Reply to post: The video doesn't show the full story...

The video doesn't show the full story...

The video starts too late. If you look at other videos, you will see the full chain of events. The test fire for just a few seonds, then stops. The upper and lower tanks vent for about 40 seconds then stop. Nearly a minute later the upper tank starts venting and a couple of seonds later cryogenic fluid suddenly comes pouring out of the bottom of SN4, creating the white cloud around the base (this is where the linked video starts).This happens for nearly 30 seconds before the explosion, and is clearly an massive uncontrolled leak. Shortly after the masive leak, the upper tank starts emergency venting with a second outlet. SN4 doesn't deform or collapse, so I think Scott Manly is incorrect about the weight of the upper tank crushing the lower tank. SN4 is fully intact, and doesn't deform until the explosion shockwave hits it. Looking at varous videos frame by frame, it appears the igntion point of the explosion is external to SN4: for a few frames, the wavefront apears to defom around SN4 (which was fully intact), and only after then SN4 experiences RUD.

My guess is that the lower tank ruptured and an external ignition source triggered the explosion.

Still I'm sure valuable information was found. This is why they do testing.