Aiming for the Moon: the engineering challenge of Apollo

In retrospect, the Apollo lunar programme is recognised as a political imperative, designed to illustrate American superiority in the face of Soviet competition. It was, nevertheless, also a triumph of technology over seemingly insurmountable challenges. The developments in the many aspects of engineering required to meet those challenges stand, even today, as a testament to mankind's inventiveness and perseverance. The Apollo 17 mission ended this historic first phase of manned planetary exploration in December 1972, but the legacy of the Apollo programme remains-in science, technology and culture-even 30 years on. This paper describes the guidance, navigation and control, the power subsystem, learning from mistakes, and the problems encountered by Apollo 13.     

Neutron sources for in-situ planetary science applications

There are a number of future European Space Agency (ESA) and NASA planetary science missions that are in the planning or initial study phases, where the scientific objectives include determining the surface composition, measuring planetary surface heat flow and constraining planetary chronology. The University of Leicester is developing instrumentation for geophysical applications that include γ-ray spectroscopy, γ-ray densitometry and radiometric dating. This paper describes the modelling of a geophysical package, with the Monte Carlo code MCNPX, in order to determine the impact that a neutron source would have on in-situ composition measurements, radiometric dating and, in particular, trace element detection. The suitability of 2.54×2.54 cm LaBr₃(Ce) detectors in the geophysical package for in-situ missions was examined. ²⁵²Cf, Am–Be and Pu–Be neutron sources were compared in a trade-off study to determine mission suitability, potential for thermal and electric power production, mass and shielding requirements. This study is linked to a parallel examination of the suitability of radioisotope thermal generators for in-situ planetary science applications. The aim of the modelling was to optimise the source type and detector geometry in order to measure the elemental peaks of interest with a precision of 10% or better based on the Poisson statistics of the detected counts above background.     

New millennium frontiers of luminescence dosimetry

What are the new frontiers' facing us in the new millennium with respect to luminescence dosimetry? I suggest that the first is in methodology. The fast, sensitive optically stimulated luminescence (OSL) techniques developed recently have yielded the potential for rapid environmental monitoring, multiple measurements, dose imaging, and fast readout. New vistas of applications in medical dosimetry and remote dosimetry have opened. A second frontier is literally 'out of this world'--namely, space dosimetry. Extended stays in low Earth orbit and the potential for a 1000-day mission to Mars emphasise the challenges of dosimetry in this unique radiation environment. What role does luminescence dosimetry play in this field? This talk explores the possibilities and the challenges as we seek to penetrate these new frontiers.     

Exoplanets: the quest for Earth twins

Today, more than 400 extra-solar planets have been discovered. They provide strong constraints on the structure and formation mechanisms of planetary systems. Despite this huge amount of data, we still have little information concerning the constraints for extra-terrestrial life, i.e. the frequency of Earth twins in the habitable zone and the distribution of their orbital eccentricities. On the other hand, these latter questions strongly excite general interest and trigger future searches for life in the Universe. The status of the extra-solar planets field--in particular with respect to very-low-mass planets--will be discussed and an outlook on the search for Earth twins will be given in this paper.     

Materials science issues in the Earth and planetary sciences

Earth is a dynamic planet. Solid state convection in the deep interior is coupled to the motion of about a dozen rigid plates at the surface. Earthquakes, volcanoes and mountains are located mainly at the boundaries between plates and reflect the relative motion between them. The associated deformation processes span a wide range of regimes from high temperature dislocation and diffusion accommodated creep to brittle fracture, friction, fragmentation and granular flow. There is a long history of collaboration between earth and materials scientists in modeling the relevant micromechanics and formulating appropriate constitutive relations. Materials analysis in the Earth and planetary sciences pose special challenges. Pressure and temperature conditions in the Earth's interior reach 360 GPa and 8000 K so that constitutive equations must often be extended to pressure and temperature regimes well beyond laboratory limits. Deformation occurs over a range of temporal and spatial scales difficult to simulate in the laboratory. The emergence of deformation structures spanning many spatial orders of magnitude has made Earth sciences the test bed for modern ideas of self-organization and scaling. Finally, deformation mechanisms in earth materials are extremely sensitive to environmental factors, especially water. This factor alone explains most differences between large-scale deformation structures observed on Earth and those on the other terrestrial planets. Current problems in the Earth sciences that require a better understanding of material behavior include the mechanics of the earthquake instability, the migration of magma in the crust, the source and dynamical significance of observed heterogeneity in the deep interior, and the generation of the magnetic field.     

