HVAR recoil

[Random]

Indeed not, was thinking about the Huey pods when I wrote that, my bad.

 

Even that kind of pod is open at the rear.

 

I'd really like to see the recoil removed from the rockets in DCS. I love ground attack and it ruins it for me when the mustang swings wildly if you dont fire off 2 at once!

[Oydoron]

Take a hair dryer. It will be a rocket. Then you can make a paper tube as a launcher or just place a bended sheet of cardboard on the table as a launcher. Then turn on your hair dryer (sorry - a rocket!) and move it forward from the launcher. Notice, where the cardboard launcher flies - forward or back... enjoy.

 

Effect, of course, is dependable of the area exposed to the jet stream.

 

Ah, launch tubes

 

What about the moment when this stream hits to the wing and launcher? And what about the video I posted in #18? At least 2 tonns of jeep rocks very well.

 

These have tubes

 

But It's not HVAR on the Jeep - less caliber - but the rails are bending.

 

And tubes here too. But the P-51D has no tubes.

 

Small launchers, like in the Mustang will have less recoil effect, so what is strange if a heavy rocket has the same recoil as a 46 g bullet?

 

Is the recoil of a single 46g bullet even noticeable in the mustang?

[msalama]

Even that kind of pod is open at the rear.

 

...and yet, has some friction / stiction between the pod and the rocket.

[Captain Orso]

From whose part, mine? Nah, just interested in the phenomenon, that's all.

 

If you argue that the recoil must be true because ED put it in, but cannot produce evidence for the recoil other than that ED put the recoil in (that is a circular argument), then you are apologizing for ED for putting the recoil in; that is apologetics.

 

Please don't make up an excuse for the recoil. Either you have some evidence for it or you don't.

[Captain Orso]

I think the statement that "rockets have no recoil" was used to compare to conventional cannon with the same or comparable caliber.

 

The statement is "rockets have no recoil" not 'rockets have less recoil'. Why do you refuse to take the word of the authors the official manual?

 

But if any part of the launcher interacts with a high-speed jet stream, it will encounter dynamic pressure action of it - for short time but it will. The impulse of this interaction depends on the rocket thrust and the area and the lenght of the launcher.

Large block of tubes like modern Russian (for S-5 and S-8) and USA Hydra will definetely encounter sufficient interaction either the jet nozzle is inside the tube or just in front of it.

 

Small launchers, like in the Mustang will have less recoil effect, so what is strange if a heavy rocket has the same recoil as a 46 g bullet?

 

So, since everybody is making their wish-statements as if they were facts, here's mine:

 

The bolts which hold the rockets in place before they are fired are so small and the jet of the firing propellant so greatly offset from the bolts that the force exerted on them is so minimal that its affect on the airframe of the P-51D is not measurable.

 

I have show evidence to support my statement, please show evidence to support yours.

[NineLine]

The statement is "rockets have no recoil" not 'rockets have less recoil'. Why do you refuse to take the word of the authors the official manual?

 

 

 

So, since everybody is making their wish-statements as if they were facts, here's mine:

 

The bolts which hold the rockets in place before they are fired are so small and the jet of the firing propellant so greatly offset from the bolts that the force exerted on them is so minimal that its affect on the airframe of the P-51D is not measurable.

 

I have show evidence to support my statement, please show evidence to support yours.

 

I think some of the issue is using the word 'recoil' I dont know if this would still be considered recoil, dont know if there is a special term for the moment a rocket is ignited and the time before the shear cables were broken. One would have to believe these cables that held the rockets in place were fairly strong to withstands even normal flight. So I would image it took some force to break them.

 

Would be a good question for a WWII pilot with experience with these things, in my mind there would have to be a moment of something when they were fired, how much I have no clue, or if it was truly noticeable...

[Destroyer37]

Just looking at this video there does seem to be several things going on here. First off I know its not a mustang...

 

It looks like the first effect is an increase in speed from the rocket motors firing, followed by a reduction in parasitic drag as the rocket leaves the airframe. This asymmetrical drag although momentary may force a "recoil-esque" feel in the controls. That all being said (not an expert here) I do think the effects of firing the rockets on the Mustang may be a bit overstated.

