Could the Goshawk have been a successful engine?

maxmwill · Aug 13, 2020

I've been researching the Goshawk engine. When I'd first learned of this, and how it was cooled(boiling water), I have been intrigued by this, and each time I try to find out the disposition of this engine, that is, what might have been done to make it a better engine, nothing, just that it was dropped as a failed technology. The question, in my mind, still remains, could the bugs in this engine have been overcome? I realize that instead of a simple radiator, it used a series of pipes and a condenser, which does tend to add extra weight, but it still sits in the back of my mind that with time and money(hey, someone richer than Croceus could have taken an interest in this), so, given it's method of cooling, what was the overall efficiency(as well as anticipated future efficiency) of this engine compared to the Dagger, Sabre, or even the Merlin?

Shortround6 · Aug 13, 2020

In size (displacement) it was a Kestrel. So from a power perspective it was going to make as much power as a Kestrel/Perigrine.
The steam cooling was attractive because of the tremendous amount of heat needed to turn water to steam. They figured the cooling system could actually be smaller and lighter.
However the problem is that the point or position in the engine where the water turns to steam has to be carefully controlled. Steam takes up 1600 times the volume the water did and if you had say 40lbs of water per minute flowing through a certain water passage in the engine and it flashed to steam a bit too early you now had a lot less mass of water flowing through the passage leading to local overheating.
It wasn't really all or nothing but a flow of water mixed with steam bubbles that expanded-contracted-collasped didn't give even predictable cooling. Not to mention what the pressure variations could do to the piping and connections.
The British were not the only people to fool around with steam cooling. Nobody got it into a service aircraft.

Dash119 · Aug 14, 2020

Didn't the HE-100 use this type of system? While not produced in great numbers it might be considered a service aircraft.

pbehn · Aug 14, 2020

I think another issue with evaporative cooling was maintaining pressure exactly. Wiki says this about the Supermarine 224. For a fighter plane having the wings and undercarriage as part of a pressurised cooling system must be a drawback.

The evaporative cooling system used by the Goshawk involved allowing the cooling water to reach a temperature greater than 100 °C without boiling by keeping it under pressure while circulating through the engine: this superheated water was then allowed to boil off by releasing the pressure, the resulting steam then being cooled in a condenser, collected as water and then recirculated through the engine.
The system had been experimentally flown in other aircraft, but these were all biplanes, and the condensers and collector tank for the condensed water were all mounted in the upper wing. In the Type 224 the collector tanks were in the undercarriage fairings, and, as the condensed water was nearly at boiling point, it was liable to turn to steam under any slight change of pressure; this frequently occurred in the water pumps and would cause them to stop working

fastmongrel · Aug 15, 2020

A good example of the size of condenser needed for the Goshawk

The Shorts S18 prototype flying boat. Those huge contraptions ontop of the engines are the condensers much bigger than a Kestrel radiator.

Dash119 · Aug 15, 2020

The HE 100 got around the problem of the large condensers by using surface cooling. The skin on the outer wing panels serves as the bulk of the condenser for the steam.

The advantage to this type of system was to eliminate the drag produced by the radiator or condenser as you can see from the pictures. There was a retractable radiator for use on the ground, and even when retracted it contributed to the condensation of the coolant. In fact a special variant of this type set the absolute world speed record in March of 1939. The downside to this type of surface cooling was vulnerability to enemy gunfire.

Although a handful were built, in the end Germany decided to continue with production of the Bf 109 rather than produce two similar designs. The remaining fighters were used extensively in German propaganda and served as a homespun defensive force at the Heinkel factory. It is thought politics played a role in the decision not to produce this type, with Willy Messerschmitt being favored over Ernst Heinkel by the Nazi Party. However Heinkel did produce the bulk of German bombers during the war, so he couldn't have fallen far out of favor with the Nazis.

Edited from condenser to radiator

Dash119 · Aug 15, 2020

This is a full scale replica at Planes Of Fame Museum in Chino California;

Acheron · Aug 15, 2020

Dash119 said:
The downside to this type of surface cooling was vulnerability to enemy gunfire.

Although a handful were built, in the end Germany decided to continue with production of the Bf 109 rather than produce two similar designs. The remaining fighters were used extensively in German propaganda and served as a homespun defensive force at the Heinkel factory. It is thought politics played a role in the decision not to produce this type, with Willy Messerschmitt being favored over Ernst Heinkel by the Nazi Party. However Heinkel did produce the bulk of German bombers during the war, so he couldn't have fallen far out of favor with the Nazis.

Maybe it was really discounted because of vulnerability issues? I understand that aircraft with radial engines were generally much more robust than those with inline engines because in the later, a hit at the engine was likely to destroy the coolant system, dooming the aircraft. Wouldn't any He100 hit in the wings-cooling lines inevitable become a casualty?

