Kramer X-4 Air-To-Air Missile

[red admiral]

One of the air to air missiles closest to use was the German X-4 wire guided missile. After reading of the British efforts in BSP4 I'm wondering how effective it would have been. Most of the British designs were rejected from lack of range but the X-4 is fairly similar. At the same time, the postwar beam riding missiles were a bit of a failure. How is a manually guided missile going to do? I have some concerns over the liquid fuel engine as well.

Any thoughts?

Thanks

 

[Jemiba]

There were two pretty comprehensive articles in Flugzeug Classic last year. Apart from
the liquid fuel rocket engine, a solid fuel rocket was tested, too, although, IIRC, mainly due
to delays in the development of the chosen engine. The development of the X-4 was hampered,
too, by delays with the proximity fuse.
Against a bomber sized target, this missile probably could have been effective, if the attacker
wasn't shot down in time by escorting fighters ! A single seat fighter perhaps wasn't the best
choice, as the pilot couldn't maneuver freely, as long as he was guiding his missile.

P.S.: If you are interested in the mentioned article (in german !), just send a PM ...

 

[Justo Miranda]

From "Hitler´s guided weapons" by Dr. Alfred Price , "Aeroplane" January 2005

 

[Stargazer]

X-4 (GERMAN)

The air-to-air rocket-propelled winged missile X-4 was designed by Max Kramer beginning in June, 1943. About 250 missiles were built and about 150 tested. The gross weight is 132 lb of which 44lb is war head. Propulsion is by means of a liquid fuel rocket weighing 31 lb (empty) and giving a thrust of 242 lb for 17 sec. About 19 lb of fuel were provided.

The missile is approximately 75 in. long, 8.7 in. in diameter, with wing span of 23 in. The speed is about 790 ftl sec, the horizontal range about 1.2 miles.

The missile has four sharply swept-back wings near the center of gravity and four tail fins. Aerodynamic control is by means of spoilers on the tail fins. Tabs on the wings cause the missile to spin. Two of the wings carry at the tips spools of fine wire 0.009 in. in diameter and long enough to permit a range of about three miles while maintaining direct-wire connection to the control aircraft. A gyrostabilized commutator in the missile and a suitable filter system permit direct electrical transmission of the control from the operator to the spoilers on the control surfaces of the missiles by means of the connecting. wires which can feed out at speeds of more than 650 ft/sec.

A document dated 11 January 1945 stated that 130 trials had been made. It was stated that the missile was in the early testing stage to prove its fundamental correctness of functioning. At one time the Air Ministry had a requirement for 5000 missiles by the middle of 1945 but this was later reduced. In February, 1945, SS leader Kammler ordered a lower priority and the closing out of the project at the end of the development period.

Kramer designed an acoustic proximity fuse for this missile known as "Kranich." About 30 were built and some preliminary fly-over and fly-by tests were made. The effective range was expected to be 45 ft. The tests which had been completed were promising. Work was also under way to develop an acoustic homing device with a hoped for range of from 1650 to 3300 ft.

Source: Guidance and Homing of Missiles and Pilotless Aircraft, May 1946

 

[pathology_doc]

Given how desperate they were for defensive weapons, and how much of an advance their guided weapons (including the surface-to-air ones) represented over AA artillery, cannons and unguided RP, it's surprising the Nazis never fired a few off in anger. What did they have to lose, after all?

 

[Jemiba]

... What did they have to lose, after all?

After first tests (AFAIK still unguided) with single seat fighters (Fw 190), the X-4 was intended to be used from
multi seat/twin engined fighters only, because of problems with guiding the missile and flying the aircraft. Additionally
the guiding wires were endangered to be cut by the propeller in single engined fighters. The X-4 was limited to daylight
attacks, as the operator had to guide it visually. That would have meant daylight attacks by aircraft like the Me 110/410
or Ju 88 from distances of about 4000m, something that had already be proven to be more or less suicidal with the
appearance of escort fighter like the P-51 or P-47.

