Highly reusable space transportation: Approaches for reducing ETO launch costs to 100−100 - 200 per pound of payload

The Commercial Space Transportation Study (CSTS) suggests that considerable market expansion in earth-to-orbit transportation would take place if current launch prices could be reduced to around $400 per pound of payload. If these low prices can be achieved, annual payload delivered to low earth orbit (LEO) is predicted to reach 6.7 million pounds. The primary market growth will occur in communications, government missions, and civil transportation. By establishing a cost target of$100-$200 per pound of payload for a new launch system, the Highly Reusable Space Transportation (HRST) program has clearly set its sights on removing the current restriction on market growth imposed by today's high launch costs. In particular, achieving the goal of$100-$200 per pound of payload will require significant coordinated efforts in (1) marketing strategy development, (2) business planning, (3) system operational strategy, (4) vehicle technical design, and (5) vehicle maintenance strategy

Inference of selection gradients using performance measures as fitness proxies

O.D.F. is supported by the Natural Sciences and Engineering Research Council of Canada and the Madame Vigdís Finnbogadóttir Scholarship. M.B.M. is supported by a University Research Fellowship from the Royal Society (London).1.  Selection coefficients, i.e., selection differentials and gradients, are useful for quantifying selection and for making comparisons across traits and organisms, because they appear in known equations for relating selection and genetic variation to one another and to evolutionary change. However, selection coefficients can only be estimated in organisms where traits and fitness (components) can be measured. This is probably a major contributor to taxonomic biases of selection studies. Aspects of organismal performance, i.e., quantities that are likely to be positively related to fitness components, such as body size, are sometimes used as proxies for fitness, i.e., used in place of fitness components in regression-based selection analysis. To date, little theory exists to inform empirical studies about whether such procedures may yield selection coefficients with known relationships to genetic variation and evolution. 2.  We show that the conditions under which performance measures can be used as proxies for fitness are very limited. Such analyses require that the regression of fitness on the proxy is linear and goes through the origin. We illustrate how fitness proxies may be used in conjunction with information about the performance-fitness relationship, and clarify how this is different from substituting fitness proxies for fitness components in selection analyses. 3.  We apply proxy-based and fitness component-based selection analysis to a system where traits, a performance measure (size; similar to proxies that are commonly used in place of fitness), and a more proximate fitness measure, are all available on the same set of individuals. We find that proxy-based selection gradients are poorly reflective of selection gradients estimated using fitness components, even when proxy-fitness relationships are quite strong and reasonably linear. 4.  We discuss the implications for proxy-based selection analysis. We emphasise that measures of organismal performance, such as size, may in many cases provide useful information that can contribute to quantitative inferences about natural selection, and their use could allow quantitative inference about selection to be conducted in a wider range of taxa. However, such inferences require quantitative analysis of both trait-performance and performance-fitness relationships, rather than substitution of performance for measures of fitness or fitness components.PostprintPeer reviewe

Highly Reusable Space Transportation System Concept Evaluation (The Argus Launch Vehicle)

This paper summarizes the results of a conceptual design study that was performed in support of NASA's recent Highly Reusable Space Transportation study. The Argus concept uses a Maglifter magnetic-levitation sled launch assist system to accelerate it to a takeoff ground speed of 800 fps on its way to delivering a payload of 20,000 lb. to low earth orbit. Main propulsion is provided by two supercharged ejector rocket engines. The vehicle is autonomous and is fully reusable. A conceptual design exercise determined the vehicle gross weight to be approximately 597,250 lb. and the dry weight to be 75,500 lb. Aggressive weight and operations cost assumptions were used throughout the design process consistent with a second-generation reusable system that might be deployed in 10-15 years. Drawings, geometry, and weight of the concept are included. Preliminary development, production, and operations costs along with a business scenario assuming a price-elastic payload market are also included. A fleet of three Argus launch vehicles flying a total of 149 flights per year is shown to have a financial internal rate of return of 28%. At $169/lb., the recurring cost of Argus is shown to meet the study goal of$100/lb.-$200/lb., but optimum market price results in only a factor of two to five reduction compared to today's launch systems

Use of Flexible Body Coupled Loads in Assessment of Day of Launch Flight Loads

A Day of Launch flight loads assessment technique that determines running loads calculated from flexible body coupled loads was developed for the Ares I-X Flight Test Vehicle. The technique was developed to quantify DOL flight loads in terms of structural load components rather than the typically used q-alpha metric to provide more insight into the DOL loads. In this technique, running loads in the primary structure are determined from the combination of quasi-static aerodynamic loads and dynamic loads. The aerodynamic loads are calculated as a function of time using trajectory parameters passed from the DOL trajectory simulation and are combined with precalculated dynamic loads using a load combination equation. The potential change in aerodynamic load due to wind variability during the countdown is included in the load combination. In the event of a load limit exceedance, the technique allows the identification of what load component is exceeded, a quantification of how much the load limit is exceeded, and where on the vehicle the exceedance occurs. This technique was used to clear the Ares I-X FTV for launch on October 28, 2009. This paper describes the use of coupled loads in the Ares I-X flight loads assessment and summarizes the Ares I-X load assessment results