Real-time total integrated scattering measurements on the Mir spacecraft to evaluate sample degradation in space

An instrument to measure total integrated scattering (TIS) in space was built as part of the Optical Properties Monitor instrument package and flown on the Russian Mir Space Station in a low Earth orbit. TIS at two wavelengths was measured in space at approximately weekly intervals from 29 April to 26 December 1997 and telemetered to Earth during the mission. Of the 20 TIS samples, 13 are described here to illustrate the performance of the TIS instrument. These include ten optical samples and three thermal control samples. Two optical samples and one thermal control sample were severely degraded by atomic oxygen. All samples received a light dusting of particles during the mission and an additional heavier layer after the samples returned to Earth. The initial brassboard instrument and the validation tests of the flight instrument are also described.     

The implications of the discovery of extra-terrestrial life for religion

This paper asks about the future of religion: (i) Will confirmation of extra-terrestrial intelligence (ETI) cause terrestrial religion to collapse? 'No' is the answer based upon a summary of the 'Peters ETI Religious Crisis Survey'. Then the paper examines four specific challenges to traditional doctrinal belief likely to be raised at the detection of ETI: (ii) What is the scope of God's creation? (iii) What can we expect regarding the moral character of ETI? (iv) Is one earthly incarnation in Jesus Christ enough for the entire cosmos, or should we expect multiple incarnations on multiple planets? (v) Will contact with more advanced ETI diminish human dignity? More than probable contact with extra-terrestrial intelligence will expand the Bible's vision so that all of creation--including the 13.7 billion year history of the universe replete with all of God's creatures--will be seen as the gift of a loving and gracious God.     

Life in the lithosphere, kinetics and the prospects for life elsewhere

The global contiguity of life on the Earth today is a result of the high flux of carbon and oxygen from oxygenic photosynthesis over the planetary surface and its use in aerobic respiration. Life's ability to directly use redox couples from components of the planetary lithosphere in a pre-oxygenic photosynthetic world can be investigated by studying the distribution of organisms that use energy sources normally bound within rocks, such as iron. Microbiological data from Iceland and the deep oceans show the kinetic limitations of living directly off igneous rocks in the lithosphere. Using energy directly extracted from rocks the lithosphere will support about six orders of magnitude less productivity than the present-day Earth, and it would be highly localized. Paradoxically, the biologically extreme conditions of the interior of a planet and the inimical conditions of outer space, between which life is trapped, are the locations from which volcanism and impact events, respectively, originate. These processes facilitate the release of redox couples from the planetary lithosphere and might enable it to achieve planetary-scale productivity approximately one to two orders of magnitude lower than that produced by oxygenic photosynthesis. The significance of the detection of extra-terrestrial life is that it will allow us to test these observations elsewhere and establish an understanding of universal relationships between lithospheres and life. These data also show that the search for extra-terrestrial life must be accomplished by 'following the kinetics', which is different from following the water or energy.     

The runaway greenhouse: implications for future climate change, geoengineering and planetary atmospheres

The ultimate climate emergency is a 'runaway greenhouse': a hot and water-vapour-rich atmosphere limits the emission of thermal radiation to space, causing runaway warming. Warming ceases only after the surface reaches approximately 1400 K and emits radiation in the near-infrared, where water is not a good greenhouse gas. This would evaporate the entire ocean and exterminate all planetary life. Venus experienced a runaway greenhouse in the past, and we expect that the Earth will in around 2 billion years as solar luminosity increases. But could we bring on such a catastrophe prematurely, by our current climate-altering activities? Here, we review what is known about the runaway greenhouse to answer this question, describing the various limits on outgoing radiation and how climate will evolve between these. The good news is that almost all lines of evidence lead us to believe that is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of non-condensible greenhouse gases such as carbon dioxide to the atmosphere. However, our understanding of the dynamics, thermodynamics, radiative transfer and cloud physics of hot and steamy atmospheres is weak. We cannot therefore completely rule out the possibility that human actions might cause a transition, if not to full runaway, then at least to a much warmer climate state than the present one. High climate sensitivity might provide a warning. If we, or more likely our remote descendants, are threatened with a runaway greenhouse, then geoengineering to reflect sunlight might be life's only hope. Injecting reflective aerosols into the stratosphere would be too short-lived, and even sunshades in space might require excessive maintenance. In the distant future, modifying Earth's orbit might provide a sustainable solution. The runaway greenhouse also remains relevant in planetary sciences and astrobiology: as extrasolar planets smaller and nearer to their stars are detected, some will be in a runaway greenhouse state.     

