Turbojet powered cruise missiles

[Koopernic]

I don't get the claim that high precision wasn't a possibility. The electronics of the day could be extraordinarily accurate.

The Blind bombing systems merely need to be applied to the autopilot directly. It was only a matter of time.

For instance a Seetakt radar (land based version) could measure the range of a target out to 60km with only a 10m error. There was no 'percentage error' this was an absolute error. The reason was that the pulse was also sent down a series of switched delay lines which were precisely calibrated and then compared to the return pulse with a sort of Geneva mechanism or resolver. If you used two radars you could triangulate a target to within 10m. This is GPS scale accuracy.

This is what Oboe did. There are broadly two types of radar, primary which relies of a reflected wave of the target and secondary which relies on a transponder which upon receiving a radar pulse retransmits it on a different frequency, thus achieving greater range. A little bit of data can be appended such as IFF (Identification Friend or Foe) or some height information.

Oboes accuracy was sometimes exaggerated but if operating say 50km from the transmitter it was extremely accurate. This is often quoted as 17 yards. This is not the accuracy but the resolution that was used to inform the pilot if he was of path (by a Morse signal) Naturally at 100s of km of range the bomb would be released at maybe 10000m and subject to the effects of wind as it fell. There would be a little distortion due to the atmosphere, which was actually taken into account.

Bind bombing systems + auto pilot = an extremely accurate guided missile.

The USN did fly TV guided drones in the dying days of the pacific.

The Germans did fly TV guided versions of the Hs 293 (the so called Hs 293D) which had TV guidance in the nose. The TV transmitter was called Tonne Seedorf. it worked fine in the summer or good light conditions and Ive seen photographs of its black and white screen being test flown. Its not inconceivable that a jet powered V1 could carry an rotating directional antenna that could relay TV signals to a control aircraft.

The Germans had two radiation homing warheads Radischein and MAX-P as well as some work on infrared homming (seen as usefull against blast furnaces.

 

[stona]

If it was possible then it must have been deemed either impractical, for whatever reason, or undesirable by the Germans. Is there another explanation as to why neither they, nor anyone else, deployed such a system at the time or even medium future?

Cheers

Steve

 

[GrauGeist]

The TDR-1 used in the Pacific during WWII required a TBM-1C to guide it. Out of the 195 TDR aircraft built, only 50 were deployed and out of that 50, only 31 missions were successful.

Looking at the TDR project's development, you'll find that the guidance system was problematic and held up the project. While they had been working on the project for a while, it wasn't until 1942 that a first test flight was conducted, yet it was two more years before the system performed well enough that the TDR was able to go into combat.

So again, it was the developing technology that was holding the concept back: both the Radar Altimeter and the Television Guidance System.

Otherwise, it was a sound idea and capable of delivering a bombload of up to 2,000 pounds (910 kg). However, if the TDR were used by the Germans against Britain, it would have never stood a chance, as it's average speed was 140 mph (225 kph) and would be easily intercepted or downed by AA.

 

[Koopernic]

The systems that would get a V1 or V2 accurate to say within 1km were testing and had been testing since 1943. The guidance beams had a problem with ground plane interference and the missile needed to damp out sideways velocities, it being no good placing a V2 to within 10m of a guidance beam if upon motor cut off it had a residual sideways velocity. Because development had been started fairly early the two problems had been identified and it seems solved: one by using microwaves and the other by electronic differentiation and correct 'damping equations'

The winged A4b did undertake two flights of which one displayed a successful re-entry before telemetry from the Minerva system indicated that the wings broke of at the root due aero thermal heating that was harsher than expected. The giant guidance system to control it to within just over 100m was also under development. It was called 'Wasserspiegel" or water mirror. It was made up of a existing radar systems rather than any new development.

It would be only a matter of time after the TV guidance systems developed for the Hs 293 anti shipping missile were tried on something like the V1. The Iconoscopes of the day had quite a problem in dim conditions but the war seems to have progressed them.

I suggest that the reason these systems didn't see service sooner was a primarily a conceptual one. Humans were thinking inside the box. The other was that the technology, such as radar, had only just become available in the mid 30s.

For instance the Miles Hoop-La, Britain's own fly back cruise missile, was rejected because it wasn't accurate enough to avoid killing women and children and so was 'beneath contempt'. That's actually the wording in the official document. The V1 is a latter aircraft than the Hoop-La, by then the gloves were off.

