25 December 1968: During the 10th orbit of the Moon, the crew of Apollo 8 fired the Service Propulsion System (SPS) of the Command Service Module for the Trans Earth Injection (TEI) maneuver that would send them home.
TEI was a critical maneuver which had to be timed perfectly. It occurred while the spacecraft was on the side of the Moon away from Earth, and so the crew was out of radio communication with Mission Control in Houston, Texas. If initiated too soon, the Apollo capsule would miss Earth, or ricochet off the atmosphere. Too late and the capsule would re-enter too steeply and burn up.
The engine had to burn for precisely the correct amount of time to accelerate the space craft out of lunar orbit and to arrive at Earth at exactly the correct point in space where where our home planet would be 57 hours, 26 minutes, 56.2 seconds later, as it traveled in its orbit around the Sun.
The SPS engine was an AJ10-137, built by Aerojet General Corporation of Azusa, California. It burned a hypergolic fuel combination of Aerozine 50 and nitrogen tetraoxide, producing 20,500 pounds of thrust (91.19 kilonewtons). It was designed for a 750 second burn, or 50 restarts during a flight. The SPS engine had already been used for the Trans Lunar Injection maneuver, sending Apollo 8 from Earth orbit to the moon, and now served the same function in reverse.
The SPS started at mission time T+089:19:16.6 and cut off at T+089:22:40.3, a burn duration of 3 minutes, 23.97 seconds, increasing the velocity (Δv, or “delta–v”) 3,531 feet per second (1,076 meters per second).
11 October 1968: at 15:02:45 UTC, Apollo 7, the first manned Apollo spacecraft, was launched aboard a Saturn IB rocket from Launch Complex 34, Cape Kennedy Air Force Station, Cape Kennedy, Florida.
The flight crew were Captain Walter M. (“Wally”) Schirra, United States Navy, the mission commander, on his third space flight; Major Donn F. Eisele, U.S. Air Force, the Command Module Pilot, on his first space flight; and Major R. Walter Cunningham, U.S. Marine Corps, Lunar Module Pilot, also on his first space flight.
The mission was designed to test the Apollo spacecraft and its systems. A primary goal was the test of the Service Propulsion System (SPS), which included a restartable Aerojet AJ10-137 rocket engine which would place an Apollo Command and Service Module into and out of lunar orbit on upcoming missions.
The SPS engine was built by Aerojet General Corporation, Azusa, California. It burned a hypergolic fuel combination of Aerozine 50 (a variant of hydrazine) and nitrogen tetraoxide, producing 20,500 pounds of thrust. It was designed for a 750 second duration, or 50 restarts during a flight. This engine was fired eight times and operated perfectly.
The duration of the flight of Apollo 7 was 10 days, 20 hours, 9 minutes, 3 seconds, during which it orbited the Earth 163 times. The spacecraft splashed down 22 October 1968, approximately 230 miles (370 kilometers) south south west of Bermuda in the Atlantic Ocean, 8 miles (13 kilometers) from the recovery ship, the aircraft carrier USS Essex (CVS-9).
The Apollo command module was a conical space capsule designed and built by North American Aviation to carry a crew of three on space missions of two weeks or longer. Apollo 7 (CSM-101) was the first Block II capsule, which had been extensively redesigned following the Apollo 1 fire which had resulted in the deaths of three astronauts. The Block II capsule was 10 feet, 7 inches (3.226 meters) tall and 12 feet, 10 inches (3.912 meters) in diameter. It weighed 12,250 pounds (5,557 kilograms). There was 218 cubic feet (6.17 cubic meters) of livable space inside.
The Saturn IB consisted of an S-IB first stage and an S-IVB second stage. The S-IB was built by Chrysler. It was powered by eight Rocketdyne H-1 engines, burning RP-1 and liquid oxygen. Eight Redstone rocket fuel tanks containing the RP-1 fuel surrounded a Jupiter rocket tank containing the liquid oxygen. Total thrust of the S-IB stage was 1,600,000 pounds and it carried sufficient propellant for 150 seconds of burn. This would lift the vehicle to an altitude of 37 nautical miles (69 kilometers).
The Douglas-built S-IVB stage was powered by one Rocketdyne J-2 engine, fueled by liquid hydrogen and liquid oxygen. The single engine produced 200,000 pounds of thrust and had enough fuel for 480 seconds of burn.
The Saturn IB rocket stood 141 feet, 6 inches (43.13 meters) without payload. It was capable of launching a 46,000 pound (20,865 kilogram) payload to Earth orbit.
12 August 1960: At 5:39:43 a.m., Eastern Daylight Savings Time, the Echo 1A experimental passive communications satellite was launched from LC-17A at Cape Canaveral Air Force Station, Florida. The launch vehicle was a Thor-Delta three stage rocket. It entered a nearly circular 944 mile × 1,048 mile orbit (1,519 × 1,687 kilometers). The orbital period was 118.3 minutes.
The satellite was a 100 foot diameter (30.48 meter) Mylar polyester balloon with a reflective surface. The material was just 0.0127 millimeters thick. The mass of the satellite was 66 kilograms (145.5 pounds). In orbit, the balloon envelope was kept inflated by gas from evaporating liquid. It had been constructed by the G.T. Schjeldahl Company, Northfield, Minnesota. This was the second Echo satellite. The first had failed to reach orbit when launched 13 March 1960.
Later the same day, a microwave transmission from the Jet Propulsion Laboratory, Pasadena, California, was reflected off the Echo 1A satellite and received at the Bell Laboratories, Homdel, New York.
According to NASA, “The success of Echo 1A proved that microwave transmission to and from satellites in space was understood and demonstrated the promise of communications satellites. The vehicle also provided data for the calculation of atmospheric density and solar pressure due to its large area-to-mass ratio. Echo 1A was visible to the unaided eye over most of the Earth (brighter than most stars) and was probably seen by more people than any other man-made object in space.”
Echo 1A remained in Earth orbit until 24 May 1968.
The Delta was a three-stage expendable launch vehicle which was developed from the Douglas Aircraft Company’s SM-75 Thor intermediate-range ballistic missile.
Designated Thor DM-19, the first stage was 60.43 feet (18.42 meters) long and 8 feet (2.44 meters) in diameter. Fully fueled, the first stage had a gross weight of 108,770 pounds (49,337 kilograms). It was powered by a Rocketdyne LR-79-7 engine which burned liquid oxygen and RP-1 (a highly-refined kerosene rocket fuel) and produced 170,565 pounds of thrust (758.711 kilonewtons). This stage had a burn time of 2 minutes, 45 seconds.
The second stage was an Aerojet General Corporation-built Delta 104. It was 19 feet, 3 inches (5.88 meters) long with a maximum diameter of 4 feet, 6 inches (1.40 meters). The second stage had a gross weight of 9,859 pounds (4,472 kilograms). It used an Aerojet AJ10-104 rocket engine which burned a hypergolic mixture of nitric acid and UDMH. The second stage produced 7,890 pounds of thrust (35.096 kilonewtons) and burned for 4 minutes, 38 seconds.
The third stage was an Alleghany Ballistics Laboratory Altair 1. It was 6 feet long, 1 foot, 6 inches in diameter and had a gross weight of 524 pounds (238 kilograms). This stage used a solid-fuel Thiokol X-248 rocket engine, producing 2,799 pounds of thrust (12.451 kilonewtons). Its burn time was 4 minutes, 16 seconds.