Satellites, Future Designs
Satellites, Future Designs
The nature of the satellite manufacturing industry is changing, much as the computer industry changed in the late 1970s. The satellite industry is becoming less of a scientific enterprise, wherein each spacecraft is a unique design, handcrafted and built for a very specific purpose, and more of a commodity business, in which satellites are built around a basic model and adapted to meet the customer's needs. Shopping for a modern communications satellite is more like buying a very expensive piece of industrial machinery than building a new type of airplane.
The Spread of Satellite Technology
Still, building satellites and satellite components is a high-prestige, high-payoff industrial activity. Ambitious nations are willing to spend heavily to create a satellite manufacturing capacity for themselves. Being able to build or launch even relatively unsophisticated spacecraft is a way to assert national pride and show the world that one's country is capable of high-tech development. Argentina, Brazil, China, India, Israel, South Korea, and Taiwan all launched spacecraft in the 1990s at least partly with political and national security goals in mind. In a market in which so many nations are in competition to sell their satellites to a limited number of commercial operators, it is a classic buyers' paradise.
Orbital Sciences Corporation of the United States and Surrey Satellite Technology Limited of Britain have both helped small developing countries to build and fly their own spacecraft. The spread of satellite technology, especially Earth observation systems, is giving even the poorest nations the possibility of using spy satellites to check on their neighbors. India has developed its own series of Earth observation spacecraft, called the India Resource Satellites. Over the years, their spacecraft have gotten better and better at sending down increasingly sharp images so that now they are almost as good as the spy satellites of Western nations.
Newer and Future Commercial Communications Satellites
Nevertheless, the cost of putting a commercially viable communications satellite into geosynchronous orbit (GEO), 35,880 kilometers (22,300 miles) above Earth, is still anywhere from $50 million to $70 million. For the newer and more powerful communications satellites, such as the Boeing Company's 702 model, the cost of getting up there is even higher.
The Boeing 702 model is a good example of an ultramodern communications satellite designed to operate in GEO. It will carry up to 100transponders providing highly reliable communications services at what Boeing hopes will be a competitive price. With its innovative new propulsion system called XIPS, Boeing hopes the 702 will stay up longer, and with less need for complicated and expensive ground control services, than any other communications satellite on the market. The trough-shaped solar wings are a new and highly efficient design intended to act as a concentrator to increase the level of electric power generated by the gallium arsenide solar cells.
In the early twenty-first century, positions for satellites in GEO will become more and more valuable and, probably, will become the subject of expensive and lengthy international litigation. The greater the value, the more profit investors will expect from each spacecraft placed up there. One hundred transponders will not be enough to satisfy the needs of a world that demands ever more communications capability. Commercial telecommunications satellites will soon have to carry hundreds, and eventually thousands, of transponders to meet future demand. Boeing hopes that its future generations of very large commercial satellites will be far more reliable and will remain operational much longer than the current generation, whose reliability problems are well known.
Distributed Spacecraft Systems
One way the satellite industry hopes to solve some of the reliability problems is to build satellites that will fly in formation. This is sometimes referred to as a distributed spacecraft system. The idea is to launch groups of spacecraft that will cooperate to accomplish the desired goal. Whether providing a better multispectral look at Earth's atmosphere, focusing on deep space, or providing less-expensive satellite phone service, future clusters of satellites will have the capability to repair the system by working around a single, broken spacecraft.
Control techniques for these systems will need to be built into each satellite. The satellites will need to be able to communicate automatically among themselves—to autonomously maintain position both within the cluster and in relation to the mission's objectives. An objective could be something as simple as keeping together in orbit or as complex as traveling to Jupiter or Saturn and changing formation when they arrive there.
Old concepts and methods of spacecraft and mission design will simply not work for these future requirements. The satellite cluster, as a whole, must be able to adapt itself to new circumstances without waiting for orders from ground control. This will require new forms of artificial intelligence and a whole new field of software design. There are many difficulties to be overcome before satellite clusters become a reality, but they promise great improvements in reliability and performance.
The most interesting application for a distributed spacecraft design is the Constellation X mission being planned by the National Aeronautics and Space Administration. Its space segment will be composed of a group of X-ray telescopes based around one of the libration points or Lagrangian points. The mission is designed to give scientists a better look at black holes and to push ahead with the effort to unravel the mystery of missing matter .
Other applications of the concept of distributed spacecraft systems include the military's idea for a fleet of radar satellites that would provide real-time data of both ground and air movements as a long-term replacement for the AWACS radar surveillance and the J-Stars ground surveillance aircraft. Another military idea is to build a new class of satellites that can be refueled while in orbit, thus giving them a vastly longer operational life.
Future Space Probes
The need for an inexpensive way to get around the solar system is driving research into "solar sails." This type of spacecraft will be propelled by the solar wind in a manner similar to an ordinary sailboat. It will need huge, lightweight structures to capture the energy of the solar wind. Given the right design, solar sails could be used to place research probes on the far side of the Sun, thus providing us with three-dimensional views of such spectacular events as solar coronal mass ejections .
More conventional deep-space missions will eventually be launched to follow up on the Galileo mission to Jupiter and the Cassini mission to Saturn. In deep space beyond the asteroid belt, solar power arrays do not work. Nuclear power systems, such as the controversial isotope thermal generator used for the Cassini mission, seem to be the only alternative. It had been thought that no more large, expensive deep-space missions would ever be launched again. Now, however, they appear to be the most effective way to reach the outer planets of our solar system.
In the near future, satellites will be even more diverse than they are today. Everything from tiny nanosats, weighing only a few ounces, to very large satellites, weighing hundreds of tons, will be launched into space. Humanity's robotic servants in space will be as diverse, and as ingeniously made, as any of the millions of other tools we have built over the ages.
see also Communications, Future Needs in (volume 4); Lightsails (volume 4); Satellites, Types of (volume 1); Small Satellite Technology (volume 1); Solar Power Systems (volume 4); Space Industries(volume 4).
McCurdy, Howard E. Faster, Better, Cheaper: Low-Cost Innovation in the U.S. Space Program. Baltimore: John Hopkins University Press, 2001.
Sarsfield, Liam. The Cosmos on a Shoestring: Small Spacecraft for Space and Earth Science. Santa Monica, CA: RAND, Critical Technologies Institute, 1998.