R4M rocket accuracy

[Juanpunto]

I was playing around with the R4M rockets and I noticed how they just seemed to go around where I was aiming rather than towards it, so I did some testing.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

And yeap, the rockets seem to have donut-shaped spread (toroidal if you want to be technical), with an external and internal diameter around 16m and 7m respectively at 200m. This is very surprising, since this 1957 US air force document states on page 52 that the spread of an 11-rocket burst, as mounted on an aircraft at 200m was around 4m in diameter, and goes as far as to call it a considerable improvement over any previous German rocket. In that same document their combat range is stated as 600m, which in game would give you a gigantic 21m deadzone around where you are aiming and a 48m outer diameter, and that's the lower end of the ranges that can be found, some sources claiming up to 1000m.

 

Now, maybe there is something I am missing and they are correctly modelled in-game, in which case I would love to know.

[Avimimus]

It is worth noting that these rockets are aerodynamically stabilised. One can't use a simple linear projection. Most of the initial dispersion happens before the rocket accelerates, but the rocket trajectories then tend to become more stable over time:

 

IRL rockets fired from a helicopter (slow moving and passing through rotor downwash) will have several times the dispersion of the same model of rocket fired from a fixed wing platform flying at 500 km/h.

 

That said - some of the rockets should be finding their way back towards the centre (the toroidal shape seems unlikely to me).

[Holtzauge]

On 1/21/2024 at 7:52 PM, Juanpunto said:

I was playing around with the R4M rockets and I noticed how they just seemed to go around where I was aiming rather than towards it, so I did some testing.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

And yeap, the rockets seem to have donut-shaped spread (toroidal if you want to be technical), with an external and internal diameter around 16m and 7m respectively at 200m. This is very surprising, since this 1957 US air force document states on page 52 that the spread of an 11-rocket burst, as mounted on an aircraft at 200m was around 4m in diameter, and goes as far as to call it a considerable improvement over any previous German rocket. In that same document their combat range is stated as 600m, which in game would give you a gigantic 21m deadzone around where you are aiming and a 48m outer diameter, and that's the lower end of the ranges that can be found, some sources claiming up to 1000m.

 

Now, maybe there is something I am missing and they are correctly modelled in-game, in which case I would love to know.

 

I must say that that was a very thorough and well presented "complaint" @Juanpunto. And thanks for the link to that document. A lot of good info there not only on rockets but on cannon armament as well.

 

@Avimimus: About the pattern: In the linked report (page 52), it states that the 11 rocket salvo that hit within 3.8 x 4.1 m at 200m, the rockets were fired in a sequence so as not to disturb each other's fin deployment. And given this information, it's far more likely that the resulting pattern within the 3.8 x 4.1 m was more of a normal distribution meaning that most rockets would hit close to the middle with a few outliers on the edges.

 

So the  toroidal pattern we see above seems more like a game artifact to me. Or else what would cause it?

 

Anyway, a well argued and well researched post @Juanpunto.

 

And like you, I am most interesting to see what the developers have to say about this.

[Stonehouse]

Unfortunately, this info only seems available via the web archive and is in German, but it is still interesting reading via google translate. Pics and pdf links don't seem to work but perhaps they could be tracked down particularly if a person fluent in German was doing the tracking down. 

 

R4M Rocket Hurricane

[Holtzauge]

2 hours ago, Stonehouse said:

Unfortunately, this info only seems available via the web archive and is in German, but it is still interesting reading via google translate. Pics and pdf links don't seem to work but perhaps they could be tracked down particularly if a person fluent in German was doing the tracking down. 

 

R4M Rocket Hurricane

 

Absolutely. The more info the merrier. And I do happen to have some of those documents like the Bedienungsvorschrift and some technical data from that site but I never did see any dispersion data like @Juanpunto posted in the OP.

 

And this really begs the question of why the in-game dispersion is (as far as I can understand from the testing done) roughly toroidal-shaped with a 7 m hole in the middle and an outer diameter of 16 m at 200 m range, while the document states only about 4 by 4 m at that range.

 

And that's a huge difference. And which is why I share @Juanpunto's question if this is based on some actual data or just a best guess that was done at the time the R4M model was introduced in-game.

