Blackbird
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What's JP-8

Sat Jan 05, 2008 3:03 am

Assuming it's not classified, what's JP-8 and how does it differ from JP-4 or JP-5?

AV Kent
 
sovietjet
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RE: What's JP-8

Sat Jan 05, 2008 3:11 am

http://en.wikipedia.org/wiki/JP-8
http://en.wikipedia.org/wiki/JP-4
http://en.wikipedia.org/wiki/JP-5

Pretty good info there, I would say quite accurate, despite what people say about wikipedia
 
mark5388916
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RE: What's JP-8

Sat Jan 05, 2008 6:02 am

High Flashpoint, low freezing.
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Blackbird
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RE: What's JP-8

Sat Jan 05, 2008 4:44 pm

Is it as high a flashpoint as JP-7? If so, how do they light the thing off?

Andrea Kent
 
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RE: What's JP-8

Sat Jan 05, 2008 6:10 pm

This may shed some light on your questions...


http://tinyurl.com/2o59bg
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A342
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RE: What's JP-8

Sun Jan 06, 2008 2:16 pm

JP-8 is nothing more than Jet-A1 with a few additional additives.
Exceptions confirm the rule.
 
L-188
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RE: What's JP-8

Sun Jan 06, 2008 8:47 pm

It is just military grade kerosene.

Intended to replace both JP-4 and Diesel.
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kc135topboom
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RE: What's JP-8

Mon Jan 07, 2008 6:18 pm



Quoting L-188 (Reply 6):
It is just military grade kerosene.

Intended to replace both JP-4 and Diesel.

Didn't JP-8 replace JP-5, too?
 
A342
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RE: What's JP-8

Mon Jan 07, 2008 8:33 pm



Quoting KC135TopBoom (Reply 7):
Didn't JP-8 replace JP-5, too?

No. JP-5 has a higher flash point and is used on aircraft carriers (only?) to provide increased safety.
Exceptions confirm the rule.
 
KevinSmith
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RE: What's JP-8

Tue Jan 08, 2008 12:20 am



Quoting A342 (Reply 8):

No. JP-5 has a higher flash point and is used on aircraft carriers (only?) to provide increased safety.

Correct.


Navy birds will burn either JP-8 or JP-5 but if you're going to the boat it's JP5.
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mark5388916
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RE: What's JP-8

Sat Jan 12, 2008 11:57 pm



Quoting KevinSmith (Reply 9):

Do the DDGs and other fuel burning ships burn JP-5 as well?
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Venus6971
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RE: What's JP-8

Sun Jan 13, 2008 10:46 am



Quoting Blackbird (Reply 3):
Is it as high a flashpoint as JP-7? If so, how do they light the thing off?

Andrea Kent

JP-7 was used for the SR-71 to power its J-58's and was carried or tanked by KC-135Q's, the J-57 on the tank could burn it if they kept continois ignition on. You could tell if a J-57 burned JP-7 when you inspected the tailcones which were a ashy white color.

The engine's high operating speeds and temperatures required a new jet fuel, JP-7. Its relative unwillingness to be ignited required triethylborane (TEB) to be injected into the engine in order to light it up, and to light up the afterburner in flight; above -5 °C TEB spontaneously ignites in contact with air. Each engine carried a nitrogen-pressurized sealed tank with 600 cm³ of TEB, an amount sufficient for at least 16 starts, restarts, or afterburner lights; this number was one of the limiting factors of SR-71 flight endurance, as after each air refueling the afterburners had to be lit up. [2] When the pilot moved the throttle from cut-off to idle position, fuel flowed into the engine, and shortly afterwards a shot of 50 cm³ of TEB was injected into the combustion chamber, where it spontaneously ignited and lit up the fuel with a telltale green flash. In some conditions, however, the TEB flow was obstructed by coking deposits on the injector nozzle, hindering restart attempts. The refilling of the TEB tank was a perilous task; the maintenance crew had to wear silver fire suits.[3] Conversely, the JP-7 fueling was so safe in operational use that some aircraft maintenance was permitted during filling. The chemical ignition was chosen instead of a conventional igniter due to reliability reasons and to lower the number of mechanical parts that could fail in the extreme temperatures they would be subjected to. The TEB tank is cooled with fuel flowing around it, and contains a rupture disk that in case of an overpressure allows discharging of TEB and nitrogen into the afterburner section.
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PADSpot
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RE: What's JP-8

Sun Jan 13, 2008 3:34 pm

Quoting Mark5388916 (Reply 10):
Do the DDGs and other fuel burning ships burn JP-5 as well?

