Comparison by Spurts

New and old developments in aviation technology.
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eloise

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Unread post23 Feb 2020, 03:36

sprstdlyscottsmn wrote:I see what you are saying. Per my previous post about the SPEAR window, I can't justify it going lower that 0.05, but you have a decent argument that SLAM-ER should be in the same class, not half the size.

Another detail I want to suggest is
Stuart said the company is evaluating multiple sources for the aft actuator solution and also for the new rocket motor design that, Jane's understands, is expected to deliver an engagement speed that is double that of the current AARGM. "Our assessment is that there are propulsion options out there that are high TRL and can quickly transition into a production scenario to meet the USN's timelines," he said.

While the propulsion type has yet to be decided, a ramjet solution has not been discounted. "The current Orbital ATK design concept is not a ramjet, but it certainly doesn't remove that potential. However, it will be the USN and its requirements office that make the final decision on where they want to go with propulsion," he said.

'Increased Survivability' is built into the AARGM ER requirement, although Stuart declined to comment on the specifics of the Orbital ATK solution, noting only that "speed is in the equation. We're going double the range in about the same amount of time, and you have to increase speed to achieve that; so speed in and of itself is an improvement to survivability. There are other aspects of our design solution that improve survivability, but these are not releasable".

https://www.janes.com/article/71285/orb ... gn-concept
AARGM is mach 2 - 150 km missile, So if AARGM-ER can fly 300 km in the same amount of time, I think it will reach Mach 4 (or have much higher cruising speed than AARGM, but AARGM-ER doesn't have ramjet motor so Iam more inclined that it is much faster)
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Unread post23 Feb 2020, 05:23

eloise wrote:
sprstdlyscottsmn wrote:I see what you are saying. Per my previous post about the SPEAR window, I can't justify it going lower that 0.05, but you have a decent argument that SLAM-ER should be in the same class, not half the size.

Another detail I want to suggest is
Stuart said the company is evaluating multiple sources for the aft actuator solution and also for the new rocket motor design that, Jane's understands, is expected to deliver an engagement speed that is double that of the current AARGM. "Our assessment is that there are propulsion options out there that are high TRL and can quickly transition into a production scenario to meet the USN's timelines," he said.

While the propulsion type has yet to be decided, a ramjet solution has not been discounted. "The current Orbital ATK design concept is not a ramjet, but it certainly doesn't remove that potential. However, it will be the USN and its requirements office that make the final decision on where they want to go with propulsion," he said.

'Increased Survivability' is built into the AARGM ER requirement, although Stuart declined to comment on the specifics of the Orbital ATK solution, noting only that "speed is in the equation. We're going double the range in about the same amount of time, and you have to increase speed to achieve that; so speed in and of itself is an improvement to survivability. There are other aspects of our design solution that improve survivability, but these are not releasable".

https://www.janes.com/article/71285/orb ... gn-concept
AARGM is mach 2 - 150 km missile, So if AARGM-ER can fly 300 km in the same amount of time, I think it will reach Mach 4 (or have much higher cruising speed than AARGM, but AARGM-ER doesn't have ramjet motor so Iam more inclined that it is much faster)

That one I will disagree with on the principles of physics. It is pure speculation that it has the same time of flight. Even if we say the new missile has half the drag of the old missile, it would only have 41% more speed/range for the same thrust/time/fuel mass. To have twice the speed even with half the drag coefficient would be 2 times the thrust, which would need 2 times the fuel. AARGM ER is not a larger missile than AARGM and has the same guidance and warhead, so there is nor feasible way for it to carry twice the fuel.
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Unread post23 Feb 2020, 07:08

sprstdlyscottsmn wrote:That one I will disagree with on the principles of physics. It is pure speculation that it has the same time of flight. Even if we say the new missile has half the drag of the old missile, it would only have 41% more speed/range for the same thrust/time/fuel mass. To have twice the speed even with half the drag coefficient would be 2 times the thrust, which would need 2 times the fuel. AARGM ER is not a larger missile than AARGM and has the same guidance and warhead, so there is nor feasible way for it to carry twice the fuel.

