DF 21D VS bRAHMOS 2 HYPERSONIC aSCM A LAYMAN COMPARISION

[gambit]

exactly the same theory stated by another respected member of another forum to me that it wont work .So what guidance would really be employed by chinese in it's terminal guidance i doubt

Most likely radar. But here is my speculations on that...And I posted it here before...

===
1- The latest variant of the DF-21 has reaction thrust steering mechanisms. The radar system is high PRF X-band with a scan limit of 60deg. due to nosecone dimension. Since the target is moving, proportional navigation is employed to provide continuous target track. Despite the fact that the target is moving at only 33 knots, the PN guidance output is then converted to bang-bang guidance commands to provide the vehicle with near instant lateral acceleration to reduce interception probability by air defense missiles. Due to vehicle structural constraints, bang-bang guidance commands are limited to 10g. Standard fighter aircraft air to air missiles, because of their smaller warhead, can have bang-bang guidance forces up to 40g with no catastrophic structural failure.

2- Given the developmental maturity of ballistic defense missile system like the latest US SM-3, it is determined that the best execution altitude for vehicle deceleration for evasive maneuvers to be at 25 km above ground level (AGL). The longer the vehicle remains static, it will provide air defense radars with consistent vehicle profile and descent rate, also with the lower altitude, the higher air density would not allow the 10g evasive maneuvers, therefore the greater the odds of a successful interception. Further, this 10g bang-bang guidance limit is necessary to prevent the vehicle's radar system from losing target line-of-sight (LoS).

3- If this vehicle is used against fixed land targets that has air defense deployments, the vehicle can afford to lose target LoS with higher g-rating evasive maneuvers as target geo-coordinates are also fixed in memory. The vehicle will remember heading offset and deviation rate and can make appropriate return bang-bang guidance commands for the radar to reacquire target information. Against a moving target, even though one moving at only 33 knots, the current technology level does not afford the vehicle to lose a moving target LoS.

4- The latest US SM-3 missile is capable of reaching speed of 9600km/h with a climb rate of 5km/h in altitude, making early descent phase evasive maneuvers important to reduce interception probability. Missile against aircraft engagements typically occurs at or below 10km altitude, making feasible aerodynamic forces exploitation. But because this vehicle will begin to execute evasive maneuvers at very thin air altitude that reduces aerodynamic forces exploitation effectiveness, reaction thrust mechanisms are necessary and this will cost vehicle warhead payload.

5- During development, in post evasive maneuvers analysis, an interface was thought to be required between bang-bang to proportional navigation guidance. Velocity compensated proportional navigation guidance (VCPN) was briefly tested as that interface and but was found to offer statistically negligible improvement in target tracking and guidance. Target lead angle and its rate change are nowhere as extreme as in a missile versus aircraft engagement and any vehicle descent rate change is already reflected in closing speed calculations. Therefore, it was decided to use only proportional and bang-bang navigation guidance methods.

6- Another developmental exploration was the order of guidance laws. The program decided to conduct dual testings. One strategy was bang-bang guidance for initial vehicle-target orientation, evasive maneuvers, then switches to PN guidance at 2km AGL. A parallel strategy has the reverse, PN for initial vehicle-target orientation and bang-bang guidance for evasive maneuvers. It was found that because bang-bang guidance is already sensitive to LoS change and rate of change, hardware related LoS noise can induce evasive maneuvers thrust command oscillations as the guidance laws attempt to null the LoS rate after every execution. This condition is similar to constantly oversteering an automobile, either due to driver ability or steering mechanism 'slop'. When PN guidance takes over at 2km AGL, the program recorded a higher miss rate than the pn_bang-bang strategy. In some instances, the vehicle's radar could not reacquire the target after several violent maneuvers to evade air defense missiles.
===

This is the type of reasonably technical explanations that I am waiting for from any Chinese sources. No 'classified' information need be revealed. Of what I said above, even if I am completely wrong, I would be wrong only about how the DF-12D uses these technologies, not about the technologies themselves. You can take relevant items like 'proportional navigation' or 'guidance laws' to any avionics engineer and he would know exactly what I am talking about.

 

[gubbi]

OT: The fanboiz' silence is deafening!!

 

[FairAndUnbiased]

Most likely radar. But here is my speculations on that...And I posted it here before...

