posted 07-09-2001 05:29 PM            

[The following is new material, which can be found at http://www.af.mil/environment/contrails_exhaust.shtml ]
Often, military aircraft can be seen taking off with a black smoke appearing from the engines. This smoke is mainly soot particles, similar to diesel engines. Commercial aircraft also produce the same type of soot particles, but usually not to the same degree as military aircraft. This is for two reasons: the type of fuel and the type of engines.

Most military aircraft use JP-8 jet fuel which is a blend of commercial Jet Aviation Fuel -1 (or Jet A-1) with three extra additives. The additives are used to control ice formation, control biogrowth (molds and slimes), and inhibit corrosion. The military uses these additives because of the unique environments the military operates in, the type of self-sealing fuel tanks used, and the type of metals, plastics, and sealant used on military aircraft. Several specialized aircraft like the SR-71 and U-2 use different fuels than JP-8, but are developed from the same base stock. Fuels research is always ongoing. The newest fuel being brought into production is JP-8+100. Dubbed JP-8+100 because the additive package can increase the thermal stability of military fuel by 100 degrees Fahrenheit, the improved fuel helps prevent gums and deposits that can foul fuel lines.

Military engines are also designed with different performance characteristics than commercial aircraft. Military aircraft and engines also tend to be older and less efficient than commercial aircraft and produce more emissions. Engines are optimized for fuel consumption and power rates at a particular cruising altitude. At take-off, the engines are usually very inefficient and produce more emissions than when at the optimal cruising altitude. Older military aircraft like the B-52 and C-130 can leave a black smoke exhaust even at cruising altitude, while aircraft like the KC-135R with new engines produce an invisible exhaust plume. Typical pictures of aircraft exhaust emission are shown below.

posted 07-22-2001 11:54 AM            

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Posted 07-21-2001 01:44 PM
LTC8K6, yes, I realize that there is sometimes quite a bit of fuss over normal traffic when it leaves longer trails.
It seems as if you are willing to acknowledge that there is some differentiating factor that causes military flights to produce trails longer than commercial/passenger do. That is certainly what I've seen, over and over and over again.

But what I'm trying to convey is that these strips from the unidentified (military) planes behave differently than strips from identified planes. For example, I have never seen a strip from an indentified plane remain for hours, instead there is a tendency to sublimate and disappear quickly. On the other hand strips from unidentified planes will appear on days when the regular traffic isn't leaving them at all. Also, these same strips have a tendency to persist and spread. Even though they start with very blunt edges, after a couple of hours, they have spread and feathered out. (The photo below from Rense is a good example.) If you start with an initial hypothesis that this is caused by air pockets and subsequent feathering is result of the mixing of the surrounding air, it seems as though this mixing would have already blended the supposed pockets thus eliminating the possibility of having very blunt initial edges in the first place.

Even the longest real contails I ever saw and verified using Flight Explorer never had these attributes which seem to be the exclusive domain of the trail strips from unidentified flights, on the other hand besides the trail strips the unidentified traffic also produced contrails that were very consistent with the contrails from identified traffic. So it really looks like there is a common factor between the identified and the unidentified flights they both have consistent contrails in a given time period, but the unidentified flights may have the additional highly persistent trail segment that exhibits several factors that differentiate it from the contrails:

1. Tendency to persist
2. Never horizon to horizon (as contrails are sometimes), but relatively short.
3. Bluntness of start and stop

Interestingly these factors are consistent with what I would expect to be the behavior of a released liquid material. If there was a controlled sprayed material being released it would most likely have blunt edges and would contain so much more additional moisture than a contrail by itself that it would definately have a much longer duration than a contrail.

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posted 07-22-2001 11:58 AM            

According to Thermit, after persisting for hours, these trails typically feather out in the following manner (the photo itself comes from Rense's site):

posted 08-14-2001 12:54 PM            

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Jet fuel study prompts call for protective gear upgrade
by Chief Master Sgt. Gary Emery
Air Force Print News
08/13/01 - SAN ANTONIO -- Preliminary results of a health study of exposure to JP-8 jet fuel have led the Air Force Surgeon General to recommend the use of more effective protective equipment for workers who come in contact with the fuel.

People were coming forward with health complaints after being exposed to JP-8, so the Surgeon General started to investigate worker's concerns, said Lt. Col. (Dr.) Thomas Neal, chief consultant for occupational medicine at the Air Force Surgeon General's office.

Reported symptoms included dizziness, lightheadedness, skin irritation and objectionable taste and odor, records show. The Department of Defense completed a 20-year phased changeover from gasoline-based JP-4 to the safer and more versatile kerosene-based JP-8 in 1996.

