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[Resolved] Modern US Bomber Aircraft – Range and Weapons

 
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[Resolved] Modern US Bomber Aircraft – Range and Weapons - 8/29/2016 7:47:55 PM   
Nightwatch

 

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Hey guys

So like the title says, I was playing around with US bomber aircraft and I noticed something strange going on with the ranges of the aircraft.
(I’m not sure if this is a bug, perfectly fine or the game engine handling things in a unique way, but I think this is worth a look.)

To be specific:
A generic modern B-1B (#4325 2018) with no weapon load has a range of about 9475 nm
A generic modern B-52H (#4118 2020) with no weapon load has a range of about 8476 nm
A generic modern B-2A (#4326 2020) with no weapon load has a range of about 6805 nm
Those numbers look pretty good. But i’m not so sure about the numbers when you start adding weapons.

If you add 24 JASSMs to the B-1B, its range drops to just 3430 nm, a reduction of almost 66%.
I think this looks kinda funny. The empty weight of a B-1B is 87.000kg and it has a maximum internal fuel capacity of 120.000kg, so the total weight of the aircraft without weapons is 207.000kg. 24 JASSM weight about 25.00kg, or just about 12% of the total empty weight of the aircraft.
How can a 12% increase in weight result in a range reduction of almost 66%?

And btw: Maximum taking of weight of the B-1B is about 216.000kg. This means the aircraft cant carry 24 JASSMs and a full fuel load. Its possible in CMANO however. (minor issue)

Lets compare this to the B-52Hs.
I cant add 24 JASSMs obviously, but I can do 12. Those 12 reduce the range of the aircraft to 7391 nm, a reduction of only 13%. This looks much more reasonable.
B-52H has an empty weight of 83250kg and carries 145.000kg internal fuel. This gives a total weight without weapons of 228250 kg. 12.500kg weapons is just about 5% of the total empty weight of the aircraft.
So a 5% increase in weight result in a range reduction of 13%. I can buy this.

What about the B-2?
Looks funny as well.
16 JASSMs result in a range reduction to 2931nm, that’s a reduction of 57%.
Total weight without weapons is 147.900kg ~ 17.000kg of weapons is 11%.
So an 11% increase in weight results in a range reduction of 57%. I’m not buying this.

If you check the test scenario I linked below, just look at the burn rates.
A Lancer with not weapons at 350 kts and 360k ft burns 74.1kg/min. With weapons without changing altitude or speed it jumps to 204.6 kg/min, a 276% increase. For a weight increase of just 12%. Insanity.

Maybe I’m missing something but I cant think of anything to explain this.
(Yes it’s the current database. I checked. )





Attachment (1)

< Message edited by Rory Noonan -- 4/8/2021 7:12:49 PM >
Post #: 1
RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 8/30/2016 3:23:15 PM   
ComDev

 

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Thanks for you feedback Nightwatch

A few points to consider...

- You're comparing loiter speeds, not cruise speeds. Loiter is for maximum endurance, cruise is for maximum range. If you plot a course for the aircraft and let them accelerate to cruise speed, the ranges change quite a bit.

- The reason for the relative diff between unloaded and loaded ranges for B-1/2 vs B-52 is that the cruise speed of the B-52 isn't much higher than loiter speed, but much higher for the B-1/2.

- The actual strike radius is given in the loadout description in the Database Viewer. Remember that the max radius is different depending on whether the aircraft is expected to drop (or jettison) ordnance, or expected to bring it back home to base. The DB Viewer assumes the ordnace is expended at the given radius, where as the range estimate you see in the Unit Status assumes the ordnace is carried all the way.

We have used combat radius from public sources for these bombers. If you think the DB Viewer ranges are incorrect, feel free to link to sources with updated info.

Thanks again!

< Message edited by emsoy -- 8/30/2016 3:26:23 PM >


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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 8/30/2016 5:43:02 PM   
Nightwatch

 

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quote:

You're comparing loiter speeds, not cruise speeds. Loiter is for maximum endurance, cruise is for maximum range. If you plot a course for the aircraft and let them accelerate to cruise speed, the ranges change quite a bit.


