the power of jet engines...

[SkippyX]

I have a reasonable idea of what 60,000lbs of thrust means for a 747 engine, I think. But I try to explain to a friend and it means nothing. Anyone know any good analagies that help appreciate the power and energy used during a 7/8hr flight?

I once heard sth like the fuel used by a B747 flying LHR - JFK would take a car to the moon and back, if there was a road! Any others?

[fifthcolumns]

After 14 years working with jet engines. The
only one I can remember is that at
take off power a JT9D use 4 gallons
a second, US gallon that is.

Well I'm impressed.

[captain marvellous]

Thrust is FORCE.

If you had, for example, 10,000 pounds of thrust available then that would be sufficient to be able to hold up an object weighing 10,000 pounds. If you had 10,001 pounds of thrust then you could RAISE a 10,000 pound object off the ground, and then hold it above the ground.

So a 747 with 60,000 pounds of thrust per engine (or about 27,300 kilograms if you prefer) could LIFT a 27,299 kilogram lorry off the ground and HOLD up.

747 has four engines each with about 60,000 pounds (27,300kg) of thrust you say? Well thats a total of 4 x 60,000 = 240,000 pounds (or 109,000 kg if you like).

If it helps with perspective, most articulated lorries have a gross vehicle mass of about 40,000 kilograms, or 40 tonnes.

[52049er]

Im sure someone once told me that at a certain altitude a jet engine of 5000lbs produced the same thrust as 4 X 2000hp piston engines with very efficient props.

Not sure if its true though. He might have been the same bloke that got a 319 stuck in a (an?) hold.

[ual757]

here's a good example (the comment is by yours truely)
http://www.ilovebacon.com/vehicles/070500.shtml

[Spam Fritter]

all I know is that jets produce alot of hot air.....

[Dorfer]

Refering to my trusty P&W Handbook the relation between thrust is expressed by the following: THP = F x mph/375 Where THP is Thrust Horse Power, F is thrust in pounds and mph is miles per hour. Doing the math on a 60,000 pounder going at M.80 at MSL one would arrive at 97,000+ horse power. A figure that I cannot relate to. I kinda like the 4 gal per second thing.

[Zulu]

Aren't there some other gems, like a B747-400 at idle power, produces more power than a Trident did at full power, or some such like?

[Thrust]

If an engine is producing 60,000lbs at MSL what is it producing at altitude at M.80? I suspect we would all be suprised at the very low figure. Any enlightenment out there?

[This message has been edited by Thrust (edited 18 October 2000).]

[jtr]

HP= TV/325 (I think the 375 someone mentioned above is for mph)

because w =Fd

and Power = w/t = Fd/t

and V=d/t

so Power also = FV or TV

so using 1 HP = 550 ft-lb/sec

HP = TV/550

or in knots HP=TV/325

Doesn't help with the mental imagery though, as a -400 at 1 knot msl/isa etc is putting out around 700 ponies, whilst at 340 kts it's pumping 230,000 horses.

[CaptainSquelch]

A CF6-50 on T/O thrust displaces about 600 cubic meters of air per second.

really a lot of hot air.

[captain marvellous]

In the end they are all noisy BRT's. (big round things)

[enginefailure]

If a 747 applies full thrust,
1.000 woman 100 meters away could
dry their hairs ........

isn't that an impressive example ?

cheers
ef

[Horsepower]

EF,
Shouldn’t that be ‘fry’ their hairs?

[Desk Driver]

If you could fill up your Ford whatever with the same amount of full as a B744 and you drive an average of 10'000 miles a year. You would'nt need to re-fill for a 144 years.


------------------
-------------------------
You fly em we'll fill em!

[Shaggy Sheep Driver]

A Rolls Royce engineer was interviewed on telly recently, and he held a blade (about 3 inches long) out of the power turbine in a Trent engine in the palm of his hand. Can't remember the exact text but I think he said that one blade took the same power out of the gasflow as a Formula one racing engine develops. And it sits in a gasflow which is at a temperature of more that twice the melting point of the blade. It's only because the blade's air cooled internally that it doesn't instantly melt.

Amazing stuff.

SSD

[Goldie]

A level 3 Mc Donalds could fry up 37065208 Big Macs with the fuel capacity of a 737? Fact or Fiction

[Unwell_Raptor]

Goldie -

I think you made that up.

