Search

The Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Small Explorer X-ray astrophysics mission being implemented by a geographically dispersed team. The IXPE collaboration and Observatory complexity provide both unique challenges and advantages for Project V&V. A rigorous and iterative V&V process is essential to ensuring the successful realization of reliable and cost effective IXPE Mission System. The IXPE verification, validation and characterization (V&V) process starts at the component/unit level and rolls up to appropriate higher levels. V&V compliance is assured by collaborative development by the V&V Team which spans all project organizations. The V&V process provides a framework, with appropriate confidence, to show that all needs and expectations are met by the as-built system. Proof is in the form of traceable detailed evidence of compliance at every level rolling up to and including the overall system and architecture levels. The detailed verification approach for IXPE components/units/subassemblies/subsystems is the responsibility of the applicable subsystem RE supported by systems and the I&T team. All verification processes, analyses and steps are documented. IXPE is using a V&V threads process which is ideal for use in showing compliance when a requirements set is dependent on a complex set of actions/processes. It's a system engineering graphics method to ensure all ‘contributors’ and ‘influencers’ are included. When applicable, verification threads are provided to support the verification compliance/sell-off process. This paper summarizes the IXPE mission and describes the verification, validation and characterization activities planned for the IXPE mission including the use of V&V threads.

The goal of the Imaging X-Ray Polarimetry Explorer (IXPE) Mission is to expand understanding of high-energy astrophysical processes and sources, in support of NASA's first science objective in Astrophysics: “Discover how the universe works.” Polarization uniquely probes astrophysical anisotropies — ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin — that are not otherwise measurable. IXPE will conduct X-ray polarimetry for multiple categories of cosmic X-ray sources that are likely to be polarized such as neutron stars, stellar-mass black holes, supernova remnants and active galactic nuclei. The IXPE Observatory consists of Spacecraft and Payload modules built up in parallel to form the Observatory during system integration and test. The Payload includes three polarization-sensitive, X-ray detectors, each paired with its corresponding grazing incidence mirror module assembly (MMA). A deployable boom provides the correct separation (focal length) between the detector units (DU) and MMAs. These Payload elements are supported by the IXPE Spacecraft which is derived from the BCP-100 small Spacecraft architecture. This paper summarizes the IXPE mission science objectives, describes the Observatory implementation concept including the payload and spacecraft elements and summarizes the expected concept of operations.

The Imaging X-ray Polarimetry Explorer (IXPE) is a space-based observatory that will have the capability to measure the polarization of X-rays from astrophysical sources. IXPE will improve sensitivity over OSO-8, the only previous X-ray polarimeter, by two orders of magnitude in required exposure time. IXPE will yield insight into our understanding of X-ray production in objects such as neutron stars as well as stellar and supermassive black holes. IXPE measurements will provide new dimensions for probing a wide range of cosmic X-ray sources — including active galactic nuclei (AGN) and microquasars, pulsars and pulsar wind nebulae, magnetars, accreting X-ray binaries, supernova remnants, and the Galactic center. Addressing NASA's Science Mission Directorate's science goal “to probe the origin and destiny of our universe, including the nature of black holes, dark energy, dark matter, and gravity.” IXPE will introduce the capability for X-ray polarimetric imaging, uniquely enabling the measurement of X-ray polarization with scientifically meaningful spatial, spectral, and temporal resolution. These polarization measurements will help answer fundamental questions regarding 1) the geometries of the flows, emission regions, and magnetic fields, 2) the physical process that lead to particle acceleration and X-ray emission, and 3) the physical effects of gravitational, electric, and magnetic fields at their extreme limits. This scientific mission, IXPE, is being developed by the NASA Marshall Space Flight Center (MSFC), Ball Aerospace, the Italian Space Agency (ASI), the Institute for Space Astrophysics and Planetology (IAPS)/ National Institute of Astrophysics (INAF), the National Institute for Nuclear Physics (INFN), the University of Colorado Laboratory for Atmospheric and Space Physics (LASP), Stanford University, McGill University, and the Massachusetts Institute of Technology. The IXPE partners each provide unique capabilities and experience which are utilized to design, build and launch the IXPE observatory resulting in the collection of on-orbit scientific data measurements which are transmitted to ground stations and analyzed. The established systems engineering (SE) methods and teaming approach to achieve the IXPE mission goals will be discussed. For this paper, the focus is the IXPE observatory and the collaboration of NASA MSFC, Ball Aerospace and IAPS/INAF. Our current focus is on requirements development and analysis along with definition of the interface control documents (ICD). Of particular note are requirements and ICDs between major flight elements and between organizations. This paper will describe the SE philosophy being used to ensure complete inter-organizational understanding and agreement as the Project moves towards SRR in September 2017 and PDR in June 2018. Current status and future milestones will be discussed.

