Wasserfall antiaircraft rocket

[Justo Miranda]

Regarding the use of fuel booster rockets, I remember reading a long time ago (I don't remember the source) that EMW engineers were given the directive to minimize vibrations and sudden movements that could affect the delicate guidance system (they did not specify what type). Perhaps that was the reason why they decided to use the four fins installed in the midsection of the fuselage.

 

[Justo Miranda]

I’ve continued to dig on the question of whether the C2 Wasserfall jettisoned its thrust vector control vanes once its velocity was sufficient to depend on aerodynamic control.

Sources vary. A few say its was planned to improve efficiency but the vanes burned off anyway so wasn’t needed. A few others say the vanes burned unevenly, causing asymmetric thrust, making jettison critical.

Ive found a very good technical article on Wasserfall in a 1951 Interavia magazine by Rudolf Reichel. I think Reichel was at Peenemunde so can be regarded as a primary source ? His article stated that it was set up for vane jettison, each vane and backplate assembly being held in a slide rail by a squib operated bolt.

I have yet not found a wartime German language technical report that confirms this, so would say squib jettison on C2 is 80 percent but not certain.

I think a fair number of early missiles that followed the war also used graphite TVC vanes. Does anyone know if any of those had a scheme to jettison vanes once up to speed ?

That's new to me, I've always thought that they burned during flight without affecting the aerodynamic control surfaces

 

[Justo Miranda]

The warhead was really too small to accomplish that. From everything I've read on it, they intended it to shoot down planes but had serious doubts about its accuracy and the lack of a proximity fuze to do it. You needed to only get close to shoot down a plane. That was how most SAM's through at least the 60's worked.

What surprises me about the German SAM program is:

First, they didn't pursue a ramjet missile. This would have given them a SAM with greater range and reliability than a straight rocket, solid or liquid fuel.

They made little or no attempt to improve solid fuels.

They failed to consider a much larger proximity fuze using a small on board radar given the room their SAM's had internally. Command detonation was explored at least some.

They didn't aggressively try and improve their electronics technology.

Of their SAM designs, only Enzian might have worked to break up a bomber box. With a 500 kg warhead it had the possibility. Of course, any SAM in service really needed to be able to intercept RAF bombers at night flying in a stream too. Again, the only real option was being able to target and engage single bombers.

In my opinion, the reason why they did not use large quantities of solid propellants is the starvation of materials for the manufacture of ammunition. Also the ramjets needed rockets to reach the ignition speed.

Liquid propellants could be obtained from the air and the sun (through potatoes).

 

[T. A. Gardner]

In my opinion, the reason why they did not use large quantities of solid propellants is the starvation of materials for the manufacture of ammunition. Also the ramjets needed rockets to reach the ignition speed.

Liquid propellants could be obtained from the air and the sun (through potatoes).

That's the problem. The Germans never went beyond double base nitrocellulose propellants--essentially the "gunpowder" used in artillery. They failed to produce something like the US GALCIT series of potassium perchlorate and asphalt ones, or Goodyear's Thiokol rubber sulphate based versions. These had much greater energy than diglycol the Germans were using.

The GALCIT versions were likely producible in Germany as they wouldn't have had much, if any, impact on fuel and other petroleum production using only tars. The Thiokol based rubber ones would have been highly problematic given the general shortage of rubber in Germany.

From what I can tell, it is simply a case of myopia on the part of German rocket engineers and scientists. They saw liquid fuels as far better for sustained burns and for their energy content. They ignored solid fuels as these didn't fit their needs in developing large rockets like the A-4. That is, they fixated on an outcome and failed to consider alternatives.

In the US, the reverse occurred. While US rocket scientists knew quite a bit about liquid fuels and pretty much had discovered all the same ones the Germans had, there was no official interest in large liquid fuel rockets so there was no funding to be had for that. The result was that liquid fuel rockets and motors were little more than scientific curiosities at the time. Instead, the military wanted solid fuel rockets for artillery, as JATO units, and for other such applications. So, the focus was on developing better solid fuels. That happened, and did so on about the same timeline as the Germans did for liquid fuels.