Edited July 15, 2015 by Destroyer37

[Captain Orso]

I think some of the issue is using the word 'recoil' I dont know if this would still be considered recoil, dont know if there is a special term for the moment a rocket is ignited and the time before the shear cables were broken. One would have to believe these cables that held the rockets in place were fairly strong to withstands even normal flight. So I would image it took some force to break them.

 

Would be a good question for a WWII pilot with experience with these things, in my mind there would have to be a moment of something when they were fired, how much I have no clue, or if it was truly noticeable...

 

The manual describes a "safety-wire latch" on the "aft launcher" which is "sheared" when the rocket is fired.

 

If the "recoil" we are seeing when firing a single rocket is caused by the force necessary to shear the safety-wire latch that would mean that the rocket engine is igniting and remaining attached to the launchers while pulling the airframe about 5 degrees off center before the safety-wire latch breaks and releases the rocket, which would mean that the rocket will always launch about 5 degrees offset from where the pilot was aiming.

 

Firing a rocket at 1000' from the target, causing a 5° yaw to one side would cause the rocket to hit 87.5 feet to the side of the point of aim, and the pilot would never hit a target.

[NineLine]

The manual describes a "safety-wire latch" on the "aft launcher" which is "sheared" when the rocket is fired.

 

If the "recoil" we are seeing when firing a single rocket is caused by the force necessary to shear the safety-wire latch that would mean that the rocket engine is igniting and remaining attached to the launchers while pulling the airframe about 5 degrees off center before the safety-wire latch breaks and releases the rocket, which would mean that the rocket will always launch about 5 degrees offset from where the pilot was aiming.

 

Firing a rocket at 1000' from the target, causing a 5° yaw to one side would cause the rocket to hit 87.5 feet to the side of the point of aim, and the pilot would never hit a target.

 

I dont doubt that its a little extreme right now, but the manual for the training rounds also points out that the pilot needs to fly correctly to lesses the dispersal of the rockets... whatever that might mean we probably wont know without talking to a P-51 pilot that has fired rockets.

[msalama]

Please don't make up an excuse for the recoil.

 

"Excuse"? The hell is wrong with you? All I've been doing is offering some counterarguments just for the sake of discussion. I've no idea whether the current implementation is right or wrong, I'm just interested in the friction/stiction phenomena and how it may - or may not - affect the rockets we have. That OK to you? Or if not, why don't you just go and apply for a ruddy restraining order banning me from this thread or something?

 

Jeez, some people...

[NineLine]

Lets keep the discussion open guys, not need to pick at anyones comments, I honestly feel like this wont be answered by anyone short of someone with experience from the 40's...

[Tucano_uy]

We don't see this amount of force (let's not call it recoil as it is not, but the gases pushing on the wing) even when launching a Maverick from the Warthog. At some time the effect was introduced, I don't know why, even if it is not described in the manuals or observed on real life videos. The jet of gases would pass mostly under the wing anyways. The effect seems to be really exaggerated, I don't know why ED stubbornly decided to keep it this way. There's more evidence against than supporting, the things the way they are now.

[NineLine]

We don't see this amount of force (let's not call it recoil as it is not, but the gases pushing on the wing) even when launching a Maverick from the Warthog. At some time the effect was introduced, I don't know why, even if it is not described in the manuals or observed on real life videos. The jet of gases would pass mostly under the wing anyways. The effect seems to be really exaggerated, I don't know why ED stubbornly decided to keep it this way. There's more evidence against than supporting, the things the way they are now.

 

Problem is there is no real conclusive evidence for or against. Even the evidence against is light, I mean the manual states there is no recoil... of course, but it doesnt mean there isnt some other effect experienced by the pilot. Accusing ED of being stubborn wont get you anywhere though... Yo-Yo agrees that a pilot from that time would be the best reference unless there are some tests or reports on the subject.

