In the years leading up to the beginning of the Space Age, there were many studies made in the West about lunar missions which gripped the public’s imagination. Among these were grandiose proposals made by German rocket pioneer, Wernher von Braun, who had been relocated to the US after World War II to develop missiles for the US Army. His writings on the topic in popular American magazines like Colliers during the 1950s and widely-watched documentaries produced by Walt Disney inspired an entire generation with visions of space stations, trips to the Moon, and large expeditions to Mars. All these missions were still far in the future since they required the development of rockets significantly larger than any in existence.
Von Braun’s articles in popular magazines like Colliers helped to increase public interest in space travel in the 1950s. (NASA)
Early Proposals to Reach the Moon
More modest (and realistic) proposals for lunar missions, which could be flown in the near term using available technology, were studied by a wide range of groups. In the two years leading up to the launch of Sputnik and the beginning of the Space Age, serious proposals included one by Aerojet Corporation (which today is part of Aerojet Rocketdyne) to use a five-stage version of its Aerobee sounding rocket to send a probe to the Moon as well as Ford’s Aeronutronic division using a lash up of the Vanguard and X-17 rockets, Martin (which today is part of the aerospace giant Lockheed Martin) using their Titan ICBM then under development, and the USAF employing the rocket booster of the Navaho cruise missile (then the largest American rocket to fly) combined with the Redstone and solid upper stages. The RAND Corporation proposed a lunar impactor launched using a version of the Atlas ICBM and the Massachusetts Institute of Technology studied recoverable lunar probes.
There were even serious proposals to detonate a nuclear weapon on the surface of the Moon. One such proposal was outlined in an article in the June 1957 issue of Scientific American written by the designer of the innovative Atlas ICBM, Krafft Ehricke, and Noble prize winning physicist, George Gamow. Called “Cow” (referring to the nursery rhyme line, “the cow jumped over the Moon”), one of their proposed flights would detonate a nuclear device on the lunar surface with a second probe following close behind to pass through the resulting debris cloud to retrieve lunar samples for return back to the Earth.
After the furor caused by the launching of the first Soviet Sputniks (see “Sputnik: The Launch of the Space Age”), some of these proposals started to receive serious attention by the American Department of Defense (DoD). In the hopes of quickly unifying the military’s research projects and securing a major share of the nation’s future space program for the DoD, Secretary of Defense Neil McElroy established the Advanced Research Projects Agency (ARPA) on February 7, 1958. ARPA was charged with coordinating all the DoD’s advanced research, including their space projects, to help eliminate duplicate efforts among the various branches of the service. Since the entire space program at this time was connected in some way to the military, by default ARPA would be in charge of almost all aspects of the American space program until Congress and the Eisenhower Administration made other arrangements.
Neil McElroy was President Eisenhower’s Secretary of Defense from 1957 to 1959 and oversaw the formation of ARPA and its first Moon program, Operation Mona. (DoD)
On March 27, 1958, President Eisenhower approved McElroy’s plan for ARPA to undertake its first series of space missions. The most ambitious of these was labeled “Operation Mona” which called for the launching of five probes to the Moon in hopes of beating the Soviet Union to our neighbor. Three of these attempts would be sponsored by the USAF Ballistic Missile Division while the von Braun’s group at the Army Ballistic Missile Agency (ABMA) would be responsible for the last two. ARPA believed that a successful military lunar mission would not only help the US leap frog ahead of the Soviet Union in the space race, but also add credibility to the military presence in space. It was felt by some that these missions could help prevent any civilian space agency that Congress might create from taking an important share of the space program from the DoD. In addition, the long-distance guidance and tracking experience gained in the project would be useful for future scientific and weapons programs.
