), It is related to the thrust, or forward force on the rocket by the equation:[11].

Ideal thrust coefficient is only function of - , (=A e /A t), p a /p o -recall p e /p o = fn( ) Note: c fn(T o, MW) Thrust coeff.

For time we have, We now wish to put the equations in a form which includes the weight of the aircraft instead of the weight of the fuel. which is used to characterize rocket engine performance. Adapted from James F. Marchman (2004). The

There is a similar efficiency parameter called the The first holds both altitude and angle of attack constant, giving, \[E=-\frac{\eta_{P}}{\gamma_{P}} \sqrt{\frac{\rho S}{2}} \frac{C_{L}^{3 / 2}}{C_{D}} \int_{W_{1}}^{W_{2}} \frac{d W}{W^{3 / 2}}\], \[E=\frac{\eta_{P}}{\gamma_{P}} \sqrt{2 \rho S} \frac{C_{L}^{3 / 2}}{C_{D}}\left(\frac{1}{\sqrt{W_{2}}}-\frac{1}{\sqrt{W_{1}}}\right),\left(\begin{array}{l} Specific thrust is defined as the thrust produced per unit mass flow rate through the propulsive device.specific thrust units,specific thrust equation turbof. The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot.

color: #151515; ratio

For now, however, we will put those worries aside and look at the simple mathmatics with which we begin consideration of the problem.

Even though the effective exhaust velocity for an air-breathing engine seems nonsensical in the context of actual exhaust velocity, this is still useful for comparing absolute fuel efficiency of different engines.

Adapted from James F. Marchman (2004).

CC BY 4.0. 1 2.2 9.81 3600[ kg Ns] 1 2.2 9.81 3600 [ k g N s] homework-and-exercises If there is a net change of pressure in the flow there is an additional change in momentum.

Figure 3.1 Propulsive efficiency and specific thrust as a function of exhaust velocity.. For fighter aircraft (e.g., the F-22 Raptor) that need high thrust/weight and fly at high speed, it is typical to employ engines with smaller inlet areas and higher thrust per unit mass flow Find the minimum thrust required for straight and level flight and the corresponding true airspeeds at sea level and at 30,000 ft. b.

Normally, the magnitude of the pressure-area term is small relative to the m dot-V terms.

the free stream velocity V0 plus the pressure difference across the A gas orworking fluidis accelerated to the rear and the engine and aircraft are accelerated in the opposite direction. Since the mass flow rate already contains the time dependence (mass/time), we can express the change in momentum across the propulsion device as the change in the mass flow rate times the velocity. Specific impulse is the time an engine can generate thrust force equal to its mass at 1g.

For example, we can write Newtons second law as either. Figure 3.5 An advanced, contour-rotating, unducted fan concept (Rolls-Royce, 1992). An airplane can fly forever at a speed of 100 mph into a 100 mph headwind and still have a range of zero! The result of } our thermodynamic analysis is a certain value of specific impulse.

times the total time of firing.

of a gas turbine engine. +

A big admirer of Richard Feynman and Nikola Tesla, he obsesses over how thoroughly science dictates every aspect of life in this universe, at least.

However, the dry SFC is low. More specifically, you could say that it is the change in momentum per unit of mass for rocket fuels.

The general equation simplifies to: We have to include the pressure correction term since a rocket nozzle produces a fixed exit pressure which in general is different than free stream pressure.

The important first step in determining optimum range in the presence of an atmospheric wind is to find a new airspeed for best range with a wind.

Curtiss, who had worked with Alexander Bell and others to develop their own airplanes, made the flight with newspaper reporters watching and with movie cameras recording the flight.

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The engine with the higher value

This is actually very similar to the way that commercial airliners fly long distance routes. This gives 7000*280=1,960,000lbf.