But AARGM-ER is a larger missile with wider diameter than AARGM
AARGM rocket motor diameter is 254 mm
AARGM rocket motor diameter is 290 mm
If the length of the rocket motor section is equally long, AARGM-ER will carry 29% more rocket fuel, but they removed the mid body wing/actuator section, so I think it is feasible for it to carry twice the fuel load.

17EBD85B-127B-4B3D-A689-6AE3B6866645.jpeg

E2987019-EF1C-48EA-952B-18A4C75E5804.jpeg

17CAF9BF-8EFA-49EF-A8C7-D4199B97031E.png

A165AE79-3526-47FD-A0E8-634A60EBA5E0.png
Last edited by eloise on 23 Feb 2020, 18:44, edited 1 time in total.
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sprstdlyscottsmn

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Unread post23 Feb 2020, 15:42

The new propulsion section would need to be over 50% longer than the old one. Looking at the space between the find on the old one, and the removed control section, that might just be it.

Thank you for taking the time to go over your evidence with me on this, as it ended up causing my rebuttal to line up with your argument. Provided, of course, that the missile has half the drag coefficient by ditching the big fore wings.
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Unread post23 Feb 2020, 18:46

sprstdlyscottsmn wrote:The new propulsion section would need to be over 50% longer than the old one. Looking at the space between the find on the old one, and the removed control section, that might just be it.

Thank you for taking the time to go over your evidence with me on this, as it ended up causing my rebuttal to line up with your argument. Provided, of course, that the missile has half the drag coefficient by ditching the big fore wings.

Thank you for the great explaination too.
By the way, when we talk about mach 2 speed for AARGM and mach 4 speed for AARGM-ER, is it top speed or average speed?
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Unread post23 Feb 2020, 18:50

Sprts,

you're the best! :notworthy: :notworthy:
Russia stronk
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Unread post23 Feb 2020, 20:04

If fired from a good cruising altitude with a loft profile then there will not be as much speed lost. I treat it as an average speed for that reason. I do not go into as much investigation for the AG missiles as I treat them as fairly static, as their targets are static.
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Unread post24 Feb 2020, 10:32

sprstdlyscottsmn wrote:If fired from a good cruising altitude with a loft profile then there will not be as much speed lost. I treat it as an average speed for that reason. I do not go into as much investigation for the AG missiles as I treat them as fairly static, as their targets are static.

I find that Kh-15 has very similar kinematic specs with AARGM-ER
Kh-15 max range is 300 km, AARGM-ER max range is also 300 km
1ja1o.jpg

t3ULL.jpg

1.PNG

Kh-15 can climb to 40 km and reach Mach 5 in the final dive at target, I don't know if AARGM-ER is capable of the same thing, so I look closer
Kh-15 propellant is 44% of its length, Kh-15 is 478 cm long and 45.5 cm in diameter so the propellant volume is 3.42×10^5 cubic centimeter
AARGM-ER propellant is 49.6% of its length, AARGM-ER is 410 cm long and 29 cm in diameter so the propellant volume is 1.34×10^5 cubic centimeter
So Kh-15 carries 2.55 times more rocket propellant than AARGM-ER. But, Kh-15 diameter is 45.5 cm while AARGM-ER diameter is 29 cm so the cross section area of Kh-15 is 2.46 times greater than AARGM-ER. Because form drag is proportional to cross section area, AARGM-ER can reach the same speed as Kh-15 even though it carries less propellant. Is that reasonable ?
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Unread post24 Feb 2020, 14:25

the "drag is proportional to cross sectional area" is a bit of a misnomer, but it can be useful for first order approximations.
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Unread post25 Feb 2020, 03:30

sprstdlyscottsmn wrote:Here is the comparison currently. I am working on the F-16 model now.