The USAF Moon Probes
The USAF proposal would have the first shot at the Moon with the more ambitious of the two sets of ARPA lunar probes under the name of “Project Able-1”. For these missions, the USAF planned to use their new Thor-Able rocket, which had been cobbled together from existing rocket components. The first stage of this rocket was the Thor intermediate-range ballistic missile (IRBM) which, as a weapon, had a range of 2,600 kilometers. The Thor, built by the Douglas Aircraft Company (which became McDonnell-Douglas and much later merged with Boeing) for the USAF, was about 18.6 meters long and 2.4 meters in diameter at the base. The Thor incorporated a Rocketdyne MB-3 power plant burning kerosene and liquid oxygen (LOX) to produce 668 kilonewtons of thrust.
A USAF Thor IRBM, Number 115, being prepared for a test flight from Cape Canaveral, Florida on June 4, 1958. (USAF)
In the Thor-Able configuration, Thor’s one-ton nuclear warhead was replaced with an adapter upon which the 1,880-kilogram upper stages were mounted. These stages were modified versions of the ones originally developed for the Navy’s Vanguard program (see “Vanguard TV-3: America’s First Satellite Launch Attempt”). The Vanguard second stage built by Douglas was modified by the builders of the USAF lunar probes, STL (Space Technology Laboratory – a division of what would become TRW), for the Thor-Able program. In the Able configuration, the second stage retained its original 0.85 meter diameter but it was shortened to 5.8 meters to optimize its size for the Thor-Able mission. The second stage’s original Aerojet General AJ10-37 liquid propellant rocket engine was also replaced with the substantially improved AJ10-41 engine which generated 35 kilonewtons of thrust burning UDMH and nitric acid. Before it had been selected for its lunar mission, a two-stage version of this rocket, designated Thor-Able 0, had been selected by the USAF for high-speed reentry testing of proposed ICBM reentry vehicle designs. STL had submitted the proposal for what became known as ARTV (Able Reentry Test Vehicle) on November 1, 1957 with work beginning in earnest the following month.
The first two-stage Thor-Able 0 shown on the pad at LC-17A for the first ARTV launch on April 23, 1958. (USAF)
The third stage of what would become known as the Thor-Able 1 was the fiberglass-cased X-248 solid motor built by Allegany Ballistics Laboratory (which today is operated by ATK under contract from the US Navy). This innovative lightweight motor was an evolutionary outgrowth of work for the US Navy to develop a backup for the more conventional motor developed by the Grand Central Rocket Company for the Vanguard program. The X-248, which generated 12.5 kilonewtons of thrust for 38 seconds, was later incorporated into several other rocket designs including a high performance version of the Vanguard satellite launch vehicle. Altogether, the Thor-Able I was 27 meters tall from its base to the top of its hemispherical “mushroom cap” payload fairing. Theoretically, the Thor-Able I could place 160 kilograms of payload into a 480-kilometer high orbit or up to 39 kilograms into a direct ascent escape trajectory to the Moon or beyond.
STL’s lunar orbiter built for the USAF Project Able-1. (STL/John Taber)
The USAF lunar probe, which was frequently labeled as “stage 4” in STL’s Thor-Able design documents, had the ambitious goal of being the first spacecraft to orbit the Moon less than a year after the first satellites had been launched into Earth orbit. Under contract by the USAF, STL built three 38-kilogram spin-stabilized probes each carrying 18 kilograms of scientific instruments. The orbiter consisted of a wide cylindrical belt with a diameter of 74 centimeters joining two flattened fiberglass cones. At the end of the bottom cone was a ring of eight vernier solid rockets which could be fired to correct the probe’s trajectory with a total velocity increment of 23 meters per second. At the other end of the 76-centimeter tall probe was a single Thiokol TX-8 solid rocket motor that would be fired about 65 hours after launch to slow the probe’s speed by about 850 meters per second allowing it to enter lunar orbit. Without any attitude control system, the probe spinning at a rate of about 120 rpm would essentially maintain a constant orientation in inertial space after its release from the launch vehicle’s final stage. Removable black and white stripes applied to the probe’s exterior before launch and other interchangeable elements with differing finishes were used for passive thermal control to maintain the orbiter’s internal temperature between 16° and 29° C.
