Spacelab Mission Research Articles

Crystal growth under reduced gravity

During the German Spacelab mission D1 various Crystal Growth Experiments have been successfully performed. The aim of this article is to review those growth studies which have been carried out in ellipsoidal mirror furnace systems. A Floating Zone Technique has been applied to Si whereas GaSb, InP, CdTe and (Pb, Sn) Te have been grown in quartz ampoules by the Travelling Heater Method (THM). One CdTe-growth run used a vapour zone instead of a metallic solution zone. As a main result of all experiments it could be demonstrated that semiconductor crystals may be grown under reduced gravity conditions in a nearly diffusive growth regime.

The ultraviolet color gradient in the late-type spiral galaxy M33

The ultraviolet surface brightness and color distributions for the late-type spiral galaxy M33 are derived from images at 1520 and 2490 A that were obtained by the Ultraviolet Imaging Telescope (UIT) on the Astro Spacelab mission. Although the surface brightness shows a general decline with radius, the dominant spiral arms cause significant deviations from an exponential fit. Colors in elliptical annuli become 0.2-0.3 mag bluer with increasing radius. Our measures of individual H II regions and sections of spiral arms follow this same trend. Interarm regions are redder than the arms. A metallicity gradient affecting only the colors of stars is inadequate in accounting for the observed color gradient. A plausible explanation invokes a combination of an LMC-type reddening curve and a radial gradient in the internal reddening in M33.

Ultraviolet Imaging Telescope ultraviolet images - Large-scale structure, H II regions, and extinction in M81

The study employs UV images of M81 obtained by the Ultraviolet Imaging Telescope (UIT) during the December 1990 Astro-1 spacelab mission to determine 2490- and 1520-A fluxes from 46 H II regions and global surface brightness profiles. Comparison photometry in the V band is obtained from a ground-based CCD image. UV radial profiles show bulge and exponential disk components, with a local decrease in disk surface brightness inside the inner Lindblad Resonance about 4 arcmin from the nucleus. The V profile shows typical bulge plus exponential disk structure, with no local maximum in the disk. There is little change of UV color across the disk, although there is a strong gradient in the bulge. Observed m152-V colors of the H II regions are consistent with model spectra for young clusters, after dereddening using Av determined from m249-V and the Galactic extinction curve. The value of Av, so determined, is 0.4 mag greater on the average than Av derived from radio continuum and H-alpha fluxes.

Telescience with MARCO/HOLOP on board the spacelab D2-mission as a preparation for Columbus

The implementation of the telescience concept and its test in precursor missions is mandatory for experiment operations in the Columbus era with respect to enhancements in science quality and quantity. During the German D2 Spacelab mission, scheduled for spring 1993, a fluid physics experiment (MARCO, MARangoni COnvection in an open boat) will be performed in the telescience mode, using the HOLOP-D2 (HOLographic OPtics laboratory) experiment facility. MARCO will be remotely operated by the experimenter from a USOC (User Support and Operations Center). DLR/MUSC (Microgravity User Support Center, located at Cologne, Germany) will play the role of this USOC, being connected to DLR/GSOC (German Space Operations Center, located in Oberpfaffenhofen, Germany) via remote data, voice and video lines. Telescience with MARCO/HOLOP is a joint effort between DARA GmbH (Deutsche Agentur für Raumfahrt-Angelegenheiten), DLR (Deutsche Forschungsanstalt für Luft- und Raumfahrt e.V.) and ESA (European Space Agency).

Non-linear axial vibrations of a cylindrical liquid column in zero-gravity

The non-linear response of an axially excited cylindrical liquid column consisting of frictionless liquid has been investigated for harmonic excitation with the excitation amplitude¯z0 and the forcing frequency Ω. Free non-linear surface displacement-response has been determined and shows softening liquid behavior. The results shall be used for the efficient planning of the “LICORE” (liquid columns' resonances) experiments in the second German Spacelab mission D-2.

NEPTUNE: A new expert planning tool for users in a network environment

MARS (mission activities and resources scheduler) is a planning and scheduling tool for both automatic and interactive generation of spacecraft timelines of realistic complexity, which has been extensively tested, e.g. for HERMES, EURECA, or Spacelab mission planning. In its new version it has been extended to include full distributed mission planning capability (as required for the COLUMBUS mission planning scenario) under the ESA contract NEPTUNE (new expert planning tool for users in a network environment). This paper describes the main features of the planning tool MARS in its new NEPTUNE version and sketches its applicability to the distributed mission planning scenario and for other (non-space) domains.

