Indian Agni-4 launch stirs fears of local nuclear war in S Asia amid arms race

[The Deterrent]

Ballistic Glide Re Entry Vehicle (BGRV) and Indian Missile Program

I have read this one, it doesn't talks about Agni-4...rather Shaurya and BGRVs in general. As per the described profile of Shaurya, it indeed possesses the characteristics of BGV, but the Agni series? I think not.

i do not think that it is cable harnessing cover. I do not think it is visible on third vehicle of A4.

See that duct running down from just below the warhead to the exhaust of the second stage (the red one)? That is the cover/duct for the cable harness which is connecting the exhaust vane controls of the second stage with the missile's flight computer. That thing is too fragile to sustain the high temperatures of a hypersonic flight inside the atmosphere.

This the third vehicle, and you can clearly see that red line running down on the second stage.

I do not think that shutting down or restarting of motor is required. small thrushter motors can keep the vehicle on track.

By restarting I meant powered flight in the terminal stage. Of course the thruster motors correct the trajectory after boost phase.

I do not know how much it is true for a missile travelling at a very high speed?

No problem.

This is the first time I am seeing you trolling ......welcome to the club ......

Haha couldn't control it anymore. These guys estimate the CEP of Pakistani weapons in kilometres ...can you imagine?

 

[HariPrasad]

See that duct running down from just below the warhead to the exhaust of the second stage (the red one)? That is the cover/duct for the cable harness which is connecting the exhaust vane controls of the second stage with the missile's flight computer. That thing is too fragile to sustain the high temperatures of a hypersonic flight inside the atmosphere.

They already said that it came across a temperature of 4000 * c. So where is the question of not sustaining high temperature.

By restarting I meant powered flight in the terminal stage. Of course the thruster motors correct the trajectory after boost phase.

That is ok . So what contradiction do you see?

No problem.

Ok . I believe that control surface like A2 is not required for a vehicle traveling at high mach No. It can cruise with whatever control surface it has and correct the trajectory with small thruster motors.

 

[The Deterrent]

They already said that it came across a temperature of 4000 * c. So where is the question of not sustaining high temperature.

Yes, thats what I'm saying. That when it is said that a temperature of 4000C was sustained, it was sustained by the ReV consisting of the payload section only. Not payload+second stage, as second stage cannot survive re-entry.

That is ok . So what contradiction do you see?

Contradiction in what? I didn't get your question.

Ok . I believe that control surface like A2 is not required for a vehicle traveling at high mach No. It can cruise with whatever control surface it has and correct the trajectory with small thruster motors.

If it doesn't have a lift generating surface, it can't "cruise" unless it is powered. It will follow a steep trajectory during re-entry.

 

[kurup]

I have read this one, it doesn't talks about Agni-4...rather Shaurya and BGRVs in general. As per the described profile of Shaurya, it indeed possesses the characteristics of BGV, but the Agni series? I think not.

How about Prithvi ??

See that duct running down from just below the warhead to the exhaust of the second stage (the red one)? That is the cover/duct for the cable harness which is connecting the exhaust vane controls of the second stage with the missile's flight computer. That thing is too fragile to sustain the high temperatures of a hypersonic flight inside the atmosphere.

I always wondered what was that duct .

Is that duct a part of the missile body itself or a seperate part attached to the body ??

By restarting I meant powered flight in the terminal stage. Of course the thruster motors correct the trajectory after boost phase.

No problem.

Does any BM reach hypersonic velocities during the ascend??

Haha couldn't control it anymore. These guys estimate the CEP of Pakistani weapons in kilometres ...can you imagine?

 

[OrionHunter]

is this article supposed to be taken as a pat on the back or just a rhetoric ? Anything short of MIRVed 14k KM ranged SLBM and ICBM should not be acceptable !

We don't need 14k km missiles. Waste of time and money. We need missiles with adequate range to take on China and farthest most portions of Pakistan only.

And yes, the more important issue is MIRVs. We need a few hundred of those, each with between 20 to 200kt yield.

 

[The Deterrent]

How about Prithvi ??

Prithvi is a sort of lift-augumented vehicle. In the terminal stage the large delta wings can be used to generate lift for range extension. But the speed wouldn't be hypersonic, maybe closer to Mach-3.

I always wondered what was that duct .
Is that duct a part of the missile body itself or a seperate part attached to the body ??

That duct contains cables which connect the flight computer with the control mechanism. It is not a part of the body (motor) which is a cylindrical object, rather its attached to it. See the below image for approximate comparison:

Does any BM reach hypersonic velocities during the ascend??

Yes, except smaller SRBMs, ballistic missiles reach hypersonic velocities during ascend. But due to less acceleration during ascent, by the time hypersonic velocity is attained the missile is travelling in the upper atmosphere where the air is less dense. So the atmospheric drag is very less and there is little heat generated on the ReV.

 

[kurup]

Prithvi is a sort of lift-augumented vehicle. In the terminal stage the large delta wings can be used to generate lift for range extension. But the speed wouldn't be hypersonic, maybe closer to Mach-3.

Something like this , right .

Yes, except smaller SRBMs, ballistic missiles reach hypersonic velocities during ascend. But due to less acceleration during ascent, by the time hypersonic velocity is attained the missile is travelling in the upper atmosphere where the air is less dense. So the atmospheric drag is very less and there is little heat generated on the ReV.

Since the apogee of A4 is 900km , Don't you think the A4 second stage will reach hypersonic velocity .

 

[The Deterrent]

Something like this , right .

Yeah.

Since the apogee of A4 is 900km , Don't you think the A4 second stage will reach hypersonic velocity .

