LAST STAND ROCKET PLANES

The need for a revolutionary air defense fighter led to many other German rocket interceptor designs near the end of the war, as well as an even more bewildering array of advanced propeller planes, jet fighters and intercontinental bombers that are beyond the scope of this book. Even limiting the focus to rocket airplanes results in a lengthy list of concepts.

Junkers came up with the EF127 ‘Walli’, a rather whimsical code name for what was to have been a relatively large, horizontal take-off rocket fighter equipped with a retractable tricycle undercarriage (i. e. one with wheels under the wings and the nose), a take-off weight of 2,960 kg (6,530 pounds), a wingspan of 6.7 meters (22 feet) and an armament comprising a pair of MG 151/20 20-mm cannon and a dozen air-to-air rockets. With two solid propellant take-off assist boosters each delivering a thrust of 10,000 Newton and an HWK 105-509C dual-chamber rocket engine it was predicted to be able to climb to an altitude of 10 km (6 miles) in a mere 75 seconds, which was significantly faster than either the Me 163B or the Me 263. Apart from the boosters it had many similarities with the Me 263, but had a more conventional shape with two straight wings and a tail with horizontal stabilizers.

Then there was the Arado Аг E381 minifighter, of which the first design had a length of just 4.7 meters (15 feet), a wingspan of 4.4 meters (14 feet) and a weight of only 1,200 kg (2,650 pounds). It was to have been carried to altitude slung under an Ar 234 jet bomber, a plane that was actually operational in August 1944. Because the E381 was so small and simple, heating and electrical power would be supplied by the host during the ascent. Communication between the E381 pilot and his colleague in the Ar 234 would be via a telephone link. The E381 was to be released at an altitude of about 1 km (0.6 miles) above the enemy bomber formation to execute its attack in a shallow dive at close to 900 km per hour (560 miles per hour), firing either a single MK 108 cannon or air-to-air missiles. The Walter HWK 109-509C dual-chamber engine would subsequently be ignited to climb for a second attack pass. At that point the E381 would dive and glide to the ground unpowered. It would land using a skid, similar to the Me 163. Then the little plane was designed to be easily dismantled into wing, fuselage and tail units that could be manually loaded onto a truck for return to base.

Due to the limited ground clearance of the E381 when suspended under its carrier plane whilst on the ground, its pilot would lie on his stomach in the cramped cockpit and view through a bubble window in the nose. This prone position would also help him to sustain the high G-forces when making sharp maneuvers at high speeds. Pilots in a conventional sitting position could experience tunnel vision, black-outs (loss of vision) and even loss of consciousness when sharply starting a steep ascent or a tight turn because the centrifugal force would push blood into the lower part of their body, depriving the brain of sufficient oxygen. Similarly, when pilots would suddenly push their planes into a dive the negative G-forces would push blood into the upper part of the body, causing a reddening of his vision known as ‘red-out’. These phenomena were much less trouble when the pilot was in a prone, horizontal position, since there was little vertical distance between his upper and lower body, making it easier for the heart to keep pumping sufficient blood to the brain. Also, the prone position led to a more aerodynamic fuselage shape with a smaller frontal area, reducing drag.

The second design of the E381 was slightly larger and had a weight of 1,270 kg (2,790 pounds). What appears to be the Аг E381 III had a length of 5.7 meters (19 feet), a wingspan of 5.1 meters (17 feet) and a weight of 1,500 kg (3,300 pounds). Instead of a single MK 108 cannon, the third version was armed with six RZ-65 air – to-air rockets that would be fired from the leading edges of the wings. But the E381 project never materialized. After the war, the prone pilot position was tested in the UK using a second, experimental cockpit attached to the nose of a Gloster Meteor F8 jet fighter. For safety, the conventional cockpit was also manned. The tests showed that the prone pilot could endure slightly higher G-levels, but this position proved to be very uncomfortable, to lead to vertigo (a sensation of motion when one is actually stationary) and to seriously limit the pilot’s rear view; the latter being a very serious disadvantage in a dogfight. Furthermore, it would be very difficult to devise a good ejection seat escape mechanism for this awkward position: ejecting forward was not an option because the plane would catch up with the pilot and collide with him. After 55 hours of flight testing, the idea was abandoned. The prone position soon became obsolete after the war anyway thanks to special anti-G suits with inflatable bladders in the trousers: when they experienced negative G-forces in a sitting position, these bladders would quickly inflate to firmly press against the abdomen and legs in order to restrict the draining of blood away from the brain.

