Unmanned Space Research Articles

Hercules to sell aerospace business to Alliant

Making a long-anticipated move allowing it to focus on specialty chemicals, Hercules has agreed to sell its aerospace operations to Alliant Techsystems, an Edina, Minn.-based munitions supplier, in a deal worth $465 million. Under the terms of the agreement, Alliant will pay $365 million in cash and 3.5 million shares of its stock to acquire Hercules units that produce electronic equipment, Army ordnance, and rocket motors for unmanned space launches and military missiles. Alliant also will get a Hercules subsidiary, Global Environmental Solutions, that provides disposal and cleanup services for explosives and propellants. These units had combined 1993 revenues of $660 million and an operating profit of $105 million. They employ 5,700 people in seven states. The companies expect the deal to take effect by year's end, assuming successful negotiation of a definitive agreement and receipt of the acquired regulatory and shareholder approvals. Hercules will keep its carbon fiber and composite materials busines...

Global steering of single gimballed control moment gyroscopes using a directed search

A guided depth-first search that manages null motion about torque-producing trajectories calculated with a singularity-robust inverse is proposed as a practical feedforward steering law that can globally avoid (or minimize the impact of) singular states in minimally redundant systems of single gimballed control moment gyroscopes. Cost and heuristic functions are defined to guide the search procedure in improving gimbal trajectories. On- orbit implementation of the steering law is proposed as an extension to momentum management algorithms. A set of simulation examples is presented, illustrating the search performance for a minimally redundant, pyramid- mounted array. Sensitivities o£ feedforward gimbal trajectories are examined in the presence of unmodeled disturbances, and techniques are proposed for avoiding excessive divergence. HE next generations of manned and unmanned space- craft will require enhanced control algorithms in order to efficiently achieve their proposed mission objectives. Reg- ularly coping with uncertainties in the orbital environment, dynamically changing spacecraft configurations (i.e., via docking and buildup), nonlinear actuator properties, and the need to tolerate potential hardware failures will mandate develop- ment of control strategies considerably beyond the available state-of-the-art. Because of the priority placed on minimizing cost, weight, and consumable requirements, future spacecraft will not always be able to rely on highly complex, multiply- redundant actuator systems (as is often now the case), but must employ more flexible and intelligent schemes that effi- ciently exploit all available onboard control capability. This study has examined methods of applying heuristic search techniques to perform adaptable inverse kinematics and ac- tuator management for spacecraft attitude control. In partic- ular, single gimballed control moment gyros (SGCMGs) were chosen as torque actuators. Although many existing al- gorithms may suffice for steering double gimballed CMG (DGCMG) arrays, such as envisioned for the NASA Space Station, no powerful techniques have been developed to man- age minimally redundant arrays of SGCMGs. These devices, however, are ideally suited as momentum-exchange effectors for a wide class of future spacecraft because of their large torque output and momentum capacity. They offer significant cost, power, weight, and reliability advantages over DGCMGs and could provide attitude control for a wide variety of future spacecraft, as torque requirements in many proposed mod- erate-sized vehicles may surpass the capability of available reaction wheels. Because of the complicated nonlinear map- ping between the input (gimbal) space and output (momen- tum) space, however, effective steering laws that reliably avoid problematic singular states have not been developed for min- imally redundant SGCMG systems, discouraging their appli- cation in many situations. To fully exploit the capability of SGCMGs, intelligent steering laws must be developed that address the system nonlinearities and avoid singular states over global trajectories.

Crystallization of two bacterial enzymes on an unmanned space mission

We have grown crystals of two bacterial enzymes, thermolysin from Bacillus thermoproteolyticus and a novel 23 kD lysozyme from Streptomyces coelicolor, on the unmanned COSIMA-2 space mission. The crystals obtained under microgravity conditions were compared with crystals grown in a ground control experiment using identical hardware, and with those obtained in ‘hanging drops’ in the laboratory. For both enzymes, the space-grown crystals tended to be longer but thinner than their terrestrial counterparts. The diffraction properties of each type of crystals were assessed by collecting nearly complete diffraction data sets using an area detector. Space-grown crystals of the enzymes showed much weaker diffraction than both the ground control and the laboratory-grown crystals. Possible reasons for this are discussed.

