Akash and its nuclear payload

Arun_S · Post by **Arun_S** » 06 Jul 2000 11:00

<A HREF="http://rediff.com/news/2000/jul/05akash.htm" TARGET=_blank>http://rediff.com/news/2000/jul/05akash.htm</A> Initially I though this news was another misreporting/ignorence by news media, but after listening to AIR news (on Real Audio), I give some credence to it, which raises some questions:1. 55Kg payload: Does it mean that one or more of the Sub-kilo ton nuke testes were compact N-weapons design ? It is well known that during the cold war the western forces had tactical N-weapons to be fired as artillary shells, whose weight was less than 55 Kg in question. This news coming from GOI is not from thin air.2. The use of Nuke-tipped Akash: I can only think of its only use in ABM role (it is of same class as Patriot) to defend high value assets & establishment from TSP & China.100 Ton explosive yield and associated EMI gives good assurance against the other wise difficult task of defending against N-tipped ballistic missile. It's certainly better than being hit by 20 Kt nuke.IIRC I did hear about indigineous S300 with Akash as a component.What do you think ?[This message has been edited by Arun_S (edited 06-07-2000).]

Cybaru · Post by **Cybaru** » 06 Jul 2000 11:15

Ah small point .. the range at max is 25 kms .. I don't think i wanna hang around to press the trigger for a nuclear tipped akash.. 15.5 Nm miles ?? Hell it would cause enough EMI to take my systems offline too.. Or am i missing something here ??

shiv · Post by **shiv** » 06 Jul 2000 12:07

This is garbage reporting - I was going to post it as a humor news item but you beat me to it. There is another funny photo in the news however - a "Trishul Tanker" - whatever that means - TOI Bangalore 6th July. Sorry about the poor scan quality - handheld hurried scan at 160V and 37Hz mains voltage. <A HREF="http://personal.vsnl.com/cybersurgeon/tritank.jpg" TARGET=_blank>http://personal.vsnl.com/cybersurgeon/tritank.jpg</A> Ques: What effect does a 0.1 kT airburst at ~20km altitude have on the ground?Ans: A bright flash of light that enables you to find your matchbox during the power cut[This message has been edited by shiv (edited 06-07-2000).]

Cybaru · Post by **Cybaru** » 06 Jul 2000 12:30

OH boy.. its carrying more people than missiles..

geeth · Post by **geeth** » 06 Jul 2000 18:32

>> What effect does a 0.1 kT airburst at ~20km altitude have on the ground? Assuming of course that the incoming warhead is completely neutralised.That is the altitude where a/cs like Mig 25, SR-71 et al flies. All the Nuclear debris will fall back to earth (India). You may say it is still better than the incoming warhead exploding. There is also a chance that the "Nuclear" Akash targets a non-nuclear warhead/target. IMO we should think of better solutions. Controlling the issue of Nuclear debis will be too problematic politically, militarily and technically.I think it is a case of wrong reporting.

Gerard · Post by **Gerard** » 06 Jul 2000 18:44

> Initially I though this news was another > misreporting/ignorence by news mediaI think your initial impression was correct. The PTI release has the same nonsense about the missile being able to "hit several targets simultaneously".

Aditya Vikram · Post by **Aditya Vikram** » 06 Jul 2000 18:51

Arun S, Could India try to a nuclear tipped akash as an answer to the PLAAF in case it decides to adopt a wolfpack strategy with its 3000 J-6's???

Calvin · Post by **Calvin** » 06 Jul 2000 19:00

What is the smallest size a nuclear weapon could be?IIRC, the critical mass for such a weapon is in the neighbourhood of 10 kg of Plutonium. (IOW, you don't need the temp/pr of conventional explosives to set it off). Based on this, the smallest nuclear weapons that are believed to have been made are around 30 kg in weight (add in casing, shielding etc).This means that with a 55 kg warhead, Akash could certainly carry a nuke warhead, although its utility is somewhat dubious. It is even more dubious given the declared doctrine of the nation.