Ju 88 pilots on torpedo runs had a habit of entering the aircraft into a descent held by the quite good 3 dimensional autopilots the Luftwaffe had. They noted how accurate the aircraft was. This lead to the idea of using unnamed aircraft as giant missiles with oversized hollow charge warheads. (they were quite capable of smashing through a dam wall). The autopilot could be controlled via the kehl strassberg system used in the Hs 293 and Fritz-X though it was likely never used as the autopilot was quite accurate.

 

[stona]

Ju 88 pilots on torpedo runs had a habit of entering the aircraft into a descent held by the quite good 3 dimensional autopilots the Luftwaffe had. They noted how accurate the aircraft was. This lead to the idea of using unnamed aircraft as giant missiles with oversized hollow charge warheads.

The system was used on 'Mistel' composite aircraft and proved thoroughly unreliable and inaccurate. The Germans persevered with the system and at least one RN vessel was badly damaged by a near miss. The vast majority of launches, both test and operational, failed dismally.

There's a Mistel thread somewhere here in which I posted quite a bit of data to which I don't have access at the moment.

Cheers

Steve

 

[GrauGeist]

I suggest that the reason these systems didn't see service sooner was a primarily a conceptual one. Humans were thinking inside the box.

However, the concept had been in practice since WWI...how much longer would it take for the system to be perfected?

The Kettering Bug was proved to be a fairly accurate weapon in 1918, using rudimentary guidance systems of the time. It had a range of 75 miles (121 km) and an average speed of 50 mph (80 kph)...this was 20 years before the V1.

20 years is a long time when looking at the advancement of technology.

 

[Koopernic]

The system was used on 'Mistel' composite aircraft and proved thoroughly unreliable and inaccurate. The Germans persevered with the system and at least one RN vessel was badly damaged by a near miss. The vast majority of launches, both test and operational, failed dismally.

There's a Mistel thread somewhere here in which I posted quite a bit of data to which I don't have access at the moment.

Cheers

Steve

Their lack of success can be attributed to their being used in the face of a phenomenal scale of allied air power and return fire power from shipping that they faced during the Normandy landings. If used against a surprise target, such as a dam face, as they had been designed for they likely would have been capable of prevailing against the lessor defences.

The point I was making was that an autopilot was already quite accurate on its own. Trimming in commands either from a radar navigation or a command guidance system allowed pin point accuracy to be achieved.

 

[Koopernic]

However, the concept had been in practice since WWI...how much longer would it take for the system to be perfected?

The Kettering Bug was proved to be a fairly accurate weapon in 1918, using rudimentary guidance systems of the time. It had a range of 75 miles (121 km) and an average speed of 50 mph (80 kph)...this was 20 years before the V1.

20 years is a long time when looking at the advancement of technology.

The vacuum tube had only been invented a few years before WW1. It took barely 20 years till the 1930s for that technology to mature enough to allow radar, TV, radio and radio control, electronic navigation, power servo controls, analogue computation. The V2 for instance used an analogue computer liked to electrohydraulic vanes. It was the only system fast and vibration resistant enough to stabilise the missile.

There were several German WW1 attemps at radio and wire controlled air dropped torpedos and glide bombs. There were to be flown from Zeppelins or large aircraft.

They were truly guided, unlike the Kettering bug which really would have been only about killing civilians.

 

[tyrodtom]

And using Zeppelins had nothing to do with killing civilians ???

 

[GrauGeist]

I have to point out, especially in WWI, that there were very few civilians in the trenches and fortresses where the Bug was intended to be used.

The guidance system aboard the Bug may have been crude by today's standards, but it was effective enough to measure it's flight.

Saying the Bug was only about killing civilians can be applied to every single piece of military hardware in history: from the longbow to the ICBM...

 

[tyrodtom]

I wonder how many German civilians there were within 75 miles of the WW1 front lines?

 

[stona]

Their lack of success can be attributed to their being used in the face of a phenomenal scale of allied air power and return fire power from shipping that they faced during the Normandy landings. If used against a surprise target, such as a dam face, as they had been designed for they likely would have been capable of prevailing against the lessor defences.

