Pioneer 1

Pioneer 1 (also known as Able 2) was an American space probe, the first under the auspices of NASA, which was launched by a Thor-Able rocket on 11 October 1958. It was intended to orbit the Moon and make scientific measurements, but due to a guidance error failed to achieve lunar orbit and was ultimately destroyed upon reentering Earth's atmosphere. The flight, which lasted 43 hours and reached an apogee of 113,800 km (70,700 miles), was the second and most successful of the three Thor-Able space probes. Pioneer 1 was fabricated by Space Technology Laboratories, a division of Ramo-Wooldridge Corp (later TRW Inc.), and consisted of a thin cylindrical midsection with a squat truncated cone on each side. The cylinder was in diameter and the height from the top of one cone to the top of the opposite cone was . Along the axis of the spacecraft and protruding from the end of the lower cone was an solid propellant injection rocket and rocket case, which formed the main structural member of the spacecraft. Eight small low-thrust solid propellant velocity adjustment rockets were mounted on the end of the upper cone in a ring assembly which could be jettisoned after use. A magnetic dipole antenna also protruded from the top of the upper cone. The shell was composed of laminated plastic. The total mass of the spacecraft after vernier separation was , after injection rocket firing it would have been . The three-stage Thor-Able vehicle consisted of a modified Air Force Thor IRBM (liquid propellant, thrust about ) as the first stage. A liquid-propellant rocket engine powered the second stage (modified Vanguard second stage, thrust about ). The third stage was a solid-propellant unit based on Vanguard design, rated at -sec total impulse. The scientific instrument package had a mass of and consisted of an image scanning infrared television system to study the Moon's surface to a resolution of 0.5°, an ionization chamber to measure radiation in space, a diaphragm/microphone assembly to detect micrometeorites, a spin-coil magnetometer to measure magnetic fields to 5 microgauss, and temperature-variable resistors to record the spacecraft's internal conditions.