Arado also proposed to develop the TEW 16/43-13, a low-wing rocket interceptor that had a wingspan of 8.9 meters (29 feet), a Walter HWK 109-509A engine, and an armament of two MG 151/20 20-mm cannon and two MK 108 30-mm cannon set in its nose. The wings and tailplane were moderately swept back, and the pilot would sit in a conventional upright position. The company also devised the TEW 16/43-15, a combined jet/rocket powered variant in which a jet engine was mounted on top of the (lengthened) fuselage.

In his 1929 book Wege zur Raumschiffahrt (Ways to Spaceflight) Hermann Oberth had contemplated a rocket aircraft built like a tank to fly into an enemy air fleet. It could then use conventional gunfire to destroy targeted planes but he suggested that collision would also be an effective means of attack. By 1943 this dramatic concept started to look like a valid idea to stop Allied bombers, leading Lippisch to suggest a ‘ram rocket’. This would be launched vertically using a liquid propellant engine and solid propellant boosters (like the Natter) and be equipped with a sharp steel nose to slice through a bomber without damaging the ram rocket (or its pilot). In November 1944 the Zeppelin works, famous for building giant airships, had the same idea and proposed the ‘Rammjager’ (Rammer Fighter). Taking off from a jettisonable tricycle carriage, their little plane would be towed aloft by a fighter aircraft and be released near the bombers. The pilot would ignite a single solid propellant Schmidding rocket (similar to the Natter boosters) to accelerate to 970 km per hour (600 miles per hour) and launch his 14 R4M rockets. He was then expected to make a second pass and actually ram his plane through the tail section of a bomber. It was calculated that the Rammjager would slice cleanly through without great loss of speed and stabihty, and survive the collision thanks to its armored cockpit and reinforced fuselage and wings. It would then glide back unpowered and land on a retractable skid. By virtue of not having a liquid propellant rocket engine, the Rammjager was even simpler than the Natter. After towed glide flights in January 1945 an order for sixteen pre-production prototypes was placed. However, US bombers destroyed the Zeppelin factory before their construction could commence.

Another rather ludicrous proposal by Zeppelin was for the ‘Fliegende Panzerfaust’ (Flying Armored Fist, or Flying Bazooka). This was to be an aircraft filled with high explosives to ram and blow up an enemy bomber; the pilot was supposed either to eject just before impact or sacrifice himself to ensure an accurate hit. If possible, the plane would also be equipped with a cannon to shoot down other bombers in advance of the final ramming attack. In line with the need for a very simple and cheap design, it would be powered by six solid propellant rocket motors only. The machine would be towed to altitude, for which it was equipped with a hooked nose connecting to the tail of a regular fighter aircraft. It would have been some 6 meters (20 feet) in length with a wingspan of 4.5 meters (15 feet). The project never got any further than a full-scale mockup that was presented to the SS in January 1945.

Then there was the DFS ‘Eber’ (Boar), a tiny rocket fighter that either an Fw 190 propeller fighter or an Me 262 jet fighter would tow using a long pole, then release some 300 meters (1,000 feet) above the bombers. The Eber would engage a target in a gliding dive utilizing either a single Mk 108 cannon or air-to-air rockets, and then ignite two solid propellant motors that would deliver a thrust of 15,000 Newton for 6 seconds to make a second attack in which it would ram a bomber. The prone pilot would be protected by an armored cockpit and use a special spring-dampened shding seat to soften the 100 G deceleration shock that would result from the collision with a large enemy plane. After the final attack, a parachute would pull the pilot and his seat from the cockpit. At sufficiently low speed, he would jettison the seat and land using his own parachute. The airplane itself was expendable.