Information for the study, which compares health data from 169 fuel cell maintenance volunteers with 160 Air Force people who have no contact with JP-8, was gathered over an 18-month period at six stateside bases, Neal said.

Scientists and researchers from several major universities are participating in the $3.6 million study, which is being funded by the Air Force and other government agencies, he said.

Study results so far indicate no long-term health hazards from JP-8 exposure, Neal said. For instance, medical records show no significant difference in reported ailments between the fuels workers and the control group.

But, Neal said, the study was specifically looking for acute, short-term health effects in a very narrowly defined group of workers -- fuel cell maintainers.

Nevertheless, because short-term JP-8 exposure has unpleasant and uncomfortable side effects, the Air Force is ready to move ahead to the next step --investigating more effective protective clothing and reviewing procedures to ensure maximum personal protection for fuels workers, Neal said.

"For many years, people exposed to solvents -- such as painters working in enclosed places -- have experienced similar symptoms to those we're seeing in people who enter JP-8 fuel tanks to perform maintenance," Neal said. "But that doesn't mean we're not concerned, we need to be proactive in protecting our people.

"That's not to say we haven't done so already. We have protective equipment and technical orders in place, but we're taking the initiative to explore recent advances in equipment that may provide greater protection," he said.

"Our interest is our people," Neal said. "We want to do everything possible to keep them healthy and safe."

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posted 08-14-2001 05:16 PM               

JP-8 fuel additive patent 1

JP-8 fuel additive patent 2

JP-8 fuel additive patent 3

JP-8 fuel additive patent 4

I am exausted at just reading the first 2 patents and following links to some of the patents sighted in the applications.

posted 08-15-2001 12:48 AM               

I don't want these folks harrassed in any way so I am not going to publish this information here. Any requests for information from them should be as scientific and direct to the point as possible IMHO.

Back to the subject at hand.

I am studing the components that go into the fuel additives and there is a lot of them. It is going to take some time to sort out but the experts already have this information I am certain but are not, or at least have not given it to me yet.

The thermal break down components are more important then what is in the fuel before it is burned for my purpose so we shall see.

Sorry I can not ad more to the thread tonight but after reading all these patents today and several more for another unrelated research project I am doing for my company my brain is pretty overworked.

More tomorrow after I have rested some.

posted 09-06-2001 07:56 AM            

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Kerosene based jet fuels have very low sulfur content compared to other fuels. Always less than 1% by weight and usually in the range of 0.04-0.06%. They are made from the upper 10% fraction of low sulfur crude to start with and then more is removed during the hydrogenation process. As far as H2O produced the average jet engine efficiency gives you 1.15 kg H2O/kg fuel. So, at crusing altitude a 747 produces about 28 kg H2O/km or 44.8 kg/mile. That's quite a bit of water, especially considering it's rapidly expanding, too. That's why the megasprayer picture shows the hazy clear space behind the wing (hot, hot compressed vapor) and then the spreading and freezing makes the contrail. And you guys are right. A fuel dump or a liquid spray should be visible the second it's released. The Blue Angels/Thunderbirds (and other jet flying demo teams) have little injectors right on the edge of the afterburner portion of their engines. They spray tiny amounts of light oil or fuel in the post combustion stream and make tons of smoke that way. But, the actual amount used in a 30 min show is very small, just a few liters.

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posted 09-06-2001 07:59 AM            

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I hope I'm not laboring the point...but some more on sulfur content in fuel inrelation to contrail production....

http://cloud1.arc.nasa.gov/success/daily_summary/Highlights/960427.hil.html

http://cloud1.arc.nasa.gov/success/success.eom.html#tocIIGiii

T-39 Highlights from SUCCESS; Bruce Anderson - LaRC

Observations of aerosol/trace gas emissions and wake/plume dynamics were obtained from the T-39 on 14 separate flights during the SUCCESS mission. On 10 of the flights, data were recorded within the wake of the NASA DC-8 or B757 aircraft at separation distances ranging from < 50 m to > 10 km and at altitudes ranging from the surface to near 13 km. Two of the flights were devoted to sampling the B757 exhaust as it alternately burned fuel of high (~700 ppm) and low (< 20 ppm) sulfur content. Important new information gathered in these flights include:- Modern aircraft engines appear to generate 1-5 x 1015 >20 nm diameter soot particles per Kg fuel burned at cruise altitudes. This emission index (EI) may be slightly pressure/temperature dependent as most altitude profiles suggest values increase a factor of 2 between the surface and 12 km. -Aircraft, when burning nominal sulfur level Jet A fuel, generate an aerosol fraction volatile at < 290ĄC which is 10-20 times more abundant than the soot component. These aerosols typically are < 20 nm in size and exhibit an EI which increases somewhat with decreasing atmospheric pressure/ temperature. They are present within 50 m (plume age of 0.25 seconds) behind the source aircraft engine and appear to grow in size with age and in high humidity/contrail producing situations. Their numbers are significantly reduced in heavy contrail cases and by decreasing the level of fuel sulfur, suggesting they are both soluble and most probably composed of sulfuric acid or sulfate.

