what's the speeds of MaRV during re-entry and impact/blast ?
During the terminal phase:
Chinese DF-15 SRBM has a terminal speed of Mach 6 (see citation below).
Chinese DF-21D IRBM has a terminal speed of Mach 10.
Chinese DF-5/DF-31/DF-31A ICBM has a terminal speed of Mach 23.
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Indian missile defense won't work against hypersonic Chinese ballistic missiles
Shooting down a Prithvi SRBM
It depends on whether the interceptor shot down a Prithvi I/II or a Prithvi III SRBM.
A Prithvi I SRBM has a range of 150km. A Prithvi II has a range of 250km.
For an interceptor to shoot down a Prithvi I, it's really not that hard. A Prithvi I is liquid fueled, which should have a lower energy density than a solid-fueled missile. Also, given the limited range of 150km, the incoming warhead will have a very slow speed.
Shooting down a Prithvi II is better performance. Given the greater 250-350km range of a Prithvi II, the incoming warhead should travel a little faster than a Prithvi I.
Since a Prithvi III is solid-fueled and has the greatest range at 350-600km range. Shooting down a Prithvi III warhead would be the best performance, because the warhead should be traveling faster than a Prithvi I or II.
However, in the end, the interceptor only shot down a SRBM.
I would have to research the answer, but a SRBM warhead moves pretty slowly. It's nice for India to develop a defense against a SRBM.
I know a Chinese DF-21D ASBM travels at Mach 10. As far as I know, the United States has no reliable defense against an incoming IRBM warhead.
An ICBM warhead travels at Mach 23. No known conventional technology can intercept an incoming ICBM MARV. You might get lucky with a Nike Hercules-type nuclear interceptor, but then you'll become blind to the follow-up nuclear strike.
In conclusion, an interceptor against a SRBM is a nice beginning. To become truly useful, the technology must be extended and shown to reliably intercept Mach 10 IRBMs and Mach 23 ICBMs.
References:
Prithvi (missile) - Wikipedia, the free encyclopedia
LGM-30 Minuteman III ICBM - United States Nuclear Forces
"
Speed: Approximately 15,000 mph (Mach 23 or 24,000 kph) at burnout"
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Indian AAD/Prithvi interceptor won't work against China's DF-15 SRBM with MARV warhead
The Indian Prithvi AAD works only against dumb warheads that travel in a predictable trajectory. Basically, a Prithvi interceptor was used to shoot down another Prithvi SRBM.
A Chinese DF-15 SRBM is a completely different story. A DF-15 has a maneuverable warhead (MARV or maneuverable reentry vehicle). I don't think the U.S. can shoot down an incoming Mach 6 MARV under real world conditions.
Technically speaking, it is impossible for a supersonic Prithvi to intercept a Mach 6 DF-15 MARV warhead. You need a steerable hypersonic interceptor kill vehicle that can travel at least Mach 6 to have a chance.
Chinese DF-15 SRBM (short-range ballistic missile) with 600km range has a terminal velocity of over Mach 6. China's hypersonic DF-15 SRBM cannot be intercepted by slow-moving supersonic Indian AAD interceptor missile.
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DF-15 - Wikipedia, the free encyclopedia
"The DF-15 uses a solid fuel, single-stage rocket. It is vertically launched from an eight wheeled transporter erector launcher (TEL). The missile's trajectory is guided using small thrusters and an inertial guidance system on the warhead. The warhead is only a tenth of the size of the missile body. After the body and warhead separate, the body trails behind to camouflage the warhead.
The terminal velocity of the missile is over Mach 6.[3]
...
Warhead One, with
Maneuverable reentry vehicles [1]
Blast yield 350-500 kT"
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Too many intractable problems in defending against China
India has lots of problems.
1. Too many Chinese missiles. China has 1,800 SRBMs stationed near the Taiwan coast. It will bankrupt India to build that many interceptors.
2. Chinese DF-15 MARVs traveling at Mach 6 cannot be intercepted with current supersonic Indian AAD interceptor. The technology required is completely different.
3. China is working on stealth HN-2000 cruise missiles. India has a whole host of new problems in trying to protect its interceptor batteries.
4. In a few years, J-20 stealth fighters will be ready. India has to defend its military installations against J-20s as well.
5. India has to defend against WS-2C (350km range) and WS-2D (400km range) MLRS.
6. MIRV problem. The DF-31, DF-31A, and JL-2 all carry 3 MIRVs. It's more economical for China to build MIRVed missiles than it will ever be for India to build interceptors for each warhead. Also, the DF-41 with 10 MIRVs per missile is almost ready. It will never make sense to build 10 interceptors to defend against one DF-41.
I could extend the list, but you get the point. It's a bad position to be that far behind the technological curve.
It's a nightmare to try and build a defense system against a mature missile power like China. China will either destroy your missile defense system first (e.g. stealth strike or overwhelming missile strikes), evade it with MARVs, or overwhelm it with MIRVs.
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As far as I can tell, the U.S. seems to have lost enthusiasm for its ballistic missile defense (BMD) system. China can build triple-MIRVed DF-31A and 10-MIRVed DF-41 ICBMs a lot faster than the U.S. can build interceptors in Alaska.