Turbojet powered cruise missiles

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Hi Again KoolKitty,

The cowling was designed by the guys on our team and we had it made using metal spinning technique and riveted it together to form the round cowl behind the round front lip. We made a wood mold and the metal spinner spun it on a lathe out of Aluminum. We polished the front lip for a better look, but painted the rest. It faded from heat. Should have used header paint.

The fuel we used was exclusively gasloine. We ran 87 Octane and 100 Octane, both unleaded. After we discovered how to start it (6 months or slightly more), it ran well. We had to use a bypass valve to bypass the fuel regulator for startup since we were using about 90 psig of compressed air to get it going at idle power and that would blow out the rubber diaphragm. We constructed a mold and molded 4 rubber diapragms ... we blew out 2 of them learning to start it.

We were at a standstill when we decided to approach the engine while it was running and try to push the fuel metering level down by hand. The tube got seriously hot and the convective heat was terrific, but we learned how to get the engine to full power by hand. We then made a friction stop controlled by a wing nut and we could get the engine from idle to full pwoer and then tighten down the nut to hold the full power setting, shut off the compressed air. When we did, the fuel metering regulator operated as designed and maintained the fuel pressure at a constant level, resulting in good, solid, full-power runs.

Later, we added an electric solenoid and used a potentiometer to regulate the current through it, and we could operate the fuel metering lever remotely. After than, it got easier each time we ran it until the fuel pump starting flucuating. Now the fuel pump needs a rebuild. When we stopped running it, we were getting erratic runs due to erratic fuel pump operation.

The museum got a lot of noise complaints every time we ran it, so it is sitting right now, waiting for a fuel pump rebuild, but with little official interest in continuing to operate it. Therefore it is somewhat of a display item at this point. We COULD start it, but the fuel pump just isn't quite right and it souldn't be my first inclination to operate with a known fault. We have a dearth of spare parts, so it we break anything, it might be all over ... we DO have ONE spare set of reed petals, but all of us who restored it want the fuel pump rebuilt before we run it again and are not going to fund it any further from our own pockets. We already have several thousand dollars of our own money in it but it belongs to the Museum. We think it would easily pay for itself at shows but I MUST admit, it is LOUD. You can probably hear it for 5 miles or more when it is at full power, and low frequencies carry a LONG way.

The first time we got it to full power we had three fire departments and two Police cars respond to see what was continuously blowing up for so long! After that, we called the tower to let them know if we were going to run it.
 

Greater speed will mean less shells fired on the missile. Faster target is also harder to hit, or to make a near miss that will make the proximity fuse to detonate. Cumulative effect of greater speed should be a greater survivability of missile.
 
From what I read the radar gun laying and proximity fuse took an increasing toll on V1s as they were deployed. From a theoretical point of view, if the guidance is 100% effective and the launch site is known it makes interception with artillery and barrage balloons easier.
 
On V-1 all I can say is that according to the British their speed varied between 300 - 420 mph, avarage speed was 350 mph (480 - 675 km/h, 563 km/h) and flight altitude from tree-tops to 8,000 ft. Source The Blitz Then and Now. IIRC the British thought that the variations were results of indifferent production quality, after all V-1 was a low-price product.
 
pbehn said:
...it makes interception with artillery and barrage balloons easier.
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The V1 had cable-cutters on their wings, so they could evade balloons for the most part, although about 300 V1s were successfully brought down.

A suggestion about the varying speeds reported for the V1: as time wore on, the different manufacturers were making the V1 from various materials, wouldn't this effect airspeed? Some V1s had steel skinned wings, some had plywood and others had aluminium. There was also quality control on the engines themselves...these were manufactured by forced labor, after all.
 
Juha said:
after all V-1 was a low-price product.
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Again, that should be the emphasis of this thread. COST

I did a little research and I welcome anyone to correct my numbers.

Just before WW2 one US dollar equaled 2.49RM

The V-1 according to Wiki cost 5090 RM which equals $2044 US dollars during WW2, roughly $34,700 in todays dollars.

The Jumo 004 cost 10,000RM, roughly $4010 US dollars during WW2, $68,200 in today's dollars.

So here you had a complete weapon system, the V-1 which cost almost half of a turbine engine of the same period.

Do the math.
 