They change (obviously), but this is not relevant since the reduction remains the same when adding weapons:
The unloaded B-1B flies 10365 nm at 480kts, but loaded with 24 JASSMs its again reduced to 3740nm, exactly the same reduction of about 66%.
Same with the B-2 9300 vs 4000 ( 56% ) and the B-52, 10875 vs 9480 ( 13%)

I don’t have any problem with the total range when the aircrafts are unloaded.
They match with the info which is publicly available. What I don’t understand is how a 12% increase in weight can result in a 66% decrease in range in one aircraft while a 5% increase only results to 13% in another.

quote:


The reason for the relative diff between unloaded and loaded ranges for B-1/2 vs B-52 is that the cruise speed of the B-52 isn't much higher than loiter speed, but much higher for the B-1/2.
Also true but again, besides the point. Yes, a B-52 has a greater range than a B-1B, it carries more fuel to begin with and the original B-1B design was built for speed anyway.
But this doesn’t explain the reduction in range when you add weapons.

No matter how efficient the B-52 might be, there is no way loading her up to the maximum possible weight will result in only a 13% decrease in range while a B-1B losses 66% of its range under the same conditions.
Also, cruising speed of the B-52s is 450kts. B-1Bs fly at 480 kts. That’s a negligible difference.

But what happens if I just increase the speed of the B-52s to 480kts? The range drops (obviously, I don’t have any problem with this), for unloaded B-52 8500nm, and the loaded one 7400nm. So that’s a range reduction of only 8% (!), even less than the reduction at their optimal cruising speed.

We can play the same game with the Lancers. At 450kts its about 10200nm for the unloaded and about 3700nm for the loaded ones. Again, no difference, the range reduction when carrying weapons is still absurdly high compared to B-52s.

quote:


- The actual strike radius is given in the loadout description in the Database Viewer. Remember that the max radius is different depending on whether the aircraft is expected to drop (or jettison) ordnance, or expected to bring it back home to base. The DB Viewer assumes the ordnace is expended at the given radius, where as the range estimate you see in the Unit Status assumes the ordnace is carried all the way.

I’m aware of this, all that I’m interested at this point is exactly like you said – how far can a fully armed B-52 / B-1B until it crashes.
Ignore the those Strike Mission estimates from the database finder for a sec, just look at the fuel status panel of the individual unit (check attachment, unit fuel.png).

The game tells me 9462nm for a loaded B-52 carrying 145.000 kg of fuel and just 3750nm for a B-1B carrying 120.000kg of fuel.
I just can fathom why. IMO there is something wrong with whatever CMANO does to come up with those ranges. The range for the B-52 looks fine, but the absurdly large range reductions of the B-1Bs and B-2s don’t seem to work at all.


quote:


We have used combat radius from public sources for these bombers. If you think the DB Viewer ranges are incorrect, feel free to link to sources with updated info.

As said, I’m not arguing about the database viewer. There has to be something wrong with your math or whatever CMANO does coming up with its numbers.

I mean,
Range is just velocity x maximum flight time
maximum flight time is Fuel x LiftDragRatio / Specific Fuel Consumption x weight
We don’t know know every parameter but we know enough for me to illustrate the problem.
If you check the small and crude excel sheet I included you see that there is simply no way that a 25.000kg increase in weight will result in a range reduction of 66%.

Or to put it another way: An unloaded B-1B will make it to Bejing from Ellsworth AFB and back to CONUS with room to spare. If the same aircraft is carrying 25tons of weapons, it'll barely reach Hickam on Hawaii.




Attachment (1)

< Message edited by Nightwatch -- 8/30/2016 5:54:06 PM >

(in reply to ComDev)
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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 8/30/2016 8:57:22 PM   
ComDev

 

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Yeah I get what you're saying

Remember the database for Command is adjusting the ordnance drag/weight penalty settings to produce the correct range & flight profile. So if public sources say that the radius is 3500nm with a given loadout, the sim will produce the same result. And the payload weight/drag factor may be a bit on the high side if the combat range is shorter than what it should have been.

