This paper investigates different types of reusable first stages designed for a near term application with heavy lift launchers. The attached reference expendable space transportation system is a future Ariane 5 with cryogenic core and upper stage, but skipped solid rocket boosters. The design of the so called liquid fly-back boosters (LFBB) is restricted here to the incorporation of rocket motors already under development or in operation. LOX/RPI and LOX/LH2 combustion in different cycles is looked upon. The analyzed lay-out-variants of the reusable vehicle include attached single as well as dual LFBB-configurations. Catamaran type double fuselage stages are regarded to evaluate the potential in reducing the unsymmetrical thrust load of one side mounted boosters. Beside their primary use to boost heavy lift GTO missions, a second task may be covered by the same vehicle to accelerate the upper stages of small and medium launchers. The additional requirements in designing the same reusable launch vehicle for a least two different missions are studied. The investigation includes trajectory simulations and optimizations for ascent. Return to the launch site by the LFBB is regarded, concerning the propellant requirements and the loads on the vehicle. Different booster geometries are generated by CAD for a preliminary aerodynamic sizing, dimensioning, and mass estimation. Critical flight stability aspects are assessed by static and dynamic simulations. The paper includes a comparison of size and mass, as well as performance data of the different liquid fly-back booster configurations. The relevant rocket engine figures of performance, mass, reusability, and throttling capability are presented.