===
1- The latest variant of the DF-21 has reaction thrust steering mechanisms. The radar system is high PRF X-band with a scan limit of 60deg. due to nosecone dimension. Since the target is moving, proportional navigation is employed to provide continuous target track. Despite the fact that the target is moving at only 33 knots, the PN guidance output is then converted to bang-bang guidance commands to provide the vehicle with near instant lateral acceleration to reduce interception probability by air defense missiles. Due to vehicle structural constraints, bang-bang guidance commands are limited to 10g. Standard fighter aircraft air to air missiles, because of their smaller warhead, can have bang-bang guidance forces up to 40g with no catastrophic structural failure.

2- Given the developmental maturity of ballistic defense missile system like the latest US SM-3, it is determined that the best execution altitude for vehicle deceleration for evasive maneuvers to be at 25 km above ground level (AGL). The longer the vehicle remains static, it will provide air defense radars with consistent vehicle profile and descent rate, also with the lower altitude, the higher air density would not allow the 10g evasive maneuvers, therefore the greater the odds of a successful interception. Further, this 10g bang-bang guidance limit is necessary to prevent the vehicle's radar system from losing target line-of-sight (LoS).

3- If this vehicle is used against fixed land targets that has air defense deployments, the vehicle can afford to lose target LoS with higher g-rating evasive maneuvers as target geo-coordinates are also fixed in memory. The vehicle will remember heading offset and deviation rate and can make appropriate return bang-bang guidance commands for the radar to reacquire target information. Against a moving target, even though one moving at only 33 knots, the current technology level does not afford the vehicle to lose a moving target LoS.

4- The latest US SM-3 missile is capable of reaching speed of 9600km/h with a climb rate of 5km/h in altitude, making early descent phase evasive maneuvers important to reduce interception probability. Missile against aircraft engagements typically occurs at or below 10km altitude, making feasible aerodynamic forces exploitation. But because this vehicle will begin to execute evasive maneuvers at very thin air altitude that reduces aerodynamic forces exploitation effectiveness, reaction thrust mechanisms are necessary and this will cost vehicle warhead payload.

5- During development, in post evasive maneuvers analysis, an interface was thought to be required between bang-bang to proportional navigation guidance. Velocity compensated proportional navigation guidance (VCPN) was briefly tested as that interface and but was found to offer statistically negligible improvement in target tracking and guidance. Target lead angle and its rate change are nowhere as extreme as in a missile versus aircraft engagement and any vehicle descent rate change is already reflected in closing speed calculations. Therefore, it was decided to use only proportional and bang-bang navigation guidance methods.

6- Another developmental exploration was the order of guidance laws. The program decided to conduct dual testings. One strategy was bang-bang guidance for initial vehicle-target orientation, evasive maneuvers, then switches to PN guidance at 2km AGL. A parallel strategy has the reverse, PN for initial vehicle-target orientation and bang-bang guidance for evasive maneuvers. It was found that because bang-bang guidance is already sensitive to LoS change and rate of change, hardware related LoS noise can induce evasive maneuvers thrust command oscillations as the guidance laws attempt to null the LoS rate after every execution. This condition is similar to constantly oversteering an automobile, either due to driver ability or steering mechanism 'slop'. When PN guidance takes over at 2km AGL, the program recorded a higher miss rate than the pn_bang-bang strategy. In some instances, the vehicle's radar could not reacquire the target after several violent maneuvers to evade air defense missiles.
===

This is the type of reasonably technical explanations that I am waiting for from any Chinese sources. No 'classified' information need be revealed. Of what I said above, even if I am completely wrong, I would be wrong only about how the DF-12D uses these technologies, not about the technologies themselves. You can take relevant items like 'proportional navigation' or 'guidance laws' to any avionics engineer and he would know exactly what I am talking about.

What about cluster munitions? The kinetic energy of even a 100 kg block of steel hitting something at Mach 10 is pretty powerful. 580 MJ actually, which is about 1/3 the energy of a lightning bolt condensed as pure kinetic energy. More than enough to penetrate a carrier flight deck. With a 1000 kg payload, the DF-21 can spread 10 of these out, or with a 50 kg payload, 20 of these out. An explosion separating the cluster munitions, by conservation of momentum, would not change their direction or the speed of their collective center of mass.

The missile only needs to make minimal guidance such that the center of mass would be on the carrier, which would greatly increase the probability that any one piece would impact a carrier.

