Moreover, hypersonic gliders are actually at a speed disadvantage compared with ballistic missiles of the same range. Ballistic missiles are also boosted to high speed by large rockets, before arcing through the vacuum of space. A glider, by contrast, spends most of its trajectory in the atmosphere, using aerodynamic lift to extend its range. The increased range comes at the cost of faster deceleration caused by atmospheric friction. One implication of this reduced speed is that hypersonic gliders may be more vulnerable to interception by U.S. “point” missile defenses (especially after such defenses have been optimized for that purpose). Like cornerbacks in football, point missile defenses are intended to protect small but important areas — such as U.S. military bases in the western Pacific.
Here is the full piece by James Acton.