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DF 21D VS bRAHMOS 2 HYPERSONIC aSCM A LAYMAN COMPARISION

which antiship missile is going to be a real threat in future wars ?


  • Total voters
    48
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.
It's actually mach 12. And we've already tested it by destroying a decommissioned PLAN vessel earlier this year. Gambit's frantic copy & paste from engineering textbooks to "prove" cannot be done what is already done is pretty sad.

http://the-diplomat.com/flashpoints-blog/2011/11/22/asbm-defense-isn’t-easy/
 
It's actually mach 12. And we've already tested it by destroying a decommissioned PLAN vessel earlier this year. Gambit's frantic copy & paste from engineering textbooks to "prove" cannot be done what is already done is pretty sad.

ASBM Defense Isn
You have a reading comprehension problem typical of those who have no relevant experience but is desperate to prove his relevancy in a debate. NOWHERE have I stated that the DF-21D is technically impossible. Never even hinted so. You can take post 46 to any avionics engineer and he will tell you the items I cited do exist and that while their incorporation into a functional device is feasible, making the device work as intended is an endeavor that will require the nation's best.

Here is yours and the rest of the Chinese boys' problem: If you take my post 46 to a Chinese avionics engineer, most likely he will run away from speculating about it out of fear of being imprisoned. But if I -- an anonymous Internet character -- is able to post a reasonably technically credible speculation on how the DF-21D might work on a publicly accessible forum to give the interested laymen an idea of what is involved, what do you think the scientists and engineers working in the American Ballistic Missile Defense (BMD) program with the latest technology working for them can speculate about the DF21-D and how to counter it?

Here is something you conveniently ignored from your own source...

ASBM Defense Isn
But impressive technology isn’t always superior.
If that criticism can be levied against the American CIWS, then why is it inapplicable to the DF-21D? Because it is a Chinese product, of course. :lol: That is how you boys think.

Think about the scope of the problem. Terminal velocity for the DF-21 family of missiles is estimated at Mach 10 to Mach 12, on the order of 8,000 to 9,000 miles per hour. That means the missile covers up to 150 miles each minute, or 2.5 miles per second. At such speeds, CIWS gets around a second to engage a maneuvering target, correct its stream of projectiles onto the target, and make the kill. That’s tough even for a computer-controlled weapon system.
Then why are the problems I speculated about in post 46 is easy for the DF-21D? Because it is a Chinese product, of course. :lol: Closing speed related issues do not exist in 'Chinese physics'.

And even if the engagement succeeds, detonating the warhead, the debris from the explosion keeps coming along roughly the same trajectory. In all likelihood, some of the debris peppers the ship. Metal shards traveling at hypersonic velocities retain enormous kinetic energy, more than enough to penetrate the lightly armored hulls of modern warships and inflict all manner of havoc within.
True, but here is the problem for your argument, Mr. Holmes: Which is more lethal to the human body, a single large sword thrust to the torso, or several knife cuts to the limbs? The analogy is quite appropriate here. Diverse debris masses impacting different areas of the ship will not damage the ship the same way a unitary mass can.

Your source is about criticism of the CIWS, not anything about the DF-21D testing program. It does not mention successes or failures. Try again.
 
Gambit

From your last post one may assume that given enough testing time, the DF-21D may become a more effective weapon(if the guidance issues which do seem formidable can be sorted out) than a Brahmos.
I do not intend to call it superior as to me these are still apples and oranges.. but when I say more effective I refer to a perfected(if such a term may apply) DF-21D with a unitary warhead being more effective than a Brahmos at killing a carrier.
However.. compared to a carrier, a Arleigh Burke may not be such an easy target for a DF-21D as it would be for a Brahmos.
 
Gambit

From your last post one may assume that given enough testing time, the DF-21D may become a more effective weapon(if the guidance issues which do seem formidable can be sorted out) than a Brahmos.
I do not intend to call it superior as to me these are still apples and oranges.. but when I say more effective I refer to a perfected(if such a term may apply) DF-21D with a unitary warhead being more effective than a Brahmos at killing a carrier.
However.. compared to a carrier, a Arleigh Burke may not be such an easy target for a DF-21D as it would be for a Brahmos.

Brahmos II would be carried by stealth planes in its weapon bays....
A lot cheaper than DF-21D...
Can be fired in large numbers at the single target...
Lighter can be carried on warships in large numbers...
would fly lower hence No early detection....
flexible to use and move...

