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America’s First Satellite

Fifty-six years ago this week, the United States successfully orbited the country’s first satellite.  Known as Explorer I, the artificial moon went on to discover the system of radiation belts that surrounds the space environment of the Earth.

The Explorer I satellite was designed and fabricated by the Jet Propulsion Laboratory (JPL) under the direction of Dr. William J. Pickering. The satellite’s instrumentation unit measured 37.25 inches in length, 6.5 inches in diameter, and had a mass of only 18.3 lbs. With its burned-out fourth stage solid rocket motor attached, the total on-orbit mass of the pencil-like satellite was 30.8 lbs.

Explorer I was launched aboard a Jupiter-C (aka Juno I) launch vehicle from LC-26 at Cape Canaveral, Florida on Friday, 31 January 1958. Lift-off at occurred at 22:48 EST (0348 UTC).  With all four stages performing as planned, Explorer I was inserted into a highly elliptical orbit having an apogee of 1,385 nm and a perigee of 196 nm.

Arguably the most historic achievement of the Explorer I mission was the discovery of a system of charged particles or plasma within the magnetosphere of the Earth. These belts extend from an altitude of roughly 540 to 32,400 nm above mean sea level. Most of the plasma that forms these belts originates from the solar wind and cosmic rays. The radiation levels within the Van Allen Radiation Belts (named in honor of the University of Iowa’s Dr. James A. Van Allen) are such that spacecraft electronics and astronaut crews must be shielded from the adverse effects thereof.

Explorer I operational life was limited by on-board battery life and lasted a mere 111 days. However, it soldiered-on in orbit until reentering the Earth’s atmosphere over the Pacific Ocean on Tuesday, 31 March 1970. During the 147 months it spent in space, Explorer I orbited the Earth more than 58,000 times. Data obtained and transmitted by the satellite contributed markedly to mankind’s understanding of the Earth’s space environment.

Perhaps the greatest legacy of Explorer I was that it was the first satellite orbited by the United States. Unknown to most today, this accomplishment was absolutely vital to America’s security, and indeed that of the free world, at the time. The Soviet Union had been first in space with the orbiting of the much larger Sputnik I and II satellites in late 1957. However, Explorer I showed that America also had the capability to orbit a satellite. History records that this capability would quickly grow and ultimately lead to the country’s preeminence in space.

Posted in Aerospace, History

Surveyor 7

Forty-six years ago this month, the Surveyor 7 spacecraft soft-landed in the lunar highlands near the Crater Tycho. It was the fifth and final Surveyor vehicle to successfully perform an autonomous landing on the surface of the Moon.

In preparation for the first manned lunar landing, the United States conducted an extensive investigation of the Moon using Ranger, Lunar Orbiter and Surveyor robotic spacecraft.

Ranger provided close-up photographs of the Moon starting at a distance of roughly 1,100 nautical miles above the lunar surface all the way to impact. Nine (9) Ranger missions were flown between 1961 and 1965. Only the last three (3) missions were successful.

Lunar Orbiter spacecraft mapped 99% of the lunar surface with a resolution of 200 feet or better. Five (5) Lunar Orbiter missions were flown between 1967 and 1968. All were successful.

Surveyor spacecraft were tasked with landing on the Moon and providing detailed photographic, geologic and environmental information about the lunar surface. Seven (7) Surveyor missions were flown between 1966 and 1968. Five (5) spacecraft successfully landed.

The Surveyor spacecraft weighed 2,300 lbs at lift-off and 674 lbs at landing. The 3-legged vehicle stood within a diameter of 15 feet and measured almost 11 feet in height. Surveyor was configured with a television camera, a surface sampler and an alpha-scattering instrument to determine the chemical composition of the lunar soil.

Surveyor 7 was launched from Kennedy Space Center’s Launch Complex 36A at 06:30:00.545 UTC on Sunday, 07 January 1968. The ride to the Moon was provided by a General Dynamics Atlas-Centaur launch vehicle. It took almost 68 hours to reach the Moon.

On Wednesday, 10 January 1968, Surveyor 7 successfully landed at 01:05:36 UTC on the lunar surface near the North Rim of Tycho Crater. A total of 20,993 photographs were taken during Surveyor 7′s first lunar day. By Friday, 26 January 1968, Surveyor 7 was powered-down for its first lunar night.

On Monday, 12 February 1968, Surveyor 7 was powered-up for its second lunar day of surface operations. The spacecraft took an additional 45 photographs and operated erratically for 9 earth-days. At 00:24 UTC on Wednesday, 21 February 1968, contact with Surveyor 7 was lost for the final time. By 06:48 UTC, the Surveyor 7 mission was officially terminated.

Although seldom remembered today, the Surveyor Program provided America with a wealth of lunar surface information critical to the Apollo Program. Surveyor’s success provided an added measure of confidence in the attainability of a manned lunar landing. Indeed, seventeen (17) months after Surveyor 7 fell silent, Astronauts Neil A. Armstrong and Edwin E. Aldrin, Jr. imprinted the lunar surface with their bootprints at Mare Tranquilitatis.

