ZTE, TMN and Microsoft have jointly launched two new 3.5G smart phones in Portugal. The SilverBelt and BlueBelt II handsets feature the WindowsR phone operating system which brings together the mobile phone,
The NASA Artemis program will take incremental steps towards establishing a sustainable and long-term human presence in the vicinity of the Moon.Artemis Ⅲ and beyond(Artemis 3+)will leverage a mission architecture th...The NASA Artemis program will take incremental steps towards establishing a sustainable and long-term human presence in the vicinity of the Moon.Artemis Ⅲ and beyond(Artemis 3+)will leverage a mission architecture that supports science in lunar orbit and on the surface of the Moon.These later Artemis missions will exploit either the Gateway spacecraft,an orbital laboratory in a 9:2 lunar resonant Near-Rectilinear Halo Orbit(NRHO),or the Human Landing System(HLS)in a similar orbit.While the NRHO provides many benefits to operations,the multi-body gravitational regime produces complex dynamics that can make orbital transfers from Earth difficult to optimize.This study provides a comprehensive examination of NRHO rendezvous transfers subjected to operational constraints presented by an Artemis 3+architecture.An ephemeris model is utilized for the outbound transfer to rendezvous with a 9:2 NRHO bounded by parameters,such as Earth parking orbit,ΔV requirements,and transfer time constraints expected from an Artemis 3+mission.The model was used to computeΔV optimal transfers to a rendezvous target at different epochs corresponding to different positions along the NRHO.Next,contour plots were generated for transferΔVs across a range of rendezvous epochs and cislunar transfer durations,similar to a porkchop plot.These contour plots allow mission designers to view the entire solution space over a selected window of dates instead of just point solutions for a given epoch.This is particularly useful for a problem that has multiple local minima.While there is already a theoretical understanding of optimal transfers to an NRHO,this work explores transfer and rendezvous optimization in the context of Artemis 3+operational constraints.Contour plots of the transfer solution space generated in this study are shown to be a valuable tool for constructing continuous and optimal launch windows.展开更多
文摘ZTE, TMN and Microsoft have jointly launched two new 3.5G smart phones in Portugal. The SilverBelt and BlueBelt II handsets feature the WindowsR phone operating system which brings together the mobile phone,
文摘The NASA Artemis program will take incremental steps towards establishing a sustainable and long-term human presence in the vicinity of the Moon.Artemis Ⅲ and beyond(Artemis 3+)will leverage a mission architecture that supports science in lunar orbit and on the surface of the Moon.These later Artemis missions will exploit either the Gateway spacecraft,an orbital laboratory in a 9:2 lunar resonant Near-Rectilinear Halo Orbit(NRHO),or the Human Landing System(HLS)in a similar orbit.While the NRHO provides many benefits to operations,the multi-body gravitational regime produces complex dynamics that can make orbital transfers from Earth difficult to optimize.This study provides a comprehensive examination of NRHO rendezvous transfers subjected to operational constraints presented by an Artemis 3+architecture.An ephemeris model is utilized for the outbound transfer to rendezvous with a 9:2 NRHO bounded by parameters,such as Earth parking orbit,ΔV requirements,and transfer time constraints expected from an Artemis 3+mission.The model was used to computeΔV optimal transfers to a rendezvous target at different epochs corresponding to different positions along the NRHO.Next,contour plots were generated for transferΔVs across a range of rendezvous epochs and cislunar transfer durations,similar to a porkchop plot.These contour plots allow mission designers to view the entire solution space over a selected window of dates instead of just point solutions for a given epoch.This is particularly useful for a problem that has multiple local minima.While there is already a theoretical understanding of optimal transfers to an NRHO,this work explores transfer and rendezvous optimization in the context of Artemis 3+operational constraints.Contour plots of the transfer solution space generated in this study are shown to be a valuable tool for constructing continuous and optimal launch windows.
