The larger parts on either end are primarily just heavy armor.
They move along their length. Typically the end with the larger bulb is the front I believe, but many ships have equally sized bulbs.
Propulsion is provided by gravity generators built in a ring encircling either end of the craft.
In normal space the ship forms two planes of intense gravitational gradient above and below the ship in a wedge shape, which has the effect of moving the ship forward. For reasons that I suspect have some grounding in actual physics (?) The wedges need to be open at either end to actually move the ship forward.
The two planes have such intense gravity that literally nothing (including missles, lasers, visible light, etc.) can get through. The sides of the ship can be protected with weaker "side wall" gravitational planes, but not at the strength of the primary planes or it will interfer with propulsion.
All of this has the effect of making space battles similar to ocean battles with broadsides of missiles (which can get through the side walls) and lots of emphasis on maneuvering to bring your ship's broadside in line with the other ships unprotected "throat" or "kilt".
Which brings it right back to the bulbs on either end which are the heaviest armored parts of the ship because they are not protected by powerful gravitational planes.
Civilian ships taper at the ends instead of flaring since they don't need the armor or powerful sensors that military craft put there.
(As an aside, the honorverse hyperspace has currents of gravity. When in hyperspace the gravity generators on a ship create Warshawski Sails - massive km wide planes of gravity which catch the currents to move the ship much faster than possible in normal space.)
They move along their length. Typically the end with the larger bulb is the front I believe, but many ships have equally sized bulbs.
Propulsion is provided by gravity generators built in a ring encircling either end of the craft.
In normal space the ship forms two planes of intense gravitational gradient above and below the ship in a wedge shape, which has the effect of moving the ship forward. For reasons that I suspect have some grounding in actual physics (?) The wedges need to be open at either end to actually move the ship forward.
The two planes have such intense gravity that literally nothing (including missles, lasers, visible light, etc.) can get through. The sides of the ship can be protected with weaker "side wall" gravitational planes, but not at the strength of the primary planes or it will interfer with propulsion.
All of this has the effect of making space battles similar to ocean battles with broadsides of missiles (which can get through the side walls) and lots of emphasis on maneuvering to bring your ship's broadside in line with the other ships unprotected "throat" or "kilt".
Which brings it right back to the bulbs on either end which are the heaviest armored parts of the ship because they are not protected by powerful gravitational planes.
Civilian ships taper at the ends instead of flaring since they don't need the armor or powerful sensors that military craft put there.
(As an aside, the honorverse hyperspace has currents of gravity. When in hyperspace the gravity generators on a ship create Warshawski Sails - massive km wide planes of gravity which catch the currents to move the ship much faster than possible in normal space.)