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King Haalahd VII's design

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Re: King Haalahd VII's design
Post by PeterZ   » Fri Feb 02, 2018 5:33 pm

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WeberFan wrote:BIG HUGE SNIP... (Emphasis mine)
PeterZ wrote:That is unless it is possible to make jets/turbo props without electricity. Re-starting en engine in flight may not be possible, but can it even get started with assistance groundside? Can an ignition system be created witout electricity? Will using chemical agents work as igniters? I have no clue what is possible in that direction.


Yep...It's possible.

Speaking as an aerospace engineer now...

A lot of what goes on in turbojet engines is mechanically driven once the motor is started. So, when you're getting ready to start it on the ground, you need a way to rotate the engine, which will then drive all the accessories (like the hydraulic pumps and - the one I was really thinking of - the fuel pump). The fuel pump delivers high-pressure fuel to the burner cans. The fuel injectors vaporize the fuel and allow it to mix with the combustion air being drawn through the engine intake and compressed. So now you have a highly-combustible fuel-air mixture in the burner cans.

The final step is ignition. While an electrical / spark ignitor is the most common, you could also use a "shotgun shell" ignitor (common with earlier piston engines and diesels). Once it's going, it'll keep going so long as you have a continuous supply of air and fuel.

As to restarting a motor in the air (and assuming you've "got some sky underneath you"), you can nose over to get enough airspeed so you have ram air up the intake to spin the motor (and thus drive all the accessories like the fule pump). Another shotgun shell ignitor and voila.


So jets don't need an ignitor after the initial ignition? I thought that might be the case, but wasn't sure.
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Re: King Haalahd VII's design
Post by WeberFan   » Sat Feb 03, 2018 7:04 am

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Hey PeterZ...

To respond to your question - once it's running, it'll keep running... UNLESS you get some lose air or fuel. BUT... If you get some unstable airflow down the intake, it could "blow out the fire."

With an early generation jet traveling at relatively slow speeds (i.e., not even close to supersonic), I don't think that would be an issue. Another potential cause of unstable airflow would be if the aircraft were operating at high angle of attack with high engine speed. This would put the engine in a situation like cavitating a pump where it's turning at high speed but there's just not enough air present for the engine to pull down the intake.

As to the first case (high speeds), I recall reading something about the SR-71 - the aircraft flew so fast that there would be compression (shock) waves tailing from the edges of the intakes down into the engine. When these shock waves impinged into the compressor section they would cause what the pilot called an "unstart" in the engine - basically a hiccup that would stall the engine. Don't know if this story was really true or not, but it sounds reasonable. Weird (and in some ways really, really cool) things happen in shock waves and there's been a lot of research done to fully understand what's going on.
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Re: King Haalahd VII's design
Post by PeterZ   » Sat Feb 03, 2018 2:05 pm

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Thanks, Weber Fan.. It seems jets are less likely to transgress the Proscriptions than gasoline IC engines. That is consistent with current development of steam turbines and reliance on pneumatics. Heck, the Royal College has a specialization in pressures. All told, jets appear to be the preferred engine for heavier than air flight. Diesel and steam will likely be the preferred IC engine for almost every other use.

I wonder what this might mean for aircraft carriers. Will we see helicopters? Will we see steam tanks or diesel? Will we see various types of propulsion in naval ships? I can't wait to read about all of this.
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Re: King Haalahd VII's design
Post by WeberFan   » Sun Feb 04, 2018 10:45 am

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PeterZ wrote:Thanks, Weber Fan.. It seems jets are less likely to transgress the Proscriptions than gasoline IC engines. That is consistent with current development of steam turbines and reliance on pneumatics. Heck, the Royal College has a specialization in pressures. All told, jets appear to be the preferred engine for heavier than air flight. Diesel and steam will likely be the preferred IC engine for almost every other use.

I wonder what this might mean for aircraft carriers. Will we see helicopters? Will we see steam tanks or diesel? Will we see various types of propulsion in naval ships? I can't wait to read about all of this.

I wouldn't necessarily jets are the immediate future, PeterZ. IMHO, diesel-powered props would be a good - a very good - intermediate step. Props work very well at relatively low RPMs while jets require (literally) thousands of RPM to work well.

