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Environmental Testing for Launch and Space Vehicles
Space systems must endure a physically stressful journey from the launchpad to their final destinations. Adequate testing can help ensure they survive the trip.
The structural design of space systems is dictated by the rigors of the liftoff and ascent environments during launch as well as the extreme thermal conditions and operational requirements of spacecraft equipment and payloads on orbit. At liftoff and for the next several seconds, the intense sound generated by the propulsion system exerts significant acoustic pressure on the entire vehicle. This pressure induces vibration, externally and internally, in the space vehicle structures. In addition, the vehicle experiences intense vibrations generated by engine ignitions, steady-state operation, and engine shutdowns as well as sudden transients or "shocks" generated by solid rocket motor jettison, separation of stages and fairings, and on-orbit deployments of solar arrays and payloads. Space vehicles will also experience wide fluctuations in temperature from the time they leave the launchpad to the time they settle into orbit. Both individually and in combination, the mechanical environments of pressure, vibration, shock, and thermal gradients impose design requirements on many structural components. Ensuring the survivability of the delicate hardware poses challenges that can be met only by extensive preflight tests encompassing acoustic, shock, vibration, and thermal environments.
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- Rockets and the Ozone Layer
Rocket engine exhaust contains chemical compounds that react with ozone in the stratosphere. A new measurement program suggests that current space transportation activities only minimally affect Earth's protective ozone layer.Protecting Earth's ozone layer remains an important environmental issue. Without this shielding layer, ultraviolet (UV) radiation would harm life on Earth. We hear alarming statistics on increasing incidences of skin cancer and other disorders that may be linked to a thinning of Earth's ozone layer. We know that the presence of chlorofluorocarbons (CFC)—chemicals used as solvents and refrigerants—and other industrial gases in the atmosphere is the major cause of ozone depletion. But what about exhaust from launch vehicles? Can the cumulative effect of emissions from rockets launched every three or four days from various launch sites around the globe significantly alter Earth's delicately balanced, natural sunscreen? More ...
Launch Vehicle Propulsion
Rocket engines have evolved over the course of several decades. Research at Aerospace has helped make valuable improvements in performance, cost, and reliability.
In 1920, The New York Times responded to a scientific paper in which Robert Goddard, the father of modern rocketry, discussed the possibility of sending a rocket to the moon. The Times editorial stated that Goddard's ideas were all wrong and that rockets could not reach the moon because there was "nothing for a rocket to push against in outer space." Of course, Goddard was correct, and in 1969, just after the launch of the Apollo 11 moon mission and 24 years after Goddard's death, the Times issued a belated retraction.
The technology underlying the propulsion systems that power today's rockets is being pushed to new limits. The analytical tools that Aerospace and contractors use to design and analyze engines have made significant improvements in speed and fidelity, but the hardware itself has evolved slowly compared with that of other high-tech industries. Characterized by extreme power density (enough pumping power to empty a swimming pool in 25 seconds) and severe temperature gradients (up to 3600 Kelvin), propulsion systems are understandably difficult to design with high reliability. Challenges have included reducing propulsion system mass to allow more room for payload, pushing propellant combustion performance closer to the theoretical maximum, and increasing reliability to make launch vehicles as dependable as aircraft. The future holds promise in these areas, but to appreciate the changes taking place, one must first be familiar with the basic physics of rocket propulsion. More ...
The Launch Verification Process
An impartial and comprehensive system review verifies the flightworthiness of a launch vehicle and instills confidence in ultimate mission success.
The process used to independently determine launch system flight readiness is a capability unique to The Aerospace Corporation that has been employed for more than 40 years. It is based on a comprehensive technical assessment that is thorough in its attention to detail with total system coverage.The Aerospace approach to launch-readiness verification is unparalleled in its breadth and depth. This comprehensive, end-to-end process extends from concept and requirements definition through flight operations: It entails the detailed scrutiny of hundreds, if not thousands, of components, procedures, and test reports; it draws upon independently derived system and subsystem models to objectively validate contractor data; it provides timely review through firsthand involvement in all aspects of the launch campaign; and it concludes with a thorough postflight assessment using independent analytical tools and independently acquired telemetry data to generate useful feedback and monitor performance trends. More ...
Launch Vehicle Guidance, Navigation, and Control
Getting a rocket safely from pad to orbit requires sophisticated, responsive flight software. Aerospace helps ensure that these mission-critical systems are fully qualified for the job.
A rocket's flight software (part of the avionics suite) has the difficult job of directing and controlling the vehicle from its initial position bolted down to the ground to its target location far above Earth. In modern rocketry, this is performed autonomously. To accomplish this challenging task, the flight software must correctly perform three basic functions: guidance, navigation, and control (GNC). Navigation is the process of determining the vehicle's position, velocity, and attitude in space. Guidance is the process of deciding how to steer to the desired target. Control is the process of implementing the guidance commands to achieve actual engine deflections or changes in thrust vector. More ...
