On July 28, 1944, a flight of P-51 Mustangs escorting a squadron of B-17 Bombers on a mission over Merseburg, Germany, spotted something strange in the distance: a pair of white contrails rising at tremendous speed into the stratosphere. As the contrails pitched over and dove onto the bomber stream, the fighters broke formation to intercept. Seconds later, a pair of tiny egg-shaped aircraft with short swept-back wings flashed by and plunged back into the clouds, travelling faster than anything the American pilots had ever seen. It was the Allied air forces’ first encounter with a new German secret weapon: the rocket-powered Messerschmitt Me-163 Komet, an aircraft so fast its performance would not be matched for nearly a decade, yet so horrendously dangerous to fly it would claim the lives of more German pilots in  development and training than Allied aircrew it took down in combat.

Experiments with rocket-powered aircraft have a long history in Germany. In a series of increasingly audacious publicity stunts, during the 1920s automobile manufacturer Fritz Opel experimented with fitting gunpowder rockets to a variety of vehicles from cars to railway wagons. These experiments culminated in the construction of the Lippisch Ente, or Duck, which on June 11, 1928 became the first manned aircraft to fly under rocket power. Later in the 1930s, aircraft manufacturer Ernst Heinkel undertook a series of experiments to develop a liquid-fuelled rocket engine for use in aircraft. Heinkel’s first success came in March 1937 when a modified He-112 propeller-powered fighter flew under rocket power for 30 seconds. Heinkel next constructed the diminutive He-176, which on June 20th, 1939, became the first aircraft to take off, fly, and land solely under rocket power..

But while Heinkel had high hopes for rocket aircraft, the German Air Ministry was decidedly less enthusiastic. On first being shown the He-176, Generaloberst Ernst Udet, Director-General of Equipment for the Luftwaffe, exclaimed: “You want to fly with that? It has no wings…those are running boards!”

On actually seeing the aircraft fly, Udet reportedly flew into a rage, declaring: “That is no airplane, leave it alone! I forbid you to fly it again.”

Even a demonstration in front of top Nazi dignitaries including Adolf Hitler on July 3 failed to make any impact, and Germany entered the Second World War with conventional propeller-driven aircraft. But the realities of War would soon force the High Command to change its mind. Starting in 1942 the Royal Air Force and United States Army Air Force began a concerted strategic bombing campaign against Germany and occupied Europe, pounding cities, factories, and other targets round-the-clock. The Luftwaffe, stretched thin by Hitler’s invasion of Russia and chronically short on men and fuel, was unable to cope, and so the call went out for a fast, inexpensive rocket-powered interceptor that could stem the tide of Allied aircraft.

The aircraft that would become the Komet emerged from the work of two aviation pioneers. The first was Alexander Lippisch, designer of the pioneering Ente, who, working with DFS, the German Research Institute for Sailplane Flight, was attempting to develop a unique high-speed tailless glider. In 1939, Lippisch left DFS and took his design to aircraft manufacturer Messerschmitt, who gave it the designation Me-163. Messerschmitt soon began experimenting with fitting the 163 with a revolutionary new rocket engine designed by Hellmuth Walter, who had also designed the engine for Heinkel’s pioneering He-176. Walter’s R-1-203 ‘cold’ engine, originally developed as a Jet-Assisted Take-Off or JATO pod for helping overloaded transport aircraft get off the ground, reacted concentrated Hydrogen Peroxide with Sodium Permanganate to generate high-pressure steam, producing around 1000 pounds of thrust.

The result was an aircraft of unprecedented performance. On the 2nd of October 1941 test pilot Heinrich ‘Heini’ Dittmar flew the prototype Me-163A to a record airspeed of 1003.67 mph, becoming the first pilot to exceed 1000 mph in level flight. Three years later Dittmar would fly the improved 163B model to 1130 mph – a record that would not be beaten by a jet aircraft for almost a decade. The Komet’s climb rate also far exceeded that of any contemporary aircraft, being able to climb to an altitude of 39,000 feet in less than four minutes. This in turn required pilots to maintain a special low-fibre diet to prevent gas from expanding painfully in their gut too uncomfortably. Even unpowered the Komet displayed superb handling characteristics, with pilots reporting the aircraft to be nearly impossible to stall or spin. And so fast was it in a  glide that upon being buzzed by a 163A at 300mph, a startled Ernst Udet is reported to have exclaimed “What sort of engine has it?”, to which a presumably smug Alexander Lippisch replied “None.”

Yet despite this blistering performance, the Komet quickly revealed itself as an extremely hazardous aircraft to fly. Among its major flaws was its landing gear. For takeoff the Komet was fitted with a simple two-wheeled dolly which was jettisoned as soon as the aircraft left the ground, after which the aircraft landed on a retractable ventral skid. However, if the pilot forgot to extend the skid or unlock the skid, the impact of landing could cause severe injuries. Indeed, during the Komet’s development three of its main test pilots – Heini Dittmar, Rudy Opitz, and Hannah Reitsch – suffered serious spinal damage and skull fractures due to hard landings and spent several months in hospital recovering.