My background included flying single and multi-engine turbojets. Normal idle was on the order of 6000 RPM and 100% power was a bit over 12,000. Interesting things happen from a metallurgical thing when you heat metals up to combustion temperatures and rotate them at those speeds. Blade creep being one of them.

OTOH, a diesel driving a prop through an appropriate set of gearing is just so much more simple - and reliable. For the prop, I'd go with (probably) a prop with 4, controllable pitch paddle blades. I think a diesel would drive that prop just fine.

If I were going to implement heavier-than-air aircraft, I'd go (initially) with a straight-wing/high-wing design with a relatively thick/high aspect ratio wing (lots of lift and also gives you lots of space for fuel in the wings). Perhaps not the most maneuverable thing in the world, but quite adequate. My initial design would have manual (cable and linkage) control systems which are quite workable at relatively low speeds when you trim them up. Probably a single engine at first (a bit underpowered, but workable). I'd use the single-engine only for overland flights or those with short periods overwater. When the engine technology evolves a bit, you could then go to a multi-engine design for longer, overwater flights. One thing I would NOT do - even at the outset - is to design a tail-dragger. I'd go with a tricycle landing gear from the outset with a manual crank to get the gear up (to reduce weight and, with the gear up to reduce drag). Yep... I can picture the 220 knot (single engine) up to perhaps 300 knot (twin engine) aircraft in my head as I write this...
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Re: King Haalahd VII's design
Post by PeterZ   » Mon Feb 05, 2018 7:59 am

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WeberFan wrote:
PeterZ wrote:Thanks, Weber Fan.. It seems jets are less likely to transgress the Proscriptions than gasoline IC engines. That is consistent with current development of steam turbines and reliance on pneumatics. Heck, the Royal College has a specialization in pressures. All told, jets appear to be the preferred engine for heavier than air flight. Diesel and steam will likely be the preferred IC engine for almost every other use.

I wonder what this might mean for aircraft carriers. Will we see helicopters? Will we see steam tanks or diesel? Will we see various types of propulsion in naval ships? I can't wait to read about all of this.

I wouldn't necessarily jets are the immediate future, PeterZ. IMHO, diesel-powered props would be a good - a very good - intermediate step. Props work very well at relatively low RPMs while jets require (literally) thousands of RPM to work well.

My background included flying single and multi-engine turbojets. Normal idle was on the order of 6000 RPM and 100% power was a bit over 12,000. Interesting things happen from a metallurgical thing when you heat metals up to combustion temperatures and rotate them at those speeds. Blade creep being one of them.

OTOH, a diesel driving a prop through an appropriate set of gearing is just so much more simple - and reliable. For the prop, I'd go with (probably) a prop with 4, controllable pitch paddle blades. I think a diesel would drive that prop just fine.

If I were going to implement heavier-than-air aircraft, I'd go (initially) with a straight-wing/high-wing design with a relatively thick/high aspect ratio wing (lots of lift and also gives you lots of space for fuel in the wings). Perhaps not the most maneuverable thing in the world, but quite adequate. My initial design would have manual (cable and linkage) control systems which are quite workable at relatively low speeds when you trim them up. Probably a single engine at first (a bit underpowered, but workable). I'd use the single-engine only for overland flights or those with short periods overwater. When the engine technology evolves a bit, you could then go to a multi-engine design for longer, overwater flights. One thing I would NOT do - even at the outset - is to design a tail-dragger. I'd go with a tricycle landing gear from the outset with a manual crank to get the gear up (to reduce weight and, with the gear up to reduce drag). Yep... I can picture the 220 knot (single engine) up to perhaps 300 knot (twin engine) aircraft in my head as I write this...

Yeah, I bow to your experience. My thoughts were jets would be in a prototype phase by the next story arc. Diesel engines having been well developed. I doubt we'll see much use of jets in the next story arc, though.
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Re: King Haalahd VII's design
Post by Silverwall   » Mon Feb 05, 2018 4:08 pm

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The problem with jets is the metalurgy. Not having the right trace additives (Chromium etc) in the steel makes them very sensitive to disortion and weak in high temps.

The Engines in the ME 262 had to be rebuilt every 10 hours because of this as Germany could not make the right steel alloys for the compressor blades.