Directional solidification of the LiF - LiBaF 3 eutectic

The lamellar eutectic LiF - LiBaF 3 has been directionally solidified in different furnaces and special designed cartridges with growth rates between 3 and 60 mm/h and temperature gradients from 1.5 to 7°C/mm. The growth rates have been calculated from temperature measurements in the melt. The critical ratio G/v for interface stability avoiding eutectic cells has been determined. These experiments have been made in preparing experiments under μg(microgravity)-conditions during the second German Spacelab Mission D2 in spring 1993.

Possible actions of gravity on the cellular machinery.

Since the first flight of the ESA Biorack on the German Spacelab Mission D1 in 1985 evidence has been obtained that biological cells and small unicellular organisms function differently under conditions of microgravity. However, there is still lack of scientific proof that these effects are caused by a direct influence on the cells in the weightlessness condition. The question how normal gravity may play a role in cellular activity is being addressed and the results show that gravity may provide important signals during certain state transitions in the cell. These would be gravity-sensitive windows in the biological process. Also, by amplification mechanisms inside the cell, the cell may assume a state that is typical for normal gravity conditions and would change in microgravity. Experimental tools are discussed that would provide the conditions to obtain evidence for direct action of gravity and for the possible existence of gravity-sensitive windows.

Axial response of an amphora-type liquid column

Under axial microgravity, an originally circular cylindrical liquid column assumes an amphora-type geometry. The response of an axially excited amphora-type liquid column consisting of non-viscous liquid has been investigated for a harmonic excitation. Free surface displacement- and velocity-response have been determined. The results shall be used for the efficient planning of the “LICORE” experiments in the second German Spacelab mission (D-2).

Protein crystallization facilities for microgravity experiments

The first experiments demonstrating the enhancement of protein crystallization in microgravity were performed on the European Space Agency's first Spacelab mission in 1983 using the liquid/liquid interface diffusion technique and this experiment method will be continued on the European Retrievable Carrier. The current facility fromthe National Aeronautics and Space Administration employs a modified version of the “hanging drop” or the vapor diffusion technique. Protein crystal growth programs of NASA, ESA. and other national space programs now utilize a variety of instrumentation, and new methods are being developed to grow and study crystals of biological macromolecules in microgravity. This paper summarizes the present status of the NASA Vapor Diffusion Apparatus and ESA Protein Crystallization Facility.

Neurosciences research in space Future directions

Future research in the neurosciences can best be understood in the context of NASA's life sciences goals in the near term (1990–1995), mid term (1995–2000), and long term (2000 and beyond). Since NASA is planning short-duration Spacelab and International Microgravity Laboratory (IML) flights for many years to come, the acute effects of exposure to microgravity will continue to be of experimental and operational interest in the near term. To this end, major new areas of research will be devoted to ground-based studies of preflight adaptation trainers and their efficacy in preventing or reducing the incidence of space motion sickness. In addition, an extensive series of studies of the vestibular system will be conducted inflight on the IML-1 mission The IML-2 mission will emphasize behavior and performance, biological rhythms, and further vestibular studies.In the mid-term period, Spacelab missions will employ new technology such as magnetic recording techniques in order to evaluate changes in the processing of sensory and motor inputs at the brainstem and cortical level during exposure to microgravity. Two Space Life Sciences (SLS) missions planned for the mid to late 1990's, SLS-4 and SLS-5, will utilize an onboard centrifuge facility that will enable investigators to study the effects of partial gravity on sensory and motor function.In the long term (2000 and beyond), Space Station Freedom and long-duration missions will provide opportunities to explore new options in the neurosciences, such as sensory substitution and augmentation, through the use of physical sensors to provide three-dimensional tactile-visual, tactile-auditory and tactile-somatosensory inputs. The use of this technology will be extremely important in the area of robotic telepresence. Finally, Space Station Freedom and proposed LifeSat missions will provide neuroscientists the opportunity to study the effects of partial gravity and microgravity on neuronal plasticity.

Response of a Nonviscous Liquid Column and Layer with Anchored Liquid Surface to Axial Excitation

The response of an axially excited cylindrical liquid column consisting of frictionless and incompressible liquid has been investigated for a harmonic excitation. The column is located between two discs such that the free liquid surface exhibits there a stuck-edge boundary condition. Free surface displacement and velocity response have been determined. The results will be used for the efficient planning of the "LICOR" experiments in the second German Spacelab mission (D-2).

