An underestimated onboard generated recoil force contributing to the Pioneer anomaly

The Pioneer anomaly, an unexpected acceleration of the Pioneer 10 and 11 spacecraft of ∼8.5 × 10⁻¹⁰ ms⁻² directed towards the inner Solar System, has been of great interest for the physics community during the past decade: considered explanations range from new physical concepts to conventional mechanism. It is shown that non-isotropic outgassing of the complete spacecraft structure is comparable in magnitude and direction to the effect and should be considered as a significant contribution to the anomalous acceleration. Although gas leaks from e.g. the propulsion system and propulsive mass loss mechanism have been discarded as possible explanations for the anomaly, the arguments used against such mechanisms do not apply to global outgassing from the spacecraft.     

Japan,Ballistic Missile Defence and remilitarisation

Japan's future trajectory in security policy and the extent of deviation from the post-war course of a constrained military stance have been the source of constant academic and policy debate. Japanese policy-makers have maintained that national security policy has shown no fundamental deviation, and that this can be benchmarked against a range of constant anti-militaristic principles. The advent of BMD, however, poses significant questions over whether Japan is continuing to follow a similar security trajectory. This article examines how BMD has challenged four key anti-militaristic principles—the non-exercise of collective self-defence, the non-military use of space, the ban on the export of weapons technology, and strict civilian control of the military—and uses this assessment to judge how BMD is driving remilitarisation. It concludes that BMD's impact is highly significant in transgressing these anti-militaristic principles and is thus indicating a more remilitarised security path for Japan developing now and in the future.     

Gas permeability and flow characterization of simulated lunar regolith

Recent discoveries of water ice trapped within lunar topsoil (regolith) have placed a new emphasis on the recovery and utilization of water for future space exploration. Upon heating the lunar ice to sublimation, the resulting water vapor could theoretically transmit through the lunar regolith, to be captured on the surface. As the permeability of lunar regolith is essential to this process, this paper seeks to experimentally determine the permeability and flow characteristics of various gas species through simulated lunar regolith (SLR). Two different types of SLR were compacted and placed into the permeability setup to measure the flow-rate of transmitted gas through the sample. Darcy’s permeability constant was calculated for each sample and gas combination, and flow characteristics were determined from the results. The results show that Darcy’s permeability constant varies with SLR compaction density, and identified no major difference in permeable flow between the several tested gas species. Between the two tested SLR types, JSC-1A was shown to be more permeable than NU-LHT under similar conditions. In addition, a transition zone was identified in the flow when the gas pressure differential across the sample was less than ∼40 kPa.     

Flywheel technology development program for aerospace applications

An overview of advanced flywheel development for energy storage in aerospace applications is presented. The advantages offered by this emerging technology are described and the current NASA approach toward developing the technology is presented     

Furthering our understanding of electrostatic solitary waves through Cluster multispacecraft observations and theory

Nonlinear isolated electrostatic solitary waves (ESWs) are observed routinely at many of Earth’s major boundaries by the Wideband Data (WBD) plasma wave receivers that are mounted on the four Cluster satellites. The current study discusses two aspects of ESWs: their characteristics in the magnetosheath, and their propagation in the magnetosheath and in the auroral acceleration (upward current) region. The characteristics (amplitude and time duration) of ESWs detected in the magnetosheath are presented for one case in which special mutual impedance tests were conducted allowing for the determination of the density and temperature of the hot and cold electrons. These electron parameters, together with those from the ion experiment, were used as inputs to an electron acoustic soliton model as a consideration for the generation of the observed ESWs. The results from this model showed that negative potential ESWs of a few Debye lengths (10–50 m) could be generated in this plasma. Other models of ESW generation are discussed, including beam instabilities and spontaneous generation out of turbulence. The results of two types of ESW propagation (in situ and remote sensing) studies are also presented. The first involves the propagation of bipolar type ESWs from one Cluster spacecraft to another in the magnetosheath, thus obtaining the velocity and size of the solitary structures. The structures were found to be very flat, with large scale perpendicular to the magnetic field (>40 km) and small scale parallel to the field (<1 km). These results were then discussed in terms of various models which predict such flat structures to be generated. The second type of propagation study uses striated Auroral Kilometric Radiation (SAKR) bursts, observed on multiple Cluster satellites, as tracers of ion solitary waves in the upward current region. The results of all studies discussed here (pulse characteristics and ESW velocity, lifetime, and size) are compared to in situ measurements previously made on one spacecraft and to theoretical predictions for these quantities, where available. The primary conclusion drawn from the propagation studies is that the multiple spacecraft technique allows us to better assess the stability (lifetime) of ESWs, which can be as large as a few seconds, than can be achieved with single satellites.     