[Stonehouse]

There is dispersion information in the linked post - I assume this comes from the source references on the links which sadly don't work anymore. You may have to scroll through the different subtopics to see the info. Note this is using translate so the English is a bit cumbersome and word choice not quite correct eg "reduced to 770m" in the second spoiler probably should be "improved to 770m". Other sites (unfortunately without reference docs or substantiation) also state that the inflight trajectory was sufficiently close to the mk108 round that the Revi sight could be used without change and that each "fighter would carry up to 24 rockets, to be fired in four salvos, saturating a box to ensure a hit.". This last quote is from the Smithsonian. Anyway, the point I was getting at is regardless of the size of the dispersion box the in-game scatter pattern (leaving the hole in the circular pattern) would seem to be not right based on the linked site and other sites. Everything refers to an approximately square pattern in the target area not toroidal. I imagine some of the references in the post from www.germanluftwaffe.com if they could be found may give the source info needed to get a change considered. Particularly the operating instructions pdf or the operational review documents.

 

Spoiler

Only 0.8 seconds after firing, the R4/M had reached its top speed, which was 635 m/s for the Focke Wulf Fw 190 including aircraft speed. In the case of the tubular grate, which consisted of 13 pieces of 600 mm long cardboard pipes, each with a wall thickness of 2.5 mm, the empty grate was automatically thrown off after the closure of nos. 4 and 9. Here, the fastening struts of the 45 kg (incl. assembly) grate were located in the slotted closure tubes. The dimension of 65 mm specified for the rail grating from rocket axle to rocket axle has been reduced to 60 mm for the tube grating. Throw-off arrangements were also being developed for the rail grid, as the aircraft suffered a loss of speed of about 18 km/h. Of course, only 6 or 7 rockets could be fired per area by means of a dial-up circuit. Firing tests showed 50% hits at a distance of 500 m in a square of 16 m edge length.

 

and later it talks about later advances made in rails 

 

Spoiler

The rail grating and the tubular grating for 13 rockets next to each other did not have any special features. They also had the disadvantage of a not inconsiderable air resistance (speed loss of about 18 km/h). Instead of these, a fairly good suggestion was the so-called honeycomb, which could either be permanently installed in the aircraft, or in which the missiles were concentrically stored in a jettisonable, aerodynamically high-quality, teardrop-shaped body. The cap and tail of this body should be thrown off immediately before the fight. The production: the honeycomb was intended in its final solution from cardboard tubes, among other things. It had been considered to create a cardboard sleeve for the packaging of the rockets, which could also have served as a launch tube and could also have been used in grates of suitable construction. An objective comparison to determine the influence of the various launchers on the accuracy of the missiles was still lacking at the end of the war.

The company Rh. B. also adjusted a rail grid in such a way that 24 rockets fired head-on at the enemy from a distance of 1230 m resulted in a hit area of 320 m2. For the same hit area, the distance has been reduced to 770 m when attacking from behind. Another salvo shot attempt from a distance of 300 m resulted in a hit area of 2.9 X 4.4 m.

 

Edited December 28, 2024 by Stonehouse

[Holtzauge]

13 hours ago, Stonehouse said:

There is dispersion information in the linked post - I assume this comes from the source references on the links which sadly don't work anymore. You may have to scroll through the different subtopics to see the info. Note this is using translate so the English is a bit cumbersome and word choice not quite correct eg "reduced to 770m" in the second spoiler probably should be "improved to 770m". Other sites (unfortunately without reference docs or substantiation) also state that the inflight trajectory was sufficiently close to the mk103 round that the Revi sight could be used without change and that each "fighter would carry up to 24 rockets, to be fired in four salvos, saturating a box to ensure a hit.". This last quote is from the Smithsonian. Anyway, the point I was getting at is regardless of the size of the dispersion box the in-game scatter pattern (leaving the hole in the circular pattern) would seem to be not right based on the linked site and other sites. Everything refers to an approximately square pattern in the target area not toroidal. I imagine some of the references in the post from www.germanluftwaffe.com if they could be found may give the source info needed to get a change considered. Particularly the operating instructions pdf or the operational review documents.

 

  Hide contents

Only 0.8 seconds after firing, the R4/M had reached its top speed, which was 635 m/s for the Focke Wulf Fw 190 including aircraft speed. In the case of the tubular grate, which consisted of 13 pieces of 600 mm long cardboard pipes, each with a wall thickness of 2.5 mm, the empty grate was automatically thrown off after the closure of nos. 4 and 9. Here, the fastening struts of the 45 kg (incl. assembly) grate were located in the slotted closure tubes. The dimension of 65 mm specified for the rail grating from rocket axle to rocket axle has been reduced to 60 mm for the tube grating. Throw-off arrangements were also being developed for the rail grid, as the aircraft suffered a loss of speed of about 18 km/h. Of course, only 6 or 7 rockets could be fired per area by means of a dial-up circuit. Firing tests showed 50% hits at a distance of 500 m in a square of 16 m edge length.