And there are many points in which brahmos scores over DF-21... Specially when it would be carried in the weapon bays of FGFA/PAKFA forming a deadly combination of stealth and speed... and would be launched from many directions at an Aircraft carrier..sinking it or damaging it enough... to sail back home..

While DF-21 being a bulkier missile would have the sledge hammer punch but would lack flexibility, ease of deployment, surprise element etc... and could result in a bigger retaliation from the enemy.
 
Brahmos II would be carried by stealth planes in its weapon bays....
A lot cheaper than DF-21D...
Can be fired in large numbers at the single target...
Lighter can be carried on warships in large numbers...
would fly lower hence No early detection....
flexible to use and move...

And there are many points in which brahmos scores over DF-21... Specially when it would be carried in the weapon bays of FGFA/PAKFA forming a deadly combination of stealth and speed... and would be launched from many directions at an Aircraft carrier..sinking it or damaging it enough... to sail back home..

While DF-21 being a bulkier missile would have the sledge hammer punch but would lack flexibility, ease of deployment, surprise element etc... and could result in a bigger retaliation from the enemy.

No... Just no...
 
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

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...

mirv_assembly_009.jpg


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.


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.

Cost: yes, which is why it is worth it to trade X missiles, as many as it takes, for a carrier, since it is essentially a risk free weapon: it can attack the carrier, for as long as it takes essentially, while the carrier cannot strike back; the cost of losing the war is far greater than just building thousands of missiles.

Cluster munitions: I cannot quantitatively answer this question, but I'd imagine, there will be initial guidance before separation, with extrapolation of ship position at early re-entry from current momentum (since the ship cannot realistically change its momentum significantly in the order of seconds during re-entry), and a release in the upper atmosphere where aerodynamic effects would not throw off the munitions paths. The munitions should be limited in number, maybe each 250 kg for 4x, to increase the probability of hit.

What would essentially be 4x 500 pound bombs at Mach 10 would be devastating to a carrier; a 127 mm Zuni rocket, probably weighing in at less than 50 kg and perfectly stationary on the flight deck, caused the Enterprise fire which killed 27. Even ONE of these hitting the carrier would be devastating.
 
Gambit

From your last post one may assume that given enough testing time, the DF-21D may become a more effective weapon(if the guidance issues which do seem formidable can be sorted out) than a Brahmos.
I do not intend to call it superior as to me these are still apples and oranges.. but when I say more effective I refer to a perfected(if such a term may apply) DF-21D with a unitary warhead being more effective than a Brahmos at killing a carrier.
However.. compared to a carrier, a Arleigh Burke may not be such an easy target for a DF-21D as it would be for a Brahmos.
From a sensor perspective, if I was instructed by the customer to focus in on the sensory perception, radar or IR, of an 'aircraft carrier' type signature, it would be an easy task -- for me. The physical dimensions of this ship poses no credible challenges once its sensor characteristics, radar or IR, is produced and acquired.

For the guidance engineer, the technical hurdles are enormous, sensor target and flight controls inputs updates are real time dynamic variables whose compensatory methods, from said guidance engineer, cannot trespass the millisecond barrier, in other words, whatever his methods are to compensate for weather phenomenon that may block the sensor's view of the target or that the flight controls system detected a course deviation, they must be within milliseconds of receiving those variables. Target updates can be one millisecond or one hour and it does not matter, his methods must process each update within milliseconds and send the appropriate commands to the flight controls within milliseconds. Flight controls do not have that luxury, to keep the vehicle in stable flight, the FLCS system must monitor air data, gyros, accelerometers, and surface deflections and positions, at all time. If there is a course deviation detected, and there will be, the FLCS system must query the guidance section for instructions, the guidance engineer's methods must respond within milliseconds.

For the flight controls system engineer, his problems are equally enormous because he must deal with mechanical variables, such as materials and manufacturing defects. Those variables inevitably exists and will introduce system noise, which can give erroneous data regarding the flight control status itself, which in turn will query the guidance section for instructions, which can give compensatory instructions that will fail the mission. The problem here is that because the guidance section have no way of telling if the query for instructions is valid or not, the guidance engineer MUST have complete trust that whatever query he receive it is a valid one, hence his methods will automatically assume that ALL queries are valid.

