Given that PL-15 length of 4m and diameter 203mm, even if we treat it as perfect cylinder filled with solid fuel, with no voids.
The volume for propellants are 0.13m^3
Aim-54 with diameter 380mm and, even if we assume it’s motor section is only 1/3 of its length, it still has more volume, 0.15m^3, for propellants than the most unrealistic overestimate of PL-15’s propellant.
A slightly more realistic estimate of PL-15’s propellant, say 3m rocket motor, means it has volume of ~0.1m^3
Unless there is some magical advance in solid fueled rocket efficiency, this shows that Aim-54 is seriously underperforming at high alt.
129.12 - 89.30 = 39.82 in = 1.011428 m
1.011428 * pi * (0.381 / 2) ^ 2 = 0.11531207973 m^3
And keep in mind, this is the external volume of the propulsion section of the missile.
The internal volume of the rocket motor will be lower (and is not necessarily comparable between the two missiles).
Furthermore, there is hollow space inside the propellant grain … You can’t assume that the empty space inside the propellant is similar between PL-15 and AIM-54’s motors.
We had the argument about AMRAAM weight, the same pertains to the Phoenix. It could easily be a modified AIM-54A or one equipped with the MK60 motor that was referenced. Either way, if it is the AIM-54C it is worth noting that the AIM-54A would have larger less advanced seeker technology as well.
2007
They calculated most scenarios for mach 2 launch.
While the data was based on information that meant it is not usable for a report on the AIM-54’s top speed, it was quite clear the intent was to utilize the missile as a testbed for hypersonic research. The calculations even though not quite correct show us that the missile is certainly capable of more than 4.3 mach as claimed previously. That measure came as a datapoint from a lower speed and possibly lower altitude launch and was spread erroneously as the maximum “top speed”.
I am not dodging anything, and yes if you want anyone to take the statement seriously you need to provide sound logic, reason, and back it up with evidence. You have none of the puzzle pieces here.
Absolutely not.
The AIM-54 uses quite a lot of ablatives to ensure safe operation of the motor and longer shelf life. Modern missiles do not use anywhere close to this amount of ablative, if at all. The AIM-54 is a late 1950s and early 1960s design. The XAIM-54A was first tested in 1963 and was ready for production but was waiting for a flying platform to be serviced on. Once the F-14A entered service, so did the AIM-54 with only minor changes to fuzing and other parts for reliability concerns.
Thinking that the PL-15 could not vastly outrange the Phoenix due to size when there is a 60 year gap in missile technology between them is crazy.
Additionally, the ISP of the motor is going to be vastly different. You’re talking two or three generations of propellant difference between the two. Modern high performance propellant is going to have more than 50% higher specific impulse for the given weight and better density as well.
You are the one that claims that its fine and even overperforming while there are a bunch of people that even main that aircraft that tell you that its broken.
So a bunch of people who play the game in a video game are saying that it doesn’t perform as it should… according to what?
Yes, I did say it is overperforming in certain aspects but this isn’t one of them. The top speed is underperforming. What I am telling you is that according to real world datapoints - it overperforms at sea level in regards to range and underperforms in speed at altitude (but meets the correct range and time to target for maximum launch range conditions). It’s not black and white.
So with a launch at mach 1.93 it reaches mach 4.6 momentarily and then it drops. The target is at 15000m and im at 12000m as you said.
Having said that, do you think its supposed to reach this speed only when its given such ridiculous parameters? The weapon supposed to intercept cruise missiles that are skimming the surface of the water according to your sources and as I have demonstrated, in that role even something as “bad” as the sparrow would be better suited since the in game phoenix is both very slow and also loses whatever speed it gained very quickly against a low flying target, even without any maneuvers.
Missiles like the sparrow, the 27 - 27ER, or amraam, reach close to if not their top speed even when fired in these parameters. How do you explain that then?
Thrust is correct, burn time is lower than anticipated and overall deltaV seems to be underperforming a little bit because Gaijin did not model the high altitude thrust quite right according to documents provided by @sudo_su1 that show the missile can indeed burn upwards of 40s.
