Launch Vehicles Then and Now: 50 Years of Evolution
The launch industry has come a long way from the risk-filled early forays into space to the well-orchestrated launches of today—and Aerospace has been there, every step of the way.
Early launch systems were far from reliable, but by 1960, the nation was hurriedly working to send an astronaut into space—along with a host of national security payloads—to overcome the Soviet Union's early lead in space technology. In such an environment, The Aerospace Corporation was founded. Among its core responsibilities was the conversion of ballistic missiles into space launch vehicles. Since that time, the corporation has fulfilled a vital role in supporting Department of Defense (DOD) launches and has also played a significant role in numerous NASA launches. Today, Aerospace is widely recognized for its expertise in launch systems, not to mention its comprehensive archive of historical launch data going back to the earliest launch vehicles.
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Green Propulsion: Trends and Perspectives
Environmentally friendly alternatives could reduce the risk and cost of propulsion systems. Aerospace has been investigating possible candidates for national security space systems.
The propellants used in space programs pose environmental concerns in four main areas: ground-based impacts, atmospheric impacts, space-based impacts, and biological impacts. Ground-based impacts range from groundwater contamination to explosions caused by mishandling of propellants. Atmospheric impacts generally come from the interaction of propellant exhaust with the atmosphere. Space-based impacts generally focus on debris and effects on spacecraft. Biological impacts tend to focus on the toxicology and corrosiveness of propellants.
Discusses the replacement for ammonium perchlorate and hydrazine.
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Space Launch Vehicle Reliability
Launch failures have been a fact of life for most space-faring nations since the space age began in 1957. Because a space mission involving a launch vehicle and a sophisticated satellite can easily cost hundreds of millions of dollars, investigation into why launches fail can provide valuable information for improving vehicle systems and cost savings. Any lessons learned from past experiences that could serve to mitigate launch failures in the future would make such an investigation extremely worthwhile.
A space launch failure is an unsuccessful attempt to place a payload into its intended orbit. This definition includes all catastrophic launch mishaps involving launch vehicle destruction or explosion, significant reduction in payload service life, and extensive effort or substantial cost for mission recovery. It also includes the failure of the upper stage of a launch vehicle, up to and including spacecraft separation on orbit. However, this definition does not include the failure of an upper stage released from the U.S. space shuttle. The U.S. space shuttle is both a launch vehicle and a space vehicle. An upper stage released from the space shuttle in orbit is considered a transfer vehicle, not a launch vehicle.
The space age began with the USSR launch of the first artificial satellite, a liquid-fueled Sputnik (SL-1), on October 4, 1957 (see sidebar,
A Brief History of Rocketry). At present, nine countries or consortia—the United States, the Commonwealth of Independent States (CIS, formerly USSR), the European consortium, China, Japan, India, Israel, Brazil, and North Korea—possess space launch systems, demonstrate space launch capability, or conduct space launch operations.
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Ground Systems Testing
Testing procedures are seldom fully foolproof, but an independent review can help identify and correct potential sources of trouble.
Ground systems testing covers many different aspects of the total ground operations, including areas such as launch facilities, power supplies and generators, fire protection, fluid storage and transfer, air conditioning, payload facilities, fixed and mobile tracking stations, communications, and vehicle transport. These testing operations begin with component testing and end with integration and testing of the complete space system. The goal is to ensure not only that systems function properly, but that they pose no safety hazard for workers in the vicinity.
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Future Directions in Flight Software Assurance
Software accounts for a relatively small fraction of total satellite cost, but as these instances show, it can have a disproportionate effect on mission success. In fact, an Aerospace study of operational failures showed that, in the period from 1998 to 2000, nearly half of all observed space vehicle anomalies were related to software. A rigorous and consistent software assurance approach is clearly needed—but with current systems employing up to a million lines of code, the prospect of verifying and validating system software in a timely fashion poses a significant challenge. As part of its overall focus on mission assurance, Aerospace has embarked upon numerous research efforts to develop new software analysis techniques and to apply the latest developments to critical space programs.
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Space Vehicle Mechanisms
Mission success requires the precise and reliable operation of numerous mechanisms that secure, deploy, move, and release space and launch vehicle components. Aerospace has developed particular expertise geared toward optimizing the design and analysis of these moving mechanical assemblies and mechanisms.
All space vehicles contain mechanisms or moving mechanical assemblies that must move by some combination of sliding, rolling, rotating, or spinning—and their successful operation is usually mission-critical. For example, solar arrays are often stowed for launch to survive the ascent environments and to reduce their envelope, but once in space, they are deployed and must be continually rotated to maximize exposure to the sun. Antennas are sometimes mounted on rotating gimbals to maintain sufficient signal strength. Remote-sensing optical payloads track a scene of interest or examine new targets as the space vehicle orbits. The internal lenses and mirrors of optical sensors are often mounted on adjustable mechanisms to maintain or adjust focus or to reject undesirable signals. Space vehicles must maintain attitude either by spinning or by the use of flywheels or gyroscopes. All of these devices, and many others, depend upon the successful and long-term operation of moving mechanical assemblies.
Unlike many other space vehicle subsystems, moving mechanical assemblies generally are not redundant and therefore represent potential single point failure modes. They therefore require stringent design practices and thorough analysis to ensure proper operation. Aerospace has developed specialized tools for characterizing the motion of rigid and flexible components to verify that mechanisms will perform as intended. In many cases, Aerospace has gone beyond its traditional role in modeling and validation to develop novel practical approaches to prevent mechanism failure.
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What Could Go Wrong? The Effects of Ionizing Radiation on Space Electronics
Space radiation comes in many forms and affects electronic components in diverse ways. Aerospace investigations of how energetic particles interact with integrated circuits and other electronics have been helping spacecraft designers and mission planners minimize the risk of component failure or performance degradation.
The harsh space environment can wreak havoc on unprotected electronics. Over time, exposure to energetic particles can degrade device performance, ultimately leading to component failure. Heavy ions, neutrons, and protons can scatter the atoms in a semiconductor lattice, introducing noise and error sources. Cosmic rays speeding through space can strike microcircuits at sensitive locations, causing immediate upsets known as single-event effects. Passive electronic components and even straightforward wiring and cabling can be seriously affected by radiation. Aerospace has been investigating the means by which heavy ions, protons, and electrons interact with microelectronics. This effort has helped spacecraft designers find ways to prevent serious anomalies on orbit
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Small Satellites: Past, Present, and Future
Chapter 24: The Generation After Next: Satellites as an Assembly of Mass-Producible Functionalized Modules. More
