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Posted: Sep 5 2008, 06:50 PM
Member No.: 1
Joined: 3-November 07
The evolution of surface-to-air missiles, started from 1960, was constantly connected with increase in launch and transported mass. New systems required heavier launch platforms or carried fewer missiles per vehicle. Man-portable systems became crew-served weapons rather than individual, and their 'man-portability' required a dedicated soldier carrying nothing else, increasing the practical team to 2 or 3.
While the effectiveness has undoubtedly improved, the possibilities of weight reduction have been occasionally neglected in favor of rolling out the newest system as soon as possible. The armies were left without one-man air defense weapons or modern all-in-one TELAR vehicles once again.
Since that was unacceptable in aircraft-dense environments like that of Vault 10, a rollback in the systems weight was required. The new missile series, developed by ALC, was designed to rectify that fault and provide ground forces with compact and lightweight air defense once again.
MLSA-10 "Dart" is a highly modular ultra-lightweight air defense system, consisting of a launcher, the missile itself, available in different variations, replaceable booster packages, and additional missile internal electronic and chemical systems. Space for three additional circuit boards or special modules is intentionally left inside, for current and future mission capability enhancement.
The airframe of MLSA-10 is composed of four distinct sections: the curved nosecone, the oxidizer tank, the semi-rigid polyethylene fuel section, and the engine section.
The nosecone is built of fibreglass reinforced polyphthalamide, a low-cost, lightweight, impact resistant composite, structurally sound in temperatures up to 500K, sufficient for the missile's operating conditions. It has conventional straight bidirectional reinforcement and corrugated structure, protecting the seeker head from drag. A magnesium ring supports the one-piece, three-layer chameleon glass sensor cover.
This section is mated to the rest of the missile through tight mechanical fit and a reinforcement ring, and can be separated in workshop conditions for electronics replacement or repairs.
The oxidizer tank has only one layer of unidirectional fiberglass covering its main structure, composed of hardened 5mm thick magnesium, and forming the fragments casing upon detonation. Within, in a bladder, the oxidizer itself is contained. As opposed to the nosecone, the tank section structure intentionally facilitates heating of the liquid inside.
Aft from the tank, the solid fuel section is a solid 95% polypropylene block, with minor inclusions of heat-resistant polymers for structural integrity, wire-wound with glass fibre on the outside. Eighteen separate ports, in two concentric 12 and 6 channel rings, are left in the block, forming slowly increasing combustion surface.
Finally, aftmost is the semi-exposed convergent-divergent nozzle. However, gimballed engine thrust vectoring couldn't be used due to mass and cost limitations, so the engine is fixed in place. A pro-side of such arrangement is that no wiring goes further than the oxidizer tank.
To save weight, in place of simple but inefficient solid fuel, a new fuel system had to be designed, and, to save cost, MLSA-10 has inherited some solutions from the MLSS-21 family, built with similar demands in mind. The exact kind of fuel used, however, was changed significantly.
The Dart Missile uses a self-pressurized hybrid rocket system, with aft rocket body serving as the solid fuel combustion chamber and forward as the 98% hydrogen peroxide oxidizer storage. To improve initial fuel transfer, the oxidizer in the tank is mixed with hexane, a volatile hydrocarbon fuel without a tendency for hypergolic reaction with hydrogen peroxide. For more precise control, a fiberglass ball-shaped container at the edge nosecone section contains pressurized oxygen, that is used as a coolant for the seeker head, and then vented into the engine at a valve-controlled rate, thus providing precise rapid throttling for the engine.
While a booster isn't strictly necessary, to accelerate the missile quickly, and protect the shooter, the ports and the engine may be filled with a low-temperature solid fuel, normally in a granulated powdered form, which facilitates rapid ignition and start. Since this was seen as partly unnecessary, not weight-efficient but space-efficient, the additional fuel can be loaded and removed by the user, held in place by the nozzle cover.
The variations include: AMLSA-10-41 - smokeless propellant to maintain good view of the aircraft, supplied in all variants with communicating launcher; -43 - "cold" system with low exhaust heat energy, enabling firing from enclosed space; -44 - range-extending efficient solid propellant. All of them give the shooter a delay before main motor ignition. Boosterless launch requires protection from the engine exhaust.
