(28) Spaceflight

The Missile Race

The end of World War II came in 1945, when Hiroshima and Nagasaki, two Japanese cities, were each destroyed by a single atomic bomb. Rocketry suddenly took on a new, terrifying image. The 1-ton payload of the German V2 only caused limited damage: it was an unstoppable terror weapon, but strategically insignificant. Now that destructive power could be increased 20,000 times. Ten years later, when the H-bomb was perfected, that ratio climbed into the millions.

This realization, in the years after World War II, turned the military into a major supporter of rocket development, especially in the US and in the USSR, the Soviet Union (now the Russian republic and its allies). Though many people still dreamt of exploring space, the support money--for a while at least--went to the development of missiles.

 Sergei Korolev

The early military rockets were actually quite adaptable to scientific uses. The military sought "Intercontinental Ballistic Missiles" (ICBMs) able to hit any point on Earth, and for this they had to be able to impart a velocity very close to the one needed to achieve an orbit above the atmosphere. Both the US and the USSR concentrated on liquid-fueled rockets. The US captured a fair number of usable V2s, as well as the German rocket-design team headed by Wernher von Braun, who soon took a key role in the development of US missiles. The USSR also captured V2 engines, and Russian rocket designers, headed by Valentin Glushko and Sergei Korolev ("Koralyov") duplicated those rockets and then went on to develop their own, more powerful designs.

In the US these efforts led to the Thor and Jupiter rockets with a range of the order of 2000-3000 km, and to the Atlas, whose range was indeed intercontinental. At the same time a series of scientific rockets was developed from JPL's "Corporal", namely the Aerobee for studies of the upper atmosphere and the Viking, a larger vehicle. More limited development projects for missiles and scientific rockets took place in Britain and France.

The International Geophysical Year

Scientific rockets made possible, for the first time, studies of high altitude phenomena and observations of the Sun in ultra-violet wavelengths, usually blocked by the atmosphere. Among those active here was James Van Allen, who in the late 1940s sent Geiger counters, detectors of fast ions and electrons, to high altitudes aboard Aerobee and V2 rockets. Aware that rockets wasted a great deal of energy overcoming air resistance, he and his team at the University of Iowa later suspended small scientific rockets from high-altitude balloons and fired them by remote control once they were above the bulk of the atmosphere. In 1953 one such rocket was fired into the polar aurora ("northern lights"--more details here) and observed a large incoming flow of fast particles, later identified as electrons.

By international agreement 1957-8 was declared as the "International Geophysical Year" (IGY), a time for special international efforts to study the solid Earth, the ocean, atmosphere and the Earth's space environment. The US announced that it planned to launch at that time a small satellite with a radio beacon, the "Vanguard", using a multi-stage rocket based on the Viking technology. Unofficially Von Braun also prepared a military rocket for launching a satellite, which Van Allen's group at the University of Iowa provided, but he was not permitted to do so ahead of the official Vanguard mission.

Sputnik

 Korolev's R-7 "Semiorka"
 rocket, similar to the one that
 launched the Sputniks.

The USSR also announced its intention of launching artificial Earth satellites during the IGY, but the US and its allies did not take that announcement seriously. They were unaware of the long development of Russian long-distance rockets, leading to Korolev's R7 rocket, the Semiorka ("little number seven"), a huge vehicle powered by 20 rocket engines. It was not only a very effective launcher, but also rather beautiful to behold: four tapered first-stage rockets, each with a cluster of 4 engines, surrounding the main vehicle which was powered by a cluster of its own.

On October 7, 1957, that rocket inserted the first USSR "sputnik" (= satellite) into a circular orbit above the atmosphere, causing a great commotion throughout the world. Sputnik was seen as a challenge to the US technology, as well as evidence of Soviet missiles with intercontinental range. Not only did the US hurry up its own launch plans, but it reassessed the science education program of its schools and other underpinnings of advanced technology. A month later the USSR launched Sputnik 2, which carried a dog named Laika, proving that living beings could fly into space and survive.

The US tried but failed to launch its Vanguard satellite on December 6, 1957. The margin of extra lifting power of the Vanguard's first stage was rather small, and in the critical first seconds it did not rise fast enough to safely lift the rocket off the pad; instead the rocket toppled and burned. Today all space launches employ clamps to hold the rocket down during those seconds, until full thrust is achieved; if you ever watch the countdown of a spaceflight launch, you might note that "ignition" comes a short instant before "lift-off. " It wasn't so in the early days. Later launches of "Vanguard" lifted off successfully, but it was the 1957 failure that is remembered.

Explorers 1 and 3

 Launch of Explorer 1

In view of the success of Sputnik and the failure of Vanguard, Braun's launch plan was given the go-ahead, and on January 31, 1958, it orbited the first successful US satellite, Explorer 1 (launch picture on right). Aboard it was Van Allen's Geiger counter, and a similar spacecraft, Explorer 3, followed it in March (Explorer 2 failed).

Van Allen had planned to observe the cosmic radiation, high-speed ions (atoms stripped of electrons) from the distant universe. In particular, it sought to measure the flow of cosmic ray ions of the lowest energies, which are completely absorbed by the atmosphere and therefore cannot be studied from the ground (the recent Sampex mission studied such particles, with much better instruments). Unlike the orbits of the Sputniks, that of Explorer 1 was quite elliptic, rising to altitudes above 2000 km.

At the higher altitudes, strangely, the rate of cosmic ray particles recorded by the Geiger counter dropped to zero. The reason was found by Explorer 3, which showed that at the higher elevation the actual radiation was so high that the instrument became overloaded. This way was discovered the belt of "trapped radiation" (that is, of trapped ions and electrons) extending around the Earth, held by the Earth's magnetic field.


Next Stop: #29 Spacecraft



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Author and curator: David P. Stern
Last updated 3 April 1999


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