Improved space safety for astronauts

The 2003 Columbia accident demonstrated that spaceflight remains a risky and dangerous human endeavor, yet there have been few ‘unofficial’ investigations into astronaut safety. This report summarizes the findings of one such study by George Washington University's Space & Advanced Communications Research Institute—e.g. that simplicity of design may be better than complexity, that cargo missions would be better carried out robotically and that all new space transportation systems should be developed to common international standards—before examining ways that international cooperation can advance the cause of space safety. In establishing future space safety standards input from a wider range of participants (industry, universities and private research institutes, as well as space agencies, etc.) will need to be sought.     

Planetary protection—A microbial ethics approach

Planetary protection policies designed to reduce the cross-transfer of life on spacecraft from one planet to another can either be formulated from the pragmatic instrumental needs of scientific exploration, or from ethical principles. I address planetary protection concerns by starting from a normative ethical framework for the treatment of microorganisms. This argues that they have intrinsic value at the level of the individual through to the level of the community, but at the individual level this ethic can only be theoretical. This approach yields a solution to the problem of the inevitable contamination of Mars by human explorers and suggests that in some instances the local contamination of other planets may be acceptable. An exception would be where this contamination would cause destruction of microbial ecosystems. Within the framework of such an ethic, the term ‘planetary protection’ may be normatively too narrow and ‘planetary preservation’ may better describe the activity of controlling cross-inoculation of planets. I discuss an example of a contamination event that might be ethically acceptable within the framework of ‘preservation’, but would be regarded as unacceptable under current planetary ‘protection’ guidelines.     

A Formalism Supplementing Cognitive Semantics Based on Mereology

ABSTRACT

This paper is motivated by and aims to supplement Cognitive Semantics. Details of this latter prominent approach within contemporary linguistic research will not be discussed here. Rather, we focus on a formalization of the concept of Gestalt and provide a formal semantics that can be used to interpret a certain formal language (LM ₀) with respect to a universe of structured wholes (Gestalts). Since a great deal of the analyses of linguistic organization that has been provided by Cognitive Semantics since the mid-1970s is based on the concept of Gestalt, the semantics unfolded in the following may be viewed as an attempt to provide a starting point for supplementing the yet informal analyses of Cognitive Semantics by formal models. Since Gestaltists have talked about Gestalts in terms of parts and wholes, it is a natural step to make use of mereological techniques.     

Long-term evolution of Galileo operational orbits by canonical perturbation theory

Galileo operational orbits are slightly affected by the 3 to 5 tesseral resonance, an effect that can be much more important in the case of disposal orbits. Proceeding by canonical perturbation theory we show that the part of the long-term Hamiltonian corresponding to the non-centralities of the Earth's gravitational potential can be replaced by an intermediary that shows the pendulum dynamics of the 3 to 5 tesseral resonance problem. Inclusion of lunisolar perturbations requires a semi-analytical integration, which is compared with the corresponding results from the well-established Draper Semi-analytical Satellite Theory.     

Control system design of the Korean lunar lander demonstrator

In preparation for the lunar exploration program scheduled to be launched during the early 2020s in Korea, a lunar lander demonstrator, which will be used for developing and demonstrating lunar landing technologies, is being developed. The control configuration of the lunar lander demonstrator is determined with the consideration of available technologies and flight requirements. It is suggested that altitude control be achieved by clustering five 200 N monopropellant thrusters and attitude control with eight 3 N thrusters. A control algorithm designed to follow a predefined trajectory is developed using quaternion feedback. Control system configuration and control logic are verified by using computer simulations. Simulation results show that a soft landing with a touchdown velocity of less than 3 m/s is achieved. Attitude control performance is also verified using computer simulations. The developed control configuration will be further tested by hardware in the loop simulations and ground based firing tests during the next phase of the study.     

