V1s start being launched 2 weeks earlier

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T. A. Gardner
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Re: V1s start being launched 2 weeks earlier

Post by T. A. Gardner » 13 Jan 2023 07:27

Well, if the Germans were up to where the US and British were on radar and guidance systems, they could have turned the V-1 into an antiship missile and done major damage to both navies...

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Re: V1s start being launched 2 weeks earlier

Post by Sheldrake » 13 Jan 2023 11:29

T. A. Gardner wrote:
13 Jan 2023 07:27
Well, if the Germans were up to where the US and British were on radar and guidance systems, they could have turned the V-1 into an antiship missile and done major damage to both navies...
The Germans had already developed air to surface guided weapons specifically as anti shipping munitions

Image
The He 293 wiuth a 500KG payload was used operationally from August 1943, ten months before the first V1 was launched on London. It seems to have had some success https://en.wikipedia.org/wiki/Henschel_Hs_293

Image

The Fritz X was a 1400KG radio guided glide bomb designed to penetrate armour. First deployed in July 1943 its victims includen the IUtalian Battleships Roma and Italia, HMS Warspite, USS Savannah and Philadelphia and various merchant ships.

The problem with any radio guided system is that it was vulnerable to counter measures. The V1 was a pre programmed drone and invulnerable to ECM. Inertial guidance systems to allow an accuracy within metres rather than kilometers were decades away in the 1940s.

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Re: V1s start being launched 2 weeks earlier

Post by T. A. Gardner » 13 Jan 2023 18:21

Sheldrake wrote:
13 Jan 2023 11:29
T. A. Gardner wrote:
13 Jan 2023 07:27
Well, if the Germans were up to where the US and British were on radar and guidance systems, they could have turned the V-1 into an antiship missile and done major damage to both navies...
The Germans had already developed air to surface guided weapons specifically as anti shipping munitions

Image
The He 293 wiuth a 500KG payload was used operationally from August 1943, ten months before the first V1 was launched on London. It seems to have had some success https://en.wikipedia.org/wiki/Henschel_Hs_293

Image

The Fritz X was a 1400KG radio guided glide bomb designed to penetrate armour. First deployed in July 1943 its victims includen the IUtalian Battleships Roma and Italia, HMS Warspite, USS Savannah and Philadelphia and various merchant ships.

The problem with any radio guided system is that it was vulnerable to counter measures. The V1 was a pre programmed drone and invulnerable to ECM. Inertial guidance systems to allow an accuracy within metres rather than kilometers were decades away in the 1940s.
Those require air launch and the launching aircraft to have visual sight of the target. A V-1 that was equipped like the USN Bat or Pelican glide bombs with an active radar homing system and ground launched would have been a serious threat. You have a missile approaching at low altitude doing 400 + mph with say a 1500 lbs. (smaller to make room for the guidance and control) that can home on a ship using radar on its own.

Fire, forget, repeat.

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Re: V1s start being launched 2 weeks earlier

Post by wm » 13 Jan 2023 22:35

Although ww2-era radars were easy to jam (just transmit noise on the frequency at full power of the ship radio) and only the human operator was capable to defeat the jamming (not always).

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Re: V1s start being launched 2 weeks earlier

Post by T. A. Gardner » 14 Jan 2023 05:21

wm wrote:
13 Jan 2023 22:35
Although ww2-era radars were easy to jam (just transmit noise on the frequency at full power of the ship radio) and only the human operator was capable to defeat the jamming (not always).
Not true. First, ship's radios didn't operate--for the most part-- on millimeter wavelengths. Second, you need some directionality to that. Third, noise jamming only works to a certain distance beyond which the system being jammed can burn through the noise.

Against Fritz X and Hs 293 operators would tune their equipment to the detected guidance frequency for jamming.

Against an active homing missile or glide bomb, you'd need to do the same thing.

Chaff could be effective, but the radar could have a pulse doppler mode (like Wurtzburg with Wurtzlaus) that rejects objects that aren't moving.

Then add in most, if not all, merchant ships would not have any sort of jamming equipment aboard.

Most warships by 1944 had some ESM and ECM systems aboard, so they probably could at least attempt to jam an incoming missile assuming they detect it.

