F-14 Space Launch Vehicle

Originally posted by esecallum
RICHARD CLAIMS

*snip*


Richard your calculations are totally wrong and flawed....AND APPLY TO THE SHUTTLE ONLY.!!!!

the 747 as it exists carries enough fuel in its wings to last for at least 10 hours...
modified versions can last for 20 hours....

I dont need to look it up, I work close to the aviation industry and my figures are 100% correct.

The 747 has a maximum capacity of 216,840 litres. Thats all, total.

It has wet wing tanks and a centre belly tank.

And in any case it simply cannot carry the weight of fuel required.

upto 50000 feet going upwards at a speed of 500 mph takes how long does it take richard??

A 747 takes a good part of an hour to reach its cruising altitude of about 40,000 feet at its maximum takeoff weight of 413,000kg.

A 747 does not have a climb rate of 500mph.

from above 50000 feet to 400000 feet using onboard oxidizer how long does it take travelling at 500 mph..?

It will never get there.

then from 400000 ft to 23000 MILES how lon does it take a 747 ACCELERATING IN FREE SPACe WITHOUT ANY DRAG ON SUSTAINED THRUST?

What sustained thrust? The engines are high bypass, it wont be producing anywhere near enough thrust to exceed the pull of gravity. The result will be an airframe stall, and a rapid descent.

if you work it out the flight duration is about 2 hours and yet a 747 can sustain thrust for 10 hours minimum......

do you see now?

Obviously you dont see.

your calcultions about 8 million litres are connected to that space shuttle...this not the same...
its a winged vehicle based on continous efficient sustained thrust....

How is it not the same? The Space Shuttle uses 2 million litres of fuel and oxidiser, are you saying the 747 is somehow magically exempt from the laws of physics and can do it on less than an 8th of that?

The wings wont produce lift after a certain altitude, and thats well well below 100,000ft for that airframe. The aircraft would come back to earth very fast.

Why arent NASA using this?! Why arent Boeing using this?! Why arent EADS using this?! Why arent Lockheed using this?!

Cheap space flight is a holy grail - if it could be done as simply as you seem to think, then why arent people doing this? Why are hundreds of satelites being launched a year on expensive rockets?

What drugs are you on? Have you missed a dose?

I can see another problem with this concept, I'm sure others can see it too:

The 747 has an MTOW of around 413,000kg. The speed being proposed is 7,800m/s. For this I'll round the mass in space to around 250,000kg.

Using a simple equation, K.E. = 0.5 x 250000x 7800^2 = 7.605x10^12J
Or 7.605 TERAJoules. If you can get that much energy from the fuel load of a 747 I'm impressed. And this is ignoring air resistance, assuming the whole thing was done in a vacuum.

And I personally don't remember ever seeing a 747 do a 45 degree climb, even at takeoff.

Originally posted by RichardPrice

Originally posted by esecallum
RICHARD CLAIMS

*snip*


Richard your calculations are totally wrong and flawed....AND APPLY TO THE SHUTTLE ONLY.!!!!

the 747 as it exists carries enough fuel in its wings to last for at least 10 hours...
modified versions can last for 20 hours....

I dont need to look it up, I work close to the aviation industry and my figures are 100% correct.

The 747 has a maximum capacity of 216,840 litres. Thats all, total.

It has wet wing tanks and a centre belly tank.

And in any case it simply cannot carry the weight of fuel required.


why? the 747 is empty inside where the passengers sit and whre the lggage is carried and all that empty space cannot carry oxidizer to use above 50000 feet...

well??

upto 50000 feet going upwards at a speed of 500 mph takes how long does it take richard??

A 747 takes a good part of an hour to reach its cruising altitude of about 40,000 feet at its maximum takeoff weight of 413,000kg.

A 747 does not have a climb rate of 500mph.

even at 45 degrees....?? come on u r being wrong again..

from above 50000 feet to 400000 feet using onboard oxidizer how long does it take travelling at 500 mph..?

