Project Minerva: A low cost manned Mars mission based on indigenous propellant production

Project Minerva is a low-cost manned Mars mission designed to deliver a crew of four to the Martian surface using only two sets of two launches from the Kennedy Space Center. Key concepts which make this mission realizable are the use of near-term technologies and in-situ propellant production, following the scenario originally proposed by R. Zubrin. The first set of launches delivers two unmanned payloads into low Earth orbit (LEO): the first payload consists of an Earth Return Vehicle (ERV), a propellant production plant, and a set of robotic vehicles; the second payload consists of the trans-Mars injection (TMI) upper stage. In LEO, the two payloads are docked and the configuration is injected into a Mars transfer orbit. The landing on Mars is performed with the aid of multiple aerobraking maneuvers. On the Martian surface, the propellant production plant uses a Sabatier/electrolysis type process to combine nine tons of hydrogen with carbon dioxide from the Martian atmosphere to produce over a hundred tons of liquid oxygen and liquid methane, which are later used as the propellants for the rover expeditions and the manned return journey of the ERV. The systems necessary for the flights to and from Mars, as well as those needed for the stay on Mars, are discussed. These systems include the transfer vehicle design, life support, guidance and communications, rovers and telepresence, power generation, and propellant manufacturing. Also included are the orbital mechanics, the scientific goals, and the estimated mission costs

Reliability of the mouse model of choroidal neovascularization induced by laser photocoagulation

Abstract Purpose: We attempted to reproduce published studies that evaluated whether the following factors influence the choroidal neovascularization (CNV) induced by laser photocoagulation in murine retinas: small interfering RNA (siRNA), cobra venom factor, the complement factors C3 and C5, and complement receptor C5aR. In addition, we explored whether laser-induced CNV in mice is influenced by the vendor of origin of the animals or by the scientist administering the laser. Methods: Experimental procedures for standardizing the measurement of laser-induced CNV were developed and validated with oral doses of pazopanib, a low molecular weight (LMW) vascular endothelial growth factor (VEGF) receptor kinase inhibitor. Reagents or genotypes reported by others to influence CNV in this model were assessed utilizing our standard procedures, with dose regimens closely mimicking those used in respective publications. Retrospective analyses of control or placebo mice in many experiments were done to evaluate whether the CNV area induced by laser photocoagulation varied according to vendor, laser operator, or year that the experiment was conducted. Results: We developed methods that reproducibly showed that oral doses of pazopanib dose-dependently reduced CNV. The administration of the following agents did not have a substantial impact on the choroidal neovascularization induced by laser burns in mice: small interfering RNA (siRNA), a LMW inhibitor of the C5a receptor (PMX53), or cobra venom factor. JAX mice lacking either C3 or C5 had increased neovascularization compared to non-littermate JAX wild-type controls. Taconic mice lacking C3 had reduced CNV compared to non-littermate Taconic wild type control mice. A retrospective analysis of vehicle-treated wild-type C57BL/6 mice used as controls across 132 experiments conducted from 2007 - 2010 revealed that mice purchased from the Jackson Labs or from Charles River produced less neovascularization than mice from Taconic. There was no significant difference in choroidal neovascularization between 4 different scientists administering laser burns to wild-type mice from one vendor. A further retrospective analysis of vehicle-treated mice from Taconic revealed similar average CNV areas in 2007 – 2010 but comparatively smaller average CNV areas in 2011 and 2012. Conclusions: We were not able to reproduce results from four publications using the laser-induced CNV model in mice. This non-reproducibility could be related to unidentified variations in the responsiveness of mice derived from different vendors or differences in reagents, laser applications, blood vessel measurements, or techniques of compound administration. Alternatively, the discrepancy between our results compared to other published studies could be due to published studies having type 1 errors because of insufficient power, no pre-determined inclusion and exclusion criteria, no or insufficient masking, lack of a positive controls, or lack of confirmation studies. We present our recommended methods for conducting experiments with the mouse laser-induced CNV model to enhance reproducibility and minimize investigator bias

Genomic reconstruction of the SARS-CoV-2 epidemic in England

AbstractThe evolution of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus leads to new variants that warrant timely epidemiological characterization. Here we use the dense genomic surveillance data generated by the COVID-19 Genomics UK Consortium to reconstruct the dynamics of 71 different lineages in each of 315 English local authorities between September 2020 and June 2021. This analysis reveals a series of subepidemics that peaked in early autumn 2020, followed by a jump in transmissibility of the B.1.1.7/Alpha lineage. The Alpha variant grew when other lineages declined during the second national lockdown and regionally tiered restrictions between November and December 2020. A third more stringent national lockdown suppressed the Alpha variant and eliminated nearly all other lineages in early 2021. Yet a series of variants (most of which contained the spike E484K mutation) defied these trends and persisted at moderately increasing proportions. However, by accounting for sustained introductions, we found that the transmissibility of these variants is unlikely to have exceeded the transmissibility of the Alpha variant. Finally, B.1.617.2/Delta was repeatedly introduced in England and grew rapidly in early summer 2021, constituting approximately 98% of sampled SARS-CoV-2 genomes on 26 June 2021.</jats:p