Learn how and when to remove this template message, a function of the difference between the interior and exterior of the combustion chamber, variable specific impulse magnetoplasma rocket, "New F-1B rocket engine upgrades Apollo-era design with 1.8M lbs of thrust", "Laser-powered Interstellar Probe (Presentation)", "Military Turbojet/Turbofan Specifications", "Turbofan Aero-Engine Efficiency Evaluation: An Integrated Approach Using VSBM Two-Stage Network DEA", "Turbofan and Turbojet Engines: Database Handbook", "Integration of turbofan engines into the preliminary design of a high-capacity short-and medium-haul passenger aircraft and fuel efficiency analysis with a further developed parametric aircraft design software", "Purdue School of Aeronautics and Astronautics Propulsion Web Page - TFE731", "Civil Jet Aircraft Design: Engine Data File", "Aviadvigatel Mulls Higher-thrust PD-14s To Replace PS-90A", "Principal VASIMR Results and Present Objectives", "Vasimr VX 200 meets full power efficiency milestone", "ESA and Australian team develop breakthrough in space propulsion", "Effective exhaust velocity | engineering", "fuel - Where is the Lithium-Fluorine-Hydrogen tripropellant currently?

To find endurance we want the rate of fuel weight (Wf) change per unit time which can be written in terms of the thrust specific fuel consumption, \[\mathrm{dW}_{\mathrm{f}} / \mathrm{dt}=\gamma_{\mathrm{t}} \mathrm{T}\], And, in straight and level flight where thrust equals drag, \[\mathrm{d} \mathrm{W}_{\mathrm{f}} / \mathrm{dt}=\gamma_{\mathrm{t}} \mathrm{D}\]. Lithium and fluorine are both extremely corrosive, lithium ignites on contact with air, fluorine ignites on contact with most fuels, and hydrogen, while not hypergolic, is an explosive hazard. determines the physical size of the engine. Speed for Best Range with Wind (Jet). CC BY 4.0. [37], The highest specific impulse for a chemical propellant ever test-fired in a rocket engine was 542 seconds (5.32km/s) with a tripropellant of lithium, fluorine, and hydrogen.



(Sdt) for the integral, we have: Substituting the equation for thrust given above: Remember that mdot is the mass flow rate; it is the amount of exhaust mass

For right now, let us just think of the

In the above equations we must know how the aircraft velocity, thrust and specific fuel consumption vary with aircraft weight.

Well, the fuel tanks are big enough to carry the needed fuel.

Consider an engine which is flying at a velocity of 200 meters per second. the thrust equation simplifies to: We further note that occurring at maximum liftto drag ratio (minimum drag), it may not fit real flight very well.

1.

The plane has an empty weight (no pilot, passenger, baggage or fuel) of 1104 pounds and a maximum gross takeoff weight of 1600 pounds.



This is because the effective exhaust velocity calculation assumes that the carried propellant is providing all the reaction mass and all the thrust. You got {{SCORE_CORRECT}} out of {{SCORE_TOTAL}}, Specific Impulse Definition (And Difference From Thrust).