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Re: V1s start being launched 2 weeks earlier

Post by wm » 14 Jan 2023 09:08

The Germans didn't have magnetrons, so the Allies didn't need millimeter radios. Without magnetrons, small radars weren't possible anyway.

Of course you didn't need directionality; by definition, the power of the ship radio was thousands of times greater than a return signal from the ship.

Additionally, the ww2-era electronics weren't capable of identifying and auto-locking on the target. They were way too bulky for that.
Existing gliding bombs (e.g., the ASM-N-2 Bat) had to be aimed and locked on the target visually (it was locked on the target prior to launching).
Otherwise, its dumb radar would pointlessly lock on ground or sea clutter.

And because of sea clutter, I'm quite sure their radar wouldn't work anyway at low attitudes, so no sea skimming.
This is why they had to be launched at altitudes of 15,000 to 25,000 feet.

In the case of ships, chaff works by hiding the target. If you couldn't see, you couldn't lock; and no wizardry would help to overcome it.

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Re: V1s start being launched 2 weeks earlier

Post by T. A. Gardner » 14 Jan 2023 18:12

wm wrote:
14 Jan 2023 09:08
The Germans didn't have magnetrons, so the Allies didn't need millimeter radios. Without magnetrons, small radars weren't possible anyway.

Of course you didn't need directionality; by definition, the power of the ship radio was thousands of times greater than a return signal from the ship.

Additionally, the ww2-era electronics weren't capable of identifying and auto-locking on the target. They were way too bulky for that.
Existing gliding bombs (e.g., the ASM-N-2 Bat) had to be aimed and locked on the target visually (it was locked on the target prior to launching).
Otherwise, its dumb radar would pointlessly lock on ground or sea clutter.

And because of sea clutter, I'm quite sure their radar wouldn't work anyway at low attitudes, so no sea skimming.
This is why they had to be launched at altitudes of 15,000 to 25,000 feet.

In the case of ships, chaff works by hiding the target. If you couldn't see, you couldn't lock; and no wizardry would help to overcome it.
I pointed out in earlier in the thread that the Germans would have needed radar and guidance technology on par with the Allies (like say the USN's Bat or Pelican) to do this. Bat only needed to be pointed in the correct direction as its radar had a limited field of view. You get rid of wave clutter by antenna polarization and use of a pulse doppler signal that removes most of it.

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Re: V1s start being launched 2 weeks earlier

Post by wm » 15 Jan 2023 21:21

Yes, a skillful operator of an advanced (by ww2 standards) radar set could use those tricks to partially mitigate the effects of clutter and jamming.
But not the primitive and dumb radar of the ASM-N-2 Bat based on only several vacuum tubes.
Bat was used against Japanese shipping for the remainder of the war, but the success rate was mediocre at best.
While some ships were indeed severely damaged, the drawbacks of the primitive radar seeker also became obvious.
When attacking a ship near land (e.g., in port), Bat tended to home on all kinds of unwanted "targets", like docks, mountains, etc. Because of these problems, combat use of the Bat was relatively limited.
In the post-war years, the U.S. Navy tried to improve Bat's accuracy and reliability, but a live test series against an obsolete battleship in 1948 yielded very disappointing results. The latter were in part attributed to radar interference from other ships and aircraft.
Because that meant that the ASM-N-2 could be fooled by very simple radar countermeasures, Bat was removed from the inventory in the early 1950s.

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Re: V1s start being launched 2 weeks earlier

Post by T. A. Gardner » 16 Jan 2023 01:46

wm wrote:
15 Jan 2023 21:21
Yes, a skillful operator of an advanced (by ww2 standards) radar set could use those tricks to partially mitigate the effects of clutter and jamming.
But not the primitive and dumb radar of the ASM-N-2 Bat based on only several vacuum tubes.
Image

Far, far, in advance of any German missile guidance system...

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Re: V1s start being launched 2 weeks earlier

Post by wm » 18 Jan 2023 11:20

It wasn't that advanced.
At the front, there is an antenna and hardware to rotate it around its axis because conical scanning requires it.
The Germans knew and used conical scanning in their radars; even more, they were able to rotate the beam purely electronically, without any moving parts.