Kuttan · Post by **Kuttan** » 06 Jul 2000 19:17

Disinformation or not, this has excellent potential for increasing Maalox sales. 1) Is there any reason why an air-breathing SAM like the Akash cannot be modified to become a short-range tactical nuke missile? Air-burst at 2000 meters above a tank formation, 25 km inside TSP...I've always wondered why the Akash had the complexity of an airbreathing stage. 2) If I saw a flight of, say, 5 F-16s coming in, I would not hesitate to use a nuke-tipped SAM at 25 km range. Yes, my life expectancy might be rather reduced, but that of 5 million others might be increased. I wonder very much whether TSP's F-16s have electronics which will withstand a nuclear EMP. 3) Hit multiple targets? Well, with a nuke warhead, that/s not so far-fetched. Also, after a hit, a TSP F-16 will become multiple objects. Otherwise, of course, its India Today - quality of reporting. I suppose it will hit one target, then get up and reconstitute itself like MGR in "Aayirathil Oruvan" (translation: one missile against 1,000 targets

) , and move on to the next one..or maybe it carries 10 independent air-launched AA missiles inside its nose-cone, to be launched after reaching 30,000 feet and Mach 2. BTW, why does an SAM site need to track 64 simultaneous targets? They're doing good if they can track, lock on, and kill one target. Once an SAM is launched, you don't usually tell it to turn around and go after another target, do you?Anyway, we do hope the TSP aces who shoot down 10,000 IAF aircraft with each machine-gun bullet are reading this. Yes, indeed. Now TSP has to go to General Li and beg for 10,000 F-7s, plus SAMs which use ramjet engines for the FIRST stage (from zero velocity, that is

) to be "India + 1". [This message has been edited by narayanan (edited 06-07-2000).]

Nikhil Shah · Post by **Nikhil Shah** » 06 Jul 2000 19:24

<BLOCKQUOTE>quote:<HR>Originally posted by Gerard R Thomas: > The PTI release has the same nonsense about the missile being able to "hit several targets simultaneously".<HR></BLOCKQUOTE>That is not nonsense! When they say missile, they mean the complete system. Multiple missiles fired. My gues is 4 at a time. That is what is meant by multi-target elimination.

Vick · Post by **Vick** » 06 Jul 2000 20:29

multiple targets can also mean that the warhead (conventional) is a proximity fragmentation warhead. if there are multiple targets within the blast radius, then it would be engaging and killing multiple targets. that's my logic anyways but its been proven that DRDO works on a completely different logic (not necessarily bad).

Amitabh · Post by **Amitabh** » 06 Jul 2000 21:07

<BLOCKQUOTE>quote:<HR>I've always wondered why the Akash had the complexity of an airbreathing stage.<HR></BLOCKQUOTE>That's because the missile is derived from the Russian SA-6, which has airbreathing propulsion. The Trishul is similarly derived from the SA-8. <BLOCKQUOTE>quote:<HR>BTW, why does an SAM site need to track 64 simultaneous targets? They're doing good if they can track, lock on, and kill one target. Once an SAM is launched, you don't usually tell it to turn around and go after another target, do you?<HR></BLOCKQUOTE>A SAM radar controls more than one missile. Each launcher has three missiles. One Rajendra radar typically controls three or more launchers. Tracking 64 targets allows you to prioritize them and launch missiles at the 9-12 most important ones within your range. It also allows you to feed data to other launchers in the ADGES network.

Arun_S · Post by **Arun_S** » 06 Jul 2000 23:54

>> The PTI release has the same nonsense about the missile being able to "hit several targets simultaneously".Not nonsense. Akash is designed exactly for this capability too. I.e. One missile engaging mutiple aircrafs in tight wolfpack formation. >> Could India try to a nuclear tipped akash as an answer to the PLAAF in case it decides to adopt a wolfpack strategy with its 3000 J-6's???Use of sub-KT nuke for SAM has serious repercussions: 1. Radioactivity contamination. 2. Possible collateral damage. 3. "First Use" of nuke : however small.If Nuclear deterrance breaks then use of Nuke tipped SAM is a last resort to thwart Nuke attack on Indian soil, by ballistic missile or bombers. So IMHO it use against PAL woulfpack would only be relavent in case of nuke attack. >>1) Is there any reason why an air-breathing SAM like the Akash cannot be modified to become a short-range tactical nuke missile? Air-burst at 2000 meters above a tank formation, 25 km inside TSP... You mean 0.3 KT nuke in 55 Kg package at 2 Km altitude ? Unlikely to be effective against tank ! Technically possible but there are other issues. See above.>> I've always wondered why the Akash had the complexity of an airbreathing stage. Two reasons: 1. Doesnot have to carry the weight of oxidizer. Thus has faster acceleration and greater range. 2. Lesser weight and compact space. So can carry more missiles on the BMP. >>BTW, why does an SAM site need to track 64 simultaneous targets? If you can track 64 you will not get confused and hit the 3 assignes aircrafts while the other missile takes care its share of 3 targets and so on.... (robust target tracking + no confusion + allows missile to react to targets evasive and ECM response).>>I read in a asian neswpaper in the UK, the world, that the Akash warhead splits into three and using just kinetic energy of the initial thrust, go after three seperate targets in the same vicinity. However I think that is nonsense.But that is True. Kinetic energy is used to get close to the independent targets (not to kill it), it still uses Hi-Explosive to blast the target. Each warhead has independant terminal seeker and control.Cheers

Vick · Post by **Vick** » 07 Jul 2000 00:00

another SAM that splits up and attacks multiple targets is the irish? starstreak[This message has been edited by Vick (edited 06-07-2000).]

