With the recent .25 update, the R.A.P.I.E.R. engine received a decrease in it's dry weight; going from 1.7 to 1.2 tons. This allowed for the more effective use of the engine, forming the creation of the B-25 SSTO family. This group of SSTOs were built to replace existing Goliath Aerospace shuttle designs with smaller, simpler alternatives.
B-25 Type A
Personally my favorite of the three, the type A has an inline Mk2 docking port, and is meant for the comfortable transportation of two pilots. This variant has the best in-flight performance, especially for newer SSTO pilots. The type A can reach a 100km periapsis orbit and still have enough fuel to de-orbit and land.
B-25 Type B
The first out of the three built, this version can bring a small satellite to a 100km orbit, using the new cargo bays. The reason for this is to establish an objective for beginner pilots; fly into space, establish orbit, release the satellite, and land safely.The type B can also reach a 100km periapsis orbit and still have enough fuel to de-orbit and land.
B-25 Type C
longer range version of the B-25. An extra(emptied) fuel tank and front-facing docking port allows for more refueling and the ability to attach space tugs, respectively. It is important to place all remaining fuel in the most frontward tanks when re-entering.