FLYBOYJ said:
Again, that should be the emphasis of this thread. COST

So here you had a complete weapon system, the V-1 which cost almost half of a turbine engine of the same period.

Do the math.
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The man hours for a Jumo 004 and BMW 003 are well known and indeed they are approximately twice that of the V1.

There wasn't likely an exchange market of $US versus RM in 1944 so its hard to tell. One could probably tell from how neutrals such as Spain, Turkey, Portugal valued RM versus $US. I recall figures between 4.2 (when it was set by the German Government in 1936) and 10, suggested late war.

If one assumes a modern low end wage for manufacturing of $40/hour the 800 hour jumo is about $32000 and the V1 about $16000. Which double checks your figures.

I think the costs might have gone down lower still as automation came in: presses, jigs, large assemblies made in one operation.

From Elegance in Flight:


I'd be surprised if there were that many man hours in engines such as the Merlin or DB605 but one would have to only take the costs of the most advanced piston engines.
 
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My source for the exchange rate, 1938

Historical US Dollars to German Marks currency conversion

My point is you have one V-1 complete for at least half the cost of just one turbo jet engine.

Now having built both aircraft engines and airframes, there's only so much you're going to automate or reduce manufacturing steps, especially looking at 1940s technology. BTW, the 5090 RM cost of the V-1 was from wiki as the indicated cost of the Jumo; I'm assuming those are out the door figures
 
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It helps when you have access to slave labour, I believe the V weapons cost as many lives on the German side as they did on the allied side.
 
I was speculating on using a more powerful engine ... a throw-away turbojet specifically, possibly in the 1,000-1,100 lbf class like the 1938/39 HeS 3. (the idea being something considerably cheaper than the 004B, available much earlier, while being more powerful than the As 014, vibration-free, and much more fuel efficient)

Granted, you could still argue for speed (or speed+range+altitude+much earlier service date) over any increase in guidance system complexity or payload. The overall cost would still be less than double that of the existing V1, so the question is whether it would be at least twice as effective ... or worth the earlier service entry. (lack of vibration issues would speed up development of the existing system dramatically if nothing else)

Beyond that, I'm less sure whether cruise missiles would be more economical than jet powered bombers using longer-life versions of similar engines. (particularly early/mid war when there was less of a pilot shortage)






I think I recall seeing a video from one of the early start-up attempts and the fire department showing up to check on things, though this may have been some other folks.
Ah, nope, it was another group with that appears to be an original As 014 and custom rebuilt valve grid by the sound of the conversation around half way in. They also mention using 50/50 gasoline and diesel fuel (seems like that'd be harder to start on) and a supercharger to supply the compressed air.

youtube.com/watch?v=jTsQxwWcqJI


With the Chino jet, I wonder if you guys could set up some kind of muffler to dampen the sound on test runs. Maybe rig up a 55 gallon drum with the bottom cut out and a bunch of holes or slots punched in it placed at or near the exhaust outlet. (without the perforations, the drum might still muffle things somewhat, but also end up acting as a crude thrust augmentor, which would wouldn't be the intended purpose and could have ... interesting results depending how the drum/muffler rig was mounted)
 
Pulse combustion does away with those problems with heating ... at least once they've warmed up to minimum operating temperature (or use a fuel that lowers the min operating temp) and would almost certainly produce more static thrust at far better specific fuel consumption than a ram jet using the venturi effect for continuous static combustion. (I'd imagine the latter would be closer to the limited thrust resulting from a blow lamp or blow torch -though having ANY sort of stable flame /and/ thrust at static speeds is significant for a ram jet)

That said, that idea of using a pressurized heated fuel jet inside a RAM jet is very much relevant in the idea of placing an entire pulse jet inside a RAM duct sleeve (effectively acting as the combustion chamber embedded inside a ram jet). Be it a valved or valveless design, a cowl/duct with a ram inlet adding significant compression at high speeds would force the pulsing combustion into continuous flow combustion (due to pressure forcing the shutters to remain open in the valved examples -the valve grid acting as flam holders for the combustion chamber).

