When the US Navy finally solved its problems with the Vanguard launcher programme, and succeeded in launching the Vanguard 1 satellite (on 17 March 1958, some 5 months behind Sputnik 1), it was a cause for celebration in the homeland. However, at 16 cm in diameter and 1.5 kg in weight, it was even smaller than and not one-fifth the mass of Explorer 1. Considering that Sputnik 2 had been more than 300 times heavier, the spherical Vanguar d 1 nicknamed the grapefruit by Soviet Premier Khrushchev ^[27] was a political gift to the Soviets (Figure 3.5).

Figure 3.4: Simulation of Earth's Van Allen radiation belts generated by a plasma thruster at NASA's Lewis Research Center [NASA]

Figure 3.5: Vanguard 1, the grapefruit , showing solar cells [NASA]

Nevertheless, Vanguard 1 represented a significant advance from the engineering point of view, in being the first satellite to derive its power from solar cells. The first practical photovoltaic cell had been developed at AT&T's Bell Telephone Laboratories in 1954 and Vanguard 1 presented the first opportunity to fly it in space. The 34 cells were mounted behind six tiny protective windows spaced around the sphere, and produced just 10 m W of DC (direct current) power ^[28]. At the time, these groups of cells and their accompanying rechargeable batteries were termed solar batteries . The term arose because, in the early days of the Space Age, the majority of launch vehicle and spacecraft power was derived from non-rechargeable batteries, and the...