But the greatest danger by far came from the Komet’s engine. Hellmuth Walter’s HWK 509 “Hot Engine,” which powered the production Me-163B, ran on a combination of two propellants: “T-Stoff”, highly concentrated hydrogen peroxide;  and “C-Stoff”, a 30% mixture of Hydrazine Hydrate and Methanol. These propellants were hypergolic, meaning that when mixed they immediately and violently exploded. The fact that they were both colourless liquids meant that handling accidents were common, as in the case of one unfortunate ground crewman who inadvertently poured a container of T-Stoff into another containing a small quantity of C-Stoff. As author William Green recounts: “Before he realized the magnitude of his mistake his remains had been spread thinly over the entire test shed.”

This extreme volatility meant that great care had to be taken when refuelling the Komet, with the propellants being loaded one at a time and the engine flushed out with water between each flight. But despite these measures, many Komets and ground crew were lost to explosions before the aircraft ever left the ground. Even worse,T-Stoff is highly corrosive and can strip flesh from bones in seconds. It also tends to react with even the smallest speck of dirt or organic matter, decomposing violently into scalding steam and oxygen, meaning it could only be stored in glass or enamel-lined containers. While Komet pilots were issued with special acid-proof asbestos flight suits, any landing made with propellant left in the tanks was likely to end in disaster – as Mano Ziegler, one of the few Komet pilots to survive the war, recounts in his memoirs:

A certain Feldwebel Alois Worndl from Aschau, an excellent fellow and completely reliable flying with the accuracy of a precision instrument, was chosen from among us pupils to make the first sharp start in the Komet. “Make it good, Alois!” We shouted, and then he was off.

…As expected, Alois’ rocket motor cut out at about 6000 metres altitude, and he turned back towards the field, as precise as ever. Then, without warning, “Sideslip!” The shout came from one of the group. Alois was much too high to touch down anywhere near the landing cross! “Sideslip, sideslip!” We all shouted as if he could hear us, but the Komet shot past us and past the landing cross – too high, too fast!

Anxiously we watched the Komet touch down far outside the airfield perimeter, rebound into the air, drop back again like a brick, then skid into some rough ground and turn over on its back. A split second later a blinding white flame shot up, followed by a mushroom of smoke.

On other occasions pilots suffered a fate worse than an explosion, as in the case of Oberleutnant Josef Pohs, who on one flight released his takeoff dolly too early. The dolly bounced off the ground and struck the aircraft, rupturing a T-Stoff line. Pohs immediately jettisoned his fuel and banked around to make an emergency landing, but just like Alois Worndl missed the runway, touched down on rough ground, and flipped over. To the relief of his watching comrades his aircraft did not explode, but when they finally reached him and turned the Komet over they were greeted with a gruesome sight: T-Stoff leaking from the ruptured line had dissolved the unconscious Pohs alive.

Despite these hazards, development of the Komet pressed ahead, with the first operational squadron, Jagdgeschwader 400, receiving production Me-163Bs in May 1944. The Model B was larger and more streamlined than the Model A and equipped with armour protection for the pilot and a pair of MK 108 30mm cannons with 60 rounds of ammunition each. Due to its limited engine endurance of only 6 minutes, the Komet served as a point-defence interceptor, with airfields being located next to strategic targets such as the Leuna synthetic fuel works near Leipzig. To conserve fuel, the Komet was towed to the runway by a modified agricultural tractor before having its propellant tanks filled. The pilot then took off and climbed to an altitude of 39,000 feet before cutting off the rocket motor and making a gliding dive onto the approaching bomber formation. The pilot would make as many attack runs as fuel and airspeed would allow before breaking off and gliding to a landing on the ventral skid. The now-immobile Komet would then be retrieved by another tractor and prepared for its next flight.

The first operational sorties soon revealed yet another of the Komet’s many flaws: it was too fast. Due to the short range of its cannons, during a high-speed approach the pilot only had a window of around 3 seconds in which to aim and fire, making it impossible for all but the best marksmen to hit their targets. Engineers attempted to correct this issue by developing a unique weapon known as the SG 500 Jagdfaust. This consisted of a set of five 50mm cannon barrels mounted vertically in the wing roots and connected to a photocell, such that when the Komet pilot passed into the shadow of a bomber all ten barrels would fire automatically. Field trials revealed the system to be highly effective, with Lieutenant Fritz Kelb reporting that the B-17 he fired upon “simply disintegrated.”  However, the War ended before the weapon could be deployed in large numbers.