Activities on space debris in Europe

Space debris is receiving increased attention as a growing threat to manned and unmanned space activities. It is a global issue, which may ultimately affect all users of space. As the risk posed by space debris to present and future missions reached a level which requires serious considerations and measures, especially for manned missions, ESA, together with its Member States, has initiated first steps to better understand and mitigate the problem. In this paper European efforts in the space debris field are described. In the technical area activities can be grouped into three main subdivisions, namely improved knowledge of the terrestrial particulate environment including the future evolution of the space debris population, assessment of the risk for manned and unmanned space missions, and finally, protective and preventive measures. In order to avoid serious consequences in later periods, measures to reduce the growth of the number of space debris should be initiated now.

Optimizing Launch‐on‐Time Probability

Future space projects such as space stations, large unmanned space structures, interplanetary spacecraft, and lunar and Mars bases will require highly reliable launch systems for their construction and logistic support. It may also be necessary to provide “guaranteed” commercial launches. These needs will place increased emphasis on mastering every aspect of launch‐vehicle operations, particularly a launch‐on‐time capability. Causes for delay during launch, i.e., unplanned “holds,” are attributable to several sources: weather, range activities, vehicle conditions, human performance, and so forth. In this paper, actual launch data on unscheduled hold distributions of various launch vehicles are presented. The data were supplied by industrial associate companies of the Center for Space Construction of the University of Colorado, Boulder. Probability models that can describe these historical data and be used for several purposes are determined: (1) As inputs to broader simulations of launch‐vehicle logistic space construction support processes; (2) to determine which launch operations sources cause the majority of the unscheduled holds; and (3) to suggest changes that might improve launch on time. The paper demonstrates the ability of a compound distribution probability model to fit the actual data. This model is then manipulated to develop a method for optimally improving launch‐on‐time probability.

Developmental biology on unmanned space craft.

Even the short period (6-7 min) of real microgravity during Sounding Rocket (SR) flights has provided important basic new information about the influence of the lack of gravity on particular developmental processes. However some of the reports also clearly revealed the need of an increased number of larger samples per experiment. The SR provides a very appropriate way for testing of specific flight hardware designed for experiments on long-duration missions. It was stated that the number of flight opportunities should be extended, in order to keep scientists interested in the performance of Space experiments. To this end ESA and USSR have started to collaborate in the BIOKOSMOS-9 Mission with the aim of continuing that collaboration in the future, to provide additional unmanned flight opportunities with a duration of 10-14 days. The reports on experiments performed on Biokosmos-9 showed that such missions can be a very useful extension of flight opportunities, although several of the experimental conditions should be improved. In comparison with the 1988 COSPAR meeting, the material presented at the 1990 COSPAR Session on Developmental Biology showed considerable progress in methodology: the more descriptive phase is over, the period of the actual microgravity-experiments has started, and cell- and molecular biological approaches are increasingly applied. It also became clear that in experiments with relatively small cells (plant cells, human A431 epidermoid carcinoma cells and lymphocytes) the experimental results from flight experiments were often identical to those obtained in simulated microgravity. When applicable to the biological systems involved, users should more often consider the application of such Earth-based methods, that is not only in preparation of a real Space experiment. Finally, it was emphasized that some of the results from earlier experiments, which were assumed to demonstrate real microgravity effects, might have only seemingly been due to the microgravity conditions. Instead, they could have been caused secondarily by factors such as the lack of convection in surrounding media. It is important to test this possibility in future experiments.

The Space Telescope: A Study of NASA, Science, Technology, and Politics by Robert W. Smith