Naval marine engines and gas turbines can burn a multitude of different fuels. They will theoretically run on most types of jet fuel but normally are being fed with Medium Fuel Oil (MFO, also Marine Gas Oil or NATO-Code F-75) which is a type of bunker oil. It runs fine on marine diesel engines and also works with turbines if preheated (and at llower power-settings compared to aviation gas turbines). It is a much cruder distillate of raw oil and therefore much cheaper. But it is totally inappropriate as an aviation fuel.

Older tenders, oilers and carriers, which have steam boiler-based engines or large, two-stroke diesel engines also run on Heavy Fuel Oil. That is slaggy, very thick, residual substance of oil refinement. At room temperature it has a consistency like warm asphalt. It needs to be preheated even to just pump it. Today it is still used on freighters, tankers etc. It is really cheap but also extremely dirty stuff eco-wise and operation-wise (produces slag that needs to be filtered and collected on-board and later disposed off as hazardous waste at port).

[Edited 2008-01-13 07:38:43]
 
A342
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RE: What's JP-8

Sun Jan 13, 2008 3:37 pm



Quoting PADSpot (Reply 12):
Naval marine engines and gas turbines can burn a multitude of different fuels. They will theoretically run on most types of jet fuels but normally are being fed with Medium Fuel Oil (MFO, also Marine Gas Oil or NATO-Code F-75) which is a type of bunker oil. It runs fine on Diesel engines and also works ok with turbines if preheated. It is a much cruder distillate of raw oil and therefore much cheaper. But it is not appropriate as an aviation fuel.

What about gas turbine-powered aircraft carriers? Wouldn't it make sense to have just one kind of fuel?
Exceptions confirm the rule.
 
PADSpot
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RE: What's JP-8

Sun Jan 13, 2008 3:40 pm

Quoting A342 (Reply 13):
What about gas turbine-powered aircraft carriers? Wouldn't it make sense to have just one kind of fuel?

MFO costs a couple of hundred dollars less per tonne compared to aviation fuel (at government prices). An aircraft carrier would consume a couple of hundred tonnes each day, just for its own power and propulsion. Now you do the Math.  Smile

[Edited 2008-01-13 07:43:15]
 
zanl188
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RE: What's JP-8

Sun Jan 13, 2008 3:47 pm

Quoting PADSpot (Reply 14):
MFO costs a couple of hundred dollars less per tonne compared to aviation fuel (at government prices). An aircraft carrier would consume a couple of hundred tonnes each day, just for its own power and propulsion. Now you do the Math.

Answer = Nuclear powered aircraft carriers... Voila! Everything, including the GSE and aux generators, runs on JP-5.

[Edited 2008-01-13 07:49:28]
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A342
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RE: What's JP-8

Sun Jan 13, 2008 3:58 pm



Quoting PADSpot (Reply 14):
MFO costs a couple of hundred dollars less per tonne compared to aviation fuel (at government prices). An aircraft carrier would consume a couple of hundred tonnes each day, just for its own power and propulsion. Now you do the Math.  Smile

Maybe you could provide the prices for a tonne of jet fuel, MFO and HFO respectively?
Exceptions confirm the rule.
 
PADSpot
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RE: What's JP-8

Sun Jan 13, 2008 7:15 pm



Quoting A342 (Reply 16):
Maybe you could provide the prices for a tonne of jet fuel, MFO and HFO respectively?

