The fifth launch of the X-37B robot spaceplane almost makes this vehicle look routine. This time, liftoff has come with a Falcon 9 rocket from SpaceX instead of an Atlas V, a change from old-school launchers to NewSpace.
By itself, this was controversial, but the spacecraft is in orbit as requested. Security for this launch seems to have been just as tight as for previous launches, with no leaks of information. That's another point in favour of the vehicle's new launch provider.
The US Air Force has also given notice of additional payloads on this mission. In practice, that means small satellites riding under the same payload fairing as the spaceplane, but almost certainly not inside it.
The payload bay isn't really suitable for this. Apart from the deployable solar panel and antennas, we can probably say that nothing else will pop out of this spacecraft. Anything that is deployed will be taken back inside before the spacecraft returns to Earth.
Exactly when that return happens is a mystery, as for every previous flight. But we probably won't see the end of this mission for at least a year, and probably much longer than that. Every subsequent flight of X-37B lasts longer than its predecessor, but at some stage, we can probably expect mission endurance to level off.
That time is probably approaching. Even if this mission proves to be another record breaker, the sixth flight probably won't outstrip it. The last flight lasted 718 days. Even if the fifth goes longer, it will probably only do so by a few months. Somehow, the idea of breaking the two-year barrier sounds tempting.
There's another trend that now seems to be entrenched in the X-37B program. It's getting camera-shy before launch. Neither SpaceX nor the US Air Force released photography of the spacecraft before its latest mission.
We saw some nice images of X-37B encapsulated in its payload fairing, but no peeking inside. That happened for the last mission too, breaking a previous trend. Excellent pre-flight photography was released for the first three missions.
This analyst ventured theories to explain this in the past. Some theories of modifications to the X-37B itself were nullified when nice images of the spacecraft were released from its descent and landing phase.
Nothing really seemed different. But as with the previous flight, we have been told that other payloads are riding with the vehicle. Some of the payloads that rode piggyback with the last launch were openly identified, but there could have been others that we don't know about. This trend seems to be continuing.
So it seems plausible that we are not meant to see these special payloads. Photography of the spacecraft being encapsulated for launch would presumably reveal these other payloads, clinging to the adaptor just beneath the X-37B itself.
We may therefore ask if these payloads are meant to interact with the X-37B itself in orbit, possibly flying in formation as calibration targets for sensors. Seeing the target would give clues to the sensors used to observe them. But the Air Force generally doesn't like to talk much about what lies inside the clamshell doors of the spacecraft's payload bay.
Sensors of some covert nature are probably on board, but the Air Force has also disclosed one experiment inside. A thermal control system that uses heat pipe technology to cool electronics is being conducted. This sounds highly plausible, and consistent with the X-37B's role of testing vital organs for future USAF satellites.
Prior to launch, the USAF also disclosed that a higher inclination orbit would be used for this mission. This would expose more of the Earth's surface to the vehicle. Again, this is another clue that some sort of sensor is being tested. It could also cause the vehicle to pass within range of tracking stations (radio or optical) that are interacting with specific payloads on board.
A USAF officer connected to the program stated that "many firsts" will be conducted on the mission in the official media release. Some of these "firsts" have been documented in this article. We wonder how many other new developments will take place without public disclosure.