Further research tells me that they simply cited the wrong paper from W. W. Mendell, ed.; Lunar Bases and Space Activities of the 21st Century. (Houston, TX, Lunar and Planetary Institute, 1985.) They should have cited Blacic, J. D.; Mechanical Properties of Lunar Materials Under Anhydrous, Hard Vacuum Conditions: Applications of Lunar Glass Structural Components (1985.) Blacic was cited by Rowley & Neudecker, and it was Blacic who made the point about the effect of water contamination on silicate bonding. Blacic even has a figure to help us visualize the problem.
How strong is strong?So does Blacic support Hoagland & Bara's statement that lunar glass would be "approximately twice as strong as steel under the same stress conditions"? No, not at all. In fact, Blacic's Table 1 specifically falsifies the statement.
Here are the key comparisons in that table:
Young's modulus of lunar glass: 100 GPa, cf. alloy steel 224 GPa, terrestrial glass 68 GPa.
Ultimate tensile strength, alloy steel 2.3 GPa. For lunar glass, ultimate tensile strength is dependent on many factors especially temperature. Blacic gives a range of 0.007 - 3.0
Blacic writes (p. 491):
How can lunar glass be utilized? One obvious way is in the form of glass fibers in tensile stress situations. Although lunar glass will be very strong, it will still be a very brittle material, and therefore it makes sense to distribute the load over many small elements. .... lunar glass fibers should always be coated with a metal such as Fe, Al or Mg to protect the glass from inadvertent or purposeful exposure to water vapor. Otherwise, a highly stressed glass component might fail catastrophically due to water-induced stress corrosion.
Summary:: Lunar glass has only half the Young's modulus of steel.
:: If the absolute maximum of the range given for ultimate tensile strength is achieved, lunar glass fibers might be about one-third stronger than steel. At the low end of the range, lunar glass would be about 300x weaker.
:: Using lunar soil in the form of glass does not get you out of the need to mine metals. The metals will be needed for coating.
:: Hoagland & Bara lied.
:: Hoagland & Bara lied, not just in their books, but repeatedly in many radio programs, most recently only 10 days ago.