When Terrans began expanding into space a conflict began over what service would become the Solar Command. The Marines and Army were not considered and began a longstanding struggle over who was in charge of air defense. The Air Force and Navy both presented strong arguments over who should run the Solar Strategic Command.
The Air force had more experience with space launches, satellites and aeronautics. Then maneuver drives made a lot of that experience worthless. The Navy had experience managing large crews on long missions and operating large vessels. Both built spacecraft and starships. There wasn't a clear winner until the Allen Triphibian.
The Triphibian took an old idea, sticking space drives in submarines for ready made spacecraft. The vessel had ballast tanks and a pressure hull. It could preform as a submarine without the maneuver drive or contra-grav. It was going to explore the oceans of Europa and Titan. Then someone put fuel scoops on it. The first Triphibian refueled at Saturn after a long voyage to several of its moons. The government took notice. Soon proposals for gas giant refueling came out and the second generation triphibs could do just that.
The Triphibian sealed the deal for the Navy to take over the Solar Strategic Command. The similarity of scoop refueling to submersible operations was clear (at least to politicians.) The Air Force became the Orbital Defense Command. Their expertise with probes justified a small exploration fleet and several orbital stations. Having a separate air service when the Army and Marines had begun building grav tanks seemed redundant.
The many of the first settlers on Tyche and the other Fringe Worlds were ODC veterans with a love for tradition. They created the Scout Service to make use of their experience with probes and small crew operations.