No. Simply not the case as evidenced by the history of testing and operations for the 'Beethoven Gerat'. I recommend Robert Forsyth's 'MISTEL German Composite Aircraft and Operations 1942-1945' for a very good over view. The systems were not accurate or reliable. Even during completely unopposed testing the only thing they did consistently was fail to hit the intended target, they rarely came close.

I think you are applying 21st century hindsight to difficult, troublesome and for their time advanced mid 20th century technologies. The potential was certainly there but neither the Germans, nor anybody else, managed to realise it during WW2.

Incidentally they were not designed as dam busters. The guts of the war head was known as the SHL (Schwere Hohlladung) 3500. It contained 1,700 Kg of explosives. It was designed to pierce the armoured steel of battleships or blow open reinforced concrete targets. The easiest way to distinguish the variants is by the length of the so called 'elephant nose' extending from the front of the war head. Of course some dams would be a reinforced concrete structure and may well have been a target, just like bridges, bunkers etc.

Cheers

Steve

 

[Shortround6]

I am still trying to figure out when vacuum tube technology reached it's zenith and ALL radars, guidance systems, auto-pilots and the like just staggered along from this zenith sometime in WW II until the transistor took over in the 1950s, over a decade later.

All those vacuum tube radars and fire control systems in F-86Ds, F-94s and F-89s could have built at any time in late WW II right ??????

 

[Koopernic]

I have to point out, especially in WWI, that there were very few civilians in the trenches and fortresses where the Bug was intended to be used.

You think that thing could hit within a kilometre of a trench when an artillery shell could barely do so? This weapon could do only one thing, indiscriminately be used against inhabitants of cities.

 

[GrauGeist]

You think that thing could hit within a kilometre of a trench when an artillery shell could barely do so? This weapon could do only one thing, indiscriminately be used against inhabitants of cities.

I find that a little disturbing...really.

It's sole purpose was to reach into defended space and strike a reinforced target with a much heavier payload (180 lb - 82 kg) than was capable at the time, either by air or by artillery.

It's sole purpose of "indiscriminately be used against inhabitants of cities" is utter bullsh!t...it's wasn't the Paris gun, it wasn't a Zepplin taskforce, it wasn't Mustard gas - it was a proposed solution to strike fortified enemy positions within the entrenched battlefield in the hopes of creating a "breakout".

Reaching into defended space by artillery requires an increase in trajectory incline, which means the shells are falling on top of the fortified positions...this was designed to strike low on the enemy's position on one large "punch".

Just a recap: it was not designed to strike towns or cities, it was not designed to strike farms or villages. It was designed to impact fortifications...and suprisingly enough, very few civilians could be found in fortifications along the layers of trenches during WWI...most often, the people found within these areas were: soldiers!

 

[Koopernic]

I repeat: "The point I was making was that an autopilot was already quite accurate on its own. Trimming in commands either from a radar navigation or a command guidance system allowed pin point accuracy to be achieved."

IE auto pilot plus radar and remote control technology = precision guided weapon.

The Misteln were to be involved in operation Eisenhammer: a plan to knock out soviet hydroelectric production near key areas of the weapons industry that was expected to cut Soviet weapons production by around 2/3rds.

There was provision to guide the aircraft by remote control via the autopilot in a similar manner to the Hs 293 anti shipping missile.

Below is a photograph of an indicator dial used on the Nachtfee system which transmitted commands for the EGON blind bombing system. As you can see the dial could give dozens of commands to the pilot or bombardier/observer. It could just as easily be used to trim in a heading to an autopilot. This system couldn't be fooled or spoof as it was coherent and unless the jammer was in exactly the same location, within meters, any spoofing attempts would fail.

 

[kool kitty89]

When one of engineers in General Electric IIRC was asked 'why didn't you come out with jet engines years before the Germans; after all you were producing all kinds of compressors and turbines prior between the wars', he answered 'because it didn't dawned on us'. Or - it took many years for swept wings to take hold. So IMO it was one of the things that it was out there for the people to connect the dots. Like the British and Americans developing, producing and use of VT fuses, but Germany and SU did not in ww2 (apart from experimental stuff). Or APDS, or some countries neglecting the radars for many years.