Div · Post by **Div** » 07 Jul 2000 09:39

Was it the Sa-5 that was stationed around Moscow with nuke warheads, meant to destroy incoming ICBMs?

vverma · Post by **vverma** » 07 Jul 2000 10:10

A warhead this small can certainly be designed, France has one to fit the ASMP but France's nuclear infrastructure was much wider. They conducted more tests, etc. I just don't see this being true unless India was able to negotiate for nuclear data from France, Israel, etc. [This message has been edited by vverma (edited 06-07-2000).]

Arun_S · Post by **Arun_S** » 07 Jul 2000 10:23

Is there any evidance you speak from regarding the size / weight of sub-kilo ton tests done during Shakti, to assert that India has to get the design from French ?

Arun_S · Post by **Arun_S** » 08 Jul 2000 08:42

Indian Nuke doctrine would certainly be influenced by US NMD decision, and Nuke tipped Akash would become relavent.If US does deploy a National MIssile Defence, there would be immediate need in India & China to defend against US nuke black mail, while they rampup to increase their ICBM stocks to new deterrence level (~1000) to overcome the NMD threshold. NMD would be deterrent wildcard for long. Countermesaures to NMD target discrimination would certainly take many years and it would follow the cat & mouse game earlier seen in ECM, ECCM & ECCCM etc. Point defence systems like S300 may provide cover against SRBM and not ICBM's. IMHO Nuke tipped SAM's would be the first level reponsse to such a US move, for they immediately increase the effectiveness of systems like S300 against ICBM attacks.

Guest · Post by **Guest** » 08 Jul 2000 20:47

Could this be about making the Akash an air-launched nuke tipped ground attack missile. Can the Akash be converted into such a missile. If it is air-launched its range will increase a lot, perhaps 50 plus KM. It might be too big to carry aboard a Mig, but perhaps the big Sukhois could have one slung underneath. Or, who knows, we might put two or four underneath a Boeing 737 and use it to attack Karachi from a distance.Just guesses, a nuclear warhead would usually be for the ground. A missile is a missile. You should be able to launch it from anywhere, point it in the right direction, and shoot it off.

Gerard · Post by **Gerard** » 08 Jul 2000 21:37

<A HREF="http://news.excite.com/news/r/000708/07 ... ia-missile" TARGET=_blank>http://news.excite.com/news/r/000708/07 ... missile</A> NEW DELHI, July 8 (Reuters) - India tested its short-range Akash surface-to-air missile on saturday for the second time in a week, the Press Trust of India (PTI) said

Raj Malhotra · Post by **Raj Malhotra** » 09 Jul 2000 00:44

I think we should not be very quick to discard the concept of Akash being used in G to G role with nuclear warhead. In another thread posted elsewhere on this forum I had pointed out that USA had in 1958 tested a three stage thermonuclear device weighing 67 kgs with yield of 65 kt. The device had a primary of .26 kt. One must not forget that India conducted a series of subkt tests and the thermonuclear test with claimed yield of 45kt was termed very successful. In this backgroung me think use of a small thermonuclear device which will be more powerful than any pure fusion device is a very real possibility. I remember reading somewhere that there was proposal to increase Akash range to 60 km in G to A format. It would be interesting to calculate what would be the range in G to G format if this 60 km range Akash is used. (Somebody may kindly oblige.)

Arun_S · Post by **Arun_S** » 09 Jul 2000 01:14

When I read the specs: "The missile has a range of 27 km, with an effective ceiling of 15 km", I read it to mean that Akash can kill a target flying as high as 15 Km at a range significantly lesser than 27 Km, and that it can kill ataget as far as 27 Km at an altitude significantly lesser than 15 Km.It does not mean it can kill a target 27 Km away AND flying at 15Km altitude. [This message has been edited by Arun_S (edited 08-07-2000).]

Arun_S · Post by **Arun_S** » 09 Jul 2000 01:28

>>This is regarding your EMP-related comments....for EMP to be generated, the detonation needs to have necessarily occurred at a high altitude...around 35-40 km...Please sustantiate your claim.We are talking about EMP due to Nuke exposition, which is strong enough to pulverize Nuke's EMP resistant electronics (used for triggering and safety interlocks). My guess is that for 0.3 KT fission the distructive EMP radius would be around 150 meters.