So, knowing this my stance has changed slightly than it was in the past. The high altitude maximum launch range scenario is partially correct. It meets the target in the correct distance and time traveled. The top speed in this is much lower than it should be, and the speed loss after burnout is also much less than it should be.
Essentially, the missile should burn longer at higher altitudes and shorter than it does at lower altitudes. This is causing a discrepancy in top speed at higher altitudes but also overperformance in regards to drag at low altitudes. Excessive low alt range, suboptimal speeds at high altitudes. Hope this makes some sense.
The problem summed up in a few parts:
Drag
Since Gaijin does not have dynamic drag values, they cannot reduce drag during motor burntime. The current thrust is accurate, and does not seem to be increased to simulate the reduced drag during motor burn time that they did for the AIM-7F/M. The devs have been hit or miss on how they model ordnance lately.
Thrust
Gaijin does not have dynamic thrust, meaning that motors do not vary in thrust based on altitude or climatic conditions. This means that if a missile is modeled for high altitude, it will overperform in thrust at sea level conditions. Hence why Gaijin has modeled most missiles for mid-altitudes between 0 and 5km or in some niche cases as the AIM-54, for a specific high altitude launch scenario.
Burn time
Similar to thrust, burn time varies. This one would need to be tailored per missile and not using an over-arching formula. This would be tedious to find the correct documentation for and would result in more widely varying performance based on altitude than what we currently see. It would complicate their launch zone diagrams for the radar scope as well.
Atmospheric drag
High altitude drag is not properly modeled, missiles do not benefit as much from a high loft profile as they should and top speeds achievable at those altitudes are not done in-game due to this. Since the AIM-54 is modeled for the high alt launch scenario and the drag needs to be lower than expected to meet it - the lower altitude performance is higher than expected as well.
The game is too oversimplified to have a perfect AIM-54. It is not able to be simulated nearly as well as in flight sims such as DCS. (They have their own problems with this of course, and are not better by ANY means)…
There simply exists much more information and datapoints from which Gaijin can model the R-27ER, AIM-7, and AMRAAM. They also feature newer propellants with lower burn times and lower ranges. Modeling them for medium altitudes brings them closer to high altitude datapoints and prevents them from overperforming at low altitude at the same time. This is why the AIM-7F overperforms as much as 15-20% and why the AMRAAM underperforms by as much depending on scenarios. The R-27ER underperforms by as much as 25% in some scenarios.
I see, I guess I didn’t see this or read it fully. In that case everything else is still true but the burn time issue is no longer valid. The top speed issue is from lack of reduction in drag during motor burn time (especially important for longer burn time and larger caliber missiles). As well as the compounding issues of the game lacking dynamic thrust, drag, and incorrect atmospheric conditions in higher altitudes.
Without these, it is tailored towards a single datapoint that is causing performance issues at all other launch conditions which is to be expected.
Hence (among other reasons) why I think the updated 2023 thrust values by NASA for the Improved Orion (Improved Hawk) are valid, despite the Isp value that those figures result in being higher than normal. (which is already the case in the game for AIM-7F, for a similar reason)
They aren’t correct for the reasons given to you by the devs, the specific impulse of the motor is given. The burn time is given. The fuel mass is given. Those thrust values are impossible.
I would like to quote more details from that source.
The Phoenix only attains Mach 5 from Mach 2 when launch launched level (no manual loft), at alt of 48,000ft (~14630m).
The source also include a diagram of altitude over time and Mach number over time, this indicate the missile is capable of traveling above Mach 3 for over 60s.
But it doesn’t necessarily meet altitude over time, aka trajectory shaping,.
In the era where Energy–maneuverability theory were accepted into military, at least Aim-54C should have stored its energy as gravitational potential energy by aggressive lofting.
I know this is from Sea Phoenix test, however, I came across this as well:
Tests of the surface-launched Phoenix missile included a firing from what was then known as Naval Weapons Center China Lake, in California, during which a standard version of the missile traveled a distance of 13.5 miles in 90 seconds. This test, however, was less concerned with evaluating end-to-end performance than it was the separation of the missile from its launcher, as well as safety aspects. If they did occur, no other such tests appear to have been documented.