Due to lack of conventional control surfaces or thrust vectoring, the missile is steered by a four-disc common valve in the intertank space instead, which restricts the flow of oxidizer to combustion channels in either side. That in turn alters the flow of exhaust through the choke, creating less efficient, but directed exhaust at the divergent section. As the oxidizer channels are located near the edge of the missile, it is a positive-feedback process, since the centrifugal effect forces further more oxidizer into the chamber. It provides the missile with very fast turning ability, at the cost of a strong tendency to oversteer, leading to greater susceptibility to deceptive evasive manoeuvres. This represented the major challenge in design, which in part forced lower length:diameter ratio to reduce missile's static momentum.
But, critically, it avoids the bulk and cost of high-force linear actuator systems. The drawback of oversteer has been considered an acceptable cost, since nearly all countermeasures and classic manoeuvres are designed to rather exploit missile understeer, and MLSA-10 isn't intended against expert pilots, which are increasingly rare nowadays as newer avionics take on more and more of their job.
As described above, the missile has no distinct warhead section. When the detonation time is calculated, a valve is opened, which, provided the missile is sufficiently hot, purges the oxygen tank through a small tank containing a ketone mixture. Upon combining with the hydrogen peroxide oxidizer, it produces MEKP, a sensitive liquid high explosive. Depending on the amount of fuel spent by the moment, the missile will either shut the valves to only use the tank for fragmentation, or allow some of the explosive to feed into the fuel ports, to utilize the entire missile. Explosive power will depend on the amount of fuel left in either case, and will effectively match a 1.2kg blast fragmentation warhead at nominal range with tank-only explosion, or up to 2.0kg warhead with excess fuel.
This feature makes the missile highly safe in moderate conditions, since initially it has no explosive, and can't produce any unless sufficiently heated. To avoid explosion in fire, overheat of the internals above 400K will trigger a pressure release valve that releases the second component and permanently deactivates the missile.
While overheating itself doesn't cause the missile to become explosive, a combination of strong overheating and an extreme crashing shock might lead to formation of the explosive, so it's strongly recommended to maintain a temperature below 345K (70 degrees Celsius or 160 Fahrenheit) in storage or transportation.
MLSA-10 internal tankage structure has been tested not to break from shocks producible with human force, ensuring safety in human handling. A specific feature that can be viewed as an advantage or a disadvantage is that the missile is physically incapable of exploding unless heated in flight (from both fuel burn and drag), so has a minimum range of 50 to 300 meters depending on ambient temperature.
For use in arctic conditions or special tactical applications, a user or factory modification is available by replacing the binary fuel with a lighter one, that ensures detonation regardless of range. This decreases the inherent safety to the level of conventional missiles like Stinger and Igla.
Since the goal of the project was to create a system as light and simple as practical, the complex two-piece guidance activation of most MANPADS had to be rejected. Instead, all MLSA-10 systems are enclosed within the missile, and powered by an integral copper-magnesium battery, which has nearly indefinite shelf life until activated, and partially uses missile's magnesium airframe as the anode, simplifying the wiring. In case the missile was activated but not fired, it can be deactivated by refilling the electrolyte, although no more than a few times, with decreasing reliability.
All target acquisition is performed by the missile itself, using its trichromatic (IR-C, IR-A and UV-A) imaging sensor to lock on the exhaust and the target body. The latter can only be used during daytime, and only if the target is high enough, but decreases the susceptibility to decoys, otherwise the seeker operates bichromatically. If an advanced launcher with SACLOS is used, the missile can lock on to the reflection of the UV-A laser marking the target, in night or day.
The chameleon glass covering the seeker head makes the system lose sensitivity if the target is against the sun or utilizes countermeasures, but prevents accidental damage to the seeker head from strong light sources.
All processing is performed by one electronics board with five digital binary silicon-based integrated circuits, the high-density CPU/memory unit and EEPROM unit, and low density power rectifier, control signal operational amplifier, and seeker head interface, decoupling its sensors from the processor. This board is replaceable, and currently includes a 8 MIPS, 10 MHz, 24-bit RISC processor, with 2MB of synchronous MOSFET SRAM and 2MB of EEPROM, all manufactured with 250 nanometre technology.
There are four types of launcher, heavy, medium, light and ultra-lightweight. Only the heavy launcher always includes a monitor for the user, and the medium has it an attachment. Light and UL launchers are simply fibreglass tubes.
The Light launcher is guaranteed suitable for 4 shots (with average endurance of 6), having heat-resistant matrix, internal structure, structural lining, and contains manually opened lids. It has ports for attachment of electronics, can be mounted atop vehicles with standard a VTS-105 mount, and is otherwise usable.
