The rumors in Aviation Leak were that (one of the) Arora was an external burn (not RDL) unmanned aircraft around Mach 5-6. The "skyquakes" described here set off the local seismometers at regular intervals (eg 7am monday and wednesday), which doesn't normally happen. By looking at the parabolas (conic shockwave intersection with earth) of the arrival at an array of seismometers one could estimate the angle of the shockwave (Mach) and the angle relative the surface (attack angle). My memory is that it was accelerating Mach 3-5 at an angle over 45 deg.

https://www.defenceaviation.com/sr-91-aurora-aircraft/

Aurora, that's a blast from the past. Donuts-on-a-rope contrails, right?