Pressure and Ionization Balances in the Circum-Heliospheric Interstellar Medium and the Local Bubble

A disconcerting mismatch of thermal pressures for two media in contact with each other, (1) the warm, Circum-Heliospheric Interstellar Medium (CHISM) and (2) the very hot material within a much larger region called the Local Bubble (LB), has troubled astronomers for over two decades. A possible resolution of this problem, at least in part, now seems possible. We now understand that earlier estimates for the average electron density in the very hot LB plasma were inflated by an unrecognized foreground contamination to the low energy diffuse X-ray background measurements. This foreground illumination arises from photons emitted by charge exchange reactions between solar wind ions and neutral atoms from the interstellar medium that enter into the heliosphere. However, with the resolution of this problem comes a new one. The high ionization fraction of helium in the CHISM, relative to that of hydrogen, could be understood in terms of the effects from a strong flux of EUV and X-ray radiation coming from both the Local Bubble and a conductive interface around the CHISM. A revision of this interpretation may now be in order, now that the photoionization rate from radiation emitted by hot gas the Local Bubble is lower than previously assumed.     

An imaging telescope for high energy gamma-ray astronomy

Recent tests of a γ-ray imaging telescope, which incorporated a coded aperture mask and multi-wire proportional counter system produced good images of a tritium target source which was used to generate the 20 MeV protons at a proton Van de Graaff accelerator. This paper indicates what performance one might expect if a large area drift chamber were used in conjunction with a coded aperture mask. The prospects for achieving significant scientific results if such a system were flown on a variety of space vehicles are discussed.     

Taming Tornadoes Storm Abatement from Space

Tornadoes represent the most dangerous and destructive of storms. This paper describes a concept for disrupting the formation of tornadoes in a thunderstorm. Beamed microwave energy from a satellite heats cold rain to affect convective forces in the storm cell. This describes a Thunderstorm Solar Power Satellite (TSPS). The TSPS is based on Space Solar Power Program (SSP) concepts and technology. The concept was evaluated in a numerical simulation using the Advanced Regional Prediction System Code at the Center for Analysis and Prediction of Storms (CAPS). Conditions for tornado formation were affected in the simulation. Additional simulation is proposed to determine the specific areas to be heated and the intensity of directed energy to affect tornadogenesis. Benefits from taming tornadoes provide a basis for initial government investment in TSPS. The potential benefits are balanced by reservations about safety. Demonstration of technology and operations may lead to commercial investment in space solar power. We conclude that the TSPS concept merits additional analysis, numerical simulation, and demonstration testing.     

Time-Dependent Nuclear Decay Parameters: New Evidence for New Forces?

This paper presents an overview of recent research dealing with the question of whether nuclear decay rates (or half-lives) are time-independent constants of nature, as opposed to being parameters which can be altered by an external perturbation. If the latter is the case, this may imply the existence of some new interaction(s) which would be responsible for any observed time variation. Interest in this question has been renewed recently by evidence for a correlation between nuclear decay rates and Earth–Sun distance, and by the observation of a dip in the decay rate for ⁵⁴Mn coincident in time with the solar flare of 2006 December 13. We discuss these observations in detail, along with other hints in the literature for time-varying decay parameters, in the framework of a general phenomenology that we develop. One consequence of this phenomenology is that it is possible for different experimental groups to infer discrepant (yet technically correct) results for a half-life depending on where and how their data were taken and analyzed. A considerable amount of attention is devoted to possible mechanisms which might give rise to the reported effects, including fluctuations in the flux of solar neutrinos, and possible variations in the magnitudes of fundamental parameters, such as the fine structure constant and the electron-to-proton mass ratio. We also discuss ongoing and future experiments, along with some implications of our work for cancer treatments, ¹⁴C dating, and for the possibility of detecting the relic neutrino background.     

Xs-MET-a reduced complexity fabrication process using complementaryheterostructure field effect transistors for analog, low power, spaceapplications

The requirements for space-based integrated circuit applications are defined with an emphasis on being radiation tolerant and low power consuming. Flexible analog signal processors (FASPs) are outlined as a means by which effective circuit designs can be utilized to perform a multitude of tasks. The development of complementary III-V technologies have been proven to meet the demands of the space environment, and have demonstrated the potential for frequency operation beyond 1 GHz using power supply voltages at or below 1.5 Volts. The novel fabrication process known as Xs-MET (pronounced kismet, which uses the Creek letter chi, X, and stands for Complementary Heterostructure Integrated Single Metal Transistor), is introduced as a manufacturing technique to be used in FASP design. The Xs-MET fabrication process is outlined with preliminary device results presented. An example of a FASP circuit design using Xs-MET is provided. Conclusions regarding the utilization of the Xs-MET process for FASPs are outlined with comments focusing on a space-based demonstration     