[enginefailure]

No goldie!

It are 74.130.416 cheeseburgers !!!

[FL390]

Now, with a Rolls engine, at take off, the amount of 'suction' from this 747 engine will suck a person in from 8ft. and throw them out 120ft. the other side!!!!!!

Perhaps they could make it a new theme park attraction???!!!

[redtail]

FL390
I'd rather be the guy at P&W who gets to shoot the bird and blow up the fan blades. What a fun video.

(I really like shooting the bird. You'd be surprised on how many people are "number one" with me.)

[Vlieg]

For what I can remember from those days back
at school: 60.000lbs x 4,5 = 270.000Newton
and one Newton is defined as being able to
accelerate an object weighing 1kg with 1 meter per sec. square!

Always look left! Peet.

[Loc-out]

Compared to the power of the Saturn 5 rocket the power of a jet engine is rather insignificate don't you think? It's all relative. Like the size of the A/C you fly.

[AVPIN]

Vlieg

I think that you are very sad remembering useless formula like that..

Anyway, I make it 267,545.45N

Even sadder

[Big Red ' L ']

On the subject of engines, I know a woman in Bangkok who could suck start a Harley......

(A bit off subject i know but what the f***) ;-)




------------------
Its not the fall that kills you...Its the sudden stop.....

[Streamline]

I know one next to me.

[carpe.d.m]

THRUST
I think I have an answer to your query.Yes,it is v.interesting.It is a concept/fact we should be aware of.It really suprised me.

The RB-211 is rated 58,000lb. SL.By-pass ratio 4.3

35,000ft. 0.85 M max cruise thrust 12,708lb.

Official Rolls Royce figs.

[maxmobil]

jtr,
we also had some discussions about power/thrust conversion. The interesting and somehow irritating fact is that a jet engine produces maximum thrust ( full rated T.O.) while at zero speed, thus has NO power in means of physics; while it accelerates the thrust is decreasing, but the power equivalent is increasing, and there are formulas to calculate the power needed to sustain a certain speed.

With all the factors supplied for a certain engine type You can figure out a quite accurate conversion rule, e.g. for the CFM 56 engine it is something like fuel flow (kgs/h) x 4,3 = Horsepower equivalent; but as said, this number only applies to this engine. Older engines with a much worse fuel efficiency need a smaller number to convert.

Hope it helps

[Lu Zuckerman]

The easiest way to demonstrate thrust is to blow up a balloon and let it go. It will fly all over the place. The most common thought as to why the balloon is propelled forward is that the air is flowing very rapidly from the the narrow neck of the balloon. Some people will extrapolate that the ballon example can be applied to a jet engine. If they did, they would be wrong. An example of this error would be to have them explain how a rocket engine can work in outer space where there is no field of air to react against. The real thrust comes from the pressure exerted on the forward wall and side walls of the combuster. Each can or on an annular can represents a rocket engine. The exhaust from the combuster flows through a turbine which drives the rest of the engine (Fan and Compressor). There is a pressure differential between the forward wall of the can and the rear end of the can which resultst in a pressure differential. The pressure on the forward wall of the can is much greater than the pressure at the rear of the can. Since the combuster can(s) are attached to the engine and the engine is attached to the wing this pressure differential forces the airplane forward. The fan acts as a propeller and it too is attached to the engine and it provides an added force moving the aircraft forward just like a propeller on a conventional aircraft. Use the formulae to calculate the thrust assuming you have all the figures, but if you want to explain a jet or, a rocket engine to your friend use this.

Here is a little gem. An Atlas rocket engine that generates 150,000 pounds of thrust only has an internal pressure of about 600 PSIA. This pressure working against the surface area of the forward or, upper wall of the engine and the wall of the exit nozzle is what creats the force. Do the math. The forward or upper wall has a surface area of 250 square inches or there abouts. Also the higher the rocket goes until they get up to the top of the atmosphere the faster the gas flows out of the nozzle creating an even higher differential increasing the thrust over the level generated at sea level which is somewhat lower than the rated 150,000 pounds.

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The Cat

[This message has been edited by Lu Zuckerman (edited 23 October 2000).]

[This message has been edited by Lu Zuckerman (edited 23 October 2000).]

[Checkboard]

Nice thought Lu, but a balloon would work even better in space than in your average room.

The jet of air from the neck of a balloon is the same as a jet of air from a jet engine (that is why it is called a jet engine!)