TECHNOLOGY AND CULTURE Book Reviews 637 Astronomer by Chance is Lovell’s autobiography. Generally pitched at a popular level, the story moves quickly and usually gracefully. Lovell has already written at length about his life as a radio astronomer in The Story ofJodrell Bank, Out ofthe Zenith, and TheJodrellBank Telescopes. As most of Astronomer by Chance is concerned with radio astronomy, it is in part a summary of these three earlier volumes. In 1984, Dudley Saward’s uncritical biography of Lovell was published, so there is not much new on his early career, war years, and private life. It is, then, as an introduction to Lovell’s other, more detailed writings that Astronomer by Chance is most useful. The book’s central theme is modern large-scale scientific research as a product of cooperation among government, industry, and a scientific community. For the type of radio astronomy Lovell wanted to pursue, he needed big technologies on a scale that far outstripped the capabilities of the university physics department in which he was based. Lovell there­ fore turned to the engineering firm of Husband and Company to transform his and his research group’s aspirations into reality. The most spectacular example of this collaboration is the so-called Mark I radio telescope, essentially a steerable dish some 250 feet across. Its funding and construction, however, were nightmares for Lovell. He and the telescope’s builders found themselves beset by extremely tough technical difficulties and trapped in a bureaucratic maze. The rela­ tionships of technology to science, and of engineers to scientists, have of course been much studied of late. The tensions often inherent in the latter relationship have been scrutinized, but how often, for instance, do we have the example of an engineer threatening to serve a writ on a scientist for £1 million, as happened to Lovell when H. C. Husband found the quality of his work unfairly criticized by the British government’s Public Accounts Committee? (The collaboration survived and Husband built other radio telescopes for Jodrell Bank.) More generally, with Lovell’s career we are provided with an excellent case study of the dependance of scientists on engineers and patronage from national governments for much of modern scientific practice. Robert W. Smith Dr. Smith is a historian at the Smithsonian Institution’s National Air and Space Museum and an associate professor at Johns Hopkins University. His latest book is The Space Telescope: A Study ofNASA, Science, Technology, and Politics (1989). The Space Telescope: A Study ofNASA, Science, Technology, and Politics. By Robert W. Smith. New York: Cambridge University Press, 1989. Pp. xviii + 478; illustrations, notes, appendixes, bibliography, index. $39.50. The price tags of current and proposed public science projects have moved big science to the top of the national science policy agenda. As 638 Book Reviews TECHNOLOGY AND CULTURE the genome sequencing project, the Superconducting Supercollider, the space station, and the lunar-Mars initiative fight for attention and congressional support, a thorough analysis of the politics of big science is particularly timely. Robert Smith has written a detailed account of the initiation, design, adoption, and implementation of the Hubble space telescope (HST). Launched in 1990, about seven years behind schedule and at a cost of about $2.1 billion, it is the largest American commitment to unmanned space science. The Space Telescope is an important book for those interested in the history of the National Aeronautics and Space Administration (NASA) and astronomy, the politics of science, and the organization of technological research and development. Beginning in 1982, the author and his colleagues attended meetings, collected interviews, and studied correspondence, notes, and reports as part of the Space Telescope History Project. As the project’s principal product (in addition to an archive of the program), Smith’s book describes the program in considerable detail, yet in a style accessible to the general reader. After tying the project’s genesis to the evolution of astronomy, Smith launches a detailed account of the construction of the coalitions that would design the telescope and champion its development through NASA, the White House, and Congress. The second half of the book continues the theme of coalition building and maintenance while delving deeper...

Solar activity

Perhaps the most newsworthy item of recent times concerning solar activity is its unprecedented strength during the rising phase of its current 11‐year cycle. Examples of its potency include a major, well‐observed solar flare in March 1989 that launched an unusually powerful blast wave that, hitting Earth, caused spectacular low‐latitude auroras and induced currents that disabled the Quebec power system for 9 hours (6 million customers). From August through October 1989, solar flares emitted the most intense levels of solar cosmic rays measured since the beginning of the Space Age; one flare produced more cosmic rays than the previous solar cycle in total. Radiation damage to the Magellan spacecraft, en route to Venus on a radar mapping mission, permanently reduced its solar‐cell output by 10%. Excessive heating caused the Earth's upper atmosphere to rise, prematurely downing the one spacecraft capable of monitoring solar activity from orbit, the Solar Maximum Mission. Implications for the manned and unmanned space program of record‐breaking solar activity are still being assessed.

Journey into Space: The First Three Decades of Space Exploration

From NASA headquarters and the Pentagon to the edge of the solar system, an unrivaled history of America's unmanned space program. A space scientist for 30 years, Murray chronicles our rise and decline in space and calls for a return to greatness. Illustrated.