I rather doubt that turbojet propulsion hadn't occurred to at least some GE engineering staff during the 1930s, if not early, but the issue would be having the ambition and belief that such technology was worthwhile and gaining funding/support for such a project. Without competition developing similar designs and without direct interest from the government, such projects might not be all that forthcoming. As it was, GE's supercharger designs during the 1920s and 30s had been pretty poor and lacking in development, at least until other manufacturers started taking such development upon themselves. (Wright, P&W, among others working on independent supercharger designs due to GE's lacking performance)

Part of GE's early success with the I-16 and I-40 (J31 and J33) was due to using Rolls Royce supercharger designs/experience along with the extensive combustion chamber development Powerjets had undertaken. (that being one of the critical limiting factors -functional, stable combustion) They also had issues with turbine efficiency and the initial I-A engines failed to meet the specified thrust, managing only around 800 lbf each rather than the anticipated 1250, and only after further modification based on copying more of Whittle/Rolls Royce's turbine modifications did those prototype engines finally hit the 1400 lbf thrust range, similar to Whittle's W.1A.

The only actual Jet Engine project being seriously undertaken in the US prior to WWII that I'm aware of is Nathan Price's Lockheed L-1000 design (later J37) and that was both impractically complicated and underfunded. (a more conservative direct followon to his preceding centrifugal compressor steam turbine aircraft engine into the turbojet concept may have been a good deal more practical and timely in development) Apparently it wasn't very widely publicized or promoted either, given the apparent ignorance of the rest of the aircraft industry of those attempted developments at Lockheed.



That said, I do agree on the point about many technological developments being limited by sheer random chance discoveries and connections made between ideas or lack thereof. Missing the potential of relatively simple and straightforward concept (or less simple but already documented and published -it not patented) is all quite possible. That's almost certainly the reason Jumo had working, practical flame cans fairly early in their engine development while other struggled for years working out the combustion problem. (yet Jumo ended up held back primarily by vibration issues) Heinkel/Ohain adopted hydrogen fuel to accelerate initial testing to sidestep the combustion problem entirely and then later adopted a simple fuel vaporization system based on a gasoline/kerosene blow torch when attempts at atomizing fuel injectors were lagging. Ohain adopted a radial turbine to make initial testing and development easier as well, something no one else seems to have attempted.

The same issues might might apply to the lack of thrust augmentor ducting or cowling applied to pulse jets or ramjets, and certainly would apply to a great deal of electronic tech.

Sometimes those ideas do actually meet but end up held back by political or bureaucratic issues or other failures to cooperate.

 

[kool kitty89]

The Air Ministry was approached in 1934 about a pulsejet powered flying bomb, so the potential was already there.

The problem was that the development of the engine itself was still in it's early stages. Add to that, the ideal placement of the engine for optimum performance hadn't yet been refined (the early design saw the pulsejet embedded in the fuselage) and finally, the technology behind the guidance system had yet to be developed to the point where reasonable accuracy could be expected.

Limited emphasis on pulse jet engine development in general certainly appears to have been a major limiting factor, not just for the V1, but for a variety of other potential applications. Even starting in 1934, there was a great deal of potential rapid development for that form of propulsion, both valved and valveless. There'd already been a great deal of research done into the concepts and related mechanisms (including aerodynamic valves) prior to that time, though I'm not sure how much of it was publicly available (NACA research at least would be, including cowling and thrust augmentation that would be applicable to pulse jets, ram jets, rockets, and turbojets -thrust augmentation using ducts in the exhaust stream to combine high volumes of air to increase working mass would have been especially useful for low-speed applications like JATO, but certainly would apply to the speed ranges the V1 was employing and like Me 163 as well -though at higher speeds, using ducting specifically designed to efficiently take advantage of ram effect would be more useful for given weight and drag added; the simplest form of augmentation would literally just be attaching a duct similar to a townend ring aft of the jet/rocket exhaust nozzle, somewhat larger diameter than the exhaust stream itself, and leaving an air gap between).

Pulse jets are incredibly simple mechanically, but tend to require a great deal of trial and error in development and a lot of theory breaks down in practice, at lest from the articles I've read on development. (this is true for almost any engineering effort, but it appears a far more long-lasting problem not easily solved by more modern developments in science and engineering aside from the advent of computer modeling to partially supplant physical prototyping) In any case, the best development strategy tends to be just shotgun engineering: building as much variety of test designs as you can imagine, even some that don't seem sensible or are totally random, test them all and build on the observations.