The fact that the idea of ramming enemy planes was popular near the end of the war reflects a level of panic in German military planning and an increasing fanatical demand for pilots to sacrifice themselves in defense of their doomed motherland. The Sombold So 344 ‘Rammschussjager’ (Ram-shoot Fighter) was another approach to the ramming plane concept. Rather than ramming a bomber itself, this rocket aircraft would carry a 400 kg (880 pound) warhead on its nose and fire it into the middle of a bomber group using a solid rocket motor built into the bomb. The warhead was fitted with four stabilizing fins and a proximity fuse for automatic detonation when close to an enemy plane. Allied bombers flew in tight formations so that the onboard gunners could provide cover to each other’s planes and work together to bring down attacking fighter planes. The explosion of the warhead released by the So 344 was expected to destroy three of four bombers and open the formation sufficiently for other German fighters to engage individual bombers. The So 344 was expected to join this carnage employing a pair of machine guns.

The So 344 was to be powered by either a single Walter HWK 109-509 engine or a number of solid propellant rocket motors, have a wingspan of 5.7 meters (19 feet) and a take-off weight of 1,350 kg (2,980 pounds). Its cockpit was located well behind the wings, just in front of the vertical and horizontal stabilizers. It was designed to be carried into the air on top of another aircraft, to land employing a skid, and then be dismantled into two sections for transportation by truck back to its base.

Messerschmitt also produced designs for simple towed ramming rocket aircraft. The basic design for the Me P.1103 of July 1944 had its pilot lying prone inside an armored cylinder cockpit. After release from a conventional Bf 109 fighter or even an Me 262 jet fighter tow plane, it would attack at 700 km per hour (435 miles per hour) shooting a single MK 108 30-mm cannon before ramming one of the bombers. A parachute would then pull the pilot and his seat out of the aircraft. Another chute would soft-land the reusable assembly consisting of the armored cockpit, the cannon, and the floor-mounted Walter RI-202 ‘cold’ rocket engine (the same as in the RATO pods used on German bombers) for retrieval. The tail section would be lost, but that was to have been only a simple wooden empennage derived from the VI unmanned flying bomb. Another interesting fact about the Me P.1103 is that it was to have a rearward firing rocket launcher to defend itself from Allied fighters. A design for an alternative P.1103 version of September 1944 shows a sitting pilot looking through a conventional bubble canopy. The Me P.1104 was another Messerschmitt design for a simple towed, rocket propelled defensive interceptor. This one would have had an HWK-109-509A rocket engine (as on the Me 163B) and been equipped with a single MK 108 cannon. The total weight of the fully loaded plane was to be 2,540 kg (5,600 pounds), so its rocket engine should have provided a maximum speed of 800 km per hour (500 miles per hour) and a range of some 90 km (60 miles).

All these concepts for small and cheap rocket propelled fighters were consigned to the archives by the Luftwaffe, which was undoubtedly better news for the pilots who would have been required to fly these rickety death traps than it was for the crews of the Allied bombers. However, some other rocket fighter designs did progress a little further through the development process.

The Focke Wulf ‘Volksjager’ (the People’s Fighter; not to be confused with the Heinkel He 162 ‘Volksjager’ jet fighter) was based on the design for the Та 183 jet fighter. It was to be a defense interceptor with a similar role and mode of operation to the Me 163. It also looked a lot like the Komet, with a Walter HWK 109-509A2 and sharply swept wings mounted mid-fuselage which were to be mostly made of wood. The wingspan would be 4.8 meters (16 feet) and the total length a mere 5.3 meters (17 feet). It would take off from a jettisonable dolly, climb to the enemy bombers and attack using two MK 108 30-mm cannon located in the lower fuselage sides, then glide back unpowered and land on a retractable skid. Unlike the Me 163 (but like the Та 183) it had a horizontal stabihzer mounted on the vertical fin to form a ‘T’ shaped tail. With the addition of four solid propellant strap-on boosters, the Volksjager was intended to reach an altitude of 5.9 km (19,400 feet) in just 60 seconds, and 16.5 km (54,100 feet) in 100 seconds. This was a significantly faster climbing speed than the Komet, which did not have boosters. The maximum speed was expected to be about 1,000 km per hour (620 miles per hour). Three aircraft were under construction when the war ended but none ever flew. As was the case for the He 162 jet that was also called the ‘People’s Fighter’, the Focke Wulf was probably meant to be flown by relatively untrained pilots recruited from the Hitlerjugend, the Nazi youth movement. But the He 162 proved too difficult for amateurs to fly, and this would probably also have been the case for the Focke Wulf rocket interceptor.

