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NASA NTRSDate not supplied

Liftoff Environments

A Launch Environment, or Liftoff Environment, fundamentally represents a source of loading during the hold-down or liftoff phase of a rocket launch. A launch vehicle is subjected to transient and oscillatory pressure loading on its exterior surfaces induced by engines and boosters during vehicle hold-down and liftoff. These pressure loads are a principal source of structural vibration which may result in the malfunction of vehicle components or the fatigue of exterior skin panels or component brackets. Additionally, the pressure loading gives rise to sound pressure levels inside the crew cabin which may impact the crew's health, safety, or ability to communicate. Liftoff Environments can have a significant impact on the launch vehicle or surrounding structures. For SLS, there are eight primary environments supported by the Liftoff Environments team. These are Liftoff Acoustics (LOA), Hold-down Acoustics (HDA), RS-25 Nozzle Flow Transient (NFT) Acoustics, Booster Ignition Overpressure (IOP) & Duct Overpressure (DOP), Igniter Shock, Core Stage Engine (CSE) Overpressure, Excess Hydrogen (H2) Pop, and Infrasonic Acoustics. These can be split generally into acoustics, which are sustained stationary events, and transients, which are short duration nonstationary events.

Matthew J Casiano↗
NASA NTRS2004

Vibration Isolation for Launch of a Space Station Orbital Replacement Unit

Delivery of Orbital Replacement Units (ORUs) to on-orbit destinations such a the International Space Station (ISS) and the Hubble Space Telescope is an important component of the space program. ORUs are integrated on orbit with space assets to maintain and upgrade functionality. For ORUs comprised of sensitive equipment, the dynamic launch environment drives design and testing requirements, and high frequency random vibrations are generally the cause for failure. Vibration isolation can mitigate the structure-borne vibration environment during launch, and hardware has been developed that can provide a reduced environment for current and future launch environments. Random vibration testing of one ORU to equivalent Space Shuttle launch levels revealed that its qualification and acceptance requirements were exceeded. An isolation system was designed to mitigate the structure-borne launch vibration environment. To protect this ORU, the random vibration levels at 50 Hz must be attenuated by a factor of two and those at higher frequencies even more. Design load factors for Shuttle launch are high, so a metallic load path is needed to maintain strength margins. Isolation system design was performed using a finite element model of the ORU on its carrier with representative disturbance inputs. Iterations on the modelled to an optimized design based on flight proven SoftRide MultiFlex isolators. Component testing has been performed on prototype isolators to validate analytical predictions.

Maly, Joseph R.↗
NASA NTRS2003

Scale Model Experiments on Sound Propagation From a Mach 2.5 Cold Nitrogen Jet Flowing Through a Rigid-Walled Duct With a J-Deflector

The Launch Systems Testbed (LST) represents the evolution of vibroacoustics research and development work performed at NASA John F. Kennedy Space Center (KSC) over the last 15 years. The LST is located at the Launch Equipment Test Facility (LETF) in the KSC industrial complex. The LETF is operated by Sierra Lobo, Inc., as a member of University-Affiliated Technology Development Contract (USTDC) to KSC Spaceport and Engineering and Technology Directorate (YA), with ASRC Aerospace Corporation as a the prime contractor. Trajectory Simulation Mechanism (TSM) is a major component of the LST, developed specifically to simulate nonstationary acoustic loads on launch pad structures, vehicles, and payloads. TSM enhances the capabilities within LST for simulating launch environments of future vehicles. The scaled launch environments will be used to predict the full-scale launch environment via an appropriate scaling procedure. Air Force Research Laboratory (AFRL) has tasked NASA KSC to perform a basic technology test program in support of developing a low-cost clean pad (incorporating passive mitigation techniques) for future launch vehicles. The overall goal of the program is to develop innovative launch exhaust management systems, which effectively reduce launch acoustic environment with innovative duct designs, while eliminating traditional sound suppression water systems. Passive techniques, such as nontraditional duct geometries, resonators, and diffusers, etc., will be investigated. The overall goals are to advance innovative concepts for a clean pad while developing ideas to reduce transmitted sound via investigation and modeling of jet exhaust acoustic and flow field characteristics. The series of tests outlined in this report represent baseline tests and are geared towards defining the acoustic load environment on the TSM pad for open and closed duct configurations. This report summarizes the cold jet acoustic testing for Mach 2.5 supersonic nitrogen jet issuing from a nozzle with 1-inch exit diameter. Acoustic data, including spectral sound power and Overall Sound Pressure Level (OASPL), are obtained both for a free jet and with the jet flowing through a rigid-walled duct with a J-deflector. The relative performance of closed duct and open duct is evaluated. The results show that the closed duct is superior to the partially open duct, and results in about 3-decibel (dB) noise reduction (near the duct axis) relative to the free jet. The location of the nozzle exit plane (NEP) relative to the duct inlet plane (DIP) has a significant effect on the acoustic field. The results suggest that the location of NEP at 10 inches above the DIP results in reduced acoustic loads relative to 5 inches above the duct inlet and 1 inch into the duct inlet.