Market prices for HFO vary greatly between 100$/tonne and about 350$/tonne, because price and availability depends almost to 100% on transport costs from the nearest refinery. MFO is currently at 460$/tonne (high grades up to 800$/tonne), Jet-A at 900$/tonne. Of course Governments buy fuel cheaper, but that is true for all kinds of fuels. But you need also need to take into account all the support costs for a oil-powered carrier. You need additional replenishment oilers, which need fuel also, need staff, need to be maintained, need to be bought etc. Also a nuclear carrier has lot of advantages: It does not need to be refueled for at least 12-15 years. A "dry" non-nuclear carrier is dead in the water without a refuel after a couple of weeks ... therefore ZANL188 is hits the nail on the head:

Quoting ZANL188 (Reply 15):

Answer = Nuclear powered aircraft carriers... Voila! Everything, including the GSE and aux generators, runs on JP-5.

 
zanl188
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RE: What's JP-8

Sun Jan 13, 2008 7:27 pm



Quoting PADSpot (Reply 17):
A "dry" non-nuclear carrier is dead in the water without a refuel after a couple of weeks ...

My understanding is that fossil fueled USN carriers conducting operations need to go alongside an oiler every 3 to 4 days....
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A342
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RE: What's JP-8

Sun Jan 13, 2008 8:55 pm



Quoting PADSpot (Reply 17):
Market prices for HFO vary greatly between 100$/tonne and about 350$/tonne, because price and availability depends almost to 100% on transport costs from the nearest refinery. MFO is currently at 460$/tonne (high grades up to 800$/tonne), Jet-A at 900$/tonne.

Thank you! That was very helpful.

Quoting PADSpot (Reply 17):
s. But you need also need to take into account all the support costs for a oil-powered carrier. You need additional replenishment oilers, which need fuel also, need staff, need to be maintained, need to be bought etc. Also a nuclear carrier has lot of advantages: It does not need to be refueled for at least 12-15 years. A "dry" non-nuclear carrier is dead in the water without a refuel after a couple of weeks ... therefore ZANL188 is hits the nail on the head:

From an operational perspective, a nuclear carrier is ideal, of course. But financially? I don't think so. Building, and above all, disposing of one is extremely expensive. That's why the UK has opted for a gas turbine-powered design.

(While we're at it, why is there no carrier powered by a large 2-stroke cruise diesel, propelled with cheap HFO, and additional gas turbines for peak performance? Is it because the military doesn't have the infrastructure to support HFO?)
Exceptions confirm the rule.
 
zanl188
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RE: What's JP-8

Sun Jan 13, 2008 9:03 pm



Quoting A342 (Reply 19):
From an operational perspective, a nuclear carrier is ideal, of course. But financially? I don't think so. Building, and above all, disposing of one is extremely expensive. That's why the UK has opted for a gas turbine-powered design.

Convienently ignoring the fact that the French went nuclear with the de Gaulle....
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A342
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RE: What's JP-8

Sun Jan 13, 2008 9:10 pm



Quoting ZANL188 (Reply 20):
Convienently ignoring the fact that the French went nuclear with the de Gaulle....

Who is ignoring that? Me or the Brits?
Exceptions confirm the rule.
 
PADSpot
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RE: What's JP-8

Sun Jan 13, 2008 10:45 pm

Quoting A342 (Reply 19):
That's why the UK has opted for a gas turbine-powered design.

... which is still in the multi-billions ... I would estimate the difference in costs between turbine/diesel-powered carrier and a nuclear one to a medium hundred-million dollar amount. Hence a nuclear-powered carrier would be 10-20% more expensive. That is still in a range where one can seriously think about taking the nuclear option.

Quoting ZANL188 (Reply 20):
Convienently ignoring the fact that the French went nuclear with the de Gaulle....

... which was an economic disaster. The CDG is a good argument for choosing a conventionally powered carrier.

Quoting ZANL188 (Reply 18):
My understanding is that fossil fueled USN carriers conducting operations need to go alongside an oiler every 3 to 4 days....

I think that is the peacetime procedure. Whenever something happens you need to be sure that the carrier is self-dependent as much as possible. I am sure carriers like the Kitty Hawk are self sustained for 2-3 weeks if necessary. Anything else would be a huge tactical disadvantage. Imagine how easy it is in a conflict for a hostile fleet (esp. subs) to blow up some oilers on the way to the carrier. If it needed to refuel every couple of days you could easily let it "starve" that way ...

