It would be great if you could Please clarify
Mass of rocket or Mass of propellant?
if mass of propellant, in a ramjet, is the mass of oxidiser, i.e air accounted? In a rocket the propellant part includes both fuel and oxidiser.
Mass of rocket or Mass of propellant?
if mass of propellant, in a ramjet, is the mass of oxidiser, i.e air accounted? In a rocket the propellant part includes both fuel and oxidiser.
Ahh........never mind them. Those equations are basically old people grumbling. Firstly they are meant for liquid/solid rockets and not air-breathing engines and secondly they are all ideal cases. In practice they are used as a reference, nothing more.
If you want of go into boring old rocket physics equations there are two basic ones :
First is the Newtonian equation, the one I wrote down. The mass here can be mass flow rate shooting outside the nozzle or it can be overall mass of the rocket(propellant, electronics etc all included). It really doesn't matter much in this case. If you look at the equation, we have thrust on one side. Thrust as we know is a force, force = mass X acceleration. Now you have a mass on both sides of the equation, which cancel out. Whether mass flow rate or overall mass is considered it really doesn't matter. You have to keep in mind the nuances like : when the rocket is operating mass flow rate considered to be a negative gradient, since propellant mass is being lost.
The second equation is the Tsiolkovsky rocket equation which deals with delta v. We don't know the exact velocity here so it can't be used.
If you are wondering what is the physical significance of the mass cancelling out its this : The propellant load of the rocket has no impact on the efficiency of the engine.
We have seen a practical demonstration of this very recently. Remember the CY-2 launch where the cryo upper stage carried 28 tons of propellant instead of 25 tons ? That had negligible impact on the CE-20 engine's efficiency. Sure there are problems with sudden increase in propellant load like increasing the duration of burn might cause material failure. But as long as the increase and decrease is kept with in reasonable limits it should be okay.
But like I said these things don't apply for air breathing highly maneuvering missiles. So never mind.
This is a good graphic to keep in mind :
The SFDR is stated to have a Isp of 1000-1200 sec and it is a ramjet powered missile, that's very much possible. It was tested in 2018 at speeds exceeding mach 3. Again the exact figure of speed was never released. But one article written by a Other Forum. poster seems very accurate with the range figures released today. This was his prediction :
He based his prediction on the discharge time of the battery :
"The cutting-edge Lithium Thermal Battery of SFDR. DRDO’s SFDR Missile under development incorporates a state-of-the-art Lithium Thermal Battery weighing just 1.4kg which powers up the entire sub-systems of SFDR during its entire flight. The shelf life of Lithium Thermal Battery is highest amongst any kind of battery made in the world so far, with atleast 25 years of shelf life, which will help in lesser maintenance of this missile. The most notable thing in this Lithium Thermal Battery is its discharge duration requirement of minimum 230 seconds. The battery only gets activated when the missile is launched and its discharge time straightly points towards flight time of approx. 230 seconds."
DRDO’S precious ‘Project SFDR’: Connecting the Dots
Thrust = (Mass of rocket X Specific Impulse X acceleration due to gravity)
MLT(^-2) = M*T*(L / (T*T)) ? i.e MLT^(-2) != MLT^(-1)
Just a nitpick though
MLT(^-2) = M*T*(L / (T*T)) ? i.e MLT^(-2) != MLT^(-1)
Just a nitpick though
Basing flight time on just the battery, implies the entire missile is built around the constraints of the battery.. Why not connect two of these batteries in parallel and have longer flight time..
That is a perfectly correct equation. Just one little problem. You are assuming the dimensions on both sides to be equal. If that were the case, the unit of efficiency of a rocket engine would be, like all other engines in the world, dimensionless.
But that isn't the case is it ?
Most efficiencies that we calculate and formulate in the world are to measure how much energy was converted from one form to the other, in rocket sciences none of that matters. Its all about how much fuel you need to carry a given payload assuming the engine has a given Isp.
Needless to say this is a weird premise and it leads to some pretty outlandish assumptions. For example the "g" is always assumed to be 9.81 m/s2, irrespective of where the rocket is. You could argue that gravity reduces as you get far away from earth but the equations will always take acceleration due to gravity as 9.81. Doesn't matter if the rocket is sitting next to the Sun where the gravity is 1000 times higher, it always going to be 9.81. Seems unreasonable doesn't it ?
This whole equation is just a weird but internationally accepted assumption. Just like how we all agree that a given length is 1 meter, a given duration is 1 sec and so on. We need these assumptions to base our calculations on.
Isp is measure in seconds because no matter what system(SI, mks,fps etc) you follow, time is always in seconds. It was internationally accepted to be the standard in the 1950s and 60s, largely because the German scientists working with Americans in NASA used the metric system and the Americans used the imperial system. This caused all kinds of problems.
All these assumptions ensures pretty inaccurate outcomes, sometimes ridiculously funny. For example you can use the delta-v equation to find the speed of a rocket, however the result will be always wrong. The actual speed will be lower than the calculated figure. Back a long time ago scientists use to use these results as a reference, nowadays nobody does that.