Kandula, Max↗
NASA NTRS2012

Verification of Ares I Liftoff Acoustic Environments via the Ares Scale Model Acoustic Test

Launch environments, such as Liftoff Acoustic (LOA) and Ignition Overpressure (IOP), are important design factors for any vehicle and are dependent upon the design of both the vehicle and the ground systems. The NASA Constellation Program had several risks to the development of the Ares I vehicle linked to LOA which are used in the development of the vibro-acoustic environments. The risks included cost, schedule and technical impacts for component qualification due to high predicted vibro-acoustic environments. One solution is to mitigate the environment at the component level. However, where the environment is too severe to mitigate at the component level, reduction of the launch environments is required. The Ares I Scale Model Acoustic Test (ASMAT) program was implemented to verify the predicted Ares I launch environments and to determine the acoustic reduction for the LOA environment with an above deck water sound suppression system. The test article included a 5% scale Ares I vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 200 instruments. The ASMAT results are compared to the Ares I LOA predictions and water suppression effectiveness results are presented.

Counter, Douglas D.↗
NASA NTRS2012

Verification of Ares I Liftoff Acoustic Environments via the Ares I Scale Model Acoustic Test

Launch environments, such as Liftoff Acoustic (LOA) and Ignition Overpressure (IOP), are important design factors for any vehicle and are dependent upon the design of both the vehicle and the ground systems. The NASA Constellation Program had several risks to the development of the Ares I vehicle linked to LOA which are used in the development of the vibro-acoustic environments. The risks included cost, schedule and technical impacts for component qualification due to high predicted vibro-acoustic environments. One solution is to mitigate the environment at the component level. However, where the environment is too severe to mitigate at the component level, reduction of the launch environments is required. The Ares I Scale Model Acoustic Test (ASMAT) program was implemented to verify the predicted Ares I launch environments and to determine the acoustic reduction for the LOA environment with an above deck water sound suppression system. The test article included a 5% scale Ares I vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 200 instruments. The ASMAT results are compared to the Ares I LOA predictions and water suppression effectiveness results are presented.

Counter, Douglas D.↗
NASA NTRS2005

The Standard Deviation of Launch Vehicle Environments

Statistical analysis is used in the development of the launch vehicle environments of acoustics, vibrations, and shock. The standard deviation of these environments is critical to accurate statistical extrema. However, often very little data exists to define the standard deviation and it is better to use a typical standard deviation than one derived from a few measurements. This paper uses Space Shuttle and expendable launch vehicle flight data to define a typical standard deviation for acoustics and vibrations. The results suggest that 3dB is a conservative and reasonable standard deviation for the source environment and the payload environment.

Yunis, Isam↗
NASA NTRSDate not supplied

Leveraging Large Eddy Simulations to Characterize Aeroacoustic Environments on Launch Vehicles

NASA's Space Launch System (SLS) program has relied on multiple wind tunnel campaigns to predict expected aeroacoustic environments. Time, cost, Reynolds number matching, contamination from test section acoustics, and limitations in spatial resolution are all factors that impact the use experimental data for development of launch vehicle environments. Methodological and computational advances over the last decade are enabling scale resolving computational fluid dynamics (CFD) simulations to be completed that can address some the challenges with conventional datasets, enabling more complete/accurate modeling of dynamic loading events on ascent. These simulations are classified as so-called "Large-Eddy Simulations" (LES). As the name implies, these simulations seek to directly resolve the turbulence in the largest, most-energetic turbulent structures, or eddies, and the dissipation of the smallest eddies in the flow field, is modeled. Like anything else, these simulations still must undergo rigorous testing and validation for the results to ultimately be trusted in the analysis of a launch vehicle. EV33 has begun to conduct some of this early-stage testing and validation to better support NASA missions in the future.

