Some principles of space strategy (or ‘Corbett in orbit’)

There is still little theory on the strategic use of space. Some have proposed naval theorist A.T. Mahan as a guide but this viewpoint argues that, while the analogy with sea power makes sense, it is the naval theories of Sir Julian Corbett that are most apt. Parallels are drawn between the latter's emphasis on attacking commerce as the best means of crippling a seafaring state and the implications of the current US dependence on trade in information. Ways for the USA to mitigate its vulnerability in this area are suggested.     

Some thoughts on space station science

US government proposals to cut the scientific budget of the ISS are placed within the historical context of the US space program. The author divides this into three phases—early days to the end of Apollo, the Shuttle era, and the Space Station era—and shows that all of these have suffered from decisions to reduce scientific capabilities. Even without cuts, it is unlikely that the Station can produce scientific outcomes that are commensurate with the investment that has taken place and it is imperative that policy makers learn from the lost opportunities of the two earlier phases if greater disappointment is to be avoided.     

Formation of required transfer zero location in the multiconnected dynamic system

A method for providing the required location of a transfer zero set in the linear multiconnected dynamic system with an equal number of inputs and outputs is considered.     

Three-phase rectifiers that apply optimal current injection

A class of current injection based three-phase high power factor rectifiers is proposed. Low distortion of the input currents and high power factor are obtained applying near optimal current injection. The optimal current injection is discussed, and requirements it imposes to the current injection network are derived. A class of simple current injection networks that provide near optimal current injection, consisting of a transformer, two capacitors, and a number of resistors or resistance emulators is proposed. The power processed by the resistors or resistance emulators is shown to be 8.81% of the input power. Design of the current injection network is discussed, and dependence of the input current distortion on capacitance of the applied capacitors is analyzed. Volt-ampere rating of the transformer is shown to be only 0.16% of the input power. Effects caused by the output current ripple are studied, and a method for their compensation is proposed. Analytical results are experimentally verified. Switching resistance emulation is discussed and its feasibility is experimentally demonstrated     

H. J. Habing and H. J. G. L. M. Lamers (eds.), Planetary Nebulae,IAU Symposium 180

Space Science Reviews -     

A procedure for benchmarking laboratory exposures with 1 A GeV iron ions.

A new version of the HZETRN code capable of simulating HZE ions with either laboratory or space boundary conditions is under development. The computational model consists of combinations of physical perturbation expansions based on the scales of atomic interaction, multiple scattering, and nuclear reactive processes with use of asymptotic/Neumann expansions with non-perturbative corrections. The code contains energy loss with straggling, nuclear attenuation, nuclear fragmentation with energy dispersion and downshifts, and off-axis dispersion with multiple scattering under preparation. The present benchmark is for a broad directed beam for 1 A GeV iron ion beams with 2 A MeV width and four targets of polyethylene, polymethyl metachrylate, aluminum, and lead of varying thickness from 5 to 30 g/cm2. The benchmark quantities will be dose, track averaged LET, dose averaged LET, fraction of iron ion remaining, and fragment energy spectra after 23 g/cm2 of polymethyl metachrylate.     

Does the lunar surface still offer value as a site for astronomical observatories?

Current thinking about the Moon as a destination has revitalized interest in lunar astronomical observatories. Once seen by a large scientific community as a highly enabling site, the dramatic improvement in capabilities for free-space observatories prompts reevaluation of this interest. Whereas the lunar surface offers huge performance advantages for astronomy over terrestrial sites, free-space locales such as Earth orbit or Lagrange points offer performance that is superior to what could be achieved on the Moon. While astronomy from the Moon may be cost-effective once infrastructure is there, it is in many respects no longer clearly enabling compared with free space.     

Monitoring Changes in Continental Water Storage with GRACE

The Gravity Recovery and Climate Experiment, GRACE , will enable the recovery of monthly estimates of changes in water storage, on land and in the ocean, averaged over arbitrary regions having length scales of a few hundred km and larger. These data will allow the examination of changes in the distribution of water in the ocean, in snow and ice on polar ice sheets, and in continental water and snow storage. Extracting changes in water storage from the GRACE dataset requires the use of averaging kernels which can isolate a particular region. To estimate the accuracy to which continental water storage changes in a few representative regions may be recovered, we construct a synthetic GRACE dataset from global, gridded models of surface-mass variability. We find that regional changes in water storage can be recovered with rms error less than 1 cm of equivalent water thickness, for regions having areas of 4 × 10⁵ km² and larger. Signals in smaller regions may also be recovered; however, interpretations of such results require a careful consideration of model resolution, as well as the nature of the averaging kernel. This revised version was published online in August 2006 with corrections to the Cover Date.