The simplicity and materials/fuels practical to work with (especially with valveless designs) make it possible for pulse jets to have been developed to great extent decades earlier than they were without any other technological advances (existing late 1800s or early 1900s metalurgy, riveting, welding and brazing techniques, fuels, ignition methods, among other things, especially if using a fuel feed system as simple as a the pressure vessels used in contemporary blow-lamps). The greater problem is actual need/demand for such engines, and given their inefficiency and the advent of piston engine driven propellers in the early 1900s, the main applications would tend to be novelty/toy/model use and military drones.

I am still trying to figure out when vacuum tube technology reached it's zenith and ALL radars, guidance systems, auto-pilots and the like just staggered along from this zenith sometime in WW II until the transistor took over in the 1950s, over a decade later.

All those vacuum tube radars and fire control systems in F-86Ds, F-94s and F-89s could have built at any time in late WW II right ??????

Even if you had the circuit design down for more advanced electronics, the vacuum tube technology itself was still a good bit more limited in the 1940s in terms of physical size, energy consumption, longevity, durability, etc. And even ignoring manufacturing costs, that all means bulkier, heavier, less reliable systems that require more power. (all of that is also part of the reason I suggested a larger cruise missile than the V1 itself might have been required to make adding more electronics viable, let alone cost effective -one could argue the added precision alone could more than make up the cost difference, but with the bulk/weight needed for electronics and possibly power supplies, it seems more plausible that increasing the warhead size would be significant as well -aside from potential of delivering far more deadly chemical or biological weapons, or perhaps shifting to incendiary bombs -the latter seems the most likely to actually be deployed)

Vacuum tube technology was improving and refining at very least well into the late 1960s, and aside from some military applications retaining their use due to potential redundancy or even on primary systems better hardened against electromagnetic damage, there was a great deal of use in consumer applications with more compact and cost reduced electronics. Not to mention, some tube based electronics were MORE compact and lighter (as well as cheaper) than their transistor counterparts for a time. Lots of oddities on the consumer market of the late 60s and early 70s. (GE's compact luggable Porta-Color television line comes to mind in particular, produced from 1966 to 1980 and surviving several attempts at solid state replacements due both to cost and weight).

 

[GrauGeist]

In regards to vacuum tube technology of the early to mid 1940's, look at the TDR's TV camera that's mounted in it's nose here: http://www.ww2aircraft.net/forum/aviation/drone-warfare-40838.html#post1126561

Just the TV camera's diameter is greater than that of the V1's fuselage.

 

[kool kitty89]

However, the concept had been in practice since WWI...how much longer would it take for the system to be perfected?

The Kettering Bug was proved to be a fairly accurate weapon in 1918, using rudimentary guidance systems of the time. It had a range of 75 miles (121 km) and an average speed of 50 mph (80 kph)...this was 20 years before the V1.

20 years is a long time when looking at the advancement of technology.

The guidance system aboard the Bug may have been crude by today's standards, but it was effective enough to measure it's flight.

Given the Bug used a rudimentary gyroscope stabilized autopilot system, it might not have been all that much simpler than a V1 (aside from the engine -the 4 cylinder piston engine is obviously more complex). Plus it had to deal with torque from the propeller, though not the level of vibration the As 014 produced.

The technology for simple unmanned drones and cruise missiles was obviously there much earlier than the operational V1, and aside from development interest and funding the matter of costs of production to value as a weapon (or drone, etc) would still be significant. (pulse jet vibrations are also a lot easier to cope with at smaller scales with much higher frequency pulsing -significant for smaller scale drones or even deployable weapons, or possibly used in batteries in leu of single larger engines)

Further, the intended purpose of the Bug is a bit closer to my earlier suggestion of a scaled down V1 better suited for tactical use and easier to launch from mobile platforms.

And of course, for decoy drones, you wouldn't need (or want) speeds nearly as high as the V1 offered. Mimicking fighter or bomber flight speeds and overall radar signature (within the limitations of radar of the day) would mean drones cruising closer to 200 mph.

In regards to vacuum tube technology of the early to mid 1940's, look at the TDR's TV camera that's mounted in it's nose here: http://www.ww2aircraft.net/forum/aviation/drone-warfare-40838.html#post1126561

Thanks for linking that thread. I'd overlooked some of the the unmanned drones already flying pre-war, particularly that Argus As 292.