Opening the Solar System: An Advanced Nuclear Spacecraft for Human Exploration

Human exploration of the solar system is limited by our technology, not our imagination. We dream of a time when we can freely travel among the planets and truly become a spacefaring people. However, the current state of our technology limits our options for architecting missions to other planets. Instead of sailing the seas of space in the way that we cruise the seas of Earth, our limited propulsion technology requires us to depart Earth on a giant cluster of gas tanks and return in a lifeboat. This inefficient approach to exploration is evident in many of today's leading mission plans for human flights to Mars, asteroids, and other destinations. The cost and complexity of this approach to mission architecting makes it extremely difficult to realize our dreams of exploration beyond Low Earth Orbit (LEO). This does not need to be the case. Researchers at NASA's Marshall Space Flight Center (MSFC) have been investigating the feasibility of a new take on nuclear propulsion with the performance to enable a paradigm shift in human space exploration. During the fall of 2013, engineers at MSFC's Advanced Concepts Office developed a spacecraft concept (pictured below) around this new propulsion technology and redefined the human Mars mission to show its full potential. This spacecraft, which can be launched with a fleet of soon-to-be available SLS launch vehicles, is fueled primarily with hydrogen, and is fully reusable with no staging required. The reusable nature of this design enables a host of alternative mission architectures that more closely resemble an ocean voyage than our current piecemeal approach to exploration

Assessing the Relative Risk of Aerocapture Using Probabalistic Risk Assessment

A recent study performed for the Aerocapture Technology Area in the In-Space Propulsion Technology Projects Office at the Marshall Space Flight Center investigated the relative risk of various capture techniques for Mars missions. Aerocapture has been proposed as a possible capture technique for future Mars missions but has been perceived by many in the community as a higher risk option as compared to aerobraking and propulsive capture. By performing a probabilistic risk assessment on aerocapture, aerobraking and propulsive capture, a comparison was made to uncover the projected relative risks of these three maneuvers. For mission planners, this knowledge will allow them to decide if the mass savings provided by aerocapture warrant any incremental risk exposure. The study focuses on a Mars Sample Return mission currently under investigation at the Jet Propulsion Laboratory (JPL). In each case (propulsive, aerobraking and aerocapture), the Earth return vehicle is inserted into Martian orbit by one of the three techniques being investigated. A baseline spacecraft was established through initial sizing exercises performed by JPL's Team X. While Team X design results provided the baseline and common thread between the spacecraft, in each case the Team X results were supplemented by historical data as needed. Propulsion, thermal protection, guidance, navigation and control, software, solar arrays, navigation and targeting and atmospheric prediction were investigated. A qualitative assessment of human reliability was also included. Results show that different risk drivers contribute significantly to each capture technique. For aerocapture, the significant drivers include propulsion system failures and atmospheric prediction errors. Software and guidance hardware contribute the most to aerobraking risk. Propulsive capture risk is mainly driven by anomalous solar array degradation and propulsion system failures. While each subsystem contributes differently to the risk of each technique, results show that there exists little relative difference in the reliability of these capture techniques although uncertainty for the aerocapture estimates remains high given the lack of in-space demonstration

Substructure in clusters containing wide-angle tailed radio galaxies. I. New redshifts

We present new redshifts and positions for 635 galaxies in nine rich clusters containing Wide-Angle Tailed (WAT) radio galaxies. Combined with existing data, we now have a sample of 18 WAT-containing clusters with more than 10 redshifts. This sample contains a substantial portion of the WAT clusters in the VLA 20 cm survey of Abell clusters, including 75% of WAT clusters in the complete survey (z0.09. It is a representative sample which should not contain biases other than selection by radio morphology. We graphically present the new data using histograms and sky maps. A semi-automated procedure is used to search for emission lines in the spectra in order to add and verify galaxy redshifts. We find that the average apparent fraction of emission line galaxies is about 9% in both the clusters and the field. We investigate the magnitude completeness of our redshift surveys with CCD data for a test case, Abell 690. This case indicates that our galaxy target lists are deeper than the detection limit of a typical MX exposure, and they are 82% complete down to R=19.0. The importance of the uniformity of the placement of fibers on targets is posited, and we evaluate this in our datasets. We find some cases of non-uniformities which may influence dynamical analyses. A second paper will use this database to look for correlations between the WAT radio morphology and the cluster's dynamical state.Comment: 15 pages, 5 figures, 7 tables. To appear in the Astronomical Journa

