tavarish palkovnik

Do you have this specifications for Mk 78, I can't find it in some readable format. It would be appreciated if possible to share it here. Of what I've found about all these Shrike's motors, I only got total confusion. Mk 78 Mod.0 Mk53 Mod.4 and Mk39 Mod.7 are what I'm interested for. For first two there are some sectional views (which are kind of same actually based on source) while Mk39 Mod.7 is total mess. Some says it is single thrust model while other says dual thrust, and two totally different concepts (sectional view pictures) are signed same

Already have employment, this is just a hobby and interest of mine. There is no enough math, never been, math is all around us. Tell me please, what do you think, do you have in this simulation correctly modeled Phoenix in mechanical point of view? This second sentence of yours is very worrying. Looks like situations in corrupted states where if you are not member of ruling political party you can bark all days long and nothing will change Just joking, now honestly, like said it doesn’t bother me at all if anything get changed or not. But if I manage to make, at least few to get interested in all this and to start asking questions and perhaps express doubts, the goal is done. Once I said here, flood on internet of wrong information about Phoenix is coming mostly from DCS and WT. And I stand by that, simply, I don’t know terminology for that, but googling commonly sends you to related pages and then it is to late So, math will continue , maybe guys from HB, or HB is a guy, I don’t know, will join us in this conversation, who knows. Stay well all of you

Keep trying, there is somewhere in these last pages PS: short input, short output

Already done at -40degC but seems you didn’t read it Fun fact…fuel in wings of passengers airplanes…outside hard minus, but friction which rises with altitude in same time warm that same fuel and fuel is in normal liquid state and there’s no need for heating elements Of course when aircraft goes in supersonics that change everything but not in way that minus will overcome but aircraft is going to be overheated

Let’s put this stability aside for now, that would be really too much, of course if someone is interested in this also, no problem whatsoever to go through it. Subject is indeed interesting, not so easy to follow for those not having basics of mechanics but everything can be learned. I said it’s maybe time to leave all this…but no, I will not leave it yet. Few days ago I saw, some guys on WT forum where they also talk about Phoenix, found some document and, step by step, some ideas started to rise, and it is a matter of time when that will flood internet again over already flooded internet when Phoenix is topic. Anyway…OMG how young’s like to say, somehow (I don’t know how) they got to theory that rocket motor burn time depends of altitude and that Phoenix’s motor depending of that can burn even up to 40 seconds … and that’s not all, at lower altitudes when paper work is read literally motor burns 15 seconds Let’s make retrospective and let’s see what mathematics says what is burn time, although it is already clear, at least to me, not from my calculations but NASA’s data, I’ve just calculated it my way to see does it fit, and it fits perfectly, from 20 to 30 seconds depending on temperature. Now let’s use formulas involving neither specific impulse neither coefficient of thrust, but let’s go over characteristic velocity c* What we have fixed: Tc=5400-5700F … average 5550F what is 3339K At=0,002408m^2 (Dtr=2,18”) m=168kg pc=700psi=4,8MPa (Rocketdyne’s data for reference chamber pressure) k=1,2 … like most of Flexdyne CTPB compositions as well as R=307,9 And what would be characteristic velocity from Tc, R and k -> 1563 m/s Now from characteristics velocity, chamber pressure and throat area mass flow rate goes -> 7,395 kg/s And of course end is 168/7,395=22,7 seconds as total burn time, average at normal temperature. With mine 4,5 MPa as normal average it goes 24,2 seconds. 22,5 23,5 or 24,5 it doesn’t matter…but fifteeeeeeen to foooorthy

What about Cy function (lifting coefficient and static stability) ? Did he make it as well? You know, with these loft scenarios Cx is not going alone without Cy. And….uffff…this so complex, writing in not native language is difficult especially when subject is not so basic. Shortly, their AIM-54 could easily in this scenario become “AIM-180” , how I from jokes use to say, when angle of attack just turns nose of missile backwards

Come on man, don’t exaggerate it now. Let’s stay on ground, this is after all just mathematics and mechanics

In these 7 seconds missile is overloaded of course. Overload is α*Cy*v˄2*ρ*A/(2*m*g) and because motor doesn't have enough kilograms of thrust, starting velocity gain is lower. Lower velocity for same G overload means higher angle of attack and then induced drag is coming in game Cx ind = Cx (α=0) + α˄2*Cy/57,3 Everything is connected. Simply, motor as in game and in addition for high altitudes where atmosphere is rare will give such velocity ''brake'' ... which is not normal. Normal motors, by the way, usually have higher thrust in start, just take a look how thrust-to-time curve of Sidewinder looks like. Also one of steps in chain of arming missile in flight is data from motor, data about chamber pressure, usually data is when pressure get down to some fixed value

