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Goddard’s proposals were met with disbelief and ridicule. In response he became secretive about his plans, worked only with a small team of trusted people and hid his experiments from the public. Often not even his close associates knew exactly what he was up to. Like Tsiolkovsky, Goddard reahzed that rockets based on liquid propellants have several advantages over the simpler solid propellant (gunpowder) rockets used until then for artillery and fireworks. Liquid propellant rockets have a lower weight relative to their thrust and, unlike solids, can be throttled up or down, and even stopped entirely without blowing up. So Goddard began to experiment with liquid propellants and in 1926 flew the world’s first liquid propellant rocket (running on gasohne and liquid oxygen); an event now recognized as historic even though at the time virtually no one knew about it.

Goddard also gave some thought to rocket planes, leading in 1931 to a patent for an especially innovative design. Observing that rocket motors are not very efficient in the lower atmosphere, he proposed that his rocket plane would start off by using the exhaust from its rocket engine to drive a pair of turbines each of which would be connected to a conventional propeller. At higher altitudes the turbine blades would be withdrawn from the path of the hot gas and the plane would fly on rocket thrust alone. The turbines would have had to be made from heat-resistant materials that far exceeded the capabilities of the time, but the general idea was sound and similar to what we call today a turboprop engine. The concept of dual-mode propulsion was also very innovative and would become a feature of advanced spaceplane concepts half a century later (although not involving propellers). In his book The Conquest of Space, the first non-fiction book on spaceflight in English, American David Lasser foresaw fleets of Goddard’s planes connecting London, Paris and Berlin with New York by 1950. Flight time: 1 hour! The general public nevertheless kept ignoring Goddard’s important work, probably wrongly associating it with the fanciful stories that featured in the popular science fiction pulp magazines of the time. After one of his rocket experiments in 1929, a mocking headline in a local Worcester newspaper read “Moon rocket misses target by 238,799 1/2 miles”. By 1935 Goddard’s rockets had exceeded the speed of sound and reached altitudes of 1.5 km (0.9 miles), but the US government did not seem to appreciate the possibilities of this novel technology. During the Second World War Goddard was only assigned a contract to develop rockets to assist propeller aircraft take off from carrier ships.

In Germany the situation was very different. The rocket experiments of a small club of hobbyists, inspired by their own rocket pioneer Hermann Oberth, attracted serious attention from the military. German Army leaders saw the development of powerful rockets as a means of circumventing the ban on the use of large cannon as stipulated in the Treaty of Versailles that Germany had been forced to sign after its defeat in the First World War. Under the technical leadership of the German Space Society’s Wemher von Braun, who was only 20 years old at time, the Army began an enormous rocket development effort. It soon became the Third Reich’s most expensive development project. A dedicated and huge development and launch center was built in Peenemiinde, a remote and sparsely inhabited place on the Baltic shore, involving laboratories, wind tunnels, test stands, launch platforms and housing facilities for the 2,000 rocket scientists, 4,000 supporting workers and their

families. Peenemtinde’s vast resources enabled the team ultimately to develop the infamous A4 rocket; a 14 meter (46 feet) tall monster capable of throwing a 738 kg (1,630 pound) warhead a distance of 418 km (260 miles). In 1942, on its first flight, and A4 (without an explosive cargo) climbed to an altitude of over 80 km (50 miles) and thus became the first man-made vehicle to reach the edge of space. In a speech afterwards, Walter Dornberger, head of the rocket development program, observed: “This third day of October, 1942, is the first of a new era in transportation, that of space travel…”

But spaceflight was not what the rocket was developed for. It was a weapon and, renamed Y2 for ‘Vergeltungswaffe 2’ (Retaliation weapon number 2), at least 3,000 were fired at London and Antwerp towards the end of the war, blowing away entire blocks of houses in an instant. Although impressive and scary, the A4 was however not a huge success as a weapon. For one, it was a very expensive means of dropping a 738 kg bomb on a city in a neighboring country, and not a very precise one at that. The ‘terror’ effect of the rocket striking without warning (because it flew faster than sound it could not be heard before impact) did not have the effect that Hitler hoped for either: Londoners did not panic en masse, and did not desperately demand their government negotiate an armistice with Nazi Germany. In retrospect it would have been better to use the money that went into developing and producing the V2 to buy advanced jet fighters like the Messerschmitt Me 262. Although the A4/Y2 failed to change the outcome of the war, it demonstrated the future of big rockets as ballistic missiles. More importantly for von Braun and other space enthusiasts, it proved that a rocket could reach space and with further development would be able to launch a satellite into orbit in the foreseeable future.

By the end of the war rockets had reached such a high maturity that they could be used to propel operational planes. The rocket engines of the time were powerful and yet less complicated than turbojet engines, so if you needed to get an airplane up and high as fast as possible with a relatively simple power plant, a rocket engine was the obvious choice. In America the Air Force attached rocket pods to heavy cargo planes to help them to take off, but in Germany real rocket fighters were put into operation to counter high flying bombers. While it took a conventional high altitude propeller interceptor such as Focke Wulf s Fw 190D-9 some 17 minutes to climb to bombers at altitudes of up to 10 km (6 miles), the revolutionary Me 163 ‘Komet’ (German for Comet) rocket plane could do it in just under 3 minutes! Even the Me 262 jet fighter took 10 minutes to climb that far. The Me 163 was the fastest aircraft of the Second World War: at top speed, the little rocket interceptor closed in on the Allied bombers at about 960 km per hour (590 miles per hour), allowing the defending gunners no chance to take aim at it. The Komet also outran the propeller – driven escort fighters, so there was essentially no defense against the little rocket plane during its powered attack. Only when it ran out of propellant and had to glide back to its base could the Me 163 be intercepted and destroyed.