Kuttan · Post by **Kuttan** » 09 Jul 2000 01:28

<BLOCKQUOTE>quote:<HR>You mean 0.3 KT nuke in 55 Kg package at 2 Km altitude ? Unlikely to be effective against tank ! <HR></BLOCKQUOTE>Not to argue with experts, but I find this a little hard to believe. If I am not mistaken, the Hiroshima bomb exploded at 5000 feet, and several people walking along a bridge were vaporized; they cast shadows on the bridge where the material of the bridge wall (stone/concrete?) was affected less. I don't think I want to be in a tank when a nuke missile of any size goes off in the clear air 6000 feet above me. Some of the metal of the tank may survive, but at minimum: a) the people in the tanks will be dead b) all gun-control and probably the propulsion will be dead c) the fuel tank will probably explode d) the tank will travel some distance through the air in the blast wave. Thanks for the info on why people use airbreathing propulsion. My question is why a missile designer would choose a complicated system where there is a rocket to start, then transitioning into a ramjet. This "hybrid" engine is thus far more complicated and hence expensive to build. Ramjets have problems like inlet instability, combustion instability etc., which affect how sharp a maneuver can be executed. So if I were designing a pure SAM, I doubt if I would go to the trouble of an airbreathing engine. I could probably afford 3 times as many pure solid-rocket missiles for the cost of one of these. No inlet needed; and solid fuel is pretty cheap. But if I wanted to control and modulate the thrust, and vary the flight profile greatly, and get a lot of cruising range, then the added complexity and cost would be worth it. The idea of a versatile missile which can be converted for ground-to-ground missions may not be as far-fetched as the experts here might claim. Just a few random thoughts..

Kuttan · Post by **Kuttan** » 09 Jul 2000 02:23

Thanks. Very interesting link. I didn't know one could find such things in the open internet. True, it appears that if one sets out to send an EMP, its pretty hard to damage India without also doing similar damage to TSP. Or vice versa. OTOH, Uncle or General Li could easily send up something to explode a couple of hundred km above South Asia, and pffffft! no more air defenses, no more computer industry, telephones, etc. Kerala State Road Transport will still operate because they keep the exposed ends of the wires from the battery and ignition system straight under the dashboard, and the driver does the switcing by clicking the ends together.

vram · Post by **vram** » 09 Jul 2000 02:49

<BLOCKQUOTE>quote:<HR> The area of the Earth's surface directly illuminated by EMP is determined entirely by the height of burst. All points on the Earth's surface within the horizon, as seen from the burst point, will experience EMP effects as depicted in figure 2, which is on page 3 of your handout. Note that a burst on the order of 500 kilometers in altitude can cover the entire continental United States. Mr. WELDON. What strength burst would that be? Dr. SMITH. It is not terribly burst-strength dependent; almost any burst will produce that kind of radiation. The strength of the field will change at the various radii from the burst point, but it will cover the same area regardless of the strength of the burst.<HR></BLOCKQUOTE>Any power that wants to take on the US, this is the most cost effective way of doing it. US is a hi-tech fighting machine, but it makes them that much more vulnerable to EMP-- it will bring the war fighting machine to a grinding halt.In fact, if ever India is confronted with a carrier fleet heading towards the Bay of Bengal (a la 1971) a high-latitude burst should really degrade the US fighting capabilities. Yes, it will affect India too, but it is the US that is much more reliant on sattelites, and electronic warfare...

rama · Post by **rama** » 09 Jul 2000 03:00

Arun_S, Narayanan,What are your thoughts on eventually deriving an airlaunched standoff weapon from the ramjet propulsion of Akash (something like an ASMP). For a standoff weapon, conventional turbojet cruise missiles offer good range x payload for a given weight limit (say 1000 kgs or less) to make it usable with a Mirage2000 or similar aircraft, but too slow and hence vulnerable to interception. I dont know enough about rocket motors to comment on rangexpayload, but unless we want messy liquid fueled devices maneouvering to a low CEP might be a problem.A ramjet, it seems to a non-aero person, would offer a good compromise in propulsion for such standoff weapons, and a surface-to-surface testing of Akash a logical first step in that direction. India's aircraft delivery part of the triad would have to move beyond gravity bombs at some point of time.Akash right now is ~700kgs, of which the first stage rocket motor may be unnecesary for airlaunch from a supersonic/transonic platform (is this correct?), and so its warhead weight may be marginally increased in the standoff confiiguration?

