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"We have... liftoff!"

rstark
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The Titan II missile used in the Gemini Space program weighed 330,000 lbs at liftoff. Riding skyward on 440,000 lbs of thrust it would accelerate to 60 mph in a distance about equal to its own length (105 feet, about the length of a Boeing 737). Astronauts reported that the acceleration on a launch would build to just over five Gs of acceleration before first stage burnout at around 100,000 feet and 60 miles down range. At this point, stage two would ignite and push the capsule into space before shutting down, its fuel tanks exhausted. As the capsule entered orbit, fully three-quarters of the weight of the airframe present at liftoff would have been burned up as fuel to lift the crew capsule into space. From ignition start to stage II shutdown, the whole powered portion of the flight would last about ten minutes. In a former life, I used to sit nuclear alert as a Missile Combat Crew Commander in Tucson. My Titan II had no crew capsule but rather a re-entry vehicle whose sole passenger was a thermonuclear warhead. Several of our Pilots here at Southwest served in this capacity prior to going to Air Force flight training. Fortunately, none of us "missile pilots" logged any flying time, except for test launches out of Vandenberg AFB, in California. As in many jobs, I see parallels in my current job as aircraft Pilot. Today, flying from Providence, R.I., to Phoenix, my aircraft is filled with 33,000 pounds of jet fuel, spread across three tanks (a main and the two wing tanks). At brake release, we will accelerate to about 150 mile per hour in less than 30 seconds and liftoff consuming about 5,000 pounds of fuel an hour, per engine. At cruise altitude, the fuel usage rate for each engine will decrease to about 2,000 lbs per hour. This increase in fuel efficiency is why jetliners fly so high. Like the missile burning fuel, we will consume 1,500 pounds of fuel as we climb just getting to 20,000 feet. By level-off at 36,000 feet, we will have used two tons of jet fuel at about $2 a gallon  ($1,200 total). Nearly two and a half hours downrange, our center main tank will be empty and we will run the rest of the way to our destination on our full wing tanks.  Over the planned 5:05 hours of flight time to Phoenix, we will consume 25,500 pounds, or over eleven tons of fuel ($7,700!). Even at that rate, I have read that the fuel used is still less than if we had loaded 40 or so SUV's with three or four people each and driven everyone of our 137 passengers the same distance. Efficiency and unsurpassed speed. Two great reasons flying SWA has become the logical choice for modern travelers.
19 Comments
Francisco_Delga1
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Thanks for the info. Some guy in a different post offered to pay Southwest Airlines fuel bill. Perhaps he should read this and maybe just maybe he might rethink his offer.
Jeff2
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It would take 34.25 SUV's-4 passengers each-driving app. 2600 miles. That would be 4452 gal. of fuel at 20 mpg. That's 32.5 gallons per passenger. The 737 w/ 137 (including crew?) would consume 3750 gal.of fuel (6.8 lbs per gallon). That's 27.37 gallons per passenger. Comparing the exact amount of fuel per mile would be interesting, but I would need to know the actual miles of the flight-not n. miles but road miles in the air.
chuchoteur
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Hi Jeff, Even with actual track miles (which are always greater than great circle distances) and factoring in some headwinds (the aircraft fly more miles in the air than an estimated still air distance - ESAD), you would in most cases find that "road miles" can be very penalising! Air Transport as an industry has much higher load factors than the average SUV driven across state, and when looking at fuel burn per pax, remember that CO2 emissions are a linear function of weight. For 1kg of fuel (Jet A1) burnt, you will have produced 3.15kgs of CO2, recognised as a major Greenhouse Gas (GHG). The differential in fuel burn per pax is thus multiplied, and maybe the State of California is onto something sueing car manufacturers for their pollution... :o)
Frank_Ch__Eigle
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> For 1kg of fuel (Jet A1) burnt, you will have produced 3.15kgs of CO2, recognised as a > major Greenhouse Gas (GHG). Those more chemically inclined may recall that at least as many molecules of H2O (water vapour) are created during hydrocarbon combustion as CO2 molecules. And according to wikipedia, H2O "accounts for the largest percentage of greenhouse effect".
