My green lady

a reply to: yuppa

that sounds like a lot of work. what if there was a way to make a normal supersonic turbine out perform a ramjet, and with out the usage of things like boron?

originally posted by: BASSPLYR
a reply to: yuppa

that sounds like a lot of work. what if there was a way to make a normal supersonic turbine out perform a ramjet, and with out the usage of things like boron?

In the 1960's boron based fuels were all the rage for rocket engines. A test of a jet resulted in an embarrassing failure because the engineers did not take boron oxide formation into account. Newer jet fuels were developed that had other important properties, such as heat dissipation, and higher densities. Look up the fuel for the Mig 25 for an example.

I think that the problems with Boron were determined to be not worth the complexity of using carboranes as a fuel.

originally posted by: BASSPLYR
a reply to: yuppa

that sounds like a lot of work. what if there was a way to make a normal supersonic turbine out perform a ramjet, and with out the usage of things like boron?

That be great,but what else burns that shade of green? COuld they use something else but put something of a "octane booster" in th e mix?

Can't remember too much now but during Development of the Typhoon I am sure there was a canister of some fuel additive which was used to relight the turbine after a flam out or stall or whatever, we were doing envelope expansion.

I didn't work on that system so have no idea if it's standard fit or whether it would take much re9-engineering to have a similar fuel injected.

However, I wouldn't think the green stuff would go through the turbines like this fuel, surely someone can correct me but if you were rotating a turbine for Mach 4 or something the RPM would be too high? So it would need a buy pass.

a reply to: pteridine

I think its safe to say that there is SOMETHING emitting a green light that persists for a short time along the flight path of this aircraft.

Another safe assumption is that there is a light on said craft to disrupt night vision equipment and maybe even targeting systems of missiles.

The boron oxides left in the exhaust stream would make a convenient projection platform to send this light threw, as it would leave a streak of light to confuse observers and missiles.

originally posted by: Forensick
However, I wouldn't think the green stuff would go through the turbines like this fuel, surely someone can correct me but if you were rotating a turbine for Mach 4 or something the RPM would be too high? So it would need a buy pass.

You really wouldn't want turbines or compressors at Mach 4. Really we hit that sort of wall with the SR71 where it was at the end of turbojet's usefulness, and the start of a ramjet's operating window. At that point the flow has so much speed that you can do all the compression you need using speed alone, no need for turbine or compressor machinery. But this compression process generates a lot of heat, and engines do better with colder air in, hotter air out. Not so different from a cold-air intake on a car. Then you start getting to where scramjets are what you need because they don't have to slow down the flow to subsonic speeds to work correctly. The more you have to slow down the air for the engine to work, the more heat you put into it and the worse your engine performs. Less slowdown, less heat, better performance.

If you were running a ramjet, keep in mind you would not have sensitive machinery to get sandblasted by additives. The engine would still need to be wearproofed, but you would be facing a task order of magnitudes simpler than armoring up turbomachinery. Part of me wonders if you could take a standard turbojet and use it for the basic stuff, and then for higher speeds just bypass the turbo and use internal geometry to form a sc/ramjet. You would be devoid of a way to light the fuel because you will have isolated the ignition chamber between the compressors and turbines, but perhaps our green firey friend can help with that.

originally posted by: Darkpr0

originally posted by: Forensick
However, I wouldn't think the green stuff would go through the turbines like this fuel, surely someone can correct me but if you were rotating a turbine for Mach 4 or something the RPM would be too high? So it would need a buy pass.

You really wouldn't want turbines or compressors at Mach 4. Really we hit that sort of wall with the SR71 where it was at the end of turbojet's usefulness, and the start of a ramjet's operating window. At that point the flow has so much speed that you can do all the compression you need using speed alone, no need for turbine or compressor machinery. But this compression process generates a lot of heat, and engines do better with colder air in, hotter air out. Not so different from a cold-air intake on a car. Then you start getting to where scramjets are what you need because they don't have to slow down the flow to subsonic speeds to work correctly. The more you have to slow down the air for the engine to work, the more heat you put into it and the worse your engine performs. Less slowdown, less heat, better performance.