It will never get there.

you never gave a reason...why? maybe you dont have one??

then from 400000 ft to 23000 MILES how long does it take a 747 ACCELERATING IN FREE SPACe WITHOUT ANY DRAG ON SUSTAINED THRUST?

What sustained thrust? The engines are high bypass, it wont be producing anywhere near enough thrust to exceed the pull of gravity. The result will be an airframe stall, and a rapid descent.

but you keep forgetting AT THAT POint onboard oxidiser is being used to burn the fuel to provide thrust...
and the 777 engines or similar can eaily provide 129000 pounds of thrust each....so 4 x 129000 will support the 747 without wings.......enough for vertical flight...

if you work it out the flight duration is about 2 hours and yet a 747 can sustain thrust for 10 hours minimum......

do you see now?

Obviously you dont see.

esecallum, you either need to pass puberty or you need to get an education.

Its as simple as that.

Im not going to spend any more time on this, I have given you reasons why it wouldnt work and you rejected them out of hand without even understanding them.

A 747 to orbit under its own power would not work, period. Thats it, theres nothing more to say.

Originally posted by esecallum

What sustained thrust? The engines are high bypass, it wont be producing anywhere near enough thrust to exceed the pull of gravity. The result will be an airframe stall, and a rapid descent.

but you keep forgetting AT THAT POint onboard oxidiser is being used to burn the fuel to provide thrust...
and the 777 engines or similar can eaily provide 129000 pounds of thrust each....so 4 x 129000 will support the 747 without wings.......enough for vertical flight...

Don't you understand what high bypass means? It means that most of the air going into the engine is bypassed, so it doesn't enter the combustion chamber, which is what you are suggesting you do with your onboard air, so you would get about a 1/10th of the thrust in the atmosphere.

This means it won't produce enough lift from the engines. If you can produce some system that would get a 747 into space using any type of engines that would not need a massive fuel capacity, then it would have been done.

About the only way to get enough energy out of the engines without exceeding the maximum take off weight would be something like a nuclear powered jet, but again it needs an atmosphere.

esecallum, all jet engines work on the basis of accelerating air through them, then newtons laws take over (equal and opposite reaction).


Without any air to accelerate, the engines you propose will only be accelerating the oxygen and fuel you have provided from within the aircraft - which is no different to a liquid fuelled rocket.



Boeing 747-400:

The most powerful engines are:
4x 275.8kN (62,000lb) PW-4062s

giving a total thrust of just over 1100 kN

The MTOW (depending on various options) is around 380,000kg (multiply by gravity to get 3,800,000 N, or 3800kN, giving a power to weight ratio of just under 0.3 - which is inline with pretty much every other commerical airliner in existence.

It will not climb at angles approaching 45 degrees, it simply does not have the thrust available to do so. Simply working through the mechanics of an aircraft in climb at 45 degrees means that the thrust available (T) must equal the longitudinal (with respect to the aircraft axis) component of the weight (mg) through the aircraft.

T = mg*cos45

T = 380,000 * 10 * cos45
T = 2,687,005 N = 2,690 kN

whereas the 747 only has around 1100 kN - which is well short.

Originally posted by kilcoo316
esecallum, all jet engines work on the basis of accelerating air through them, then newtons laws take over (equal and opposite reaction).


Without any air to accelerate, the engines you propose will only be accelerating the oxygen and fuel you have provided from within the aircraft - which is no different to a liquid fuelled rocket.

What is your obsession with air??

jets work by combusting fuel with air or the oxygen in the air...
the explosive hot gases jet from the nozzal to give thrust...



above 50000 feet no air so you use onboard oxidiser...to replace air or oxygen...

your turbofan is using energy from fuel/air combustion to turn the fans...so its NOT FREE which you seem to think...

jet/rocket/liquid fuel whatever its called all it need to provide net lift at angle of about 45 degrees...
i have seen hundreds of times 747 taking of from runways at nearly an angle of 45 degrees...and yet you lie saying it cant do that...
another member above claimed the 747 would collapse...!!!

in any case what label u put on it must provide thrust as specified above...

i mentioned te 777 engines which can generate 129000 ibs of thrust
4 engines can lift a 747 vertically
as the weight varies between 400000 to 700000 for a 747...

in your desparate haste you cant even read what written...

