Why did Luftwaffe prefer 21cm Nebelwerfer rocket?

[davebender]

1943 rocket production.
1.1 million. 15cm Nebelwerfer rocket.
119,600. 21cm Nebelwerfer rocket.

15cm rocket.
About 35kg total weight. (110kg for 21cm rocket).
340 m/s velocity.
6,000m max range.
Dispersion. 130m x 80m. 50% of projectiles would land in this area.
About 2.5kg of HE in warhead. Designed for enhanced fragmentation.

15cm was preferred Heer Nebelwerfer rocket by a wide margin. Why did Luftwaffe prefer the much heavier 21cm rocket? You could carry three 15cm rockets for same weight as one 21cm rocket and it's plenty powerful enough to kill any bomber. 15cm rocket was also the most accurate Nebelwerfer. Put three under each wing and you can create a 130m x 80m barrage box for enemy bombers to fly through.

 

[Civettone]

Dave, the 21cm was not intended to destroy a bomber, it was used to disperse them, so lone bombers could be taken out.

Barrage boxes rarely work.

Kris

 

[Tante Ju]

Its easy. A 10 kg warhead vs 2,5 kg warhead.

 

[davebender]

Not so easy. 21cm rocket weighs three times as much so it's 10kg warhead vs three 2.5kg warheads with overlapping blast patterns.

Overlapping blast patterns cause more damage then a single large blast and cover a greater area. German Army figured this out. It's also why 1970s ICBMs starting switching to relatively small MIRV warheads rather then a single large warhead.

 

[Civettone]

Not so easy. 21cm rocket weighs three times as much so it's 10kg warhead vs three 2.5kg warheads with overlapping blast patterns.

Overlapping blast patterns cause more damage then a single large blast and cover a greater area. German Army figured this out.

No no, you are just imagining this. They always preferred one large explosive versus several smaller ones. Same things with aerial bombs.

But anyway, as I said before, the Werfer-Granate were meant to break up the formation, not to destroy the bomber.
Kris

 

[tyrodtom]

The 21cm Nebelferwer used by the Luftwaffe had a 41 kg warhead, with a time fuse.
It was meant to explode inside a formation box, hopefully downing some aircraft thru direct damage but mostly to scatter the formation so the aircraft could be destroyed individually.

 

[davebender]

Werfer-Granate 21 - Wikipedia, the free encyclopedia

Modified from the 21 cm Nebelwerfer 42 infantry barrage rocket projectile and reconfigured for air-launch, the spin-stabilised rocket was propelled by 18.4 kilograms (41 lb) diglycol solid fuel, and the warhead weighed 40.8 kilograms (90 lb). The Wfr. Gr. 21's projectile had a velocity of 320 metres (350 yd) per second (1,150 km/h, 716 mph) and a maximum range of 1,200 metres

Looks like Luftwaffe decreased rocket fuel and increased warhead by an equal weight. Max range about 20% of normal Nebelwerfer rocket.

You could do the same trick with smaller 15cm rocket and end up with a warhead of about 10kg with rocket total weight still about 35kg.

A bit off topic.
By 1944 German Army developed a new folding fin version of 15cm Nebelwerfer rocket. Late war production problems prevented this newer model artillery rocket from entering mass production. However I think that's where idea for small R4M FF rocket came from.