 

[legranddudu]

Friends,

I am looking to get more info on the Rheinmetall-Borsig Feuerlilie F25. I am a rocket modeler from Germany. I built and flew successfully a 90% scale Kramer X4

(http://www.rocketryforum.com/showthread.php?52241-90-RUHRSTAHL-KRAMER-X4-(1944-1945)

Now I want to build a flying full scale Feuerlilie F25.

I am particularly looking for:

- accurate drawings (Post war from Allied Services?)

- pictures, especially from the F25 that is exposed in RAF Museum Cosford. The issue at the moment is to picture out the tailcone. Has anyone a detailled picture from the back/thrust plate of the F25? I cannot find anything. The tail cone looks really particular...

Thx for your help

Denis

 

[Hood]

I have a photo I took of the X-4 at Cosford a couple of years ago. It might be of some use to you.

 

[legranddudu]

Thx, the X4 pics and text was only to inroduce myself to the forum. At the moment I look for plans, drawings or pics of any sort to start building a full scale Feuerlilie F25..

If someone has or can make a series of pictures of the F25 exposed in Cosford I would be really thanksfull, especially pictures from the aft of the bird.

thx
denis

 

[klem]

Historically one of the most important missiles, as it is the introduction to air-to-air missiles as an effective action, it is wire-guided, its design was initiated by Dr. Max Kramer of Ruhrstahl in 1943, under the designation RK 344 of the German Air Ministry. Abandoning the shape of an airplane, Kramer chose the configuration of the Fritz-X, with cross-shaped wings placed around the center of gravity and cross-shaped ailerons with control rudders placed in the tail of the missile, turned 45 degrees in respect of the wings. The swept wings reduced aerodynamic drag while the missile was suspended from a turbojet aircraft and allowed it to briefly reach speeds in excess of Mach 1 after the ignition of the BMW 548 rocket engine.but this overview exists in all the technical documentation relating to the X-4.This was for the history of the X-4 which continues to generate interest even in an auction where a unique piece of an authentic X-4 was exposed for sale.

 

[Orionblamblam]

Site says this sold for a shockingly measly $7,050.

 

[edwest4]

Drat! And no one told me... It would have gone nicely with my Ta 154.

 

[klem]

A very interesting article about the X-4 in Waffen Revue 1998.the author tells the subject point by point,from the beginning of the X-4 adventure to its realization.an article to read without getting tired between the websites.

 

[Nicknick]

I found this really good clip about this rocket:

View: https://www.youtube.com/watch?v=zXan1fo6qi0&ab_channel=Dave_sic

 

[T. A. Gardner]

Actually, the X-4 was virtually worthless as a guided AAM. The wire guidance was, at best problematic. Using the FuG 510/238 Dusseldorf-Detmold MCLOS system by Telefunken was so inadequate as a guidance system as to make the missile more of an unguided AAM.

The missile itself was simply too small, and its warhead inadequate for an early AAM.

As far as its importance to development of other AAM's, the X-4 was a technological dead end that NOBODY copied in any way. The guidance system was dumped as unworkable. The Kransch acoustic proximity fuze was not proceeded on or copied by anyone. The missile being subsonic (and there's ZERO evidence to show it could exceed Mach) made it a worthless example compared to postwar development efforts into an AAM.

 

[Harry64]

Any primary sources for your statements or just guesses?

 

[Nicknick]

As far as its importance to development of other AAM's, the X-4 was a technological dead end that NOBODY copied in any way. The guidance system was dumped as unworkable. The Kransch acoustic proximity fuze was not proceeded on or copied by anyone. The missile being subsonic (and there's ZERO evidence to show it could exceed Mach) made it a worthless example compared to postwar development efforts into an AAM.

According to the video, the French kept on working on this design until 1950, so either the video is wrong or you. Dave_sic linked his sources, you migh go through them or bring your own evidence.

 

[Dilandu]

Any primary sources for your statements or just guesses?

French tried to make it work. Their Nord AA.20 was essentially the same idea - visually tracked, manually-guided air-to-air missile - but with proximity fuze and radio control link instead of wires. The results were the same; human reaction was just too slow to guide missile in aerial interception.

According to the video, the French kept on working on this design until 1950,

Yeah, but they worked on it as anti-tank missile, not anti-air. As anti-tank weapon, it actually worked quite good.