ATMOSPHERIC CHEMISTRY

Chemical Ionization Mass Spectrometer; John Ballenthin - Air Force Phillips Lab

On May 3rd and 4th the T-39 participated in an aircraft chase of the B-757 under conditions where the B-757 was burning low sulfur fuel in one engine and high sulfur fuel in the other. The concentrations of the target exhaust products, NO2, HNO2, HNO3, SO2 and H2SO4 were measured within the individual plumes and near field wakes at separation distances ranging from 0.1 km to 10 km. The signature of the exhaust gases in the mass spectrum were clearly discernible with either fuel relative to the ambient concentrations of the measured species. Sampling of the low sulfur exhaust trail indicated a substantial reduction (~x5) in the observable gas phase SO2 and H2SO4 relative to that found in the high sulfur exhaust trail under identical sampling conditions. The concentrations of the NOy species were found to be essentially invariant with respect to fuel sulfur content.

And this is interesting...

Cloudscope; John Hallett - Desert Research Institute

Cloudscope shows the presence of a few particles in contrails which evaporate to leave a soot-like residue.
Shows the presence of particles at low temperatures <-65C which evaporate more slowly as the size becomes smaller suggesting the presence of a component other than ice with a lower vapor pressure.
There is some evidence of particle conversion to a liquid phase as they evaporate suggesting the presence of a soluble component which is reluctant to evaporate.

T/S

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posted 09-06-2001 08:21 AM            

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So is it possible that the occasional batch of jet fuel has a high sulfur content? Or that an increased amount of high-altitude flying has significantly increased sulfuric acid in the atmosphere? This might explain the oily rings around the sun and moon, and the chemdome phenomenon.

I found this article interesting. It's a PDF, unfortunately. http://eos913c.gsfc.nasa.gov/gcss_wg2/projects/ARM94/cold_cirrus.pdf

Corona-Producing Ice Clouds: A Case Study of a Cold Midlatitude
Cirrus Layer

The homogeneous freezing of sulfuric acid droplets of stratospheric origin is assumed to be the dominant ice particle nucleation mode acting in corona-producing cirrus clouds. It is speculated that this process results in a previously unrecognized mode of acid-contaminated ice particle growth, and that such small-particle "cold" cirrus clouds are potentially a radiatively distinct type of cloud.

It was only recently established, unambiguously, that cirrus clouds composed of nonspherical ice crystals could generate multiple-ring colored corona displays....It was inferred that these atypical midlatitude cirrus cloud microphysical conditions were the result of the formation of some characteristic type of ice crystal
homogeneously nucleated from stratospheric sulfuric acid droplets

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posted 01-02-2002 12:45 PM               

The picture of B-52's taking off. I would like to just add a bit of information that wasn't included. On take off the 52's and 135'2 used water injection to add thrust. The 135's with the new 'R model engines do not have it anymore. And the 'H model B-52 doesn't either.
But the water injection added alot to the black soot trails and made them impressively louder.

Just my 2 cents!
Chip

posted 01-05-2002 06:21 PM            

[Edited 2 times, lastly by mark sky on 01-05-2002]

posted 01-05-2002 08:27 PM            

Mr. Fishburn provided an update on JP8+100 implementation plan. Stated the implementation was proceeding as scheduled. Briefly explained the composition of JP8+100 and why we use it (new aircraft coming on line and significant reduction in maintenance cost). Gave an overview of the results of the data obtained thus far during the conversion. Colonel Johnson closed the briefing by stating it remains undetermined if the AF will convert the entire fleet (currently, only fighters and trainers) to JP8+100. Thus the capability to handle two types of JP-8 must be maintained by the bases. This is not the optimum way for the fuel community to conduct business but stressed it is the optimum way for the Air Force to conduct business.

posted 01-05-2002 08:36 PM            

Welcome to the Bulk Fuels Homepage (Chevron ~ rockey feller~ www.dfsc.dla.mil/main/b/b.htm
was redirected to http://www.desc.dla.mil/default.asp
seems these "old" (1998) links are a changen


[Edited 5 times, lastly by 3T3L1 on 01-05-2002]

posted 01-06-2002 02:33 PM            

By the way 3T3L1 I really like both of your Avitars,
i almost chose the spiral one myself~