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NASA NTRS1978

Effect of flow separation vortices on aircraft unsteady aerodynamics

The unsteady aerodynamic flow field over the space shuttle orbiter was studied. The results indicate at moderate to high angles of attack separation-induced vortices exact a dominating influence on the unsteady aerodynamics of the space shuttle orbiter and of high performance aircraft. The main characteristics are as follows: (1) The vortex-induced aerodynamic loads are large and highly nonlinear, sometimes discontinuous in character; and (2) the vortex-induced loads have opposite effects on static and dynamic stability characteristics. Analytic approximations are presented which can predict these vortex-induced aerodynamic effects with the accuracy needed for most engineering design.

Ericsson, L. E.↗

NASA NTRS2016

Development of Constraint Force Equation Methodology for Application to Multi-Body Dynamics Including Launch Vehicle Stage Seperation

The objective of this report is to develop and implement a physics based method for analysis and simulation of multi-body dynamics including launch vehicle stage separation. The constraint force equation (CFE) methodology discussed in this report provides such a framework for modeling constraint forces and moments acting at joints when the vehicles are still connected. Several stand-alone test cases involving various types of joints were developed to validate the CFE methodology. The results were compared with ADAMS(Registered Trademark) and Autolev, two different industry standard benchmark codes for multi-body dynamic analysis and simulations. However, these two codes are not designed for aerospace flight trajectory simulations. After this validation exercise, the CFE algorithm was implemented in Program to Optimize Simulated Trajectories II (POST2) to provide a capability to simulate end-to-end trajectories of launch vehicles including stage separation. The POST2/CFE methodology was applied to the STS-1 Space Shuttle solid rocket booster (SRB) separation and Hyper-X Research Vehicle (HXRV) separation from the Pegasus booster as a further test and validation for its application to launch vehicle stage separation problems. Finally, to demonstrate end-to-end simulation capability, POST2/CFE was applied to the ascent, orbit insertion, and booster return of a reusable two-stage-to-orbit (TSTO) vehicle concept. With these validation exercises, POST2/CFE software can be used for performing conceptual level end-to-end simulations, including launch vehicle stage separation, for problems similar to those discussed in this report.

Pamadi, Bandu N.↗

NASA NTRS1983

Effects of flow separation and cove leakage on pressure and heat-transfer distributions along a wing-cove-elevon configuration at Mach 6.9

External and internal pressure and cold-wall heating-rate distributions were obtained in hypersonic flow on a full-scale heat-sink representation of the space shuttle orbiter wing-elevon-cove configuration in an effort to define effects of flow separation on cove aerothermal environment as a function of cove seal leak area, ramp angle, and free-stream unit Reynolds number. Average free-stream Mach number from all tests was 6.9; average total temperature from all tests was 3360 R; free-stream dynamic pressure ranged from about 2 to 9 psi; and wing angle of attack was 5 deg (flow compression). For transitional and turbulent flow separation, increasing cove leakage progressively increased heating rates in the cove. When ingested mass flow was sufficient to force large reductions in extent of separation, increasing cove leakage reduced heating rates in the cove to those for laminar attached flow. Cove heating-rate distributions calculated with a method that assumed laminar developing channel flow agreed with experimentally obtained distributions within root-mean-square differences that varied between 11 and 36 percent where cove walls were parallel for leak areas of 50 and 100 percent.

Deveikis, W. D.↗

NASA NTRS1985

Filament wound data base development, revision 1

The objective was to update the present Space Shuttle Solid Rocket Booster (SRB) baseline reentry aerodynamic data base and to develop a new reentry data base for the filament wound case SRB along with individual protuberance increments. Lockheed's procedures for performing these tasks are discussed. Free fall of the SRBs after separation from the Space Shuttle Launch Vehicle is completely uncontrolled. However, the SRBs must decelerate to a velocity and attitude that is suitable for parachute deployment. To determine the SRB reentry trajectory parameters, including the rate of deceleration and attitude history during free-fall, engineers at Marshall Space Flight Center are using a six-degree-of-freedom computer program to predict dynamic behavior. Static stability aerodynamic coefficients are part of the information required for input into this computer program. Lockheed analyzed the existing reentry aerodynamic data tape (Data Tape 5) for the current steel case SRB. This analysis resulted in the development of Data Tape 7.