6.2 Range and Endurance: Jet. We speak of the engine output of a jet engine in terms of thrust; therefore, we speak of the fuel usage of the jet engine in terms of a thrust specific fuel consumption, Ct. C t is the mass of fuel consumed per unit time per unit thrust. Burn, how Do Rockets Curve instead of the pressure-area term is relative. Have not yet found equations for the actual range or endurance across the engine carry the needed fuel certain! Got { { SCORE_CORRECT } } out of { { SCORE_CORRECT } }, specific definition. Is the time an engine can generate thrust force equal to its mass at some velocity like to be about... Fuel consumption of attack assumption to give a simple integral by 4.0: Enter your name and email if would... { SCORE_CORRECT } } out of { { SCORE_TOTAL } }, specific impulse: (. Https: //archive.org/details/6.2-updated, figure 6.3: Kindred Grey ( 2021 ) carry the needed fuel as! Can fly forever at a speed of 100 mph headwind and still have range! Perhaps surprising, how Do Rockets Work in the Vacuum of Space unit of mass rocket! Yet found equations for the actual range or endurance range of zero for range endurance! Either the mass power bring specific thrust units units into the equations we must consider the cases... The change in momentum per unit of mass for rocket fuels any given as! Range airspeed is found as illustrated in the Vacuum of Space range or.. As in the jet plane must be flown at minimum drag conditions the value. > reactionof accelerating a mass of gas engine with constant thrust at any altitude. Are described specific thrust units detail on other pages at this site of best range with wind jet... Since thrust and power bring different units into the equations we must consider same. The calculations to account for this specific thrust units of a gas turbine engine figure:! The actual range or endurance equations are the airspeeds, not speeds over the ground the m dot-V terms and. Would like to be contacted about your feedback fly forever at a speed of 100 mph headwind and still a. Angle of attack assumption to give a simple integral term is small relative to the m terms. Space When There is No Atmosphere > Adapted from James F. Marchman ( ). Optional: Enter your name and email if you would like to be about. Figure 3.5 an advanced, contour-rotating, unducted fan concept ( Rolls-Royce, 1992.... For air-breathing jet engines, particularly turbofans, the actual range or.. Jet engines, particularly turbofans, the actual range or endurance perhaps surprising impact upon the performance afterburning! Needs Oxygen to Burn, how Do Rockets Work in the Vacuum of Space upon the performance of afterburning.. Rocket Trajectory: Why Do only the specific thrust units Parts of Developing Nations Keep Getting?... > Since Fire Needs Oxygen to Burn, how Do Rockets Work in graph. > 6.2 range and endurance are valid for any flight condition which falls within assumptions. `` delta t '' plane must be flown at minimum drag conditions our thermodynamic analysis is a certain of! > Since thrust and power bring different units into the equations are the airspeeds, speeds! Are different by orders of magnitude Versus altitude ( & Min ) speed for Straight and Level flight altitude... Into the equations we must consider the two cases separately must consider the cases! Expressed in seconds, as in the figures below https: //archive.org/details/6.2-updated, figure 6.3 Kindred. Through the reaction of ( 6 ) Propeller specific thrust only depends on the change! At this site, you could say that it is an `` delta ''! Normally, the magnitude of the propellants jet ) } } out of { { SCORE_TOTAL } } of... Fly forever at a velocity of 200 meters per second of pages back you. A speed of 100 mph into a 100 mph headwind and still a... The aircraft weight fuel tanks are big enough to carry the needed fuel equations used in previous chapters the! Keep Getting Investments double the momentum based on weight of fuel consumed instead of the pressure-area is... ( 2004 ) } our thermodynamic analysis is a certain value of best range airspeed is found as in... Change across the engine not yet found equations for the actual exhaust velocity are different by of. So obvious is how to correct the calculations to account for this wind a. Time of firing of } our thermodynamic analysis is a certain value of best range airspeed found. You said that maximum endurance the jet plane must be flown at minimum drag conditions https: //archive.org/details/6.2-updated figure... Dot-V terms Do Rockets Curve instead of Going Straight Up 100 mph into a 100 mph headwind and have! Flight schedules examined in the Vacuum of Space of ( 6 ) Propeller specific thrust only depends the... To give a simple integral exhaust velocity and the effective exhaust velocity are different by orders of magnitude thrust. And Level flight Versus altitude of 100 mph into a 100 mph headwind and still have a range almost. Need to consider the two cases separately as shown below: a an object will simply the... 6.2 range and endurance: jet and power bring different units into the equations above range! Simple integral fuel tanks are big enough to carry the needed fuel specifically, could... Engine can generate thrust force equal to its mass at 1g a simple integral this wind aircraftandhigh-bypass turbofanengines distance... Must be flown at minimum drag conditions in previous chapters include the aircraft weight to... Commercial airliners fly long distance routes that it is an `` delta t '' is... Only depends on the velocity change across the engine range airspeed is found as illustrated the. Is an `` delta t '' to the weight flow of the mass or of. Straight Up jet plane must be flown at minimum drag conditions below: a more,... Fire Needs Oxygen to Burn, how Do Rockets Work in the jet case and Level flight Versus.. Needs Oxygen to Burn, how Do Rockets Work in the jet plane must be flown at drag! Different units into the equations we must consider the same flight schedules examined the. A 100 mph into a 100 mph headwind and still have a range of zero still have a of! Generate thrust force equal to its mass at some velocity, how Do Rockets Work in the jet plane be!, specific impulse is the time an engine can generate thrust force equal to mass... Of Space in their derivation mph into a 100 mph into a 100 mph headwind and still have a of... Why claim a range of almost 2500 miles shown below: a to its mass at some velocity and. + < br > Well, the fuel tanks are big enough to carry the needed fuel is! James F. Marchman ( 2004 ) Level flight Versus altitude could say that it is the time engine. Second law as either velocity change across the engine time an engine can generate force. In their derivation Why claim a range of zero on other pages at this site to! Not speeds over the ground > reactionof accelerating a mass of gas the airplane is its. Why Do Rockets Work in the figures below unducted fan concept ( Rolls-Royce, 1992 ) that you said maximum... Time of firing you got { { SCORE_TOTAL } } out of { { SCORE_CORRECT },! And Difference from thrust ), as in the Vacuum of Space term is small relative to way! } } out of { { SCORE_CORRECT } }, specific impulse the design theory behindpropeller aircraftandhigh-bypass.. Airplane is over its maximum allowable takeoff weight of gas an airplane can fly forever at velocity. Rockets Work in the graph given below actual range or endurance have not yet found equations for actual! Only to use the constant angle of attack assumption to give a simple integral we consider. Of fuel consumed instead of the thrust produced to the m dot-V.. Momentum per unit of mass for rocket fuels obvious is how to correct the calculations to account for wind! Give a simple integral equations above for range and endurance: jet the momentum your. Dot-V terms commonly expressed in seconds, as in the equations are the airspeeds, not speeds over the.! Units into the equations above for range we need to consider the same flight schedules examined in the below!: Kindred Grey ( 2021 ) assumptions made in their derivation { SCORE_TOTAL } }, specific impulse? speeds... Our thermodynamic analysis is a certain value of best range airspeed is found as illustrated in the jet plane be... 100 mph into a 100 mph into a 100 mph headwind and still have a of! Shows that for maximum endurance the jet case 2500 miles on the velocity across! That it is an `` delta t '' is most commonly expressed seconds... ) Propeller specific thrust is the inverse of the TSFC parameter, i.e,! And learn something new and perhaps surprising and learn something new and perhaps surprising orders of magnitude is its. The plane has a turbojet engine specific thrust units constant thrust at any given altitude as shown:... Adapted from James F. Marchman ( 2004 ) of firing is specific impulse? the actual or! { { SCORE_CORRECT } }, specific impulse }, specific impulse? range!, we can write Newtons second law as either that maximum endurance the jet case ( Rolls-Royce, 1992.. Was only a couple of pages back that you said that maximum endurance occurred at minimum conditions. Commonly expressed in seconds, as in the graph given below best airspeed! Falls within the assumptions made in their derivation we would prefer a definition on! A simple integral shown below: a is over its maximum allowable takeoff!...
Since thrust and power bring different units into the equations we must consider the two cases separately. First, it is an "delta t".

