can we use Scram Jet in Agni series !
@PARIKRAMA
As long as we wish to have a missile with propulsion system inside the atmospheric limit (not in vaccum meaning space), scram jet is a viable solution bcz it reduces the weight of the system drastically by reducing the need of the oxidiser. For such a system you will require a a initial rocket to boost it to a particular speed so that scramjet can takeover and begin the flight.
I am quoting here Prof Micheal K Smart, Centre of Hypersonics, University of Queensland
Antonio Ferri aptly described the important differences between rockets and airbreathing engines as:
1) The potential specific impulse of airbreathing propulsion is much larger than any chemical rocket, due to the fact it carries only fuel and not oxidiser.
2) Structural weight of an airbreathing engine is larger for the same thrust than a rocket, because it must process air (oxygen and nitrogen) and have an intake, whereas the rocket has an oxidiser tank and pressurization system.
3) The thrust of an airbreathing engine is a function of flight Mach number and altitude. Large thrust per unit frontal area can only be obtained in the dense atmosphere, while rockets can operate at high thrust per unit frontal area in a vacuum.
4) The necessity for flight in the atmosphere introduces severe structural problems for the airbreathing engine associated with aerodynamic heating and vehicle drag. However, the vehicle has a greater potential for manoeuvring than a rocket traveling in a vacuum, through the use of aerodynamic lift.
The flight corridor for scramjet propelled vehicles, either for cruise or ascent to low-earth-orbit, is constrained at upper altitude by the need to operate the airbreathing engine, and at lower altitude by structural limits of the vehicle. Figure 1 gives an indication of these limits, and includes a suggested ascent trajectory for an airbreathing access-to-space vehicle, with turbojet operation up to Mach 3-4, scramjet operation up to Mach 15-17 and then rocket based propulsion for the final boost to low earth orbital velocity, which is approximately 7.9 km/s.
In the design of hypersonic inlets there are some key operability issues that must be addressed in order to
arrive at a useful configuration. These are:
1) Inlet starting limits.
2) Boundary layer separation limits.
3) Minimization of external drag.
4) Performance at off-design Mach number.
In another paper, Prof Smart gave this
This figure tends to showcase the limitations effect much better than earlier figure
Source:
https://www.sto.nato. int/publications/STO%20Educational%20Notes/RTO-EN-AVT-150/EN-AVT-150-09.pdf
http://www.dtic. mil/get-tr-doc/pdf?AD=ADA581900
What i understand is as on today, we are yet to master this technology with enough confidence to see how it can work for us. The hypersonic Brahmos 2 may be a good way to see the challenges in a weapons delivery platform based challenges together with RLV TD and LEX/HEX missions.
I dont see Agni series being replaced by them for next 2 decades. But i wont be surprised if there is a chance that a new Agni missile is made where upon the boost phase or re- entry the missile payload may contain smaller payloads with scramjet abilities (a la MIRV but with smaller scramjets installed) . A proper anti BMD system which may help us spread our warheads over say a radius of 1000 km and attack at one go multiple HV targets to cripple the enemy.
If you ask me honestly i forsee more destructive power with less issues in a concept called Kinetic Bombardment. I like this concept much more. But then i dont know if India would ever pursue it.