Strike Fighters 2025_4.pdf

I have another question about these specs of these air to air missiles
Why is the boost time of MiCA, R-77-1 and AIM-9X so long?
Mica can boost almost as long as the sustain time of Meteor?
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Unread post25 Feb 2020, 15:54

eloise wrote:I have another question about these specs of these air to air missiles
Why is the boost time of MiCA, R-77-1 and AIM-9X so long?
Mica can boost almost as long as the sustain time of Meteor?

Those missiles are using single impulse motors, "boost-only", and have no sustaining charge. I try to assume this is the default motor condition of AAMs unless it is specifically stated otherwise or the listed performance specs are unobtainable otherwise.

Also, the Sustain time of the meteor is the minimum time, and it CAN sustain for ten times as long by throttling back.
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Unread post25 Feb 2020, 17:01

sprstdlyscottsmn wrote:Those missiles are using single impulse motors, "boost-only", and have no sustaining charge. I try to assume this is the default motor condition of AAMs unless it is specifically stated otherwise or the listed performance specs are unobtainable otherwise.

Also, the Sustain time of the meteor is the minimum time, and it CAN sustain for ten times as long by throttling back.

I get that, but except for Meteor and AIM-120D I feel like the boost and sustain time of the others are too long
I mean AIM-120 can boost for 7 seconds but MICA can boost for 20 seconds?
4EBE0DEA-74AC-4DE9-BF52-C8EE54D3784E.jpeg

C6ABAF22-16AC-4B89-BED7-38E397876D10.jpeg
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Unread post25 Feb 2020, 17:20

eloise wrote:I get that, but except for Meteor and AIM-120D I feel like the boost and sustain time of the others are too long
I mean AIM-120 can boost for 7 seconds but MICA can boost for 20 seconds?

AIM-120 boost only for 8s, not 7, and at nearly 4,500lbt. It gets to Mach 4 in about 3nm. It uses loft in order to get its range.

MICA has a 20s motor, yes, but with only 1,485lbt it takes 7nm to reach Mach 4. Even with loft it does not come anywhere close to the range of the AIM-120D because of the high drag fins on a lightweight missile (see it's crazy high Dogfight score?). I did not like what I had to do with the MICA, but it was the only way I found to get the kind of range it is reported to have.

My missile model requires me to make a LOT of assumptions and I have to play with a lot of parameters to get the reported performance, since motor information is generally non-existant.
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Unread post25 Feb 2020, 17:43

for example, if I change the MICA motor to 8s at 3700lbt and increase loft to 25 degrees (same burn time and loft as AIM-120D) it actually loses range and it's speed goes to over Mach 5 (in 4nm).

If I leave loft alone and change it to 2s Boost at ~5600lbt and 10s Sustain at ~1800lbt the top speed goes up a little but it still solidly in the Mach 4 range, but it still loses flight range. In effect, with a 20deg loft the MICA needs to still be doing Mach 4 from 9NM on to reach 80km flight range in under 180s. No matter how I slice it, it needs 20s of motor burn time to get there. Even 2s boost and 17s sustain wont reach the range needed.

Don't get hung up on the terms "boost" and "sustain". Sustain only applies if there are two thrust levels. For a given ISP and Fuel Weight, there is only so much "delta V" available. The use of single pulse or duel pulse thrust levels only change HOW the delta V is applied.

Case in point, two 20s motors for MICA, with a "boost/sustain" thrust ratio of 3, a 2s/18s boost/sust time split results in the boost phase burning 12.5% o the fuel per second while the sustain phase burns 4.2% per second. a 20 "Boost" burns 5.0% of fuel per second. Both provide 29,700lbt-s (110lb motor with 270 ISP)
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Unread post25 Feb 2020, 17:56

I see your reasoning but I think the range value on internet may not be correct.
For MiCA I think you can calculate the motor burn time from this video
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