[mod edit: in bold]
Mod Note: General ATS Discussion Etiquette – Please Review This Link.

[edit on 1/24/2007 by 12m8keall2c]

Please consider the ATS motto... Deny Ignorance...

www.aerospaceweb.org...

www.grc.nasa.gov...

Please note that thrust is computed as a function of inlet flow; no flow, no thrust...

An oxidizer would only support combustion, but would not support the bypass thrust, nor the process of compression that is vital to turbine engine function.

count to 10 1.2.3.4.5.6.7.8.9.10......
breath out thats better

isnt this about a proposal about the F-14

Originally posted by esecallum
What is your obsession with air??

jets work by combusting fuel with air or the oxygen in the air...
the explosive hot gases jet from the nozzal to give thrust...

The combustor (which is a component within a jet engine) works by combusting fuel with air.

But that is not where the thrust comes from.

Originally posted by esecallum
above 50000 feet no air so you use onboard oxidiser...to replace air or oxygen...

your turbofan is using energy from fuel/air combustion to turn the fans...so its NOT FREE which you seem to think...

Yeap - so the fans are turning, I'm not disputing that - but what is the point in them turning if there is no air to accelerate (in order to produce thrust).

Originally posted by esecallum
jet/rocket/liquid fuel whatever its called all it need to provide net lift at angle of about 45 degrees...

i mentioned te 777 engines which can generate 129000 ibs of thrust
4 engines can lift a 747 vertically

I've shown 4 747 engines will not - but since you mention 777 engines...

The 777-200LR is powered by two 489kN (110,000lb) GE90-110B1s, that gives a total of 1,960 kN, which is still a long way short of the 2,690kN I mentioned earlier for sustained 45 deg flight [and that was neglecting drag!].

Originally posted by esecallum
i have seen hundreds of times 747 taking of from runways at nearly an angle of 45 degrees...and yet you lie saying it cant do that...

Yeap, I can guarantee you it will not approach anything like 45 degrees, it is probably climbing out at an angle around 15 degrees.

Originally posted by esecallum
in your desparate haste you cant even read what written...

Before you start having goes at other members, perhaps you should consider that you are arguing with at least 2 people that work in the industry and maybe, just maybe, we know something you don't.

Also, you should be aware, that I am only choosing to discuss the least complicated of the many gaping holes in your idea - in the hope you'd realise your mistake quickly. I'm not so sure if that is going to be the case now.

Nice to see this dog is still chasing its tail. One more time friend, in a jet engine fuel and oxidizer combust to release stored chemical/potential energy that heats the airflow (not just the fuel and perhaps oxidizer that has just been injected into the combustor) that has passed INTO THE ENGINE and through the core, and then expands that heated airflow through a set of turbines to generate enough power to turn the compressor (increases pressure ratio for higher efficiency) and turn the fan TO PRODUCE THE VAST MAJORITY OF THE ENGINE'S THRUST BY ACCELERATING MASSIVE AMOUNTS OF ATMOSPHERIC AIR. Beat it into your head that massflow MUST be accelerated for 3rd-law thrust to be generated. The acceleration of the combusted fuel and whatever oxidizer you wish to bring with you is not enough thrust. For giggles, why don't you work out the avg #/sec fuel burn on your mythical 10 hour mission, and then multiply that bad-boy by the exit velocity of your engine exhaust and you'll soon realize that even for a choked conic exit nozzle that you won't have anywhere near the thrust you thought you had. Also for grins, why don't you look into the thrust rating system, and work on grasping the concept of a sea-level static (SLS) thrust quote. The 129,000# thrust of the GE90-115B is only made at SLS. IT DOES NOT MAKE THIS AT ALTITUDE. Any dreams you have of supplementing lost wing lift with half a million pounds of engine thrust in an effort to wrench a half million pound aircraft into space are wildly off the mark. I'm sure this effort will prove fruitless, since you've had about 4-5 people trying to educate you on airbreathing propulsion, and multiple others on aerodynamics and structures, but one more stab can't hurt I guess.

