Advanced Interface Concepts for Rollable Composite Space Booms under Test in Artificial Weightlessness

In July 2021, DLR conducted a test campaign in artificial weightlessness. During a dedicated flight day, the entire 20 m x 5 m test area of the special Airbus A310 was available for 5 experiments in the field of deployable high strain composite space structures. The results presented here originate from experiment No4 in which two different deployment mechanisms for DLR's deployable CFRP masts were tested. Both types of mechanisms use new interface concepts to attach the booms to the satellite structure with high stiffness during and after deployment. Both concepts were extensively evaluated in artificial weightlessness with respect to their safe deployment and stowage as well as their resulting interface stiffness. For this purpose, the test setup in the aircraft, the test plan and the test procedure are described. Finally, the results are discussed and recommendations are given for the further development of the boom and mechanisms as well as the testing of such structures in artificial weightlessness

0G TESTING OF ALTERNATIVE BOOM ROOT INTERFACE CONCEPTS FOR ROLLABLE COMPOSITE BOOMS

In July 2021, DLR conducted a test campaign in artificial weightlessness to verify some of its concepts. During this dedicated flight day, the entire 20 m x 5 m test area of the special Airbus A310 was available for 5 experiments in the field of deployable high strain composite space structures. The results presented here originate from experiment No. 4 in which two different deployment mechanisms for DLR's deployable CFRP masts were tested. Both types of mechanisms use new interface concepts to attach the booms to the satellite structure with high stiffness during and after deployment. Both concepts were extensively evaluated in artificial weightlessness with respect to their safe deployment and stowage as well as their resulting interface stiffness. The test setup in the aircraft, the test plan and the test procedure are described hereunder. The results are discussed and recommendations are given for the further development of the boom and mechanisms as well as the testing of such structures in artificial weightlessness

Risks to Young Volunteers in International Social Projects

Background: The number of young volunteers in international social projects has increased significantly with governmental and non-governmental project support. This paper investigates the hypothesis that the preventative medical advice currently given prior to departure is inadequate because the risk profile of young persons (<30 years) differs from that of the general population. Methods: A retrospective cross-sectional study was performed with participants of international social projects. A specific questionnaire was developed; inclusion criteria were age between 18 and 30 years at departure and a duration with the project of at least 6 months. Results: One hundred and fifty-three data sets could be evaluated. Fifty-three percent were females; the destinations were as follows: 65.4% to Asia, 14.4% to Africa, and 10.5% to Latin America. The mean age was 20 years. Ninety percent of the participants received some kind of advice in travel medicine prior to departure. The vaccination rate was quite good, but pertussis (13.7%), yellow fever (80%), typhoid fever (54%), and rabies (49.7%) should be improved when travelling to high-risk regions. Food is a very important potential source of problems as 66% receive catering by the project, 56.2% from street stalls, and 44% were regularly invited to dine with locals. In Africa, only two-thirds of the participants of projects had regular access to safe water and the sanitary facilities were also poor; 51.7% of respondents reported new sexual contacts (one to more than six new partners). In most cases, condoms were used, but there were two unintended pregnancies. Conclusions: We conclude that young people need to be targeted with specialized advice for health and safety while abroad. This should highlight age-specific risks compared to advice for a more general population. Vaccination status should be improved for some regions and disease

Parabelflug mit aufrollbaren Raumfahrtstrukturen

Beim Transport von Satelliten ins All ist der begrenzte Platz an Bord der Rakete die größte Hürde. Durch dieses Nadelöhr muss alles hindurch, was in den Weltraum fliegen soll. Einige Komponenten, wie Solargeneratoren oder Antennen, müssen im All jedoch große Flächen aufspannen, um ihre Funktion zu erfüllen. Daher sind faltbare und aufrollbare Strukturen ein sehr wichtiger Entwicklungszweig in der Raumfahrt. Sollen diese Strukturen besonders leicht und kompakt sein, ergeben sich zwangsläufig Konzepte, die nur in der Schwerelosigkeit des Alls funktionieren. Entfalten sich diese Strukturen auf der Erde, brechen sie unter ihrem eigenen Gewicht zusammen. Zur Überwindung des daraus resultierenden Defizits an realistischen Tests und somit zur Erbringung des Funktionsnachweises führte das DLR – teils in Kooperation mit der NASA – im Juli 2021 fünf erfolgreiche Versuche zur Entfaltung großer Strukturen an Bord eines Spezialflugzeugs unter künstlicher Schwerelosigkeit durch