Jonathan Boustani↗
NASA NTRS1990

Atmospheric Environment for Space Shuttle (STS-28) Launch

A summary is presented of selected atmospheric conditions observed near Space Shuttle STS-28 launch time on August 8, 1989. STS-28 carried a Department of Defense payload and the flight azimuth is denoted by a reference flight azimuth, since the actual flight azimuth is not known. Values of ambient pressure, temperature, moisture, ground winds, visual observations (cloud), and winds aloft are included. The sequence of prelaunch Jimsphere-measured vertical wind profiles is given. The final atmospheric tape, which consists of wind and thermodynamic parameters versus altitude, for STS-28 vehicle ascent was constructed and represents the best estimate of the launch environment to 400,000 ft altitude that was traversed by the STS-28 vehicle. The STS-28 ascent atmospheric data tape was constructed by Marshall Space Flight Center's Earth Science and Applications Division to provide an internally consistent data set for use in post-flight performance assessments.

Jasper, G. L.↗
NASA NTRS1990

Atmospheric environment for space shuttle (STS-33) launch

A summary is presented of selected atmospheric conditions observed near space shuttle STS-33 at launch time. STS-33 carried a DOD payload and the flight azimuth is denoted by a reference flight azimuth, since the actual flight azimuth is not known. Values of ambient pressure, temperature, moisture, ground winds, visual observations (clouds), and winds aloft are included. The sequence of pre-launch Jimsphere measured vertical wind profiles is given. The final atmospheric tape, which consists of wind and thermodynamic parameters versus altitude, for STS-33 vehicle ascent, was constructed. The STS-33 ascent atmospheric data tape was constructed by NASA-Marshall to provide an internally consistent data set for use in postflight performance assessments and represents the best estimates of the launch environment to the 400,000 ft altitude that was traversed by the STS-33 vehicle.

Jasper, G. L.↗
NASA NTRS1990

Atmospheric environment for Space Shuttle (STS-32) launch

A summary of selected atmospheric conditions observed near space shuttle STS-32 launch time on January 9, 1990, at Kennedy Space Center, Florida, are presented. Values of ambient pressure, temperature, moisture, ground winds, visual observations (clouds), and winds aloft are included. The sequence of pre-launch Jimsphere-measured vertical wind profiles is also presented. The final atmospheric tape, which consists of wind and thermodynamic parameters versus altitude, for STS-32 vehicle ascent was constructed. The STS-32 ascent atmospheric data tape was constructed to provide an internally consistent data set for use in postflight performance assessments and represents the best estimate of the launch environment that was traversed by the STS-32 vehicle.

Jasper, G. L.↗
NASA NTRS1990

Atmospheric environment for Space Shuttle (STS-31) launch

A summary of selected atmospheric conditions observed near space shuttle STS-31 launch time on April 24, 1990, at Kennedy Space Center, Florida, are presented. Values of ambient pressure, temperature, moisture, ground winds, visual observations (clouds), and winds aloft are included. The sequence of pre-launch Jimsphere-measured vertical wind profiles is also presented. The final atmospheric tape, which consists if wind and thermodynamic parameters versus altitude, for STS-31 vehicle ascent was constructed. The STS-31 ascent atmospheric data tape was constructed to provide an internally consistent data set for use in postflight performance assessments and represent the best estimated of the launch environment to the 400,000 feet altitude that was traversed by the STS-31 vehicle.

Jasper, G. L.↗
NASA NTRS1990

Atmospheric environment for space shuttle (STS-36) launch

A summary of selected atmospheric conditions observed near space shuttle STS-36 launch time on February 28, 1990, at Kennedy Space Center, Florida was presented. STS-36 carried a Department of Defense payload and the flight azimuth is not known. Values of ambient pressure, temperature, moisture, ground winds, visual observations (cloud), and winds aloft are included. The sequence of pre-launch Jimsphere-measured vertical wind profiles is given. The final atmospheric tape, which consists of wind and thermodynamic parameters versus altitude, for STS-36 vehicle ascent was constructed. The STS-36 ascent atmospheric data tape was constructed to provide an internally consistent data set for use in postflight performance assessments and represent the best estimate of the launch environment to the 400,000 feet altitude that was traversed by the STS-36 vehicle.

Jasper, G. L.↗
NASA NTRS1989

Atmospheric environment for space shuttle (STS-34) launch

A summary of selected atmospheric conditions observed near space shuttle STS-34 launch time on October 18, 1989, at Kennedy Space Center, Florida is presented. Values of ambient pressure, temperature, moisture, ground winds, visual observations (clouds), and winds aloft are included. The sequence of pre-launch Jimsphere-measured vertical wind profiles is given. The final atmospheric tape, which consists of wind and thermodynamic parameters vs. altitude, for STS-34 vehicle ascent was constructed to provide an internally consistent data set for use in post-flight performance assessments. It represents the best estimates of the launch environment to the 400,000 feet altitude that was traversed by the STS-34 vehicle.

Jasper, G. L.↗