If you read the Skunkworks book, they openly admit Oxcart was tracked by radar. Just as they admit they were fired on by missles (using aforementioned radar for

If you read the Skunkworks book, they openly admit Oxcart was tracked by radar. Just as they admit they were fired on by missles (using aforementioned radar for targeting). They go on to say the missles at the time were unable to reach the speed (mach 3.2) or height of the plane in time to hit it.