Free Flyer Research Articles

浮遊機械のノンホロノミック可変拘束制御の提案と収束性の検討

浮遊機械のノンホロノミック可変拘束制御の提案と収束性の検討

Dynamics of geometrically-exact sandwich beams/1-D plates: computational aspects

A Galerkin projection of the complete equations of motion of geometrically-exact sandwich beams applicable to 1-D plates is presented here. The beam can take any arbitrary initial position in the 2-D space. Each layer of the beam can have different material constants with no restriction on the mass distribution and layer thickness; further, each layer can take on different length, thus allowing the modeling of multilayer structures with ply drop-offs. Finite rotation and shear deformation are accommodated for in each layer. The deformed cross section of the beam is continuous, piecewise linear. The continuity of displacement across the interlayer boundaries is exactly enforced. Extensive numerical examples including sandwich beams with three identical layers, sandwich structures with ply drop-off, free flying and spin-up maneuver of sandwich beams are presented to illustrate the applicability and versatility of the proposed formulation.

Post-impact dynamics of two multi-body systems attempting docking/berthing

Berthing/docking of two spacecraft systems will become quite routine in future operations. The shuttle will dock with the space station during the latter's construction and operation. Malfunctioning satellites will be serviced by the shuttle or other free flyers. Ideally the rendezvous between the two spacecraft systems should be smooth, but in practice, there is always a velocity differential leading to an impact. Undesirable attitude drift, and structural motion if there are flexible components, will follow this impact. This paper studies the dynamics of two multi-body systems attempting a manipulator assisted docking/berthing considering various impact scenarios. The equations of motion for the two multi-body systems before and after docking/berthing attempt are obtained using the Lagrangian formulation for individual bodies and then eliminating the constraint forces and moments with the help of the natural orthogonal complement of the velocity constraint matrix. An impact model is developed which can handle impact from fully plastic to fully elastic. Two parameters characterizing the impact—the energy loss parameter and the friction parameter—are introduced. Simulation of the post-impact dynamics shows that the values of these parameters have significant influence on the dynamics. Whether the end-effector is free or locked also influences the dynamics. Response using a control scheme to eliminate the undesirable motion in the fully plastic case (i.e. for successful berthing) is presented.

Hearing and bat defence in geometrid winter moths.

Audiograms and behavioural responses to ultrasound reveal that male geometrid winter moths (Agriopis and Erannis spp.; Ennominae, and Alsophila aescularia; Oenochrominae), which have large wings and a slow flight, have good, broadly tuned ultrasonic hearing with best frequencies at 25-40 kHz, coinciding with the frequencies used by most sympatric aerial-hawking bats. Ultrasonic pulses (27 kHz 110 dB at 1 m) delivered at distances of 1-12 m evoked consistent reactions of free flying, male A. marginaria in the lab as well as in the field; those at < 5 m resulted in the moth spiralling or diving towards the ground, those at 5-12 m resulted in one or several changes in the flight path, but did not end on the ground. The differential reaction probably reflects whether the moth is likely to have been detected by the bat or not. The micropterous (and flightless), and hence cryptic, females have strongly reduced tympanic organs and are virtually deaf. Sexual dimorphism in hearing and behavioural reactions to ultrasound reflect differential natural selection on males and females by bats. Natural selection on the hearing of the males thus seems to occur although they fly in late autumn and early spring, when bat activity is much reduced.

Let spectra measurements on LDEF: Variations with shielding and location

LET spectra measurements made with passive plastic nuclear track detectors (PNTDs) were found to depend on detector orientation, shielding and experiment location. LET spectra were measured at several locations on LDEF as part of the P0006 LETSME experiment (Benton and Parnell, 1984), the P0004 Seeds in Space experiment (Parks and Alston, 1984), the A0015 Free Flyer Biostacks and the M0004 Fiber Optics Data Link experiment (Taylor, 1984). Locations included the east, west and Earth sides of the LDEF satellite. The LET spectra measured with PNTDs deviated significantly from calculations, especially for high LET particles (LET ∞·H 2O ≥ 100 keV/ μm). At high LETs, short-range inelastic secondary particles produced by trapped proton interactions with the nuclei of the detector were found to be the principal contributor to LET spectra. At lower LETs, the spectra appeared to be due to short-range, inelastic and stopping primary protons, with primary GCR particles making a smaller contribution. The dependence of LET spectra on detector orientation and shielding was studied using the four orthogonal stacks in the P0006 experiment. Both measurements of total track density and LET spectra showed a greater number of particles arriving from the direction of space than from Earth. Measurements of LET spectra in CR-39 PNTD on the east (leading) and west (trailing) sides of LDEF showed a higher rate of production at the west side. This was caused by a larger flux of trapped protons on the west side as predicted by the east/west trapped proton anisotropy in the South Atlantic Anomaly (SAA). Track density measured in CR-39 PNTDs increased as a function of shielding depth in the detector stack. A similar measurement made in a thick stack of CR-39 interspersed with layers of Al and exposed to 154 MeV protons at a ground-based accelerator showed a similar result, indicating that a significant fraction of the particle events counted were from secondaries and that the total cross-section for production of proton-induced secondaries increased as the energy of primary protons attenuated. Little change was seen in either total differential or integral LET spectra as a function of shielding depth, indicating that the increase in cross section with decreasing proton energy affected mostly the shorter range secondary components. Similarity in the slopes of LET spectra from ground-based proton exposures and the A0015 LET spectra showed that modeling of a monoenergetic proton beam transported through a 1-D geometry was a useful first step in modeling the production of secondary particles by trapped protons in the SAA.