Role of dielectric constant in electrohydrodynamics of conducting fluids

Electrohydrodynamic (EHD) flows are driven by the interaction of an electric field with variations in electric conductivity or dielectric constant. In reported EHD experiments on the deformation of drops of immiscible dielectric fluids, the role of conductivity has tended to overshadow the role of dielectric constant. Often, large conductivity contrasts were convenient because the conductivities of the dielectric fluid were relatively uncertain. As a result, the observed effects were always qualitatively the same as if there had been no contrast in dielectric constant. Our early experiments studying the EHC deformations of cylindrical streams readily showed the conductivity effect but the dielectric constant effect was not discernible. We have modified our flow chamber and improved our method of observation and can now see an unequivocal dielectric constant effect which is in agreement with the prior theory. In this paper we first give a brief description of the physics of charge buildup at the interface of an immersed spherical drop or flowing cylindrical sample stream and then show how these charge distributions lead to interface distortions and accompanying viscous flows which constitute EHD. We next review theory and experiment describing the deformation of spherical drops. We show that in the reported drop deformation experiments, the contrast in dielectric constant was never sufficient to reverse the deformation due to the conductivity contrast. We review our work describing the deformation of a cylindrical stream of one fluid flowing in a parallel flow of another, and we compare the deformation equations with those for spherical drops. Finally, we show a definite experimental dielectric constant effect for cylindrical stream of aqueous polystyrene latex suspension. The dielectric constant varies with the frequency of the imposed electric field, and the associated EHD flow change is very apparent

Role of dielectric constant in electrohydrodynamics of conducting fluids

Electrohydrodynamic sample distortion during continuous flow electrophoresis is an experiment to be conducted during the second International Microgravity Laboratory (IML-2) in July 1994. The specific objective of this experiment is the distortion caused by the difference in dielectric constant between the sample and surrounding buffer. Although the role of sample conductivity in electrohydrodynamic has been the subject of both flight and ground experiments, the separate role of dielectric constant, independent of sample conductivity, has not been measured. This paper describes some of the laboratory research and model development that will support the flight experiment on IML-2

Studies of Fission Fragment Rocket Engine Propelled Spacecraft

The NASA Office of Chief Technologist has funded from FY11 through FY14 successive studies of the physics, design, and spacecraft integration of a Fission Fragment Rocket Engine (FFRE) that directly converts the momentum of fission fragments continuously into spacecraft momentum at a theoretical specific impulse above one million seconds. While others have promised future propulsion advances if only you have the patience, the FFRE requires no waiting, no advances in physics and no advances in manufacturing processes. Such an engine unequivocally can create a new era of space exploration that can change spacecraft operation. The NIAC (NASA Institute for Advanced Concepts) Program Phase 1 study of FY11 first investigated how the revolutionary FFRE technology could be integrated into an advanced spacecraft. The FFRE combines existent technologies of low density fissioning dust trapped electrostatically and high field strength superconducting magnets for beam management. By organizing the nuclear core material to permit sufficient mean free path for escape of the fission fragments and by collimating the beam, this study showed the FFRE could convert nuclear power to thrust directly and efficiently at a delivered specific impulse of 527,000 seconds. The FY13 study showed that, without increasing the reactor power, adding a neutral gas to the fission fragment beam significantly increased the FFRE thrust through in a manner analogous to a jet engine afterburner. This frictional interaction of gas and beam resulted in an engine that continuously produced 1000 pound force of thrust at a delivered impulse of 32,000 seconds, thereby reducing the currently studied DRM 5 round trip mission to Mars from 3 years to 260 days. By decreasing the gas addition, this same engine can be tailored for much lower thrust at much higher impulse to match missions to more distant destinations. These studies created host spacecraft concepts configured for manned round trip journeys. While the vehicles are very large, they are primarily made up of a habitat payload on one end, the engine on the opposite end and a connecting spine containing radiator acreage needed to reject the heat of this powerful, but inefficient engine. These studies concluded that the engine and spacecraft are within today's technology, could be built, tested, launched on several SLS launchers, integrated, checked out, maintained at an in-space LEO base, and operated for decades just as Caribbean cruise ships operate today. The nuclear issues were found to be far less daunting that [than for] current nuclear engines. The FFRE produces very small amounts of radioactive efflux compared to their impulse, easily contained in an evacuated "bore-hole" test site. The engine poses no launch risk since it is simply a structure containing no fissionable material. The nuclear fuel is carried to orbit in containers highly crash-proofed for launch accidents from which it, in a liquid medium, is injected into the FFRE. The radioactive exhaust, with a velocity above 300 kilometers per second rapidly leaves the solar system