 

[Nicknick]

This is quite a contradiction to your previous post... The X-4 was also using a proximity fuse (accoustic) which is very well described in the video.

 

[Dilandu]

This is quite a contradiction to your previous post... The X-4 was also using a proximity fuse (accoustic) which is very well described in the video.

Yeah, with the radius of approximately seven meters. Considering that the average closing velocity of X-4 with the propeller-driven bomber would be about 100-150 meters per second, it would require far faster reaction that human could achieve (0,15-0,2 second on average) to guide it into a lethal range.

 

[Nicknick]

So the statement that NOBODY copied it in any way was clearly false. It sure showed potential, otherwise the French wouldn’t have continued the development.

Of course, it was a weapon of WWII and a device against subsonic propeller driven bombers. This was surly not a wrong priority proving any lack of electronic competences. It is clear, that it found a natural death when the Jet age started, but the X-4 can’t be blamed for that…

Youre calculation is also wron, no one would attac a bomber from the side, but from behind. The gunner could have had a very reaction time, since he just needs to direct the rocket streight towards the bomber. Due to the proximity fuse, he doesnt have to estimate the distance or to pull a triger for ignition, its a simple continously process.

 

[T. A. Gardner]

As far as its importance to development of other AAM's, the X-4 was a technological dead end that NOBODY copied in any way. The guidance system was dumped as unworkable. The Kransch acoustic proximity fuze was not proceeded on or copied by anyone. The missile being subsonic (and there's ZERO evidence to show it could exceed Mach) made it a worthless example compared to postwar development efforts into an AAM.

According to the video, the French kept on working on this design until 1950, so either the video is wrong or you. Dave_sic linked his sources, you migh go through them or bring your own evidence.

They did do some testing as the AA 10 with it. However, they found its low speed, MCLOS guidance, use of liquid fuel, and unreliability all traits they couldn't get past. See: La Saga des Missiles Européens for example. The whole program was dropped by 1951 as far better AAM's were close to being introduced into service. Dilandu is correct in stating that any developments the French made were found to be unworkable with systems similar to the X-4.
It would be competing programs that the French did adopt for an AAM rather than use German wartime technology.

The US did look at the Kranch fuze at Wright Field briefly under one of the MX series programs (I have a list somewhere of the exact program number) but that program was brief and nothing came out of it.

As for the US, they had no reason to copy or test the X-4 as their own programs into an AAM in 1945 were ahead of the Germans in any case:

On March 8, 1945 the first live fire test against a TDC-2 target drone of a Gorgon IIA using TV MCLOS took place off Cape May NJ. The system was the same as used successfully on the Bat and Pelican guided bomb. The Navy’s project engineer, Cdr. Moulton “Molt” Taylor, reported that this guidance system was unworkable against an aerial target where closing speeds were too high for human mind and hand-eye coordination to match the speed of response needed to make it work. This launch represents the first time in history that a guided air-to-air missile had been tried in a live fire test against a target.

The USAAF, likewise adopted the NACA's test missiles into guidance at Wallops Island VA as the JB-3 Tiamat in late 1944. It too was in advance of the German missile using a variety of guidance systems like semi-active and active radar homing, TV MCLOS and MCLOS control. This was followed closely by the Ryan AAM-A-1 Firebird AAM.

The Russians immediately after the war didn't do much towards developing an AAM, and when they did it was not based on German wartime technology. The British, likewise, used homegrown technology, not captured German to develop their early AAM's.

 

[Nicknick]

I showed the parts which were clearly not correct.

"Dilandu is correct in stating that any developments the French made were found to be unworkable with systems similar to the X-4."

As said, this was a device which was developed in short time to shoot down propeller driven bombers. It is no suprise, that it came to a natural death in 1950.

"The USAAF, likewise adopted the NACA's test missiles into guidance at Wallops Island VA as the JB-3 Tiamat in late 1944. It too was in advance of the German missile using a variety of guidance systems like semi-active and active radar homing, TV MCLOS and MCLOS control. This was followed closely by the Ryan AAM-A-1 Firebird AAM."

