Rocket artillery

[ChernayaAkula]

Didn't find a thread for these, so here goes. Kicking things off is a vehicle worthy of a website dedicated to what-if modelling.

What if I took my trusty Zil 131 truck and put these two B8M1 80mm rocket launchers on the truck bed? 

[Arc3371]

I think you will find this link interesting

http://oklop2.tripod.com/made_in_war/war1.htm

From the site above




Not rocket artillery but still....

[NARSES2]

That Zil with the rocket pods makes you realise just how big they are  

[MAD]

Nothing wrong with 'improvise, adapt and over come'!
A tank is always a tank to an infantrymen - wether its a 1940's T-34 in 2010!
Or an improvised aircraft 57mm air-to-ground rocket mounted on the back of some old banged out truck - it still rains fire on your poor donkey!

M.A.D

[Weaver]

If I read the accompanying text right, this little number is four K-13 (AA2-Atoll) rocket motors with a 250kg bomb strapped to the front of them....



Not only do I not want to be in front of that, but I don't want to be behind it either, or, indeed anywhere within a mile of it when it's fired..... what do you think the chances are of those four mass-produced, unmatched rocket motors all firing at the same time with exactly the same thrust? 

[PR19_Kit]

And look at the amount of offset on those four boilerplate fins! That thing's going to spin like crazy when it gets moving, presumably for 'stability'. [The word 'stability' here is used in its widest possible sense.........]

[Steel Penguin]

that just screams "light the blue touch paper and run"  or more likely get a poor private to do so 

[Weaver]

I'd want a blue touch-paper so long that the war would be over by the time it got to the rocket......

[Silver Fox]

It should actually be pretty tolerant of mismatched thrust and pretty stable. You see, the fins aren't fixed, they're hinged and gyro-stabilized like a Sidewinder or Atoll missile. Wouldn't be all that accurate... should be a pretty wild flight though! Something that big wandering through the sky like a Sidewinder would be spectacular. 

[Weaver]

It should actually be pretty tolerant of mismatched thrust and pretty stable. You see, the fins aren't fixed, they're hinged and gyro-stabilized like a Sidewinder or Atoll missile. Wouldn't be all that accurate... should be a pretty wild flight though! Something that big wandering through the sky like a Sidewinder would be spectacular.  

That's what I thought at first, but if you look at them:

a) there are no signs of the usual rolleron wheels in the control flaps,

b) at least one of them is pointing upwards, which implies that it's been fixed in position: the usual freely-hinged flap would fall downwards at rest.


In any case, the Sidewinder rollerons don't actually make the missile fly straight or follow it's characteristic "sidewinding" path. All they do is control the roll rate: the "sidewinding" iwas caused by the simplified guidance logic in the early versions which caused them to constantly over-steer.

[rickshaw]

That is rather reminiscent of the Japanese bomb rockets used towards the end of WWII.  Big powder rockets attached to small bombs and fired from fairly primitive troughs.   They worked reasonably well but weren't intended to be super accurate and neither is this, I suspect.  The canted fins impart spin and that would more than likely be sufficient to offset any imbalance in the burning of the separate rocket motors.  The CEP might be several tens of metres but its not intended to be anything other than a general bombardment weapon in all likelihood.

[NARSES2]

The CEP might be several tens of metres but its not intended to be anything other than a general bombardment weapon in all likelihood.

Can I ask a naive question ? In any weapon like that how can you control anything with even a hint of accuracy ? I would have thought all you could do would be alter the range by changing the elevation of the launch rail and the bearing by pointing it in a different direction ? Everything else is fixed or am I missing something ?

[rickshaw]

The CEP might be several tens of metres but its not intended to be anything other than a general bombardment weapon in all likelihood.

Can I ask a naive question ? In any weapon like that how can you control anything with even a hint of accuracy ? I would have thought all you could do would be alter the range by changing the elevation of the launch rail and the bearing by pointing it in a different direction ? Everything else is fixed or am I missing something ?

Basically you're correct.  However, remember spinning the rocket creates a gyroscopic effect with the result that it tends to fly in a straight line.  "Tends" because of course it is affected by external factors, such as winds as is any projectile.   Remember, this gyroscopic effect is why rifling was introduced in firearms.

This sort of rocket isn't wildly inaccurate, just relatively.   By changing the elevation,  as you mention you can alter the range by altering the trajectory - make it fly higher, the range shortens (if above approximately 45%).   You'd have to do fairly extensive testing to work out the ranges each elevation change produces.   On a windless day, you'd expect it to fly in a reasonably straight line (they are never perfect) because the spinning would keep it pointing the way you pointed it.   Remember, this is almost exactly how a Katayusha or Nebelwerfer rocket works and while not highly accurate, they could usually get them to within a hundred metres or less of their target.

[Weaver]

The CEP might be several tens of metres but its not intended to be anything other than a general bombardment weapon in all likelihood.

Can I ask a naive question ? In any weapon like that how can you control anything with even a hint of accuracy ? I would have thought all you could do would be alter the range by changing the elevation of the launch rail and the bearing by pointing it in a different direction ? Everything else is fixed or am I missing something ?

That's pretty much the limit of what you can do with simple rocket artillery, whether improvised or not. They are significantly less accurate than tube artillery, their principle advantage being saturation, i.e. they can land a large number of rounds in a short time with minimal warning, which is why they are particularly favoured for chemical weapons amd submunitions. Two thing you do have to know for any kind of accuracy are the flight characteristics of the airframe and the thrust/time characteristics of the rocket motor, which are derived from theory and modified by firing tests. Some of this data was probably available for the aircraft rocket pods, but somehow I doubt whether any serious firing tests were conducted on the 4 x K13 + FAB combination.

More sophisticated rocket artillery can refine the flight profile of the rocket by using variable motor cut-off and remote/timer-controlled spoilers, together with radar fire-control systems that track a single ranging rocket before firing the whole salvo in order to determine the real flight path in the real conditions.

[Weaver]

Basically you're correct.  However, remember spinning the rocket creates a gyroscopic effect with the result that it tends to fly in a straight line.  "Tends" because of course it is affected by external factors, such as winds as is any projectile.   Remember, this gyroscopic effect is why rifling was introduced in firearms.

However, the difference between a rocket and a bullet is that the rocket motor is producing thrust during flight, while the bullet is just coasting. If a bullet wobbles in flight, the gyroscopic effect tends to re-stabilise it, but if a rocket wobbles while it's motor is burning, the motor immediately starts actively pushing it off course.