Tag Archives: Thor DM-18A

1 April 1960, 11:40:09 UTC, T minus Zero

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TIROS-1/Thor-Able 148 launches from Launch Complex 17A at Cape Canaveral, Florida, 11:40:09 UTC, 1 April 1960. (NASA)

1 April 1960: TIROS-1, the first successful Earth-orbiting weather satellite, was launched at 6:40:09 a.m. (11:40:09 UTC), from Launch Complex 17A at the Cape Canaveral Air Force Station, Cape Canaveral, Florida, aboard a Thor-Able II liquid-fueled rocket. The satellite’s name is an acronym for Television Infra Red Observation Satellite.

The satellite was placed into a nearly-circular low Earth orbit with an apogee of 417.8 miles (672.4 kilometers) and perigee of 396.2 miles (637.6 kilometers). It is still in orbit and circles the Earth once every 1 hour, 37 minutes, 42 seconds. TIROS-1 remained operational for 78 days. It is still in orbit.

“TIROS undergoes vibration testing at the Astro-Electronic Products Division of RCA in Princeton, New Jersey.” (NASA)

TIROS-1 was built of aluminum and stainless steel. It had a diameter of 3 feet, 6 inches (1.067 meters) and height of 1 foot, 7 inches (0.483 meters.) The satellite weighed 270 pounds (122.47 kilograms). Two television cameras were installed on the satellite. They received electrical power from storage batteries charged by 9,200 solar cells. Images were stored on magnetic tape, then transmitted when in range of a ground receiving station. The first image, which showed large-scale cloud formations, was transmitted the day of the launch.

Technicians mount the TIROS-1 weather satellite to the Thor-Able upper stage carrier. (NASA)

The launch vehicle, Thor 148, consisted of a liquid-fueled Douglas Aircraft Company Thor DM-18A first stage (based on the SM-75 intermediate range ballistic missile) and an Aerojet Able-II second stage, which was developed from the Vanguard rocket series. The Thor-Able was 91 feet (27.8 meters) tall and 8 feet (2.44 meters) in diameter. It weighed 113,780 pounds (51,608 kilograms). The first stage was powered by a Rocketdyne LR79-7 rocket engine which burned RP-1 and liquid oxygen. The engine produced 170,560 pounds of thrust (758.689 kilonewtons) and burned for 165 seconds.

The Able-II second stage was powered by an Aerojet AJ-10 engine which produced 7,800 pounds of thrust (34.696 kilonewtons). The propellant was a hypergolic combination of nitric acid and UDMH (hydrazine). It burned for 115 seconds.

There were sixteen Thor-Able two-stage rockets launched. TIROS-1 was placed in orbit by the last of that series.

The first television image of Earth, transmitted by TIROS-1, 1 April 1960. (NASA)
The first television image of Earth, transmitted by TIROS-1, 1 April 1960. The image shows Maine, Nova Scotia, the Gulf of St. Lawrence and the Atlantic Ocean. (NASA)

© 2019, Bryan R. Swopes