Supratik wrote:Yes. Trying to do out of the box thinking unless it is not scientifically possible. The idea is to neuter in the boost phase.
Not going to be practical for you require quite a lot of speed at a fairly decent altitude where both advanced ramjets and scramjets will struggle. A typical Intermediate Range Ballistic Missile with a 400-500 km apogee will have 2.5-3.5 minute boost phase. Provided you have early warning provided by Satelites and have constant high quality IRST sensor in the air at the time of launch you would still have to give perhaps a minute or so for this to work and the ballistic missile to break cloud cover and be constantly tracked by your targeting sensor. MIT Lincoln Labs in their analysis actually use 80 seconds as a good assumption given varying weather conditions and assume a 180 second boost phase for a 2000km ranged ballistic missile with a 500 km apogee.
They developed a model where a hypothetical air launched, large boost phase interceptor missile with a top speed of 4 km/s (Mach 11) with a 20 second burn time was launched from an altitude of 50,000 ft roughly 90 seconds post ballistic missile launch. Intercept range was limited by IRST targeting sensor performance. In such a case against the ballistic missile described earlier the intercept would take at roughly 170 seconds post launch so you have a 10 second margin. Overall you could do an assent phase intercept post burn out depending upon how quickly PIP is calculated but that would be at altitudes that essentially require a KKV.
For shorter ranged, less sophisticated ballistic missile threats, Dr. Canavan did some academic work at Livermore and found that a ballistic missile with a 500-600 km range, launched a few hundred km's inland has a 75 second burnout time and would require an interceptor with an average velocity of 6.7 km/s . The stress here comes from the significantly shorter boost phase compared to the IRBM example cited above. This assumes that the target ballistic missile is launched from 300 km inside of enemy territory and that the ground launched interceptor is being fed targeting through an airborne sensor and is roughly 400 km away from the TEL (i.e. 100 km inland). In a nutshell, whether that is intercepting very short range ballistic missiles, MRBM's or IRBM's you need a very fast interceptor missile system which makes cruise missiles a poor choice for such a role.
Doesn't mean cruise missiles or loitering munitions aren't helpful in ballistic missile defense, but just not for boost or assent phases. They can play a very important role in left of launch scenarios and TEL hunting.
A 5 km/s interceptor can only get to 100 km in 30 s, which is too small for even short-range missiles. It could get to about 300 km in 75 s, which might be adequate for forward-deployed short-range SCUDs. The 7.5 km/s interceptor could still only get to about 100 in 30 s, but it could reach almost 400 km in 75 s. A 10 km/s interceptor could get to about 500 km in 75 s, and a 12.5 km/s interceptor could get to about 550 km in that time, which would cover most theater threats. Note, however, that for the latter case, a delay of only 10 s would reduce the range about 100 km.