Constants and cosmology: The nature and origin of fundamental constants in astrophysics and particle physics

We ask about the nature and origin of the fundamental constants of astrophysics and particle physics, notably the speed of light c, the gravitational constant G, Planck's constant h, and the magnitude of the electron charge e. We consider general relativity and the theories of the electromagnetic, weak and strong interactions that make up the Standard Model; together with the Lagrangians of Einstein, Maxwell, Schrödinger, Klein-Gordon, Dirac, Proca, and Yang-Mills. Then we look in a more qualitative way at how the equations of physics are set up, their dimensional content, and the removal of constants from them by a suitable choice of units. We conclude with Hoyle and Narlikar, Jeffreys and McCrea that parameters like c, G, and h are merely manmade dimensional conversion constants. They arise because of our subjective view that mass, length, and time are different concepts. These constants can be removed in a manner analogous to the removal of the permittivity of free space ₀ from electrodynamics, and none are really fundamental. The charge e is different, being the low-energy limit of a function related to properties of the vacuum, but because of this it is not a fundamental constant either. We suggest there are no constants which truly deserve to be called fundamental, and that an aim of physics ought to be to write down laws in which no constants appear.     

Theoretical modeling for the stereo mission

We summarize the theory and modeling efforts for the STEREO mission, which will be used to interpret the data of both the remote-sensing (SECCHI, SWAVES) and in-situ instruments (IMPACT, PLASTIC). The modeling includes the coronal plasma, in both open and closed magnetic structures, and the solar wind and its expansion outwards from the Sun, which defines the heliosphere. Particular emphasis is given to modeling of dynamic phenomena associated with the initiation and propagation of coronal mass ejections (CMEs). The modeling of the CME initiation includes magnetic shearing, kink instability, filament eruption, and magnetic reconnection in the flaring lower corona. The modeling of CME propagation entails interplanetary shocks, interplanetary particle beams, solar energetic particles (SEPs), geoeffective connections, and space weather. This review describes mostly existing models of groups that have committed their work to the STEREO mission, but is by no means exhaustive or comprehensive regarding alternative theoretical approaches.     

Local Interstellar Medium Summary of Working Group VI

This report summarizes the issues discussed in Working Group VI concerning the accuracy of measurements of D/H and 3He/H in the local interstellar medium, possible systematic errors, and emerging trends in the results.     

Smart sensor Web: tactical battlefield visualization using sensor fusion

Smart sensor Web (SSW) is a recent DUSD (S&T) initiative inspired by extraordinary technological advances in sensors and microelectronics and by the emergence of the Internet as a real-time communication tool. The overall vision for SSW is an intelligent, Web-centric distribution and fusion of sensor information that provides greatly enhanced situational awareness, on demand, to warfighters at lower echelons. Emphasis is on multi-sensor fusion of large arrays of local sensors, joined with other assets, to provide real-time imagery, weather, targeting information, mission planning, and simulations for military operations on land, sea, and air. This paper gives an overview of this new initiative, highlights some of the technology challenges in sensor/information fusion, and presents a program approach for near-term demonstrations and long-term solutions, involving the DoD, National Labs, commercial industry, and academia.     

YES2 optimal trajectories in presence of eccentricity and aerodynamic drag

YES2 (launching 2007) aims to demonstrate a tether-assisted re-entry concept, whereby payload will be returned to Earth using momentum provided from a swinging tether. Deployment takes place in two phases: (1) deployment of 3.5 km of tether to the local vertical and hold, and (2) deployment to 30 km for a swinging cut. Optimal trajectories are determined for both phases after comparing the effect of different cost functions on the deployment dynamics. Closed-loop control is provided by linearizing the dynamics around the optimal trajectories and solving a receding horizon control problem for a set of linear feedback gains. The controllers are tested in a flexible tether model with large disturbances to the hardware model and environmental variables. Closed-loop simulations show that the system can be controlled quite well using only feedback of length and length rate.     

Radiation analysis for manned missions to the Jupiter system.

An analysis for manned missions targeted to the Jovian system has been performed in the framework of the NASA RASC (Revolutionary Aerospace Systems Concepts) program on Human Exploration beyond Mars. The missions were targeted to the Jupiter satellite Callisto. The mission analysis has been divided into three main phases, namely the interplanetary cruise, the Jupiter orbital insertion, and the surface landing and exploration phases. The interplanetary phase is based on departure from the Earth-Moon L1 point. Interplanetary trajectories based on the use of different propulsion systems have been considered, with resulting overall cruise phase duration varying between two and five years. The Jupiter-approach and the orbital insertion trajectories are considered in detail, with the spacecraft crossing the Jupiter radiation belts and staying around the landing target. In the surface exploration phase the stay on the Callisto surface is considered. The satellite surface composition has been modeled based on the most recent results from the GALILEO spacecraft. In the transport computations the surface backscattering has been duly taken into account. Particle transport has been performed with the HZETRN heavy ion code for hadrons and with an in-house developed transport code for electrons and bremsstrahlung photons. The obtained doses have been compared to dose exposure limits.     

Effects of orbit progression on the radiation exposures from solar proton fluxes in low Earth orbit under geomagnetic storm conditions.

The present study examines the effects of orbit progression on the exposures within a Space Station Freedom module in a 51.6-degree inclined orbit at 450 km. The storm evolution is modeled after the November 1960 event, and the solar proton flux evolution is taken from the August 1972 solar proton event. The effects of a strong magnetic shock, such as was observed during the October 1989 event, is also modeled. The statistics on hourly average storm fields for the last forty years reveal that the largest geomagnetic storms approach a Dst value of -500 nanotesla at the storm peak. Similarly, one of the largest satellite-measured proton flux (> 10 MeV) for space exposures is the event of August 1972. The effects of orbit progression (advance of the line of nodes) is examined for the above conditions to study the variation of exposures under differing times of occurrence of the solar proton peak intensity, attainment of geomagnetic storm maximum, and the location of the line of nodes of the last geomagnetically protected orbit. The impact of the inherent inhomogeneity of the space station module is examined as a limiting factor on exposure with regard to the need of additional parasitic shielding.     

Materials trade study for lunar/gateway missions.

The National Aeronautics and Space Administration (NASA) administrator has identified protection from radiation hazards as one of the two biggest problems of the agency with respect to human deep space missions. The intensity and strength of cosmic radiation in deep space makes this a 'must solve' problem for space missions. The Moon and two Earth-Moon Lagrange points near Moon are being proposed as hubs for deep space missions. The focus of this study is to identify approaches to protecting astronauts and habitats from adverse effects from space radiation both for single missions and multiple missions for career astronauts to these destinations. As the great cost of added radiation shielding is a potential limiting factor in deep space missions, reduction of mass, without compromising safety, is of paramount importance. The choice of material and selection of the crew profile play major roles in design and mission operations. Material trade studies in shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of space mission's to two Earth-Moon co-linear Lagrange points (L1) between Earth and the Moon and (L2) on back side of the moon as seen from Earth, and to the Moon have been studied. It is found that, for single missions, current state-of-the-art knowledge of material provides adequate shielding. On the other hand, the choice of shield material is absolutely critical for career astronauts and revolutionary materials need to be developed for these missions. This study also provides a guide to the effectiveness of multifunctional materials in preparation for more detailed geometry studies in progress.