This is miniature Lancer Cruiser from the RTS game "Conquest Frontier Wars".
I built it in, let's say, an hour or so and would be glad when noboby, who knows the game, feels insulted by now.
Lack in colour and shape are result of my nearly empty bucket of spare parts.
Length: 19 studs (15 cm/6 inch)
Breadth: 10 studs (8 cm/3 inch)
Heigth: 5 cm/2 inch
About this creation
I couldn't find any close-ups of the ship and so had to refer to pictures of battles where Lancers are involved.
At least I learnt something new about it. The main cannon is not set on top of the ball-shaped middle section but in front of it.