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What's JP-8  
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Posted (6 years 6 months 3 weeks 6 days 11 hours ago) and read 3488 times:

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

AV Kent

28 replies: All unread, showing first 25:
 
User currently offlineSovietjet From Bulgaria, joined Mar 2003, 2577 posts, RR: 17
Reply 1, posted (6 years 6 months 3 weeks 6 days 11 hours ago) and read 3482 times:
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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


User currently offlineMark5388916 From United States of America, joined Aug 2007, 377 posts, RR: 0
Reply 2, posted (6 years 6 months 3 weeks 6 days 8 hours ago) and read 3454 times:

High Flashpoint, low freezing.


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User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 3, posted (6 years 6 months 3 weeks 5 days 22 hours ago) and read 3385 times:

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

Andrea Kent


User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 4, posted (6 years 6 months 3 weeks 5 days 20 hours ago) and read 3378 times:

This may shed some light on your questions...


http://tinyurl.com/2o59bg


User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 5, posted (6 years 6 months 3 weeks 5 days ago) and read 3257 times:

JP-8 is nothing more than Jet-A1 with a few additional additives.


Exceptions confirm the rule.
User currently offlineL-188 From United States of America, joined Jul 1999, 29791 posts, RR: 58
Reply 6, posted (6 years 6 months 3 weeks 4 days 18 hours ago) and read 3197 times:

It is just military grade kerosene.

Intended to replace both JP-4 and Diesel.



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User currently offlineKC135TopBoom From United States of America, joined Jan 2005, 12128 posts, RR: 51
Reply 7, posted (6 years 6 months 3 weeks 3 days 20 hours ago) and read 3099 times:



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?


User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 8, posted (6 years 6 months 3 weeks 3 days 18 hours ago) and read 3083 times:



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.
User currently offlineKevinSmith From , joined Dec 1969, posts, RR:
Reply 9, posted (6 years 6 months 3 weeks 3 days 14 hours ago) and read 3047 times:



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.


User currently offlineMark5388916 From United States of America, joined Aug 2007, 377 posts, RR: 0
Reply 10, posted (6 years 6 months 2 weeks 5 days 15 hours ago) and read 2912 times:



Quoting KevinSmith (Reply 9):

Do the DDGs and other fuel burning ships burn JP-5 as well?



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User currently offlineVenus6971 From United States of America, joined Dec 2004, 1440 posts, RR: 0
Reply 11, posted (6 years 6 months 2 weeks 5 days 4 hours ago) and read 2861 times:



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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User currently offlinePADSpot From Germany, joined Jan 2005, 1676 posts, RR: 5
Reply 12, posted (6 years 6 months 2 weeks 4 days 23 hours ago) and read 2828 times:

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]

User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 13, posted (6 years 6 months 2 weeks 4 days 23 hours ago) and read 2826 times:



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.
User currently offlinePADSpot From Germany, joined Jan 2005, 1676 posts, RR: 5
Reply 14, posted (6 years 6 months 2 weeks 4 days 23 hours ago) and read 2823 times:

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]

User currently offlineZANL188 From United States of America, joined Oct 2006, 3503 posts, RR: 0
Reply 15, posted (6 years 6 months 2 weeks 4 days 23 hours ago) and read 2815 times:
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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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User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 16, posted (6 years 6 months 2 weeks 4 days 23 hours ago) and read 2809 times:



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.
User currently offlinePADSpot From Germany, joined Jan 2005, 1676 posts, RR: 5
Reply 17, posted (6 years 6 months 2 weeks 4 days 19 hours ago) and read 2778 times:



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.



User currently offlineZANL188 From United States of America, joined Oct 2006, 3503 posts, RR: 0
Reply 18, posted (6 years 6 months 2 weeks 4 days 19 hours ago) and read 2777 times:
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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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User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 19, posted (6 years 6 months 2 weeks 4 days 18 hours ago) and read 2769 times:



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.
User currently offlineZANL188 From United States of America, joined Oct 2006, 3503 posts, RR: 0
Reply 20, posted (6 years 6 months 2 weeks 4 days 17 hours ago) and read 2767 times:
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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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User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 21, posted (6 years 6 months 2 weeks 4 days 17 hours ago) and read 2762 times:



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.
User currently offlinePADSpot From Germany, joined Jan 2005, 1676 posts, RR: 5
Reply 22, posted (6 years 6 months 2 weeks 4 days 16 hours ago) and read 2743 times:

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]

User currently offlineMark5388916 From United States of America, joined Aug 2007, 377 posts, RR: 0
Reply 23, posted (6 years 6 months 2 weeks 4 days 14 hours ago) and read 2716 times:

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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User currently offlinePADSpot From Germany, joined Jan 2005, 1676 posts, RR: 5
Reply 24, posted (6 years 6 months 2 weeks 4 days 6 hours ago) and read 2678 times:



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


25 Mark5388916 : A picture truly IS worth a thousand words, thanks! Mark
26 PADSpot : 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 pi
27 Post contains links Dougloid : 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
28 Woodreau : 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 u
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