On-orbit thermal behaviour of the IRTS cryogenic system

The IRTS (Infrared Telescope in Space) was launched at 08:01 on 18 March 1995 UT by the H-II rocket as a part of the Space Flyer Unit (SFU), which is a re-usable free flyer designed as a multi-purpose common facility for scientific and engineering experiments. The He II tank was estimated to be approximately 85% full at 1.84 K at the moment of launch, 11 h after pumping was disconnected and the tank was sealed. The vapour evacuation through a porous plug was resumed 28 min after the launch. The thermal state reached the anticipated steady state at 1.91 K on the third day without any anomalous thermal behaviour of the porous plug in the initial zero- g state. Over the course of 10 days the SFU transferred to a low earth orbit (LEO) at 486 km from the initial phase orbit at 340 km with the telescope aperture lid ejecting on day 11 after launch. A 3He refrigerator was then activated to decrease the temperature of some bolometer detectors down to 302 mK for observations in the far IR region. Every detector worked quite satisfactorily. The stable thermal state of He II at 1.91 K was maintained until the depletion of He II at 09:30 on 24 April UT. The cold life is found to be fairly close to the prediction on the basis of the ground test data. On April 27 the sun shield was jettisoned for the safe retrieval by a US shuttle in January 1996, and the IRTS mission was completed because of the regular shift of the SFU mission time-line to another experiment. In this report the flight data of the thermal performance of the cryogenic system are discussed.

SOLCON Solar Constant Observations from the ATLAS Missions

The solar constant observations obtained by the SOLCON/ATLAS experiment during the three successive missions are presented based on the Space Absolute Radiometric Reference (SARR) defined during the ATLAS‐2 mission. The objectives of SOLCON, namely to obtain accurate measurements of the solar constant and to compare them with the observations obtained from free flyers in the hope of establishing a baseline and strategy for monitoring the solar constant at climate scale, have been achieved successfully with the three ATLAS missions. The long range objective of insuring the solar constant data continuity will, however, require that an alternative approach than that of the ATLAS program be found to fly and retrieve SOLCON.

Degradation of far ultraviolet reflectance of aluminum films exposed to atomic oxygen. In-orbit coating application

The drop in reflectance at the interval 82.6–174.4 nm of ultra high vacuum prepared aluminum coatings when exposed to controlled doses of atomic oxygen with average energy 0.17 eV has been measured by the first time. We show that atomic oxygen produces a much stronger effect on the far ultraviolet (FUV) reflectance of aluminum that molecular oxygen: for the same relative drop in reflectance of 40% at 82.6 nm, the required exposure to molecular oxygen is about 5000 times larger than to atomic oxygen. These measurements allowed us to calculate a higher limit of the useful lifetime of an aluminum mirror placed in a low earth orbit (LEO, 200 to 700 km altitude; oxygen atoms with energy of 5 eV). This limit was found to be as short as a few hours. To avoid the oxidation by atomic oxygen a high altitude orbit should be used. A more practical alternative may be found by placing the aluminum mirror behind a wakeshield device, a well known proposal, in a LEO. In this case, the flux of oxygen atoms impinging on the mirror would be strongly reduced and consequently the lifetime of the mirror greatly increased. We have calculated that the energy of oxygen atoms impinging on the shielded mirror would range from 0.07 to 1.8 eV. As the energy of oxygen atoms in our experiment is within that interval of energies, a plausible estimate of the lifetime expected for an in-orbit aluminum coating behind a wakeshield can be derived from our experimental measurements. For a wakeshield operating as a free flyer at a 300 km altitude orbit an aluminum mirror would suffer a negligible drop in its FUV reflectance after a time as long as 20 years, which is a stimulating prospective.