Synthetic Aperture Processing with Limited Storage and Presumming

The number of transmitted pulses associated with the Doppler histories of a side-looking radar may greatly exceed the desired azimuth compression ratio of the system. This discrepancy is taxing if the storage required for the azimuth processing is provided by cores, magnetic drums, and the like. Thus, as a practical matter, one considers presumming of the data prior to correlation in an attempt to achieve the desired performance with a minimum amount of digital storage. In this paper, the optimum (in terms of resolution) presummer is derived, along with the optimum apportionment of the available storage capacity between the presumming and correlation operations. Under the condition (or generally pessimistic approximation) that the illumination pattern of the antenna uniformly illuminates a Doppler bandwidth equal to the PRF of the radar, the optimum presumming coefficients are the first Np Fourier coefficients of a function which is one of the Doppler bandwidth to be correlated and zero on the remainder of the PRF bandwidth, where Np is the number of transmitted radar pulses over which presumming is provided. Increasing Np reduces the degradation due to presumming, but may leave inadequate storage for correlation. Hence, we optimize the apportionment between the two operations and present the obtainable resolution as a function of total storage and the number of transmitted pulses in the received Doppler history.     

Error Reduction in HF Loop DF Systems

Techniques for reducing bearing errors in vertical loop HF direction finders for ionospherically propagated signals were evaluated in a dual-channel system. A main channel provides a bearing display from the output of a rotating loop; an auxiliary channel unblanks the bearing ng display when propagation conditions are favorable for minimum bearing error. Circuitry to provide optimum unblanking for a wide variety of signal and fade conditions is described. The results of an operational evaluation are presented and show that a large majority of the unblanked bearings can be restricted to ±15° of the great-circle bearing with average bearing errors of 10° or less. Operational comparison with a contemporary system shows that the dual-channel system performance is superior with a 2 to 1 reduction ion in bearing spreads, standard deviations, and RMS error.     

激光诊断技术在脉冲爆震发动机研究中的应用

在美国海军研究生院及斯坦福大学的脉冲爆震发动机（PDE）模型上，应用两种新发展的二极管激光诊断技术－光吸收／高温辐射组合测定法和多路复合可调二极管激光（TDL）技术，测量了其中的温度、各燃烧产物组分等重要参数，并与传统方法所得结果进行对比，说明新方法可靠、准确，适合爆震燃烧流场这种特殊环境，测量精度更高，而且更加简便、快捷。     

The Student Dust Counter on the New Horizons Mission

The Student Dust Counter (SDC) experiment of the New Horizons Mission is an impact dust detector to map the spatial and size distribution of dust along the trajectory of the spacecraft across the solar system. The sensors are thin, permanently polarized polyvinylidene fluoride (PVDF) plastic films that generate an electrical signal when dust particles penetrate their surface. SDC is capable of detecting particles with masses m>10^?12 g, and it has a total sensitive surface area of about 0.1 m², pointing most of the time close to the ram direction of the spacecraft. SDC is part of the Education and Public Outreach (EPO) effort of this mission. The instrument was designed, built, tested, integrated, and now is operated by students.     

Low cost guidance for the Multiple Launch Rocket System (MLRS)artillery rocket

The US Army Aviation and Missile Command has demonstrated the application of advanced technology to significantly improve the accuracy and range of the Multiple Launch Rocket System (MLRS) through the Guided MLRS Advanced Technology Demonstration (ATD). The addition of a cost-effective guidance and control package to the rocket results in a weapon system that can defeat the target at ranges up to 70 km with significantly fewer rounds. This not only increases the destructive capability of the system but also reduces the cost of the expended ammunition, the cost to transport the ammunition to the combat zone, and the number of launchers required to execute the mission. The guidance kit is housed in the nose of the MLRS and consists of an Inertial Measurement Unit (IMU), four independent electromechanically actuated canards, a GPS receiver, GPS antennas, a thermal battery, a guidance computer, and power supply electronics. Roll decoupling of the warhead and motor section was required to allow roll control of the guidance section to enable accurate inertial navigation and was accomplished by joining the two sections with a roll bearing. Five flight missiles were built and tested during the ATD. A tightly coupled eight channel GPS receiver was flown on all flights. This paper discusses the ATD development effort and presents flight test results