In article .com,
says...

Quite a lot of sources name the Valkyrie as an extremely high lift
over drag efficient aircraft. According to Wikipedia:

"This gave the Valkyrie the best lift:drag ratio of any powered manned
aircraft ever built and allowed a much better aspect ratio on take-off
and landing. Some recent SST designs are considering this as an
option."

Anyone knows l/dmax of the XB-70? Commercial airliners are around 1:18
while motorgliders (and the U2) come close to 1:30 An L/D of 1:30
seems impossible for an aircraft like the Valkyrie?

Good question I have some B-70 data somewhere around from when I worked at NASA
Lewis (now Glenn) on the B-70 project. I worked in the 10'X10' wind tunnel and
we had the B-70 model in for inlet studies. North American had a nice booklet
they passed out that had a lot of neat pics and background on the plane.

Chuck S