From a system engineering perspective, we cannot have Sensor, Guidance, and FLCS second guessing each other. That would create chaos within the system. FLCS and guidance engineers work much more closely with each other than with Sensor, often times a person may be both, not merely work on/with both, if he is talented enough. Sensor provide the mission goal, so to speak, and everyone else must work to accommodate that mission. Guidance and FLCS must have complete trust that the goal provided is a valid one and that is why a missile can be misled by decoys. It is Sensor's responsibility to discriminate between the true and the false.

The above technical hurdles are applicable to all weapons systems, be it missiles or dropped 'stupid' bombs. They only differ in terms of complexity.

In a ballistic approach to the target, speed is a 'one-way' variable in the sense that since gravity is the source of motion, any loss in speed cannot be regained. Closing speed compensation algorithms need not and are not as sophisticated as when speed can be 'throttled' or is 'two-way'. A thought to consider: Given the high speed approach of the ballistic method, the system will have very limited time to compensate for any corrections required. So from this perspective, is it really necessary to have as capable a sensor/guidance/FLCS integration as thought? No.

However, when the customer's requirement is that we are using a non-nuclear explosion to destroy an already difficult target, then said integration must adapt some of the complexity level of if speed is a 'two-way' variable because we must attempt to have 100% successful impact in every missile launch. Unlike a fixed land target, sensor target updates of this moving object must increase. The guidance section is now receiving more course deviations information from sensor and must send appropriate compensatory commands to FLCS to correct the flight path, and given the high closing speed between warhead and target, course corrections must have near instantaneous response.

There are two reasons why we must have a 'near instantaneous response' capability:

- High closing speed between two objects.
- Short distance between two objects.

Both situations give us 'compressed response' time.

GBU-12 Paveway II - Wikipedia, the free encyclopedia
Paveway II laser guided bombs use what is known as "bang bang" guidance. This means the bomb's fins deflect fully, rather than proportionally when it is attempting to guide to the laser spot. For example, if it sees the laser spot and determines that it should make a change it deflects its fins until it has over-corrected and then it deflects back the opposite direction creating a sinusoidal type of flight path. This type of guidance may be less efficient at times.
The Paveway bomb uses bang-bang guidance because of the 'short distance' situation. I am very confident that the DF-21D guidance system uses bang-bang guidance because of the high speed situation, not entirely like the Paveway bomb but as part of a composite guidance system. The bang-bang guidance method require a very tough FLCS but that does not mean it must be durable. This is meant to destroy itself, after all, so what is there the need to have durable mechanical devices. They just need to be tough enough to withstand extreme stresses in their short time of existence.

The situation is different for the cruise missile. Even though both ballistic and cruise missiles are technically 'aircrafts' the latter is more so. Its speed variable is 'two-way' in that if it must maneuver due to terrain, its speed will be lost and regained when the FLCC throttles up again. Its sensor/guidance/FLCS integration algorithms will inevitably be more sophisticated. Its FLCS must be both tough and durable for mechanical devices, especially if the weapon is designed to compensate for decoys because it must ignore the deception if it recognized such and to try to reacquire the true target. The ballistic approach does not allow this capability.

Efficacy - Wikipedia, the free encyclopedia
Efficacy is the capacity to produce an effect.
So how does all this mumbo-jumbo related to 'efficacy', which is to stop an aircraft carrier from producing attack aircrafts? It is well known that given time, we can correct for errors, which includes deceptions. The subsonic approach give us that capability, at the cost of time, of course.

gulfnews : Tomahawk cruise missile used for long-distance precision strikes
Radar detection of a flying Tomahawk, whose range could exceed 2,500 kilometres is difficult because of the missile's small radar cross-section and low altitude flight.
That is the intended distance for the DF-21D so distance is not an issue for the cruise missile design itself, be it the Tomahawk or the Brahmos models.

To date, despite what the Chinese members here may say, there is no credible data on the success of the ballistic approach to destroy a moving target, even one as slow moving like a ship, whereas for the cruise missile, from the early Exocet to the more sophisticated later Tomahawk, we have plenty of data of these weapons' ability to acquire moving target.

So if we define 'efficacy' here as to stop an aircraft carrier from producing aircrafts, then the DF-21D will take the seat PROVIDED that it must have at least comparable successes in hitting its targets as the cruise missile design. The impact of ONE unitary warhead will force an aircraft carrier to at least have a long respite if not complete cessation of air operations.

