Hi. I had the same dilemma with my current webcomic. I had never drawn a spaceship before and my comic is a spaceship battle comic.My advice is to practice drawing as much as possible beforehand and to try a bunch of different designs before settling on a design. And maybe try to make them in Sketchup as someone mentioned. I end up just drawing mine by hand (digitally) every time, but it's difficult to get them looking consistent between panels.
As others have said, you definitely should have some backgrounds and it is something that does unfortunately come with the territory. If you use a program like Clip Studio Paint, it is much easier to make a background than doing it by hand with pen and ink since it draws a line in perspective every time so you can ink as quickly as anything else.
I think a general rule of thumb, at least for manga style comics, is an average of 1-2 backgrounds per page. But some pages might be just dramatic close ups and some pages might require more backgrounds so the amount of backgrounds will vary.
Also, readers LOVE backgrounds. Striking characters, poses, and expressions are nice, but readers will also be wow'd if you have a really nice, detailed background once in a while.