The rest is mainly hardware translating inputs from the radar to movements of the flight control surfaces. It wasn't easy, but nothing more complicated than contemporary autopilots.

In electronics, the capabilities of the principal belligerents (Germany, Britain, and the US) were very similar. There was nothing that the others couldn't have invented or replicated.
Even a German magnetron was possible, but it seems the Germans never wanted it that badly.

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Re: V1s start being launched 2 weeks earlier

Post by T. A. Gardner » 19 Jan 2023 16:58

wm wrote:
18 Jan 2023 11:20
It wasn't that advanced.
At the front, there is an antenna and hardware to rotate it around its axis because conical scanning requires it.
The Germans knew and used conical scanning in their radars; even more, they were able to rotate the beam purely electronically, without any moving parts.

The rest is mainly hardware translating inputs from the radar to movements of the flight control surfaces. It wasn't easy, but nothing more complicated than contemporary autopilots.

In electronics, the capabilities of the principal belligerents (Germany, Britain, and the US) were very similar. There was nothing that the others couldn't have invented or replicated.
Even a German magnetron was possible, but it seems the Germans never wanted it that badly.
Actually, the BAT glide bomb in terms of guidance was streets ahead of anything the Germans had in production or even design. The Germans didn't have a single 'fire and forget' guidance system available. All they had for guiding a glide bomb or ASM was the Kehl-Strassburg system. They were producing a wire guided variant for crap like the X-4 Ruhrstal missile, code named Düren-Detmold (FuG 208/238), and an alternate for Kehl-Strassburg using higher frequency radio (still AM), Kogge-Brigg (FuG 512/E230). There were a few other variants on the same theme being prototyped, but none of these were fire and forget.
All of the German systems were simple two-axis, all-or-nothing (on / off), manual, joystick controllers using optical line-of-sight and a simple MF, or HF AM radio links to the weapon being guided. The commands translated to up-down, or left-right, but only one or the other could be applied at a given time. Düren-Detmold used a 600 VDC using +/- or high-low voltage to accomplish the same left-right, up-down, all-or-nothing coarse control signals.

Bat on the other hand could be dropped on a detected target and would glide towards it searching for it with its on-board radar. Conical scan was used because it was relatively cheap and available as a means of guidance to the target. Use of a moving the antenna simplified scanning--the US could do electronic steering but that's more expensive and time consuming to build. After all, in BAT the use of the radar was a one-time thing.

After all, Robert M. Page, at the Naval Research Laboratory had already discovered how to do monopulse scanning in 1943, something the Germans didn't figure out, but the process was very expensive and labor intensive to produce working sets with.

Anyway, the SWOD Mk 2 radar homing system on BAT had its own transmitter on millimeter wave radar (S band 3 cm) and receiver that translated the return from the target into command signals for the servo motors to guide the bomb. A set of gyros ensured the bomb remained stable in flight. The theoretical range for a BAT to home on a target was 25 miles, but in service it was found that 12 to 15 was more practical. Altitude of release was based on range and the release speed was a maximum of 205 kts IAS.

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Re: V1s start being launched 2 weeks earlier

Post by wm » 21 Jan 2023 22:31

No, actually, the Bat was junk; anything, even the radar from another Bat, would disorient it, so the Germans didn't need it.
They had their own (slightly better) junk - the Fritz X.

A reliable seeker during ww2 wasn't possible. The best was the German wired control system - impervious to jamming, chaff, smoke screens, radar reflectors, and anything else.

I don't know if the Germans weren't aware of monopulse scanning, the technique known as simultaneous-lobing had been well known since 1928.

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Re: V1s start being launched 2 weeks earlier

Post by T. A. Gardner » 22 Jan 2023 00:27

wm wrote:
21 Jan 2023 22:31
No, actually, the Bat was junk; anything, even the radar from another Bat, would disorient it, so the Germans didn't need it.
They had their own (slightly better) junk - the Fritz X.

A reliable seeker during ww2 wasn't possible. The best was the German wired control system - impervious to jamming, chaff, smoke screens, radar reflectors, and anything else.