[Lu Zuckerman]

To: Checkerboard

Dear Check,

The air rushing out of the neck of the balloon is not reacting against the surrounding air. It is the pressure differential between the front of the balloon and the rear of the balloon. What you said about the balloon in outer space is true. The pressure differential would be greater due to a lack of surrounding atmosphere and the absence of any drag.

When fluid is contained under pressure the internal pressure acts at right angles to the containing wall. That means that when the container is sealed the pressure on the containing walls is equal. When you open up one end of the container the fluid under pressure flows out of the opening and the differeential pressure between the front and rear causes the container to move in the direction of the highest pressure.

Whether you are talking about a balloon, a rocket engine or a jet engine the principle is the same.

------------------
The Cat

[SRR99]

Lu,

You're right, the jet is not reacting against the air outside and rockets, balloons and turbine engines do operate off the same principle, but you're wrong about the pressure differential providing the thrust.

The engines and balloons that you talk about derive their thrust by the momentum change, or accelaration, of a mass of working fluid. At the end of the day, you cannot go faster forwards tham you are propelling gas backwards. Previous threads have discussed how thrust decreases with increasing forward speed. This is precisely because the momentum change imparted is decreasing, and the exhaust gas is leaving backwards at speed cancelled out by the forward speed

Supersonic jets have to propel gas backwards fast (e.g. Concorde, military jets)because their ultimate speeds are higher (that's also why they are so noisy when they pass you on final approach - the high jet speed creates lots of turbulence which you hear as rumbling noise), but Commercial airliners impart lower accelerations to larger amounts of gas - higher bypass ratios gas turbines and propellers.

The engine is not "sucked forward" as other threads have alluded to - they are propelled forward by the acceleration of gas through some kind of nozzle (momentum change).

This is also demonstrated by the reaction on a constricted hosepipe. Where is the pressure on the "forward wall" of a hose? At the pumping station. Where is the acceleration of the water? In the nozzle. So where is the force developed? In the nozzle, which is why the nozzle flicks around, not the rest of the hose.

[John Farley]

I think there is a tad more to it than thrust always drops off from the static case as aircraft speed builds up.

The intake has a part to play in obtaining the eventual compressed air that the engine uses to keep itself pumped up (using the everlasting balloon analogy) While the increase in efficiency of overall compression due to the intake as speed initially builds may not be huge, the compressor can still do better when it does not have to suck all the air in. A bit of ram is helpful.

Once the speed builds the increasing drag effects will quite soon overwhelm the benefits of feeding the compressor better. Once you are supersonic though its all change and the intake provides perhaps 40% of the necessary compression – check with WOK if you doubt that.

[Lu Zuckerman]

If what you say is true then you are stating that the jet exhaust propels you forward and not the pressure differential between the forward wall of the combustor can and the lower pressure due to mass acceleration. If you had a means of generating gas pressure separate from the nozzle and introduced that pressure the gas would be expelled from the nozzle and the reaction would move the nozzle forward. That is how a pneumatic tip jet helicopter works. The gas pressure inside the engine drives a compressor and the compressed air drives the blade forward. I think there was some Greek or Roman by the name of Hero that demonstrated this theory. Werner Von Braun and later on a company called Rocketdyne adapted this principle and sent men to the moon (assuming you believe that). I think Mr. Newton said that for every action there is an equal and opposite reaction. In this case, the expelling of the gas from the combustor creates this differential and it is the force imbalance between the forward wall of the containing vessel and the exit nozzle. The faster you can expel the gas the greater the pressure drop at the nozzle which increases the differential. Since the containing vessel is attached to the conveyance it propels, the conveyence is moved.

I saw on another posting on this thread and it had as picture of a jet engine
with the pressure levels at different points in the engine. If I remember correctly, the internal pressure peak in the combuster was 250 PSIA. As I said previously the internal pressure in an Atlas rocket engine was 600 PSIA and that created 150,000 pounds of thrust. Efficiency in a rocket engine is measured by dividing the thrust by the amount of fuel and oxidizer that is pumped into the engine. It is refered to as ISP or Specific Impulse. If you are right, then Von Braun, Rocketdyne and all of the other rocket scientists are wrong.