But if we define 'efficacy' here as to hit a ship, be it the large aircraft carrier or the smaller destroyer type, then given what we know of missile guidance technology, see 'mumbo-jumbo' above, and cruise missile successes, then the Brahmos must be given priority. Some opinions I have heard is that the Indians have given that capability more hoopla than it deserve, however, when taken into tactical situations such as proximity to an adversary, as in 'next door neighbor' type, that Mach capability will be more valuable in the long run. The Brahmos is a more flexible weapon than the DF-21D but at the cost of immediate potency upon hitting a target.

Going back to the first paragraph...

From a sensor perspective, if I was instructed by the customer to detect as wide a range of 'ship type' sensory perceptions, radar or IR, as possible, from an aircraft carrier to a cruiser to a dingy, the task would have much greater difficulty but still quite 'doable'. We already can do that. But once I handed off these signals to Guidance and FLCS, the burden of making the concept into a workable weapon falls upon them. The reverse applies to me as well. If Guidance and FLCS present to everyone the successful response required regardless of Sensor inputs, hypothetical or real, then the burden falls upon me to provide the final piece to produce a working weapon.
 
^ Mate you need to join a think tank or something, your knowledge is wasted here.
 
How about the C-301 cruise missile China developed in the 80s?

Range: Brahmos 290km, C301 180km
Speed: Brahmos Mach 2.8, C301 2.5
Weight: Brahmos 3 ton, C301 3.4
Warhead: Brahmos 300kg, C301 500kg
 
Gambit.. thanks for that.

I do have 90% of an idea what you were talking about and would have given similar ideas but it would be more "universal" coming from you.

Now if I can give it an example. A certain system I worked on requires input from a gyro which is accurate to x and an accelerometer that is accurate to y.the gyro sensor has a higher update rate than the accel-meter , almost twice as fast.
Guidance is terminal supported/supplemented by a IR sensor after re-entry.
FLCS is directing a TV system for boost and second stage.. along with non Bang-Bang fins for atmospheric maneuvering after reentry. Sensors are linked to a FPGA that takes inputs from the gyro, the accellerometer, IR and command link..and outputs those to the Servo's controlling the fins. A GPP sits on top of this system keeping a check on command links and any guidance corrections,fuel monitors,engine monitors and modes
The package is done.. it has been tested.

Vis a vis the cost.. which control system will cost more?
One for a BM or a CM?
 
Any why is that so ??

Way too big to carry be carried internally. As it is, it takes a beast like the modified Su-30MKI to carry it externally (afaik, the Su-30MKI will be the only fighter aircraft in the world capable of carrying such a cruise missile).
 
Gambit.. thanks for that.

I do have 90% of an idea what you were talking about and would have given similar ideas but it would be more "universal" coming from you.

Now if I can give it an example. A certain system I worked on requires input from a gyro which is accurate to x and an accelerometer that is accurate to y.the gyro sensor has a higher update rate than the accel-meter , almost twice as fast.
Guidance is terminal supported/supplemented by a IR sensor after re-entry.
FLCS is directing a TV system for boost and second stage.. along with non Bang-Bang fins for atmospheric maneuvering after reentry. Sensors are linked to a FPGA that takes inputs from the gyro, the accellerometer, IR and command link..and outputs those to the Servo's controlling the fins. A GPP sits on top of this system keeping a check on command links and any guidance corrections,fuel monitors,engine monitors and modes
The package is done.. it has been tested.

Vis a vis the cost.. which control system will cost more?
One for a BM or a CM?
Difficult to guess but for the discussion's sake I would say the ballistic approach would be the more expensive.

Here is why I guess so and for the interested laymen I will digress in a technical direction...

First...The lay readers should understand that there is a difference between using gyros/accels signals for flight controls versus for navigation. Both uses displacement data but for different purposes and those differences dictate physical constructions of these units. For navigation, gyros/accels displacement signals are used to generate INSTRUCTIONS. For flight controls, these displacement signals are used to generate COMMANDS. We are not obligated to obey instructions but are obligated to obey commands.

Now...There are two main popular methods using gyro/accel combinations for any sort of displacement data:

- Stabilized platform
- Strapdown

Inertial navigation system - Wikipedia, the free encyclopedia
Gimballed gyrostabilized platforms

Some systems place the linear accelerometers on a gimbaled gyrostabilized platform. The gimbals are a set of three rings, each with a pair of bearings initially at right angles. They let the platform twist about any rotational axis (or, rather, they let the platform keep the same orientation while the vehicle rotates around it). There are two gyroscopes (usually) on the platform.