Another Focke Wulf design was the Та 283, an airplane with a slender fuselage, wings swept back at 45 degrees, and two large ramjet engines. Since ramjets do not work at low speeds, for take-off the aircraft was to have a single Walter HWK 109- 509A rocket engine and about 30 seconds worth of rocket propellant. To prevent the big ramjets from disturbing the airflow over the wings, they were to be mounted on the sharply swept tailplane. The armament was envisaged to comprise two MK 108 cannon. When this concept was judged lacking in performance an improved design was proposed in which the fuselage intended for the Fw 252 jet fighter would have a small jet engine emplaced in the central fuselage, two ramjets on the tailplane and a Walter HWK 109-509A just beneath the tail boom. This design was so preliminary that it didn’t even have a proper designation, but after the war it came to be known as the Fw 252 ‘Super Lorin’ (after the inventor of the ramjet concept, Frenchman Rene Lorin).

Heinkel’s contribution to the mixed bag of radical rocket fighter concepts was the P.1077 ‘Julia’. As designed in August 1944, the wooden Julia would have been 6.98 meters (22.9 feet) long, had straight shoulder-mounted wings with a total span of 4.6 meters (15 feet) and a tail with twin vertical stabilizers. Its propulsion was to have been one Walter HWK 109-509C engine with separate combustion chambers for the initial climb and subsequent cruise, and two booster rockets mounted on either side of the fuselage. It would have had two MK 108 cannon housed in blisters on the sides of the forward fuselage. It was initially envisaged that the pilot would fly in a
prone position but an alternative design was prepared in which he would sit in a conventional manner. Like its Bachem Natter competitor, the Julia would have been launched vertically off the ground, but after the attack the pilot would have landed it on a retractable skid rather than bail out. In September 1944 the RLM ordered 20 Julia prototypes and then two weeks later demanded the production of 300 operational aircraft per month. Nothing came of this, of course. Only towing trials with a full-scale mockup were performed before it was destroyed when the Vienna woodworks was bombed, and the Schaffer company in Linz had time only to start two unpowered prototypes, neither of which was completed.

The DFS 346 of the German Institute for Sailplane Flight was not intended for combat, it was designed purely as an experimental research plane. Its chief designer, Felix Kracht, gave it wings swept back at 45 degrees, a streamlined fuselage with a prone pilot, and an HWK 109-509C rocket engine. It was to be taken to high altitude by a Domier Do 217 bomber and then air-launched, a novel concept which, it was hoped, would save the DFS 346 sufficient propellant (otherwise needed for take-off and ascent) to break the sound barrier. The altitude provided by the carrier plane also resulted in lower aerodynamic drag due to the thinner atmosphere and meant Mach 1 could be reached at a lower absolute flight speed since the speed of sound is lower in the colder high-altitude air. The pilot was in a pressurized section that formed a self-contained escape capsule which could be separated from the plane in an emergency. Stabilized by a small parachute, the capsule would fall to an altitude of about 3 km (10,000 feet) where the air pressure is safe, the Plexiglas nose section would separate and the pilot would slide out and land using his parachute. The unfinished DFS 346 prototype was captured by the Soviets at the end of the war, taken to Russia, rebuilt and actually flown (we will discuss this further in a later chapter).

The concept of air-launching was later adopted in the USA for the world’s first supersonic rocket plane, the post-war X-l. The highly swept wings of the DFS 346 were actually much more advanced than the conventional straight wings of the X-l and make the DFS 346 look more like a modern supersonic fighter than the famous

American rocket plane which relied upon brute rocket power and sturdy wings rather than sophisticated aerodynamics to blast through the sound barrier.

Felix Kracht also designed the DFS 228 rocket propelled reconnaissance aircraft, a fairly conventional sailplane design with long, slender but straight wings spanning 17.6 meters (57.7 feet). It was to have a dry weight of 1,350 kg (9,280 pounds) and a take-off weight of 4,210 kg (2,980 pounds). It would be air-launched from on top of a Do 217, be powered by a Walter rocket motor, and land using a belly-mounted skid. The pilot was to be prone in a pressurized escape capsule. The long wings were designed to enable the plane to achieve a cruise altitude of 24 km (80,000 feet), safe from interception by Allied fighters. Its maximum speed was estimated to be about 900 km per hour (560 miles per hour). The mission profile was for a powered climb followed by a slow, unpowered descending glide, then reigniting the rocket motor to climb back to altitude, and so on until the propellant was finished. The resulting saw­tooth flight pattern that would give the aircraft the relatively long range of 1,050 km (655 miles) also prompted its nickname of ‘Sagefish’ (Sawfish).