Reconstruction of DCS model trying this 48kft 2M launch Document1.pdf And soon I will again be without possibility to upload files because reaching given maximum

So, in this last image ''red'' case is Phoenix with its nozzle expansion ratio measuring 18,5 and ''blue'' dots are various tactical motors, there are various Sparrows, Sidewinders, Falcons, than Amraam, Genie, pallet of Rs, 23, 60, 27, 27ER, 33 also some air-to-ground like Harm, Hellfire etc. Maverick is missing because its motor is also extreme with expansion ratio measuring just 2, extreme but on other side from Phoenix, so much extreme that third method is not even applicable. But what image is showing? It's showing that all these motors are more or less grouped together, alright R-60 and Hellfire pop out a bit but still everything is under control and understandable why. And all these motors work just fine down, and also up with some slight gain getting with altitude. Only Phoenix is with huge difference in thrust at sea level and up there. That's why it is special case, it is intentionally designed to give maximum where tacticians placed it. Other motors are not so much customized but made as universal, fine at sea level, better when higher but that all is measured in just few percentages...except with dual thrust motors (R-33, AIM-7F, AIM-120B and AGM-88) where this percentage is rising significantly when motor works in sustain stage. I got impression that when common internet write about this altitude gain only external diameter of nozzle is in focus. And that is wrong, without nozzle expansion ratio and chamber pressure all that story is useless. AIR-2 Genie has huge nozzle exit, 296mm is exit diameter what is bigger then Phoenix's bell of 238mm but expansion ratio is just 6,7 and gain with altitude no matter of huge exit area is just slight, nominal sea level thrust of 155kN will be improved just for few percent Maybe is time now to left this, it is up to you guys now to fight for it, to get Phoenix in game in more realistic shape. It will ask for different approach but special case looks for special approach. If I can help with something else just shoot

To help a little bit more, to understand how this motor is special and why it should be taken as uniqe case Three methods how to calculate pressure at nozzle exit. First formula is the most precise but very inconvenient to use and it gives pressure 25237 Pa. Second method is approximate method but still fine and enough precise and it gives 25634 Pa. Thrid one is for those not like formulas, and it gives 26163 Pa. All three results are with average chamber pressure 45 bar and heat ratio 1,2 About this last image latter today...

Don't be so sure Indeed I can't see what exact code is implemented but with reversible method it can be easily figured out. Maybe you expect that motors in DCS are modeled in details, but they are not and like said it is understandable, who would make all these motors to be precise and perfect. So everything can be detected because of simplifications used in DCS and all other similar games. Give me several level (horizontal) flight envelopes velocity-time and distance-time for active time (when motor burns) let's say 1,2M launch velocity (or better 1M because 1,2M at 1km exceed limits) at 1, 5, 10 and 15km and let's see can we see or not what is code, what is motor thrust at these altitudes. DCS simplified principles is Isp*m, always linear thrust, not involving details like chamber pressure, pressure at nozzle exit, nozzle expansion ratios, throat diameters etc etc etc and that's perfectly right for most of motors. Even 7% principle when increasing thrust as altitude gain is fair enough because it fits quite fine for most of motors...but not this one. Deliberately said ''one'' not ''ones'' and who was reading me know what it means. This motor simply can't be ''molded'' together with Sidewinder, Amraam, Sparrow and pallets of various other tactical motors because with its huge nozzle expansion ratio it is simply different and needs different approach...believe it or not We have saying to someone when ruin established facts, you are destroying snowman, and I know that is exactly what I'm doing But not from wickedness but from engineering needs for precision

You are welcome @Маэстро Of course if something new appears, somewhere, about this motor, to confirm or correct this a bit or…rebut it, I will share it. But like you said, it looks quite reasonable and I fully agree. It is backed with quite enough valid inputs so output should not be much different than this, perhaps just in some finesses

It is not academic to quote yourself but what the hech, it is really on the table AIM-54 altitude.pdf

