Reddit reviews Space Wars: Worlds & Weapons

This illustration appears on page 50 of Steven Eisler's Space Wars Worlds & Weapons (my edition is the 1980 Octopus Books UK reprint). As others have already noted, it credits this picture to Micheal Whelan, and says its title is "Armageddon". I'm pretty confident the image you found is scanned from the book, because the original is actually square, and the book spans it over 2 pages, with the rightmost 15% or so on the right page (missing from the image you've found).

You can get a used copy of the book very cheaply:
http://www.amazon.com/Space-Wars-Weapons-Steven-Eisler/dp/0517273446/

It's a weird book - the text of the book is a factual history of science fiction. It's illustrated with a wide collection of SF artworks, from the usual crew of SF artists that you've seen illustrate every pulpy SF novel ever). But the captions for each picture don't actually describe the picture - they are themselves a single coherent(ish) fictional universe, and pretend that the thing illustrated is part of that universe. Which gets weird when you encounter the same pictures (by e.g. Chris Foss) on the cover of some totally unrelated novel.

The image was also used in the book Space Wars, Worlds, and Weapons by Steven Eisler.