During the study and development of NASA space vehicles, acoustic environments have been a critical design input. This paper surveys some of the key challenges and focuses on the contributions and collaborations of Kenneth J. Plotkin/Wyle Laboratories with various NASA centers and personnel. In the mid-1960’s and early 1970’s, a method for predicting in-flight fluctuating environments for vehicle systems was developed for the Saturn Development Programs at NASA Marshall Space Flight Center (MSFC). With the Space Shuttle Vehicle development in the 1970’s, sonic boom became a concern and sonic boom focusing was studied. Attention was turned to the Space Shuttle Orbiter entry maneuvers during the approach to the KSC landing site. In 1993, a PC version for sonic boom prediction was developed for the National Launch System study. Near-field pressure data from computational fluid dynamics analyses were used to develop the shape factors used in the X-33 sonic boom analyses. For the X-34 sonic boom analyses, the ...

As a patient’s end-of-life approaches, it is typical for the disease to be the focus of treatment instead of the dying patient. There is limited congruence between the care preferred by patients and the treatment actually delivered to patients during their end-of-life. The Physician Orders for Life-Sustaining Treatment Paradigm has been endorsed or is in development in all but three states and the District of Columbia in an effort to ensure that patients are provided with adequate opportunities to specify their end-of-life care preferences. However, most states are using paper forms to document these preferences which may be inaccessible when needed. We have developed an electronic end-of-life care registry that allows authorized users to store and retrieve information pertaining to patients’ end-of-life care preferences. In this paper, we describe (a) the requirements identified for the registry from the users’ perspective and (b) the design and development of the electronic registry.

The liftoff phase induces high acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are used in the prediction of the internal vibration responses of the vehicle and components. There arises the question about time equivalent (Teq) duration of the liftoff phase and similarity to other launch vehicles. Vibroacoustic engineers require the fatigue-weighted time duration values for qualification testing inputs. In order to determine the Teq for the Space Launch System, NASA's newest launch vehicle, the external microphone data from the Exploration Flight Test 1 (EFT-1) flight of the Orion Multi-Purpose Crew Vehicle (MPCV) was evaluated. During that evaluation, a trend was observed in the data and the origin of that trend is discussed in this paper. Finally, the Teq values for the EFT-1 Orion MPCV are presented.

The value of the International Space Station (ISS) as a premier microgravity environment is currently at risk due to structure-borne vibration. The vibration sources are varied and include crew activities such as exercising or simply moving from module to module, and electro- mechanical equipment such as fans and pumps. Given such potential degradation of usable microgravity, anything that can be done to dampen vibration on-orbit will significantly benefit microgravity users. Most vibration isolation schemes, both active and passive, have proven to be expensive - both operationally and from the cost of integrating isolation systems into primary/secondary structural interfaces (e.g., the ISS module/rack interface). Recently, passively absorptive materials have been tested at the bolt interfaces between the operating equipment and support structure (secondary/tertiary structural interfaces). The results indicate that these materials may prove cost-effective in mitigating the vibrational problems of the ISS. We report herein tests of passive absorbers placed at the interface of a vibration-inducing component: the Development Distillation Assembly, a subassembly of the Urine Processing Assembly, which is a rotating centrifuge and cylinder assembly attached to a mounting plate. Passive isolators were installed between this mounting plate and its support shelf. Three materials were tested: BISCO HT-800, Sorbothane 30 and Sorbothane 50, plus a control test with a hard shim. In addition, four distinct combinations of the HT-800 and Sorbothane 50 were tested. Results show a significant (three orders of magnitude) reduction of transmitted energy, as measured in power spectral density (PSD), using the isolation materials. It is noted, however, that passive materials cannot prevent the transmission of very strong forces or absorb the total energy induced from structural resonances.