Posted in Aerospace, History

Bridging the Booster Gap

Fifty-years ago this month, NASA successfully launched the first Saturn I Block II heavy-lift launch vehicle. Known as Saturn-Apollo No. 5 (SA-5), the mission featured the largest mass ever orbited up that time in the history of spaceflight.

The Saturn I was a pathfinder rocket booster that ultimately lead to the development of the mighty Saturn V launch vehicle. Ten (10) Saturn I boosters were flown between October 1961 and July 1965. The first four (4) missions involved the Block I variant wherein only the first stage was powered. The final six (6) missions employed Block II vehicles which included live first and second stages.

The Saturn I measured 164 feet in length with a maximum diameter of 21.42 feet. The S-I first stage was powered by an octet of Rocketdyne H-1 engines that generated a total sea level thrust of 1,500,000 lbs. The S-IV seconds stage incorporated six (6) Pratt and Whitney RL10 engines rated at a total vacuum thrust of 900,000 lbs.

SA-5 was launched from LC-37 at Cape Canaveral, Florida on Wednesday, 29 January 1964. Weighing 1,121,680 lbs at first stage ignition, the vehicle lifted-off at 14:25:01 UTC. As the first and second stages functioned in splendid fashion, the second stage successfully achieved an elliptical orbit measuring 142 x 415 nm.

The SA-5 orbited mass of 37,700 lbs was a record for the time. This payload, consisting of the S-IV stage, an instrument unit, and a modified Jupiter nose cone filled with sand ballast, remained in orbit through the end of April 1966.

The SA-5 mission was significant for a variety of reasons. It featured the first live S-IV rocket stage and was the first Saturn I vehicle to achieve orbit. It also marked that moment in spaceflight history when America finally surpassed the Soviet Union in payload mass to orbit capability. Known as “bridging the booster gap”, this event was an important step in the race to the moon in which America would be the ultimate victor.

Posted in Aerospace, History

Supersonic Manta Ray Debut

Sixty-three years ago this month, the USN/Douglas XF4D-1 Skyray fighter flew for the first time at Edwards Air Force Base in California. Douglas test pilot Robert O. Rahn was at the controls of the single-engine, carrier-based, supersonic-capable aircraft.

The Douglas XF4D-1 was the prototype version of the United States Navy’s F4D-1 Skyray. Designed to intercept adversary aircraft at 50,000 feet within 300 seconds of take-off, development of the Skyray began in the late 1940’s. As an aside, the Skyray nickname derived from the type’s large delta wing which gave it the appearance of a Manta ray.

The Skyray was originally designed to be powered by a Westinghouse XJ40-WE-6 turbojet capable of 7,000 lbs of sea level thrust. However, when significant developmental problems were encountered with that power plant, Douglas substituted an Allison J35-A-17 turbojet to support early flight testing of the XF4D-1. With a max sea level thrust of 5,000 lbs, the J35 rendered these early airframes significantly underpowered.

A pair of XF4D-1 Skyray airframes were built by Douglas. Ship No. 1 was assigned tail number BuAer 124586 while Ship No. 2 received the designation BuAer 124587.

On Tuesday, 23 January 1953, XF4D-1 Ship No. 1 (BuAer No 124586) departed Edwards Air Force Base on its first foray into the wild blue. Doing the piloting honors on this occasion was highly regarded Douglas test pilot Bob Rahn. The delta-winged beauty performed well on this maiden flight which concluded with Rahn making an uneventful landing back at Edwards.

Extensive flight testing of the Skyray, including carrier trials, continued through 1955. The Westinghouse XJ40-WE-8 appeared on the scene during this time. Rated at 11,600 lbs of sea level thrust in afterburner, this power plant allowed the Skyray to establish several speed records in California during October of 1953. Specifically, a speed of 752.944 mph was registered within a 3-kilometer course over the Salton Sea followed by 100-kilometer closed course mark of 728.11 mph at Edwards AFB.

Unfortunately, the XJ40 would prove to be very temperamental and unreliable. Inflight engine fires, explosions, and component failures constantly plagued the Skyray program. Westinghouse never did solve these problems to the satisfaction of the Navy. As a result, the service eventually opted to power production aircraft with the Pratt and Whitney J57-P-8 turbojet (10,200 lbs of sea level thrust).

The Douglas F4D-1 Skyray went on to serve with the United States Navy and Marines from 1956 through 1964. A total of 420 aircraft were produced. While never used in anger, the Skyray was a solid performer and served well in its intended role as a point design interceptor.

The Skyray holds the distinction of being the last fighter produced by the Douglas Aircraft Company before this legendary aerospace giant merged with McDonnell Aircraft to form McDonnell Douglas.

Posted in Aerospace, History