This will be exacerbated on safehold as with no electricity it will be VERY hard to A: get the trace minerals. B: control the temperature and casting process.
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Re: King Haalahd VII's design
Post by PeterZ   » Mon Feb 05, 2018 4:16 pm

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Silverwall wrote:The problem with jets is the metalurgy. Not having the right trace additives (Chromium etc) in the steel makes them very sensitive to disortion and weak in high temps.

The Engines in the ME 262 had to be rebuilt every 10 hours because of this as Germany could not make the right steel alloys for the compressor blades.

This will be exacerbated on safehold as with no electricity it will be VERY hard to A: get the trace minerals. B: control the temperature and casting process.


Text has Safehold's metalurgy well in advance of the steam age. One suspects that adding the proper mix of trace elements to iron is within reach of current Safehold tech. 20 years of experimentation should provide solid results.
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Re: King Haalahd VII's design
Post by Silverwall   » Tue Feb 06, 2018 7:57 pm

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Yes thier metalurgy is better than histoically but that doesn't solve the Chromium problem. Sadly chromomium production chemistry relies on electric arc furnaces and aluminimium reduction processes (Aluminium production also requires electricity) Other Rare metals also need Electricity as part of the refining process.

On a side note 80-90% of earths chromium is produced in India, Khazakstan and South Africa, so it's quite possible that The Charisians have no easily exploitable deposits (subject to author fiat)which could make a good pretext for war.
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Re: King Haalahd VII's design
Post by Castenea   » Wed Feb 07, 2018 7:52 pm

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Silverwall wrote:Yes thier metalurgy is better than histoically but that doesn't solve the Chromium problem. Sadly chromomium production chemistry relies on electric arc furnaces and aluminimium reduction processes (Aluminium production also requires electricity) Other Rare metals also need Electricity as part of the refining process.

On a side note 80-90% of earths chromium is produced in India, Khazakstan and South Africa, so it's quite possible that The Charisians have no easily exploitable deposits (subject to author fiat)which could make a good pretext for war.

You are both correct and incorrect. Economical bulk production of Aluminum, Chromium, Tungsten and many other metals rely on electricity. There are chemical processes for refining these metals, but for various reasons (cost of reagents, safely handling reagents, et al) these were barely developed past the lab bench stage.
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Re: King Haalahd VII's design
Post by Theemile   » Fri Feb 09, 2018 5:19 pm

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PeterZ wrote:
Silverwall wrote:The problem with jets is the metalurgy. Not having the right trace additives (Chromium etc) in the steel makes them very sensitive to disortion and weak in high temps.

The Engines in the ME 262 had to be rebuilt every 10 hours because of this as Germany could not make the right steel alloys for the compressor blades.

This will be exacerbated on safehold as with no electricity it will be VERY hard to A: get the trace minerals. B: control the temperature and casting process.


Text has Safehold's metalurgy well in advance of the steam age. One suspects that adding the proper mix of trace elements to iron is within reach of current Safehold tech. 20 years of experimentation should provide solid results.


When the US was given the design of the British jet engine, GE couldn't figure out how to get power out of the engine AND longevity - they ended up getting a 1st generation engine with ~70% the output of the same design the British were reporting and a average lifetime of 60-80 hours. Running at the British reported output gave the plane 5-20 hours of use.

What the Brits didn't tell the Americans was the turbine blades required a new type of Nimonic alloys. While the original British engines used Nimonic 75 or 80a, Nimonic 90, deployed in 1945 had the following composition:

Nimonic 90:
Ni 54% min
Cr 18–21%
Co 15–21%
Ti 2–3%
Al 1–2%

This was cutting edge mettleurgy in 1945, which no one else had. The Russians got it by purchasing 55 Rolls Royce Neva engines via a goodwill agreement, which came with the blueprints (the Russians asked, and the factory rep, trying to curry goodwill with the liberal brit govt, gave them to them), including details of the Nimonic alloys, which took them years to figure out properly.
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RFC said "refitting a Beowulfan SD to Manticoran standards would be just as difficult as refitting a standard SLN SD to those standards. In other words, it would be cheaper and faster to build new ships."
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