An approach to the dynamics of modular repetitive structures

The dynamics of modular structures is approached in this paper by means of the discrete Fourier transform. This method, applied to a structure with N bays and ring type boundary conditions, leads to N uncoupled systems of the size of a single bay. For other boundary conditions, it leads to a “spectrally resolved” eigenproblem, that is a form whose dominant terms in each field of frequency are evidenced. Approximate reduced models in narrow frequency fields can therefore be generated by using the “spectral condensation” technique. The method can be applied with general boundary conditions, but the present paper deals mostly with the “clamped edges” boundary condition and shows that numerical advantages can be obtained, particularly for the large space structures.     

Active measures for reducing the global climatic impacts of escalating CO2 concentrations

The buildup of CO₂ by fossil-fuel burning and associated climatic changes have become the subject of intensive investigations. Although the time scale on which significant climatic changes (e.g. mean temperature changes of several degrees, appreciable changes in global and regional rainfalls and winds, etc.) are expected to occur is long, it has been noted that the magnitude of the energy system is so vast that modifications in the primary resource mix should preferably be initiated within a decade or sooner. The notion that the most economical energy source will be replaced globally in response to longterm climate model predictions is probably false. Before policy matters of this type can be discussed reasonably, careful assessments must be made of alternative global measures that do not require curtailments of fossil-fuel applications. This study on active measures for reducing climate changes caused by escalating CO₂ concentrations deals with potentially important areas of research. We find: (a) reductions in the solar input to the Earth by reflecting sunlight directly are prohibitively costly; (b) desired changes in Earth albedo through judicious introduction of small particles can probably be accomplished at acceptable cost through the use of modified combustors on high-flying aircraft.     

Assessment on the feasibility of future shepherding of asteroid resources

Most plausible futures for space exploration and exploitation require a large mass in Earth orbit. Delivering this mass requires overcoming the Earth's natural gravity well, which imposes a distinct obstacle to any future space venture. An alternative solution is to search for more accessible resources elsewhere. In particular, this paper examines the possibility of future utilisation of near Earth asteroid resources. The accessibility of asteroid material can be estimated by analysing the volume of Keplerian orbital element space from which Earth can be reached under a certain energy threshold and then by mapping this analysis onto an existing statistical near Earth objects (NEO) model. Earth is reached through orbital transfers defined by a series of impulsive manoeuvres and computed using the patched-conic approximation. The NEO model allows an estimation of the probability of finding an object that could be transferred with a given Δv budget. For the first time, a resource map provides a realistic assessment of the mass of material resources in near Earth space as a function of energy investment. The results show that there is a considerable mass of resources that can be accessed and exploited at relatively low levels of energy. More importantly, asteroid resources can be accessed with an entire spectrum of levels of energy, unlike other more massive bodies such as the Earth or Moon, which require a minimum energy threshold implicit in their gravity well. With this resource map, the total change of velocity required to capture an asteroid, or transfer its resources to Earth, can be estimated as a function of object size. Thus, realistic examples of asteroid resource utilisation can be provided.     

An alternative approach to solar system exploration planning

Planning for the future exploration of the solar system has involved the structuring of a series of missions that address major scientific objectives at a minimum runout cost for the entire endeavor. In many cases, however, the optimal structuring of a program that would minimize the runout cost would entail an unacceptable high annual funding. Our actual planning must consider the planning wedge imposed on the National Aeronautics and Space Administration. It is vital that a plan be structured that copes with the annual restraint. If we do not recognize this, our plan will not be realized and a queing problem will result, thus negating all of our planning efforts.This paper presents ideas as to how planetary initiatives can be structured, wherein the peak annual funding is minimized. One vital aspect in the plan is to have a transportation capability that can launch a mission in any planetary opportunity. Solar electric propulsion can provide this capability. Another cost reduction approach would be to structure a mission set in a time sequenced fashion that could utilize essentially the same spacecraft for the implementation of several missions. This opportunity does exist. A third technique would be to fulfill a scientific objective in several sequential missions rather than attempt to accomplish all of the objectives with one mission. This approach might be applied to a mission currently in the planning stage designated the Saturn Orbiter Dual Probe mission. The current concept involves the delivery of a Saturn probe, a Titan probe, and a Saturn Orbiter by a one Shuttle launch. In this case, the orbiter must serve as a relay station for both probes; map the magnetosphere of Saturn; conduct a survey of Saturn's major satellites; and perform the planetological observation of Saturn itself. This mission entails the development of a complex spacecraft that would be required to have a fairly long life due to the extended mission operations at the benefit of accomplishing the mission with one launch. An alternate approach would be to break the mission into two separate elements. We could, for example, launch a Saturn orbiter carrying a Saturn entry probe. After serving as a communications relay system for the Saturn probe, the orbiter would then be specialized to map the magnetosphere of Saturn. A second launch would involve the delivery of a Titan probe by another orbiter where after delivery the orbiter would conduct the planetological observation of Saturn and its satellites. For the split-launch option, the runout cost for the two missions would be greater than the single launch option. However, optimum structuring of the two missions could materially reduce the peak annual funding.This paper presents data on the estimated cost on a year by year basis of a mission set structured to minimize the runout cost with no concern as to the peak annual funding as compared to a mission set that would yield the same scientific objectives in a slightly longer time span wherein the annual peak funding would be minimized. The consequences of this revised plan are analyzed.     

