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Engineering lessons from Apollo, and for the future
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Bill Schweber
Page 1 of 2
EE Times
(07/21/2009 2:20 PM EDT)
With the 40th anniversary of the Apollo moon landing, commentators from all disciplines are offering insights into "what it all meant.".Let's instead stick to results closer to home: What did the Apollo project, and space exploration in general, mean to the engineering community?
The broad lessons I see for engineers and scientists are:
Space design is hard. Every decision, from high-level system architectures down to the components and modules, involves tough, unpleasant tradeoffs in power, performance, reliability, weight, cost, availability, simulation, testability and confidence. There is no free lunch when making a design choice for space vehicles or equipment. Most designs are for a production run of one or several pieces, so it's hard to verify performance. Some elements have to work just one time and then self-destruct (think of explosive bolts) and that's difficult to test with confidence since the actual system cannot be tested (think lunar module ascent engine). Second-, third-, and even fourth-order anomalies and perturbations often have to be considered in the design process.
Space design entails factors which are--excuse the expression--alien to most designers. Factors such a launch acceleration, zero gravity operation, total vacuum environment, extremes of heat and cold, radiation, solar storms and cosmic rays affect components and design. For engineers, the real problem is that "in space, there is no convection cooling." The implications of the space environment are extreme ESD events, static electricity, outgassing of adhesives, lubricants and materials, among others. In some cases, they can be predicted; sometimes, they are predictable, but hard to overcome; in many cases, these situations are unique to space and are not predictable. This means they finally understood the hard way.
Problems and failures are tough to diagnose, repair or work around. Troubleshooting and repair operations have included hands-on replacement of the Hubble Space Telescope's misaligned lens assembly, which took two years to fix. Another example is the sophisticated re-routing of signal paths (via ground-based commands) in a communications satellite to bypass failed modules.
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