Horizon Space Suit Credit - US Army

For sustained operation on the lunar surface Project Horizon advocated a 'body conformation suit' having a substantial outer metal surface.

This was considered a necessity for several reasons: (1) uncertainty that fabrics and elastomers could sustain sufficient pressure differential without unacceptable leakage; (2) meteoroid protection; (3) provision of a highly reflective surface; (4) durability against the abrasive lunar surface; (5) easy cleansing and sterilization. It was noted that while movement and dexterity were severe problems in suit design, the earth weight of the suit could be allowed to be relatively substantial. For example, if a man and his lunar suit weigh 120 kg on earth, they would only weigh 20 kg on the moon.