Feasibility study of astronaut standardized career dose limits in LEO and the outlook for BLEO

Cosmic Study Group SG 3.19/1.10 was established in February 2013 under the aegis of the International Academy of Astronautics to consider and compare the dose limits adopted by various space agencies for astronauts in Low Earth Orbit. A preliminary definition of the limits that might later be adopted by crews exploring Beyond Low Earth Orbit was, in addition, to be made. The present paper presents preliminary results of the study reported at a Symposium held in Turin by the Academy in July 2013. First, an account is provided of exposure limits assigned by various partner space agencies to those of their astronauts that work aboard the International Space Station. Then, gaps in the scientific and technical information required to safely implement human missions beyond the shielding provided by the geomagnetic field (to the Moon, Mars and beyond) are identified. Among many recommendations for actions to mitigate the health risks potentially posed to personnel Beyond Low Earth Orbit is the development of a preliminary concept for a Human Space Awareness System to: provide for crewed missions the means of prompt onboard detection of the ambient arrival of hazardous particles; develop a strategy for the implementation of onboard responses to hazardous radiation levels; support modeling/model validation that would enable reliable predictions to be made of the arrival of hazardous radiation at a distant spacecraft; provide for the timely transmission of particle alerts to a distant crewed vehicle at an emergency frequency using suitably located support spacecraft. Implementation of the various recommendations of the study can be realized based on a two pronged strategy whereby Space Agencies/Space Companies/Private Entrepreneurial Organizations etc. address the mastering of required key technologies (e.g. fast transportation; customized spacecraft design) while the International Academy of Astronautics, in a role of handling global international co-operation, organizes complementary studies aimed at harnessing the strengths and facilities of emerging nations in investigating/solving related problems (e.g. advanced space radiation modeling/model validation; predicting the arrivals of Solar Energetic Particles and shocks at a distant spacecraft). Ongoing progress in pursuing these complementary parallel programs could be jointly reviewed bi-annually by the Space Agencies and the International Academy of Astronautics so as to maintain momentum and direction in globally progressing towards feasible human exploration of interplanetary space.     

Synthetic observation alignment, and design implications for instruments on small satellites

Spaceborne Earth-Observation requires multi-spectral views of identical physical scenes, so that geophysical parameters can be derived from synergistic scene differences or combinations. This is traditionally achieved by mounting many instruments on a large platform, and constraining their beamshape relation and alignment — an approach inapplicable to SmallSats. However, an adequate density of image samples reports the entire ‘alias-free’ information-content of the spatially-continuous image-scene. Under these conditions sample-alignment is irrelevant; beamshape matching and alignment can be accurately synthesised by signal-processing manipulations of reported data — allowing instruments or channels to be mounted on separate platforms, without physical alignment. Current meteorological instruments vary in their image alias, but for many these limitations could be eliminated by small design changes; or a more radical change could give smaller and cheaper instruments with improved spatial resolution.     

