These were taken during a rocket motor test when I was working at Thiokol Corporation in Utah. I'm pretty sure, but not absolutely certain anymore, that this was the second stage for the MX missile. If I remember correctly this had one minute of burn time, and I believe space shuttle solid boosters had 2 minutes. These were taken from along the desert highway where a public viewing area was available, anyone could watch these tests but it's a bit of a drive from anywhere. The plant is north of the Great Salt Lake. The large dust cloud remained visible for a long time as it slowly drifted across Plant 78 (another part of the sprawling 19,000 acre or 30 mi2 plant) and dissipated.
There used to be some humorous items floating around the rocket ranch. At that time it was Morton-Thiokol, a division of Morton Salt. And there was a good comic of the Morton Salt girl with her umbrella but holding a missile under her arm. Rather than the salt slogan "when it rains it pours" it said "when it burns it roars". I wish I still had a copy of that!
You can click on any of these thumbnails for a larger version of that photo. I did not create pages for each one for this gallery.