There are constraints of space, weight etc for every missile, especially air to air missiles. Adding another battery consumes internal space which has to be compensated by reducing fuel load. This will reduce range and speed of the missile. That not an option here.
What can be done is that we make better propulsion systems and more efficient batteries in the future.
Work is already ongoing in the batteries department, we are making some very efficient zinc batteries for our upcoming heavyweight electric torpedoes.
On the propulsion front we might have hit a plateau. Boron based fuel, used by SFDR, are the most powerful among all solid fuels(google zip fuel) and any advancement in speed and range will require either making larger missiles or some breakthrough in scramjet engines.
For now let's just worry about making this thing operational first.
X band seeker trialed at sea against a sea based target. Note that SCI Saraswati is a small tug boat.
Interesting. It seems we are making a naval missile that requires high precision scanning, tracking, discrimination and targeting ability.
Which missile ? NASM-SR ?
Barak 8 without extended range booster has a diameter of 225cm, while the Desi Meteor will be 200mm or less.
Strictly speaking a Brahmos type VLS can be used to hold as many as 4 of these missiles without a heavy booster. With a Type 052D style 64 cell UVLS, we can easily carry 16 Brahmos, 16 Nirbhay, 8 ASROC class missiles, 32 Desi Meteors without booster and 16 Desi Meteors with boosters. This practically gives us AB class firepower on a Kolkata class vessel. Also, instead of 4 CIWS, we can have just 2. And the other 2 can be replaced with 2x8 cell Desi Meteor launchers as well, like we have done with Barak 1.
Depending on the size of the booster, the range can be increase to well beyond 400Km.
But are the specifications of SFDR like length, weight, wing/fin span and diameter for ground launched and air launched versions.
SFDR with the booster is 200 mm ? Are you certain of that ? If so that is a great deal of firepower enhancement coming our way.
As a thought exercise let's assume we are going to turn the Brahmos VLS into the UVLS. The Brahmos is the largest diameter missile the Navy uses from its ships excluding the Dhanush missile(that one doesn't count), so it is very likely that the current or the future iteration of the Brahmos VLS is going to be the UVLS.
I understand you can carry multiple missiles in a single VLS, but how do you fire them ? If they are hot launched, shouldn't the flames from one missile damage the forward section of the other missiles ?
Can the MF-STAR acquire targets beyond 400 km ? If not how do we engage targets that far ? co-operative engagement ?
And about the SMART. Do you think that the Lightweight Torpedo Shyena having a range of only 7 km will be a problem in the terminal phase of SMART ? All contemporary light torpedoes have a range ~10 km, although the SMART with its 65 km range should make up for it.
All that's unknown. But logic dictates the A2A version should have a length of 4m and a diameter of 200mm, or 3.6m and 175-200mm at worst, like most standard AAMs are.
And the ground based version can very well be the same dimensions as the A2A version. They can probably make it slightly longer to accomodate a bigger warhead. But with this version, you can remove the range extension booster or change the size of the booster to get the range you need. So there is no need to change the dimensions of the missile itself, only the booster needs to be changed for different ranges. Like the case with SPYDER-SR and SPYDER-MR or Barak 8 and Barak 8ER.
The A2A version can also be designed with a range extension booster. The current booster under testing is only used to take the A2A version to altitude for testing purposes.
I am just assuming the Desi Meteor is 200mm, because anything fatter will be a problem for A2A needs.
In the picture of the missile, you can see two boosters. One is outside the missile, it's meant to carry the missile to a desired altitude. And the other booster is inside the missile, which is the nozzle-less booster. This will take the missile to the desired speed before the ramjet kicks in.
The external booster is fatter than the missile itself. So if the missile is 200mm, then the booster could very well be 300mm or more, possibly 400-500mm. That's why I put 4 missiles in one VLS for the one without the booster, and just 1 missile in one VLS for a missile with the range extension booster. The one without the booster, you can possibly get a range of 150Km, and the one with booster can be 200 or 300 or 400Km, depending on the size of booster used.
The UVLS may be the same, but the canisters inside have to be specifically designed for the missile itself. So the Brahmos canister will be completely different from the Desi Meteor canister, and so on.
This is the MK25 canister for the ESSM on the Mk41 VLS.
As you can see, the canister is specifically designed for the missile. So you can design your own ventilition system for each missile. And the lids protect the other missiles.
The MF-STAR's range exceeds 400Km against fighter jet sized targets. It won't have any problems against aerodynamic targets 600Km away even.
CEC is particularly useful against sea-skimming targets, since the range of the MF-STAR depends on the height of the mast, which is considerably less than 40Km. But of course aircraft based targeting is the most useful capability since you are potentially much closer to the target than the ship is.
Shyena is fine for SMART. The SMART's job is to take the torpedo as close as possible to the target, so you don't need a lot of range for the torpedo itself. But we most definitely need a faster torpedo, particularly against nuclear subs. Perhaps a Shyena Mk2.
