Wasserfall antiaircraft rocket

GARGEAN said:
Well, from guidance law perspective it made little difference if target was moving in air or was standing on ground. Aerial target is even simpler in fact due to being point target at low contrast background. Anyways, I might quess that this was simple lead sulfide based AM-modulated seeker, like all those zero and first gen seekers. Still interesting to know if they used some unusual solutions in it.
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In theory - yes. On practice, the engineering solutions are quite complex, because both targets & missile are moving in 3D with considerable speed, both linear & angular.
 
GARGEAN said:
Anyways, I might quess that this was simple lead sulfide based AM-modulated seeker, like all those zero and first gen seekers. Still interesting to know if they used some unusual solutions in it.
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Well, Wiki quoted the Benecke "History of German guided missile development" (unfortunately I did not have this work):

AEG and Kepka of Vienna used systems with two movable plates that continually scanned horizontally or vertically, and determined the location of the target by timing when the image disappeared (AEG) or reappeared (Kepka). The Kepka Madrid system had an instantaneous field of view (IFOV) of about 1.8 degrees and scanned a full 20 degree pattern. Combined with the movement of the entire seeker within the missile, it could track at angles as great as 100 degrees.

So it seems to be the rather primitive device, in which seeker rotates to provide scanning with some "blind spot" directly forward. If the target appeared in sight, then the seeker relay would be closed, and the exact moment in seeker scanning cycle, during which target was observed, would determine the autopilot response. And if the target is directly ahead, then it would disappear from seeker field of view completely & missile would flight straight forward.

The obvious problem with that kind of device is that it have no ability to discriminate between "target directly forward" and "no target". So if target was lost, the missile would make no attempt to reacquire, because (from its point of view) the trget is still directly forward. Also, when fired against bomber formation, seeker would probably be very confused by multiple signatures, and missile would zig-zag between bombers, not hitting anything.
 
Dilandu said:
more complex task, because it would need to hit a target in 3D space
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I think, guiding a missile at an aerial target is still guiding in 2D space, only X/Y coordinates have to be controlled.

Dilandu said:
So it seems to be the rather primitive device, in which seeker rotates to provide scanning with some "blind spot" directly forward.
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According to my notes, the Madrid was equipped with a 28 cm parabolic mirror, pneumatically moved, an Elac IR detector cooled with LOX, and 5 tubes. FOV was 18 degrees, switching to 1.5 degree after locking on a target, range probably 3000 m.
 
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GARGEAN said:
I am interested specifically in IR seeker.
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unfortunatey there are no books known which contain actual mechanisms and circuits for ir seekers as only few internet website explain the theory but how actually it is done is still a mystery as engineers still hide it.But building ir seekers sholudn't be a big deal since if you can built a "sun tracker(ir diode only)" then practically you have a seeker.
 
The significant issue for an IR system at the time would be signal to noise. The electrical output from the cell is tiny, the piston engine exhaust was rapidly diluted in cool air and the 40’s vintage thermionic values were inherently electrically noisy. So one way to fix this is improve the signal by increasing the delta T hence the use of LOX . This fundamental problem was only really practically fixed when the transistor (which works well at low signal levels) came about and jets provided a much hotter heat source.

Ten years after the German work when the IR homing Firestreaks were tested against radio control piston engine targets (Fairy Firefly’s) they had to install a kerosene fuelled blow lamp in a pod to provide a workable heat source.
 
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Grzesio said:
I think, guiding a missile at an aerial target is still guiding in 2D space, only X/Y coordinates have to be controlled.
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Only if you use the straightforward approach, i.e. when the missile is aiming directly at the plane.

Grzesio said:
According to my notes, the Madrid was equipped with a 28 cm parabolic mirror, pneumatically moved, an Elac IR detector cooled with LOX, and 5 tubes. FOV was 18 degrees, switching to 1.5 degree after locking on a target, range probably 3000 m.
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Thank you for the data!

arshin said:
unfortunatey there are no books known which contain actual mechanisms and circuits for ir seekers as only few internet website explain the theory but how actually it is done is still a mystery as engineers still hide it.But building ir seekers sholudn't be a big deal since if you can built a "sun tracker(ir diode only)" then practically you have a seeker.
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Well, the old-type IR seekers are well-known. You could find the complete description of Ke-Go IR seeker here:


Of course, it was quite primitive device, but workable, and it get the whole theory.
 
Dilandu said:
Only if you use the straightforward approach, i.e. when the missile is aiming directly at the plane.
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Egh... No? Missile with IR seeker (and in fact many other types of guidance) don't know range to target and not flying straight at it, but into predicted interception point trough zeroing angular velocity.
 
GARGEAN said:
Egh... No? Missile with IR seeker (and in fact many other types of guidance) don't know range to target and not flying straight at it, but into predicted interception point trough zeroing angular velocity.
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Such primitive seeker as mentioned above - that could only detect the "appearance/disappearance" of the target have no means to calculate the predicted interception point. Modern one - yes, could use constant bearing. But those WW2 units could, at best, point the missile straight on target.
 
Dilandu said:
So it seems to be the rather primitive device, in which seeker rotates to provide scanning with some "blind spot" directly forward.
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As I understand, the Madrid had no blind spot, it used lineal scanning of the whole FOV with a pair of perpendicularly moving masks, with target coordinates established by timepoints, at which the masks were revealing the target.
 
Dilandu said:
Such primitive seeker as mentioned above - that could only detect the "appearance/disappearance" of the target have no means to calculate the predicted interception point. Modern one - yes, could use constant bearing. But those WW2 units could, at best, point the missile straight on target.
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If by "modern ones" you mean oldest ones with simple AM seekers - then I can agree.
 
For me.. the only problem for Wasserfall is that there just not enough time for it to properly developed.
 
Grzesio said:
By the way - what was so wrongly designed in the Wasserfall?
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As far as I knew, when Soviet engineers designed R-101 missile (reverse-engineered Wasserfall), they were forced to eventually redesign the whole engine, because German one was just impossible to made reliable and re-work the feeding system, because German one was inefficient. The command guidance system never worked as intended, and our engineers were of general opinion that it is pointless even to try to make it right, because it was basically a modified variant of Kehl-Strasbourg RC system, essentially a 1930s technology.

Eventually, the situation came to the point when there were no two exactly similar examples of R-101, because each attempt to perfect the system caused more and more rebuilds. In 1951, the R-101 project was cancelled because no one could actually be sure that this pile of German junk could be made workable at all.
 

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