Walter designed a new rocket motor for the plane because the requirement for a very streamlined fuselage in combination with weight balance made it necessary to place the motor near the plane’s center of gravity, which required fitting a long thrust tube to the tail. The resulting motor was an elongated version of the single­chamber HWK 109-509A2 named the HWK 109-509D. The DFS built three prototypes: VI, V2 and V3. The DFS 228 VI had a conventional seat but it was shghtly inclined to the rear to accommodate the fuselage streamlining and to assist the pilot in handling high G-loads (a similar idea was introduced in the F-16 fighter jet several decades later). The VI made several unpowered glide flights after being carried to altitude on top of a Do 217, and was later fitted with the HWK 109-509D for ground tests. This prototype was captured by the Americans at the end of the war and in 1946 was sent to Britain for study, but it arrived in very bad condition and was apparently scrapped. The V2 had a cockpit with a prone pilot position and apparently made several glide flights before being damaged in a landing accident. The V3 was never finished. None of these aircraft ever flew under rocket power.

Rather than develop a completely new aircraft, in mid-July 1943 Arado proposed to produce a high-altitude reconnaissance rocket plane by modifying the Ar 234 jet, which had made its first flight in June. In the initial design the two jet engines were to be replaced by two HWK 109-509A rocket engine pods. The resulting Ar 234R ‘Hohenaufklarer’ (High-altitude Scout) would be able to take off by itself, ascend to an altitude of 16.5 km (54,000 feet) and photograph its targets while descending in a shallow glide. It would be equipped with the pressurized cockpit already created for the Ar 234C reconnaissance jet. A later design had a dual-chamber HKW 109-509C built into the tail instead of pods slung under the wings. This version was to be towed to an altitude of 8 km (26,000 feet) by a Heinkel He 177 bomber (a large, long-range bomber then under development) and upon being released it would boost itself up to 18 km (59,000 feet). The Ar 234R would be able to photograph areas some 250 km (155 miles) from its base, being towed 200 km (125 km) towards its target and flying a further 50 km (30 miles) on rocket power. The plane would subsequently glide over its targets, igniting the rocket engine at intervals to maintain sufficient altitude.

Freed from the need to mount engines under the wings, a special highly efficient wing was designed to give the aircraft a glide angle of 1 to 14 (in which it would lose 1 meter of altitude for each 14 meters of horizontal flight), sufficient to enable it to glide the entire 250 km (155 miles) back to base.

Another Ar 234 variant fitted with a rocket engine was actually under construction when the Allies captured the factory in which it was being assembled. It consisted of an Ar 234B fuselage equipped with a new concave-curved swept wing optimized for high-speed flight. It was powered by a pair of BMW 003R engines, each consisting of a BMW 003 turbojet with a BMW 718 liquid propellant rocket engine mounted on top. The fact that the pumps for the rocket propellant were powered by the jet engine resulted in a nicely compact assembly. The rocket engine could deliver an additional 10,000 Newton of thrust for 3 minutes during take-off and ascent. Unfortunately the prototype was scrapped.

The sole surviving Ar 234B can be seen in the National Air and Space Museum’s Steven F. Udvar-Hazy Center near Washington Dulles International Airport. It is the basic jet type with a pair of Walter RI-202 ‘cold’ RATO pods under its wings. The parachute pack intended to retrieve the pods following jettisoning soon after take-off can be clearly seen on these examples.