UL launcher is simply a sealed single-use tube which is only needed to protect the missile from damage.
In order to monitor target detection and tracking, the shooter needs an external display, which may range from a helmet-mounted display to a vehicular system.
Other launchers aren't any less boring, but they do include a display. Later.
The least interesting section
MLSA-10 - Missile, Light, Surface-Air, Platform Class 1 (man-portable), Standard Design.
Diameter, missile: 70mm
Diameter, container: 80mm
Weight, missile, basic: 4.0kg (no booster, fire&forget)
Weight, missile, standard: 4.5kg (MLSA-10-40 booster, radio comm module)
Weight, missile, maximum: 5.0kg (permitted for all systems)
Weight, storage container: 0.4kg
Weight, MLSA-10-10 ultra-light launcher: 0.4kg
Weight, MLSA-10-12 light launcher: 1.0kg
Weight, MLSA-10-14 medium launcher: 3.0kg
Weight, MLSA-10-16 heavy automated launcher: 12.0kg
Maximum velocity: 900m/s
Average velocity: 700m/s
Fuel limited range: 9,000m
Fuel limited ceiling: 7,000m
Maximum Range (effective): 6,500m
Minimum Range: 50-400m (depends on temperature)
Ceiling (effective): 5,000m
Maximum target speed: 450m/s
Production expenses: N$16B per million
Unit cost: N$20,000 for million+ orders;
Variable for small orders.
( Sold here: Hub Limited Exports )
[Whatever else I've forgot...]
And, though I don't keep lists of whatever I've read to reference in the design, here are some references and links for what was most useful in the design:
Rocket performance calculator and optimizer. Suitable for all kinds of rockets, has a database of over 300 propellants (so you only need the name). Note this the real thing, used by USAF around 1990s.
Minimum cost design methods
Polyethylene and H2O2 hybrid rocket testing
Bipropellant self-pressurized rockets
High regression rate hybrid rocket propellants
Posted: Sep 5 2008, 06:53 PM
Member No.: 1
Joined: 3-November 07
There are possible other versions in plans, specifically a normal weight missile and a higher performance (and more expensive) version, but first I'd like to see any feedback, comments or questions on this one. Everything is welcome.
Also, if you don't understand something, just ask, and I'll expand that in common terms.
Now some more detail...
First, I'll explain the designation, as say MLSS-21 having heavy versions was a bit counterintuitive. The "L" is best explained as "Lightened" - it's a new missile line, built around improving the performance of low-weight and low-cost solutions, rather than lightening complex and expensive ones. So MLxx are not necessarily lighter than other missiles, but lighter than other missiles of similar performance.
As for how the MLxx-xx series of missiles are lightened, they, first, use a lot of components in dual purpose, e.g. MLSA-10 airframe is mostly supported by its hybrid fuel (it's a plastic) and warhead casing, doubling as the oxidizer tank. That has certain downsides, such as making the maintenance so hard that zero- and low-maintenance components are needed instead of ones that give rocket science its reputation for complexity.
So performance is not the pinnacle of what can possibly be achieved, but, instead, balanced with weight and cost. Actually, even within the hybrid rocket technology, I found some more effective solutions, but all of them had downsides: dangerous, unreliable, fragile, maintenance-intensive, very expensive, or several combined. In the end I've decided to go with the bulletproof-reliable technology, even if it makes the missile a bit heavier or a bit less effective - sensible sufficiency principle.
I think much later I'll need MHxx heavy missiles, but I don't see design without weight and cost limits as a challenge, so it isn't interesting for me, at least not as much as with these limits.
What's the practical intent of this MLSA-10 missile? Two key points: light and simple. No external cooling bottles, battery checks, extreme care in handling, lock-on complications. That allows it to be used as the second weapon, just carried along with the squad, or inside a truck or APC, or even stored in a house, and used without specialist training. But most importantly it's a MANPADS than can be hanged on one's back (it's the size and weight of a battle rifle) and just carried for when it's needed.
Now, component breakdown, to explain the cost, is it high or low in comparison, and why each decision was made. Well, really I post this just because I think you might find it interesting or even useful. Since costs are approximate, I've rounded them up.
Airframe: Heat-resistant fiberglass - $300. A cost saving over aluminium structure, and somewhat mass. Really it's so light and cheap here only because it has little structure and so is weaker, but it's suitable for a hybrid rocket: its fuel is a structural plastic itself. Commonly, airframe is up to 25% of the mass.