Dash119 · Aug 15, 2020

Acheron said:
Maybe it was really discounted because of vulnerability issues? I understand that aircraft with radial engines were generally much more robust than those with inline engines because in the later, a hit at the engine was likely to destroy the coolant system, dooming the aircraft. Wouldn't any He100 hit in the wings-cooling lines inevitable become a casualty?

It was probably a consequence of both, but there is always politics in these types of decisions, past and present...

A direct hit on the engine would probably bring down either a air cooled or a liquid cooled aircraft. The point of difference with the liquid cooled aircraft is the additional plumbing, and the radiator for the coolant. Any air cooled engine hit in the oil cooling system, which was larger than the comparable liquid cooled engine, would likely also end in premature failure.

Acheron · Aug 16, 2020

Dash119 said:
It was probably a consequence of both, but there is always politics in these types of decisions, past and present...

A direct hit on the engine would probably bring down either a air cooled or a liquid cooled aircraft. The point of difference with the liquid cooled aircraft is the additional plumbing, and the radiator for the coolant. Any air cooled engine hit in the oil cooling system, which was larger than the comparable liquid cooled engine, would likely also end in premature failure.

Doesn't that depend on the kind of hit? Like a 20mm cannon or (several) MG bullets?

And why did the P-47 then have such a reputation for ruggedness?

Mad Dog · Aug 16, 2020

maxmwill said:
I've been researching the Goshawk engine. When I'd first learned of this, and how it was cooled(boiling water), I have been intrigued by this, and each time I try to find out the disposition of this engine, that is, what might have been done to make it a better engine, nothing, just that it was dropped as a failed technology. The question, in my mind, still remains, could the bugs in this engine have been overcome? I realize that instead of a simple radiator, it used a series of pipes and a condenser, which does tend to add extra weight, but it still sits in the back of my mind that with time and money(hey, someone richer than Croceus could have taken an interest in this), so, given it's method of cooling, what was the overall efficiency(as well as anticipated future efficiency) of this engine compared to the Dagger, Sabre, or even the Merlin?

Well, probably, but then you have the impact of war preparation on development. Conventional radiator cooling is developed and understood, and scales predictably with engine size, so it is not expected to present unexpected holdups in the development of larger engines. And you have to remember, the British (and the Germans) were having plenty of other issues developing engines in the 2000hp class they projected as required for future bombers. So, conventional cooling was preferred as a matter of expediency.

fastmongrel · Aug 16, 2020

Acheron said:
And why did the P-47 then have such a reputation for ruggedness?

In the ground attack role in Western Europe when the P47 is compared to the Typhoon the Typhoon was less likely to be damaged and the pilot less likely to be injured.

Dash119 · Aug 16, 2020

Acheron said:
Doesn't that depend on the kind of hit? Like a 20mm cannon or (several) MG bullets?

And why did the P-47 then have such a reputation for ruggedness?

I think where the hit occurs is more important than the type, size or quantity of the ammunition. If the coolant radiator or oil cooler is hit with either a 20mm shell or several MG bullets, the end result is pretty much the same with regards to the engine, although the 20mm would probably cause more damage to the radiator itself. I suspect that a direct hit by 20mm shell to the engine itself is likely to cause catastrophic failure in either case. Although once again that would depend on the location of the strike(s).

Ruggedness is not just a function of the type of cooling system utilized by the engine(s). If that was the case only one type of cooling system would be used on most combat aircraft of the era.

All aircraft design is a series of trade-offs and there are pluses and minuses to both types of cooling systems. One of the reasons the U.S. Navy preferred air cooled engines was that the aircraft carriers could avoid having to carry and store one more flammable liquid(ethylene glycol) on board. Hardly seems like a great justification for not using liquid cooled aircraft engines, but this is the kind of trade-offs one encounters in these decisions.

maxmwill · Aug 20, 2020

Acheron said:
Doesn't that depend on the kind of hit? Like a 20mm cannon or (several) MG bullets?

And why did the P-47 then have such a reputation for ruggedness?

You'll have to get a Ouija board, because you'll have to ask Sasha Kartvelli, who designed the aircraft(based upon the P43, which was based upon the P35) about the ruggedness of the design, and he was one talented Russian.