In the long run, solid fuels proved more viable than liquids and that's where we are today.

 

[Scott Kenny]

In the long run, solid fuels proved more viable than liquids and that's where we are today.

For combat use, sure.

Liquids still rule in the "lifting heavy weights to orbit" department.

 

[T. A. Gardner]

For combat use, sure.

Liquids still rule in the "lifting heavy weights to orbit" department.

Absolutely. For very large missiles and rockets liquid fuel is the go-to fuel. For military purposes, solids win hands down. They are far safer and easier to handle. They store better than liquid fuels.

 

[BernardQuatermass21]

It took years to tame castable solid propellants to the point where they had the performance and reliability to be a viable option for large sustainer motors. Hence the post war high altitude SAMs fielded by the USSR and US followed the same path as Wasserfall, with liquid fuel sustainers using nitric acid as the oxidiser. Battlefield, intermediate range and intercontinental ballistic missiles all followed the same development path, adopting liquid fuelled technology before being replaced by solid fuelled alternatives years later.

The Wasserfall design study was undertaken between 18 Sept 1942 to 20 April 1943. At that point liquid hypergolics were the bleeding edge of technology. Castable solid fuels with the reliability and performance for high altitude SAM were years away.

It doesn't seem to me to have been particularly myopic for the Wasserfall team to focus on liquid fuelled engines, given their rather shorter time to market.

 

[BernardQuatermass21]

Regarding the use of fuel booster rockets, I remember reading a long time ago (I don't remember the source) that EMW engineers were given the directive to minimize vibrations and sudden movements that could affect the delicate guidance system (they did not specify what type). Perhaps that was the reason why they decided to use the four fins installed in the midsection of the fuselage.

The EW engineers (it was never called EMW) chose a liquid fuel motor because it nearly met the performance requirements. The solid fuelled alternatives were much worse.

The adoption of a low thrust long burn time liquid fuel motor,without a booster, did have the advantage of relatively low launch acceleration, which was kinder to the avionics.

The fins installed mid section are wings, for lift. To achieve the tight turns needed for a 12g pursuit course. Wasserfall, like most missiles with cruciform wings, flies like an aeroplane, depending on lift from its wings and needing to be cautious with its angle of attack to avoid the collapse in lift that a stall would induce. All of this is covered in the Wasserfall Aerodynamics Report, published late war by the Peenemunde Aerodynamics Institute.

 

[T. A. Gardner]

The EW engineers (it was never called EMW) chose a liquid fuel motor because it nearly met the performance requirements. The solid fuelled alternatives were much worse.

The adoption of a low thrust long burn time liquid fuel motor,without a booster, did have the advantage of relatively low launch acceleration, which was kinder to the avionics.

Interestingly, the solution almost everybody settled on postwar with SAMs was to use a powerful solid fuel booster, preferably in-line with the missile to avoid asymmetric thrust, to get the missile up to speed in a matter of seconds, while locking the controls to avoid deviations in course. This reduced the need for a powerful liquid fuel engine on the missile itself as this engine only needed to keep the missile at speed.

What held that solution back for countries other than the US initially was their lack of a better solid fuel than nitrocellulose. Britain, for example, stuck with multiple boosters using that on their early SAMs because that was what they had and it was a cheap solution. They used very large fins to stabilize the missile during boost because of the potential for asymmetric thrust.

The fins installed mid section are wings, for lift. To achieve the tight turns needed for a 12g pursuit course. Wasserfall, like most missiles with cruciform wings, flies like an aeroplane, depending on lift from its wings and needing to be cautious with its angle of attack to avoid the collapse in lift that a stall would induce. All of this is covered in the Wasserfall Aerodynamics Report, published late war by the Peenemunde Aerodynamics Institute.

Again, postwar, fins of that sort while providing some aerodynamic lift were found to limit the ability or a missile to make high G maneuvers rather than enhance it. That is why EW or EMW, reduced the size of the wings on Wasserfall. The original larger wing design made the missile too stable. On the whole, wings like Wasserfall had were a net negative for a SAM.