Serious plans for launching rocket planes into space also began to be developed during the Second World War, starting with Eugen Sanger’s design for a bomber to strike New York. This ‘Silbervogel’ (Silverbird) would begin its mission by riding a large rocket sled on a rail track over a distance of about 3 km (2 miles). On firing its own rocket engine it would climb into space, its altitude peaking at around 145 km (90 miles). It would fly below orbital speed, slowly descending into the stratosphere until the increasingly denser air would generate sufficient lift to ‘bounce’ the plane up again. Thus the Silbervogel would hop around the planet in the same manner as a stone skipping across a pond. It was calculated that the rocket plane would be able to take off from Germany, cross the Atlantic, drop a small bomb on the USA and land somewhere in Japanese occupied territory in the Pacific. It wouldn’t be a real orbital spaceplane, but pretty close. Fortunately, Germany had no time to develop anything like this before the war ended, and even if they had it would not have worked: later analysis showed that the heat generated by re-entry into the atmosphere would have destroyed the Silbervogel in its original design. Additional heat shields might have saved the concept, but the associated extra weight would have cut the bomb load to zero. Certainly it would have been difficult to justify the vast effort and expense to develop the Silbervogel simply to drop the equivalent of a hand grenade on the US. Even its designer reckoned it would take decades to get the Silbervogel operational. But the idea of a rocket propelled space bomber would return later, even leading to concern in the Soviet Union that the NASA Space Shuttle was actually a disguised orbital bomber with heat shielding that would enable it to make shallow dives into the atmosphere to deploy nuclear bombs!

During the 1940s and 1950s many technological fields experienced radical and rapid advances, in particular aviation: jet aircraft replaced piston-engined propeller planes, and ballistic missiles quickly made strategic bombers all but obsolete. The amazingly fast progress in rocket and aircraft development led to series of rocket aircraft that repeatedly broke altitude and speed records. In October 1947 test pilot Chuck Yeager managed to get the little Bell X-l rocket plane to fly faster than the speed of sound (Mach 1), thereby breaking the so-called ‘sound barrier’ (or rather, discovering there was no such barrier). In 1953 Scott Crossfield became the first to exceed Mach 2 in the Douglas D-558-2 Skyrocket. Three years later Milburn ‘Mel’ Apt pushed the Bell X-2 to the next magic number of Mach 3. Shortly before Apt’s flight, Iven Kincheloe became the first pilot ever to climb above 100,000 feet, as he flew the X-2 to a peak altitude of 126,200 feet (38,5 km, or 23.9 miles).

The complexity of the aircraft had increased enormously in the quarter century that separated the first rocket propelled gliders to the Bell rocket research aircraft: while the Opel RAK-1 had required only a few simple readiness checks shortly in advance of the launch, the Bell X-l A pilot had a checklist of 197 points to tick off prior to flight. By 1962, test pilots were flying at speeds over Mach 6, and earning their ‘astronaut wings’ by reaching altitudes of 80 km (50 miles) and even higher in the incredible North American X-l5; the US Air Force designates people who travel above an altitude of 50 miles as astronauts, although the International Aeronautical Federation (Federation Aeronautique Internationale, FAI) defines the boundary of space at 100 km (62 miles). Many therefore saw the rocket spaceplane as the logical progression of aviation into space, as had Valier, Tsiolkovsky and Goddard thirty years earlier.

But based on the design of the A4/V2 and insight gained from the Peenemunde experts captured after the war, the US and the USSR had by then both developed an arsenal of intercontinental ballistic missiles. The multi-stage rocket technology used to lob a nuclear warhead halfway around the Earth had reached a very high level of maturity, and laid the basis for a much faster and easier road into orbit which all but suspended the development of rocket spaceplanes. Simply put, the warheads were removed and replaced with satellites and manned capsules. Of course these missiles were not reusable, but in the Moon Race of the 1960s money and sustainability were not the most important issues. Instead of the Silbervogel or similar rocket plane, the ultimate space machine thus became the enormous Saturn V rocket. It boosted Neil Armstrong and Buzz Aldrin to the Moon, in the process beating the Russians in the technological and political space race that had started with the launch of the world’s first satellite by the Soviets in October 1957. Although the ultimate launch vehicle in terms of its capability, the Saturn V was also an extremely wasteful transport vehicle:

excluding the actual payload, the total weight of the 111 meter (363 feet) rocket was some 2,896,000 kg (6,384,000 pounds), 94 percent of which consisted of propellant. At 47 tons (104,000 pounds), the Apollo spacecraft and lunar lander represented less than 2 percent of the entire vehicle that lifted off from the launch pad, and 187 tons (412,000 pounds) of precious hardware was lost by the time the astronauts arrived in lunar orbit; the Saturn Y first stage fell into the ocean, the second stage burned up falling back into the atmosphere, and the third stage went into an orbit around the Sun or crashed on the Moon. Corrected for inflation, in 2011 economic conditions a Saturn V would have cost $2.9 billion per launch, which translates to nearly a billion dollars per astronaut. And for that they were only flying tourist class, with poor food and hardly any leg room. It got you to the Moon and made an impressive amount of noise and smoke doing so, but a Saturn Y was clearly not an economical means of transportation. Good for winning a race, but not for the large-scale economic use of Earth orbit and beyond.