Do we have data on what angle the Sea Phoenix test was launched at? If they were concerned with safety scenario, say Phoenix fell to the ground after lift off, then they won’t launch it to demonstrate performance, instead they probably launch it like, for example, at 70 degrees above horizon and make it fly ballilstic (guidance turned off to avoid autopilot goes HAL).
Then we get the 13.5miles/22km down range not because missile motor’s performs bad at sea level, but simply due to how the launch was setup and it wasn’t intended to fly far.
Also, “travels 22km downrange in 90s” doesn’t mean the missile has landed on the ground, the missile could still be in the air
Inital mass = 463kg
End mass = 293kg
Propellant mass = 463 - 293 = 170kg
Mass flow rate = 170kg / 24s = 7.08kg/s
Isp = F / mass flow rate / g = 17793 / 7.08 / 9.81 = 256s
That’s actually whoppingly good.
This is on par with the HTPB.
We need direct proof that Aim54’s solid fuel has really bad Isp, since the quote “the only definitive data sources we have regarding the AIM-54’s motor performance for any variant” endquote + Math says the Isp is very good.
There are four possibilities I can think of:
The source is wrong
The Math is wrong
The claim that Aim54’s solid fuel has low Isp is wrong.
Or the end mass is wrong.
Even if we use 258kg (from a random reddit post) as end mass, the Isp is still 212s.
Also, surprisingly, dV increases if we have lower specific impulse due to lower end mass.
Isp of 212 + end mass 258kg => dV ~= 1216m/s
Isp of 256 + end mass 293kg => dV ~= 1149m/s
(In game it is 258s + end mass of 293kg, dV ~= 1157m/s. So the Isp in game is mostly fine)
This further proves my point: it doesn’t matter the missile is 60 years old or not, only delta V matters at high alt. If it have same dV when at very high alt where drag doesn’t really matter and flies similar trajectory, it’s gonna has similar range as latest state of the art missile.
Drag matters.
If there is enough air for the missile to create lift to fly, then there is also enough air to slow it down … You can’t have one without the other …
I know that, but the drag is so miniscule and it won’t slow the missile down significantly. For example, when flying at altitude of 30,000m, air denstiy = 0.018.
This means the missile is only experiencing less than 2% of the drag it would have were it to traveling at similar speed at sea level. (0.018 / 1.225 ~= 1.5%)
If we plug in numbers.
Mach 5 at 30,000m + drag coefficient of 0.2 + mass of 293kg
v = 1475
Area = 0.1134m^3
drag = 0.018 * 0.2 * 0.1134 * 1475 * 1475 * 0.5 = 444N
Basically no drag since gravitational force at this point is 2871N.
The missile only needs to glide at around 9 degrees below level to compensate for most of the drag.
Let’s exaggerate this say missile flies for 60s with 2000N of drag force, total impulse from drag is 120,000Ns and translates to a decrease of ~409m/s.
The missile would still fly at over 1000m/s, meanwhile it had covered a ground distance of at least 60km, not including the distance covered during boost; and it only lost about 9400m of altitude in that 9 degree glide. sin(9) * 60,000 = 9386m. It still has 10,000m at disposal before hitting denser atmosphere.
The ability to glide at over Mach 3 for over a minute is the secret sauce (in addition to being ARH) that makes Aim-54 having superior range and extremely deadly in the 70s.
The battery is Phoenix’s limitation, not the kinematics. This is similar to the limitation of Aim-120, except the later variant (like 120D) where Raytheon constantly advertised it magically gained 50-100km range without any change in specific impulse or aerodynamics, while in fact they just swapped in a better battery that holds more charge and allow missile glide further at subsonic speed.
The diagram of the launcher shoes a 30 degree vertical angle, which is what I launched it at. They also said it was a 100% untouched, unmodified Phoenix in any way. It was an off-the-shelf example slotted and launched.
That is true, but the in-game model travels further in the same amount of time which suggests motor or drag overperformance (or both), which agrees with my assessment earlier about how it was modeled.