So the big question is... are the sources we've used not accurate enough? In your mind, what source should we have used?

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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 8/30/2016 9:36:21 PM   
Nightwatch

 

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Sorry but we still talk past each other. Please check my attachments.

I'm not talking about the radius, i'm talking about total range as shown in unitfuel.png.
Currently you can fly a loaded B-1B 3400nm straight until it runs out of fuel. And an empty Lancer will make 9476nm. Thats TOTAL range, NOT combat radius.
Hell, you cant even fly the '2400 nm Strike radius' mission someone put into the database viewer. The plane will crash on the return leg.
For the combat radius you put into the viewer to work the total range of the aircraft needs to be more than 5000nm. And as shown, if you do the math, the range is even greater than that.

Just compare the B-1B database stuff with the B-52 entry. There has to be a bug somwhere. Its physically impossible to get to a 225,8kg/minute fuel burn rate just by adding 25tons of weapons as shwon in unitfuel.png. No matter what any sources say, its flat out impossible to increase fuel consumption by 277% without increasing velocity.







< Message edited by Nightwatch -- 8/30/2016 9:37:20 PM >

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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 8/31/2016 7:14:27 AM   
ComDev

 

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quote:

ORIGINAL: Nightwatch

Sorry but we still talk past each other. Please check my attachments.

I'm not talking about the radius, i'm talking about total range as shown in unitfuel.png.
Currently you can fly a loaded B-1B 3400nm straight until it runs out of fuel. And an empty Lancer will make 9476nm. Thats TOTAL range, NOT combat radius.
Hell, you cant even fly the '2400 nm Strike radius' mission someone put into the database viewer. The plane will crash on the return leg.


Hmmm will it crash even if it drops the ordnance at max range?

It was me who came up with the propulsion model and put the data into the database

quote:

ORIGINAL: Nightwatch
For the combat radius you put into the viewer to work the total range of the aircraft needs to be more than 5000nm. And as shown, if you do the math, the range is even greater than that.

Just compare the B-1B database stuff with the B-52 entry. There has to be a bug somwhere. Its physically impossible to get to a 225,8kg/minute fuel burn rate just by adding 25tons of weapons as shwon in unitfuel.png. No matter what any sources say, its flat out impossible to increase fuel consumption by 277% without increasing velocity.


Yes, exactly hehe This is what the sources tell us the ranges actually are IRL, so the burn rates have to be adjusted accordingly to actually produce those ranges in-game. If you think something is whack, I'm open for suggestions, ideas, creative solutions.

What would be realistic ranges & profiles for the B-1/2, you think? What sources do you have?

When I adjust the loadout range and/or profile in the database editor the drag per kilo of payload is automatically adjusted, and the aircraft will be able to fly the new mission profile. No problem.

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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 8/31/2016 10:30:21 AM   
Nightwatch

 

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quote:

Hmmm will it crash even if it drops the ordnance at max range?

Hm, dunno, probably not but this is not how it should work.
Think about it, the aircraft carries almost 5 times more fuel than weapons. If the expenditure of 25 tons of weapons will result in an range increase of hundreds of miles, enabling the aircraft to return home, what should the consumption of 120 tons of fuel result in?

What sources did you use anyway?
If I had to guess I’d say those numbers you can find online are skewed by all those low altitude, high speed penetration profiles based on which the aircraft was first designed.
This differs greatly from a Hi-Hi-Hi maxrange maxrange with modest, internally payloads flown today.
Unfortunately there is no data publicly available on this.
But as I already tried to show, some simple math suggest a much higher range. I cant point you to a definitive number since we don’t know enough of the performance of the F101-Ge-102.
What I would do – I’d take the readily available combat radius of 2993nm, double it and use it as a baseline for a maximum weight Hi-Hi maximum range mission at cruising speeds.
Its wasg sure, but its way better than using Hi – Lo – Lo profiles from during the cold war.
Who knows what the were planning on doing with the engines in a penetrating profile at 200ft above ground. If you checkout those profiles, they are kinda fancy with maximum military power climbs in between and lots of loitering time for recovery. Doesn’t translate at all to a baseline for ‘fly as far as possible until you drop’.



