Comparison by Spurts

New and old developments in aviation technology.
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garrya

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Unread post07 Nov 2020, 04:15

sprstdlyscottsmn wrote:So I was finally able to sit down and update my Meteor model. I used the boost/sustain fuel data from garrya and rewrote my throttle logic to more closely target a set cruise speed (used to be "hold current speed unless we can go full throttle to impact" effectively) within the limits of the throttle (7.5TDR used). I then noticed something troubling. While I had previously modified my thrust model to allow for conditional throttling I had failed to adjust my fuel burn. My model was only allowing a single ISP, which for the Meteor was the Ramrocket ISP of 795. This combined with my boost/sustain transition being time based meant I was only using 1/3 of the boost motor fuel in the boost phase and the rest was being added to the sustain phase.
What an embarrassment.
I fixed that so that the ISP shifts from 265 for boost to 795 for sustain.

IMHO, that ISP for sustain stage is rather low: the common figure I saw for ramjet is 1000-2000
Specific-impulse-kk-20090105.png

India estimate the ISP of their reverse engineering Meteor to be 1000-1200s
india ramjet missile.jpg


In a solid-fuel ramjet, air from the inlet flows through the "pipe" of fuel (also known as a "fuel grain"), which burns along its length. Unlike solid rocket propellant whose formulation is approximately 20% fuel and 80% oxidizer, the solid ramjet fuel is 100% fuel and obtains oxidizer from air, with the result being approximately four times the specific impulse (the product of thrust and time divided by propellant weight) as compared to solid rocket propellant

https://www.globalsecurity.org/military ... a/sfdr.htm
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sprstdlyscottsmn

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Unread post07 Nov 2020, 04:46

I strongly considered it, and I may still change it, but the old spec i saw nearly a decade ago was along the lines of "3 times the ISP of a traditional rocket" vs your sources which say 4 times. Was my figure underestimating? Is your figure a result a recent advances in ram rocket tech? I can't say for sure either way. I'll sleep on it and I appreciate the additional sources beyond the Indian display.
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garrya

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Unread post07 Nov 2020, 06:34

sprstdlyscottsmn wrote:I strongly considered it, and I may still change it, but the old spec i saw nearly a decade ago was along the lines of "3 times the ISP of a traditional rocket" vs your sources which say 4 times. Was my figure underestimating? Is your figure a result a recent advances in ram rocket tech? I can't say for sure either way. I'll sleep on it and I appreciate the additional sources beyond the Indian display.

BTW, I found additional source for the mass flow turndown ratio
A3M prototype:
Mass flow turn down ratio > 1:10
A3M.png

Meteor:
Mass flow turn down ratio > 1:12
Meteor.png
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sprstdlyscottsmn

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Unread post07 Nov 2020, 13:43

What is this document?

Just to nitpick the verbiage, a TDR greater than 10 COULD be achieved and it COULD be in excess of 12.
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Unread post07 Nov 2020, 17:42

sprstdlyscottsmn wrote:What is this document?

Image


sprstdlyscottsmn wrote:Just to nitpick the verbiage, a TDR greater than 10 COULD be achieved and it COULD be in excess of 12.

TDR greater than 10 is for the A3M technology demonstration program
demonstration.PNG

TRD greater than 12 is gained by experience from M1 stage of Meteor development
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sprstdlyscottsmn

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Unread post07 Nov 2020, 23:06

Oh wow. That will really change the max powered altitude.
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marauder2048

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Unread post08 Nov 2020, 00:06

garrya wrote:
sprstdlyscottsmn wrote:So I was finally able to sit down and update my Meteor model. I used the boost/sustain fuel data from garrya and rewrote my throttle logic to more closely target a set cruise speed (used to be "hold current speed unless we can go full throttle to impact" effectively) within the limits of the throttle (7.5TDR used). I then noticed something troubling. While I had previously modified my thrust model to allow for conditional throttling I had failed to adjust my fuel burn. My model was only allowing a single ISP, which for the Meteor was the Ramrocket ISP of 795. This combined with my boost/sustain transition being time based meant I was only using 1/3 of the boost motor fuel in the boost phase and the rest was being added to the sustain phase.
What an embarrassment.
I fixed that so that the ISP shifts from 265 for boost to 795 for sustain.