Arun_S · Post by **Arun_S** » 09 Jul 2000 03:33

By no means am I a bomb expert, leave alone Nukes. I was just imagining if I am in a T72 tank and 12 car freight train loaded with 300 Ton TNT explodes 2 km away ( at say 45 degree elevation) would really disable me or my tank ? I was relating it to my experience of watching 24 x 2000 Lb bombs expode 1.5 Km away. Of course it is not a like like watching one 24 T bomb but it is a degree of magnitude. >>My question is why a missile designer would choose a complicated system where there is a rocket to start, then transitioning into a ramjetExcept short range SAM's, all medium or long range missiles are staged to realize very fast acceleration. Ram-jet or not, one would have the complication of multi-staging. Medium range SAM's need to be short reactioned and anything to maximize acceleration to target is worth the complications of Ram-jet. [This message has been edited by Arun_S (edited 08-07-2000).]

Arun_S · Post by **Arun_S** » 09 Jul 2000 04:38

For the given missile weight, maximum range is achived with sub-sonic flight (aka cruise missile). Supersonic fights are always very inefficient, thus tend to be very bulky or short ranged. Sure for supersonic missiles Ramjet is very appealing due to reduced weight of oxidizer. Converting Akash for A-S role requires India developing expertize in minaturized terminal guidence for surface targets, which is more difficult than an airborn target.Standoff weapon for static surface targets is more of navigation & guidence challange rather then flight control challenge (control fins are adequate). Moving targets on surface is more problamatic.[This message has been edited by Arun_S (edited 08-07-2000).]

shiv · Post by **shiv** » 09 Jul 2000 06:46

OK OK folks. If you keep telling me that TSPAF is the best - I will eventually start believing it.So EVERYONE, including that news item about the second test says "nuclear and conventional payload"If there were a 0.2 kT warhead - I think it would be no use as an ASM. I suppose it could have some meaning as an ABM - a someone pointed out. With a 0.2 kT nuke - a "near miss" could be 100-200 metres and still take out an incoming missile.In other words - I think it makes far more sense to develop some degree of ABM defences than make yet another ASM.

Kuttan · Post by **Kuttan** » 09 Jul 2000 08:25

<BLOCKQUOTE>quote:<HR>Except short range SAM's, all medium or long range missiles are staged to realize very fast acceleration.<HR></BLOCKQUOTE>I'm a bit confused: I thought the shortest-range SAMs, or ABMs, need fast acceleration the most. The time available to dilly-dally around is far too short for anything else. Turbojet and turbofan engines certainly offer better efficiency at speeds below Mach 2.5, but they are vastly more expensive to put on something intended for a 1-way trip. If you want the fastest acceleration, you use fast-burning rocket propellant. I doubt very much whether a ramjet engine gives the kind of thrust that you can get from a rocket, for the same diameter and length of the motor. So this rocket-ramjet seems to be a curious thing to do, just for a medium-range SAM. The cited ceiling of 15Km is not bad, but its not that extreme: it could be done with a decent-sized rocket with a good payload. Rocket motors are much cheaper than ramjets to make. Multistage solid rockets are not unknown technology in India (ISRO uses 4-stage solids on much bigger missions). Airbreathing engines, especially ramjets (which have no mechanical compressor to pull in the air and compress it, but depend on the shock pattern to do it) have problems of stalling when they try to pull fast maneuvers. I don't think a TSPAF F-16 will hold a steady course for the convenience of an upcoming SAM: it will be pulling 9-g maneuvers to escape. So all this makes for a curious design for a SAM. As with many DRDO projects, this too now reveals other intentions and technology-development objectives: its many development programs rolled into one, while the critics sneer at it as a copy of some Russian missile or other. Knowing some of the people behind the Akash program, the new aspects are not surprising. Once the ramjet is shown to work, it can be scaled up: that's where the advantages begin to kick in. So lets not be so rigid on the 0.2kT number. That may be something else, pretty soon.Hitting a stationary ground target is fundamentally easier than hitting a fighter aircraft maneuvering at Mach 1.something, and putting our countermeasures. Yes, you do need to add some terminal-stage guidance, but a TV camera may be adequate for that. As for tank survivability, maybe the nuke experts can comment on this. The kiloton comparison is not everything. The nuke, I think, releases more of the theoretical "yield" than a conventional explosive. The conventional explosion is a chemical reaction, where the maximum temperature reached is perhaps 4000 K. The energy release is distributed, perhaps, over a larger volume. The max. temperature in a nuke explosion is a lot higher; perhaps 20,000K or higher. Energy release occurs in a much shorter time than in a dynamite explosion. Ionizes air; creates a shock wave which is far more intense. The initial thermal radiation (the flash) is far worse than that in a conventional blast. So the freight train explosion is not a correct analogy. For example, see all the discussion about a 15kT nuke going off in or above Mumbai. Well, a big ammunition ship blew up in Mumbai harbor in 1943 (I think). Though it killed many people, it was nowhere near as horrible as a nuclear blast.So, I hope the TSP apologists are reading this, somewhere. Today a ramjet SAM with multiple targeting, maybe multiple warheads. Tomorrow, a multi-warhead tactical nuclear cruise missile which can cruise at Mach 2, or 3, or maybe 4, to any military installation or terrorist formation anywhere in TSP. May be ground launched, may be air launched..And its designed, built and tested in India. No phoren parts, no need to read Chinese instruction manuals. It will keep getting scaled up in size, speed, accuracy and lethality.