Edited July 15, 2015 by NineLine

[Yo-Yo]

We don't see this amount of force (let's not call it recoil as it is not, but the gases pushing on the wing) even when launching a Maverick from the Warthog. At some time the effect was introduced, I don't know why, even if it is not described in the manuals or observed on real life videos. The jet of gases would pass mostly under the wing anyways. The effect seems to be really exaggerated, I don't know why ED stubbornly decided to keep it this way. There's more evidence against than supporting, the things the way they are now.

 

We only want to have the most accurate evidencies about HVAR recoil. Not Maverick, not Hydra or S-8 or even S-13. Possibly the effect in DCS is stronger than it could be, possibly it is right.

 

The only thing we can not do, is to change something after user's wishes, suggestions and imaginations.

The history of simulators knows some examples that following the community wishes caused weird changes in physics having no grounds to exist.

[Tucano_uy]

I didn't mean to use the word "stubbornly" in an insulting way. I respect a lot the work of the people that created this sim.

 

I am still convinced that there's more evidence against than for. Why would a manual specifically state that there's no recoil and ignore any other significant force or effect in the flight?

 

Yes, a pilot that fired HVARs would be great, need to hurry up though, they're not getting younger. How are the developers going to create sims in 50 years time?

 

Let's find a video of any WWII bird shooting rockets and yawing like crazy and then that's it, dilemma put to rest. So far all the videos I have seen show something else.

Edited July 15, 2015 by Tucano_uy

[Captain Orso]

BTW the yawing motion is definitely recoil:

Edited July 15, 2015 by Captain Orso

[Captain Orso]

"Excuse"? The hell is wrong with you? All I've been doing is offering some counterarguments just for the sake of discussion. I've no idea whether the current implementation is right or wrong, I'm just interested in the friction/stiction phenomena and how it may - or may not - affect the rockets we have. That OK to you? Or if not, why don't you just go and apply for a ruddy restraining order banning me from this thread or something?

 

Jeez, some people...

 

My dearest msalama, "offering some counterarguments just for the sake of discussion"; the more common term for this is, "just for the sake of argument".

 

I am completely open to any argument based on evidence, but but not "just for the sake of discussion". That will get us nowhere.

 

I believe the video I posted above documents that the yawing motion represents recoil, because the wing on the firing side is being pushed back. This precludes the yawing motion is being caused be the rocket 'pulling' on the airframe.

[NineLine]

 

I believe the video I posted above documents that the yawing motion represents recoil, because the wing on the firing side is being pushed back. This precludes the yawing motion is being caused be the rocket 'pulling' on the airframe.

 

I wonder if it could be that the aerodynamics of the wing is 'disturbed' enough on firing of the rocket to cause the yawing shown. The thrust of the rocket breaking up the flow over the wing just enough to have an effect? That's above my head though, so I'll leave that to Yo-Yo. :pilotfly:

[Holbeach]

Lets keep the discussion open guys, not need to pick at anyones comments, I honestly feel like this wont be answered by anyone short of someone with experience from the 40's...

 

Of all the imaginative denial posts in this thread, this is one of my favorites.

 

Dig up a 95 year old Mustang pilot who has fired HVAR rockets and get him to substantiate the effect in a computer game.

 

Well you can actually use a younger 75 year old Sabre pilot, because it has the same recoil effect, in game when firing HVAR.

 

C'mon boys just read the manual.

 

Rockets have no recoil.

 

 

..

[NineLine]

Of all the imaginative denial posts in this thread, this is one of my favorites.

 

So I ask people not to pick apart peoples comments and you decide that is a good post to pick apart? You don't have to agree with me... but if you read my comments through out, I wasn't denying anything at all, I don't doubt that its possible the effect is possible wrong or too strong, but an engineer who builds FMs for a living thinks there must be something, I am not going to argue with him based available info.

[Yo-Yo]

Of all the imaginative denial posts in this thread, this is one of my favorites.

 

Dig up a 95 year old Mustang pilot who has fired HVAR rockets and get him to substantiate the effect in a computer game.