On the note of ram jets, those would also avoid the issues related to vibrations and have better altitude performance compared to pulse jets, but they'd need to be able to reach a critical airspeed/thrust threshold with catapult/rocket assist. (or air-launched in an accelerating dive, or some combination of those)


Propane needs fairly heavy pressure tanks to be liquified and is a fair bit less dense than gasoline even as a liquid (though better volumetric energy density than methanol by a good margin). Butane or a propane-butane blend, or some economical cocktail of LPGs with relatively low liquification pressures would make sense, though. (same would apply to a turbojet using a pressure feed)

For that matter, you could potentially use fuel bleed to power the pneumatic instruments rather than compressed nitrogen, possibly vented into an intermediate medium pressure gaseous expansion tube/chamber/regulator fed into the fuel jets rather than just vented. (though the temperature drop from liquid to gas phase shift might make the LPG gas too cold to properly operate some of the instruments, or lead to icing, and while I've seen regenerative cooling used for butane vaporization on model pulse jets, and that too would be useful here -for combustion needs- having fuel piped to the hot section and then BACK to the instrumentation seems inefficient/needlessly complex when the solution is to use an independent local nitrogen chamber)


Koopernic said:
The man hours for a Jumo 004 and BMW 003 are well known and indeed they are approximately twice that of the V1.
Click to expand...
I've seen some figures (or at least claims) putting the 004B at 375 man hours to the 003's 600, but I'm not sure how accurate those are or what the context was. (differing production lines, volumes, workforce, among other factors)

Something like the HeS 3 should take considerably less time/cost though, particularly if further developed/modified specifically as a cheap/short life engine.

But aside from that the bigger point wouldn't be whether an alternate cruise missile was more or less expensive to build than the V1, but the relative effectiveness ... the bang for buck. That and whether a (basic) turbojet design could have reached service earlier.

On that note, using LPG fuel would actually ease/solve some of the problems with the HeS 3 design, including the reliance on starting on hydrogen for a warm-up period until the kerosene vaporizer tubing reached operational temperatures. (plus pressurized gaseous fuel avoids the complexity of a fuel pump and use on a disposible missile avoids the concerns with vulnerable pressure tanks compromising a piloted combat aircraft)
Due to the ease of synthesizing it from methanol and smokeless flame even during incomplete combustion, dimethyl ether might be an attractive fuel to target in particular.

According to:
F3 Centre
Dimethyl ether has 70% of the energy content per volume (as a liquid) of conventional diesel fuel, or roughly 80% that of gasoline by volume, compared to 74% for propane based on: Gasoline gallon equivalent - Wikipedia, the free encyclopedia

DME would have similar advantages for use on pulse jets with lack of smoke/soot and ease of start-up. (advantages for use in ram jets too)



Ignoring the V1 production cost and target hitting precision, the ability to fly faster AND at higher altitudes than the existing V1 would have been very significant for AA evasion. The low altitude flights of the existing V1s meant great vulnerability to light and medium as well as heavy AA (where proximity fuzed shells would come into play). An increase in speed AND altitude would dramatically improve AA resistance though, and in the case of a turbojet, the exhaust jet would be invisible (or nearly so) and noise levels drastically lower. (not that that would matter for radar sighting)

Come to think of it, though, I wonder if some V1s were picked up on the old acoustic mirror system before they showed up on RADAR, particularly any that flew very close to wave/treetop level, flying under the radar.
 
I disagree that flying higher would make the V1s less resistant to AA.
The heavy AA was radar guided, and equipped with proximity fuses.
A radar directed gun has no more problem determining lead for a 550mph target than it does for a 350mph target, and by flying at higher altitude, you give each individual gun more time to shoot at you horizon to horizon, though increaseing the speed would decrease that time of course. But increasing speed while increasing altitude at the same time might end up not decreasing time exposed to each AA weapon site.

If they wanted to make it impossible to shoot down , they should have made it fly faster and lower. Too fast for the fighters to intercept, and by the AA gun crews before they could alert them, or even traverse a gun if they were alert.
That's the way modern cruise missiles do it, fast and very low.
 
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The man hour numbers are just that. You could factor that at a normal labor rate of consider the free "slave labor" that was available. You have to consider the cost of material, but regardless the sources at Wiki are showing that a complete V-1 airframe is nearly half the cost of a Jumo engine alone. Throw in the rudimentary guidance systems of the day and I see no way you could get "more bang for the buck" with what was available at the time. The V-1 was cost effective and IMO if introduced earlier in the war "would have" been more of a game changer than an earlier deployment of the Me 262.