Two gyroscopes are used to cancel gyroscopic precession, the tendency of a gyroscope to twist at right angles to an input force. By mounting a pair of gyroscopes (of the same rotational inertia and spinning at the same speed) at right angles the precessions are cancelled, and the platform will resist twisting.[citation needed]
This system allows a vehicle's roll, pitch, and yaw angles to be measured directly at the bearings of the gimbals. Relatively simple electronic circuits can be used to add up the linear accelerations, because the directions of the linear accelerometers do not change.

The big disadvantage of this scheme is that it uses many expensive precision mechanical parts. It also has moving parts that can wear out or jam, and is vulnerable to gimbal lock. The primary guidance system of the Apollo spacecraft used a three-axis gyrostabilized platform, feeding data to the Apollo Guidance Computer. Maneuvers had to be carefully planned to avoid gimbal lock.
What this mean is that the gyros and accelerometers are placed on a extremely high precision manufactured gimbaled platform and they control some motors. If there are displacements of any degree in any axis, the motors that are controlled by the gyros/accels will level the platform. The physical differences between the gimbaled platform and the frame that represent the body that produced those movements are recorded as electrical differences. Those signals then can be used for intertial navigation or for flight controls.

Strapdown systems

Lightweight digital computers permit the system to eliminate the gimbals, creating strapdown systems, so called because their sensors are simply strapped to the vehicle. This reduces the cost, eliminates gimbal lock, removes the need for some calibrations, and increases the reliability by eliminating some of the moving parts. Angular rate sensors called rate gyros measure how the angular velocity of the vehicle changes.

A strapdown system has a dynamic measurement range several hundred times that required by a gimbaled system. That is, it must integrate the vehicle's attitude changes in pitch, roll and yaw, as well as gross movements. Gimballed systems could usually do well with update rates of 50–60 Hz. However, strapdown systems normally update about 2000 Hz. The higher rate is needed to keep the maximum angular measurement within a practical range for real rate gyros: about 4 milliradians. Most rate gyros are now laser interferometers.

The data updating algorithms (direction cosines or quaternions) involved are too complex to be accurately performed except by digital electronics. However, digital computers are now so inexpensive and fast that rate gyro systems can now be practically used and mass-produced. The Apollo lunar module used a strapdown system in its backup Abort Guidance System (AGS).

Strapdown systems are nowadays commonly used in commercial and tactical applications (aircraft, missiles, etc.). However they are still not widespread in applications where superb accuracy is required (like submarine navigation or strategic ICBM guidance).
What this mean is that the gyros and accelerometers are literally bolted on to the body itself and the F-16 will illustrate this system...

flcs_f-16_components.jpg


The accelerometer assembly is pictured in the upper left corner. The three gyros are pictured in the middle right with the yellow tags. They are literally identical to each other in form and function. What make them 'pitch' or 'roll' or 'yaw' are their orientations and the above illustration has them correctly oriented as they are on the aircraft.

This is the 'strapdown' system. The gyros/accels units are literally bolted to the airframe and as the aircraft maneuvers in all three axes, the sensors move or 'displaced' with the aircraft and those movements are sent to the flight control computer (FLCC).

The interested readers should place attention on the highlighted wiki sourced paragraphs. The stabilized platform method offers the highest accuracy displacement movements, the costliest to manufacture, and more vulnerable to certain physical complications, mainly 'gimbal lock', which occurs at the extremes of maneuverings. The strapdown method is less accurate BUT considering the fact that the F-16 pioneered the fly-by-wire flight control system (FBW-FLCS) with this method, there is no credible reason to abandon it for flight control purposes. The Apollo vehicles used stabilized platforms as primary displacement data and strapdown as backup. What could be more effective an endorsement of quality than the Moon missions?

Does the submarine have maneuvers in the extremes? No. But a sub is literally blind most of the time and cannot afford to use its sonar all the time. Pre WW II subs were not truly submarines, they were more like surface boats that can submerge for short periods of time. For long distance journeys, they will be on the surface. Post WW II subs are truly submarines, by both their shapes and internal constructions. But because when submerged and cannot afford to use sonar all the time, they must have the highest possible body displacement sensors possible for them to guess their positions and the stabilized platform method is the best.

