Caldwell Johnson, co-holder with Maxime Faget of the Mercury space capsule patent, was chief of the Spacecraft Design Division at the NASA Manned Spacecraft Center (MSC) in Houston, Texas, when he proposed that astronauts test prototype Space Shuttle manipulator arms and end effectors during Apollo Command and Service Module (CSM) missions in Earth orbit. In a February 1971 memorandum to Faget, NASA MSC's director of Engineering and Development, Johnson described the manipulator test mission as a worthwhile alternative to the Earth survey, space rescue, and joint U.S./Soviet CSM missions then under study.
At the time Johnson proposed the Shuttle manipulator arm test, three of the original 10 planned Apollo lunar landing missions had been cancelled, the second Skylab space station (Skylab B) appeared increasingly unlikely to reach orbit, and the Space Shuttle had not yet been formally approved. NASA managers foresaw that the Apollo and Skylab mission cancellations would leave them with surplus Apollo spacecraft and Saturn rockets after the last mission to Skylab A. They sought low-cost Earth-orbital missions that would put the surplus hardware to good use and fill the multi-year gap in U.S. piloted missions expected to occur in the mid-to-late 1970s.
Johnson envisioned Shuttle manipulators capable of bending and gripping much as do human arms and hands, thus enabling them to hold onto virtually anything. He suggested that a pair of prototype arms be mounted in a CSM Scientific Instrument Module (SIM) Bay, and that the CSM "pretend to be a Shuttle" during rendezvous operations with the derelict Skylab space station.
The CSM's three-man crew could, he told Faget, use the manipulators to grip and move Skylab. They might also use them to demonstrate a space rescue, capture an "errant satellite," or remove film from SIM Bay cameras and pass it to the astronauts through a special airlock installed in place of the docking unit in the CSM's nose.
|Image credit: NASA/Caldwell Johnson.|
Faget enthusiastically received Johnson's proposal (he penned "Yes! This is great" on his copy of the February 1971 memo). The proposal generated less enthusiasm elsewhere, however.
Undaunted, Johnson proposed in May 1972 that Shuttle manipulator hardware replace Earth resources instruments that had been dropped for lack of funds from the planned U.S.-Soviet Apollo-Soyuz Test Project (ASTP) mission. President Richard Nixon had called on NASA to develop the Space Shuttle just four months before (January 1972). Johnson asked Faget for permission to perform "a brief technical and programmatic feasibility study" of the concept, and Faget gave him permission to prepare a presentation for Aaron Cohen, manager of the newly created Space Shuttle Program Office at MSC.
In his June 1972 presentation to Cohen, Johnson declared that "[c]argo handling by manipulators is a key element of the Shuttle concept." He noted that CSM-111, the spacecraft tagged for the ASTP mission, would have no SIM Bay in its drum-shaped Service Module (SM), and suggested that a single 28-foot-long Shuttle manipulator arm could be mounted near the Service Propulsion System (SPS) main engine in place of the lunar Apollo S-band high-gain antenna, which would not be required during Earth-orbital missions.
During ascent to orbit, the manipulator would ride folded beneath the CSM near the ASTP Docking Module (DM) within the streamlined Spacecraft Launch Adapter. During SPS burns, the astronauts would stabilize the manipulator so that acceleration would not damage it by commanding it to grip a handle installed on the SM near the base of the CSM's conical Command Module (CM).
Johnson had by this time mostly dropped the concept of an all-purpose human hand-like "end effector" for the manipulator; he informed Cohen that the end effector design was "undetermined." The Shuttle manipulator demonstration would take place after CSM-111 had undocked from the Soviet Soyuz spacecraft and moved away to perform independent maneuvers and experiments.
The astronauts in the CSM would first use a TV camera mounted on the arm's wrist to inspect the CSM and DM, then would use the end effector to manipulate "some device" on the DM. They would then command the end effector to grip a handle on the DM, undock the DM from the CSM, and use the manipulator to redock the DM to the CSM. Finally, they would undock the DM and repeatedly capture it with the manipulator.
Johnson estimated that new hardware for the ASTP Shuttle manipulator demonstration would add 168 pounds (76.2 kilograms) to the CM and 553 pounds (250.8 kilograms) to the SM. He expected that concept studies and pre-design would be completed in January 1973. Detail design would commence in October 1972 and be completed by 1 July 1973, at which time CSM-111 would undergo modification for the manipulator demonstration.
Johnson envisioned that MSC would build two manipulators in house. The first, for testing and training, would be completed in January 1974. The flight unit would be completed in May 1974, tested and checked out by August 1974, and launched into orbit attached to CSM-111 in July 1975. Johnson optimistically placed the cost of the manipulator arm demonstration at just $25 million.
CSM-111, the last Apollo spacecraft to fly, reached Earth orbit on schedule on 15 July 1975. By then, Caldwell Johnson had retired from NASA. CSM-111 carried no manipulator arm; the tests Johnson had proposed had been judged to be unnecessary.
That same month, the U.S. space agency, short on funds, invited Canada to develop and build the Shuttle manipulator arm. The Remote Manipulator System — also called the Canadarm — first reached orbit on board the Space Shuttle Columbia during STS-2, the second flight of the Shuttle program, on 12 November 1981.
Memorandum with attachment, EW/Chief, Spacecraft Design Division, to EA/Director of Engineering and Development, "Flight Demonstration of Shuttle docking and cargo handling techniques and equipment using CSM/Saturn 1-B," NASA Manned Spacecraft Center, 1 February 1971.
Memorandum with attachment, EW/Chief, Spacecraft Design Division, to PA/Special Assistant to the Manager, "Demonstration of Shuttle manipulators aboard CSM/Soyuz rendezvous and docking mission," NASA Manned Spacecraft Center, 25 May 1972.
Memorandum with attachment, EW/Chief, Spacecraft Design Division, to LA/Manager, Space Shuttle Program Office, "Proposal to Demonstrate Shuttle-type Manipulator During Apollo/Soyuz Test Project," NASA Manned Spacecraft Center, 28 June 1972.
"Still Under Active Consideration": Five Proposed Earth-Orbital Apollo Missions for the 1970s (1971)