Suppose one could increase the speed of sound of the fluid inside a ramjet device?

originally posted by: mbkennel
Suppose one could increase the speed of sound of the fluid inside a ramjet device?

There already exist ways to do this, though not many of them are under our direct control. You can affect the speed of sound in air using factors like humidity, pressure, temperature and whatnot. Humidity is not so large a deal, but pressure and temperature vary greatly across and aircraft, particularly in an engine.

So your dealing with the government here. The engine self destructs at maybe 40 hours of high speed flight but that 40 gets 500 hours normal flight distance. You just put in a new engine after 40 hours of high speed flight. Money is no object.


Just a thought

originally posted by: mikell
So your dealing with the government here. The engine self destructs at maybe 40 hours of high speed flight but that 40 gets 500 hours normal flight distance. You just put in a new engine after 40 hours of high speed flight. Money is no object.


Just a thought

You do got a point. Since its just one aircraft most likely its prolly easier to make engines for it curently and sinc e the budget is black... th e skys th e limit(pun intended)

a reply to: Darkpr0

I like your theory, it would make a lot of sense as it has been hinted that the green lady has a fast mode, and GTFO mode. That could be why its only green during GTFO

Don't you think that the green color can be made by the skin of the craft insteed of the engine ?

My thought was the engine can go thousands of hours at normal flight speed but the green bug juice has a life of say 40 hours. Just thinking. The green might be part of the engine sacrificing itself for speed??

a reply to: Bfirez

If that were the case then why use it over the Continental US or allied countries as seen by many witnesses.

What ever emits the green is used for a large duration of the flight.

a reply to: Sammamishman

old school seeding alkali?

originally posted by: BASSPLYR
a reply to: Sammamishman

old school seeding alkali?

You leaving?

May be the green Lady is born on the dead of the Blackswift demonstrattor cancelled in 2008 ?

a reply to: darksidius

There is a need that persists for On-Demand ISR. So much so that the USG will pay anything to obtain (or keep) that capability. As questionable as it may have been initially Post-1991, with the rise of China over the last two decades, this capability no longer became a fiscal concern. China is allegedly planning to unveil their version of the B-2 along with another platform this year, hopefully that will resonate appropriately with those who need to come to terms with what's going on this century.

Wrong thread

originally posted by: penroc3
The General Electric YJ93turbo jet was to be used in the XB-70 and the F-108. As i'm sure most of you know these aircraft were mach 3+ with JP-6 fuel. If I am remembering correctly they modified and had allot of test hours using HEF(high energy fuels) the JP-6 produced 18000 and the HEF’s made 26000 of thrust.

We also know that the Air Force has a HEF plant that they made there special boron fuels. So they have the ability to make the green burning fuel. The F-24 like vehicle was most likely made or maybe a modified f-23 is using these power plants with JP-6 for normal flight then the HEF for dashing over mach 3.

Thus making our green lady. What do all of you think about my hypothesis?
If you were going to make the Green lady how would you do it?

I believe many of the points being discussed here were covered in the other thread and (apparently) forgotten about. So here are a few points that were made there with some new thoughts:

1. The SR-71 was a Mach 3+ cruise airframe using a quasi-turboramjet with TEB injection as needed to light the engines on the ground, relight the engines if a flameout occurred, and light the AB. It took off under turbojet power ( P&W J58, usually with AB) and often flew without AB for low speed flight (< Mach 1).
2. A true turboramjet has all of the air that enters the turbojet compressor flowing through all the turbomachinery and exhausting into the inlet of the jet pipe. Pratt & Whitney discovered that when they tried that on the J58, the turbomachinery choked up at about Mach 2.5, and the engine wouldn’t go any faster. So they modified The J58 to bleed some of the air at the 4th stage of the compressor and inject that air into the tail pipe, where they could then burn more fuel, and were then able to get the engine to go up to Mach 3+. That’s why I refer to it as a quasi-turboramjet; not all of the air went through the rotating machinery. When the aircraft was cruising along at its top speed, virtually all the net thrust was being generated by the tail pipe acting as a ramjet; the turbomachinery was just going along for the ride.
3. The SR-71 carried less than a quart of TEB. It was used only for starting the engine and AB. It didn’t supply any additional thrust during flight. During cruise, the SR-71 was powered entirely by hydrocarbon fuel (JP-7).
4. For a given aircraft shape flying at supersonic velocities, the drag coefficient actually decreases monotonically after about Mach 1.5. That means that if you took a shape like the SR-71 and pushed it faster than Mach 3, its L/D would actually improve, up to about Mach 6 or so. In order to fly it faster than Mach 3 while keeping the dynamic pressure the same (thereby keeping the L/D relatively constant) you would have to fly it higher (let’s say up to 110,000 ft instead of 80,000 ft). However, to fly at the higher speed and altitude, you would have to come up with a way to get more thrust out of the same sized engines.
5. My back of the envelope calculation suggests that to cruise between Mach 5 and 6 with the slightly improved L/D you would get from cruising at a higher Mach number, you would need to increase the specific thrust from an engine like the J58 by about 50% or so. That’s right in the ballpark of the kind of improvement you get by using Borane fuels.
6. However, in order to produce more thrust in the same sized engine with the same mass airflow, but at higher speeds, you have to not only have fuel with higher energy content, you also have to be able to burn it faster and use more of the available oxygen in the air (i.e., burn at leaner air to fuel ratios). This is why simply trying to pump more hydrocarbon fuel through the engine and trying to keep it lit with exotic technology like laser or electron beams, etc. won’t work.
7. A hypergolic fuel like TEA/TEB solves all three of these problems at once; it has higher energy content, it burns faster (because it’s hypergolic), and it burns at leaner mixture ratios.
8. Because all the thrust at high speed cruise is generated by the tail pipe and not the turbomachinery, there is nothing to be gained by putting the zip fuel through the turbomachinery and a lot to be lost. The main combustion products of zip fuels that complicates life for turbomachinery includes not just Boron Oxide, but also Boron Nitride (from the Nitrogen in the air) and Boron Carbide (from the Carbon in the hydrocarbon fuel). Both of these last two compounds are abrasives that are much harder than metals and will sand blast the hell out of any metallic surface they come in contact with. This means that the Green Lady almost certainly has two separate fuel tanks, one for hydrocarbon fuel only and one for zip fuel—whether that’s pure TEA/TEB, or one of the many HEFs the Air Force experimented with in the 1950s.
9. If the abrasive combustion byproducts are only in the tail pipe (which has no moving parts) the pipe could be lined with any one of several advanced ceramics which were not available when the SR-71 was designed. Ceramic liners like that would resist the abrasive effects of the Nitrides and Carbides and could be easily replaced when needed.
10. This suggests a nominal flight profile where the aircraft would take off and land and cruise to and from its target (at maybe Mach 3 or so) on hydrocarbon fuel only and then burn the zip fuel only when it was over its target at Mach 5 to 6. That would allow it to refuel from any tanker equipped for JP-7 and not require tankers to be modified to carry zip fuel.
11. An aircraft outer mold line (OML) that had a supersonic drag coefficient at least as good as the SR-71 should be able to do this mission. However, the higher speeds of the Green Lady would require an OML appearing quite a bit different from the SR-71 for several reasons. First, all the wings, intakes, and empennage have to fit inside the Mach cone coming off the nose. At Mach 5 to 6, the Mach cone has a half angle of about 10 degrees (compared to about 18 degrees for the SR-71). So the Green Lady is probably about twice as slender as the SR-71. Second, the higher speed would put the Green Lady into a significantly hotter aerodynamic heating environment and the OML would probably have to look different to minimize hot spots. Third, the SR-71 was designed with slide rules and wind tunnels; with modern computational fluid dynamics, it should be possible to design an OML that’s more aerodynamically efficient than the SR-71, perhaps using the body shape for some external air compression and expansion. At those speeds, some waverider features would make sense.

It seems like an aircraft with the characteristics of the Green Lady is perfectly feasible as a straightforward extension of engine and fuel technology that was developed in the 1950s and 1960s, coupled with advances in materials and computer aided design that have come along in the mean time. No unobtainium is required.