Here is a point I should have brought out earlier in this posting. Are you familiar with a pulse jet. If you are old enough you would remember that they did a lot of damage in the UK and parts of Europe. These jets are started up on the ground. Just before start up, you could look through the engine from front to back with minimal restriction. However once the combustion pressure builds louvers at the front of the engine are closed due to the increase of pressure. Under full combustion the pressure builds and the gas is ejected rearward and the the V 1 is shot off a ramp at a very high cyclical rate the internal pressure drops and the louvers open letting in ram air at a fairly high pressure. Ignition takes place and the louvers close allowing the pressure level to raise again propelling the rocket forward. If the louvers did not create a forward wall to allow pressure build up the rocket would have fallen into the water or, not even started. It is that forward wall that takes the reactive force and transfers it to the airframe structure. A more simple system is the ram jet which has no moving parts. However it is the ram effect that creates the forward wall just like the pulse jet louvers. Only in this case the propulsive force is much greater as is the speed of the rocket.

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The Cat

[This message has been edited by Lu Zuckerman (edited 28 October 2000).]

[This message has been edited by Lu Zuckerman (edited 28 October 2000).]

[alosaurus]

SRR99-Have to agree with Lu on this.A bit dodgy comparing compressible gas and a liquid .If the hose were in a straight line it would not move.

[SRR99]

Just read the text books. Don't get confused between compressible and incompressible. It alters things a bit, but not the fundamentals. These engines/motors are momentum change devices, and they rely on Newton's Laws of motion.

Also, if the hose were in a straight line, the force would still be there, but the hose would be restrained by the body of the hose itself!

All the basic equations of thrust, as shown in previous threads, relate to mass flow, and the exhaust velocity and the forward velocity, and the density, and things that affect density, like temperature (remember the thread about water injection - it's a bit like an intercooler in a car, it cools the air after compression and raises the density. It also drops the pre-combustion temperature, which increases the change in temperature pre- and post-combustion. This is a fundamental determinant of thermodynmaic efficiency).

Don't take my word for it, read a physics text book, or "The Jet Engine" by Rolls-Royce.

Also, in terms of the original question, am I right in thinking that the combustor of an RR Trent 700 or the like is working at a rate of something like 170MW (I'm not so sure about this - I read it on the back of a matchbox) - try relating that to a power station or the power consumption of a town.

[SRR99]

You ask if I am familiar with a pulse-jet, with its spring-loaded louvres. I am, but are you familiar with a ramjet, which has no forward walls at all? How do you explain that?

The engine designer uses a subtle blend of pressure, velocity and temperature distributions, something along the line of Bernoulli's theorem. The highest pressure, is actually just aft of the compressor, and before the combustor cans or rings, not in the combustion chamber.

Speeding gas up drops its pressure, while slowing it down increases it. That is why there are components with names like nozzles and diffusers. Diffusers expand the gas, slow it down, and drop the static pressure. Nozzles tend to do the opposite, and direct the flow in the desired direction.

In spite of the general acceleration of gas in all of these engines which creates a forward force, there is an element in rocket engines and afterburners where the acceleration of the gas is not the only force. There is also an element, especially in rocket engines, where the gas exerts pressure on the divergent part of a convergent/divergent nozzle which als propels it forwards.

Of course I believe in Herr von Braun, and of course I recognise the use of rockets. I'm not so sure that you have interpreted them correctly.

Again, I refer you to "The Jet Engine" by Rolls-Royce, especially the Chapters on "Basic Mechanics", "Working Cycle and Airflow", "Afterburning" and "Performance".

I have only relayed what they say, so if you have a better idea, then let them know :) :) :)

This is a good discussion, because everyone truly seems to have a different interpretation. Even the folks who make the things have good arguments about it from time to time, but don't let that put you off flying!

[Lu Zuckerman]

To: SRR99

If you will refer to several threads above I stated that pressure is exerted at 90 degrees to the containing vessel and I also referenced a ram jet engine. Regarding the pressure acting at 90 degrees to the containing vessel this applies also to the DeLavall nozzle used on a rocket engine.

Some of the force is exerted at a vector in relation to the center line of the rocket engine so that some of the forward thrust is exerted by the expanding gas in the nozzle itself. However, the greatest forward thrust is exerted on the forward wall of the rocket engine or to be more specific at the fuel and oxidizer injection plate.

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The Cat

[SRR99]

Lu,

I refer you again to the chapters in "The Jet Engine" by Rolls-Royce. Are they wrong?