Also, the heat generated from impact is not negligible, and if the fuel holder gets hit, it may ignite the entire carrier.

In addition, the cost of a DF-21 is about 10 million dollars, while the cost of a carrier + associated planes is somewhere like 3 billion. Using 300 DF-21s to sink 1 carrier would only break even.

 

[siegecrossbow]

Isn't comparing ballistic and cruise missiles a bit like comparing apples and oranges? DF-21 and Brahmos are definitely intended for very different roles.

 

[faithfulguy]

Isn't comparing ballistic and cruise missiles a bit like comparing apples and oranges? DF-21 and Brahmos are definitely intended for very different roles.

But since China do not have a weapon system similar to Brahmos that is worthy of comparison to Brahmos ( at least in their mind, but I do not know enough about what China has), they decide to compare it to DF-21.

 

[Nan Yang]

In addition, the cost of a DF-21 is about 10 million dollars, while the cost of a carrier + associated planes is somewhere like 3 billion. Using 300 DF-21s to sink 1 carrier would only break even.

300 ? I think its more like 10,000 !!!!

But analysts estimate that China will be able to produce 10,000 of the new missiles for the price of a single US aircraft carrier – so even with poor targeting, they could pose a serious threat.

US military leaders have, for their part, generally attempted to project sangfroid in the face of news about China’s developing area denial power, arguing that a single missile won’t change the balance of power in the region. But a missile capable of striking a ship nearly 3,000 kilometres from China's coast could end the US’s traditional ability to sail through disputed waters with impunity. It would certainly lead future US presidents to think twice before sending carriers to pass through the Taiwan Straits during standoffs between the two Chinas.

 

[gambit]

What about cluster munitions? The kinetic energy of even a 100 kg block of steel hitting something at Mach 10 is pretty powerful. 580 MJ actually, which is about 1/3 the energy of a lightning bolt condensed as pure kinetic energy. More than enough to penetrate a carrier flight deck. With a 1000 kg payload, the DF-21 can spread 10 of these out, or with a 50 kg payload, 20 of these out. An explosion separating the cluster munitions, by conservation of momentum, would not change their direction or the speed of their collective center of mass.

The missile only needs to make minimal guidance such that the center of mass would be on the carrier, which would greatly increase the probability that any one piece would impact a carrier.

Also, the heat generated from impact is not negligible, and if the fuel holder gets hit, it may ignite the entire carrier.

Today's aircraft carriers are nothing like WW II era ships. Nothing except for their shapes. Aircraft carriers of that era were constructed prior to the war and were originally designed to be tankers, battleships, and even cruisers.

For example...

Japanese cruiser Ibuki (1943) - Wikipedia, the free encyclopedia

The Japanese Navy considered completing Ibuki as a fleet oiler for underway replenishment, a capability that the Navy needed. However, since Ibuki's hull was already complete and Japan was desperate for carriers, she was towed to Sasebo in November 1943 to be converted to a light aircraft carrier.

All the major sea capable military powers of that day did conversions rather than true original designs. Everyone was familiar with hulls for tankers, battleships, and assorted lighter hulls so it made sense to turn them into aircraft carriers and it was quicker to modernize a navy with that.

The first keyword search for you is 'oriskany sinking'. The USS Oriskany was constructed during WW II where the design was on the cusp between being truly designed as an aircraft carrier and being adapted from an existing hull. To sink this ship, aside from the preparation for environmental reasons, it took a lot of work to deliberately prepare the ship for sinking.

The next keyword search for you is 'enterprise deck fire'. The USS Enterprise CVN version was a truly originally designed to be an aircraft carrier, not of a conversion of a built hull or an adaption of a previous hull design. The weapons related accident penetrated the decks all the way down to the waterline level and we are talking about exploding ordnance here. A lot of WW II navy combat veterans of different countries determined that if the Enterprise was at war, the deck would have been repaired at sea, and the ship would have been able to continue to prosecute the war. Air operations would be diminished, of course, but not entirely stopped. But since this was peace time and we do not want to send ships on patrol in a diminished capacity, the Enterprise returned to port for repairs. We will fight with diminished capacity in war if necessary and usually we do, but at the start of the war, we want the highest capable force we can wield to do as much damage and as quickly to the enemy as possible. So repairs were necessary. The repaired Enterprise continued to serve to this day and is scheduled to retire in 2013.