Right, now the F-14 idea seems to be an alright one, but the amount of fuel it would need with that rocket underneath it would be a lot I would have thought. Particular problems would be the undercarriage, I don't think it would be high enough, even if the nose wheel could be deployed. It would probably need a detachable extra fuselage for takeoff.

Also to detach that large a weight when traveling supersonic seems a bad idea too, when it would detach the rocket it would have a massive amount of extra lift which would surely give control problems.

On Landing I suppose it could use the normal landing gear.

Originally posted by Nipples
TO PRODUCE THE VAST MAJORITY OF THE ENGINE'S THRUST BY ACCELERATING MASSIVE AMOUNTS OF ATMOSPHERIC AIR..

so by your own admission its impossible for rocket engines to work as they dont have massive amounts of air to accelerate?


your cleary confused..and violating conservation of momentum.... look

M1XV1=M2XV2

we can EITHER send 1 kilogram out of the nozzle at 1000 m/s ORwe can send 10kg at 100 m/s...the thrust is the same...

so your obsession with large amounts of air is invalid.

as the large mass of air coming in is being exited AT A LOWER speed per above equation...

i have kept this post short so that by the time you have read the end hopefully you can still remember the start...

Originally posted by esecallum
we can EITHER send 1 kilogram out of the nozzle at 1000 m/s ORwe can send 10kg at 100 m/s...the thrust is the same...

Which goes right back to my earlier point about the two states of operation being fundamentally different, and impossible to design one engine to work in both ways.


Go and consider what a rocket (which is what you are proposing) and a turbofan (which is what you want to build the rocket into) have in common.

Originally posted by esecallum

Originally posted by Nipples
TO PRODUCE THE VAST MAJORITY OF THE ENGINE'S THRUST BY ACCELERATING MASSIVE AMOUNTS OF ATMOSPHERIC AIR..

so by your own admission its impossible for rocket engines to work as they dont have massive amounts of air to accelerate?


your cleary confused..and violating conservation of momentum.... look

M1XV1=M2XV2

we can EITHER send 1 kilogram out of the nozzle at 1000 m/s ORwe can send 10kg at 100 m/s...the thrust is the same...

so your obsession with large amounts of air is invalid.

as the large mass of air coming in is being exited AT A LOWER speed per above equation...

i have kept this post short so that by the time you have read the end hopefully you can still remember the start...

No, no, no...rocket engines don't need as much "air" as a jet engine. They just need two things:

1. relatively small amounts of oxygen (at least less than a jet engine) to act as the oxidizer, for burning.

2. Plenty, plenty of fuel

And if you want this 747 to get to orbital heights and speeds (even if you use jet engines until 50,000 ft), and then slow down from orbital speeds, you will need more fuel than the plane can probably carry.

And BTW, you still haven't addressed re-entry friction.

Originally posted by Soylent Green Is People

1. relatively small amounts of oxygen (at least less than a jet engine) to act as the oxidizer, for burning.

2. Plenty, plenty of fuel

And if you want this 747 to get to orbital heights and speeds (even if you use jet engines until 50,000 ft), and then slow down from orbital speeds, you will need more fuel than the plane can probably carry.

And BTW, you still haven't addressed re-entry friction.

Re-entry is the reverse of going into orbit using SUSTAINED thrust....

also i am not the only one busy designing 747 spaceplanes..

read this and eat your hat..

uplink.space.com...


full facts and figures with weights...
see??
you are clearly getting old...

with age you stop being bold.


remember you have old pilots and bold pilots
but there are no old bold pilots.


and you are clearly old pilots who never ever became bold....




[edit on 25-1-2007 by esecallum]

[edit on 25-1-2007 by esecallum]

Mod note

It's too interesting a topic to watch dissolve into pettiness so please drop the disparaging remarks.

Originally posted by esecallum
also i am not the only one busy designing 747 spaceplanes..

read this and eat your hat..

uplink.space.com...