IMHO, that ISP for sustain stage is rather low: the common figure I saw for ramjet is 1000-2000


It's completely consistent with the theoretical and practical ISP for ducted rockets.
HSAD had 850 seconds* as a reach goal. Along with a TDR of 10:1.
Neither were apparently attained back in 2008. It's why you should be wary of "could."


*2002 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program
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Unread post08 Nov 2020, 16:42

So I just looked at a high/fast launch (50,000ft 1.5M) vs a high target (75,000ft). Even a TDR of 7.5 allows for flight at ~24km (80,000ft) without overly exceeding the stated cruise speed of 4+M for production Meteor (4.08 near the end). I see no reason to increase it at this time.

As for the 1000-2000ISP for Ramjets, I am concerned that some of these other ducted missiles are only superficially similar to Meteor. I am not yet comfortable with increasing the ISP for my model, but I thank you for your inputs and datapoints garrya. You have been a huge help with this latest iteration of the comparison
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garrya

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Unread post08 Nov 2020, 20:01

marauder2048 wrote:It's completely consistent with the theoretical and practical ISP for ducted rockets.
HSAD had 850 seconds* as a reach goal. Along with a TDR of 10:1.
Neither were apparently attained back in 2008. It's why you should be wary of "could."
*2002 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program

IMHO, HSAD isn't comparable to Meteor. HSAD was a technology demonstration program to find a way to improve HARM, the whole development till the end flight demonstration is within 42 months (3.5 years). Whereas, the development of Meteor start with A3M take about 10 years till the first flight demonstration and another 10 years till the development and qualification of Meteor is finished. So MBDA do have more time to fine turn their missile, and the value of the contract is likely much higher as well. Moreover, the estimation for A3M was a turn down excess 10:1 , after A3M evolved into EURAAM then into Meteor M1 then into Meteor M2, they estimated that the turn down ratio can be extend beyond 12:1. If a turn down ratio of 10:1 isn't practical, they must have figured out by the time EURAAM was tested, it would be quite illogical for them to believe the turn down ratio could be extend beyond 12:1 if they unable to get even 10:1 ratio. Furthermore, according to Bayern Cherm, the performance of Meteor M2 motor was proven in numerous test.
Btw, I have some free time yesterday so I re-read Hewitt dissertation and figure out some interesting details that I didn't pay attention to the first time I skimmed the documents:
To start with, the low L/D ratio of GQM-163 make it more challenging for the fuel and air to reach a fully mixed stage before exist the nozzle.Thus reduce the combustion efficiency. This is partly due to the fact that GQM-163 will eject its booster when it reach the required velocity.
GQM-163.PNG

By contrast, the integrated booster/combustion chamber of Meteor will have very high L/D ratio, hence the fuel burning process can be more efficient.
meteor cutaways.PNG


In addition, when I first skimmed the dissertation, I was under the assumption that the thermal growth of the valve will make the valve hole bigger, therefore reduce the maximum turn down ratio that can be achieved. Turn out, it was the opposite, when the valve heat up, it reduce the effective flow area along with the . Hence it actually reduce the fuel flow rate.
thermal growth.PNG


Furthermore, the dissertation also mentioned that the combustion efficiency of Boron added fuel can be improved by coating the particles or adding some special ingredient. However, that wasn't considered in their research because that isn't what they want to find out. However, if we look at the enhancement in Meteor M2 stage over M1, they do some preprocessing of Boron power and adding some ingredient to enhance combustion efficiency
boron addictive.PNG

boron meteor.PNG
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garrya

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Unread post08 Nov 2020, 20:11

sprstdlyscottsmn wrote:So I just looked at a high/fast launch (50,000ft 1.5M) vs a high target (75,000ft). Even a TDR of 7.5 allows for flight at ~24km (80,000ft) without overly exceeding the stated cruise speed of 4+M for production Meteor (4.08 near the end). I see no reason to increase it at this time.

