As Terrans pushed forward and took systems off the Imperium it became necessary to defend those systems. The Terrans didn't have the assets to tie up expensive battleships defending systems behind the front line. So they looked at what they had and what had worked before.
The System Defence Boat strategy had worked in the Terran system. Relatively small and fast agile craft that could "hide" in gas giants or deep space and harry the enemy. They were also cheaper and more combat effective than equivalent sized jump-capable ships. Against a similar sized Imperial Patrol Cruiser they rarely lost. The basic concept worked well.
The only problem was that without jump drives they couldn't easily be moved between systems to where they were needed. They also realised that a fixed garrison of SDBs was wasteful of scarce resources. The Terrans required flexibility and optimal usage of their limited fleet assets if they were to stand any chance at all against the ship building might of the Imperium. The concept of the jump-tender was born.
An SDB jump-tender could carry an SDB to where it needed to go, and then return and get another one, and another. It wasn't as fast at deployment as having jump capable combat ships, but it was a lot cheaper and an acceptable compromise for second line defence.
As a totally new design the jump-tender project was beset by a string of apparently insurmountable engineering issues. Then the prototype was lost with all hands during shake down trials. After detailed investigation and further redesign a workable model emerged though issues still remain.
Fitting in just the essential components: the jump drive, the fuel tank, the space drive and the reactor was a major design challenge. It was a challenge that the Imperials could not have met with their all encompassing "standard" that dictated everything from minimum acceleration to minimum accommodation standards. Coming up with a design that compromised on almost everything was a literally alien concept to the Vilani. The end result was a military craft that could do only half a gee acceleration when loaded and had the barest minimum accommodation.
Conditions on board are spartan with just the two command officers having staterooms, and sometimes even they had to double up. The other six crew members and any rotation crew carried for the SDBs must share a single ten person bunkroom. The sickbay was often called into service as an additional stateroom for other command officers when in jump. The relatively small cargo hold was often overflowing with spares and equipment to service the SDBs putting an even greater strain on accommodation.
Both the SDB and the jump-tender are vulnerable when they are attached as the tender can only manage 0.5 G in this configuration. They are also vulnerable during the lengthy attaching and detaching process. Emergency detaching usually disables the tender and damages the SDB. Also due to the differences in streamlining between the SDB and the tender it isn't risk-free to skim for fuel while attached to an SDB so this is only done in emergencies.
Partly to make up for their shortcomings and vulnerabilities, Bearer-class tenders are as heavily armored as the SDBs they carry and have a defensive turret. They also have a reasonable 2.5 G acceleration when detached from an SDB. So despite their issues they have good battle survivability and are generally well liked by their crews.
Bearer-class jump-tenders are named after unsung heroes of the past. People who may not have been the headline maker but were there all the same, supporting or providing valuable assistance.
Hull: 200-ton Close Structure Streamlined Hull, dDR 150 armor, Stealth
Systems: 17 Maneuver Drive, 18 Jump Drive, 120 Fuel Tank, 2 Fuel Processors (18.8 hours to fill tank), Standard Bridge, Model-1 Sensors (Scan 16), 19.5 Fusion Power (390 MW), 1 Bunkroom (10 bunks), 2 Staterooms, 5.5 Cargo, 1 Workshop, 1 Sickbay, 1 Light Turret (2 Beam Lasers, 1 Sandcaster)
Statistics: Emass 1350, Lmass 6800, Cost M$ 180, SM 8, ASig 2, Hull dHP 55, Life Support 14, sAccel 0.5 G (2.5 G detached), Jump-2 (2 parsec range with SDB, 6 parsec range without), Top Air Speed 740 mph
Crew 8: 4 Command, 2 Engineers, Gunner, Medic