Energy, chemical disequilibrium, and geological constraints on Europa

Europa is a prime target for astrobiology. The presence of a global subsurface liquid water ocean and a composition likely to contain a suite of biogenic elements make it a compelling world in the search for a second origin of life. Critical to these factors, however, may be the availability of energy for biological processes on Europa. We have examined the production and availability of oxidants and carbon-containing reductants on Europa to better understand the habitability of the subsurface ocean. Data from the Galileo Near-Infrared Mapping Spectrometer were used to constrain the surface abundance of CO(2) to 0.036% by number relative to water. Laboratory results indicate that radiolytically processed CO(2)-rich ices yield CO and H(2)CO(3); the reductants H(2)CO, CH(3)OH, and CH(4) are at most minor species. We analyzed chemical sources and sinks and concluded that the radiolytically processed surface of Europa could serve to maintain an oxidized ocean even if the surface oxidants (O(2), H(2)O(2), CO(2), SO(2), and SO(4) (2)) are delivered only once every approximately 0.5 Gyr. If delivery periods are comparable to the observed surface age (30-70 Myr), then Europa's ocean could reach O(2) concentrations comparable to those found in terrestrial surface waters, even if approximately 10(9) moles yr(1) of hydrothermally delivered reductants consume most of the oxidant flux. Such an ocean would be energetically hospitable for terrestrial marine macrofauna. The availability of reductants could be the limiting factor for biologically useful chemical energy on Europa.     

The photochemical stability of carbonates on Mars

Carbonates, predominately MgCO3, have been spectroscopically identified at a level of 2-5% in martian dust. However, in spite of this observation, and a large number of climate studies that suggest 1 to several bars of CO2 should be sequestered in carbonate rocks, no outcrop-scale exposures of carbonate have been detected anywhere on Mars to date. To address one hypothesis for this long-standing puzzle, the effect of ultraviolet (UV) light on the stability of calcium carbonate in a simulated martian atmosphere was experimentally investigated. Using 13C-labeled calcite, we found no experimental evidence of the UV photodecomposition of calcium carbonate in a simulated martian atmosphere. Extrapolating the lower limit of detection of our experimental system to an upper limit of carbonate decomposition on Mars yields a quantum efficiency of 3.5 x 10(-8) molecules/photon over the wavelength interval of 190-390 nm and a maximum UV photodecomposition rate of 1.2 x 10(-13) kg m(-2) s(-1) from a calcite surface. The maximum loss of bulk calcite due to this process would be 2.5 nm year(-1) (Mars year). However, calcite is expected to be thermodynamically stable on the surface of Mars, and potential UV photodecomposition reaction mechanisms indicate that, though calcium carbonate may decompose under vacuum, it would be stable in a CO2 atmosphere. Given the expected stability of carbonate on Mars and our inability to detect carbonate decomposition, we conclude that it is unlikely that the apparent absence of extensive carbonate deposits on the martian surface is due to UV photodecomposition in the current environment.     

Clathrate hydrates of oxidants in the ice shell of Europa

Europa's icy surface is radiolytically modified by high-energy electrons and ions, and photolytically modified by solar ultraviolet photons. Observations from the Galileo Near Infrared Mapping Spectrometer, ground-based telescopes, the International Ultraviolet Explorer, and the Hubble Space Telescope, along with laboratory experiment results, indicate that the production of oxidants, such as H2O2, O2, CO2, and SO2, is a consequence of the surface radiolytic chemistry. Once created, some of the products may be entrained deeper into the ice shell through impact gardening or other resurfacing processes. The temperature and pressure environments of regions within the europan hydrosphere are expected to permit the formation of mixed clathrate compounds. The formation of carbon dioxide and sulfur dioxide clathrates has been examined in some detail. Here we add to this analysis by considering oxidants produced radiolytically on the surface of Europa. Our results indicate that the bulk ice shell could have a approximately 1.7-7.6% by number contamination of oxidants resulting from radiolysis at the surface. Oxidant-hosting clathrates would consequently make up approximately 12-53% of the ice shell by number relative to ice, if oxidants were entrained throughout. We examine, in brief, the consequences of such contamination on bulk ice shell thickness and find that clathrate formation could lead to substantially thinner ice shells on Europa than otherwise expected. Finally, we propose that double occupancy of clathrate cages by O2 molecules could serve as an explanation for the observation of condensed-phase O2 on Europa. Clathrate-sealed, gas-filled bubbles in the near surface ice could also provide an effective trapping mechanism, though they cannot explain the 5771 A (O2)2 absorption.     

A space exploration strategy that promotes international and commercial participation

NASA has created a plan to implement the Flexible Path strategy, which utilizes a heavy lift launch vehicle to deliver crew and cargo to orbit. In this plan, NASA would develop much of the transportation architecture (launch vehicle, crew capsule, and in-space propulsion), leaving the other in-space elements open to commercial and international partnerships. This paper presents a space exploration strategy that reverses that philosophy, where commercial and international launch vehicles provide launch services. Utilizing a propellant depot to aggregate propellant on orbit, smaller launch vehicles are capable of delivering all of the mass necessary for space exploration. This strategy has benefits to the architecture in terms of cost, schedule, and reliability.