Explorer S-1, also known as NASA S-1 or Explorer 7X, was a

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

Earth science Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres ...

satellite equipped with a suite of scientific instruments to study the environment around the

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

. The spacecraft and its

Juno II Juno II was an American space launch vehicle used during the late 1950s and early 1960s. It was derived from the Jupiter missile, which was used as the first stage. Development Solid-fueled rocket motors derived from the MGM-29 Sergeant we ...

launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...

were destroyed five seconds after launch on 16 July 1959, in a spectacular launch failure caused by complications with the launch vehicle's power supply. A relaunch of the mission in October 1959,

Explorer 7 Explorer 7 was a NASA satellite launched on 13 October 1959, at 15:30:04 GMT, by a Juno II launch vehicle from Cape Canaveral Air Force Station (CCAFS) to an orbit of and inclination of 50.27°. It was designed to measure solar X-ray and ...

(S-1A), was successful.

Mission

The mission was planned to be the sixth flight of the Explorer program, designated NASA S-1 and Explorer 7X retrospectively. The objectives of the mission were to measure the Earth's radiation balance, and the abundance of

Lyman-alpha Lyman-alpha, typically denoted by Ly-α or Lyα, is a spectral line of hydrogen (or, more generally, of any one-electron atom) in the Lyman series. It is emitted when the atomic electron transitions from an ''n'' = 2 orbital to the gro ...

X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

s and

cosmic ray Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the ...

s, including heavy primary cosmic rays. The spacecraft was also designed as a test bed for satellite capabilities, being equipped with instruments to measure the spacecraft's temperature,

micrometeorite A micrometeorite is a micrometeoroid that has survived entry through the Earth's atmosphere. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more abundant, and different in composition. T ...

impacts and the erosion of

solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

s exposed to the vacuum of space. The spin-stabilized spacecraft was in size, and had a launch mass of . The spacecraft's power was drawn from a bank of fifteen nickel–cadmium batteries recharged by 3,000 solar cells mounted on the exterior of the spacecraft.

Launch

The spacecraft was mounted atop a Juno II launch vehicle with the serial AM-16. It was launched on 16 July 1959, at 16:37:03 GMT, from

Cape Canaveral Launch Complex 5 Cape Canaveral Launch Complex 5 (LC-5) was a launch site at Cape Canaveral Space Force Station, Florida used for various Redstone and Jupiter launches. It is most well known as the launch site for NASA's 1961 suborbital Mercury-Redstone 3 fligh ...

(LC-5). Immediately after liftoff, a

short circuit A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit ...

of the launch vehicle's guidance system caused the

Rocketdyne S-3D The Rocketdyne S-3D (Air Force designation LR79) is an American liquid rocket engine produced by Rocketdyne (a division of North American Aviation) between 1956 and 1961. It was a gas generator, pump-fed engine, using a liquid oxygen ( LOX) and ...

engines to

gimbal A gimbal is a pivoted support that permits rotation of an object about an axis. A set of three gimbals, one mounted on the other with orthogonal pivot axes, may be used to allow an object mounted on the innermost gimbal to remain independent of ...

, tilting the rocket sharply to the west before almost flipping upside down. Five-and-a-half seconds after launch, the

Range Safety Officer In rocketry, range safety or flight safety is ensured by monitoring the flight paths of missiles and launch vehicles, and enforcing strict guidelines for rocket construction and ground-based operations. Various measures are implemented to protect ...

destroyed the launch vehicle. The launch vehicle's payload impacted the ground northwest of the launch site, resulting in a massive fireball.

Aftermath

In an investigation conducted after the launch failure, it was found that the short circuit occurred between two diodes in the launch vehicle's power supply inverter voltage regulator, cutting off power to the guidance system and causing a full gimbal. Circuit board designs for the Juno II, and similar launch vehicles, subsequently used

conformal coating Conformal coating is a protective, breathable coating of thin polymeric film applied to printed circuit boards (PCBs). Conformal coatings are typically applied with 25–250 μm thickness on electronic circuitry to protect against moisture and ...

to reduce the chances for a recurrence. The launch, described by commentators as "infamous" and "one of the most spectacular failures ever seen at ape Canaveral, was the third of the Juno II launch vehicle, after it failed to carry ''

Pioneer 3 Pioneer 3 was a spin-stabilized spacecraft launched at 05:45:12 GMT on 6 December 1958 by the U.S. Army Ballistic Missile Agency in conjunction with NASA, using a Juno II rocket. This spacecraft was intended as a lunar probe, but failed to go pa ...

'' into

heliocentric orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun ...

in December 1958, but succeeded in the same objective in March 1959, carrying the United States' first interplanetary mission, ''

Pioneer 4 Pioneer 4 was an American spin-stabilized uncrewed spacecraft launched as part of the Pioneer program on a lunar flyby trajectory and into a heliocentric orbit making it the first probe of the United States to escape from the Earth's gravity. ...

''. ''S-1'' was the first

geocentric orbit A geocentric orbit, Earth-centered orbit, or Earth orbit involves any object orbiting Earth, such as the Moon or artificial satellites. In 1997, NASA estimated there were approximately 2,465 artificial satellite payloads orbiting Earth and 6,21 ...

launch attempt for the launch vehicle; its second attempt on 14 August 1959, carrying the '' Beacon 2'' inflatable sphere experiment to

low Earth orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...

, also failed. Eventually, both the Juno II and a re-launch of the ''S-1'' mission, designated

or S-1A, found success on 13 October 1959. The satellite, which ended its mission in August 1961, is still orbiting the Earth today.

References

External links

Footage of the ''S-1'' launch
narrated by Dave Mohr on YouTube {{Orbital launches in 1959 Spacecraft launched in 1959 Satellite launch failures Explorers Program

Mission

Launch

Aftermath

See also

References

External links