Sunday, February 23, 2014

Vanguard & Other Fruit Sized Satellites, Part I

Vanguard 1 - actually, a bit larger than a grapefruit.
Drawing by Robert R. Little

The first official civilian satellites designed by the United States, the Vanguard series, were small. Very small, in fact. The first one to orbit, Vanguard 1, was a mere 6.4" (165 mm) in diameter, and was 3.2 lbs (1.45 kg) in mass. Soviet premier Nikita Kruschev derisively referred to the American satellite as a "grapefruit".
He had room to brag, in a way.
The first satellite to be orbited was Soviet, Sputnik 1. It was launched atop a powerful R-7 rocket, a launcher that would remain something of a mystery in the west until the 1967 Paris Air Show. Sputnik 1 was actually a provisional design itself. The Soviets wanted the satellite that would be known as Sputinik 3 to be the first. But at over 2,900 lbs (1315 kg), it was going to be a bit challenging. 
Still, even the "Простейший Спутник", Sputnik 1, was much larger than the US Vanguard. Sputnik 1 was 23 inches (58 cm) in diameter, and had a mass of 184 lbs (83.6 kg). 
It was nonetheless no more capable than Vanguard 1.
Even the first American satellite to orbit, Explorer 1, was much larger than Vanguard, and carried a fairly sophisticated suite. It was over 30.8 lbs (13.37 kg) and was 6' 8.75" (2.05 meters) long. 
What set the Explorer and those Sputniks apart from the first Vanguard was not their size, but their launchers. The Sputniks used the R-7 series, which still fly today as the Soyuz series. This rocket was powerful enough that on the Sputnik 1 launch the second stage, which is essentially the rocket core, went into orbit behind the PS-1 (which is what most people were actually seeing orbiting, not Sputnik 1). The modified Redstone that carried the American Explorer 1 into orbit, the Juno I (an improved Jupiter-C), was still a fairly good sized rocket, though was little more than an evolved V-2/A-4. As it turned out, the Soviets also had these lineal descendants of the V-2 on hand, but the R-7, while somewhat troublesome, was more than enough rocket for the job.
The Vanguard, on the other hand, was being launched on its own specialized launcher, also named Vanguard. It was much smaller than the Redstone, and far smaller than the R-7. It produced a modest 30,303 lbs (134.79 kilo-Newton) of thrust, and was 75 feet (23 meters) tall. It was slender, looking every bit like the sounding rockets it evolved from. 
It was simply a hard push by the Soviets that put them ahead. While the Vanguard satellite looked promising, its launcher was not.

On December 6th, 1957, the TV-3 launch vehicle lifted a short distance off the pad, only to collapse back into a fireball. 
On national television.
It does say something about the design of the Vanguard satellite that after the explosion it was found on the ground, transmitting away. 
Out of a total of eleven satellite launch attempts, eight would fail. The first successful Vanguard launch would be on the March 17th, 1958, over five months after the Soviets launched Sputnik 1.
Incredibly, the last two Vanguards to be orbited, Vanguard 2 & 3, were only slightly smaller than Sputnik 1, though close to half its mass. Even more incredibly, unlike their larger Soviet counterpart, all three Vanguard satellites, as well as some of their upper stages, remain in orbit. The little grapefruit (really, more like cantaloupe) sized Vanguard 1 will likely remain in orbit for another 150 years, while its two descendants still have perhaps as many as 250 yet to go.

Most of the early civilian American satellite and probe designs were fairly small. This is partially a function of the rockets that were available for them. There was a secret program to orbit spy satellites, WS-117, which would eventually evolve into Corona, and these were much larger satellites. With the launch of the large Soviet satellites, one of the questions troubling many was answered; overflight rights. With civilian satellites of small size, it was hoped that could be circumvented. When the first flights began in earnest, it was apparent that size didn't really matter. While the Russians orbited the entire second stage/core of an R-7 with the launch of Sputnik 1, it would be no time at all before the US showed it could do the same with Project SCORE, on December 18th, 1958. For that mission, an entire Atlas-B rocket was placed into orbit. 
It demonstrated that we could do the same, though not much else, aside from broadcasting a tape recorded message by President Eisenhower.
Many of the smaller civilian satellites were already in the works by this point, and had to rely on the retinue of Juno I, Juno II, and Thor-derived launchers. By 1961, a slender new solid fuel rocket, the Scout, began launching small satellites and probes. There were still plenty of smaller satellites that would be launched, but the availability of larger rockets, such as the various Atlas and Thor derivatives, meant that larger payloads could be carried aloft. Smaller experiments could be bundled in with these larger one, added to them, but fewer could be carried aloft as lone projects. 
In time, those smaller satellites would make something of a return, though in unusual ways.

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