Enzyme activities and membrane lipids in Artemia cysts after a long duration space flight

In the Free Flyer Biostack Experiment (L.D.E.F. mission) investigations have shown that biological objects in a resting state can survive more than 5.5 years of exposure to the space factors in particular microgravity and cosmic rays. We have measured enzyme activities involved in metabolic pathways of sugar and lipid degradation and determined phospholipid composition. Pyruvate kinase and glucose-6-phosphate dehydrogenase activities in space-exposed cysts were higher than in earth controls after 1 hour incubation. In controls, total phospholipids remained unchanged, on the contrary they increased significantly in space-exposed cysts. The rate of metabolism of various phospholipid components was unchanged in controls allowing the development while the level of most of them decreased in space-exposed cysts except for phosphatidylcholine. Enzyme activities (acetylhydrolase, phospholipase A 2 and lyso phospholipase) involved in phospholipid degradation increased; however, activities were much higher in space-exposed cysts. In conclusion, the long duration space flight resulted in an increase of the metabolic activity correlated with a faster development within the first 20 hours of post flight incubation.

Crystal Growth of Compound Semiconductor Experiments in Free Flyer

Crystal Growth of Compound Semiconductor Experiments in Free Flyer

The development of the [formula omitted]ropean [formula omitted]trievable [formula omitted]rrier “EURECA”

Having successfully completed its first flight on 1 July 1993 the design and operational concepts of EURECA are reviewed against the experience gained from the development and first mission of EURECA. Designed as a precursor to free flying and recoverable elements of a future space station scenario the cost-effectivity, flexibility and user friendliness of the EURECA as a multi-disciplinary research platform is substantiated.

Measurements of cosmic ray nuclei with energies of some hundred MeV/nucleon in the LDEF mission

As a contribution to the FREE FLYER BIOSTACK EXPERIMENT (A0015) we have flown CR-39 plastic nuclear track detectors on board LDEF. Although low energy fully-ionized galactic cosmic rays should not reach this orbit due to geomagnetic shielding we found stopping nuclei with energies of some hundred MeV/nucleon. Directions of incidence, nuclear charge and energy spectra of these particles are presented and discussed.

Influence of a long duration exposure, 69 months, to the space flight factors in Artemia cysts, tobacco and rice seeds

Three french laboratories have participated in the Free Flyer Biostack experiment. Artemia cysts, tobacco seeds and rice caryopsis and embryos were used. Biological objects in monolayers were dead. In opposite, a large fraction of samples used in bulk survived. A stimulatory effect occurred in the first steps of development in Artemia cysts. In fact, the larval survival was unchanged or slightly reduced. In tobacco a drastic decrease in germination and survival rate was observed. Space flight did not induce genetic changes. In rice, results depend on the variety which was investigated; the growth rate stimulation in flight samples is discussed with respect to controls.

First radiobiological results of LDEF-1 experiment A0015 with Arabidopsis seed embryos and Sordaria fungus spores

This article highlights the first results of investigations on the general vitality and damage endpoints caused by cosmic ionizing radiation in dry, dormant plant seeds of the crucifer plant Arabidopsis thaliana (L.) Hennh. and the ascomycete Sordaria fimicola after 69 month stay in space. Wild-type and mutant gene marker lines were included in Free Flyer Biostack containers and exposed on earth and side tray of the LDEF-1 satellite. The damage in biological endpoints observed in the seeds increased in the side tray sample compared to the earth tray sample. For the ascospores we found different effects depending on the biological endpoints investigated for both expositions.

Effects of temperature on a moth auditory receptor

Measurements of the thoracic temperature and recordings of the spike activity of the most sensitive auditory receptor (A1 cell) were made in Empyreuma pugione (Arctiidae, Ctenuchinae). The temperature range tested (19–36 °C) is relevant for the behavior and ecology of this species. Experiments were performed during the hours of maximal flying activity in the wild: sunrise and sunset. The thoracic temperature during rest reflects that of the surrounding air; there is an increase of 3–4 °C immediately after ceasing free flying in the laboratory. The spike activity of the tympanic organ was recorded with a stainless-steelhook electrode placed beneath the tympanic nerve in the mesothorax. The A1 cell activity was studied without acoustic stimulation (spontaneous) and in response to 35-kHz acoustic pulses of 20, 40, or 100 ms duration. At all of these durations A1 cell response to saturating stimulus was analysed, while with 40-ms pulses different stimulus intensities were used (20–90 dB SPL in 10-dB steps). The number of action potentials per pulse, mean spike rate, maximal instantaneous discharge, and latency period depend strongly on air temperature, while the variation coefficients of the interspike intervals during the responses were not temperature dependent and vary non-monotonically with stimulus intensity. During responses to a saturating stimulus, the stimulus duration does not affect the activation energy, calculated from an Arrhenius plot, of different physiological features. Adaptation, studied in the responses to 100-ms pulses, is also temperature dependent. This phenomenon has two components, each of which shows different activation energies, suggesting a different membrane origin. High stimulus intensity (90 dB SPL) significantly affects the activation energy of the action potentials and mean spike rate, while the activation energy, of the maximal instantaneous discharge and latency period do not show this strong dependency. The spontaneous A1 cell spike rate varies with temperature, as does the value of the mode of the relative frequency distribution of the interspike interval. The activation energy of the spike rates measured at A1 cell responses to saturating stimuli is in good agreement with that described in amphibian innerear hair cells. It is suggested that this moth auditory receptor cell also has mechanosensitive protein channels.