Exactly!!!
 
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The claim is that at their peak effectiveness SCR-584 radar directed guns firing radio proximity fused shells got down to 40 rounds per V1 destroyed.

V1's which increased speed from 600kmh to 650kmh do seem to have reached the front. Those that achieved 760km/h due to engine improvements and 815kmh due to a combination of improvements didn't. After testing something in a R+D section one has to check and issue production drawings, set up production, introduce new user instructions.

I've tried to do a calculation on decreased vulnerabillity. A V1 at 375mph would be moving at 170m/s, at 440mph at 200m/s and 515mph at 235m/s.
It would cover 1.6km or 1 mile in 9.5 sec, 8 sec and 6.5 seconds respectively.

Assuming shooting begins at 3.25 miles range (5.5km) and ceases at 0.25 (400m) there will be 28.5 seconds, 24.0 seconds or 19.5 seconds to shoot during which a battery of 6 (I'm assuming the US 90mm M3 and UK 34 pounder were in 6's) could fire a round every 2 seconds per gun (very generous, assuming VT fuzes and auto loader) hence there would be 14.25 rounds, 12 rounds and 9.75 rounds fired from 1 gun at a lone V1.

To summarise, if firing commences at 3.25miles and ceases at 0.25miles then for a single gun:
1 605kmh/375mph,170m/sec means 14.25 rounds can be fired over 28.5 seconds, increasing to 84 rounds if a battery of 6 AAA is available.
2 715kmh/440mph,200m/sec means 12.0 rounds can be fired over 24 seconds, increasing to 72 rounds if a battery of 6 AAA is available.
3 830kmh/515mph,235m/sec means 9.75 rounds can be fired over 19.5 seconds, increasing to 58 rounds if a battery of 6 AAA is available.


For a centrally directed battery of 6 guns there would be 84, 72, 58 rounds which generally is just enough to deal with a V1. I would assume that 40mm bofors would be placed in between, generally the most effective AAA gun of WW2. The 20mm gun would tend to be too short ranged, while the heavy guns cannot traverse fast enough to follow the V2 when it is directly overhead.

V1's were initially intended to cruise at 9000ft however a nagging problem with the autopilots barometric capsule forced them down to 3000ft. V1's may have changed tactics to higher altitude or more extreme low altitude.

However if two V1's can be launched simultaneously so that they cross the same area of coastline at the same time the second one may not even be engaged. Just as a lone B-17 or Lancaster can not survive over the Reich a lone V1 is also more vulnerable.

1 The higher the speed the less rounds can be fired and the less subsequent targets engaged for a firing cycle. 2 Any measurement error in the radar, FLAK predictor, gun laying, gun and optics alignment and barrel is amplified by the greater speed of the missile. These two effects would compound. For instance miscalculate the speed of a 650kmh V1 by 5% 2 seconds ballistic flight time away and you might miss by 17m, If it is a 815kmh missile you miss by 22.5m.

Other factors would be the time interval between completion of a engagement of a target and the time to re-engage a second one.

Of course if the V2 was being engaged by a highly effective modern system, such as Phalanx or a modern naval gun, the calculation would be moot. It would be gone if not in the first round then as soon as the radar had measured the miss of the first of the previous rounds and corrected.

Given the state of the art and the supposed requirements of around 40 rounds I'm hazarding to say that a 20% increase in speed would lead to at least a reduction of V1 kills from 0.8 x 0.8 = 64% reduction in effectiveness of the system. I think it would be worse in fact.

The cost of the 40 proximity fused rounds in money and material terms would be quite hefty.

Of course this is non linear. If the Germans can either saturate British AAA defences in a small area (which is what bomber command did to German defences) or disperse their attack so that coastal areas not covered by FLAK batteries are overflown the situation changes.

The German aviation industry had approximately 2 million involved in WW2, assuming this is really 1 million and that they dedicate 5% of it to V1 production they have 50,000 people would could in theory produce 5000 V1s per week (20,000 per month) if each cost 400 man hours which would be 666 per day. V2 production was to reach 1000 and then step up to 4000-5000 month.

Some on the German side were considering not 1000 or 5000 month but 100,0000.