the high TDR is to keep Meteor Mach speed below Mach 3.5, if it sustain Mach 4, the nose will get too hot
sprstdlyscottsmn wrote:As for the 1000-2000ISP for Ramjets, I am concerned that some of these other ducted missiles are only superficially similar to Meteor. I am not yet comfortable with increasing the ISP for my model, but I thank you for your inputs and datapoints garrya. You have been a huge help with this latest iteration of the comparison

I'm glad that my contribution can be helpful for your simulation
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sprstdlyscottsmn

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Unread post08 Nov 2020, 21:00

garrya wrote:the high TDR is to keep Meteor Mach speed below Mach 3.5, if it sustain Mach 4, the nose will get too hot

I know that was mentioned at length in the prototype documents, but in the first link I gave on my post at the end of the previous page it specified a 4+M cruise speed for the operational missile.
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Unread post08 Nov 2020, 23:17

garrya wrote:
IMHO, HSAD isn't comparable to Meteor. HSAD was a technology demonstration program to find a way to improve HARM, the whole development till the end flight demonstration is within 42 months (3.5 years).


Those timelines were attained by leveraging the experiences with Coyote which was under development
when ONR did their analysis.

Quite why that would change the theoretical and practical ducted rocket ISP is not clear.
850 secs was a very aggressive reach goal. I've haven't seen anything in the literature in recent years
to suggest it's really possible to greatly exceed this figure in practice.


garrya wrote:By contrast, the integrated booster/combustion chamber of Meteor will have very high L/D ratio, hence the fuel burning process can be more efficient.


Hewitt says they see combustion efficiencies close to 95% in practice.
So it's not really about improving thrust. The main goal of the dissertation is to reduce
signature and to minimize hotspots in the combustor. The preferred mechanism for doing that is
improved flow management through hardware devices es e.g. flameholders and vanes.

A non-IRR like Coyote has the volume to do this but this would be very hard to do in Meteor's confined
volume; improved fuel formulations are correctly and clearly identified as a secondary option but it would
pretty much be Meteor's only option.

For Meteor, signature reduction is crucial but it is still quite a smokey missile from the footage I've seen.
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Unread post11 Nov 2020, 20:40

sprstdlyscottsmn wrote:I know that was mentioned at length in the prototype documents, but in the first link I gave on my post at the end of the previous page it specified a 4+M cruise speed for the operational missile.

The aerodynamic heating that Meteor sustain is > 500°C, I think that cap the sustain speed at Mach 3.5
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sprstdlyscottsmn

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Unread post11 Nov 2020, 21:58

eloise wrote:The aerodynamic heating that Meteor sustain is > 500°C, I think that cap the sustain speed at Mach 3.5

Thank you, that data is quite clear. I am at a loss as to why cruise speed of M4+ was given for the flight test as the stagnation temp does not change much for 10km-30km altitude. I will re adjust my inputs to the Meteor model.
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garrya

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Unread post12 Nov 2020, 09:42

sprstdlyscottsmn wrote:I know that was mentioned at length in the prototype documents, but in the first link I gave on my post at the end of the previous page it specified a 4+M cruise speed for the operational missile.

I found something else
The multi shock inlet of A3M is designed for optimum performance between Mach 2 and 3.5
Inlet test.PNG

They tested flight condition at Mach 1.9 for Meteor
Meteor M2 test.PNG

To sum up, we know the following for Meteor
- The max turn down ratio is 12:1
- The max cruising speed is Mach 3.5
- The minimum cruising speed is Mach 1.9
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