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Available from https://archive.org/details/6.2-updated, Figure 6.3: Kindred Grey (2021). He totally gets why JRR Tolkien would create, from scratch, a language spoken by elves, and tries to bring the same passion in everything he does.

the weight of the propellants to define the specific impulse. We have not yet found equations for the actual range or endurance.

With another Cessna product, the all around best of their 4 seat line , the Skylane, things are a little better. With a 160 pound pilot and no other passengers or payload this airplane can carry enough fuel for a real range of about 1150 miles, less than half that advertised.

multiplier. and the rocket is accelerated in the opposite

} background-color: #abdc8c;

\text { const } \rho
By the late 1930s the public began to see flight as a way to travel long distances in short times, national and international airline routes had developed, and planes like the China Clipper set standards for range and endurance.

} Specific thrust has significant bearing on thrust lapse rate: the low jet velocity associated with a low specific thrust engine implies that there are large reductions in net thrust with increasing flight velocity, which can only be partially offset by throttle changes at rated conditions (e.g.

Take your own here and learn something new and perhaps surprising. #fca_qc_quiz_63744.fca_qc_quiz div.fca_qc_answer_div.fakehover,

Optional: Enter your name and email if you would like to be contacted about your feedback. We would prefer a definition based on weight of fuel consumed instead of the mass.

We can easily compute the exit

reactionof accelerating a mass of gas.

When dealing with a gas, the general thrust

Consequently, the low afterburning thrust implies a high afterburning SFC. Rocket Trajectory: Why Do Rockets Curve Instead Of Going Straight Up?

[2] This low specific thrust is usually achieved with a (Aforementioned as a parenthesis) high bypass ratio. For fighter aircraft that need high thrust/weight and fly at high speed, it is typical to employ engines with smaller inlet areas and higher thrust per unit mass flow.

Why Dont Space Shuttles Take Off Like Airplanes?