The liftoff phase induces high acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are used in the prediction of the internal vibration responses of the vehicle and components. Present liftoff vehicle acoustic environment prediction methods utilize stationary data from previously conducted hold-down tests to generate 1/3 octave band Sound Pressure Level (SPL) spectra. In an effort to update the accuracy and quality of liftoff acoustic loading predictions, non-stationary flight data from the Ares I-X were processed in PC-Signal in two flight phases: simulated hold-down and liftoff. In conjunction, the Prediction of Acoustic Vehicle Environments (PAVE) program was developed in MATLAB to allow for efficient predictions of sound pressure levels (SPLs) as a function of station number along the vehicle using semi-empirical methods. This consisted of generating the Dimensionless Spectrum Function (DSF) and Dimensionless Source Location (DSL) curves from the Ares I-X flight data. These are then used in the MATLAB program to generate the 1/3 octave band SPL spectra. Concluding results show major differences in SPLs between the hold-down test data and the processed Ares I-X flight data making the Ares I-X flight data more practical for future vehicle acoustic environment predictions.

In recent years, advances in research and engineering have led to more powerful launch vehicles which yield acoustic environments potentially destructive to the vehicle or surrounding structures. Therefore, it has become increasingly important to be able to predict the acoustic environments created by these vehicles in order to avoid structural and/or component failure. The current industry standard technique for predicting launch-induced acoustic environments was developed by Eldred in the early 1970's. Recent work has shown Eldred's technique to be inaccurate for current state-of-the-art launch vehicles. Due to the high cost of full-scale and even sub-scale rocket experiments, very little rocket noise data is available. Much of the work thought to be applicable to rocket noise has been done with heated jets. A model to predict the acoustic environment due to a launch vehicle in the far-field was created. This was done using five sets of horizontally fired rocket data, obtained between 2008 and 2012. Through scaling analysis, it is shown that liquid and solid rocket motors exhibit similar spectra at similar amplitudes. This model is accurate for these five data sets within 5 dB of the measured data.

Launch environments, such as lift-off 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. LOA environments are used directly in the development of vehicle vibro-acoustic environments and IOP is used in the loads assessment. The Scale Model Acoustic Test (SMAT) program was implemented to verify the Space Launch Systems LOA and IOP environments for the vehicle and ground systems including the Mobile Launcher (ML) and tower. The SMAT is currently in the design and fabrication phase. The SMAT program is described in this presentation.

The Marshall Space Flight Center has performed a series of test firings to simulate and understand the acoustic environments generated for the Ares I liftoff profiles. Part of the instrumentation package had special sensor groups to assess the acoustic field spatial correlation features for the various test configurations. The spatial correlation characteristics were evaluated for all of the test firings, inclusive of understanding the diffuse to propagating wave amplitude ratios, the acoustic wave decays, and the incident angle of propagating waves across the sensor groups. These parameters were evaluated across the measured frequency spectra and the associated uncertainties for each parameter were estimated.

The Ares I Scale Model Acoustic Test (ASMAT) program test matrix was designed to determine the acoustic reduction for the LOA environment with an above deck water sound suppression system. The scale model test can be used to quantify the effectiveness of the water suppression system as well as to optimize the systems necessary for LOA noise reduction. Several water flow rates were tested to determine which rate provides the greatest acoustic reductions. Preliminary results are presented.