Performance analysis and mission applications of a new solar sail concept based on crossed booms with tip-deployed membranes

For precursor solar sail activities a strategy for a controlled deployment of large membranes was developed based on a combination of zig-zag folding and coiling of triangular sail segments spanned between crossed booms. This strategy required four autonomous deployment units that were jettisoned after the deployment is completed. In order to reduce the complexity of the system an adaptation of that deployment strategy is investigated. A baseline design for the deployment mechanisms is established that allows the deployment actuation from a central bus system in order to reduce the complexity of the system. The mass of such a sail craft will be slightly increased but its performance is still be reasonable for first solar sail missions. The presented design will be demonstrated on breadboard level showing the feasibility of the deployment strategy. The characteristic acceleration will be evaluated and compared to the requirements of certain proposed solar sail missions

SN2014J gamma rays from the 56^56Ni decay chain

R. Diehl, et al., “SN2014J gamma rays from the 56Ni decay chain”, Astronomy & Astrophysics, Vol. 574, January 2015. The version of record is available online at: https://www.aanda.org/articles/aa/abs/2015/02/aa24991-14/aa24991-14.html Reproduced with Permission from Astronomy and Astrophysics, © ESO 2015.Context. The detection and measurement of gamma-ray lines from the decay chain of 56Ni provides unique information about the explosion in supernovae. SN2014J at 3.3 Mpc is a sufficiently-nearby supernova of type Ia so that such measurements have been feasible with the gamma-ray spectrometer SPI on ESA’s INTEGRAL gamma-ray observatory. Aims. The 56Ni freshly produced in the supernova is understood to power the optical light curve, because it emits gamma rays upon its radioactive decay first to 56Co and then to 56Fe. Gamma-ray lines from 56Co decay are expected to become directly visible through the white dwarf material several weeks after the explosion, as they progressively penetrate the overlying material of the supernova envelope, which is diluted as it expands. The lines are expected to be Doppler-shifted or broadened from the kinematics of the 56Ni ejecta. We aim to exploit high-resolution gamma-ray spectroscopy with the SPI spectrometer on INTEGRAL toward constraining the 56Ni distribution and kinematics in this supernova. Methods. We use the observations with the SPI spectrometer on INTEGRAL, together with an improved instrumental background method. Results. We detect the two main lines from 56Co decay at 847 and 1238 keV, which are significantly Doppler-broadened, and at intensities (3.65 ± 1.21) × 10-4 and (2.27 ± 0.69) × 10-4 ph cm-2 s-1, respectively, at their brightness maximum. We measure their rise toward a maximum after about 60–100 days and a decline thereafter. The intensity ratio of the two lines is found to be consistent with expectations from 56Co decay (0.62 ± 0.28 at brightness maximum, the expected ratio is 0.68). We find that the broad lines seen in the late, gamma-ray transparent phase are not representative of the early gamma-ray emission, and notice instead that the emission spectrum is complex and irregular until the supernova is fully transparent to gamma rays, with progressive uncovering of the bulk of 56Ni. We infer that the explosion morphology is not spherically symmetric, both in the distribution of 56Ni and in the unburnt material which occults the 56Co emission. After we compare light curves from different plausible models, the resulting 56Ni mass is determined to be 0.49 ± 0.09 M⊙.Peer reviewe

