The AIM-54 Phoenix missile - Technology, History and Performance

[MiG_23M]

@SE_8749236

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).

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.

@SE_8749236

Also, “travels 22km downrange in 90s” doesn’t mean the missile has landed on the ground, the missile could still be in the air

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.

@SE_8749236

Source please?

AFAIK, according to Math.

Given this:

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.

@SE_8749236

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.

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.

@SE_8749236

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.

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.

[SE_8749236]

I agree with most parts that you’ve said.

@MiG_23M

The diagram of the launcher shoes a 30 degree vertical angle, which is what I launched it at.

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

[MiG_23M]

@SE_8749236

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

The loft profile of the missile will self-correct it to a lower 17 degree angle, we do not know the real world missile loft parameters but it would also self-correct itself.

Given that the real world loft parameters are unknown I suggest we test with a 30 degree launch and no loft profile as well as a 30 degree loft with the in-game AIM-120 loft profile.

@SE_8749236

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

ISP is going to be above 230 in my opinion, but what we don’t know is how much the burn rate changes based on altitude. This is dirty math that may have a negative effect on the test. There are just so many variables that we aren’t able to account for.

[sudo_su1]

@MiG_23M

Flexadyne is closer to 230-240s at sea level for the RDS-5XX series propellants

https://ntrs.nasa.gov/api/citations/19660005237/downloads/19660005237.pdf

[sudo_su1]

@SE_8749236

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.

I think you are overestimating the missile’s lift to drag ratio.
Based on your own calculations (I think you are assuming AIM-54C):

444N zero lift drag + around 2871N lift inducted drag = 3315N

Aerodynamic performance improvement of a canard control missile:

Note that AIM-54 has an extremely low aspect ratio.

Aerodynamic performances of cruise missile flying
above local terrain:

Aerodynamic Shape Optimization of a Missile Using a Multiobjective Genetic Algorithm:

[SE_8749236]

Yes I’m assuming Aim-54C since that one has improved avionics and autopilots.

If we go with 3315N of drag, assuming missile never goes ballistic and total speed loss will be 678m/s.

There are still 768m/s of speed remaining after 1 minute since burnout.

If missile went ballistic with 0 AoA in a portion of its flight (say follow the velocity vector and nose down slowly), then it would have lost even less speed.

None the less, even if we assume it didn’t do anything to minimize drag loss, assuming a constant deceleration for simplicity.
The average speed is still over 1000m/a, the missile would have flown 60km in 1 minute, with speed over Mach 2 and 20000m altitude to spare, which it can use another 10,000m of altitude to glide or dive and maintain Mach 2+ all the way down to at least 10,000m

[SE_8749236]

Sounds good.

[SE_8749236]

@MiG_23M

ISP is going to be above 230 in my opinion, but what we don’t know is how much the burn rate changes based on altitude. This is dirty math that may have a negative effect on the test. There are just so many variables that we aren’t able to account for.

I agree. Sadly I only took physics as hobby in University =(

@MiG_23M

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.

@sudo_su1

https://ntrs.nasa.gov/api/citations/19660005237/downloads/19660005237.pdf

If I use this source, take the lowest Isp=245s at sea level, plus the fuel mass you mentioned, so we can ignore the incorrect end mass of Aim-54C ingame.

Then the dirty Math becomes:
Mass flow rate = 165 / 30 = 5.5s
Isp = thrust / mass flow rate / g
Sea level (Isp=245s) thrust = 245 * 5.5 * 9.81 ~= 13219N

[MiG_23M]

The propellant as tested in a lab does not correlate with the impulse of the in-service ordnance it is used on. Likely because laboratory testing still shows a delivered ISP while maintaining near perfect chamber pressure conditions and without mass production changes to the motor designs.

The AIM-9D for example has 231s impulse

Seeing as it entered production / service around the same time as the Phoenix went to full scale engineering development we can assume small improvements and potentially slightly higher impulse from the Phoenix, as well as better build quality due to size. Hence why I stated 230-240s and why 250+ is unlikely.

@sudo_su1 @SE_8749236
Something to consider is that the nozzle will be overexpanded or underexpanded at sea level depending on which altitude the nozzle was optimized for. (to benefit more from a loft and for the purpose it was built). It is possible the ISP would suffer from a more vacuum oriented nozzle once it reaches lower altitudes.

Seeing as it lofts naturally, to give it the benefit of the doubt a more aggressive profile should be given imo.

[SE_8749236]

Updated dirty math for 230s, 235s, 240s, and 245s, using 165kg as fuel mass, burn time 30s.

Sea level (Isp=230s) thrust = 230 * 5.5 * 9.81 ~= 12409N
Sea level (Isp=235s) thrust = 235 * 5.5 * 9.81 ~= 12679N
Sea level (Isp=240s) thrust = 240 * 5.5 * 9.81 ~= 12949N
Sea level (Isp=245s) thrust = 245 * 5.5 * 9.81 ~= 13219N

[MiG_23M]

The thrust and burn time would likely change, more so just the burn time. I suspect peak and minimum thrust will be similar but the most varied change is in burn time. Either way, I could test this. I’ve been lazy as of late though after grinding out the J-11A, Su-27SM, and J-10A

[SE_8749236]

Thank you before hand. Grind is indeed exhausting. Have a good weekend.

[Lolman345]

So per the latest BR changes the non Fakour armed F-14s are going up and are receiving no buffs at all.

might as well just folder the tech tree F-14A because there is even less reason to use it now given the AIM-54 is now going to be forced to fight against superior AAMs even more.

[malucobeleza171-psn]

3 things
the “New” aim54C engine will come next patch?how much power and burn have?

When the bug that datalink of the missiles change the to missile, instead the missile goes to target goes to the enemy missile will be fixed?

[MiG_23M]

These are probably never going to be fixed

[YeeT_and_Delete]

Well, if Gaijin are indeed working on RCS in anticipation of stealth coming, we might see missiles stop targeting each other as the launching aircraft should have a far higher RCS.
Other than that, I agree with you, I doubt they’ll ever fix the 54.

[Grimtax]

I think RCS, as a basic variable, is already implemented in the game. AFAIK, there should be parameters dictating how RCS scales with aspect angle, although fixed for all aircraft. I have not seen anything specifically setting an RCS value for each aircraft, but I think (this is speculation on my part) each aircraft’s RCS depends on its wing span. Maybe that’s why there used to be problems with MiG-23’s disappearing from radar with its wings swept back.

They might be thinking of adding more stuff to better model RCS. One thing is for sure, though, the 117 would be a really good way to test how low RCS impacts gameplay.

[YeeT_and_Delete]

Yeah I’m aware, I just meant a more believable version of RCS, as what we have now is a joke past 12.0. For instance, I really shouldn’t automatically switch TWS tracks from a plane to a missile or when trying to get an ACM or HMD lock it shouldn’t lock the missile. I also believe the current RCS model in game is disproportionately affected by the speed of the target, as I never have any problems locking missiles.

[malucobeleza171-psn]

Someone could pass to me the source that say about burn time of aim54A/C and thrust ?

[Areidysa]

Can somebody get a primary source that confirms the maximum speed of the AIM-54C?