They also seem to think that they know something about rockets, although they don't seem to have the knowledge that you do.

Both GE and Rolls-Royce books refer specifically to the mass flow and acceleration.

Perhaps you could argue that as the fluid naturally goes from an area of high pressure to one of low pressure then it accelerates. You can calculate the thrust or drag of an aircraft engine in each section (inlet, compressor etc), but the overall engine works on the acceleration of gas. Even turbine stages rotate not only by changing the direction of flow, but also by presenting a converging path to the gas which accelerates the gas and forces the rotor in the opposite direction.

I don't know your experience and you don't know mine, but like I say, read the book, and then tell me where you agree or it's wrong. :) :) :)

[Mach.80]

I seem to vaguely remember hearing once that a 747 engine expels something like about 7 tonnes of air in its take off run, or per minute, or something like that. I can't remember exact details. Is that
true, or just a load of hot air?

Help me out here.....

[Lu Zuckerman]

To: SRR99

Please tell me if your books can tell you if it is possible to expell this high velocity gas from a rocket engine or a gas turbine engine that is open at both ends. On a gas turbine engine I am speaking about the combuster can(s) and on the rocket engine I am speaking about the upper end of the engine combuster not being there. In order to expell the gasses, the gasses must be generated in some sort of container that will allow pressure to build up. Once again I don't disagree with what you are saying as it is the expulsion of a large mass of hot gasses that make these engines work. My point is with out the front end of the combustor there would be nothing to allow the creation of the high pressure and high velocity gasses in the first place.

For every action ther is an equal and opposite reaction. The hot gasses flow out and the pressure differential works against the forward wall and is transfered to the attaching structure. Whatever is attached to that structure is caused to move. The amount of work that is done is pressure times surface area. Getting back to the previous posting, because pressure is exerted at 90 degrees to the containing vessel some of the force cancels out the forward motion. All of these elements must be factored in to determine how much useful force is actually developed.

By the way, I was a techrep on the Atlas for three years and I worked as a project engineer on the Saturn SIV-B at Douglas and NASA MSFC for six and a half years, and no I am not a rocket scientist.

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The Cat

[This message has been edited by Lu Zuckerman (edited 29 October 2000).]

[This message has been edited by Lu Zuckerman (edited 29 October 2000).]

[alosaurus]

SRR99-Lu is correct.Also,as I said, your hose pipe analogy is inappropriate in this case.With a liquid as flow increases,temperature increases whilst viscosity and resistance decrease.With a gas the reverse is true.

[AVPIN]

Jet V Rocket engine explanations seem to be getting very complicated.

Try these analogies - they work for me

JET engine-

Sit on a kids skate board - pick up brick from ground - throw brick backwards - you go forwards. Repeat for continuous motion.
Bricks = AIR, energy used to throw brick = FUEL
Run out of either and you stop.


ROCKET engine-

Sit on the same skateboard, this time with a pile of bricks on your lap - throw bricks backwards one at a time - you go forwards.
In this case, Bricks and fuel need to be treated as one and the same - in a rocket engine, the fuel is both the energy source AND the accelerated mass. (OK-perhaps not in ION propulsion)

Too simple ?

[18Wheeler]

FWIW, you can get a gadget that stick onto the window of a car to tell you how much horsepower it has. It's a little thing with a reasonable accurate accelerometer, and you feed in the weight of the car and accelerate away, and after a few seconds it'll tell you how much power you used to accelerate that amount of mass that fast, etc.
It's called a G-Tec, and I popped it up on the window of a 747-200, powered by RR RB-211 D4X's, 53,000 lbs rated for T/O.
Allowing for a little derate, I got a grand total of 72,000 hp!

[Old Dog]

Lu, I agree with SRR99 fully. He has stated clearly all I would have said anyway. Force is derived from acceleration of some mass, F= ma, as stated by Newton.

You were a tech rep (read: salesman) with the rocket maker? You would have more credibility if you were the rocket scientist. I bet you did not major in mechanical engineering or applied maths. You knowledge of mechanics were too primitive.

(edited for typos)

[This message has been edited by Old Dog (edited 08 November 2000).]

[Old Dog]

Deleted due double posting.

[This message has been edited by Old Dog (edited 08 November 2000).]

