Russia has proclaimed the Kinzhal as a breakthrough mach 10 hypersonic missile. ICBM rockets have long been able to go to Mach 20. The reason that hypersonic missiles and hypersonic planes have been a military development goal is that they could be far more maneuverable than ballistic missiles.
The Kinzhal is a shortcut hypersonic munition that while fast enough to evade enemy defenses, also lacks the maneuverability to accurately strike targets at long range.
Babak Taghvaee, an expert on Russian warplanes, claimed in a tweet that just six MiG-31s have received the modifications necessary to carry the approximately 25-foot-long Kinzhal. Another four to six MiGs could be modified by the end of 2018.
By the end of 2018, #RuAF #Russia|n Air Force will form an Aviation Squadron with 10-12 MiG-31BMs especially modified for carrying the Dragger Hypersonic Missile in one of its Fighter Regiments. For now six MiG-31BMs are modified to carry the missile. They are now in Akhtubinsk. https://t.co/KKsex2FCKj
— Babak Taghvaee (@BabakTaghvaee) March 11, 2018
The Kinzhal does not appear to have a hypersonic engine. Hypersonic engines start working at about mach 5. For a reusable hypersonic vehicle you would need a triple engine. Turbines to get up to mach 3 and ramjets mach 4-5 and then scramjets at mach 5+. Rockets can go all the way to mach 40+. Mach 33 is orbital velocity for earth.
TBCC, or Turbine Based Combined Cycle propulsion system, is a turbine engine combined with a ramjet and scramjet.
The Pegasus was and is 55 feet long and Pegasus XL is 58 feet long.
Pegasus first flew in 1990 and remains active as of 2017. The vehicle consists of three solid propellant stages and an optional monopropellant fourth stage. Pegasus is released from its carrier aircraft at approximately 40,000 ft (12,000 m), and its first stage has wing and a tail to provide lift and attitude control while in the atmosphere