40 THE FIVE-YEAR OUTLOOK 



commercial concerns, and foreign governments (NS: 

 SPACE). It may be. therefore, that if the reaUzed traffic 

 model grows significantly, the fourorbiters already sched- 

 uled for production will eventually have to be augmented 

 to realize the system's full potential. In addition, some 

 planned payloads will require greater service facilities, 

 more power, and longer stay-times in space than the cur- 

 rent system can provide (NRC-9). 



THE STATUS AND USES OF THE SYSTEM 



The Space Transportation System is expected to replace, 

 progressively through the 1980s, the expendable launch 

 vehicles on which the space programs of this Nation and 

 other nations have so far relied. It will consist of the Space 

 Shuttle, the European-developed Spacelab. and upper 

 stages for boosting payloads from the Shuttle's low-Earth 

 orbit to higher orbits (NRC-9). 



Full development and exploitation of the Shuttle system 

 provide a wide range of exciting opportunities for the use 

 of space. Several of those opportunities are expected to be 

 realized during the next 5 years. For example, the Shuttle 

 will be able to transport a wide variety of payloads as large 

 as 15 feet in diameter and 60 feet long and weighing as 

 much as 65.000 pounds. In addition, it can launch, serv- 

 ice, and retrieve free-flying spacecraft. A Shuttle orbiter 

 with a Spacelab mounted in its cargo bay will provide a 

 low-Earth-orbit space platform with a stay-time in space 

 of up to 7 days or longer Because of the potential ease of 

 carrying out some processes in the near-zero gravity en- 

 vironment of space, investigations in materials processing 

 during the next 5 years are expected to lay the groundwork 

 for the commercial production of new and superior mate- 

 rials in space (NRC-9). Also, the greater access to space 

 provided by the Shuttle is expected to improve current 

 capabilities for remote sensing of Earth and its environ- 

 ment. Satellites will be inserted into Earth orbit from the 

 Shuttle, thereby lessening the need for expendable launch 

 vehicles and easing limitations on the weight and size of 

 payloads. It also is anticipated that the Shuttle will provide 

 unique opportunities in infrared and optical solar astrono- 

 my. The launching of a life science laboratory is another 

 possibility currently being examined (NRC-17; SPACE). 



In addition to providing many new opportunities for 

 studying and using the space environment, development 

 of the Shuttle has been paralleled by the refinement of 

 many technologies that will have potential uses in other 

 arenas. For example, design of the Shuttle was accom- 

 panied by major advances in hypersonic aerodynamics, 

 thermal protection devices, and very high pressure liquid- 

 fueled engines. In addition, the Shuttle's flight control 

 system, including the use of five identical computers for 

 sensor computational redundancy, is an example of a 

 state-of-the-art computer system offering improved and 

 advanced control technology for many Earth-based ap- 

 plications (NRC-17). 



SOME ANTICIPATED NEEDS FOR THE SYSTEM 



Regular operational flights of the Shuttle are scheduled to 

 begin in late 1982. They will mark the beginning of a new 

 national capability, but not its maturity; additional refine- 

 ments clearly will be needed. Since many of those needed 

 refinements will become evident only as flight experience 

 discloses them, some improvements in the system will 

 have to be planned as the need for them is identified. One 

 improvement already obvious involves the ability to trans- 

 port heavier cargo loads into space. Another is a necessary 

 augmentation in available electrical power both to provide 

 a supply adequate for expected payloads and to increase 

 the Shuttle-Spacelab's stay-time in orbit. Current technol- 

 ogy is sufficient for development of systems that could 

 satisfy expected needs for the next 5 years. However, 

 longer range needs suggest a requirement for increases in 

 the capacity of energy storage devices and improvements 

 in power-management systems (SPACE). 



As mentioned, some future science and applications 

 payloads will require greater stay-times in space than that 

 provided by the augmented Shuttle-Spacelab. Mounting 

 those payloads on unmanned space platforms in low-Earth 

 orbits seems now to be the most efficient method of 

 accommodation. Structures up to a certain size will be 

 carried to space in the Shuttle's cargo bay, but larger 

 structures will have to be transported in sections and/or 

 prefolded and assembled in space. Some structures that 

 may be needed in the future could be large enough to 

 require fabrication in space. Therefore, work has begun in 

 developing both the assembly and the fabricating tech- 

 niques that would be needed and the technologies to be 

 used to maintain the orientation and geometry of the 

 structures (SPACE). 



The period of rotation of any satellite is determined 

 entirely by its distance from Earth's center The rotation 

 period of a satellite located approximately 24,000 miles 

 from the Earth's center is 24 hours — the rotational period 

 of the Earth itself. Since the positions of such satellites 

 remain stationary with respect to Earth's surface, their 

 orbits are referred to as geosynchronous. Communica- 

 tions satellites, for example, benefit greatly from being in 

 geosynchronous orbit, and some remote sensing and 

 space science tasks require that sensors occupy similar 

 orbital positions. As space science and technology pro- 

 gress, the demand for the limited number of geo- 

 synchronous orbit positions is projected to grow rapidly, 

 while the number of such positions obviously will not. 

 Indeed, preemption of geosynchronous positions is an 

 emerging international problem, as noted later in this 

 section. Therefore, consideration currently is being given 

 to collecting a range of payloads on large, unmanned 

 geosynchronous platforms. Those platforms will pose 

 special problems since they may initially have to be serv- 

 iced remotely from great distances (SPACE). 