Design and performance of the cryogenic subsystem for the orbiting carbon observatory

The Space Dynamics Laboratory, under contract to Hamilton Sundstrand and NASA’s Jet Propulsion Laboratory, designed, manufactured, and tested the cryogenic subsystem for the three focal plane assemblies of the Orbiting Carbon Observatory instrument. The Orbiting Carbon Observatory is a NASA-sponsored Earth System Science Pathfinder program. During its two-year lifetime, the OCO mission will collect space-based measurements of carbon dioxide. OCO’s three focal plane assemblies are mounted to the cryogenic subsystem, which thermally isolate the focal planes from the instrument and provide a low-impedance thermal interface to the cryocooler. The hardware meets stringent requirements for stability, temperature, heat flow, contamination, mass, and volume. This paper describes design and performance characteristics, and reports test results of the cryogenic subsystem.     

The stratosphere

The stratosphere is that part of the atmosphere which lies between ca. 10 and 50 km above the surface of the Earth and which contains the ozone layer. It is the seat of much interesting behaviour in terms of dynamics, radiation and chemistry, now revealed in detail by observations from modern space instruments, but still not completely understood. Other planetary atmospheres exhibit stratospheric behaviour which in some ways resembles, and in others contrasts sharply with, that of the Earth. In reviewing these topics, this paper describes some key problems that will be addressed by new measurements from space in the near future.     

Integrated optimization of planetary rover layout and exploration routes

This article introduces an optimization framework for the integrated design of a planetary surface rover and its exploration route that is applicable to the initial phase of a planetary exploration campaign composed of multiple surface missions. The scientific capability and the mobility of a rover are modelled as functions of the science weight fraction, a key parameter characterizing the rover. The proposed problem is formulated as a mixed-integer nonlinear program that maximizes the sum of profits obtained through a planetary surface exploration mission by simultaneously determining the science weight fraction of the rover, the sites to visit and their visiting sequences under resource consumption constraints imposed on each route and collectively on a mission. A solution procedure for the proposed problem composed of two loops (the outer loop and the inner loop) is developed. The results of test cases demonstrating the effectiveness of the proposed framework are presented.     

Collisional erosion and the non-chondritic composition of the terrestrial planets

The compositional variations among the chondrites inform us about cosmochemical fractionation processes during condensation and aggregation of solid matter from the solar nebula. These fractionations include: (i) variable Mg-Si-RLE ratios (RLE: refractory lithophile element), (ii) depletions in elements more volatile than Mg, (iii) a cosmochemical metal-silicate fractionation, and (iv) variations in oxidation state. Moon- to Mars-sized planetary bodies, formed by rapid accretion of chondrite-like planetesimals in local feeding zones within 106 years, may exhibit some of these chemical variations. However, the next stage of planetary accretion is the growth of the terrestrial planets from approximately 102 embryos sourced across wide heliocentric distances, involving energetic collisions, in which material may be lost from a growing planet as well as gained. While this may result in averaging out of the 'chondritic' fractionations, it introduces two non-chondritic chemical fractionation processes: post-nebular volatilization and preferential collisional erosion. In the latter, geochemically enriched crust formed previously is preferentially lost. That post-nebular volatilization was widespread is demonstrated by the non-chondritic Mn/Na ratio in all the small, differentiated, rocky bodies for which we have basaltic samples, including the Moon and Mars. The bulk silicate Earth (BSE) has chondritic Mn/Na, but shows several other compositional features in its pattern of depletion of volatile elements suggestive of non-chondritic fractionation. The whole-Earth Fe/Mg ratio is 2.1+/-0.1, significantly greater than the solar ratio of 1.9+/-0.1, implying net collisional erosion of approximately 10 per cent silicate relative to metal during the Earth's accretion. If this collisional erosion preferentially removed differentiated crust, the assumption of chondritic ratios among all RLEs in the BSE would not be valid, with the BSE depleted in elements according to their geochemical incompatibility. In the extreme case, the Earth would only have half the chondritic abundances of the highly incompatible, heat-producing elements Th, U and K. Such an Earth model resolves several geochemical paradoxes: the depleted mantle occupies the whole mantle, is completely outgassed in (40)Ar and produces the observed (4)He flux through the ocean basins. But the lower radiogenic heat production exacerbates the discrepancy with heat loss.     