Sharp, R. Scott↗

NASA NTRS2017

Building Aerodynamic Databases for the SLS Design Process

NASA's new Space Launch System (SLS) will be the first rocket since the Saturn V (1967-1973) to carry astronauts beyond low earth orbit-and will carry 10% more payload than Saturn V and three times the payload of the space shuttle. The SLS configuration consists of a center core and two solid rocket boosters that separate from the core as their fuel is exhausted two minutes after lift-off. During these first two minutes of flight, the vehicle powers its way through strong shock waves as it accelerates past the speed of sound, then pushes beyond strong aerodynamic loads at the maximum dynamic pressure, and is ultimately enveloped by gaseous plumes from the booster-separation motors. The SLS program relies on computational fluid dynamic (CFD) simulations to provide much of the data needed to build aerodynamic databases describing the structural load distribution, surface pressures, and aerodynamic forces on the vehicle.

Aerodynamic↗

NASA NTRS1988

Turbomachinery rotor forces

The fluid-induced forces, both steady and unsteady, acting upon an impeller of a centrifugal pump, and impeller blade-diffuser vane interaction in centrifugal pumps with vaned radial diffusers were evaluated experimentally and theoretically. Knowledge of the steady and unsteady forces, and the associated rotordynamic coefficients are required to effectively model the rotor dynamics of the High Pressure Fuel Turbopump (HPFTP) of the Space Shuttle Main Engine (SSME). These forces and rotordynamic coefficients were investigated using different impellers in combination with volutes and vaned diffusers, and axial inducers. These rotor forces are global. Local forces and pressures are also important in impeller-diffuser interaction, for they may cause cavitation damage and even vane failures. Thus, in a separate investigation, impeller wake, and impeller blade and diffuser vane pressure measurements were made. The nature of the rotordynamic forces is discussed, the experimental facility is described, and the measurements of unsteady forces and pressure are reported together with a brief and incomplete attempt to calculate these flows.

Arndt, Norbert↗

NASA NTRS2008

Ares I-X Flight Test - The Future Begins Here

In less than two years, the National Aeronautics and Space Administration (NASA) will launch the Ares I-X mission. This will be the first flight of the Ares I crew launch vehicle, which, together with the Ares V cargo launch vehicle, will eventually send humans to the Moon, Mars, and beyond. As the countdown to this first Ares mission continues, personnel from across the Ares I-X Mission Management Office (MMO) are finalizing designs and fabricating vehicle hardware for an April 2009 launch. This paper will discuss the hardware and programmatic progress of the Ares I-X mission. Like the Apollo program, the Ares launch vehicles will rely upon extensive ground, flight, and orbital testing before sending the Orion crew exploration vehicle into space with humans on board. The first flight of Ares I, designated Ares I-X, will be a suborbital development flight test. Ares I-X gives NASA its first opportunity to gather critical data about the flight dynamics of the integrated launch vehicle stack; understand how to control its roll during flight; better characterize the severe stage separation environments that the upper stage engine will experience during future operational flights; and demonstrate the first stage recovery system. NASA also will begin modifying the launch infrastructure and fine-tuning ground and mission operations, as the agency makes the transition from the Space Shuttle to the Ares/Orion system.

Davis, Stephan R.↗

NASA NTRS1978

Solution of the subsynchronous whirl problem in the high-pressure hydrogen turbomachinery of the Space Shuttle Main Engine

Subsynchronous whirl of the high-pressure fuel turbopump limited operation of the Space Shuttle Main Engine for some months in early 1976. The means by which this problem was successfully attacked is of particular interest to the rotor-dynamics community, not only because this machinery was the highest power-to-weight ratio known (77,000 hp...760 pounds), but because of the multiple forcing functions involved and the means, both analytical and experimental, which were utilized in separating variables, pointing toward successful solutions, and evaluating results. The general means of identifying fundamental characteristics, analyzing data, and conducting computer investigations are delineated. The results of analysis and testing are discussed. Since whirl inception occurs at a shaft speed greater than twice the first system critical, this was increased by stiffening the shaft and bearing supports; the system damping and system stiffness was additionally increased by proper interstage seal design to the extent that the instability threshold is now beyond the operating range.