Diagram showing the arrangement of equipment inside the Project Able-1 lunar orbiter. Click on image to enlarge. (STL)
The probe’s wide belt carried the control systems, batteries, radio, and scientific instruments to measure magnetic fields, radiation, and micrometeorites. The STL probe also carried a simple line-scan camera designed and built by the Naval Ordinance Test Station (NOTS) similar to units built for the NOTSNIK satellite in the hopes of obtaining the first close-up images of the Moon (see “NOTSNIK: The First Air-Launched Satellite Attempts”). This camera had a mass of 3.8 kilograms and consisted of a small parabolic mirror that focused infrared radiation received from the Moon onto a special detector cell. The scene would be slowly built up one pixel at a time by the rotation of the probe and the forward motion of the spacecraft in relation to the Moon. The camera would be activated automatically after the camera detected the light of its target following the firing of the retrorocket. Once activated, there would be sufficient battery power available to operate the camera and its dedicated 50-watt transmitter for a few hours – hopefully long enough to secure and transmit a single crude image of the Moon via the USAF’s primary tracking station in Hawaii.
A schematic diagram showing how a Project Able-1 lunar orbiter camera would acquire its images of the Moon. Click on image to enlarge. (STL)
Because of the mission requirements, the fixed orientation of the probe and the crude nature of the probe’s thermal control system, launches to the Moon were only possible during a four-day period each month with at best a 35-minute window on each day. On the remote chance that the probe should accidentally impact the Moon, the spacecraft was decontaminated to minimize the chances that organisms from Earth would corrupt any future biological investigations on the Moon.
Technicians are shown preparing a Project Able-1 lunar orbiter under sterile conditions to minimize the risk of contaminating the Moon. (STL)
The First Launch Attempt
After a half year of intensive effort by the staff at STL and other USAF contractors, the first USAF lunar probe was ready for a launch window which ran from August 17 to 20, 1958. Thor number 127 was erected on Pad A at Launch Complex 17 (LC-17A) at Cape Canaveral, Florida followed by its STL-modified upper stages. As launch preparation proceeded, there were concerns about Thor’s MB-3 engine. The failure of an IRBM test flight of Thor 108 on October 11, 1957 and the failure of Thor 116 in the first launch attempt of the ARTV program on April 24, 1958 were determined to be the result of a failure in the MB-3 turbopump. Other flights seemed unaffected by the possible issue. Subsequent analysis of the turbopump design, however, showed it to be marginal at best sparking concerns about the first launch of Project Able-1.
The second stage is being lifted on top of Thor 127 in preparation of the first Project Able-1 launch attempt. (STL)
Despite the concerns, preparation for the launch continued with the fear that the Soviet Union would attempt to upstage the mission in the back of everyone’s mind (see “The First Race to the Moon: Getting Off the Ground”). In preparation for the launch attempt on August 17, with its launch window opening at 7:14 AM EST, the Thor-Able rocket was fueled on the afternoon of August 16 with final propulsion and electrical tests started at 7:30 PM EST and completed ahead of schedule.
The first Project Able-1 rocket being prepared for launch. (USAF)
The countdown continued without any major problems. At the T-35 minute mark, communications were checked and a minor interference issue was noted in a low-frequency telemetry transmitter resulting in a brief hold at the T-15 minute mark. When the launch team decided that this was not a major issue, the countdown started up once again. Just four minutes into its launch window, Thor 127 lifted off from LC-17A at 7:18 AM EST (12:18 GMT) into a clear Florida sky carrying the Able-1 stages and payload. For the first time in the history of our species, we were attempting to reach the Moon. All seemed to be going as planned as the Thor-Able accelerated towards space. But as the quickly rising rocket passed an altitude of 15 kilometers some 73.6 seconds after launch, it exploded. Transmissions from the still active Pioneer probe were received until it and the remains of the Thor-Able plummeted into the Atlantic Ocean two minutes later. The first ARPA-sponsored lunar mission had failed.
