Packaging of thick membranes using a multi-spiral folding approach: Flat and curved surfaces

Elucidating versatile configurations of spiral folding, and investigating the deployment performance is of relevant interest to extend the applicability of deployable membranes towards large-scale and functional configurations.In this paper we propose new schemes to package flat and curved membranes of finite thickness by using multiple spirals, whose governing equations render folding lines by juxtaposing spirals and by accommodating membrane thickness. Our experiments using a set of topologically distinct flat and curved membranes deployed by tensile forces applied in the radial and circumferential directions have shown that (1) the multi-spiral approach with prismatic folding lines offered the improved deployment performance, and (2) the deployment of curved surfaces progresses rapidly within a finite load domain. Furthermore, we confirmed the high efficiency of membranes folded by multi-spiral patterns.From viewpoints of configuration and deployment performance, the multi-spiral approach is potential to extend the versatility and maneuverability of spiral folding mechanisms.     

Planetary Accumulation with a Continuous Supply of Planetesimals

Previous calculations of the accumulation of small (∼10 km) planetesimals at ∼1 AU to form Mars-sized bodies assumed that the initial assemblage of planetesimals were all present at the outset. This is an obviously reasonable assumption in systems in which the time scale for growth time of ∼10²⁶ g planetary bodies is long compared to estimates of the evolutionary time scale of a protosolar disk, as was the case in the pioneering work of Safronov (1969). It is now found that as a result of the preplanetary assemblage being unstable with respect to the runaway growth of the largest bodies, this is unlikely to be the case. The more realistic alternative of adding the initial planetesimals on a ∼10⁵ year time scale is considered here, as well as the consequences of the initial planetesimals being considerably smaller than those assumed previously. It is found that although the time scale for runaway growth is now actually controlled by the availability of planetesimals, for planetesimal production time scales of ∼10⁵ yrs, the final consequences are very similar. These calculations do show, however, that as a consequence of continuous infall during the runaway growth process, the late initial planetesimals are likely to be catastrophically disrupted by mutual collisions. For this reason, a more detailed treatment of the growth of planetesimals into planetary embryos will require a better understanding of the difficult problem of formation of the initial planetesimals themselves. This revised version was published online in June 2006 with corrections to the Cover Date.     

High-Definition Television System Onboard Lunar Explorer Kaguya (SELENE) and Imaging of the Moon and the Earth

The High-Definition television (HDTV) system onboard the Japanese lunar explorer Kaguya (SELENE) consists of a telephotographic camera and a wide-angle camera that each have 2.2 M-pixel IT-CCDs (interline transfer charge-coupled devices) and LSIs (large-scale integrated circuits) of the several-million-gates class. One minute-long motion pictures acquired by the HDTV system at 30 fps (frames per second) are recorded in a 1 GB semiconductor memory after compression, and then transmitted to a ground station. In the development of the space-going HDTV system, a commercial ground-model HDTV system was extensively modified and evaluated for its suitability to withstand the harsh environment of space through environmental tests. The HDTV acquired a total of 6.3 TB of movies and still images of the Earth and the Moon over the mission period that started on September 29, 2007, and ended on June 11, 2009. Footage of an “Earth-rise” and an “Earth-set” on the lunar horizon were captured for the first time by the HDTV system. During a lunar eclipse, images of the Earth’s “diamond ring” were acquired for the first time. The CCDs and the instruments used in the system remained in good working order throughout the mission period, despite the harsh space environment, which suggests a potential new approach to the development of instruments for use in space.     

Capability for ozone high-precision retrieval on JEM/SMILES observation

We estimate the capability of ozone (O₃) retrieval with the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) instrument attached to the Exposed Facility of the Japanese Experiment Module (JEM) on the International Space Station (ISS). SMILES carries a 4-K mechanical refrigerator to cool superconducting devices in space. Since SMILES has high sensitivity thanks to the superconducting receiver, it is expected that SMILES has ability to retrieve O₃ profiles more precisely than the previous millimeter–submillimeter limb measurements from satellites.     

Design concept of Quasi Zenith Satellite System

The Quasi Zenith Satellite System, a Japanese satellite navigation system, is under development. The system broadcasts GPS-interoperable and augmentation signals as well as original Japanese signals from an inclined, elliptical geosynchronous orbit. Using this system, users around Japan and Oceania can use seamless positioning, navigation, and timing services, even in urban canyons and mountainous areas. A government policy supports the project to promote the use of geographical spatial information linked to satellite-based navigation for a wealthy and secure life in accordance with the rapid increase of satellite navigation users nationwide. To support that policy, JAXA is in charge of developing the first stage of QZSS in collaboration with related ministries and national institutes. Attention is devoted to making the system reliable and economical using legacy Japanese GEO satellite system technologies, not only satellite technology, but also ground systems and operations technologies.     