Ground-based VLF measurements during pulsed electron beam emissions in the ionosphere

The major objective of the CHARGE-2B sounding rocket experiment is the generation of VLF waves using a pulsed electron beam from an ionospheric platform. The sounding rocket payload included the mother section that carried the 3-keV, 2-A electron gun, a tethered daughter and a free flying diagnostics package, both with wave receivers. The experiment included four ground-based VLF wave receivers located near the ground point of the geomagnetic field line connecting the beam-emitting payload to the Earth. Initial analysis of ground-based measurements has not shown any VLF emissions correlated with electron gun operations, although VLF signals from the beam emissions were detected by both the daughter and free flyer in the ionosphere.

Calculation of the Disturbances of a Spacecraft and Payload Combination

The motion of a rigid spacecraft/robot system can be calculated with a commercial multibody analysis software on a standard PC. The spacecraft is a rigid body with 6 DOF, the robot consists of three bodies with 3 DOF. The paper includes the calculations for a nonstabilized and a reaction wheel stabilized spacecraft (Man Tended Free Flyer - MTFF). As well the influence of the rotor effect of the robot motors as a friction model is included. Within different diagrams and tables each effect can be localized and its influences compared.

EMATS, a robot-based equipment manipulation and transportation system for the columbus free flying laboratory

This paper describes the concept for a robot-based Equipment Manipulation and Transportation System (EMATS) for the Columbus Free Flying Laboratory developed under ESA contract by a study team headed by Dornier. EMATS could not only automatically provide the greater part of the payload facility handling and logistics functions during the unmanned microgravity periods, but also perform unmanned servicing operations in conjunction with various logistics vehicles concepts and assist the crew during manned servicing from the Space Station Freedom and from Hermes. To that end, a variety of telerobotics features are foreseen such as teleoperation and supervised automatic operation from ground or from a small control station aboard the Free Flyer, Hermes, or the Space Station Freedom. The paper summarizes the overall EMATS architecture and illustrates the flexibility of the concept by results from computer graphics simulations.

European opportunities for astronomical, solar-terrestrial and Earth observation research aboard the space station freedom

The International Space Station Freedom will give opportunities over some 30 years to perform ongoing observational programmes from above the Earth's atmosphere over a band of some ± 28° centred on the equator. The scientific disciplines of astrophysics and solar-terrestrial interactions as well as Earth and environmental observation will be able to benefit from such a long lived observational platform. There are no doubts that a major part of the Space Station research will be filled primarily with microgravity and life science programmes. For European scientists in the disciplines of Space Science and Earth Observation the Space Station Freedom will also offer places to install suitable instruments. Today these are: the External Viewing Platform on the Columbus Attached Lab and specific Resource Ports for small attached payloads on the Space Station truss structure. Additionally external canisters on the Columbus Free Flying Laboratory may be implemented and access may be arranged to the Exposed Facility on the trailing end of the Japanese Experiment Module. Two major studies have laid the groundwork for our synthesized overview. These are the still ongoing Attached PayLoad Support Systems (APLSS) study and the finalized Scientific AirLock (SAL) Study Team reports from 1990/91 and 1989 respectively. In our paper we will give a critical review of some of the considered model instruments and an instrument traffic model for Space Science and Earth Observation particularly with regard to the criteria: compatibility with the ongoing scientific and technological research programmes, and space station restrictions, as well as long-term prospects—as far as this is currently available. Our report provides also an opportunity to update the earlier work against revised opportunities and against more distinct system requirements brought about by the design of all aspects continuing to harden.

A strategy for identification and development of safety critical software embedded in complex space systems

Software used in safety critical applications demands new concepts covering techniques concerning thorough analyses and design for high-integrity systems with embedded software. Categorization and implementation requirements with the overall intent to prevent reliance of safety on complex design components, to reduce the amount of safety critical software, and to separate the remaining critical part from non-critical software applications are presented. The purpose of the software criticality analysis (SCA), which has been developed for the Columbus Programme, is to analyse the system for implementation of those requirements. All software components will be categorized according to their involvement in critical functions. The SCA is demonstrated taking the rendezvous and berthing function of the Columbus Free Flyer with the Space Station Freedom as an example. For software, which remains being categorized as critical, exceptional techniques to achieve exceptional quality apply. A characterization of those managerial, development, analysis, and assurance techniques is given. They are related to the Columbus Software Development Standards forming the baseline of any Columbus Space Segment Software development process.