Northrop, Boeing, Lockheed.
Amusingly enough, they're both working with Orbital ATK.
If the NGL can overcome these challenges, it will still be an unorthodox design. No other launch vehicle has ever used two solid stages topped with a liquid hydrogen/liquid oxygen upper stage. But, for Orbital ATK, this design makes sense as it draws on their decades of experience and utilizes facilities they already have. This unique architecture could actually be seen as an advantage by the US military, whose doctrine of “assured access to space” depends on having several independent means of launching satellites into space. SpaceX will use only SpaceX hardware on their Falcon rockets. ULA, as a traditional contractor, will integrate Blue Origin’s rocket engines on their new Vulcan rocket. If Orbital ATK uses their own solid-propellant motors and an RL10-powered upper stage, that would be a technologically independent means of launching national security payloads. While the NGL is unorthodox, its unconventional nature may actually prove to be its greatest asset.
Their current principal launch vehicle, the Minotaur, is the WMD formerly known as the MX Missile.
400 missiles, 90 billion dollars. that's about 2500 Falcon 9 launches.