On a lunar space elevator

We consider a space elevator system for lunar surface access that consists of a space station in circumlunar orbit, a cable reaching down to some meters above the surface and a magnetically levitated vehicle driven by a linear motor. It accelerates the load to be lifted to the speed of the cable end. Loads to be delivered are either put on the vehicle and slowed down by it or they are slowed down by a sand braking technique in a mare terrain. It is technically possible to operate this transport system nearly without fuel supply from Earth. We calculate various steel cable dimensions for a static stress maximum of $\text{1}\text{5}\text{th}$ of the tensile strength. The process of takeover is considered in detail. Five ways of eliminating the adverse large cable elongation due to the load are described. The touchdown process and behaviour of the cable after disconnection are analysed. The positive difference between the speed of the load at takeover and cable end can excite a large inplane swing motion. We propose to damp it by a dissipative pulley that hangs in a loop of wire leading to the ends of two beams mounted on the space station tangentially to the orbit, the pulley's core being connected with the load. Roll librations are damped by energy losses in the elastic beams; damping can be reinforced by viscous beam elements and/or controlled out-of-plane motions of the beams. We argue in favour of the possibility of fast deployment. The problems of vehicle vibrations and agglutination at sand braking blades are underlined and their combined experimental investigation is suggested.     

Effects of Basic Path Properties on Human Path Integration

Abstract

We investigated how path integration performance can be influenced by five basic path properties in a Virtual Reality Cube. Participants performed path-completion tasks in hallway paths with up to 12 segments. Distance information was visual, whereas turning angles were specified through vision and body senses. The ridge regression analyses suggested that path integration was affected by the number of segments, overall path length/turning angles, and the correct homing distance. Moreover, an un-correlation paradigm showed that path completion performance might be affected by participants' expectations for the correct homing distance of different paths. Implications on models of path integration were discussed.     

Got life? Hours of boredom followed by moments of sheer terror (and that''s just with the press)

It may be hoped that an initial discovery of extraterrestrial life and its disclosure will be done by accident. An event of that kind would have its own dynamic, and while communications about the discovery might be strained at times, there would be less likelihood that lines of inquiry and discourse would have already been taken by the participants and the press. In an ideal world (or worlds), the discovery would come ready-made with a picture or pictures that would be useful as an immediate verification of its reality. But such is not the way of the real world (or worlds, apparently). Lessons learned from the publication of the ALH84001 results in Science magazine are indicative of what may be a more likely scenario. Nonetheless, even that publication was held in confidence for much of the time leading up to NASA's press conference, and the science team doing the work was accordingly insulated from press inquiry while the work was underway. Envisioning a Mars sample return mission, or other, similar sort of endeavor that may involve a dedicated team of scientists—working under continual public scrutiny—it is clear that the circumstances that surround any fundamental discovery about life in the sample would be quite different. Planning for a communications strategy to support the operations of a Mars sample receiving facility (or facilities) must take those circumstances into account. An optimization of the time spent communicating the results of the facility's work should acknowledge the time and effort required, and make provisions for the work to proceed without extensive interruptions—and without being influenced by the expectations of the press or the public. This paper will discuss some of the initial planning associated with the communications strategy surrounding such a facility.     

Tractable Fragments of Fuzzy Qualitative Algebra

Abstract

In this paper we study the computational complexity of Fuzzy Qualitative Temporal Algebra (QA ^fuz ), a framework that combines qualitative temporal constraints between points and intervals, and allows modelling vagueness and uncertainty. Its tractable fragments can be identified by generalizing the results obtained for crisp Constraint Satisfaction Problems (CSPs) to fuzzy CSPs (FCSPs); to do this, we apply a general methodology based on the notion of α-cut. In particular, the results concerning the tractability of Qualitative Algebra QA, obtained in a recent study by different authors, can be extended to identify the tractable algebras of the fuzzy Qualitative Algebra QA ^fuz in such a way that the obtained set is maximal, namely any maximal tractable fuzzy algebra belongs to this set.     

