Tuesday, January 10, 2012

Literature of your Interest


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  •  Finding Flaws Without Causing More: The Art and Science of Nondestructive Evaluation
    A mixture of insight and innovation helps detect hidden defects in space system components, safely and reliably.


    The launch process is severely taxing for the countless components and assemblies found aboard spacecraft and launch vehicles, and space is a difficult environment for many materials. Invisible flaws, such as impact damage or a partially bonded joint, can lead to expensive failures during launch or on orbit, where components generally can't be fixed. Detection of flaws is therefore essential. Moreover, flaws need to be discovered in a nondestructive manner—that is, the process used to test for them must not damage the potentially unflawed component being tested. More ...
  • Electric Thruster Test and Evaluation
    Evaluation in ground test facilities plays a critical role in the development and qualification of new thruster systems.
    Spacecraft electric thrusters are responsible for the critical functions of orbit transfer, on-orbit station keeping, and, in recent applications, interplanetary propulsion. Electric systems generate thrust by using electric and magnetic processes to heat and/or accelerate a propellant or plasma. Chemical systems create thrust through chemical reactions that generate expansive exhaust. Electric thrusters have an exhaust velocity normally 2 to 10 times higher than chemical thrusters, which means their efficiency with respect to propellant usage is greater. Payloads can therefore be augmented or launched on smaller, cheaper vehicles.
    On the other hand, the testing and evaluation of electric thrusters is more challenging than for chemical systems. The amount of energy per expelled particle, the overall complexity, and the required lifetime is typically much greater. In addition, the considerable potential for sputtered particle deposition, energetic ion impingement, electromagnetic interference, and other interactions that could adversely affect the spacecraft and its subsystems must be addressed. The potential for adverse interaction tends to increase along with electrical power input and propellant flow rate, which have risen as available onboard power has increased. More ...

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