Even assuming that only 20% of V1's reach metropolitan towns, mainly London this suggests that of 20,000 V1 launches per month 4000 might hit part of a city: it could be a house, a factory, a barracks, a church, a street car, a busy road, a school with or without children, a farmers field, a block of apartments, an airfield. Exactly the same as Area Bombardment did though without the possibility of a firestorm. Somewhat mercifully engine noise and then the cut out of the engine gave a good warning.

It doesn't matter that if of the 20000 launches only 20% hit a structure, only that 4000 did and that the cost was affordable. Four engine bombers had similarly discouraging results.

It's said that a V1, if it hit a farmers potato field, was so cost effective the value of the potatoes to the British economy exceeded that of the V1.

The successful allied invasion restricted V1 launch sites allowed allied defences to be concentrated. The difficulties the Germans had due to the invasion reduced the German launch rate and thus prevented the possibility of saturation of Allied defences.

"If" 100 V1 launch sites (I believe 76 were operational) could launch 7 missiles in 7 minutes then 700 V1's could be crossing the UK coast within 10-17 minutes of launch. Catapults were nowhere near capable of that.
 
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No doubt 2 V1 could be launched at the same time, but with their big quality control problems, would those same two V1 assume accurate enough flight paths to go over the same piece of real estate at the same time 75-100 miles away ?
 
The V1 used a barometric altimeter, how low could one make such a device work reliably? Maybe 100ft?


If one wanted to go lower then the FuG 101a FM radar altimeter will go down to about 2m. They were used as part of blind landing systems and to help German bombers penetrate at night.

tyrodtom said:
No doubt 2 V1 could be launched at the same time, but with their big quality control problems, would those same two V1 assume accurate enough flight paths to go over the same piece of real estate at the same time 75-100 miles away ?
Click to expand...

I would think one would have to just rely on launching many V1 from as many locations as rapidly as possible. The limitations of the AAA belts would be not number of guns but the number of SCR-584 radars and M9 directors. (which had analogue outputs for the US 90mm and selsyns form the British guns) As the allies broke out from Normandy (Operation Cobra) the Germans lost their launch locations and the ones they had gave very limited flight optons that allowed AAA defences to be built.

The EWALD 2 guided versions were intended to lead up to 4 closely trailing versions of the V1. I believe they were to use "blitzubertragung": basically "flash transmission" like in an xenon electronic camera flash to home on to, according to Fritz Trenkle's book on German WW2 missile guidance. (German Only). It may have been code named Moselle (after the river)
 
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The manual states an accuracy of +/- 10% and states that 0 and 3 meter height are clearly distinguishable.

In practice the system worked pretty well over solid ground and water. When flying over woods, the signal would show variations.

The question is could the FuG react quick enough at low altitude to a sudden increase in elevation over tree covered terrain?
 
Koopernic said:
If one wanted to go lower then the FuG 101a FM radar altimeter will go down to about 2m. They were used as part of blind landing systems and to help German bombers penetrate at night.
Click to expand...

And add even more expensive equipment, and impose another demand on limited resources for a throwaway weapon? What could the justification be for this?

The FuG 101 also required a relatively bulky power supply to go with the receiver and transmitter units. The two antennae would be the least of the problems, though there were limits (which I can't remember) to their separation.
The system also had two altitude ranges, basically depending in which direction the motor responsible for the frequency modulation was running. In an aircraft the range (0-150 or 0-750 ) metres could be selected by a human. The speed of that motor also had to be tuned manually as it could vary with the voltage from the on board PSU. It was typically calibrated to 60m. None of this would be possible in an unmanned aircraft like an upgraded V-1.

Cheers

Steve
 
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I keep seeing these figures and am wondering where they come from...

The V1, as powered by the As014 had a launch speed (catapulted) of roughly 580kph that settled into a cruise speed of 640kph at it's typical altitude. Of course, air-launched speeds would be lower but it accelerated to it cruise speed within several minutes. Even the Fi103R (same As014 engine) had the same performances. It might be noted, that the V1 would achieve 800kph in it's dive.

The JB-2, powered by the PJ31 engine slightly improved the cruise speed to 684kph. Then there was the JB-4, with the same PJ31 however, it's cruise speed was improved to 716kph. And post-war, the Junkers EF126, powered by the As044 managed to reach 780kph max.

Although a few Fi103Rs were found to have the As044 fitted, there is no record of a V1 being fitted with any so far as I have seen.
 
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