Human space exploration - A global trans-cultural quest

This Viewpoint is a slightly edited version of the ‘Statement by Space Explorers on Human Space Exploration’ produced in the wake of a workshop organized by the European Space Policy Institute and held in Vienna in May 2010. While noting the cultural differences in understandings of ‘exploration’ around the world, it also affirms the phenomenon as a globe-wide, human urge, emphasizing that only the physical presence of a human being can assure the full emotional quality of exploration. It calls upon decision makers to regard human space exploration as a global trans-cultural quest that should be supported and furthered.     

The AURORA Project: Removal of plastic substrate to obtain an all-metal solar sail

The Orbital Angular Momentum Reversal (H-Reversal mode), is a new class of trajectories to get a cruise speed ranging from 12 to 20 AU/yr. To accomplish the H-reversal mode, a sailcraft needs of all metal solar sail. The solar sail envisaged by the “AURORA Project” is composed of two metallic layers (AI and Cr) deposited on plastic substrate. To obtain an all metal solar sail, required by the Project, the substrate must be removed in orbit. In order to accomplish that, two possible methods are described in this paper. The first one is based on the UV degradation of a buffer layer located between the substrate and the metallic layers. The UV degradation would be the starting mechanism that causes the interface weakness. The Diamond Like Carbon has been used as buffer layer and preliminary experimental results on its UV degradation are reported. The second method exploits the characteristic of most plastics to be etched (ashing process) by the atomic oxygen. The number density of atomic oxygen in Low Earth Orbit could be enough to remove a properly-selected plastic substrate in Short time.     

Strategic, technological and ethical aspects of establishing colonies on Moon and Mars

With the vast experience gained by Aerospace Community in the last five decades, the natural future course of action will be to expand Space Exploration. Our understanding of Moon is relatively better with a number of unmanned satellite missions carried out by the leading Space Agencies and manned missions to Moon by USA. Also a number of unmanned satellite missions and surface rover missions were carried out to Mars by those Space agencies generating many new details about Mars. While the future exploration efforts by global community will also be centered obviously on Moon and Mars, it is noteworthy that already NASA had declared its plans for establishing a Surface Base on Moon and developing the technical infrastructure required. Surface Bases on Moon and Mars give rise to a number of strategic, technical and ethical issues both in the process of development, and in the process of establishing the bases. The strategic issues related to Moon and Mars Surface Bases will be centered around development of enabling technologies, cost of the missions, and international cooperation. The obvious path for tackling both the technological development and cost issues will be through innovative and new means of international cooperation. International cooperation can take many forms like—all capable players joining a leader, or sharing of tasks at system level, or all players having their independent programmes with agreed common interfaces of the items being taken to and left on the surface of Moon/Mars. Each model has its own unique features. Among the technical issues, the first one is that of the Mission Objectives—why Surface Bases have to be developed and what will be the activity of crew on Surface Bases? Surface Bases have to meet mainly the issues on long term survivability of humans on the Mars/Moon with their specific atmosphere, gravity and surface characteristics. Moon offers excellent advantages for astronomy while posing difficulties with respect to solar power utilization and extreme temperature variations. Hence the technical challenges depend on a number of factors starting from mission requirements. Obviously the most important technical challenge to be addressed will be in the areas of crew safety, crew survivability, adequate provision to overcome contingencies, and in-situ resource utilization. Towards this, new innovations will be developed in areas such as specialized space suits, rovers, power and communication systems, and ascent and descent modules. The biggest ethical issue is whether humankind from Earth is targeting ‘habitation’ or ‘colonization’ of Moon/Mars. The next question will be whether the in-situ resource exploitation will be only for carrying out further missions to other planets from Moon/Mars or for utilization on Earth. The third ethical issue will be the long term impact of pollution on Moon/Mars due to technologies employed for power generation and other logistics on Surfaces. The paper elaborates the views of the authors on the strategic, technical and ethical aspects of establishing Surface Bases and colonies on Moon and Mars. The underlying assumptions and gray areas under each aspect will be explained with the resulting long-term implications.