It is my understanding that the missile launch control centers no longer are equipped with HF.
To the best of the knowledge of those who study OSINT, correct.
As far a subs go, they are generally in the receive only mode. It is rumored, however that the ESTEEM HIGHLY ALFA exercises involve subs calling in after receiving a message telling them to do so "by other means."
Naval and Marine ground and sea assets do not utilize USAF HFGCS, and operate via other nets. U.S. Subs really use everything but. LF, VLF, EHF Milstar, Naval Satcom, and on and on. When there are out going transmissions, which is almost never, it will almost always be via an encrypted data circuit through one of the suspected-dual purpose USN Ranger or Intruder satellite constellations.
In reality though, most messages and orders received via radio are generally acknowledged by USN submarines via their compliance to the order, and not a response. The point is the same as Skyking missions, stealth through silence. Often COMSUBLANT and COMSUBPAC aren't even fully aware of the exact position of their assets, but rather just the operating area. Nuclear Sub commanders are the single most autonomous and responsibility burdened commanders in the armed forces.