Calvin · Post by **Calvin** » 09 Jul 2000 08:32

All this discussion about EMP has got me thinking about whether the optimum nuclear warhead for ABM purposes would be an ER warhead (i.e., neutron bomb).

Kuttan · Post by **Kuttan** » 09 Jul 2000 08:50

Calvin: 1. The blast has to be at very high altitude, essentially at the edge of the atmosphere. 2. The incoming missile is probably not down to its final warhead yet: it still has a protective cover, re-entry shields etc. 3. As the missile re-enters, the shock etc. forming around it ionizes the air anyway. Maybe the electromagnetic wave can get through this, but the metal shield can protect against it (source: the congressional minutes cited here). The electrons etc. are not all going to get through the "entropy layer" surrounding the re-entering vehicle. The density there is maybe 100 to 1000 times what it is in the outside atmosphere, and the temperature is extremely high, so most of the electrons, neutrons etc. coming in will get hit by other particles and bounced off. Of course I don't have a clue what a neutron bomb actually does. But by the above model, the EMP might kill everyting except the incoming missile.

Arun_S · Post by **Arun_S** » 09 Jul 2000 09:36

>>If you want the fastest acceleration, you use fast-burning rocket propellant. I doubt very much whether a ramjet engine gives the kind of thrust that you can get from a rocket, for the same diameter and length of the motor. So this rocket-ramjet seems to be a curious thing to do, just for a medium-range SAMWithout belabouring it let me try it again with another perspective:Acceleration is proposrtional to 1) THRUST and inversly proportional to 2) MASS (Payload, unburnt fuel and deadweight of casing).THRUST is proportinal to ISP (STandard Impulse of the fuel) and the rate of burn. Assumming same thrust between Ramjet & solid booster, thus the steel chasing strength & dead weight is assumed the same. Now lets assume the ISP of really good solid fuel stage is say 290. The Ramjet on the otherhand does not have say 45% of oxidizer weight, thus for similar ranged chemistry its ISP would be in range of 450 to 560. Now that is significantly better then any solid fuel stage in world. Unless of course the solid stage is much larger in size and weight. And for reaction time, you may try to simulate the max G thrust that one can get from a bigger solid fuel stage of ~300 ISP versus a smaller stage with ~450 ISP. It is hard ! the burn rate is so high that very thick maraging steel casing is required.. MASS: Now for the same thrust the mass of fuel for Ramjet motor is lighter w.r.t solid fueled stage, thus the former's final velocity would be higher.In reality ISP captures the net performance index of a rocket which takes into account thrust & as well weight of fuel.On another topic: Does the air propogated shock wave experienced 2 km away by 4000 K temprature blast any different from say 1000,000 K blast of same net energy ? Per my understadning NO. Of course the effect of flash and inonization is only applicable for nuke explosion. But I think we are talking about small sized 0.2 KT blast, and really the key factor aganisy a tank and its crew at 2 KM is: 1. the shock wave: the main factor; (which is comparable) and in my opinion not big enough to be effective aginst heavily armoured vehicle. 2. EMP : only nuke has it. The qualitative difference is here.In my openion EMP at 2 Km range is not strong enough for tank's EMP resilient electronics. 3. Nuclear Radiation: Nuke only. Yes there is an impact. But I am not an expert to estimate the dose & absorbtion by the armour. hardended Tank. My reasoning to all above is also moderated by the fact that Hiroshima's 20KT explosion at 5000 feet (say 1.5 Km) was 100 times more then the 0.2 KT under discussion.Cheers -Arun