In children 18 years and under, what promotes recurrent shoulder instability after traumatic anterior shoulder dislocation? A systematic review and meta-analysis of risk factors

Background Skeletal maturity and age-related changes in the composition of the glenoid labrum and joint capsule may influence rates of recurrent instability in children. We systematically review risk factors which predispose children to recurrent shoulder instability. Methods The systematic review-concerned studies published before May 2015. Statistical analysis was undertaken to compare rates of recurrence for each extracted risk factor. Pooled ORs were analysed using random effects meta-analysis. Results 6 retrospective cohort studies met the inclusion criteria. 8 risk factors were identified across the studies including age, sex, shoulder dominance and injury side, mechanism of injury, state of physis closure, and Hill-Sachs and Bankart lesions. The rate of recurrent instability was 73%. Children aged 14–18 years were 24 times more likely to experience recurrent instability than children aged 13 years and less (93% vs 40%; OR=24.14, 95% CI (3.71 to 156.99), Z=3.33, p=0.001, I2=6.83%). There was a non-significant trend indicating males were 3.4 times more likely to experience recurrent instability (OR=3.44, 95% CI (0.98 to 12.06), Z=1.93, p=0.053, I2=0%). Analysis of one study found that children with a closed physis are 14 times more likely to experience recurrent instability compared with those with an open physis (OR=14.0, 95% CI (1.46 to 134.25), Z=2.29, p=0.02, I2=0%) . Conclusions Male children aged 14 years and over had the greatest risk of recurrent shoulder instability following a first-time traumatic anterior shoulder dislocation. This meta-analysis summarises a mix of 6 acceptable and poor quality level III retrospective cohort studies. Further examination of this population with blinded prospective cohort studies will assist clinicians in the appropriate management of first-time traumatic anterior shoulder dislocation

Ares I-X Range Safety Flight Envelope Analysis

Ares I-X was the first test flight of NASA's Constellation Program's Ares I Crew Launch Vehicle designed to provide manned access to low Earth orbit. As a one-time test flight, the Air Force's 45th Space Wing required a series of Range Safety analysis data products to be developed for the specified launch date and mission trajectory prior to granting flight approval on the Eastern Range. The range safety data package is required to ensure that the public, launch area, and launch complex personnel and resources are provided with an acceptable level of safety and that all aspects of prelaunch and launch operations adhere to applicable public laws. The analysis data products, defined in the Air Force Space Command Manual 91-710, Volume 2, consisted of a nominal trajectory, three sigma trajectory envelopes, stage impact footprints, acoustic intensity contours, trajectory turn angles resulting from potential vehicle malfunctions (including flight software failures), characterization of potential debris, and debris impact footprints. These data products were developed under the auspices of the Constellation's Program Launch Constellation Range Safety Panel and its Range Safety Trajectory Working Group with the intent of beginning the framework for the operational vehicle data products and providing programmatic review and oversight. A multi-center NASA team in conjunction with the 45th Space Wing, collaborated within the Trajectory Working Group forum to define the data product development processes, performed the analyses necessary to generate the data products, and performed independent verification and validation of the data products. This paper outlines the Range Safety data requirements and provides an overview of the processes established to develop both the data products and the individual analyses used to develop the data products, and it summarizes the results of the analyses required for the Ares I-X launch

Exploring Communal and Gendered Influences on Sexual Health Practices

In the U.S., 10% of female college students who have an unplanned pregnancy, drop out (UPFO, 2016). Additionally, young adults (15-24) account for half of the new STI’s (CDC, 2017). Previous research has established communal (other-oriented) motivation is positively associated with factors that predict safe sex practices (e.g., condom use intentions) (Phillips et al., 2019). Conversely, gender norms (societal expectations affiliated with gender) are negatively associated with factors that predict safe sex practices (e.g., partner communication and self-efficacy). For instance, although, women who report higher self-efficacy are more likely to engage in partner communication, women who rely on traditional gender norms report diminished self-efficacy and in turn, partner communication (Bertens et al., 2008; Impett et al., 2006). While gender norms seemingly diminish self-efficacy among women, women also feel that pregnancy prevention is primarily their responsibility, as compared to men. (Fantasia et al., 2014; Huber & Eresek, 2011). We hypothesized that communal motivation and gender norms would interact to predict perceptions of responsibility and self-efficacy, which in turn would predict partner communication, and ultimately safe sex practices. We also expected that these interactions would differ based on participant gender. We surveyed approximately 260 college-aged participants from a North Florida university. We anticipate that communal motivation will be positively associated with safe sex practices, while we anticipate that gender norms will be more negatively associated with safe sex practices. Our findings will illuminate critical factors associated with sexual health practices that will supplement how to approach sexual health education in the future