[Edited 2008-01-13 14:59:31]
 
mark5388916
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RE: What's JP-8

Mon Jan 14, 2008 12:43 am

I've also read that on deployment, a CVN Can re-fuel its fleet from fuel bunkers. Does that mean it also carries MFO?

Mark
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PADSpot
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RE: What's JP-8

Mon Jan 14, 2008 8:34 am



Quoting Mark5388916 (Reply 23):
I've also read that on deployment, a CVN Can re-fuel its fleet from fuel bunkers. Does that mean it also carries MFO?

You may be interested in this picture link: http://www.navy.mil/view_single.asp?id=52523
 
mark5388916
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RE: What's JP-8

Tue Jan 15, 2008 3:59 am



Quoting PADSpot (Reply 24):

A picture truly IS worth a thousand words, thanks!

Mark
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PADSpot
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RE: What's JP-8

Wed Jan 16, 2008 1:35 pm



Quoting Mark5388916 (Reply 25):
A picture truly IS worth a thousand words, thanks!

I must admit that I don't really know whether a CVN bunkers MFO for transferal to other vessels. It might just be the case that the Cruiser on the picture takes JP-5 for its SeaHawks?!
 
Dougloid
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RE: What's JP-8

Wed Jan 16, 2008 2:14 pm

Andrea, here's an interesting link with some turbine fuel specification numbers from the BP people. Jet fuel is wide cut gasoline. so they say.

If you're really interested you can dig out the military specifications for nearly anything. It's all archived somewhere. My favorite is a 10 page document that describes an octal tube socket.

However it can be useful information-one of the most misused words in buying components and supplies is "milspec". I've seen guitar amplifiers allegedly "wired to milspec standards" and they just plain aren't.

http://www.bp.com/sectiongenericarti...categoryId=4503664&contentId=57733
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Woodreau
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RE: What's JP-8

Wed Jan 16, 2008 4:30 pm

Quoting Mark5388916 (Reply 10):
Do the DDGs and other fuel burning ships burn JP-5 as well?

In the US Navy - DDGs and other conventionally powered ships carry JP-5 (I think the NATO equivalent is F44) and DFM (NATO F76). The ship's engines use DFM but can burn JP5 if needed. The ships don't carry enough JP-5 to use in the ship's engines to cross an ocean. From a ship's engineer's standpoint - I think engineers would like to burn JP-5 (probably means less water washing of the gas turbine engines) , but the bean counters ashore would freak if they burned JP-5 instead of DFM.

Quoting ZANL188 (Reply 18):
My understanding is that fossil fueled USN carriers conducting operations need to go alongside an oiler every 3 to 4 days....



It's more to top of the carrier's JP-5 fuel rather than the carrier's DFM supplies to transit - jets burn a lot of JP-5 in a normal day's worth of flying. Conventional carriers need fueling more often because they don't carry as much JP-5 compared to the nuclear powered carriers. (But since you're already hooked up and fueling for JP-5, why not take on F76 for the ship at the same time while you're connected?) Fuel is tracked very closely by everyone when a ship transits across the ocean, and everyone starts fretting about when the next refueling will be when fuel gets to 80%. Conventionally fuelled ships (at normal transit speeds) can cross the Pacific without refuelling.

Quoting PADSpot (Reply 26):
I must admit that I don't really know whether a CVN bunkers MFO for transferal to other vessels. It might just be the case that the Cruiser on the picture takes JP-5 for its SeaHawks?!

We practice dry-hookups frequently, where we'll hook up and transfer a token amount (like a 5 second squirt of fuel - open the valve, close the valve, you're done) - just to stay in practice - during transits. It helps everyone, the rig crews, the seamanship involved in driving two ships 100ft apart, etc, signalmen get to practice semophore and flag hoist, male sailors get to check out the women on the other ship, etc... I mean it's not like we have a hot date anywhere soon, we're already in the middle of the ocean going from point A to point B. So why not use the time to get some training done? It's also a nice photo op. Lots of widgets checked off and training accomplished in the picture. A nuclear-powered carrier doesn't carry any fuel to refuel any of its escorts other than JP-5. (which it needs for its own aircraft.).

[Edited 2008-01-16 08:34:13]
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