50 ton jump ship with a 50 ton drop tank they carry through jump. Gives you a jump fighter that when the tank is dropped doubles its acceleration. Of course if someone wants to get rid of you and has it drop the tank in jump space there will be no way to prove it.
Two 50 ton breakaway hulls. Same thing, 1 all fuel, dropped off to be refuelled while the 50 ton main part goes about its business. Jump 5 courier. Could even pickup another fuel hull and jump back while others are collecting the first fuel hull.
A 100 dTon Breakaway Hull; with Jump Drive & fuel in one section, and all the 'mission' equipment in the other might work. Design the drop-able 'Jump' section without a Bridge by using Virtual Crew; all the non-Virtualizable crew ride in the other hull. If you are aiming for 50 dTons exactly, you might be able to get J-4 ...
Here:
TL-15
J-4 drive (for 100 dTon capacity; 2x Decreased fuel); 15 dTons
Fuel for 1x J-4; 31 dTons (requires an additional 5 dTons of fuel from the other hull)
High Efficiency Batteries (Increase Power; Size Reduction; 40 power); 0.55 dTons
Core/40 (Retro; 0.71 MCr at TL-15)
Breakaway Mechanism (the other dTon is in the other hull); 1 dTon
10 Power worth of Fusion Reactor; 0.5 dTons
Reactor Fuel (28 days); 0.14 dTons
M-2 Drive (Sized for a 50 dTon capacity; 3x Energy Efficient, uses 2.5 Power); 1 dTons
Fuel scoop (no tonnage, free with streamlining)
Fuel Purification Plant (15 dTons per day); 0.75 dTons
0.06 dTons of ship supplies
[Edit:] After being dropped in the Destination System, the Jump-hull autonomously scoops fuel; two days, ten hours, thirty six minutes after that the tanks & battery are full, and it is ready to go again.
[Edit of the Edit:] Arrgh! I forgot the stupid % of hull
+5 dTons for the Jump Drive! Back to the drawing board!
[/Edit of the Edit]
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[Edit 3] Realized the problem I ran into above is easily solvable -- require the other hull to supply the last few dTons of fuel[/Edit 3]