The manned space-laboratories control centre - MSCC: Operational functions and its implementation

This paper describes the functions of the MSCC during the operations of the Columbus Attached Laboratory and the Free Flying Laboratory as part of the In-Orbit-Infrastructure Ground Segment. For the Attached Laboratory, MSCC payload operations coordination for European experiments within the Attached Laboratory and elsewhere on the Space Station Freedom will be explained. The Free Flying Laboratory will be operated and maintained exclusively from the MSCC during its 30 years lifetime. Several operational scenarios will demonstrate the role of the MSCC during routine - and servicing operations: of main importance are the servicing activities of the Attached Laboratory and the Free Flyer at the Space Station as well as servicing of the Free Flyer by the European Space Plane Hermes. The MSCC will have complex operational-, communications-and management interfaces with the IOI Ground Segment, the Space Station User community and with the international partners. Columbus User Support Centres will be established in many European member states, which have to be coordinated by the MSCC to ensure the proper reception of the scientific data and to provide them with quick access to their experiments in space. For operations planning and execution of experiments in the Attached Laboratory, a close cooperation with the Space Station control authorities in the USA will be established. The paper will show the development of the MSCC being initially used for the upcoming Spacelab Mission D-2 (MSCC Phase-1) and later upgraded to a Columbus dedicated control centre (MSCC Phase-2). For the initial construction phase the establishing of MSCC requirements, the philosophie used for the definition of the ‘basic infrastructure’ and key features of the installed facilities will be addressed. Resulting from Columbus and D-2 requirements, the sizing of the building with respect to controlrooms, conference rooms, office spare and simulation high-bay areas will be discussed. The defined ‘basic infrastructure’, consisting of standardized controlroom consoles, intercom system, video system, simulation system, timing system, public address system, office communications system and the associated networks will be presented with their main performance data. The D-2 data processing concept and associated interfaces is presented as well; although this portion of the MSCC facilities is unlikely to be used in later IOI operations activities the experience gathered during D-2 operations will be relevant for defining the Columbus (MSCC - Phase 2) configuration. A summary of the available budget and the allocation to the discussed MSCC Phase-1 facilities will be given. One chapter of the paper will present the current status and objectives of the Detailed Definition Phase (DDP) contract with industry. The last part of this presentation will address the planned implementation integration and test approach for the MSCC as a facility suitable for Columbus operations.

Response of a liquid column with respect to oscillatory rotational top and bottom excitation

The response of a cylindrical liquid column consisting of incompressible and non-viscous liquid has been investigated for a rotational harmonic excitation of its bottom and top. Free surface displacement and velocity response have been determined and numerically evaluated. In addition, the transient behavior of the liquid column has been treated for a rotational bottom and top excitation which has suddenly been changed to another forcing frequency and excitation angular amplitude. Since the liquid is treated as frictionless, this response exhibits singularities at the resonance frequencies. To circumvent this problem damping has been introduced in a semi-empirical way in the resonance terms, which first limits the response amplitude and has to be measured in experiments. The results are of value for the efficient planning and evaluation of the “LICORE” (Liquid Column Resonances) experiments to be performed during the second German Spacelab Mission D-2.

U.S. SPACE PROGRAM: Fuel leak again puts shuttle on hold

Just what the National Aeronautics & Space Administration didn't need happened to it again last week. A hydrogen leak, discovered during fueling operations less than eight hours before scheduled lift-off, forced postponement of the flight of space shuttle Columbia . Already delayed twice, once by a hydrogen leak in May and once by an electronic malfunction in late August, Columbia was supposed to blast off from Kennedy Space Center in Florida to start Astro-1, the first spacelab mission since 1985. During nine or 10 days in orbit, its seven crew members, four of them with doctorates in astronomy or astrophysics, were to make round-the-clock observations above Earth's atmospheric interference, using three ultraviolet telescopes and an x-ray telescope. The Hopkins Ultraviolet Telescope is designed to study faint astronomical objects such as quasars, active galactic nuclei, and supernova remnants in the little-explored UV range below 1200 A. The Wisconsin Ultraviolet Photo-polarimeter Experiment is to measur...

