The Postmaster General was completely in the dark about the real reason why the Department of Defense agreed to his proposal. They had no intention of creating a missile delivery system for the mail and thought the idea was impractical from the start. It did offer a very public way to show the improved technology of the U.S. missile program however.
The Regulus I missile was designed to carry a nuclear warhead. So even though the U.S. was currently at peace, the Department of Defense saw the Postmaster General’s request as a way to show the world just how accurate and advanced the guided missile systems of the U.S. military had become. The Regulus I missile was designed to fly up to 600 miles and was meant to be a thinly veiled threat to Russia or any other country that would dare threaten the U.S. during the Cold War.
The Postmaster General was devastated and humiliated when the Department of Defense pulled their support from the project. But even though the test was successful, the Department of Defense saw no way to make missile mail delivery worthwhile. The missile was only able to hold 3,000 pieces of mail and the missile cost $267,000, which meant that it would need to be able to carry much more mail and at a much higher cost to be profitable. In the 1950s, mail was already being delivered by plane, so while missile mail was faster, most people were satisfied with the length of time it took to get mail by plane. There was no demand for mail that could be delivered in a matter of minutes, especially at the price that the Post Office would need to charge to recoup costs.
While many amateurs have tried to deliver personal mail by rocket and handmade missile, there have been no further attempts by the USPS to deliver the mail by missile or rocket.
Regulus I stats
Cost: $267,000
Weight: 13, 685 pounds
Warhead Weight: 3,000 pounds
Length: 32 feet 2 inches
Operational Range: 500 nautical miles
Speed: Subsonic