Seeker head transparent cover - $1000.
Hydrogen peroxide tank, magnesium, with a bladder - $300.
Engine - $800. Worse than $100 for a solid fuel one, but way better than thousands of dollars a liquid rocket engine would cost.
Valves - $600. Cheap compared to control surface actuators or gimbaled engine thrust vectoring.
Binary explosive component - $200.
Fuel - $50 fuel + $50 casting. Classic PE+H2O2 hybrid fuel is way cheaper than any other, and on top of that, environmentally no worse than kerosene. In contrast, solid fuel is way more dirty and toxic. It's not just an ecology issue: some fuels are so poisonous the shooter would require special protection just to fire them; and an accident, you just pray it doesn't happen.
The rocket with this fuel combination, pressures and nozzle configuration, as optimized by the calculator (see reference), gains a practical (adjusted) specific impulse of about 220s at low altitude and just 150psi pressure.
You might have read figures like 250s and even 280s for solid rockets, but these are in vacuum, with perfect grain, and often theoretical. Due to atmosphere and imperfections of various kinds (particularly the grain), military solid propellants only do 200s in air, at significantly higher pressures, which mean heavier casing and engine.
More importantly, solid rockets burn a lot of their fuel in vain, often even counterproductively. A solid rocket is like an ultimate American car - no steering, no brakes, only one good RPM. But even worse, since the throttle, once pressed, is glued to the floor. Hybrid rockets, on the other hand, throttle almost as well as true liquid rockets, and have good internal control. That both conserves fuel and improves maneuverability, and therefore hit probability, or, failing a hit, allows for closer proximity detonation.
Seeker head sensors - $3000. This is one of the major expenditures in any guided missile, but, however, can't be made cheaper if the weapon is to actually hit the enemy.
Onboard computer, at 250nm process - $2,000. Actually, if made at 45nm process as modern processors, and to the same quality standards, it could cost just $200, but the finer the process, the worse the reliability and the more susceptible it is to things like EMP or just a voltage surge.
Control amplifiers, battery, other power electronics - $500.
Support development costs - $5,000. This is not the initial R&D cost, but recurring costs, such as acquiring and uploading the profiles of new aircraft, programming for different field conditions, regular firmware updates.
It's really very low, and the missile will only start paying off once millions of them have been sold. As it's well known, Stinger's per-missile R&D cost was about $6 million.
Assembly - $1,000. Assuming a high degree of automation, but a lot of operations are still best done manually.
Quality control - $1,000. Of course, it could be skipped, but it's best not to.
Packaging, labeling, other minor costs - assumed about $200.
That arrives at $16,000 per missile production cost, compared favorably to $50,000 for Stinger production.
As for sale, IRL Stingers "retail" at $180,000 to NATO nations, and Igla at $100,000-$300,000 depending on the associated equipment and the customer. The difference between production and export cost is caused by very high R&D expenses, even when spread among every missile.
And now, since I've talked about that calculator, here are the results of the optimization:
Mind you, the optimal propellant proportions were found by the program, I only specified the ballpark range and some necessities (hexane, water).
The second table lists missile performance and design figures: particularly useful are chamber and throat temperature and pressure; then it gives Isp at sea level and at altitude I've specified, i.e. 3 km.
The third table tells what the exhaust will consist of: as seen here, 55 grams of water, 32 of CO2, and a bit of other stuff, per 100g of propellant.
Finally, the fourth table, summarized after all optimizations, is the custom output. Any number out of 18 options can be selected, at various stations, with additional customizable parameters. Here, I ordered it to tell me the delta-V and payload, both at sea level and at 3km. Actually it has listed a lot of values, since it optimized for various configurations, but I only left my initial guess, the pre-final, and the final decision.
Delta-V is how fast a missile using this fuel and engine can theoretically accelerate to, without payload, if there's no drag, in feet per second. The figure is pretty high, at 4400m/s, but, however, it can only be achieved without any payload and any drag (I could specify payload, but I had to find it out first). Yeah, you're not going to space on this missile.
Then, "payload", of course, should be multiplied by actual propellant mass, and will give payload mass. It says I can add 71% as payload, so, for 2.5kg of propellant, that is 1775 grams. Since the essential hardware weighs 450 grams already, the maximum missile mass is 2500+450+1775=4725 grams. Of course, there's a caveat that some of that would be eaten by drag, plus it has to maneuver a lot. That's why I've specified 1500m/s velocity rather than 750m/s the missile would actually reach.