chuchoteur
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Hi Frank, You raise an interesting point, as it is often mentioned that water vapour has a higher radiative forcing effect than CO2. However, it is not often discussed, as water vapour is generally taken as having a short life cycle in the atmosphere (measured, depending on the studies, from a dozen day to a few weeks). CO2 on the other hand has an atmospheric life cycle measured in decades... hence the more we put out, the higher the ppm (parts per million) quantity in the atmosphere. From the measurements derived (ice cores can give an idea of atmospheric composition back about a 100.000 years or so), the CO2 count in ppm is on the increase, whereas the overall H2O appears to have remained fairly stable. Hence, CO2 is the Greehouse Gas that attracts the most attention. CO2 released at high or low altitude has pretty much the same effect, primarily due to this long atmospheric life cycle (ie in the decades it is in the atmosphere, it will end up spreading more or less evenly). There is some debate regarding the effects of contrails (Condensed water vapour at high altitude), however there are no definitive answers yet... There is still a lot left to discover in the environment domain! :o)
Reid_Rosenberg
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Mr. Stark, your "calculation" that flying is more fuel efficient than driving is not correct. One reason is that when considering all domestics commercial flights in this country, few are cross-country flights. Shorter trips consume more fuel per mile because the high fuel consumption of take-off remains, yet with less high-altitude cruising time to make up for all that fuel consumed at take-off. With all the talk of global warming in recent months, many (not just environmentalists) have stepped forward to explain the concept of the "carbon footprint" that each of us leaves behind on earth. There seems to be a general consensus that traveling by jet increases one's carbon footprint substantially versus any other conventional means of travel. Although your post is interesting, if you had properly acknowledged the facts on this subject (instead of your own loose calculations) you would have likely come to a much different conclusion. As far as the penultimate sentence of your post goes: "Speed and efficiency," let me just say the former is the only one of the two attributes you list that is true. Sincerely, Reid Rosenberg Frequent SWA Traveler
Jennifer_Singh
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Thank you Ray Stark! Your posts are always so much fun to read. You have a way of making your reader feel included in the action -- keep it up!
Micah1
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Ray, It's interesting. The distance between Providence and Phoenix is 2,662 miles if you drive. If you fly, only 2,277 miles lie between those two cities.
Mary9
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I believe Capt. Starks was talking about a particular non stop flight that SWA operates between Providence and Phoenix. His point being flying is still a cost effective way to travel. The global warming issue is another discussion for another web site in my opinion.
rstark
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Reid, With all due respect, your logic is inconsistent. All takeoffs are not the same - they are not constants in fuel burn. A short hop to a lower cruising altitude in a light jet burns far less fuel than a takeoff at or near max gross weight. The climb I described was absolutely accurate for the leg I flew -nearly six hours. To lift tons of fuel into the air requires tons of fuel burnt. I stated that for my given flight, the driving would have been more inefficient and I believe someone did th public math demonstrating that fact in simple terms. Since no one has put test cases in a laboratory for absolute comparative testing, I can say with a reasonable level of certainty that your "facts" are little more than interested conjecture. If you would like to like to refer us to a scientific abstract, we might all learn more about the environmental impact of the CFM-56 family, an engine which I might add has the lowest emissions of any jet engine ever produced. One thing I do remember from the scientific journal: Mt. Pinatubo produced more greenhouse gasses in 48 hours than mankind has produced since the dawn of the industrial revolution. The effect of these gasses on the atmosphere are completely unknown. Don't want to get into a big discussion of the global warming issue here... Hope to see you on one of my flights! Ray
chuchoteur
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Hi Ray, We carry out a number of studies comparing the environmental impact of both aircraft and other means of transport. Reid is correct in part when he states that short haul flights can result in higher emissions than other forms of transport (that tends to be the case on flight sectors under 2-3 hrs for example). Interestingly, taking into account respective load factors, we have found that trains expend the same amount of energy per passenger to move someone from a to b. It is important to note however that 80% of flights cannot be easily replicated by another form of transport. also, aircraft don't require a ribbon of asphalt or tracks to link two destinations... and the noise they produce is limited to departure and arrival areas (cf IATA fast facts http://www.iata.org/pressroom/facts_figures/traffic_results/fast_facts.htm ). Southwest's 737's equipped with winglets also benefit from a significant fuel burn reduction through drag optimisation (around 3-3.5% less fuel burn). Better take-off performance also helps limit the noise "footprint" on the ground. The CFM-56 engine family will have an even lesser environmental impact through the tech insertion package currently being fielded. By replacing combustor elements (amongst others), the engine will produce less NOx, a big factor on local air quality. I believe this should be fully retrofittable as well. Don't hesitate to drop me an e-mail, and I can send you some materials on environmental comparisons :o)
Reid_Rosenberg
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Ray, Raphael corroborates my argument that short- and medium-haul flights result in higher emissions than other forms of transportation. While this may not hold true for a 6 hour cross-country flight, I say look no further than to the Southwest's average flight duration: one hour and 46 minutes. I rest my case.