So as you can see for yourself, it is not that easy to sink or damage a modern post WW II aircraft carrier to the point of stopping air operations, especially if you are talking about those of the world's most experienced and powerful navy fielding two dozens of these ships in various displacements: US.

Cluster munitions? We have discussed this before and your fellow Chinese claimants of them ran with their tails between their legs. Problems with cluster munitions are evident and the most prominent one is dispense altitude: How high? In order to have a 'spread' you must have angular differences of individual munitions. So the higher the dispense altitude, the wider the spread, but here is a major problem with that...

That is a MIRV-ed warhead assembly containing several sub-munitions. Assuming the DF-12D has approximate dimensions, how many sub-munitions do you want to carry? The higher the amount you want to carry, the smaller each sub-munition will be and therefore the less destructive power each will have. This decision will affect your dispense altitude. You still need to explain to interested readers, let alone me, on whether or not you will install sensor-guidance packages into these sub-munitions. If you do, that will further reduce the explosive material size you have. But if your sub-munitions can benefit from a reasonably accurate sensor-guidance package, it would be foolish to use sub-munitions in the first place precisely because of the inevitable reduced destructive power you can bring to bear. Better off to launch several unitary munitions over cluster munitions.

The DF-21D with cluster munitions will be a cluster-fvcked weapon.

You can get away with this simple argument over at the Chinese boards where everyone has no relevant experience and therefore is gullible but not here with me.

In addition, the cost of a DF-21 is about 10 million dollars, while the cost of a carrier + associated planes is somewhere like 3 billion. Using 300 DF-21s to sink 1 carrier would only break even.

Do you have any idea on how much it cost, in both tangible and intangible terms, after you lose a war? Of course not. You are still a child. Never served a day in uniform, perhaps as a member of a fast food franchise, probably rejected from conscription, and are still trying to learn something of this world.

 

[gambit]

Isn't comparing ballistic and cruise missiles a bit like comparing apples and oranges? DF-21 and Brahmos are definitely intended for very different roles.

Each approach a target in different manners. Each approach have advantages and disadvantages. The DF-21D's ballistic approach has the advantage of speed over time and over distance. The Brahmos' aerodynamic approach has the advantage of flexibility in virtually all situations. The wise move -- and most expensive -- would be to have both. One attack mode to force an adversary to change his tactics -- should he survive -- and straight into the advantages of the other mode.

 

[SQ8]

Lets look at it this way..
Penetrating warhead heading for a carrier from the top.. a top that is think steel deck and multiple reinforced layers..by a hypersonic speed warhead.
Or a side attack on comparably less think side walls and/or perhaps through the lift openings by a hypersonic warhead.

 

[gambit]

Lets look at it this way..
Penetrating warhead heading for a carrier from the top.. a top that is think steel deck and multiple reinforced layers..by a hypersonic speed warhead.
Or a side attack on comparably less think side walls and/or perhaps through the lift openings by a hypersonic warhead.

Hope you will pardon me but that is precisely the problem we want to avoid. If you design the DF-12D for a carrier, you might as well design it for ALL ships, regardless of what you may see from above. The reason why the DF-12D is called a 'carrier killer' is simply because the aircraft carrier is the most potent -- physically and symbolically -- weapon a country can send to make a statement.

I said 'called', not 'considered'.

I have far more respect for the Chinese than others in this regard. I am 99.999% certain that the Chinese intend this for ANY ship that conforms to a certain sensory -- radar or infrared -- perception. The aircraft carrier with its flat plate top simply offer the most prominent sensor return of any type. It would convenient and expedient if the Chinese has technological limitations in the sensory arena that forced them to focus solely on the aircraft carrier based upon this singular sensory characteristic. But I doubt that the Chinese has this technological limitation.

 

[OrionHunter]

Considering that the DF-21D would have a terminal velocity of mach 10+, it would be almost impossible to maneuver it onto a moving aircraft carrier on the high seas.

 

[SEAL]

DF-21 is ballistic missile and Brahsomse is anti-ship missile the correct comparison will be between anti-ship missiles.
India depends on Russia for ramjet and scramjet engines so i think it will not be problem for China to get some scramjet motors and tell Indians hypersonic is not a big deal.