Another pragmatic design enhanced the standard Me 262 jet fighter (which had a jet engine under each wing) with an additional rocket engine. To test the principle an Me 262 was adapted to accommodate a redesigned HWK 109-509A2 motor with the combustion chamber installed in the tail; a portion of the lower part of the rudder was cut away to make room for the nozzle and the rocket exhaust. This Me 262 C-la ‘Heimatschiitzer Г (Home Defender I) prototype made its first rocket assisted take­off on 27 February 1945. The combined thrust from the two jets and the single rocket reduced the take-off run by at least 200 meters (660 feet) and pushed the plane to an altitude of 8 km (26,000 feet) in about 3 minutes (about half the time required by a standard Me 262 and similar to the Me 163 Komet’s performance). Major Heinz Bar later managed to intercept and shoot down an American P-47 Thunderbolt fighter in the rocket propelled test plane by climbing to about 9 km (30,000 feet) in a little over 3 minutes.

A similar concept was the Me 262 C-lb ‘Heimatschiitzer IF which was provided with two BMW 003R combined jet-rocket engines for boosted thrust. Only a single prototype was built and its only flight with the combined propulsion was made on 26 March 1945. This engine was also to have been mounted on an He 162 ‘Volksjager’ (People’s Fighter), the standard version of which had a single BMW 003 jet engine on its back. However, the creation of this He 162E prototype could not be achieved before the war ended.

Despite the success of the ‘Heimatschiitzer Г it was judged that the rocket engine added too much complexity to the jet fighter, making it more difficult to maintain. In addition, the tanks needed for the less propellant-economic rocket severely reduced the available space for fuel for the jet engines, which limited the range and flight duration of the fighter in comparison to a standard Me 262 (issues that would also plague the post-war mixed-power interceptor designs that we will discuss later). These considerations led to the design of the ‘Heimatschiitzer IIP which had a rocket engine bolted onto the belly of the aircraft and its propellant in drop tanks that would be jettisoned once they were empty so that the plane would not be burdened by their useless weight and aerodynamic drag. The advantages of this arrangement were that it required fewer modifications of the standard Me 262, and the modified Me 262 could take off without the rocket engine if it were not needed. Another plus was that maintenance of the rocket system could be separated from maintenance of the aircraft: a fighter would not be grounded by a malfunctioning rocket engine, but could be quickly fitted with a replacement engine while the faulty unit was taken to the repair shop (an idea which, after the war, would be applied to the French Mirage rocket-motor equipped fighters).

Walter designed a powerful ‘hot’ engine based on his HWK 109-509 series for the ‘Heimatschiitzer IV’. This HWK 109-509 S2 gave a thrust of 20,000 Newton and weighed just 140 kg (310 pounds). The engine was to be mounted on the belly of the plane, just behind the roots of the wings. Two jettisonable tanks would be carried externally on bomb attachment points under the nose, with flexible hoses delivering a total of 1,200 liters of T-Stoff to the Walter motor. The C-Stoff would be carried in the rearmost converted fuselage tank. This was designated the Me 262 C-3 and work on the prototypes started in January 1945. Tests on the Т-Stoff tanks apparently revealed a problem with feeding fuel when the drop tanks were mounted lower than the rocket motor. In April the Allies overran the factory at Jenbach before a single prototype could be completed.

Eugen Sanger’s design for the ‘Silbervogel’ (Silverbird) intercontinental bomber surely ranks as the most ambitious of Nazi Germany’s rocket plane concepts. It was the first, more or less realistic design for an aircraft capable of flying on the edge of space and it is therefore described in more detail in a following chapter.

Germany hoped that its superior rocket and jet airplane technology would counter the vast numbers of conventional planes that were being manufactured by Americans in their secure homeland. Given a bit more time, this might have worked at least for a while and greatly prolonged the war in Europe. The Luftwaffe might have been able to put some really revolutionary aircraft into the skies, and a German rocket aircraft would likely have been the first to exceed the speed of sound. However, by the time the ‘wonder weapon’ airplanes received proper support it was already too late, and in any case the developments were too scattered, rivalry between the military services too disruptive, and the constraints in terms of material and propellant availability too great. Some of the small interceptors relied on Arado jet carrier planes that were not themselves available, and those meant to be towed behind conventional bombers and fighters would have been vulnerable to enemy fighters during the first phase of their mission due to the low speed of the towing operation. Many of the RLM designs now seem to be more the results of desperation and wishful (albeit creative) thinking than the reality of military operations. Nevertheless many post-war airplane designs were strongly influenced by some of the more brilliant German developments, particularly the Me 163 and Me 263.