You are very right @Gareth Barry with this equation and while with some other motors having small nozzles that simply can be ignored, here with all specificities this can’t be excluded. However these numbers (plus or minus, increase or decrease of thrust force) are not going to come without involving pressures in calculations and your model as much as I know doesn’t include pressure rates when describing some motor. Actually understandable from one perspective and from other, why not to include it if it is on the table. I’m not much about computer-ing but this for sure would be very easy to include. From chamber pressure and nozzle expansion ratio to find what is pressure at nozzle exit. That will be pressure in range of ambient pressure at some 10km so I would put thrust on this altitude as nominal one. That thrust would be so called thrust with full expansion, no loss and no gain of ambient conditions. And from that point this nominal thrust would be changed with (pe-pa)*A where only “pa” is variable and that is piece of cake to make. Ambient pressures are well known and altitude of missile in every second is of course known. There are no linearity here with Phoenix motor so percentages are not precise enough, some other motors can handle percentages easily but here to have as closest to reality, something more have to be done. Average chamber pressure let’s say 45 bar -> nozzle expansion ratio 18,5 -> heat ratio 1,2 -> pressure at nozzle exit 0,256 bar Let’s say it is close to 10km ambient pressure of 0,26491 bar or 26491 Pa, so nominal thrust to be that one or 18318 N. What would be at 2km where ambient pressure is 79497 Pa … 18318+(26491-79497)*0,238^2*PI/4=15961 N

You are welcome, actually it’s so nice seeing someone’s interest in this for me such a fun field of technic. As an engineer working for decades, something what is not boring but I’m kind of saturated with that, and bang, several years ago, also on forum (one other, not this one) , my interest in rocket motors was born. Luckily there was a man who worked all his life with rocket motors, willing to share all he knows, with patience at the beginning…and step by step, book by book, my interest just grew, some knowledge is accumulated of course but because this is indeed specific field of technic and just hobby to me, there are still so many things to learn. There were some good points I believe, there were some completely missed ones which I will always admit, either figured out alone with time or pointed by others * So, interesting hobby made boring living work easier That’s why it’s nice to see someone’s interest, and @Katsu what ever you wish to hear about, if available time and my knowledge allow will be done. Unless forum sheriffs don’t erase and expel us * - this freak of motor is I’m very sure well pointed

But @Katsu don’t change propellant mass, it is always 168kg no matter what thrust is. Altitude change specify impulse and specific impulse multiplied with propellant mass gives thrust

Hey @Katsu Nice to see you're using these numbers. You can even change data for your self...that's surprising to me. Then change active time, take off 3 seconds you gave extra using this average thrust value, although seems as just 3 seconds, that is extra 21 kilograms of non-existing propellant. This motor although seems as relatively simple is actually very tricky and it's quite difficult to make flight model which will be general for all cases. It's not difficult to the measure that it is impossible, everything is possible, however not in case how this program and model is organized, like you said it is simplified and it is understandable. Make it realistic would be such a hard work that anyone normal would gave up right in the start. Eventually one model but how many motors you have in game, that would be finished in next century. Tricky motor-tricky case...this launch which you called deck flight, take off non-existing 3 seconds, change thrust used for 10km altitude with average trust for 1km ( 15532 N ; Isp=223,4s) and you will get completely different picture probably nothing close to what you have in game now. So you saw HARM numbers as well, that one is different on it's way, there are others issues but at least this altitude issues are not so dramatic like in case of Phoenix. Phoenix is in that real pain and from all tactical motors I know, the worst for modelling because of it's widely open nozzle and nonlinear thrust. This deck flight, to show what all can happen, how many variables can appear ... One launch from level flight on 1km at 0,8M, and then after 2 seconds 6G overload for 10 seconds pushing missile upper in rear atmosphere. And with every second drag is in variable of course but thrust is also changing Just with lifting to this final altitude and because of lower ambiental pressure 7% of extra total impulse is achieved compared to what would be in level flight at 1km and missile goes over 1,9M while by using thrust from 1km missile barely reach 1,75M. Complicated motor indeed, not easy to work with, special in many points

First thrust curves for sea level and 10km for reference, Itot=277,5 kNs and Itot=292,5 kNs This is of course weight of propellant with time, initial weight 127kg And Isp for sea level and 10km Your plan 53,3*3,2+8,4*13,5 seems as reasonable, although if we start from pressure rates I'm more for something about 125bar in boost and 25bar in sustain what for ''squared'' profile would be like 47,5*3,5+8,5*13 at sea level and 48,5*3,5+9,5*13 at 10km. Of course decision is yours, this is just thought of mine. Some guys will be disappointed when see values of Isp because it is HTPB and beside that it is American HTPB, but reality and wishes are different. This is non-aluminized propellant, relatively ''cold'' with some 3000K flame temperature, nozzle is as it is, and of course there is no rocket motor which will give theoretical maximum, simply some of total theoretical potential will be inevitable lost, and there are plenty of possible losses