And what does that link prove? So some one else on another forum 2 years ago was messing around with a similar idea for fun... and if you read the thread, you'll note that some people were picking apart the idea and finding flaws with it.

When you can find some one/company who is seriously designing an existing commercial aircraft to go into LEO or beyond and work the way you propose, then I'll eat my hat. Until then, I shall remain mildly amused by this silly idea.

Although, according to L. Ron Hubbard. 75 million years ago, Lord Xenu used spaceplanes that looked exactly like Douglas DC-8's (minus the engines), so maybe you're onto something.

Momentum is not thrust. Thrust is a force, which is defined as the time-rate CHANGE of momentum. Therefore if I want to go anywhere I desperately want to increase momentum. I will grant you the benefit of the doubt and go with the assumption that your example's initial state for both masses is zero velocity, and your numbers are their final states. Yes you get the same MOMENTUM (and thrust, assuming zero initial momentum) for 1kg*1000m/s as 10kg*100m/s, but the energy of that flow (and thus the energy spent on getting that momentum delta) goes as the SQUARE of the velocity. Large massflows accelerated to lower velocities give equal thrust as their low-massflow high-velocity inverses for less energy. THIS IS THE FUNDAMENTAL BASIS OF A HIGH BYPASS RATIO TURBOFAN ENGINE.

As best I can tell, you seem to want to simply dump JP and O2 into the combustor , burn them, and then accelerate the combustion products out the nozzle. For the time being I will skip over the extraordinarily non-trivial obstacles of getting the turbines out of the way of the gas path (since they will only serve to extract gasflow energy to spin fan/compressor around in a vacuum), as well as fitting a new nozzle to the engine that can change from a convergent nozzle (for low-exhaust-speed atmospheric flight) to a con-di nozzle (for your high-exhaust-velocity exo-atmospheric flight). All this describes is a mythical jet engine that morphs into a bad rocket engine.

I say bad because the combustor of a jet engine is nowhere near as strong as the combustion chamber of a rocket engine, and cannot create as high a chamber pressure, so it cannot accelerate the flow to high enough exit velocities to make up for the extreme decrease in massflow (since you now have no atmosphere to work with) if you are attempting to sustain thrust. Furthermore, as soon as you 'convert' your make-believe engine from jet to rocket mode you lose the endurance that you are counting on for your slow accent to orbit. Remember also that now that the atmosphere is gone, you must carry ALL your O2 with you. That is A LOT, at a 3.4:1 stoichiometric O2-JP mass ratio. I just don't see how you plan on bringing all that O2 along in addition to what is already an enormous fuel load. And for what? To power non existent engines that have 'sort-of' turned themselves into god-awful rockets?

Your premise is based on getting the fuel-sipping endurance of HBPR turbofans when they will not operate that way, but rather will operate as fuel-gulping rockets (bad ones at that). For all this effort you could just carry a smaller detachable rocket ship on top of the 747.

Originally posted by Nipples
Yes you get the same MOMENTUM (and thrust, assuming zero initial momentum) for 1kg*1000m/s as 10kg*100m/s, but the energy of that flow (and thus the energy spent on getting that momentum delta) goes as the SQUARE of the velocity. Large massflows accelerated to lower velocities give equal thrust as their low-massflow high-velocity inverses for less energy. THIS IS THE FUNDAMENTAL BASIS OF A HIGH BYPASS RATIO TURBOFAN ENGINE.
.

yes you are correct about the energy as above.

but you are forgetting that high exhuast velocities means you have to carry less fuel ...which makes the ship smaller...lighter...which means you need less thrust...

in other words a downward spiral in overall energy requirements...

look at the space shuttle...what a joke...a vast fuel can tied to 2 sticks of dynamite....and it cant even reach proper high orbit...

its huge...its ugly....and very expensive....

a high nozzle exhaust velocity is vital if space travel is to be ever affordable...and the ships to be of a smaller practical size...

and chemical rockets need to be abandoned....they have reached the limits of development...

we need to focus on sustained thrust engines.