The launch of Thor 127 carrying the Project Able-1 upper stages and payload on August 17, 1958 (left) followed 74 seconds later by its destruction following a turbopump failure (right). (USAF)
A subsequent analysis of the telemetry and hardware recovered by Navy divers showed that a fault in the turbopump in Thor’s MB-3 engine was to blame for the failure as had been feared. With the cause of the first Able-1 failure established, it was decided to replace Thor 129, which had already been erected on the launch pad on August 19 in preparation for a September launch attempt of Project Able-1, so that the fault in its MB-3 engine could be corrected. The next launch attempt was pushed back a month with a modified Thor 130 substituted to serve as the booster. In the meantime, a new name was officially adopted by the USAF for this series of flights – Pioneer. The first unsuccessful launch attempt was retroactively designated “Pioneer 0” with the next mission scheduled for October to be called “Pioneer 1”. But with the formation of NASA on October 1, 1958, this next launch attempt would be the responsibility of the new space agency with the USAF officially relegated to a support role (see “Pioneer 1: NASA’s First Space Mission”)
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Related Reading
“Pioneer 1: NASA’s First Space Mission”, Drew Ex Machina, October 11, 2016 [Post]
“The First Race to the Moon: Getting Off the Ground”, Drew Ex Machina, November 8, 2018 [Post]
General References
Evert Clark, “First US Lunar Probe Fails After Promising Launch”, Aviation Week, Vol. 69, No. 8, pp 20-22, August 25, 1958
Gideon Marcus, “Pioneering Space”, Quest, Vol. 14, No. 2, pp. 52-59, 2007
Gideon Marcus, “Pioneering Space – Part II”, Quest, Vol. 14, No. 3, pp. 18-25, 2007
Adolph K. Thiel, “The Able Series of Space Probes”, May 20, 1960
“First Lunar Shot to Seek Far Side Data”, Aviation Week, Vol. 69, No. 5, p 26, August 4, 1958
“1958 NASA/USAF Space Probes (Able-1) Final Report: Volume 1 – Summary”, Space Technology Laboratory, February 18, 1959
“1958 NASA/USAF Space Probes (Able-1) Final Report: Volume 2 – Payload and Experiments”, Space Technology Laboratory, February 18, 1959
For FINE and detailed photo coverage of the launch preparations, I suggest “The Missile Men” by Mel Hunter. His photos take you right on to the gantry as the vehicle is prepared and launched.
Thanks for the tip! I’m always looking for good illustrations from the early Space Age in old books and magazines and I’ll have to add this title to my wish list 🙂
Can you please add both measurements for distance? I don’t do well converting miles to km
Apologies but, at one time I did give both Imperial and SI units in my articles. However, I got a lot of negative feedback on how distracting this practice was. Since I use SI units exclusively in my professional scientific work and the majority of my readers (most of whom live outside the US) commonly use and understand SI units, I made the decision when I created this website 8 years ago to use SI units exclusively in my writing.
I wonder if you actually use SI units in your work or cling to older cgs units. Do you use kilograms for mass and newtons for weight/force, or do you use kilograms as a force unit? Do you use all of the prefixes or do you just use the original 6 around unity and insert counting words. I would rather see megametres, gigametres, terametres, etc than thousands of kilometres, millions of kilometres, etc. Counting words defeat the purpose of the extended range of prefixes.
What about megagram and beyond instead of tonne?
Then learn SI units like everyone else. There is never a need to convert, learn and get the feel for the units the whole world uses. I hate it when ‘muricans whine and expect to be pampered by everyone else. Very irritating
To MM – Perhaps it’s time to start using decimal kilometers, like the entire rest of global humanity, and upgrade the way you measure things from an arcane “system” from 10th century Rome?
Thanks for using only SI Metric in your article.
It was refreshing to be able to read the article and not have to convert to world standard measures.
That makes it so the whole world can understand the measurements.