Click for next page ( 2


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 1
1 Summary of Findings I. SUMMARY 1. The Shuttle can be an important asset to scientific research in and beyond the 1980's. All discipline groups in the study found aspects of the Shuttle capability important to their science. Each made specific recommendations in its report about scientific needs and, in some cases, about the Shuttle characteristics and modes of use. 2. An important aspect of the Shuttle system for science will be its ability to carry many large and heavy payloads into orbit with potentially substantial economies. Of all the changes that the Shuttle may bring to space science, the increased size and weight of the payloads that can be orbited with the possibility of reducing costs by simplifying design and construction and the possibility of a high rate of launch were singled out. 3. Many of the potential advantages of the Shuttle depend on the development of efficient and flexible procedures for flying multipur- pose missions and combined payloads. Most discipline groups found a need for Shuttle missions entirely dedicated to their own science but also recognized the potential savings associated with missions with multiple objectives. The study group identified some problems of instrument design and integration and, to some extent, the kinds of operational procedures that will be needed for multipurpose missions. This finding drew attention to the need for simplifying as far as possible all the steps that lie between the first concept of a space experiment and its eventual flight as a part of the Shuttle payload. 4. The ability of the Shuttle system to recover or service payloads in orbit will be of special value for large and expensive systems such as large observatories; for some less expensive payloads the economic advantages of recovery and of possible servicing are unclear. The 1

OCR for page 1
SUMMARY OF FINDINGS importance of recovery and service of payloads placed in orbit is frequently emphasized. However, if smaller, less expensive orbiting spacecraft are considered, advantages are less clear; it may be that incompatibility of Shuttle and spacecraft orbits will make visits too costly. Limits on the weight of the payload that can be returned from orbit may also restrict recovery. The economics of payload recovery and servicing must be studied further. 5. Most planetary missions can be launched with a Shuttle/ Centaur system. Some missions identified for the 1980's require additional capabilities such as might be provided by Tug, solar electric, or some other advanced propulsion system. 6. For biomedical research in space, the study identified a clear and essential requirement for the use of the manned pressurized space laboratory. 1. Many disciplines require rapid interaction between man and payload. This function appears to be adequately fulfilled in many cases by the payload specialist and his console. However, for some experiments in atmospheric or space physics in which continuous involvement of man is required, the pressurized space laboratory is highly desirable. The need for man is present, to some extent, in all disciplines. In high-energy astrophysics it is perhaps the smallest, and in biomedical research the greatest. It was the opinion of many study participants that the presence of a payload specialist in the Shuttle orbiter could serve their needs. However, this depends on the amount of his time available and on the degree to which it is possible to use the payload specialist's console as an experiment control center. For some experiments it is possible to have scientists either in a space laboratory or on the ground, linked with the payload by a high-data-rate real-time system. The latter implies the existence of capabilities similar to those suggested for the proposed independent Tracking and Data Relay Satellite (TDRS). The study participants realized that such a TDRS is only in the planning stage and see the need for further work to clarify how realistic this option is. 8. The ability to operate instruments mounted in the Shuttle bay (in the pallet mode, with or without a pressurized laboratory) is an important feature for all disciplines except the life sciences. 9. Payloads carried into orbit by the Shuttle and then released as free-flyers are major elements in most discipline programs. Most disciplines identified major programs requiring observing times considerably in excess of the 28-day maximum duration envisaged

OCR for page 1
Scientific Uses of the Space Shuttle 3 for sortie missions; the most cost-effective way of carrying out such programs is by using free-flying automated spacecraft. 10. For most discipline groups, the 28-day sortie mission duration (or even longer if possible) is judged to be very valuable. II. THE ROLE OF MAN One of the central concerns of the summer study was to explore the nature of the role that man will play in Shuttle-related science. One problem centers around the weight of the Spacelab needed to provide working space for men in addition to the crew; this weight may well place limits on the scientific payload that can be carried on some missions. In addition, the one- to four-week duration of manned Shuttle missions is considerably less than the time that many scientific programs require, leading to the belief that these programs could best be accommodated by unmanned free-flyers. Scientific interest in the Spacelab is greatest for the life sciences, which require man to work in the shirtsleeve environment of a Spacelab module. Other disciplines, if they require a pressurized module at all, would use a smaller module than would the life sciences. The weight penalties of carrying a Spacelab raise the question of whether real-time control and evaluation would be better supplied from a ground-based scientific group or from scientists carried in flight. If a communications system from the Shuttle to the ground, giving continuous global coverage with a high rate of data interchange, were available, then ground control might be preferable to carrying a manned Spacelab. This question requires further detailed study. III. SIZE OF THE PROGRAM The overall scale of Shuttle space science and the proportions of Shuttle opportunities that will go to various scientific disciplines can only be established when a realistic model of Shuttle operations becomes clearer. This model will, of course, depend very much on the funding available for space science and applications during and following the development of the Shuttle. Initial planning for Shuttle science will bring to the forefront priority choices—choices that must be faced in the near future. We can see the need for a significant effort in supporting research and technology to begin the develop- ment of payloads for Shuttle missions.

OCR for page 1
4 SUMMARY OF FINDINGS IV. LOWERING THE COST OF SCIENCE IN SPACE There is considerable hope that Shuttle-borne science will be less expensive and easier to fly than conventionally launched space science. In order to lower the cost of Shuttle science, a design and management philosophy must be instituted that provides maximum scientific flexibility and minimum restrictions and documentation. Many of the steps to be taken are clear for payloads that remain attached to the Shuttle throughout the missions. Mounting, pointing, and other systems can be developed in a single form to serve many purposes. For systems that are common to several different experimental packages, it should be possible to develop commercial units that are qualified for Shuttle use. It is crucial to set design and test criteria for flight hardware and to use a management system similar to those used for rocket-launched payloads, which are low in cost compared with satellite payloads. The reduction of overall costs in payloads that are separated from the Shuttle is a more complex question that requires detailed cost-effectiveness studies; the reduction of weight and size limita- tions may permit significant savings. Studies have suggested that savings will come from recovering and refurbishing satellites. This might be true for military and possibly commercial satellites, but the situation is less certain for scientific satellites. A sophisticated Large Space Telescope might be worth the cost to revisit and service or to return to earth, but this approach is less attractive for less expensive free-flying payloads. The costs of revisits and potential economies depend closely on the overall Shuttle flight pattern and the compatibility between the orbits needed for free-flying scientific experiments and those that the Shuttle will use for entirely different missions. On the latter missions, the Shuttle might have capability to revisit or recover the free-flyers at little additional cost. Such . questions must be answered before the choice of the least expensive and most effective ways of flying scientific missions can be ascertained. In summary, the study group found that the Shuttle will have many capabilities potentially of great value to space science. It will provide opportunities sufficiently different from the ways in which we now conduct space science that they demand innovations in management and execution if we are to minimize costs and realize the full benefits of this new space transportation system.