Ek, M. C.↗

NASA NTRS2000

Use of Several Thermal Analysis Techniques to Study the Cracking of an Nitrile Butadiene Rubber (NBR) Insulator on the Booster Separation Motor (BSM) of the Space Shuttle

Two different vendor rubber formulations have been used to produce the silica-filled NBR insulators for the BSM used on both of the Solid Rocket Boosters (SRBs) of the Space Shuttle. A number of lots of the BSM insulator in 1998-99 exhibited surface cracks and/or crazing. Each insulator is bonded to the BSM aluminum aft closure with an epoxy adhesive. Induced insulator stresses from adhesive cure are likely greatest where the insulator/adhesive contour is the greatest, thus showing increased insulator surface cracking in this area. Thermal analysis testing by Dynamic Mechanical Analyzer (DMA) and Thermomechanical Analysis (TMA) was performed on one each of the two vendor BSM insulators previously bonded that exhibited the surface cracking. The TMA data from the film/fiber technique yielded the most meaningful results, with thin insulator surface samples containing cracks having roughly the same modulus (stiffness) as thin insulator bulk samples just underneath.

Wingard, Charles D.↗

NASA NTRS1986

The dynamics of a space station tethered refueling facility

The fluid stored in a tethered orbital refueling facility is settled at the bottom of the storage tanks by gravity-gradient forces. The fluid motions (slosh) induced by outside disturbances must be limited to ensure the tank outlet is not uncovered during a fluid transfer. The dynamics of a LO2/LH2 TORF attached to the space station have been analyzed to identify design parameters necessary to limit fluid motion. Using the worst case disturbance of a shuttle docking at the space station, the fluid motion was found to be a function of tether length and allowable facility swing angle. Acceptable fluid behavior occurs for tether lengths of at least 1000 ft. To ensure motions induced by separate disturbances do not add to unacceptable values, a slosh damping coefficient of 5 percent is recommended.

Abbott, P.↗

NASA NTRS1996

Receiver Design, Performance Analysis, and Evaluation for Space-Borne Laser Altimeters and Space-to-Space Laser Ranging Systems

This progress report consists of two separate reports. The first one describes our work on the use of variable gain amplifiers to increase the receiver dynamic range of space borne laser altimeters such as NASA's Geoscience Laser Altimeter Systems (GLAS). The requirement of the receiver dynamic range was first calculated. A breadboard variable gain amplifier circuit was made and the performance was fully characterized. The circuit will also be tested in flight on board the Shuttle Laser Altimeter (SLA-02) next year. The second report describes our research on the master clock oscillator frequency calibration for space borne laser altimeter systems using global positioning system (GPS) receivers.

Davidson, Frederic M.↗

NASA NTRS1987

Numerical modeling of on-orbit propellant motion resulting from an impulsive acceleration

In-space docking and separation maneuvers of spacecraft that have large fluid mass fractions may cause undesirable spacecraft motion in response to the impulsive-acceleration-induced fluid motion. An example of this potential low gravity fluid management problem arose during the development of the shuttle/Centaur vehicle. Experimentally verified numerical modeling techniques were developed to establish the propellant dynamics, and subsequent vehicle motion, associated with the separation of the Centaur vehicle from the shuttle orbiter cargo bay. Although the shuttle/Centaur development activity was suspended, the numerical modeling techniques are available to predict on-orbit liquid motion resulting from impulsive accelerations for other missions and spacecraft.

Aydelott, John C.↗

NASA NTRS1986

Numerical modeling of on-orbit propellant motion resulting from an impulsive acceleration

In-space docking and separation maneuvers of spacecraft that have large fluid mass fractions may cause undersirable spacecraft motion in response to the impulsive-acceleration-induced fluid motion. An example of this potential low gravity fluid management problem arose during the development of the shuttle/Centaur vehicle. Experimentally verified numerical modeling techniques were developed to establish the propellant dynamics, and subsequent vehicle motion, associated with the separation of the Centaur vehicle from the shuttle orbiter cargo bay. Although the shuttle/Centaur development activity was suspended, the numerical modeling techniques are available to predict on-orbit liquid motion resulting from impulsive accelerations for other missions and spacecraft.

Aydelott, John C.↗

NASA NTRS1994

On-Orbit Propellant Motion Resulting from an Impulsive Acceleration

In-space docking and separation maneuvers of spacecraft that have large fluid mass fractions may cause undesirable spacecraft motion in response to the impulsive-acceleration-induced fluid motion. An example of this potential low-gravity fluid management problem arose during the development of the shuttle/Centaur vehicle. Experimentally verified numerical modeling techniques were developed to establish the propellant dynamics, and subsequent vehicle motion, associated with the separation of the Centaur vehicle from the shuttle cargo bay. Although the shuttle/Centaur development activity has been suspended, the numerical modeling techniques are available to predict on-orbit liquid motion resulting from impulsive accelerations for other missions and spacecraft.