< Message edited by Nightwatch -- 8/31/2016 10:31:13 AM >

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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 8/31/2016 3:41:00 PM   
Nightwatch

 

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Follow up
Check this out
http://www.gao.gov/assets/150/147336.pdf
This is a cold war area GAO document about how much the B-1B sucks (well, its GAO) but those projected numbers at page 21 (document page 19) are very interesting.
As you can see all those SIOP Hi-Lo-Hi and Hi-Lo-Lo missions have a projected ranges between 4000 and 6000nm while a conventional high altitude mission offers a range of 9850nm.
As noted in the document (below the table) the main reason for the shortest ranges is actual external weapons carriage.
This is not relevant in todays world, since the B-1B has lost the ability to carry stuff externally ages ago.

Anyway, this again should make it obvious that a Hi-Hi-Hi maximum range profile is not comparable to the Hi-Lo Cold War stuff.


As for the B-2, i honestly dont know. Much about propulsion of the B-2 is classified (not to mention alleged other pitch-black systems on board), any range estimate will probably fall far short if its actual range. Especially since they got rid off the Lo-Lo requirement.



< Message edited by Nightwatch -- 8/31/2016 3:49:37 PM >

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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 9/2/2016 3:57:57 PM   
ComDev

 

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Thanks, I'll take a look at the B-1B ranges

If you were to make some guesses on the different B-2A ranges, what would they be like?

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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 9/2/2016 6:22:52 PM   
Nightwatch

 

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Depends on how far you want to drift into alleged black drag reducing tech. There has been lots of talk about the aircraft charging the leading edges to mess with the airflow. Who knows if there is some truth to it did, but the sighting of an unknownaircraft with glowing edges over Wichita in 2014 lends more credibility to it IMO.

But even ignoring this topic, its just hard to make a reasonable guess on this.
Allegedly the B-2 has the ability to lock its control surfaces to further increase it stealth. I personally think this is true, but who knows what this feature does to range when you need turn the aircraft by varying the engine output.
Also, what about IR reducing measures. I don’t think the engine mode resulting in the lowest IR signature is identical to the most range efficient mode.

Anyway, if you want me to come up with a number:
quote:

Another thing B-2 crews do on the way to war is gulp fuel, taking up to 50 tons at a time in midair refueling sessions that last a half-hour or more. Flying to Iraq and back takes 38 hours, requiring at least four fill-ups by KC-135 or KC-10 tankers. When the airplane is at its ideal cruising altitude, refuelings take place about every six hours.
http://www.freerepublic.com/focus/f-news/3057735/posts

If this is correct and they refilled the plane every six hours with 100000lb of fuel while (obviously) hauling some kind of weapon load to Iraq – that’s 16.666lb of fuel an hour.
The B-2 carries 167000lb of fuel, so that’s flying 10 hours straight at cruising speeds.
At 480kts that’s 4866 nautical miles. Game has it at 4000nm for 16 JASSMs (about 36% of its total possible weapons load).
I’d take 4500nm range until crash for maximum takeoff weight. You would probably still understate its actual range (if we are not talking about full stealth mode configurations which are not simulated anyway) but its way better than what we have now. IMO at least.



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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 4/1/2021 6:36:21 AM   
Dimitris

 

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This has been revised in DB3000 v489.

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RE: [839.7] Modern US Bomber Aircraft – Range and Weapons - 4/2/2021 3:14:22 AM   
boogabooga

 

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A 66% range reduction between "no weapon load" and a weapon load might be explainable if the "no weapon load" is actually a ferry loadout which includes extra fuel tanks, either externally or in the bay. The reduction, then, is because you have to remove those to add the weapons. I have to check to see if this is the case.

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