A New Monte Carlo Method for Time-Dependent Neutrino Radiation Transport

Monte Carlo approaches to radiation transport have several attractive properties compared to deterministic methods. These include simplicity of implementation, high accuracy, and good parallel scaling. Moreover, Monte Carlo methods can handle complicated geometries and are relatively easy to extend to multiple spatial dimensions, which makes them particularly interesting in modeling complex multi-dimensional astrophysical phenomena such as core-collapse supernovae. The aim of this paper is to explore Monte Carlo methods for modeling neutrino transport in core-collapse supernovae. We generalize the implicit Monte Carlo photon transport scheme of Fleck & Cummings and gray discrete-diffusion scheme of Densmore et al. to energy-, time-, and velocity-dependent neutrino transport. Using our 1D spherically-symmetric implementation, we show that, similar to the photon transport case, the implicit scheme enables significantly larger timesteps compared with explicit time discretization, without sacrificing accuracy, while the discrete-diffusion method leads to significant speed-ups at high optical depth. Our results suggest that a combination of spectral, velocity-dependent, implicit Monte Carlo and discrete-diffusion Monte Carlo methods represents an attractive approach for use in neutrino radiation-hydrodynamics simulations of core-collapse supernovae. Our velocity-dependent scheme can easily be adapted to photon transport

The imprint of a symbiotic binary progenitor on the properties of Kepler's supernova remnant

We present a model for the Type Ia supernova remnant (SNR) of SN 1604, also known as Kepler's SNR. We find that its main features can be explained by a progenitor model of a symbiotic binary consisting of a white dwarf and an AGB donor star with an initial mass of 4-5 M_sun. The slow, nitrogen rich wind emanating from the donor star has partially been accreted by the white dwarf, but has also created a circumstellar bubble. Based on observational evidence, we assume that the system moves with a velocity of 250 km/s. Due to the systemic motion the interaction between the wind and the interstellar medium has resulted in the formation of a bow shock, which can explain the presence of a one-sided, nitrogen rich shell. We present two-dimensional hydrodynamical simulations of both the shell formation and the SNR evolution. The SNR simulations show good agreement with the observed kinematic and morphological properties of Kepler's SNR. Specifically, the model reproduces the observed expansion parameters (m=V/(R/t)) of m=0.35 in the north and m=0.6 in the south of Kepler's SNR. We discuss the variations among our hydrodynamical simulations in light of the observations, and show that part of the blast wave may have traversed through the one-sided shell completely. The simulations suggest a distance to Kepler's SNR of 6 kpc, or otherwise require that SN 1604 was a sub-energetic Type Ia explosion. Finally, we discuss the possible implications of our model for Type Ia supernovae and their remnants in general.Comment: 13 pages, 9 figures. Submitted to A&

Hepatic artery reconstruction using an operating microscope in pediatric liver transplantation—Is it worth the effort?

Introduction: In pediatric liver transplantation (pLT), hepatic artery thrombosis (HAT) is associated with inferior transplant outcome. Hepatic artery reconstruction (HAR) using an operating microscope (OM) is considered to reduce the incidence of HAT. Methods: HAR using an OM was compared to a historic cohort using surgical loupes (SL) in pLT performed between 2009 and 2020. Primary endpoint was the occurrence of HAT. Secondary endpoints were 1-year patient and graft survival determined by Kaplan-Meier analysis and complications. Multivariate analysis was used to identify independent risk factors for HAT and adverse events. Results: A total of 79 pLTs were performed [30 (38.0%) living donations; 49 (62.0%) postmortem donations] divided into 23 (29.1%) segment 2/3, 32 (40.5%) left lobe, 4 (5.1%) extended right lobe, and 20 (25.3%) full-size grafts. One-year patient and graft survival were both 95.2% in the OM group versus 86.2% and 77.8% in the SL group (p = .276 and p = .077). HAT rate was 0% in the OM group versus 24.1% in the SL group (p = .013). One-year patient and graft survival were 64.3% and 35.7% in patient with HAT, compared to 93.9% and 92.8% in patients with no HAT (both p < .001). Multivariate analysis revealed HAR with SL (p = .022) and deceased donor liver transplantation (DDLT) (p = .014) as independent risk factors for HAT. The occurrence of HAT was independently associated with the need for retransplantation (p < .001) and biliary leakage (p = .045). Conclusion: In pLT, the use of an OM is significantly associated to reduce HAT rate, biliary complications, and graft loss and outweighs the disadvantages of delayed arterial perfusion and prolonged warm ischemia time (WIT)