Building somthing overly complex which was not ready before the war ended is not superior engineering. The X-4 rocket was built out of very simple inginious elements.

 

[Dilandu]

So the statement that NOBODY copied it in any way was clearly false. It sure showed potential, otherwise the French wouldn’t have continued the development.

French continued the development mainly because they felt that they fell behind USA and USSR (and UK) in advanced weapon development, and hoped that extensive use of German technology would allow them to quickly catch up for half-price. The result was far from satisfactory, actually. While France did extensive research on German guided weapons, and tried to refine them into combat-ready condition, nearly everywhere they came to the same conclusion as USA and USSR; it would be much simpler to just start from scratch, instead of trying to remedy every mistake, overcomplication and plainly dumb idea that Germans put in their designs.

In case of X-4, French engineers quickly concluded that it's unworkable in intended role as AAM, and too dangerous to actually use (yep, liquid fuel rocket on AAM - not a good idea at all). On the other hand, the guidance system actually was fine and even elegant (spin-stabilization with a single gyro maintaining the vertical axis). So they tried to adopt the guidance system to the other role, that French military considered of uppermost importance - anti-tank weapon. And sucseeded here.

 

[Dilandu]

Of course, it was a weapon of WWII and a device against subsonic propeller driven bombers. This was surly not a wrong priority proving any lack of electronic competences. It is clear, that it found a natural death when the Jet age started, but the X-4 can’t be blamed for that…

The thing is, that Britain toyed a lot with the idea of manual-guided AAM in 1941-1943. While Germans did not proceed further than simple visual tracking, British actually attempted to use a AI radar to track the missile in flight (the operator would track the missile with the help of two A-scopes, and hold it at the center of the radar beam, while pilot would hold radar beam on target). And British came to conclusion, that the idea of manually-controlled AAM is self-contradictory:

* To make less need of course corrections, the missile must fly as fast as possible
* To make correction within human reaction capabilities, the missile must not fly as fast as possible

That's why British abandoned their "air launched Spaniel missile" concept and switched to automatic guidance.

Youre calculation is also wron, no one would attac a bomber from the side, but from behind.

Actually I described exactly the tail-chase scenario.

The gunner could have had a very reaction time, since he just needs to direct the rocket streight towards the bomber.

Yeah, "just needs". The problem is, that A - fighter is not ideally stable in air, B - target is not ideally stable in air, C - the missile flight is not stable either.

Due to the proximity fuse, he doesnt have to estimate the distance or to pull a triger for ignition, its a simple continously process.

The proximity fuse on X-4 is so short-ranged, that it didn't actually add much to the missile capabilities.

 

[Nicknick]

You should decide wether it was a dump uncontrolable system or if the guidance system worked fine.

Progress was fast in that time, of course you need to find new solutions and not try to copy the old ones.

"remedy every mistake, overcomplication and plainly dumb idea that Germans put in their designs."

Nothing could be farer from truth! The X-4 is a very simple system and the accoustic proximity fuse would have cost only a fraction of a radar system. It was a low cost rocket, made for large scale production with little recources. Of course, in peace time without the pressure of designing cheap for high quantities you will find better solutions. But this is a different game.

 

[Dilandu]

You should decide wether it was a dump uncontrolable system or if the guidance system worked fine.

Sigh. The guidance system worked fine. The guidance METHOD was unworkable for air-to-air role. It was, though, perfectly fine for a simpler anti-tank role.

The X-4 is a very simple system

Are you kidding? Just look at this horrendous spiral fuel tank, those overcomplicated wire drums! This missile was complex, hard to build, and dangerous to maintain.

It was a low cost rocket, made for large scale production with little recources.

You know the old rule - complex problems always have simple, cheap, easy to comprehend wrong solutions? Well, you have an example in X-4. Not only it wasn't cheap (the idea of using liquid-fuel engine was bad from the very beginning, and the wire control was used mainly because Germans could not create a compact enough FM radio control link - not to mention that they feared Allied jamming), or suitable for large scale production (spiral tanks!), but it also was not able to perform its intended function even in theory, much less in realistic conditions.

 

[Nicknick]

Please explain your calculation, they dont make any sense to me. Maybe you could provide a scetch an explain when exatly the fast reaction time would have been needed.

