The video below shows an oxy-hydrogen cannon test we did primarily to assess empirical data derived from a complex oxy-hydrogen cannon equation. We have already decided to use an oxy-hydrogen cannon to deliver small payloads from one moon base to another. The idea of rocket mail first surfaced nearly 80 years ago when Friedrich Schmiedl launched the first rocket mail with 102 pieces of mail on February 2, 1931. Five years later the first successful delivery of mail by a rocket in the United States was made, when two rockets that were launched from the New Jersey shore of Greenwood Lake landed on the New York shore, some 300 metres away. But due to high costs and numerous failed rocket launches, this concept was never deemed a viable option for mail delivery. Things could be different on the Moon. Hardware on the Moon is extremely valuable. Needless to say, two or more moon bases could benefit enormously by sharing equipment or measuring tools. Rock samples etc. could be distributed between isolated bases by oxy-hydrogen cannons as well. If the surface between two moon bases is relatively even, the cannon can be always aligned at an optimal vertical angle of 45° --- due to the lack of air drag and any adverse weather conditions (besides variations in temperature or solar storms) only the amount of oxy-hydrogen in the fuel tank defines the range of fire, which can be precisely controlled, so the optimal amount of explosive is used. The generation of electricity for electrolysis can be done by photovoltaic arrays, water as an electrolyte could be extracted from the top layer of the lunar surface, and the combustion product is just water again. If the extraction of water on the Moon is not possible, it can be carried to the Moon because drinking water is also needed. Besides, carrying explosive fuel mixtures 400,000 km through space is simply too risky.