 

[gambit]

DF-21 is ballistic missile and Brahsomse is anti-ship missile the correct comparison will be between anti-ship missiles.
India depends on Russia for ramjet and scramjet engines so i think it will not be problem for China to get some scramjet motors and tell Indians hypersonic is not a big deal.

The word 'ballistic' mean the mode or method of flight. A mortar round has a ballistic trajectory. If you fire a gun straight up, the bullet will have a ballistic trajectory. The 'anti-ship' is the mission type that is independent of the mode of flight. You can use a mortar against a ship or a tank.

 

[SQ8]

Hope you will pardon me but that is precisely the problem we want to avoid. If you design the DF-12D for a carrier, you might as well design it for ALL ships, regardless of what you may see from above. The reason why the DF-12D is called a 'carrier killer' is simply because the aircraft carrier is the most potent -- physically and symbolically -- weapon a country can send to make a statement.

I said 'called', not 'considered'.

I have far more respect for the Chinese than others in this regard. I am 99.999% certain that the Chinese intend this for ANY ship that conforms to a certain sensory -- radar or infrared -- perception. The aircraft carrier with its flat plate top simply offer the most prominent sensor return of any type. It would convenient and expedient if the Chinese has technological limitations in the sensory arena that forced them to focus solely on the aircraft carrier based upon this singular sensory characteristic. But I doubt that the Chinese has this technological limitation.

Gambit, that is from a EM(or IR) perspective.
I refer to effectiveness of the weapon when it comes to causing enough damage so to drastically reduce or negate its effectiveness in the battlezone.

 

[gambit]

Gambit, that is from a EM(or IR) perspective.
I refer to effectiveness of the weapon when it comes to causing enough damage so to drastically reduce or negate its effectiveness in the battlezone.

Ah...From that perspective, then the question turn to which method of attack (or area of damages) will give us the most IMMEDIATE effect of:

- Either a respite from air operations.
- Or a complete elimination of the same.

Anyone who has ever served on an aircraft carrier will tell you that it will be a direct physical assault topside. It is normal that upon being physically assaulted, everyone on a ship will pause to take stock of the situation. Was my area of responsibility affected? How many casualties? Were they from my crew? What are the equipment damages, if any? And so on...Most important will be damage control and to give way to that crew. If hit broadside, the aircraft carrier will still take a respite to make those assessments, however, as soon as it is determined that damaged sub-systems are not crucial to air operations, said operations will resume. What this mean is that a hit topside will create a longer period of respite from air operations than a hit broadside. The flight deck is the final staging area for those operations. A hit on the flight deck from a falling explosive projectile WILL produce damages to below levels, but a hit broadside may not do any damages to the flight deck at all.

On the other hand, if there are sufficient multiple hits broadside and the results are severe damages to the interior, then physical integrity of the flight deck is irrelevant because you will have lost too many aircrafts, too many men, too many support equipment, you are taking in water and it is listing the ship, etc...etc...In other words, a single well placed 'small' hit in a vital area will produce the same effect as multiple 'larger' hits in different areas whose decreased contributions to the overall capability have YET to be felt.

From this perspective, the DF-21D's method is the appropriate one to match the goal. However, intent is not the same as capability. I can intend to throw the ball through the hoop but if I do not have the same talent as Michael Jordan, my intentions are worthless. The DF-21D's capability to hit a 'High accuracy, High precision' pattern is still in doubt. Resource wise, the Brahmos offers many more opportunities for a highly incremental testing regime to increase reliability than the DF-21D could. Keep in mind that a missile is essentially a throwaway weapon. A single Brahmos missile can even be programmed to be in a 'non-destructive' test, meaning it can be programmed to deliberately miss the target to test other challenges, such as countermeasures, and the missile itself can be recovered for analysis. The US have done this with our Tomahawk cruise missiles many times over. Whereas with a ballistic missile, we have to test across large expanse of the seas that can intrude into international waters, open for everyone and anyone to observe and record. The missile itself may not be recoverable despite our best efforts to make it so.

What this mean is that the Brahmos as a weapon system will be a more rapidly developed and deployed system than the DF-21D. What this also mean is that such a weapon system can sooner become a deterrence than its adversary. The military can also sooner train and refine tactics with it. On the surface, this may sound attractive, but if there is a peace, even an uneasy one, between adversaries, then this peace can offer time for the other side to develop its own weapon system that although require more time and resources to develop, will give a more immediate debilitating result in an attack on a ship.