17,000 newtons isn’t for 24+ seconds. 17,000 newtons is generally given the Mk60 motor alternative not seen in-game, and for around ~20s. Flexadyne is closer to 230-240s at sea level for the RDS-5XX series propellants, which are also utilized by the AIM-9C/D and other motors.
In-game we have 14,350 for 30s, and that is in-line with the sources used. Though I will say DSplayer has not updated the sources list for QUITE some time. It must be realized that this performance is already for high altitude, where ISP would have increased due to increase in exhaust velocity from the reduction in ambient pressure.
Math showing 257-266s impulse is correct for the in-game thrust and burn times;
Spoiler
AIM-54A (correct weight)
Initial Mass = 443.613
End Mass = 273.063
Propellant mass in-game = 170.55kg (376 pounds)
Real propellant mass fraction = 364 pounds (11 pounds of ablatives are accounted for in WT)
Mass flow rate of correct weight AIM-54;
170.55 / 30 = 5.685kg/s
Mass flow rate not including excess ablatives in formula;
165 / 30 = 5.5
AIM-54A (correct weight)
Isp = F / mass flow rate / g = 14350 / 5.685 / 9.81 = 257
Isp = F / mass flow rate / g = 14350 / 5.5 / 9.81 = 266
I don’t really care to do the math and figure out what the thrust and burn time should be at sea level, but if it maintains the higher altitude efficiency at 266s down to sea level, you can see why it is “overperforming” in that regard.
The source used for that explanation was wrong, therefore the math is wrong, the claim that is has low ISP is correct because it is early 60’s CTPB utilized in a number of other projects, the end-mass of the AIM-54C is incorrect but it is correct for the AIM-54A. The fuel fraction is correct. McGregor tells us (as well as the yellow book for hazardous explosives) that the fuel mass is 364 pounds for the AIM-54A’s mk47 motor or ~165kg.
Without delving into this conversation too much, the switch to a new motor on the AIM-54C was only known because they switched to reduced smoke. They continued making newer propellants for the Mk36 and the AIM-120 long after the last public acknowledgement of a motor change.
They can get away with these kinds of improvements because like with the Mk36, it was improved over time from AIM-9D to AIM-9L and then was only really discussed that it was being changed as they swapped to reduced smoke there as well.
Even the reduced smoke motor for the AIM-54C was poorly documented and not well known except for some budgetary discussions.
Anyhow, the AIM-120 being flown in a more ballistic manner would not be able to effectively utilize the extra range. It was claimed that it could technically be fired straight up and then dive on a incoming head-on target and effectively “intercept” it when launched at 250km range but this really isn’t impressive since the horizontal distance covered by the AIM-120 isn’t as much as a more optimal path that reduces time to target at closer launch ranges.
I only cautiously agree with this part, only if we can confirm that the 22km ground launch test was indeed conducted by firing at 30 degrees.
The issue is I’m struggling to find the angle they launched during the Sea Phoenix test; instead I found secondary source claiming the launch has safety consideration and wasn’t meant to demonstrate the performance.
We know the diagram exists and also know the program didn’t get to the mock up and prototype stage, all of the tests were function validation.
e.g. Launch Phoenix from stationary, install AWG-9 on ship and see if it works.
But that means they were quick dirty tests and, although we may find secondary source, accuracy and usefulness in determining performance is questionable without more details on the actual setup.
Given the unlikely hood of finding information on exact Sea Phoenix test setup, I propose we do a simple test.
I did the Math for thrust at sea level (but I don’t know how to use CDK).
Assuming Isp was reduced to 230s at sea level (dV becomes 1031m/s with ingame initial/end mass).
We know Isp = thrust / mass flow rate / g
Thus sea level (Isp=230s) thrust = 230 * 5.67 * 9.81 ~= 12785N
If you have time, you can repeat that 30deg launch test while reducing Aim54’s thrust to 12785N.
If actual test were condcuted with launch at 30deg, then missile in game should have traveled around 25km in replay at T+90s.
displacement = ground distance covered / cos(launch angle) = 22 / cos(30deg) ~= 25.4km