Reid_Rosenberg
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Even better, I have just come across information from Southwest's "Facts Sheet" section of its web site that claims, as of 11/06, the airline's average flight duration is one hour and 37 minutes and covers a distance of 625 miles.
chuchoteur
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Hi Reid, Don't forget you have to take into account load factor... Quick 'n dirty example (bearing in mind I take some generic assumptions, and obviously I don't have exact performance data for SWA!): Looking at a 625nm flight from Dallas Love Field, with a 150nm divert (for reserve fuel), and an FAA domestic profile. Pax weight circa 95kgs, load factor 85% (conservative, Southwest probably has a higher LF), which equates to 109 pax out of 137 seats available. A B737-700 with CFM56-7B24 engines with winglets would burn approx 3735 kgs of fuel for this trip., which equates to roughly 1228.87 USG (or 11.274 USG per pax transported - apologies if I've made some small mistakes in my conversions, I'm european!). Looking at a Jeep Grand Cherokee, and taking the BEST performance figures on the Highway (ie, 22 miles per USG, and that's generous, most of the performance figures for their engines are sub 20 mi/usg), the same amount of fuel for one person would take you roughly 248nm. You would need AT LEAST 3 persons on board with the BEST engine for that SUV to get you over the 625nm range... And obviously, we are assuming that the BEST jeep is driving AN OPTIMISED track... in reality, the ground track distance will be longer, will require a significant amount of bedding and asphalt, and disrupt probably quite a few communities due to the noise generated... This is obviously just a quick calculation, but I think it certainly shows that: - the problem is not so simple - depending on the comparison you wish to make, the picture could be significantly different - ideally, don't buy an SUV - SWA, with high load factors, are extremely competitive compared to other forms of transportation ... And as Ray points out, with an SUV, you would not have got to your destination in one and a half hours!
rstark
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Thanks Raphael, There are a myriad of other issues like specific mile per pound (like miles per gallon) burn issues for planes sitting and waiting takeoff. Engines at low RPM are inefficient, thus the nasty diesel smell whan the wind blows the exhaust your way. A jet engine is most efficient right before it melts -in other words, at high power settings. While aspects of pollution may be exacerbated by high burns during climb, the pollution of the idling engine during a descent taking hundreds of miles (almost equidistant to the climb portion) may in fact be more deleterious than many believe. Regarding the zero-miles-to-the-gallon burned while awaiting takeoff in long lines, a new product may pose a solution. Boeing is working with a developer on a hydraulic powered nose wheel thay would pull the plane along allowing the pilots to start the engines only shortly before takeoff. That would save the passengers money and minimize wasted emissions as well. As I still say, flying sure beats driving! Ray
Jeff2
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Captian Stark: Regarding your posting a couple of months ago about turbulance (how is this spelled?); anyway-if I had your email address I would relay to you my experience on the roughest flight I've ever been on (USAIrways 737 in November) and I've been on some rough flights, but nothing like this-I also have a couple of questions I believe you could do a good job of answering-would love to hear from you. ps I'm the responder who did the milage calculations-jf
rstark
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Jeff, Either post it here or go to www.takingflight.us and ask me on the CaptainStark forum. Kind of tricky to find but click on the FORUM tab and you'll see my forum on there. Y'all come on over! We'll leave a light on! Ray
bert
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Regarding the discussion on fuel efficiency of airtravel: Driving alone, per mile, is always less efficient than average airtravel efficiency on cutting edge modern jets; see the calcution linked on my website. You'd have to get over 70 mpg to claim otherwise. Driving 2 people to a car, is about comparable to airtravel (efficient passenger cars compared to efficient passenger airplanes). You usually have to travel fewer miles going by air (path of the crow is shortest) depending on how long the trip and how nearby the airports are.
Scott5
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Hi Ray, I just finish watching coverage of the Space Shuttle launch tonight and made a note of when the launch occured and then went to Flightaware and checked to see if there were and Canyon Blue and Red Boeing 737s in the area. I noticed that there were two good candidates. One is Flight 1705 which took off from Orlando at 6:35 PM CDT (3 minutes before launch) and was 10,000 ft above the Econlockhatchee River Swamp area (28.32 degrees N and 81.08 degrees W) at 6:38 PM CDT (the time of liftoff). The other Flight in the area was flight 1326 which took off from Fort Lauderdale at 6:10 PM CDT for Long Island. This flight was 35,000 feet above and area near Winter Park (28.58 degrees N 81.37 degrees W). My short question is do you think either of these two flights had a view from the window seat of a Boeing 737-700 of the Space Shuttle launch?