All in all, it's really an amazing program. Combine it with a few other calculators, and it's brilliant.
Edit (not really): The stuff below is boring. I just find it easier to design while writing, and so take it as a record of the design process thoughts.
Now, I needed ceiling and range figures. Of course, considering how great a propulsion system I'm using, the missile can go intercity if it saves fuel, and seeker head capabilities are the limit, but ceiling is easier, as it does depend on the engine.
As I'm flying at 750m/s, I've got another 750m/s of deltaV to spare. A ballistic calculator told me I'll spend 40m/s per kilometer, at my speed and drag coefficient of 0.20. With my thrust, the linear acceleration is 9g, of which one is eaten by gravity, so the missile reaches 900m/s from booster's 100 in 10 seconds, being at 5000meters, minus 120m/s in aero drag. Don't ask me how I got these 10 seconds, I just guessed, then tested my guess, and it was right. Well, back to. Gravity drag has consumed another 100m/s, so there is 530m/s left. At the cost of (a-drag*0.75)+(g-drag), or 30+10, per second, the missile has another 14 seconds to fly. That means the technical ceiling is pretty great, really, about 15,000 meters, and that's a low estimate, since in a straight line the real drag coefficient is like 0.01 or something.
But, since this is not a sounding rocket, a certain amount of deltaV has to be left for the interception itself. Unfortunately, thrust vectoring totally sucks at fuel economy (keep that in mind for the future!): it can't reuse the speed, so, presumably, I'll need to reach my target's speed using mostly fuel. Here go the 480m/s of spare deltaV. In practice, the missile won't do that 90-degree turn, but it will stand in for all other maneuvers. At these 480m/s, at 8g, there are 6 seconds, so there's about 2000m to go, with residual 250m/s velocity.
Very little is left to determine the range, and I'm bored with math. So I just drew all of this and measured the practical range - where you could actually shoot down a plane. Which is 9000m, and the ceiling is 6500m; that's with inefficient maneuvering.
Now, you perhaps think I'm cheating or just wrong, since that exceeds the figures for heavier missiles, and so did I think. But then I calculated Stinger's max range and ceiling using the same method, and it turned out to be just 6000m/3500m, even accounting for lower velocity. How come? Well, out of Stinger's 10kg, 3kg is the warhead, 2kg the airframe, 1kg old electronics, and just 3kg the fuel - 30%. In MLSA-10, out of 4.5kg, 2.5 is the fuel - 55%. That's not to mention the fuel in Stinger is noticeably worse; so this missile has more energy than Stinger, to drive a missile that weighs just less than half as much. Like a car stripped for racing versus one loaded with bricks. This comes at the cost of terminal damage, but then Stinger is ineffective against heavy bombers anyway; what's death to a F-22 turbine is debris test to 747 one. Though some tricks are used here to improve damage, particularly, the magnesium frame, heated in flight, is good incendiary material. Otherwise, while less damaging than Stinger, Dart trades it for hit probability and envelope.
As specs cut 1,000m from Stinger, so did I cut 1500-2000m, to account for practical issues.
So, here go the revised specs.
Maximum velocity: 900m/s
Average velocity: 700m/s
Range (maximum, fuel limited): 9,000m
Ceiling (maximum): 7,000m
Range (effective, seeker head limited): 6,500m
Ceiling (effective): 5,000m
BTW, another interesting calculator, much simpler.
This is of course not a professional tool - Rocket cost Java calculator - at least compared to the USAF calculator, but it's just curious to see the results. And, of course, since it's easy, quick and fun to use, I suggest you try it yourself sometimes, for a ballpark estimate of missile costs.
It says the rocket part of MLSA-10 should cost $8,000, but that's of course not including $6,000 worth of electronics aboard. Yeah, says it right here, the link includes my data.
By the way, it also says that if I made it a true liquid rocket, it would cost 42 grand without electronics. Sucks, doesn't it? And that's just a peroxide decomposition powered pump.
I was thinking more along these lines:
Got it as small as practical, but still some distortions. To clarify, all coloured words are indicators of respective colour when lit. Normally they aren't visible.
( For people with larger monitors, here's a cleaner version: http://www.freewebs.com/vault_10/MLSA1400.png )
Now, the question is... I want to make an interface intuitive enough to be understood immediately by any user having just a basic idea of MANPADS. So, to everyone reading: How many of the buttons and screen indicators did you understand, and which specifically were confusing?
Do you think you would, generally, be able to use the missile without instructions?
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