This statement is factually wrong.
Booster is
not "in the final stage" (your quote).
The boost phase is primarily before first stage separation where mid course correction starts.
Total KE of a hypersonic weapon does not only come from first stage engine. It comes from Burnout Velocity
+ KE gathered in Skip/Steady or Skip+Steady trajectory which is why the vehicle is called "glide".
View attachment 936252
Fattah's Total KE comes from three sources
1) A very high Burnout V of 13-15 Mach from Depressed boost phase
(previously seens in Zolfaghar AShBM, Khyber Shikan Skip-GV, Qassem)
2) Skips, Glides to gain more KE
(Previously
Khyber Shikan Skip-GV, Qassem)
3) Powered RV (TVC-MaRV)
(used in almost all Space Launching Vehicles SLVs of Iran, IRBMs Sejjil II/III, K-2/4, AShBM of IRGC)
That results in a terminal V of 8 Mach which qualifies for hypersonic classification.
P.S. Also
provide evidence in form of Specific Impulse (Isp) that "first stage engine is not powerful enough to give enough kinetic energy" (Your direct qoute).
You need to read before you post. Iran has been testing+inducting missiles with MaRVs/TVC-RVs for 15+ years now. Every single missile of Iran is a separating RV with:
1) Endoatmospheric corrections through Control surfaces + TVC + Lateral Gas thrusters for CEP less than 10m.
2) Exoatmospheric corrections through Gas thrusters and vanes for mid-course corrections
Fattah is equipped with both for extreme level accuracy if required. without lateral correction it will gain even more speed (without glide, with a burnout V of 15 Mach, it will reach borderline IRBM ranges).
Here are some examples of Iranian control mechanism for missiles.
Gas thrusters of Khorramshahr-4 IRBM
View attachment 936258
Exo+Endo TVC + Control surfaces MaRV of Ghadr MRBM (Labelling Credit @Patarames)
View attachment 936261
Separating MaRV with control surfaces of Khyber Shikan (predecessor to Fattah, was a Skip glide vehicle perhaps)
View attachment 936249
View attachment 936248
This is a 15 year old Entire Solid-Staged IRBM of Iran called Sejjil II/III. Even this has a separating MaRV for low CEP.
View attachment 936253
It means nothing in the case of Fattah because it's a separating MaRV system, the booster stage separates much before. I think you do not know that modern missiles have to separate RVs.
There is no law that says to be hypersonic, the RV should have no lateral maneuverability. MaRV can go hypersonic too for accuracy (Lateral acceleration) and KE (Linear acceleration).
You are getting into the same cycle of confusion that one indian member was in earlier in this thread. Hypersonic weapons have less to do with the shapes of RV. It has more to do with
1) Hypersonic speed in the terminal phase (Fattah 8 mach)
2) Skip+Steady glide (Fattah does that)
American Hypersonic RV
Iranian Hypersonic RV