In any air combat you are facing the same problem with moving targets. but with active steering and a proximity fuse, hitting the target will become much much easier. Keep in mid, you need to hit exactly a week spot with guns!

 

[Dilandu]

Seriously, if you seek for "simple, cheap, workable" WW2 air-to-air missile, then it would probably be the British "Artemis":

(art not mine)

 

[Nicknick]

So the guidance system worked fine, just few minutes ago, it was uncontrolable....

You are not an engineer, otherwise you might notice that bending a spiral out of a pipe is very simple process.... The use of a spiral allowed to use a simple iston which seperatres the pressurized air from the fuel.

The Germans couldnt afford to use expensive radio equipment against low value targets like bombers. For this reason, the Fritz-X was only allowed to use against high value big ships. It would have been impossible to use a simillar expensive system against a large number of bombers.

So how do your scetches show the need for a fast reaction time?

By the way, I dont understand Russian...

 

[Nicknick]

"artemis, named for the Greek goddess of the chase and death, was an early air-to-air missile project carried out by the Royal Aircraft Establishment (RAE) beginning in late 1943. The missile was intended for radar-equipped night fighters like the Bristol Beaufighter, which would track the target on their AI Mk. IV radar and then fire at a set range, with the missile homing on the signal of the AI radar being reflected off the target."

Honestly, you find that simple???

The proximity fuse of the X-4 was just a piece of sheet metal! The control was done by wires, it couldnt be any simpler that that!

 

[Dilandu]

So how do your scetches show the need for a fast reaction time?

By the way, I dont understand Russian...

Seems you don't understood English either, because I specifically noted that they are NOT mine. They are translation from "British secret projects", if I understood it correctly.

 

[T. A. Gardner]

On the X-4, wire guidance was very problematic. The Germans never really tested that part of the system. The wires were 22 gage spring steel imported from Sweden coated with electrical varnish like you use in motor windings. Each of the two wires carried one of two signals that controlled the missile. These ran at +/- 200 VDC. One pair gave a signal for Left-Right +/- and the other for Up-Down in the same manner. You could input one signal at a time and the system was "all-or-nothing." That is, the missile's spoilers deflected 100% or 0.

The big problem with this system is that the wire is free between the plane and missile. If the tension increases too much the wires snap. Too little, and you get sag that could foul the control plane.

An alternative to the Duren-Detmold guidance system that was proposed was using a radio control MCLOS in its place, the Kran-Waltzenbrigg (Fug 512 / FuG 530) system that was a variant of the original Kehl-Strassburg system. Walzenbrigg was made such that it would fit in the wingtip bobbin space where the wire was. So, even the Germans were looking at a radio control system even if it didn't materialize.

The Germans did experience lots of issues using liquid fuel in the X-4 from failure of the firing mechanism to fire the pistons, to improper fuel mixtures causing reduced thrust or even motor detonations, to burn through of the motor and nozzle, etc. These were common to all liquid fuel rocket motors of that period, and big part of the reason solid fuel engines were the go-to choice for AAM's.

 

[Nicknick]

@Dilandu
It was clear to me, but it is still unclear what is the essence of that. When do I have to react very fast in those scetches???

 

[Dilandu]

Honestly, you find that simple???

Yes it was. They proposed extremely elegant control system, with the conical scan performed by fixed offset antenna by the spin of missile - and a single control element used to turn missile into the direction of the signal. No gyros at all, no roll stabilization, no complex switches for control system.

 

[Nicknick]

Honestly, you find that simple???

Yes it was. They proposed extremely elegant control system, with the conical scan performed by fixed offset antenna by the spin of missile - and a single control element used to turn missile into the direction of the signal. No gyros at all, no roll stabilization, no complex switches for control system.

You would have needed radar (expensive) and rader receivers (expensive), an RC system (expensive), a humming device (expensive) and so on. If any German engineer would have proposed such a system for shooting down hundreds of bombers, he would have been sent to the eastern front immediately.

The X4 just needed some wire, some solenoids and a piece of sheet metal for the same job. Of course, the more refined system could have had a higher precision (10 years after…) but this was a massive waste of resources for simple bombers!

