I Googled XB-70 Valkryie photos, and this photo was one of them.
The chase plane pictured is a TB-58A trainer. This is the B-58 Hustler bomber, a delta wing bomber that came out in the late fifties, and the chase plane is the trainer version.
The B-58 was a large plane, and the B-70 made it look like a fighter!
If they also made it a space delivery vehicle and replacement for the shuttle, this would be a real hit.