnel using a burst-mode laser operated at 100 kHz. A novel (to our knowledge) multi-delay timing scheme was implemented to measure velocity in a varying collisional environment in the wake of the free-flight model. Four simultaneous velocity profiles were measured in the wake of the model from -600 to 3600 m/s for flow enthalpies of 10.3 and 12.0 MJ/kg. Finally, the measured velocity distributions show good agreement when compared to computational fluid dynamics (CFD) modeling.
47 OTHER INSTRUMENTATION↗
Investigation of the free-flight characteristics and handling qualities of a ground-effect machine
Free flight characteristics and handling qualities of ground effect machine - Gem III stability
HANDLING QUALITY↗
Free-flight investigations of subliming ablators and transpiration cooling at hypersonic velocities
Free flight tests of subliming ablators and transpiration cooling as thermal protection at hypersonic speeds
EVAPORATION COOLING↗
A free flight investigation of transonic sting interference
Transonic sting interference has been studied in a supersonic wind tunnel to obtain free flight and sting support data on identical models. The two principal configurations, representing fuselage bodies, were cigar shaped with tail fins. The others were a sharp 10-deg cone, a sphere, and a blunt entry body. Comparative data indicated that the sting had an appreciable effect on drag for the fuselage-like configurations; drag rise occurred 0.02 Mach number earlier in free flight, and drag level was 15% greater. The spheres and the blunt bodies were insensitive to the presence of stings regardless of their size. The 10-deg cones were in between, experiencing no drag difference with a minimum diameter sting, but a moderate difference with the largest diameter sting tested. All data tend to confirm the notion that for the more slender bodies the sting not only affects flow but the forebody flow as well.
Jaffe, P.↗