[Old Dog]

Lu I am sure you did not qualify in mechanical engineering. If indeed you have a degree in engineering, it would be in electronics or something else. Your did not know about F=ma, no surprise.

SRR99 is correct.

[SRR99]

I've been having a nap, but I'm back.

Alosaurus, the hosepipe analogy stands. Forget the water if that causes confusion....Consider a hose, full of air.

Lu, I understand part of what you're saying, but to use your own example, a ramjet is indeed open at both ends, and yes "The Jet Engine" by Rolls-Royce does say that a ramjet, which is open at both ends, does work. Let's not compare credentials, because I think that the authors of that book have bigger ones than you, and I don't even want to talk about mine :) :) :)

Read the book for yourself!

Also, while you obviously know quite a bit about rocket engines, you are comparing apples with oranges when you say that the combustor cans develop the force in a turbine. The combustor can/annulus is a very open framework whose purpose is to promote efficient combustion. It is not a pressure vessel. It sits inside the combustor case, which is a pressure vessel, but which is also open at both ends. The compressor in front of it takes the place of the ram effect and subsequent diffusion that occurs in the pure ram jet.

I'm still interested in where the force is actually transmitted. Is there anyone out there? :)

[18Wheeler]

The compressor blades do all the 'pushing'. There's also a fair amount of plain jet thrust (no pun intended) from the combustors, but the turbine soaks up a rather large chunk of all that forward thrust, leaving the left-overs for forward 'push'.

[Lu Zuckerman]

To: SRR99

It is true, that a ram jet is open at both ends. However when combustion takes place the hot gasses can't be expelled from both ends as to do so there would be no propulsive force. It is the pressure entering the front end that acts as a forward wall during combustion which provides a "forward wall" to react against. That is why it is called a "ram jet".

This ram effect is the same as the louvers in the pulse jet but in this case, there are no moving parts. There is also a device called a flame holder which assists in maintaing the flame front.

The combustion cycle is not continuous. As each combustion cycle takes place the flame front (pressure pulse) passes down the tube and in doing so reduces the combustion pressure in front of the flame holder and the pressure drops allowing ram air pressure to enter the tube and the whole thing starts over again. The flame holder also maintains a part of the fire providing an ignition source for the next combustion cycle.

Regarding the combuster cans, they are full of holes which it would seem would allow the combustion gasses to escape and flow forward as well as back. What keeps this from happening is the compressed air that is being forced into the combusters by the compressor thus creating a closed container.

If this wall of pressure is ever disturbed due to an aerodynamic problem in the compressor section the flame would shoot out of the front of the engine.

------------------
The Cat

[Old Dog]

On a different note: I was in Taiwan a few months ago, and I read in the local news that The Taiwanese military have successfully flight trial their supersonic missiles, powered by maybe ram jet or pulse jet (they didn't say in the non-technical papers). If that was true, that made them (the Taiwanese) the third country in the world to have successfully made a ramjet engine, after the USA and Russian.

[Old Dog]

SRR99: while I agree 100% with you, I noted an error in one of your post on 29 October (3rd para):

Speeding gas up drops its pressure, while slowing it down increases it. That is why there are components with names like nozzles and diffusers. Diffusers expand the gas, slow it down, and drop the static pressure. Nozzles tend to do the opposite, and direct the flow in the desired direction.


Was it a typo, or did you really meant that?

[AVPIN]

Old Dog wrote:

On a different note: I was in Taiwan a few months ago, and I read in the local news that The Taiwanese military have successfully flight trial their supersonic missiles, powered by maybe ram jet or pulse jet (they didn't say in the non-technical papers). If that was true, that made them (the Taiwanese) the thirdcountry in the world to have successfully made a ramjet engine, after the USA and Russian.

Sorry, can't allow that statement to stand.

What about the BRITISH built ramjets such as the RR/Bristol Thor as used on the Bloodhound SAM back in the 60's ?

Sorry - VERY proud of British achievements

AVPIN

[SRR99]

Old Dog,

Yes it was a typo - slowing the gas down raises its pressure. Thanks.

Lu,

I responded to your question about whether a device which is open at both ends can provide forward thrust. I do know how these engines work.

I just find some of your explanatins lack clarity, which is why I refer everyone to the books I mention.

[Old Dog]

AVPIN, thanks for the info. I stand corrected.

BTW, is the Thor powered Bloodhound Missile you mentioned still in service ? Just curious.