Arun_S · Post by **Arun_S** » 09 Jul 2000 09:56

An incoming bomb in the missile would explode without jettsoning the RV shield. There is many reasons for it, mainly: 1. no need for jettison contraption 2. protect the payload againt re-entry shock wave due to MACH 14 speed. 3. protect against re-entry temprature as well as temp shock.The payload weapons electronics would in my openion would have EMP leakage from the bootom of the cone. But the EMP due to .2KT nuke is expected to be so strong at 200 m proximity that I belive no EMP shielding can bear it unless of course it is hermatically seald in metal. On the other hand I do not think the electronics of ballistic missile would survive the intense nuclear radiation (Gamma rays, nutrons & eletcrons) coming from a blast 200 m away. On another note: The EMP reference by Sarvatra (http://commdocs.house.gov/committees/se ... 7010_1.HTM) is more relavent for am EMP focused attack by an enemy. Thus the yeild under question is 20 KT to 10 MT and for more coverage it is done outside the atmosphere.

Kuttan · Post by **Kuttan** » 09 Jul 2000 10:36

<BLOCKQUOTE>quote:<HR>Assumming same thrust between Ramjet & solid rocket<HR></BLOCKQUOTE>That's where your problem is, as I stated in my previous post. For the rest, my understanding of Newton's 2nd law of motion and Isp is much the same as yours. As you put it, thrust does depend on burn rate, which means two things: 1) rate of heat release and 2) mass flow rate of propellant being ejected through the nozzle. Both I believe are better for the rocket. Also, rockets have much less drag because they don't have sharp-edged inlets with their shocks, etc. So less of the thrust is taken up in canceling drag caused by the engine.Why is rocket thrust for a given nozzle throat diameter bigger than what you can ge from a ramjet? Well, consider: The thrust depends on exit velocity achieved. To get higher exit velocity, you need to start with higher temperature and pressure in the combustion chamber. The highest pressure that you can get in a ramjet is the pressure obtained by stopping the incoming flow. I assume that you know enough of the "isentropic flow" relations to figure out for yourself the stagnation pressure at, say, Mach 2.5 at about 10,000 meters standard altitude. A rocket can be built to take much higher stagnation pressure than that, in the combustion chamber. Now don't get me wrong: I am a very strong supporter of ramjets for all the reasons that you mentioned. All are applicable to increasing range and endurance and the ability to control the thrust (very tough to do that with solid rocket motors: you just light the match and run for it, so to speak). Just to accelerate fast, you do a controlled explosion, dumping hot gases out the nozzle at the highest possible exit velocity. You really don't want to waste the heat on warming up nitrogen, which is the other problem with air. Lots of inert nitrogen to be heated up. Thus, to get max acceleration, you use a rocket with a "burn rate exponent" close to 1 (verges on becoming unstable and blowing up) Example: Patriot missile. Now for the high-temperature stuff: Shock wave from 4000K vs 20,000 or 100,000K: Off-hand, I'd have to say that you are quite wrong on this. Basically, (and of course simplistically to avoid a 2-page derivation) a shock wave travels at what it believes to be the speed of sound in the medium behind it. Speed of sound increases as square root of temperature. Pressure is momentum flux of molecules. Molecular speed of motion increases as square root of temperature. Density increases as pressure increases; in fact density behind a high-temperature shock is orders of magnitude higher than ambient density. So the shock from a nuke is likely to be far more destructive than a shock from an equivalent kilotonnage of TNT. The TNT shock is a detonation wave, which is a reacting shock. This is a complex phenomenon, which I don't understand except that it travels typically at upto 6 times the speed of sound in ambient air (note that this is worse than just the effect of the temperature). Detonations do damage for three reasons: the temperature and the pressure, and the fact that an expansion wave follows, and shakes down whatever survived the compression wave. Very high wind speeds also follow. Calvin, I fear, will smash my guesswork on this nuke-TNT comparison within nanoseconds, but hey, you learn something new every day

Actually temperature is a poor measure of "degree of hotness" beyond about 3000K: air at 10000K contains a heck of lot of "hotness" or enthalpy than one would expect based on the temperature. This is due to the energy soaked up in vibrating the molecules, splitting air molecules into atoms, and then ionizing those atoms and knocking free electrons out. None of this actually shows up as "degrees K" which is purely translational motion of molecules. So a 20000K nuke explosion is far worse than a 4000K dynamite blast. Was the Hiroshima bomb really 100 times more powerful than a modern small-payload nuke? I wonder seriously about this. Was it really 20kT or 2 kT? What about tactical nuclear artillery shells? How many kT are they, and do tanks just go cruising through those blasts? The main purpose of those, I thought was exactly to stop tank-supported invasions.Is a tactical nuke artillery shell so much bigger than the payload on a medium SAM? Finally, as for the EMP, neither Arun nor I have a clue except for what we read from Sarvatra's congressional testimony report, so I won't waste time on that.