ThomasP · Aug 21, 2020

I once read a memo/report on the reasons for dropping the evaporative cooling system at the time of the Goshawk. I do not remember if the memo/report was written by Rolls Royce or by Hawker, but it said that the main problem with the Goshawk-evaporative cooling system was keeping it sealed, even in the prototype test aircraft. They likened it to the problems that the steam powered ships had with leaks in their pressurized systems, but worse due to the vibration, shock, and flexing of the airframe. The memo/report did not address the issue of vulnerability.

xylstra · Aug 25, 2020

Shortround6 said:
In size (displacement) it was a Kestrel. So from a power perspective it was going to make as much power as a Kestrel/Perigrine.
The steam cooling was attractive because of the tremendous amount of heat needed to turn water to steam. They figured the cooling system could actually be smaller and lighter.
However the problem is that the point or position in the engine where the water turns to steam has to be carefully controlled. Steam takes up 1600 times the volume the water did and if you had say 40lbs of water per minute flowing through a certain water passage in the engine and it flashed to steam a bit too early you now had a lot less mass of water flowing through the passage leading to local overheating.
It wasn't really all or nothing but a flow of water mixed with steam bubbles that expanded-contracted-collasped didn't give even predictable cooling. Not to mention what the pressure variations could do to the piping and connections.
The British were not the only people to fool around with steam cooling. Nobody got it into a service aircraft.

Other main problem was vulnerability of the condenser to combat damage. May also have had issues with inverted flight.

fastmongrel · Aug 27, 2020

I just thought of another problem with steam cooling. You need absolutely pure distilled water. In a normal engine cooling system you have corrosion inhibitors but with steam it has to be pure water. Any mineral salts will turn into scale as soon as the steam condenses. You don't want the condenser loosing efficiency as it's pipework clogs with scale.

pbehn · Aug 27, 2020

fastmongrel said:
I just thought of another problem with steam cooling. You need absolutely pure distilled water. In a normal engine cooling system you have corrosion inhibitors but with steam it has to be pure water. Any mineral salts will turn into scale as soon as the steam condenses. You don't want the condenser loosing efficiency as it's pipework clogs with scale.

I don't know how it ever got considered for a fighter plane.

rinkol · Aug 27, 2020

Dash119 said:
I think where the hit occurs is more important than the type, size or quantity of the ammunition. If the coolant radiator or oil cooler is hit with either a 20mm shell or several MG bullets, the end result is pretty much the same with regards to the engine, although the 20mm would probably cause more damage to the radiator itself. I suspect that a direct hit by 20mm shell to the engine itself is likely to cause catastrophic failure in either case. Although once again that would depend on the location of the strike(s).

Ruggedness is not just a function of the type of cooling system utilized by the engine(s). If that was the case only one type of cooling system would be used on most combat aircraft of the era.

All aircraft design is a series of trade-offs and there are pluses and minuses to both types of cooling systems. One of the reasons the U.S. Navy preferred air cooled engines was that the aircraft carriers could avoid having to carry and store one more flammable liquid(ethylene glycol) on board. Hardly seems like a great justification for not using liquid cooled aircraft engines, but this is the kind of trade-offs one encounters in these decisions.

Air cooled radial engines had the further advantage that the engine itself was contained in a relatively compact volume and the oil cooler was usually mounted close to the engine. Consequently, there was a lot less in the way of plumbing that could suffer fatal damage from even a small caliber bullet or shrapnel and the engine itself could often take damage without catastrophic failure.. There were some incidents where a radial engine kept running with severe damage to a cylinder.

rinkol · Aug 27, 2020

Dash119 said:
The HE 100 got around the problem of the large condensers by using surface cooling. The skin on the outer wing panels serves as the bulk of the condenser for the steam.

View attachment 591967

The advantage to this type of system was to eliminate the drag produced by the radiator or condenser as you can see from the pictures. There was a retractable radiator for use on the ground, and even when retracted it contributed to the condensation of the coolant. In fact a special variant of this type set the absolute world speed record in March of 1939. The downside to this type of surface cooling was vulnerability to enemy gunfire.

Although a handful were built, in the end Germany decided to continue with production of the Bf 109 rather than produce two similar designs. The remaining fighters were used extensively in German propaganda and served as a homespun defensive force at the Heinkel factory. It is thought politics played a role in the decision not to produce this type, with Willy Messerschmitt being favored over Ernst Heinkel by the Nazi Party. However Heinkel did produce the bulk of German bombers during the war, so he couldn't have fallen far out of favor with the Nazis.

Edited from condenser to radiator

The system used in the He 100 suffered from complexity as it involved a large number of pumps and other components. In the 1930s and 40s, a lot of effort was wasted in various countries trying to come up with schemes to reduce drag:
- surface evaporation cooling
- high temperature cooling (didn't work because the gain in size of the oil cooler offset the smaller coolant radiator)
- buried engines (involved structural complications, drive shafts and loss of space for fuel etc)
- coupled engines (not worth the trouble)
- flat (opposed cylinder) engines

What did work was

Could the Goshawk have been a successful engine?

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