Bit too early for that. Its still an experimental missile and we don't know a lot about it. The seeker for example has a crucial role in determination of NEZ, so does the speed, acceleration, g-tolerance limits, operating altitudes etc. There are too many variables as of now to make any reasonably accurate estimate.
But there are a few things we know for sure. A ramjet engine powered by a boron based sustainer is like the best of both worlds. Ramjets are known for high terminal velocities, boron based fuels are known to produce ridiculous amounts of energy resulting in rapid acceleration. It can also propel a missile the size of the SFDR at speeds over Mach 4.5, that is assuming the launch vehicle is at rest. There are problems with boron though, it is highly volatile and will catch fire instantly when in contact with air. Boron requires some kind of chemical stabilisation to become usable as a rocket fuel. Given that we are already flying it, those problems have been dealt with.
DRDO has experience with AAMs now with the Astra maturing and it has acquired significant knowledge in making air frames that are tolerant to very high levels of g-forces. No reason why they cant make another one.
That leaves us with the seeker. All we have to do it take the Astra's Ku band seeker and put it on the SFDR and we will easily have a NEZ in triple digits. The NEZ of the SFDR would be more than the maximum range of the Astra MK-1. Ku band is a pain for electronic jammers.
There is of course other critical things like this :
A 2 way data link greatly enhances the probability of kill. It will be a standard for any radar guided future AAMs that we make. LR-SAM/MR-SAM already has it. Astra Mk-2 will have it too.
There are some internal communications of DRDO, LDRE and RCI that fleetingly mentions the presence or development of a X-band AESA seeker. Now if this is true it would be revolutionary. With an AESA seeker nearly 2/3rd of the maximum range of the missile would be the NEZ. But that's still unsubstantiated, I've not seen any research papers/ journals on it yet.
So lets just wait. Any way it turns up the SFDR will be one hell of a missile when it comes.
Thanks for the wonderful information. With 330 range even if half of it is NEZ we will be covering half of Pakistani territory. Then we should take panga with them n shoot down some of there f solas
Enforcing an A2/AD strategy by the use of fighters armed with long range missiles is inefficient. For that you need static long range air defence solutions, however aircraft with long range missiles will be needed to fill the gaps. That's where the S400 and the Rafale+MBDA Meteor comes in.
We will have similar, if not better, systems of our own in the future with the XR-SAM and Su-30MKI+SFDR. However they will still need time. The Su-30MKI upgrade has been in a limbo for a while now and no signs of getting on track. The XR-SAM and the SFDR based long range AAM will depend on the success of the SFDR project, for all its greatness its still a tech demonstrator. So let's not count our chickens yet.
While our systems come around, the S400 and Rafale will give us the hardware at hand to formulate tactics and exercise along those lines.
We cannot use S 400 on 24 / 7 basis
Otherwise the Radars will loose their Operational Life
That is why More MiG 29s and Tejas with
Derby are needed
I know and that's what I meant by plugging the gaps of AD with fighters armed with long range missiles. I used Rafale+Meteor as an example. Of course all other fighters will do their bit too.
Remember this ?
The navy had the vintage Russian rocket RGB-60 with a maximum range of 5.3km to fire from the RBU-6000 ASW rocket launcher. They wanted more range so the ARDE-HEMRL jointly built the ER-ASR(shown below) with a range of 8.5 km. The ER-ASR used the same airframe as that of the RGB-60 as it was also meant to be fired from the RBU-6000. The only changes were engine, fuel and thus thrust output.
It seems the increase in range often brings its own problems. The rocket when test fired was consistently missing the target. Remember its a non-guided rocket. So if it is flying off target, the reason isn't guidance failure, but design of the rocket. But the airframe of the rocket is the same as that of the RGB-60 which has worked well all these years. How would there be any problems with the airframe ?The inaccuracy as it turns out was due to increase in range. Well as ARDE put it :
Fascinating isn't it ? In the end all they had to do is slightly change the tail fins, the change was so small that it isn't even visible. That solved the problem.
Aerodynamics is a lovely subject, assuming you know what to do. Its not that lovely otherwise though.
The navy had the vintage Russian rocket RGB-60 with a maximum range of 5.3km to fire from the RBU-6000 ASW rocket launcher. They wanted more range so the ARDE-HEMRL jointly built the ER-ASR(shown below) with a range of 8.5 km. The ER-ASR used the same airframe as that of the RGB-60 as it was also meant to be fired from the RBU-6000. The only changes were engine, fuel and thus thrust output.
It seems the increase in range often brings its own problems. The rocket when test fired was consistently missing the target. Remember its a non-guided rocket. So if it is flying off target, the reason isn't guidance failure, but design of the rocket. But the airframe of the rocket is the same as that of the RGB-60 which has worked well all these years. How would there be any problems with the airframe ?The inaccuracy as it turns out was due to increase in range. Well as ARDE put it :
Fascinating isn't it ? In the end all they had to do is slightly change the tail fins, the change was so small that it isn't even visible. That solved the problem.
Aerodynamics is a lovely subject, assuming you know what to do. Its not that lovely otherwise though.