While Wernher von Braun is best known for his development of the V-2 rocket, his interest in rockets since the age of 13 had been to make space travel a reality, not to develop tools of war. After hearing that the V-2 rockets had struck London, he said “the rocket worked perfectly, except for landing on the wrong planet”. But while von Braun was content to work in earnest for the German military, not everyone working at the German rocket lab in Peenemünde was so eager, and the now-forgotten Geschenk Gaulmann continued work on the development of rockets for space exploration. Even as the military demands of World War II grew ever more pressing, Gaulmann maintained with undiminished optimism the imminent possibility of manned space flight to the moon and even the other planets, almost two decades before the US launched the Mercury program.
Only one rocket, the C-4, was ever built based on Gaulmann’s ideas, who was just 19 at the time he joined the Peenemünders. The C-4 (nicknamed “das Maul”, whether for the gaping maw of its engine bells, or its ravenous appetite for fuel and money I can only guess) was intended to be able to reach the moon, although it is unclear at this point if there was any intention or thought regarding landing on it instead of merely crashing into it. A number of innovations – a boldly large many for such an inexperienced rocket engineer – were made over its predecessors, most notably that it was the first modern-style multistage rocket to be built. This idea for a multistage rocket came from “founding father of modern rocketry” (and mentor of von Braun and Gaulmann) Hermann Oberth, who had come up with it in his youth but had at the time lacked the resources to realize it. On account of his mentor, his venturesome exploits in rocketry, and untimely end at a young age, Gaulmann is sometimes referred to as the “kid of modern rocketry”.
The first stage of the C-4 was based on the design of the then-proven V-2, though much larger and with four of the V-2’s engines instead of one. The four engines were fueled by a single turbopump, so it seems unlikely they could have ever reached the necessary fuel rates for proper performance. Gaulmann seemed to make some concession to the far greater difficulty of reaching the moon, but rather than the modern solution of more intricate staging and more efficient engines and materials, opted for the approach of more and more exotic fuels. The V-2 was fueled by “B-Stoff” (75% ethanol and 25% water), and its oxidizer was liquid oxygen (“A-Stoff”). Instead, the fuel for the C-4 was C-Stoff, a highly toxic and hypergolic mixture of methanol, hydrazine hydrate, water, and potassium tetracyanocuprate (I). C-Stoff had been engineered to work with the oxidant T-Stoff, which is 80% hydrogen peroxide with water. While T-Stoff itself is highly dangerous (“special rubberized suits were required when working with it, as it would react with most cloth, leather, or other combustible material and cause it to spontaneously combust”), this was apparently insufficient for Gaulmann who blithely substituted it with N-Stoff, pure chlorine trifluoride. The chemical is colorfully described in Derek Lowe’s Things I Won’t Work With who writes “during World War II, the Germans were very interested in using it in self-igniting flamethrowers, but found it too nasty to work with” and then quotes John Clark’s “Ignition!” for more details:
It is, of course, extremely toxic, but that’s the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water – with which it reacts explosively. It can be kept in some of the ordinary structural metals – steel, copper, aluminium, etc. – because of the formation of a thin film of insoluble metal fluoride which protects the bulk of the metal, just as the invisible coat of oxide on aluminium keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes.
So far, so good. The payload of the first stage was then, instead of a warhead, the second stage, with the warhead’s detonation mechanism repurposed to time the ignition of the second stage. (Later the US would do similarly in the V-2 sounding rocket program which replaced warheads of captured V-2s with scientific instruments.) However, the weight limitations on the second stage were so severe that after trimming it down practically to the bare metal Gaulmann even removed the oxidizer, relying on an air-breathing engine which we would now recognize as a ramjet. (In retrospect an aluminum can filled with C-Stoff is hardly so different from the warhead it replaced.)
Given the small size of the target and the difficulties of aiming the comparatively short-range V-2, Gaulmann endowed das Maul with three rows of six aerodynamic fins on the first stage and a further two rows of four fins on the second stage. Thus, compared to the V-2 and its four fins, the C-4 was a towering bladed monstrosity. Gaulmann had the nosecone painted bright red.
It may seem bold to try to fly a rocket to the moon with an air-breathing engine, but at the time of Gaulmann’s fateful experiments no scientific observations of the Earth’s upper atmosphere had been conducted, and it was believed by the Germans to extend much higher than we now know today. The C-4 was to expend its fuel while within the atmosphere, reaching sufficient velocity to fly ballistically to the halfway point from the Earth to the moon, from which it was expected to fall (due to the moon’s gravity) the rest of the way. Whether or how it was thought to match the moon’s orbital velocity is not known.
Construction of the C-4 was rushed and safe practices curtailed as the Gaulmann’s superiors in the military became impatient and unimpressed with the project. The propellent, which ordinarily would have been siloed off-site, was instead housed in a small shed near the launch platform which had previously been used by the locals as a lepidopterarium. Das Gifthaus (the poison house), as the shed came to be bluntly referred to, was littered with scores of dead moths from the noxious fumes which leaked terribly. The leaks were much aggravated by a hole Gaulmann had driven through the Gifthaus’s side for easy transfer of propellent, right through the giant mural of a moth that had adorned the lepidopterarium.
The cherry on the top of the inauspicious C-4 was its choice of payload, an unlucky horse given to Gaulmann by his grandparents for this purpose. Allegedly the horse earned this treatment by its aggressive tendency to bite anyone who would continue looking at it after it bared its teeth in warning – an ill-omen ever if there was one. Officially the choice was made as the horse massed at the calculated maximum payload size of the rocket, but I find it telling that after investing so much into the construction of the rocket, the German military was unwilling to fully commit to the folly by paying for a literal dead weight to go on top.
When it came time to test the rocket, most observers situated themselves in the regular observation tower, but Gaulmann decided to get a closer vantage point in the Gifthaus, taking advantage of the hole punched in the side. Thus in January of 1944, Gaulmann’s rocket – the rocket with the amibition to reach the moon, although in truth it lacked the delta-v to even enter low Earth orbit – was test launched. The C-4, in a fit of nominative determinism, exploded instantly. (A merciful ending for the horse, at least.) The fireball ignited the nearby Gifthaus, whose secondary explosion killed Gaulmann. Upon hearing about the death and destruction of Geschenk Gaulmann and his Maul, von Braun remarked (see e.g. from source, and also):
Lochen Sie nicht einem Gifthaus an der Motte.
from which of course we get the popular saying
Don’t look a gift horse in the mouth.
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