CASH 2021: commercial access and space habitation

Issues about commercialization of space have been a growing concern in the past decade for the space community. This paper focuses on the work from a team of 51 students attending the Summer Session Program of the International Space University in Bremen, Germany. CASH 2021 (Commercial Access and Space Habitation) documents a plan that identifies commercial opportunities for space utilization that will extend human presence in space, and will chart the way forward for the next 20 years. The group selected four commercial sectors that show the most promise for the future: tourism, entertainment, space system service, assembly and debris removal, and research and development/production. The content of this document presents the results of their research. Historical activities in each of the commercial sectors are reviewed along with the current market situation. To provide a coherent background for future commercialization possibilities a scenario has been developed. This scenario includes a postulated upon ideal future and includes social, political and economic factors that may affect the space industry over the timeline of the study. The study also presents a roadmap, within the limited optimistic scenario developed, for the successful commercialization of space leading to future human presence in space. A broad range of commercially viable opportunities, not only within the current limits of the International Space Station, but also among the many new developments that are expected by 2021 are discussed.     

Shape optimization of a three-dimensional membrane-structured solar sail using an angular momentum unloading strategy

A shape of the satellite’s solar sail membrane is essential for unloading angular momentum in the three-axis stabilized attitude control system because the three-dimensional solar sail can receive solar radiation pressure from arbitrary directions. In this paper, the objective is the shape optimization of a three-dimensional membrane-structured solar sail using the angular momentum unloading strategy. We modelled and simulated the solar radiation pressure torque, for unloading angular momentum. Using the simulation system, since the unloading angular momentum rate is maximized, the shape of the three-dimensional solar sail was optimized using a Genetic algorithm and Sequential Quadratic Programming. The unloading velocity in the optimized shaped solar sail was greatly improved with respect to a conventional flat or pyramid solar sail.     

Changes in prevalence of subjective fatigue during 14-day 6° head-down bed rest

The present study examines the prevalence of subjective fatigue in young healthy males during 14 days of 6° head-down bed rest (HDBR) by using a multidimensional questionnaire. Forty-one subjects completed the Subjective Fatigue Scale questionnaire to assess the fatigue-related complaints and symptoms. The questionnaire is composed of three sections, with 10 items each. The sections measured drowsiness and dullness (Section 1), difficulty in concentration (Section 2), and the projection of physical disintegration (Section 3). The subjects answered simple questions between 1400 and 1700 on 6 measurement days before and during the HDBR period. The prevalence rate of low back pain was markedly high (80.5%) on the second day and more than 50% in the first half of the HDBR period, and any complaints related to either a lack of sleep or a deterioration in the quality of sleep continued until the end of the HDBR period. Our findings may be useful in developing preventive strategies against physical and mental fatigue associated with prolonged HDBR, horizontal bed rest, and microgravity environments.     

Japanese moon lander SELENE-2—Present status in 2009

JAXA is planning exploration missions to the moon, following upon the Kaguya (SELENE) mission., These missions aim to demonstrate some new technologies, observe the moon scientifically, investigate technical, social and political feasibility of utilizing the moon. For the first step of the missions, the phase A study of SELENE-2 has started from the summer of 2007. This mission will demonstrate the effectiveness of several technologies including precision landing, hazard avoidance, surface mobility, and night survival technologies. In situ geological and geophysical observations will be conducted to improve our knowledge on the origin and the evolution of the moon. Investigating the lunar surface conditions and its potential for in situ resource utilization will provide key information for future human exploration missions. This paper presents the current status of the SELENE-2 mission, its objectives, its design, and other important aspects of its development such as international cooperation.     

JUXTA: A new probe of X-ray emission from the Jupiter system

For the future Japanese exploration mission of the Jupiter’s magnetosphere (JMO: Jupiter Magnetospheric Orbiter), a unique instrument named JUXTA (Jupiter X-ray Telescope Array) is being developed. It aims at the first in-situ measurement of X-ray emission associated with Jupiter and its neighborhood. Recent observations with Earth-orbiting satellites have revealed various X-ray emission from the Jupiter system. X-ray sources include Jupiter’s aurorae, disk emission, inner radiation belts, the Galilean satellites and the Io plasma torus. X-ray imaging spectroscopy can be a new probe to reveal rotationally driven activities, particle acceleration and Jupiter–satellite binary system. JUXTA is composed of an ultra-light weight X-ray telescope based on micromachining technology and a radiation-hard semiconductor pixel detector. It covers 0.3–2 keV with the energy resolution of <100 eV at 0.6 keV. Because of proximity to Jupiter (∼30 Jovian radii at periapsis), the image resolution of <5 arcmin and the on-axis effective area of >3 cm² at 0.6 keV allow extremely high photon statistics and high resolution observations.