Hochstein, John I.↗

NASA NTRS1990

Flight mechanics applications for tethers in space: Cooperative Italian-US programs

Since the 1974 proposal by Giuseppe Colombo to fly a tethered subsatellite from the Shuttle Orbiter, the creative thinking of many scientists and engineers from Italy and U.S. has generated a broad range of potential tether applications in space. Many of these applications have promise for enabling innovative research and operational activities relating to flight mechanics in earth orbit and at suborbital altitudes. From a flight mechanics standpoint the most interesting of the currently proposed flight demonstrations are: the second Tethered Satellite System experiment which offers both the potential for aerothermodynamics and hypersonics research and for atmospheric science research; the Tethered Initiated Space Recovery System which would enable orbital deboost and recovery of a re-entry vehicle and waste removal from a space station; and the Tether Elevator/Crawler System which would provide a variable microgravity environment and space station center of mass management. The outer atmospheric and orbital flight mechanics characteristics of these proposed tether flight demonstrations are described. The second Tethered Satellite System mission will deploy the tethered satellite earthward and will bring it as low as 130 km from ground and thus into the transition region between the atmosphere (non-ionized) and the partially ionized ionosphere. The atmospheric flight mechanics of the tethered satellite is discussed and simulation results are presented. The Tether Initiated Space Recovery System experiment will demonstrate the ability of a simple tether system to deboost and recover a reentry vehicle. The main feature of this demonstration is the utilization of a Small Expendable Deployment System (SEDS) and the low-tension deployment assumed to separate the reentry vehicle from the Shuttle. This low-tension deployment maneuver is discussed and its criticalities are outlined. The Tether Elevator/Crawler System is a new space element able to move in a controlled way between the ends of a deployed tethered system. A Shuttle test of an Elevator model is planned to demonstrate the unique capability of this element as a microgravity facility and to test the transfer motion control. The basic dynamical features of the Elevator system are presented and a preliminary assessment of the Elevator-induced tether vibrations is discussed.

Bevilacqua, Franco↗

NASA NTRS2009

Ares I-X Overview

The Ares I-X flight test is the first development flight of the Ares I crew launch vehicle. This mission, first conceived in 2006, will be launching later in 2009. Its primary mission objectives will be to demonstrate flight and roll control of a dynamically similar vehicle, perform a separation event and measure its shock effects, stack and recover a first stage booster, and demonstrate ground operations. All of the primary flight test vehicle s hardware is at Kennedy Space Center, and is being stacked in the Vehicle Assembly Building for a liftoff at Launch Complex 39B. Mission hardware specific to Ares I-X also is being installed at Launch Complex 39, which has been supporting Space Shuttle operations. This presentation will provide a status and preview of the upcoming mission.

Davis, Stephan R.↗

NASA NTRS1999

Use of Several Thermal Analysis Techniques to Study the Cracking of a Nitrile Butadiene Rubber (NBR) Insulator on the Booster Separation Motor (BSM) of the Space Shuttle

Two different vendor rubber formulations have been used to produce the silica-filled NBR insulators for the BSM of each of the two Solid Rocket Boosters (SRBs) on the Space Shuttle. Each cured insulator is bonded to the BSM aluminum aft closure with an epoxy adhesive, and some of the curved areas in the rubber may have significant residual stresses. A number of recently bonded NBR insulators have shown fine surface cracks, and stressed insulator areas may be aging at a faster rate than unstressed areas, thus hastening the surface cracking. Thermal analysis data on both vendor insulators by Dynamic Mechanical Analysis (DMA) through a temperature/frequency sweep from 24 to 74 C have shown a higher flexural storage modulus and Arrhenius activation energy for the stressed area than for the unstressed area. Other thermal analysis techniques are being used to study the insulator surface vs. bulk interior for better understanding this anomaly.

Wingard, Charles D.↗

NASA NTRS1977

The effects of flow separation on shuttle dynamics and aeroelastic stability

The effects of flow separation on the dynamic and aeroelastic stability of various shuttle configurations have been investigated. Flow separation is shown to affect the aeroelastic stability of the 747/Orbiter yaw modes, the orbiter dynamic stability and possibly the aeroelastic stability of the wing torsional mode, and to dominate both the dynamic and aeroelastic stability of the launch configuration. Limit cycle oscillations of certain launch configuration modes are the result of sudden flow separation. The limit cycle oscillations threaten the structural integrity in two ways: (1) by outright overstressing of the structure due to large modal deflection, (2) by fatigue due to the continued flexing of the structure. Fatigue is a more significant consideration for the reusable (100 flights) shuttle than it has been for previous space boosters.

Reding, J. P.↗