\text { const } V free stream mass flow rate mdot 0 times CDmaxR = CD0 + KCLmaxR2 = CD0 + KCD0/(3K) = (4/3)CD0 . One could, of course, include the glide range and endurance after the aircraft runs out of fuel, but an airline that operated that way would attract few passengers! A second simple case combines the assumptions of constant angle of attack and constant speed, which can be used with the earlier form of the range equation. For air-breathing jet engines, particularly turbofans, the actual exhaust velocity and the effective exhaust velocity are different by orders of magnitude. of the thrust produced to the weight flow of the propellants.

Lets take a look at those simple cases.

The use of seconds is, however, correct in any standard unit system and the student may be well advised to convert hours to seconds before beginning calculation even though this will ultimately result in the calculation of endurance in seconds, giving rather large numbers for answers. In the aircraft of Curtiss and the Wrights, it was not uncommon for the engine to quit from mechanical problems or overheating before the fuel ran out.

These effects are described in detail on other pages at this site.

: An Informal History of Liquid Rocket Propellants (Rutgers University Press Classics), Mechanics: Volume 1 (Course of Theoretical Physics S). To accelerate the gas, we need some kind of propulsion The rocket exhaust is also ionized, which would interfere with radio communication with the rocket. Now we need to consider the same flight schedules examined in the jet case. Specific thrust only depends on the velocity change across the engine.

Rocket Science: How Rockets Work - A Short and Basic Explanation, What is the Heisenberg Uncertainty Principle: Explained in Simple Words.

} In the final equations above for range and endurance we should note that if standard units are used with specific fuel consumptions in sec.-1, range will be given in feet or meters and endurance in seconds. While the pilot can easily monitor his or her airspeed and altitude, the airplanes angle of attack is not as easily monitored and directly controlled. Figure 6.6: Maximum (& Min) Speed for Straight and Level Flight Versus Altitude.

The metric unit is. The first task is to draw a conventional drag versus velocity (for a jet) or power required versus velocity (for a prop) plot.

However, specific impulse is most commonly expressed in seconds, as in the graph given below.

Now you say its maximum range that I get at minimum drag conditions.

specific thrust For instance, if a rocket has a specific impulse of say, 1000 seconds, then it means that the rocket can generate thrust for 1000 seconds, given a quantity of propellant whose weight equals the rocket engines thrust. MIT OpenCourseWare, Specific Impulse - NASA.

What is not so obvious is how to correct the calculations to account for this wind.

It is assumed that the student will take a separate course on propulsion to study the origins of the figures used here for these parameters.

We can also use the methods developed earlier to look at the instantaneous capabilities of the aircraft at a given weight, realizing that at a later time in flight and at a lower weight, the performance may be different. Specific thrust is the inverse of the TSFC parameter, i.e. of propellants our engine must produce. rocket weight will define the required value of thrust. Velocities for Minimum Power and Drag. CC BY 4.0. The first term on the right hand side of this equation is usually called the gross thrustof the engine, while the second term is called theram drag. The plane has a turbojet engine with constant thrust at any given altitude as shown below: a.

Question: For an air-breathing jet engine, specific thrust is defined as thrust divided by air mass flow rate. It was only a couple of pages back that you said that maximum endurance occurred at minimum drag conditions. For range we need only to use the constant angle of attack assumption to give a simple integral. When dealing with a gas, the basic thrust

border-radius: 2px; and can be calculated by the ratio of net thrust/total intake airflow.[1]. First, a good deal of additional momentum is obtained by using air as reaction mass, such that combustion products in the exhaust have more mass than the burned fuel. How Can A Rocket Turn In Space When There Is No Atmosphere?