This is a common misconception that the boost phase of a ballistic missile continues upto apogee. See the following image for approximate details:

As you can see, the boost phase is smaller and lasts for only about ~15-20% of total flight time.

That being said, Agni-IV obviously attains much more than Mach 5 during its flight time. The speed before re-entry is approximately the same as that after the termination of the boost phase. So at the end of the boost phase, Agni-IV maybe travelling at ~Mach 20 (if aimed for maximum range).
Now the thing is, this velocity is being attained OUTSIDE the atmosphere, so there is negligible drag for the ReV. No drag=no heat generated on ReV. Furthermore, during ascent the acceleration is relatively smaller, so heat generated is very less. As soon as the the ReV begins re-entry during descent, the atmospheric drag causes rapid deceleration and generation of extremely high temperatures on the ReV, until the ReV is slowed down to around ~Mach 4.

 

[kurup]

This is a common misconception that the boost phase of a ballistic missile continues upto apogee.

No, I know that boost phase does not continue upto apogee .

BY 900km apogee what I meant is that compared to 350km apogee of A3 , the second stage of A4 will most probably attain higher velocity .

As you can see, the boost phase is smaller and lasts for only about ~15-20% of total flight time.

That being said, Agni-IV obviously attains much more than Mach 5 during its flight time. The speed before re-entry is approximately the same as that after the termination of the boost phase. So at the end of the boost phase, Agni-IV maybe travelling at ~Mach 20 (if aimed for maximum range).
Now the thing is, this velocity is being attained OUTSIDE the atmosphere, so there is negligible drag for the ReV. No drag=no heat generated on ReV. Furthermore, during ascent the acceleration is relatively smaller, so heat generated is very less. As soon as the the ReV begins re-entry during descent, the atmospheric drag causes rapid deceleration and generation of extremely high temperatures on the ReV, until the ReV is slowed down to around ~Mach 4.

1. What will be max. velocity attained by the missile inside the atmosphere ?? supersonic .

2. According to the image you posted the entire boost phase completes inside the atmosphere itself . This means both the stages of A4 will burnout inside the atmosphere itself ??

 

[IND151]

We are NOT looking for more than 5000km range. There has been no political sanction.

Agni 6 is already under development

 

[The Deterrent]

No, I know that boost phase does not continue upto apogee .

BY 900km apogee what I meant is that compared to 350km apogee of A3 , the second stage of A4 will most probably attain higher velocity .

Oh okay, my bad.
Of course.

1. What will be max. velocity attained by the missile inside the atmosphere ?? supersonic .

That depends on the class of the missile. Agni-IV might have hypersonic velocity within the upper layer of atmosphere.

2. According to the image you posted the entire boost phase completes inside the atmosphere itself . This means both the stages of A4 will burnout inside the atmosphere itself ??

That depends on the time taken by Agni-4's second stage to burn out (the first stage obviously burns out within the atmosphere). If the trajectory in the image (which is a rather approximate/general description) is assumed to be somewhat the same of Agni-4, then yes both stages will burnout within the atmosphere. But given the high-end IRBM class of Agni-4, it is likely that the second stage burns out outside the atmosphere.

 

[typoerror]

Yes, thats what I'm saying. That when it is said that a temperature of 4000C was sustained, it was sustained by the ReV consisting of the payload section only. Not payload+second stage, as second stage cannot survive re-entry.


Contradiction in what? I didn't get your question.



If it doesn't have a lift generating surface, it can't "cruise" unless it is powered. It will follow a steep trajectory during re-entry.

In Hypersonic Flight trajectory mode, the missile does not leave atmosphere, hence no re-entry. That said, I still dont see fins. No fiins, no glide. But A2 RV has fins. And maybe A4 willbe hybridized (bastardized) further with Shaurya and make it a Quasi Ballistic Missile. Imagine the implications of a 5K 40km alt missile.

 

[The Deterrent]

In Hypersonic Flight trajectory mode, the missile does not leave atmosphere, hence no re-entry. That said, I still dont see fins. No fiins, no glide. But A2 RV has fins. And maybe A4 willbe hybridized (bastardized) further with Shaurya and make it a Quasi Ballistic Missile. Imagine the implications of a 5K 40km alt missile.

That depends on the delivery system. If it is something like Shaurya/Iskander, you are correct.
What you are suggesting (solid-fueled quasi-ballistic missile of 5000km range/40km altitude) is close to impossible to achieve, because the physical characteristics (mass) of the missile of that capability would become so large that the corresponding thrust to keep it cruising at the mentioned altitude would be too less to propel it.

 

[typoerror]

That depends on the delivery system. If it is something like Shaurya/Iskander, you are correct.
What you are suggesting (solid-fueled quasi-ballistic missile of 5000km range/40km altitude) is close to impossible to achieve, because the physical characteristics (mass) of the missile of that capability would become so large that the corresponding thrust to keep it cruising at the mentioned altitude would be too less to propel it.

Nonsense, thats where aerodynamics comes in. Ever heard of fins and lift? Also remember, at those speeds a small fin area corresponds to massive lift. Its all possible, but has not been done yet. If we see an A4 with fins on the second stage enough to augment some lift then you know they are on to something

 

[The Deterrent]

Nonsense, thats where aerodynamics comes in. Ever heard of fins and lift? Also remember, at those speeds a small fin area corresponds to massive lift. Its all possible, but has not been done yet. If we see an A4 with fins on the second stage enough to augment some lift then you know they are on to something

I have been talking about "fins and lift" for the past couple of posts.
I termed it impossible under the provided characteristics (solid-fueled quasi-ballistic missile of 5000km range/40km altitude).
But if you talk about a liquid fueled scramjet, something like a giant X-51 Waverider, then yes it can be done in future.