The astrophysics of crowded places

Today the Sun is in a relatively uncrowded place. The distance between it and the nearest other star is relatively large (about 200,000 times the Earth-Sun distance!). This is beneficial to life on Earth; a close encounter with another star is extremely unlikely. Such encounters would either remove the Earth from its orbit around the Sun or leave it on an eccentric orbit similar to a comet's. But the Sun was not formed in isolation. It was born within a more-crowded cluster of perhaps a few hundred stars. As the surrounding gas evaporated away, the cluster itself evaporated too, dispersing its stars into the Galaxy. Virtually all stars in the Galaxy share this history, and here I will describe the role of 'clusterness' in a star's life. Stars are often formed in larger stellar clusters (known as open and globular clusters), some of which are still around today. I will focus on stars in globular clusters and describe how the interactions between stars in these clusters may explain the zoo of stellar exotica which have recently been observed with instruments such as the Hubble Space Telescope and the X-ray telescopes XMM-Newton and Chandra. In recent years, myriad planets orbiting stars other than the Sun--the so-called 'extrasolar' planets--have been discovered. I will describe how a crowded environment will affect such planetary systems and may in fact explain some of their mysterious properties.     

Compressive pressure dependent anisotropic effective thermal conductivity of granular beds

In situ planetary thermal conductivity measurements are typically made using a long needle-like probe, which measures effective thermal conductivity in the probe??s radial (horizontal) direction. The desired effective vertical thermal conductivity for heat flow calculations is assumed to be the same as the measured effective horizontal thermal conductivity. However, it is known that effective thermal conductivity increases with increasing compressive pressure on granular beds and the horizontal stress in a granular bed under gravity is related to the vertical stress through Jaky??s at rest earth pressure coefficient. The objectives of this study were to examine the validity of the isotropic property assumption and to develop a fundamental understanding of the effective thermal conductivity of a dry, noncohesive granular bed under uniaxial compression. A model was developed to predict the increase in effective vertical and horizontal thermal conductivity with increasing compressive vertical applied pressure. An experiment was developed to simultaneously measure the effective vertical and horizontal thermal conductivities of particle beds with needle probes. Measurements were made as compressive vertical pressure was increased to show the relationship between increasing pressure and effective vertical and horizontal thermal conductivity. The results of this experiment showed quantitatively the conductivity anisotropy for two different materials and validated the developed model. This model can be used to predict the anisotropic effective thermal conductivity of granular materials under uniaxial compressive pressures, and evaluate the uncertainties in lunar heat flow measurements.     

Brittleness,fracture energy and size effect in theory and in reality

It is natural that, with the recent fast development of fracture mechanics, the meanings of some standard expressions such as brittleness, fracture energy and size effect need to be revised in order to avoid serious misunderstandings and ambiguities. The paper aims at answering such ticklish questions as the following. Can Griffith's criterion for quasi-static crack propagation, which is valid in linear-elastic fracture mechanics, be applied to the non-linear stress softening theory called the fictitious crack model? What is in fact the mutual relationship of the two theories? How can brittleness be distinctly defined? What is a brittle material and what does quasi-brittle mean? Is the fracture toughness a measure of toughness or rather a measure of strength? Is the fracture energy a material parameter and can a material parameter be ‘measured’ directly or must a theory always be used for interpreting results from experiments? What is the fundamental idea of damage mechanics? What does size effect mean? Is a size-effect law the same as a model law derived from dimensional analysis? What is in fact the relation of a model law to the theory (known or unknown) to which the model law is connected? Giving replies to such questions it is essential to distinguish between theory and reality and not to mix two or more theories, unless the mutual relations of the theories involved are taken into account.     

Remote Raman spectroscopy for planetary exploration: a review

In this review, we discuss the current state of standoff Raman spectroscopy as it applies to remote planetary applications, including standoff instrumentation, the technique's ability to identify biologically and geologically important analytes, and the feasibility to make standoff Raman measurements under various planetary conditions. This is not intended to be an exhaustive review of standoff Raman and many excellent papers are not mentioned. Rather it is intended to give the reader a quick review of the types of standoff Raman systems that are being developed and that might be suitable for astrospectroscopy, a look at specific analytes that are of interest for planetary applications, planetary measurement opportunities and challenges that need to be solved, and a brief discussion of the feasibility of making surface and plume planetary Raman measurements from an orbiting spacecraft.     