 

[Nicknick]

On the X-4, wire guidance was very problematic. The Germans never really tested that part of the system. The wires were 22 gage spring steel imported from Sweden coated with electrical varnish like you use in motor windings. Each of the two wires carried one of two signals that controlled the missile. These ran at +/- 200 VDC. One pair gave a signal for Left-Right +/- and the other for Up-Down in the same manner. You could input one signal at a time and the system was "all-or-nothing." That is, the missile's spoilers deflected 100% or 0.

The big problem with this system is that the wire is free between the plane and missile. If the tension increases too much the wires snap. Too little, and you get sag that could foul the control plane.

An alternative to the Duren-Detmold guidance system that was proposed was using a radio control MCLOS in its place, the Kran-Waltzenbrigg (Fug 512 / FuG 530) system that was a variant of the original Kehl-Strassburg system. Walzenbrigg was made such that it would fit in the wingtip bobbin space where the wire was. So, even the Germans were looking at a radio control system even if it didn't materialize.

The Germans did experience lots of issues using liquid fuel in the X-4 from failure of the firing mechanism to fire the pistons, to improper fuel mixtures causing reduced thrust or even motor detonations, to burn through of the motor and nozzle, etc. These were common to all liquid fuel rocket motors of that period, and big part of the reason solid fuel engines were the go-to choice for AAM's.

This is writen about the Artemis/Spaniel:
"The primary concern with the Spaniel was its short flight time, on the order of six seconds when fired at its ideal range of about 2,000 yards (1,800 m). Flight Lieutenant Benson of the RAE had worked on Spaniel and felt that the operator would have too little time to accurately guide the weapon, especially given the first two seconds were unguided. He also pointed out systems were needed to keep the missile from spinning, which would make manual control impossible if the "up and down" axis continually rotated. These systems added significant cost and complexit

The X-4 had more than twice the range than the Artemis, due to the liquid propulsion system and the wire control. The gyro stabilisation of the X-4 was also somthing which would have helped the Artemis a lot....

 

[Dilandu]

You would have needed radar (expensive)

Radar is on the plane, and since Germans themselves stated that it was impossible to use X-4 from single-seat fighters - then the cost of radar set is essentially included into the cost of the heavy fighter.

and rader receivers (expensive),

For Germans with their sub-par electronic production - yes, indeed. For British and Americans? No.

The X4 just needed some wire, some solenoids and a piece of sheet metal for the same job.

...A gyro, a fast-working commutator, a high-speed wire drums. Those things aren't cheap at all (especially gyro).

 

[Dilandu]

The X-4 had more than twice the range than the Artemis, due to the liquid propulsion system and the wire control. The gyro stabilisation of the X-4 was also somthing which would have helped the Artemis a lot....

Yeah, yeah. And how cold harsh reality:

1) Germans themselves concluded that liquid fuel system is not reliable, and worked on solid-fuel motor to replace it.

2) Wire control have nothing to do with range. If anything, it lessened it due to the weight and complexity of the wire.

3) X-4 did not have any gyro stabilization! It was spin-stabilized! The gyro was used only to establish reference system when missile rotated, and turn a commutator to connect the output of command system to the azimuth/elevation control, depending on the orientation of missile at this moment.

4) The whole point of Artemis was to get rid of heavy and very costly gyro.

Seriously, you seems to not understood how exactly X-4 worked.

 

[Nicknick]

1. the better is the enemy of the good

2 the Artemis fell out of range of the rc system, so wires could have helped a lot...

3. Spining bodies are automatically gyro stabilized. The gyro itself was for the reference, this is clear.

4. The Artemis was full of expansive electronic features and was underpowered, this was propable the reason, why it didnt contain a gyro. So it was uncontrolable. Here, you really needed a fast reaction time, because in the first two seconds the Artemis was not
controlable at all!

A gyro is a simple mechanical device, most parts can be made out of steel (exept the driving engine). At that time, a radar system could have easily been more expensive than 100 steel disks dynos... The proplem with the dyno is the additional weight which the underpowerd heavy Artemis couldnt carry.