RUSHing to the Diagnosis: Aortic Abdominal Aneurysm Detected Using the Rapid Ultrasound for Shock and Hypotension (RUSH) Protocol in the Wards

The rapid ultrasound for shock and hypotension (RUSH) protocol is a useful tool used in the emergency department (ED) when addressing the severity and etiology of shock. It was designed to be performed in under two minutes with evaluation of the pump (heart), tank (inferior vena cava, thoracic and abdominal compartments) and the pipes (large arteries and veins). However, its application or one similar should extend beyond the ED and into the hospital floor. Here we present an 80-year-old gentleman with a history of atrial fibrillation (A-Fib) on anticoagulation who arrived at the ED due to an episode of pre-syncope just prior to arrival. Initial EKG is concerning for A-Fib with rapid ventricular response (RVR) with a rate in the 130s. After fluid resuscitation patient improved and he was admitted to the telemetry floor for further cardiac workup and cardiology consultation. While waiting for a room in the ED, patient became hypotensive, diaphoretic and pale. After complaining of lower abdominal pain, the ED physician performed a RUSH which showed an abdominal aorta of 8 cm concerning for dissection. Diagnosis was confirmed with CT angiography of the abdomen and he was taken to the OR with successful repair of the abdominal aortic aneurysm (AAA). Patient made meaningful recovery and was discharged to in-patient rehab. The patient described in this vignette was delayed in the ED due to lack of beds on the floor. This allowed for quick ultrasound work-up by the ED physician which led to immediate recognition of the AAA and immediate response by the vascular surgery team. Should this patient have been on the hospital floor, it is unclear if such prompt steps would have occurred prior to patient’s further hemodynamic demis

Estrategias cotidianas para la producción de textos narrativos

The production of narrative texts; it must be a constant practice in the students; However, they have difficulties for not knowing strategies that allow them to write easily. For this reason, the research work aimed to demonstrate the influence of the application of everyday strategies for the production of narrative texts. The method used was the deductive inductive and the synthetic analytical; which corresponded to the level of experimental research, applied type and quasi-experimental design. The population consisted of 270 students; The sample was non-probabilistic, non-standard or circumstantial sampling with 30 students from the 5th “A” (experimental group) and 5th “B” (control group), with the application of the pretest and posttest. In the first group, daily strategies were applied; and in the second, the conventional approach. Through the result of the post test, the influence of the strategy could be determined; since 80% of the students in the experimental group are in expected achievement and 20% in outstanding achievement respectively. In conclusion, everyday strategies significantly influence the production of narrative texts, generating meaningful learning for students.La producción de textos narrativos debe ser una práctica constante en los estudiantes; sin embargo, estos tienen dificultades por desconocer estrategias que les permitan redactar con facilidad. Por esta razón, el trabajo de investigación tuvo como objetivo demostrar la influencia de la aplicación de las estrategias cotidianas para la producción de textos narrativos. El método utilizado fue el inductivo deductivo y el analítico sintético; el nivel de investigación fue experimental, de tipo aplicado y diseño cuasi experimental. La población estuvo constituida por 270 estudiantes; la muestra fue de tipo no probabilístico, sin normas o circunstancial. Con 30 estudiantes del 5.° “A” (grupo experimental) y 5.° “B” (grupo control), con la aplicación de la preprueba y postprueba. En el primer grupo, se aplicó las estrategias cotidianas; y, en el segundo, el enfoque convencional. Mediante el resultado de la postprueba, se pudo determinar la influencia de la estrategia; puesto que, el 80 % de los estudiantes del grupo experimental se encuentra en logro previsto y el 20 %, en logro destacado, respectivamente. En conclusión, las estrategias cotidianas influyen significativamente en la producción de textos narrativos, generando en los estudiantes aprendizaje significativo