At 1:03 pm today, the US Air Force launched a robotic space plane that can stay in orbit for over a year. That’s good news for the nation’s troubled space program. The X-37B, as it’s called, is pretty cool — and highly classified. But beyond the veil of secrecy, what’s it really good for? The answer is intriguing but hardly obvious.

First of all, despite some overheated speculation, the Boeing-built X-37B is probably not a space fighter, a space bomber or some kind of satellite-killer to take on the burgeoning Chinese space program. For long-range strikes on ground targets, the Air Force has a much more modest — and affordable — program for a Next-Generation Bomber, basically a souped-up B-2 that won’t even break the speed of sound, let alone reach orbit. And the military has had working anti-satellite weapons since the 1980s: The current satellite-killer is the Standard Missile SM-3, which launches off the Navy’s Aegis ships. You don’t need a robot space plane to do either job.

Second, despite people calling it one, the X-37B isn’t exactly a “space plane,” not in the 1950s sense of the word. True, it has wings, landing gear, and the ability to maneuver; on its two prior flights, the X-37B landed successfully on the runway at Vandenberg Air Force Base in California — which is pretty impressive considering that drones like the Predator have a nasty tendency to crash. But it doesn’t take off like a conventional airplane: It must be boosted into orbit strapped to a big multi-stage rocket. In both respects, the X-37B more resembles the now-retired Space Shuttle — which proved an expensive dead-end for manned space flight. It even looks like the Shuttle’s Mini-Me.

So what does the Air Force do with the X-37B, exactly? It’s almost certainly a spy plane, the 21st century equivalent of the U-2 — or, at least, a testbed for space surveillance gear and a launch platform for miniature spy satellites.

An X-37B flight may be a more expensive way to put cameras, radars, and other “intelligence, surveillance, and reconnaissance” equipment in orbit, compared to a regular spy satellite (and those are plenty expensive). But regular satellites don’t come back down on command so you can check out how well the experimental technology on board performed. And, of course, once you put a satellite in orbit, it stays in that orbit, as predictable in its motions as the phases of the moon –that’s why they’re called “satellites.”

Some spysats have a limited ability to adjust their position, but mostly you can calculate where they’ll be for years in advance. During the Cold War, the Soviets got very good at hiding secret programs when they knew our satellites were overhead and, conversely, trotting out fake stuff that they wanted us to see.

But if you launch an X-37B, the bad guys don’t know where or when it’s going to go. The robot can even adjust its course in space instead of following the same predictable orbit once it’s aloft. As my colleague Colin Clark wrote previously, that maneuverability makes the X-37B militarily flexible in a way even the most advanced spy satellites are not — and it’s got altitude and staying power that no airplane, manned or unmanned, can match.

Today’s launch, just the third X-37 launch ever, is probably just a test run. But in a future conflict, as Colin wrote, an X-37 launch could be the first sign that the military is preparing for a crisis.