Meanwhile, though the Komet’s incredible speed and maneuverability had initially taken the Allies by surprise, escort fighter pilots soon learned how to counter them, with Lieutenant Colonel John Murphy and Lieutenant Cyril Jones of the American 359th Fighter Group shooting down the first Me-163 on August 16, 1944. Allied pilots also discovered the Komet to be most vulnerable just after landing, and many were destroyed on the ground by roving fighter-bombers. But in the end what finished off the Komet was the deteriorating state of the German war economy, and by early 1945 a shortage of pilots, fuel, and spare parts left the 370 aircraft produced laying idle on the ground. Only a handful of sorties were flown before Germany finally surrendered on the 8th of May, 1945.

So what, in the end, did the Komet achieve? While exact figures are hard to come by, it is believed that between May 1944 and April 1945 Me-163 pilots shot down between 9 and 18 Allied bombers against a total of 10 Komets lost in combat – with many more aircraft, pilots, and ground crew were lost to accidents during the Komet’s long and troubled development. Strategically the Komet was an abysmal failure which, like so many other German ‘wonder weapon’ projects, consumed vast quantities of resources and manpower urgently needed elsewhere while contributing little to the final outcome of the war. Yet despite this, the Komet was an impressive technical achievement and closely studied by the Allies after the war. During the late 1940s and  early 1950s the United States, Soviet Union, and United Kingdom all experimented with mixed-power interceptors propelled by a combination of jet and rocket engines in order that combined the high speed and climb rate of the Komet with the greater endurance and range of a regular jet. However, it was soon realized that the interceptor role was more economically filled by unmanned surface-to-air missiles, and the rocket-powered fighter faded into irrelevancy, an impressive but obscure footnote in the history of aviation.

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Bonus Facts

#1: Only one Allied pilot ever flew the Komet under power: Royal Navy Captain Eric “Winkle” Brown, who to this day holds the record for the most different aircraft types flown by a single person. On May 17, 1945, Brown drove to the Me-163 airfield at Husum and asked the German ground crew to prepare an aircraft for him. At first the crew was refused, not only because of the dangerous nature of the aircraft but because following a series of incidents in which Allied pilots were killed flying captured German aircraft, flights like the one Brown was requesting were officially forbidden. Eventually Brown agreed to sign a disclaimer absolving the crew of any responsibility, and they helped prepare and familiarize him with the aircraft. In a 2014 interview, Brown recounted his experience: “The noise is thunderous, and you are given a bit of a shake-up on takeoff. The acceleration is unbelievable. I thought the performance was – there’s only one word for it – phenomenal [but] I felt that I was flying in a tin coffin because the chances of bailing out were virtually nil. I took it on in the full knowledge of what the risk was, but at the end of the day I felt a tremendous satisfaction in having beaten the odds.”

After landing safely, Brown and the no doubt relieved ground crew reportedly celebrated with a well-earned drink.

#2: Another weapon of desperation to emerge from German drawing boards at the end of WWII was the Bachem Ba-349 Natter, or Viper – an aircraft that was essentially a manned, semi-disposable antiaircraft missile. Realizing that taking off and landing from regular airfields made interceptors like the Komet vulnerable to attack by Allied aircraft, designer Erich Bachem conceived of an aircraft that could be launched vertically from a tower, allowing it to be easily hidden in forests. Built mostly of wood and other non-strategic materials, the Natter was powered by the same Walter HWK 109 rocket engine as the Me-163 and armed with a battery of 24 55mm unguided missiles housed in its nose. Upon launch an autopilot would guide the aircraft to operational altitude, whereupon the pilot would take over and intercept the incoming bomber formation. After expending his armament and fuel, the pilot would then jettison the cockpit section and bail out. The rear section of the aircraft would descend on its own parachute, allowing it to be recovered and the engine reused.

While Bachem’s design was rejected by the Air Ministry, it soon caught the attention of Heinrich Himmler and development began in October 1944 under the direction of the SS. Following a series of 8 gliding flights and unmanned launches, in April 1945 it was decided to proceed with a manned launch. On May 1, test pilot Lothar Sieber climbed into the cockpit and blasted into the air, becoming the first person to lift off vertically solely under rocket power. The launch proceeded smoothly until the Natter reached an altitude of 500 feet, whereupon the canopy, which had been insecurely latched, flew off, knocking Sieber unconscious. The Natter continued to rise to an altitude of 4,900 feet, whereupon it pitched over, plunged to the ground, and disintegrated on impact.

Despite this setback, Sieber’s flight was followed by four more successful manned launches, but the War ended before the Natter could be used operationally. But based on telemetry gathered his ill-fated flight, it is likely that just prior to impact Lothar Sieber achieved yet another first, becoming the first man – albeit briefly – to break the sound barrier.