I don't know if the Germans weren't aware of monopulse scanning, the technique known as simultaneous-lobing had been well known since 1928.
Wrong! Düren-Detmold had serious limitations, if it would work at all. The control wires were 22 gage spring steel, and when used from an aerial platform had two serious and unfixable problems. The first was tension on the wires. If the wire became to tensioned, it would snap and control was lost. The alternative to tension was droop in the wire due to gravity. When you are talking about kilometers of wire between the firing aircraft and the weapon, there is either going to be tension on the wire or it will droop due to gravity.
Either way, this creates a second problem. You have 5 to 10 kg of wire trailing the missile or bomb acting as a bob weight on it. If the weight is going between tension and droop, along with an offset, it will create issues in stability.
Worse, you have as much as several miles of wire leftover after the flight. This is still attached to the launching aircraft and likely will entangle it. While 22 ga wire is no threat to flight, it could still become entangled in propellers, on radio antennas, or elsewhere causing issues.

Wire guidance was stupid. It is also still affected by smoke screens (the system is still optical), flares (distracting / blind the operator to position of his missile / bomb), clouds, and the like.

Bat proved at least as accurate as Fritz X or Hs 239 in service and would have gotten better with continued use. The German Düren-Detmold system was the worst possible choice. Kehl-Strassburg and the later Kogge-Brigg systems were on par with similar Allied joystick / radio combinations, if more vulnerable to jamming due to use of lower frequency AM radio rather than UHF FM like the Allies used.

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Re: V1s start being launched 2 weeks earlier

Post by kfbr392 » 22 Jan 2023 07:55

Fascinating discussion.

Terry, my understanding is also that sufficiently rapid unspooling of the wires at launch was the/an issue that prevented introduction of wire guided Hs 293 before 1945.

I found this quote:
„ Ferngelenkte Körper.
[…]
Drahtspulen: Abspulgeschwindigkeit von 2O5 m/sec jetzt erreicht. Im Flugbetrieb ca. 17O m/sec auftretend. Abwurferprobung kann somit beginnen. “

source: KTB Chef Technische Luftrüstung, February 1945
Although, Hs 293 is not mentioned; it could (and likely does) refer to SAMs.

Translation:
„Remotely controlled airframes:
[…]
Wire spools: Unwinding speed of 2O5 m/sec now achieved. Requirement in flight approx. 17O m/sec occuring. Drop testing can thus begin. "
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Re: V1s start being launched 2 weeks earlier

Post by T. A. Gardner » 22 Jan 2023 18:23

kfbr392 wrote:
22 Jan 2023 07:55
Fascinating discussion.

Terry, my understanding is also that sufficiently rapid unspooling of the wires at launch was the/an issue that prevented introduction of wire guided Hs 293 before 1945.

I found this quote:
„ Ferngelenkte Körper.
[…]
Drahtspulen: Abspulgeschwindigkeit von 2O5 m/sec jetzt erreicht. Im Flugbetrieb ca. 17O m/sec auftretend. Abwurferprobung kann somit beginnen. “

source: KTB Chef Technische Luftrüstung, February 1945
Although, Hs 293 is not mentioned; it could (and likely does) refer to SAMs.

Translation:
„Remotely controlled airframes:
[…]
Wire spools: Unwinding speed of 2O5 m/sec now achieved. Requirement in flight approx. 17O m/sec occuring. Drop testing can thus begin. "
That's part of the tension - slack problem that can't be solved. The spool out of the wire requires it be under tension to 'tug' it out of the spool. If there is no tension, there is no wire being spooled out. Then if tension returns, it could well snap the wire rather than restart spooling. Additionally, if you've ever tried unspooling thread, rope, wire, whatever off a spool, it inevitably hangs up at some point and stops coming off smoothly.

When the missile launches it will accelerate and the wire has to spool off at an increasing rate or tension will increase on the wire instead. If that goes beyond the tensile strength of the wire or the attachment points on the plane, it will break and control will be lost.

Gravity alone dictates that the wire will droop under its own weight several hundred feet as the wire spools out to several kilometers. That too is a huge problem to resolve.

Spooling at 206 m/sec works out to about 740 kph or 450 mph. Since both the X-4 and Hs 293 exceed that speed in flight, that too is going to be a problem...

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