Decision-Making in Context: Conservation of Gold and Magnesium Alloy Components on a Surveyor Spacecraft

Jacqueline Riddle, Elizabeth Beesley, Lisa Young, and Malcolm Collum


In preparation for the first lunar landing, NASA created the Surveyor Program which sent seven robotic spacecraft to the Moon between June 1966 and January 1968. These spacecraft provided crucial information to the Apollo 11 mission which put the first humans on the Moon in July 1969. The Smithsonian acquired a full-scale engineering model of a Surveyor spacecraft in 1968, and it has been on continuous display since then. Amongst other components, the spacecraft has a mechanical scoop, designed to dig trenches in the lunar soil, a TV camera, designed to send live video feed back to Earth, and an alpha-scattering surface analyzer, designed to conduct the first elemental analyses of the lunar soil. The alpha-scattering instrument is housed in a gold-plated copper box secured to a magnesium alloy base. Extensive magnesium corrosion was discovered on the base and subsequently treated in 2013, when the instrument was temporarily removed due to damage caused by a leaking pipe. In 2017, the entire spacecraft was removed from display in preparation for the upcoming renovation of the Smithsonian National Air and Space Museum. For the first time in almost 50 years, conservators were able to conduct a thorough examination, technical analysis and treatment of the spacecraft. This included analysis using X-ray fluorescence spectrometry (XRF) and Fourier-transform infrared spectroscopy (FTIR), extensive cleaning and iron stain reduction, consolidation of paint and plastics, in-painting, and corrosion mitigation. The 2017 examination revealed that the magnesium treatment performed in 2013 was ineffective. Galvanic corrosion had further developed between the magnesium base and the gold-plated component, indicating that the initial treatment strategies would not be sufficient for its long-term display. Conservators walk an ethical tight rope where several factors are balanced: the principle of reversibility countered with the challenges of preserving fugitive materials, the principle of minimal intervention with the need for an enduring treatment solution. The presence of unusual modern materials with no established conservation treatment methodologies adds a layer of uncertainty in the decision-making process. In the conservation of large technological artifacts, treatment frequently requires complete or partial disassembly of the artifact. At the Smithsonian National Air and Space Museum, large artifacts are often suspended from the ceiling for long-term display, where they remain practically inaccessible for years. When suspending artifacts above the public, conservation treatments—particularly to structural components—cannot fail. All of these factors can drive treatment decisions towards more restorative techniques. This paper will present the decision-making process and ultimate outcome of the conservation treatment on the Surveyor spacecraft. It will focus on the treatment of the alpha-scattering surface analyzer, which contained persistent corrosion of magnesium alloy parts in contact with gold-plated components. Tactics for treating galvanic corrosion, as well as new tools and techniques adapted from the aerospace industry will be presented.

2019 | Uncasville | Volume 26