''Red'' model is better to use as sample for consideration of shorter boost-longer sustain. Of course it is connected if propellant type inside is same and I think it is because only TP-H1159 is mentioned as type for HARM. By the way, there is also some doubt is this grain single or there are after all two grains inside. For casting I don't see reason for two grains of same propellant because it looks to me that single one can be done, but who knows. In some similar crosscuts where it is written boost grain and sustain grain (for example in Mk39 Mod.7 motor of Shrike, precursor of HARM) indeed two grains are inside and of two different propellants, Mk58 of AIM-7F also etc etc. I wouldn't be surprised with two grains. Anyway, I modelled it as single grain and for burning used 1,55*p˄0,36 and for all pressure rates. Unfortunately, for us trying to do this, luckily for constructors of motors, burning rates can be with additives modified to be different for different pressure. So 1,55*p˄0,36 is for range of 1000 psi (69 bar) but for 20 bar or 120 bar it can be different burning exponent and response. It's not easy of course to find answers with many open questions but I really think I'm close with these two options, red and blue. Simply with shorter boost, motor would go in pressure rates exceeding normal ones, and longer sustain is possible in this grain configuration only if reduce burning rate, and 20 bar pressure is for me some minimum for proper motor operation, lower than that motor could cough and die. On 20 bar it is only something about 4,55 mm/s of burning speed and that is minimum of minimum for reliable work of motor, or I believe that. If you can, of course I don't have objections, actually I would be glad, try to use these two with your dynamic model to see how it fits to it. Or just one, on principle truth is always somewhere in the middle Falcon's drag is from here -> ''Free-Flight Investigation of the Full-Scale Hughes Falcon Missile, D Configuration, to Determine Aileron Effectiveness and Damping in Roll'' Free-Flight Investigation of the Full-Scale Hughes Falcon Missile, D Configuration, to Determine Aileron Effectiveness and Damping in Roll - UNT Digital Library

Few thoughts about HARM, there is nothing on the internet to be used as solid numbers, I mean how it's motor works in numbers. And I'm kind of stuck with it, seams as close but still final is missing, not sure what to select as final. There are only few crosscut graphics on the internet, and if those would be same then there will be no doubts but one is different then others, and that one is actually the most serious and the most relevant. Where to place second radial stress relief slot? That change everything in complete, would booster be stronger and sustain weaker and longer or weaker booster and shorter but stronger sustain. Obviously 3 graphics are showing that slot is in area of aft launch hook where motor is hardened and that has sense, usually such dividing in grain configuration is around such hardened place. But fourth one shows different, and although it is only sketch I can't not to take it seriously. After all, this one shows what is the most important in this work, grain configuration, half actually more then half is solved when having that. Propellant is known, just common non-aluminized HTPB based propellant, and there are few of such with given characteristics so together with grain configuration and also nozzle geometry which I have measured, it is almost everything on place to have something as output, how it works For sure, it is something of these two. Both are realistic, both are achievable, both are normal Pressure rates are in level of normal, a bit higher in this with stronger booster but still just regular. And this would be force output of these two options at 5km although with nozzle exit diameter of just 128mm there is no some significant gain with altitude It is nearly same total impulse about 285kNs so both should not be much different in dynamic, only distribution in time is different. I made few drop shots just to see where they are compared one to other, some launches from 2, 5 and 10km from horizontal and then gravity and atmosphere work, also some stupid non-realistic ballistic shot That's all close one to other, just slight motion adventage of stronger booster but insignificant. So I stuck, and don't know which one is the one. Almost forget to use sample shot what the Chinese gave ... Obviously they are about ''blue'' one but I'm not sure in that. I'm kind of more on side of ''red'' one...actually I don't know, it is 50:50. Both like said are realistic only I hate when don't have answer. Blue one is a bit more normal with pressures, it has slot where it would be expected to be, but the most relevant graphic shows different...70:30 for red. I would like to hear some thoughts, I know there are members here which knows this matter and which are curious as me. By the way, what you gave to HARM in DCS?

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@henshao Thanks, highly appreciated Unfortunately null, still hidden like snake’s legs. But let’s go on with finding answers, it will appear somewhere sometime. Could be some awkward case when it is hidden so much