Accretion of the Earth

The origin of the Earth and its Moon has been the focus of an enormous body of research. In this paper I review some of the current models of terrestrial planet accretion, and discuss assumptions common to most works that may require re-examination. Density-wave interactions between growing planets and the gas nebula may help to explain the current near-circular orbits of the Earth and Venus, and may result in large-scale radial migration of proto-planetary embryos. Migration would weaken the link between the present locations of the planets and the original provenance of the material that formed them. Fragmentation can potentially lead to faster accretion and could also damp final planet orbital eccentricities. The Moon-forming impact is believed to be the final major event in the Earth's accretion. Successful simulations of lunar-forming impacts involve a differentiated impactor containing between 0.1 and 0.2 Earth masses, an impact angle near 45 degrees and an impact speed within 10 per cent of the Earth's escape velocity. All successful impacts-with or without pre-impact rotation-imply that the Moon formed primarily from material originating from the impactor rather than from the proto-Earth. This must ultimately be reconciled with compositional similarities between the Earth and the Moon.     

Reducing mass while improving the operational behavior: form optimization of planetary gearbox housings

The optimization of load sharing between planets is one of the most important goals in planetary gearbox design. Unevenly distributed load will cause locally higher flank pressures and therefore, less durability of gears and bearings. Furthermore, unevenly distributed or fluctuating loads can cause excitations in the gear mesh and structural vibrations. The load sharing in planetary gear stages depends on the individual stiffness conditions in each mesh position. The stiffness is not only influenced by the gear geometry but also by the surrounding structural elements like shafts, housings and torque arms. In wind industry these components are often designed very stiff in order to reduce their effect on the operational behavior.

Within this paper, a method is presented, which allows combining the structural optimization process with a tooth contact analysis for planetary gearboxes. By means of this combined approach, it is possible to optimize the housing structure of the ring gear in terms of mass reduction while keeping the operational behavior in focus. With a weighted design objective function, it is possible to decide whether the main objective should be load distribution, excitation behavior, low mass or a balanced design.

     

Temperature gradient distribution in permafrost active layer,using a prototype of the ground temperature sensor (REMS-MSL) on deception island (Antarctica)

Deception Island, an active volcano on South Shetland Archipelago of Antarctica (62°43′S, 60°57′W), is a cold region with harsh, remote and hostile environmental conditions, what could be considered in most aspects such an analog of the Martian surface. The volcanic materials on the surface, the permafrost and active layer existence, and the cold-climate conditions made this region of the Earth a perfect site to test instruments for the future missions to Mars. This is the case of the Ground Temperature Sensor (GTS), based on an infrared radiation (IR) sensor, included into the Rover Environmental Monitoring Station (REMS) instrument on board of the Mars Science Laboratory (MSL) mission of NASA, with that it will measure the Mars surface temperature.We conducted a summer Antarctic scientific campaign in 2009 on Deception Island in order to test the GTS instrument in the field. That device was placed near other already installed instruments and used to monitor permafrost and active layer thermal evolutions: air, surface and ground temperatures, as well as short and long wave radiation were registered. In brief the main objectives are (1) test in the field and improve the GTS device prototype, and (2) develop a methodology to derive soil gradient temperature in the active layer zone; which could be applied in the MSL mission.With the obtained data during 2009 campaign, we (a) compared temperatures from GTS versus our Pt100 contact temperature sensors to analyze GTS response accuracy; (b) calculated the active layer thickness using the sinusoidal heat transfer conduction model from soil surface temperature records; and (c) calculated the unfrozen active layer thermal diffusivity.The main results show that the degree of adjustment between the temperature measurements by to Pt100 contact temperature sensors and the CGT-REMS instrument is high, with a mean error value of below ± 0.6 °C although it could reach values of ± 5.0 °C due to the heating of the instrument case due to the sun. On the other hand, the calculated active layer thickness was consistent with the direct measures from both; our temperature probes placed in shallow boreholes and mechanical probing. Then, using soil surface temperature data from GTS instrument will be able to establish indirectly the active layer thickness and its thermal structure, what will have important applications for the MSL mission to Mars.