 

Well you can actually use a younger 75 year old Sabre pilot, because it has the same recoil effect, in game when firing HVAR.

 

C'mon boys just read the manual.

 

Rockets have no recoil.

 

 

..

 

No recoil. absolutely, the car just plays itself - it's so happy to be a launcher, a battle horse...

 

But it's a tube launcher, I see...

Edited July 15, 2015 by Yo-Yo

[Captain Orso]

I don't think the exhaust gassed of the rocket will actually touch the wings unless one were to roll into them, which would be a very extreme roll while firing rockets.

 

The rocket exhaust could hypothetically change the lift of the wing for as long as it is present, which would only be the fraction of a second. Higher pressure under the wing would cause more lift locally for that part of a second it exists. That would mean that the wing on the firing side would be pushed upward, which would cause a slight involuntary roll away from the firing side. That is however not what we are seeing.

 

Arguing against that is that the gas jet is very narrow, so only a fraction of the wingspan. It would also mean that if one were to fire all ten rockets in train the affect would be ten fold. The affect would be to lift the wings and cause the airframe to pitch upward. This is also not seen, nor is anything similar to be found in the videos Destroyer37 posted nor any others I've ever seen.

[Exorcet]

I don't think the exhaust gassed of the rocket will actually touch the wings unless one were to roll into them, which would be a very extreme roll while firing rockets.

 

The rocket exhaust could hypothetically change the lift of the wing for as long as it is present, which would only be the fraction of a second. Higher pressure under the wing would cause more lift locally for that part of a second it exists. That would mean that the wing on the firing side would be pushed upward, which would cause a slight involuntary roll away from the firing side. That is however not what we are seeing.

 

Arguing against that is that the gas jet is very narrow, so only a fraction of the wingspan. It would also mean that if one were to fire all ten rockets in train the affect would be ten fold. The affect would be to lift the wings and cause the airframe to pitch upward. This is also not seen, nor is anything similar to be found in the videos Destroyer37 posted nor any others I've ever seen.

 

 

It could be instead that the exhaust doesn't directly hit the wing, but causes flow to accelerate under the wing causing a loss of lift. It could even be a combination of both that results in less lift loss/gain than expected.

 

If the wing is effected, it probably gains a less ideal spanwise lift distribution which would increase the drag on the firing wing, which could lead to something like recoil.

 

My personal reaction is to say that DCS is overdoing the recoil, if it exists, but I wouldn't rule it out without a direct test. Jumping into a P-51 and firing HVAR's is probably out of the question, but I wonder if there would be merit to simulating a HVAR launch in great detail.

[Captain Orso]

No recoil. absolutely, the car just plays itself - it's so happy to be a launcher, a battle horse...

 

But it's a tube launcher, I see...

 

Yes, the firing of those rockets at 69 seconds+ is definitely rocking the truck. If you look at 25 seconds you see another truck firing a different type of rocket and the truck is not moving at all.

 

The rockets being fired at 69 sec seem to be much larger and are being fired from tubes.

 

The rockets being fired at 25 secs may be smaller and appear to be being fired from a rack, similar to how the HVAR are carried and fired.

 

Both trucks appear to be about the same size.

 

From this I would speculate that:

1. the fact that the rockets are being firing from tubes is exacerbating the reaction of the truck.

2. the change in weight of the payload of the truck suddenly changing is also causing the truck to be jostled.

 

From the size of the rockets at 69 secs I would also speculate that they weight far more than an HVAR. They definitely have a much larger diameter than an HVAR. The truck probably weighs only about 1/10 of what the P-51D weights.

 

I believe that viewing and comparing both sections of this video only strengthen my arguments :music_whistling:

[NineLine]

If you look at 25 seconds you see another truck firing a different type of rocket and the truck is not moving at all.

 

Small nitpick, but that truck is moving, not much but it is, the smoke masks it some, but you can see it better on the second shot... not a big deal, but figured I would mention it ;)

 

Also if it was mostly weight causing the rocking, wouldnt the truck rock opposite as the weight is transferred to the end of the tube, then released?

Edited July 15, 2015 by NineLine