For the ICBM, does it maneuver at all during descent at double-digit Mach? No. Should it? That is a different issue. The reason why ICBMs require the highest possible body displacement sensors is because it is very much like the submarine in that it is quite blind for most of its journey. It is only recent that we began to install external sensors like radar and infrared upon the ballistic warhead in the final leg of its flight.

Getting back to the original question on which is more expensive to produce, the guidance for a ballistic or a cruise (normal) approach to a target. Or more specifically, whose guidance MUST be more sophisticated to accomplish the same mission: Hit a moving target. The DF-21D or the Brahmos?

The Brahmos flight manner can be compared to the F-16's and the F-16 has been performing just fine these decades with the less precise and less accurate strapdown method for flight controls, that the F-16 set the standards for FBW-FLCS for later aircrafts, and that the American missiles Tomahawk, Phoenix, and Harpoon uses the strapdown method just fine these decades as well, so why should the Brahmos take the more expensive path using stabilized platform for either navigation or FLCS?

IEEE Xplore - GPS/INS integration on the Standoff Land Attack Missile (SLAM)
The unique SLAM GPS/INS avionics configuration integrates the existing Harpoon midcourse guidance unit, which includes a strapdown inertial sensor package and digital processor,...

With the DF-21D, its nuclear armed brethens already demand the highest possible highest data integrity, now its non-nuclear mission demand 100% physical hit success on any target the DF-21D will demand no less accuracy and precision. Nosecone physical limitations for the ICBM does not afford distinct gyros/accels system like the F-16 for navigation and flight controls, making the demand for the highest possible quality gyros/accels signals more important. The stabilized platform fits the bill.

U.S. NATIONAL SECURITY AND THE PEOPLE'S REPUBLIC OF CHINA -- CHAPTER 4
The Long March 2 guidance system is also a three-axis stabilized platform, whereas the Long March 3B is a four-axis stabilized platform.

The DF series served as boosters for the Long March vehicles. We do not know the exact technical details of these adaptations but there are no reasons to dismiss the possibility that the entire system was used.

So until we know more information and I am willing to be corrected, my opinion: The DF-21D will cost more to test and produce.
 
Gambit..
There have been some alternatives to mechanical gyro's.. especially in the fibre optic kind but have lacked precision.
If we can assume that it may be possible that a Chinese manufacturer has achieved accuracy on a FOG that is close to ( perhaps even copied from) a particular FOG manufactured in czarland.. and due to the way the Chinese procurement system operates the economy of scale for the system is more favorable than ..say one manufactured elsewhere..the cost factor has come down.

As another example..
A certain TI TMS320C6000 series costs around $295 .. till early 2010 this was the cost..still is if you buy TI genuine.
apparently.. after that.. some people near the Chengdu area got their hands on complete "fabrication" of this product.
Some of those test "facsimiles" went here and there.. they cost around $50 a pop..

They arent sold anywhere international yet, except to some cellphone manufactures.. and some to interested companies.
They do all that the TI Chips do..and cost 1/5th.

here is the catch.. 1 out of 5 "facsimile" chips have problems.. some wont have pins.. others wont work properly..some are bent.. and some dont work at all.
They heat up faster than the TI originals..

But newer lots keep coming in with less and less faults.
So if we take this as an example of sheer mass "facsimile" ability and gradual learning from mistakes.
It is possible.. not certain.. possible.. that eventually; while a BM system will still be more expensive to manufacture for the Chinese than a CM.. it may not be that much more expensive than one for a CM made by another nation.

Which brings us to what does the guidance system control?
The DF-21D has been designed from the outset to kill ships.
Keeping that in mind, if I was project head.. Id keep post-reentry maneuverability a high priority..
But that is if I was the head.. there is no proof ..pictorial or otherwise to suggest that the actual project head has done the same.
And the sheer workmanship(if done properly) for a BM more expensive than a CM..
however.. I wonder if the hypersonic capability adds much to the cost of a Brahmos compared to say a tomahawk.
 
Way too big to carry be carried internally. As it is, it takes a beast like the modified Su-30MKI to carry it externally (afaik, the Su-30MKI will be the only fighter aircraft in the world capable of carrying such a cruise missile).

The combined weapon bay (i.e. both forward and behind one) can carry a missile of the size of brahmos... besides the air launched version would be smaller and more compact with lesser fuel needed since the supersonic speed of a PAK FA would provide it with necessary initial boost.
 

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