When I see the SpaceX reentry videos I see no flaming ionization from the time the reentry starts. I realize things must be getting hot at some point but its not the ball of fire I imagined . Where should I be seeing this or its probably not as I imagined. Anybody got any observations.
Assuming you are referring to videos that end with a landing, you are only seeing the first stage. Even without the boostback burn it is relatively slow - less than 2 km/s.
The second stage gets up to actual orbital speeds, around 7 km/s, and that does turn into a fireball on reentry.
Quentin Clarkson's answer is correct; the first stage doesn't get fast enough to create a dramatic reentry fireball.
However, if you look at this video -- sped-up footage from the top of the first stage, looking down -- you can see at around 0:15-0:20 that the grid fins are getting charred from the heat of reentry.
In the real-time feed in a different video, the first reentry burn occurs at 7:00 to 7:19 or so. After the reentry burn shutdown call the fins are a light gray with soot. At 7:26 there's a glint on the fin at the left of the frame -- possibly burning paint. Around 7:30 the frame is starting to gray out, with black flecks hitting the camera, while the engines are not firing. 7:35 is completely grayed out. We're still far above clouds, and around 7:40 the realtime downlink is lost, I assume because of vibration. It's another full minute before the first stage landing burn.
Comparing that sequence of events to the (uninterrupted) high-speed video you can see the burn from 0:13-0:14, light gray grid fins, then the gray-out from 0:15-0:16, and blackened grid fins at 0:18 shortly after the live feed dropped out. Something blackened them and it wasn't a main engine burn!
They do three burns.
- Boostback burn to cancel forward velocity (for ASDS landings) or to head back to the Cape to land at LZ-1/LC-1.
- Re-entry burn to control the speed and interface with the atmosphere.
- Landing burn.
The Boostback burn is too high usually to have much atmospheric effects.
The Re-Entry burn is the one you would likely see it, but it seems they control the speed sufficient to avoid it.