Space Radiation Biology of Fish Embryos.' The Effects of Protons

Development of fish eggs (Oryzias latipes) will be studied in a small unmanned space platform SFU (Space Flyer Unit) launched by Japan around 1993. In such experiments, to assess the microgravity effects justly, radiation effects on the fish embryos should be investigated beforehand. We irradiated the fish embryos (at the developmental stage 11 of this species) with proton beams (5.7 MeV) generated by a tandem-type Van der Graaff accelerator. The relationship between the dose delivered by protons and the percentage of hatching fry was established. The energy loss of protons after passing Mylar foil of different thickness was measured. More embryos survived when they were irradiated with protons after a thick Mylar foil. From consideration of the geometry of the fish eggs, it was supposed that embryos received proton energy at a plateau portion before the Bragg peak.

Microdialysis crystallization chamber: Design of a solvent exchangeable microsialysis crystallization system for manual or automatic control of protein crystal growth at microgravity

Several microdialysis crystallizing chambers (MDCC) are being developed to be used in microgravity (μG) situations where crystallization experiments could be performed on unmanned space flights of long duration. Disturbance of the crystal during growth and during recovery is to kept to a minimum.

Automated space vehicle control for rendezvous proximity operations

Rendezvous during the unmanned space exploration missions, such as a Mars Rover/Sample Return, will require a completely automatic system from liftoff to docking. A conceptual design of an automated rendezvous, proximity operations, and docking system is being implemented and validated at the Johnson Space Center (JSC). The emphasis of this article is on the progress of the development and testing of a prototype system for control of the rendezvous vehicle during proximity operations that is currently being developed at the JSC. Fuzzy sets are used to model the human capability of common sense reasoning in decision-making tasks and such models are integrated with expert systems and engineering control system technology to create a system that performs comparably to a manned system.

Now — A concise, comprehensive, and Lavishly illustrated account of the unmanned space program

Now — A concise, comprehensive, and Lavishly illustrated account of the unmanned space program

A History of Iridium

The use in unmanned space craft of iridium to encapsulate the radioisotope thermoelectric generators, where temperatures of up to 2000°C have to be withstood over several years of operation, with possible impact velocities of 90 metres per second, has focused greater attention on the remarkable properties of this member of the platinum group of metals. But these same properties of very high melting point and great mechanical strength have been the cause of difficulties in its melting and fabrication over a long period of years. How these problems were tackled and eventually overcome is described in this article.

Now - A Concise, Comprehensive, and Lavishly Illustrated Account of the Unmanned Space Program

Now - A Concise, Comprehensive, and Lavishly Illustrated Account of the Unmanned Space Program

Board advocates more unmanned space missions

The United States space program should acquire space transportation and launch systems that will allow manned missions to be used when they are “needed and can be most effective” and allow unmanned vehicles to be “the carrier of choice for other missions,” according to a statement released May 21, 1986, by the Space Science Board of the National Research Council (NRC).

Now-A Concise, Comprehensive, and Lavishly Illustrated Account of the Unmanned Space Program

Now-A Concise, Comprehensive, and Lavishly Illustrated Account of the Unmanned Space Program

Space Activities-A Review and a Look Ahead

The paper reviews the progress made in manned and unmanned space programs during the last 25 years and names several major accomplishments. The ingredients of success are identified as good engineering, good technology, and good management of a very complex enterprise. An argument is made that the pace of progress will be governed not by technological advances, which can be very rapid, but rather by future institutional arrangements, which are much slower to evolve. It is predicted that the most likely space activities for the next 20 years will be those relating to space commercialization, and several examples are cited. A hope is expressed that policy makers and entrepreneurs will match the spirit of adventure and risk-taking exhibited by engineers in exploring uncharted territory.

Television Systems and Slow-Scan Vidicons on NASA Space Probes

The television camera was and still remains one of NASA's scientific tools for the exploration of outer space. Unmanned probes have penetrated space to examine the moon, Mercury, Venus, Mars, Jupiter, and Saturn. As components of their scientific packages, the Ranger, Surveyor, Mariner, Mars Orbiter, and Voyager probes incorporated television subsystems with slow-scan vidicons as their imaging sensors to photograph these bodies. This paper examines the use of slow-scan vidicons and their television cameras on NASA's unmanned space probes in the exploration of our solar system.

Lunar Impact: A History of Project Ranger

Complete history of the Ranger project is provided as a tool for understanding the evolution and operational form of NASA's continuing progress of unmanned space exploration. Basic management techniques, flight operating procedures and technology for NASA's later unmanned lunar and planetary missions were reviewed. Methods for selecting experiments and integrating them with the spacecraft were also investigated.