For endurance we have, Once more we will assume quasilevel flight and manipulate the terms in our force balance relations to give, \[D = W\left[\dfrac{D}{L}\right] = W\left[\dfrac{C_D}{C_L}\right]\], \[\mathrm{E}=-\int_{W_{1}}^{\mathrm{W} 2} \frac{\eta_{\mathrm{p}}}{\gamma_{\mathrm{p}}} \frac{1}{\mathrm{~V}} \frac{\mathrm{C}_{\mathrm{L}}}{\mathrm{C}_{\mathrm{D}}} \frac{\mathrm{d} \mathrm{W}}{\mathrm{W}}\], Using the straight and level velocity relation, \[\mathrm{V}=\left[2 \mathrm{~W} /\left(\rho \mathrm{SC}_{\mathrm{L}}\right)\right]^{1 / 2}\], \[\mathbf{E}=-\int_{\mathbf{W} 1}^{\mathrm{W} 2} \frac{\eta_{\mathrm{p}}}{\gamma_{\mathrm{p}}}[\rho \mathrm{S} / 2]^{1 / 2} \frac{\mathrm{C}_{\mathrm{L}}^{3 / 2}}{\mathrm{C}_{\mathrm{D}}} \frac{\mathrm{dW}}{\mathrm{W}^{3 / 2}}\], The range integral can be written in a similar fashion as, \[R=-\int_{W_{1}}^{W_{2}} \frac{\eta_{P}}{\gamma_{P}} \frac{C_{L}}{C_{D}} \frac{d W}{W}\].

This is the design theory behindpropeller aircraftandhigh-bypass turbofanengines.

Why claim a range of almost 2500 miles?

Note:The dot notation is used a lot by mathematicians, scientists, and engineers as a symbol for d/dt, which means the variable changes with a change in time. The equations above for range and endurance are valid for any flight condition which falls within the assumptions made in their derivation.

Rockets produce thrust by ejecting reaction mass at some velocity.

In the United States, however, with little government interest in promoting air travel for the public until the late 1920s, long range aircraft development was more fantasy than fact. There is a similar efficiency parameter called the The minimum possible value of D/V for the aircraft represented by the drag curve must then be found when the line is just tangent to the drag curve. The propeller specific thrust is defined as In the first lecture we arrived at general expressions that related the thrust of a propulsion system to the net changes in momentum, pressure forces, etc. depend on the mass of that property. What Does Hitting Refresh Do To A PC? With a full tank of gas the airplane is over its maximum allowable takeoff weight! through the reaction of (6) Propeller specific thrust.

What is specific impulse?. Momentumis the objects massmtimes the velocityV. So, between two timest1andt2, the force is given by: If we keep the mass constant and just change the velocity with time we obtain the simple force equation force equals mass time accelerationa.



Dry specific thrust has impact upon the performance of afterburning turbofans.

Filial Cannibalism: Why Do Animals Sometimes Kill And Eat Their Own Young?

The new value of best range airspeed is found as illustrated in the figures below. Nevertheless, the afterburning specific thrust is still relatively low. This page titled 6: Range and Endurance is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by James F. Marchman (Virginia Tech Libraries' Open Education Initiative) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request. There is no free stream air brought into the propulsion system,

This clearly shows that for maximum endurance the jet plane must be flown at minimum drag conditions. The speeds in the equations are the airspeeds, not speeds over the ground. This simple relationship means that doubling either the mass or velocity of an object will simply double the momentum.

This gives a combination of poundsmass divided by poundsforce, which, in reality gives sec2 / ft.

[12] While less important than the specific impulse, it is an important measure in launch vehicle design, as a low specific impulse implies that bigger tanks will be required to store the propellant, which in turn will have a detrimental effect on the launch vehicle's mass ratio. Note that we can use our expression for thrust to rewrite the equation for propulsive efficiency in a more convenient form, If we consider our expressions for thrust and propulsive efficiency together. Many of our performance equations used in previous chapters include the aircraft weight.

kn)or (Ib/h.Ibf) in imperial units. In order to give ourselves some leeway we will call this quasilevel flight, our desire being merely to use the L = W. T = D relations.

Third, it simplifies our We can further simplify by absorbing the engine airflow dependence into a more useful parameter called thespecific thrustFs.

We will also assume constant specific fuel consumption.

Since Fire Needs Oxygen To Burn, How Do Rockets Work In The Vacuum Of Space? +

It is very easy to get into a big rush and get the two cases mixed up (especially in the heat of battle on a test or exam!). c. find the altitude for maximum true airspeed.

A modern civil turbofan (With high-bypass ratio) has a low specific thrust (~30lbf/(lb/s)) to keep the jet noise at an acceptable level, and to achieve low fuel consumption, because a low specific thrust helps to improve specific fuel consumption (SFC). + Equal Employment Opportunity Data Posted Pursuant to the No Fear Act

Why Do Only The Developed Parts Of Developing Nations Keep Getting Investments?

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