Here is an example caption used to train the model, you may get similar results of you describe your sci-fi ship using language such as this:
wtf2p5d, space science fiction 2.5D top-down overhead view of a white and grey cruiser with a distinctive bell-shaped forward hull featuring a circular viewport aperture at the apex, symmetrical red accent markings along the fuselage, segmented engine cluster at the rear, rendered in high-fidelity 2.5D isometric game art style with detailed hard-surface paneling and subsurface texture shading, isolated on pure black background
The FLUX.1 [dev] Model is licensed by Black Forest Labs. Inc. under the FLUX.1 [dev] Non-Commercial License. Copyright Black Forest Labs. Inc.
IN NO EVENT SHALL BLACK FOREST LABS, INC. BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH USE OF THIS MODEL.
Styled after a low key space 2.5d game this model is designed to create the base models for stations, ships, asteroid bases, fighters, transports, capital ships, freighters, and frigates stemming from 130 collected images this lora is trained on.