Hardware development for the surface tension driven convection experiment

The Surface Tension Driven Convection Experiment is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for March 1992. Hardware is under development to establish the experimental conditions and to perform the specified measurements for both ground-based research and the flight experiment in a Spacelab single rack. Major development areas include an infrared thermal imaging system for surface temperature measurement, a CO2 laser and control system for surface heating, and, for flow visualization, a He-Ne laser and optical system in conjunction with an intensifed video camera. For ground-based work, the components of each system have been individually purchased or designed and tested. The three systems will be interfaced with the balance of the experimental hardware and will constitute a working engineering model.

Benefits of microgravity for measuring thermotransport coefficients in liquid metallic alloys

After giving a brief review of thermotransport principles, this paper describes the experimental technique used and presents the results obtained on the ground. The author determines the solutal stability conditions to be satisfied by the metal alloy so that ground thermotransport measurements are not disturbed by convection effects. The benefits of microgravity when such conditions cannot be achieved are demonstrated and the results obtained on pure Sn (isotope separation), Sn-Co, Sn-Ag and Sn-Bi during Spacelab missions in 1983 and 1985 are presented. The results of experiments carried out without the disturbing effect of convection are compared with those found in the literature (experiments or calculations carried out from liquid structure models).

Microgravity measurement assembly (MMA) for spacelab module missions

The microgravity measurement assembly (MMA) is a precision measurement facility for ground and on-orbit disturbance accelerations on board Spacelab, being currently under development by MBB/ERNO under DFVLR contract. MMA is using a new generation of micromechanical acceleration detectors developed by CSEM under ESTEC contract. Small dimensions of the triaxial sensor packages allow for installation very close to scientific experiments; mass is significantly reduced compared to conventional systems. Six or more of these mini-sensor packages are installed at the most g-sensitive experiments of Spacelab Module Missions. Acceleration and housekeeping data are processed in real time by a dedicated microcomputer and transmitted to the ground. Thus, for the first time, synchronized and comparable precision acceleration data are available in real time on ground for on-line judgement of the microgravity environment desired for experiment success, offering the possibility, for example of experiment repetition in case of excessive g-disturbances. Furthermore, MMA allows for immediate feedback to the crew concerning the microgravity effects of their dynamic behavior, with the aim of crew training towards lower disturbances. An additional mobile sensor package can be installed at vibration sources, e.g. pumps, centrifuges etc. or any arbitrary location inside the Spacelab Module. An impact hammer can be used together with MMA in order to measure in-flight structural transfer functions. The MMA on-board system and ground station and its planned utilization for the German Spacelab Mission D-2 is described.

InP growth from In solutions under reduced gravity

During the first German Spacelab Mission D1, growth of sulphur-doped InP was performed by the travelling-heater method (THM) under microgravity conditions ( μg). Compared to the 1g reference experiments, the crystal grown under microgravity conditions shows a more homogeneous dopant distribution due to the suppression of buoyancy-driven convection to a great extent. Residual dopant inhomogeneities belong to growth kinetics (type II striations) and to striations (rotationals) due to a temperature asymmetry in the monoellipsoidal mirror heater “ELLI”. With respect to different rotation rates of the sample, microscopic growth rates could be calculated for different growth periods. They show that type II striations as traces of macrosteps occur together with high growth rates.

Space Sled--a device for the investigation of the physiological effects of weightlessness.

Space Sled is a device for providing controlled linear acceleration stimuli in the microgravity environment of orbital flight. The scientific objectives of the experiments which used Space Sled on the D-1 Spacelab mission were to study aspects of otolith organ (that is, that part of the inner ear which transduces linear accelerations) function and adaptation in weightlessness. Space Sled comprises electrical and mechanical sub-systems. The latter is made up of a carriage running on twin rails that are fixed to the floor of Spacelab. The assembly is 6 m long with a working section of 3.5 m. The seat accommodating the test subject can be mounted on the carriage in any of three orthogonal positions. The carriage is coupled by a flexible steel cable to a servo-controlled electric motor which is capable of producing a peak acceleration of 2 m/s2 and peak velocity of 2.4 m/s. In the event of failure of comprehensive safety circuits in the electrical sub-system, a mechanical snubber, of crushable honeycomb construction, limits the deceleration to 20 m/s2. Mechanical structures providing carriage guidance, Sled/Spacelab interfaces, carriage latching, motor mounting and cable tensioning are detailed in the paper.