 

and later it talks about later advances made in rails 

 

  Hide contents

The rail grating and the tubular grating for 13 rockets next to each other did not have any special features. They also had the disadvantage of a not inconsiderable air resistance (speed loss of about 18 km/h). Instead of these, a fairly good suggestion was the so-called honeycomb, which could either be permanently installed in the aircraft, or in which the missiles were concentrically stored in a jettisonable, aerodynamically high-quality, teardrop-shaped body. The cap and tail of this body should be thrown off immediately before the fight. The production: the honeycomb was intended in its final solution from cardboard tubes, among other things. It had been considered to create a cardboard sleeve for the packaging of the rockets, which could also have served as a launch tube and could also have been used in grates of suitable construction. An objective comparison to determine the influence of the various launchers on the accuracy of the missiles was still lacking at the end of the war.

The company Rh. B. also adjusted a rail grid in such a way that 24 rockets fired head-on at the enemy from a distance of 1230 m resulted in a hit area of 320 m2. For the same hit area, the distance has been reduced to 770 m when attacking from behind. Another salvo shot attempt from a distance of 300 m resulted in a hit area of 2.9 X 4.4 m.

 

 

OK, thanks for that information. That was very informative.

I noticed that the tight box pattern mentioned in the OP at 200 m now has a source saying about the same for 300 m: “Another salvo shot attempt from a distance of 300 m resulted in a hit area of 2.9 X 4.4 m.”

In addition, at the risk of repeating myself: Sure all R4M rockets hit within the box pattern, but I would not take this to mean that they were evenly distributed in that box. As I said before, physics/ballistics would rather dictate that the pattern was normal distributed with the box, not evenly distributed. So I would think it would be a mistake if any in-gamed update (of course barring any exact knowledge as to how the rockets actually distributed) from the current toroidal distribution went down that path.

Finally, this quote seems strange to me:  “the inflight trajectory was sufficiently close to the mk103 round that the Revi sight could be used without change”

Shouldn’t it be that the trajectory of the R4M was close to the Mk 108, not the Mk 103? Was the R4M trajectory really that flat? Because if you add the R4M’s purported 635 m/s top speed with the fins’ drag I would expect the trajectory to be closer to a Mk 108 round.

 

Edited December 28, 2024 by Holtzauge

[Stonehouse]

1 hour ago, Holtzauge said:

“the inflight trajectory was sufficiently close to the mk103 round

Apologies...my typo, I intended to write mk108. Previous post corrected.

Edited December 28, 2024 by Stonehouse

[Holtzauge]

34 minutes ago, Stonehouse said:

Apologies...my typo, I intended to write mk108. Previous post corrected.

 

No problem, I suspected it was the Mk 108 but just wanted to make sure. 

 

Will be interesting to see if/when this is fixed. 

 

On a tangent: The R4M seems like the perfect weapon for the Me 262: No need to loiter long at speeds close to the bomber's to get sufficient firing time with the cannons, but just a quick high speed approach and then let loose the rockets with an almost guaranteed kill every time and then still have the speed to evade the escorts.

[AEthelraedUnraed]

On 12/27/2024 at 10:18 PM, Stonehouse said:

Note this is using translate so the English is a bit cumbersome and word choice not quite correct eg "reduced to 770m" in the second spoiler probably should be "improved to 770m".

No "reduced" is the proper translation here. What I think they mean is that in a frontal attack, since the enemy is moving at you at a much greater relative velocity, you need to fire a bit earlier to have the rockets hit the target at the same range. If you attack from behind, by the time the rockets have reached the distance they'd have a 320m2 hit area, the enemy has already flown a bit further away so you need to fire a bit closer to compensate for that.

 

Now if we assume linearity (which of course is wrong since the rocket velocity isn't constant across distance), we find that against a stationary target the 320m2 hit area distance equals (1230 + 770)/2 = 1000m. Which is so perfect a range that I think they did the same linearisation.

 

If we assume the rockets follow a linear path as well, we get a hit area of 320*600/1000 = 192m2 at 600m.

EDIT: eh, sorry, just had a brainfart. Area, so that's squared. 320 at 1000 means 320*(600/1000)^2 = 115m2 at 600m.

Edited December 31, 2024 by AEthelraedUnraed