This New York Times piece still leaves us guessing about the mission of the X-37B space plane, which the U.S. Air Force launched in April from Cape Canaveral, Fla., aboard an Atlas 5 rocket under a veil of secrecy. Amateur skywatchers tracking the X-37B’s orbit suspect that since it passes over the same spot on the ground every four days, and over some of the world’s hotspots, it likely is a prototype reusable surveillance spacecraft.

Perhaps, but it is difficult to see an economic or operational case for a reusable surveillance spacecraft the size of the X-37B, which is designed to orbit for up to nine months before re-entering the atmosphere and gliding to an aircraft-like landing. In the first place, Atlas 5 and Delta 4 rockets are expensive — typically costing in the neighborhood of $160 million — which seems like a lot for short-duration missions. Moreover building one of these rockets is about a two-year process, and the Air Force typically doesn’t keep spare rockets lying around in the shed. That means if the service is to have a responsive and reconfigurable surveillance capability based on the X-37B it is going to have to dramatically change the way it buys and operates its launchers.