Johann · Post by **Johann** » 09 Jul 2000 13:17

A single optimally detonated tactical nuclear weapon should not be able to destroy much more than one armoured company prepared for nuclear attack, either on the move (two at most) or dug in and camouflaged, or one prepared infantry company (some say platoon though this is unrealistic) out of a battalion (assuming ~ 2-3 days to prepare defences). That's the rule of thumb. Tank intervals would be ~ 100m while on the move. Dug in, ~150 meters between tanks in a Platoon(4 tanks per Plt.), 300 meters between platoons in Company & 1,000 meters to 1,500 meters between Companies in a Battalion. Exact amount of damage done of course will depend on factors such as masking effect of terrain, formation type and dispersal of the unit, height of detonation, exact yield, etc, and level of preparation of vehicles. Tanks buttoned down, radios turned off, working NBC filtration and overpressure systems, radiation liners etc. Older NATO 7 Warpac tanks have the advantage of rugged simplicity as well as hardening of components against EMP, though of course this did not include radios. Challenger, M1A1s Leopard II A4s, and contemporary Soviet tanks in the European theatre were designed with the full expectation of operation in NBC conditions. I don't know what their vulnerability is today with the new generation of digital equipment. Varying damage can be expected over 4 psi (which will demolish houses not built out of concrete, brick or the like) - at the very least damaged optics, antennae, external stores, and even track damage. Thermal effects usually result in ablation of tank skin, usually too brief to cook the crew. According to the graph 1kg of TNT produces 4 psi in peak overpressure at ~ 6.2 m from ground zero.Going by the scaling formula dW = do (W)^1/3whereW = the equivalent amount of TNT in kg do is the distance in m from 1 kg TNT dw is the distance in m from the W kg of TNT equivalent. your 0.2 kt nuke will exert 4 psi at 6.2 x (200,000)^1/3 = ~ 362.6 mThis is not going to be a worry for the tank 2000 m below![This message has been edited by Johann (edited 09-07-2000).]

Arun_S · Post by **Arun_S** » 09 Jul 2000 14:54

Thank you Johann.My friend Narayanan tried to trap me in parts of nuts & bolts without concluding on their net impact on overall terminal velocity, so I did some little research and found that Ramjet performace is substantially higher then my initial stakes. The fact remains that ISP is the bottomline performance measure to all rocket propulsion.Some very interesting sites for reference: <A HREF="http://www.au.af.mil/au/2025/volume3/ch ... Hypersonic" TARGET=_blank>http://www.au.af.mil/au/2025/volume3/ch ... ersonic</A> Attack Aircraft (SHAAFT) <A HREF="http://www.ptw.com/~oglenn/trimode/3m-brief.htm" TARGET=_blank>]http://www.ptw.com/~oglenn/trimode/3m-brief.htm]</A> <A HREF="http://www.ptw.com/~oglenn/trimode/3m-arla.htm" TARGET=_blank>http://www.ptw.com/~oglenn/trimode/3m-arla.htm</A> They all point to ISP of between 1000 -1700 (inspite of using shock based compression) {though the pressure is lower then say rocket stage, but the thrust is made up by the mass of air breathed into the rocket. The nitrogen compression is effectively used for momemtum transfer in the jet}. Assuming ISP for solid fueld ramjet is lower, even an ISP of 700 will make an equivalent solid fueled rocket a monster (in size and weight) for it to match the accelation profile and final speed of Akash, not to mention the size.If required I can run the approximate numbers on my rocket simulator. For now its too late in night for me.BTW: All SAM's rockets get expended earlier on and most of the time they coast to the target using wings /fins to take care of targets evasive maneuvers. So interference with ramjet's inputs compression is minimized. Also note that there are 4 inlets for Akash on 4 sides.Cheers -Arun [This message has been edited by Arun_S (edited 09-07-2000).]

Philip · Post by **Philip** » 09 Jul 2000 15:08

I'm surprised that AIR is being taken so seriously.If you believe everything that you hear on AIR,every missile test including Trishul will have a nuclear flavour!Akash has always been India's prime SAM project,now to be integrated with the Russian S-300 family of ABMs (with Israeli help) to develop an integrated missile defence for the country.The success of Akash will find it's way into the next generation of naval warships too.

Johann · Post by **Johann** » 09 Jul 2000 15:51

Thank you Arun, I've corrected the oversight.