|Chrysler-built Saturn IB first stages in the final phase of assembly at NASA's Michoud Assembly Facility, November 1967. The clustered Redstone rocket bodies are most obvious on the stage at far left. Image credit: NASA.|
That Chrysler built the Saturn IB first stage should not be surprising. The company's Missile Division built intermediate-range Redstone missiles for the U.S. Army starting in 1950; the first flew in 1953. An upgraded Redstone, the Jupiter, served both as a missile and a space launcher. A modified Jupiter launched Explorer 1, the first U.S. Earth satellite, on 31 January 1958. Safety-enhanced Redstones launched suborbital Mercury spacecraft containing Alan Shepard, the first American in space (5 May 1961), and Virgil Grissom (21 July 1961).
|The first Saturn I rocket lifts off, 27 October 1961. For this suborbital test of the Chrysler-built S-I first stage, the rocket included a dummy S-IV second stage. Image credit: NASA.|
The last three Saturn I rockets each launched a Pegasus meteoroid-detection satellite, the first active payloads launched on a Saturn rocket. Pegasus 1 reached orbit in February 1965, Pegasus 2 in May 1965, and Pegasus 3 in July 1965. The Pegasus series was crucial for understanding the threat micrometeoroids posed to spacecraft and astronauts.
Shortly after Pegasus 1 reached space, at the Second Space Congress in Cocoa Beach, Florida, Chrysler engineers R. Dutzmann and E. Dunford described a small free-flying capsule for performing work outside spacecraft and space stations. They presented their paper in April 1965 during the six-week period that separated humankind's first spacewalk by Alexei Leonov (Voskhod 2, 18 March 1965) from the first U.S. spacewalk by Ed White (Gemini IV, 3 May 1965).
Dutzmann and Dunford's capsule design arose from a perceived need for new methods of protecting spacewalking astronauts — methods that would enhance protection but not compromise the ability to perform work. The Chrysler engineers explained, for example, that planned nylon fabric space suits might shield an astronaut from meteoroids if a coverall made of woven aluminum wire were added; the coverall would, however, make astronaut movement difficult.
Meteoroids were only one possible hazard of walking in space. Dutzmann and Dunford noted that objects in space have no weight, but retain their mass. They feared that a massive object — for example, a rocket stage — inadvertently set in motion might catch an astronaut unawares and crush him against another massive object.
The Chrysler engineers wrote that NASA planned to use a pure oxygen atmosphere at a pressure of 3.5 pounds per square inch (psi) inside its spacecraft and space suits. Experiments had shown that, should a space suit develop a leak, the astronaut would experience oxygen starvation if the pressure fell by just 0.8 psi. Increasing the flow of oxygen into the suit might keep pressure above the 2.7-psi critical level long enough for him to reach safety, but only if the suit perforation were small.
In addition, they noted that a space-suited astronaut would have no place to keep his tools. Attaching tools to the astronaut would impede movement.
The Chrysler engineers offered a brief assessment of past proposals for heavy (up to 2.5 ton) "taxis" that would include "comfortized" pressurized cockpits and mechanical manipulator arms. Such "luxuries," they wrote, could not realistically play a role in space operations before the 1970s. The technological leap required to move from a basic fabric space suit to a complex work vehicle was too great; also, tests had shown that existing mechanical manipulators were up to four times less efficient for doing work than astronaut arms and hands.
The capsule hull would comprise two layers of aluminum, each a fraction of an inch thick, separated by an empty space a little less than an inch wide. Meteoroids would strike the outer layer, break apart and partly vaporize, then strike the inner layer. Testing showed that this design, based on the Whipple Bumper concept, could provide meteoroid protection equivalent to that offered by a solid aluminum hull four times as thick. The Whipple Bumper was named for its inventor, comet astronomer Fred Whipple.
Dutzmann and Dunford suggested that the empty space between the aluminum layers be filled with aluminum honeycomb to improve structural strength. The lightweight Whipple Bumper hull meant that the Chrysler capsule's structure would weigh just 88 pounds.
The capsule's dome-shaped ends would each contain a thruster group. A total of 12 catalyst-bed thrusters, not too different from the Mercury spacecraft attitude-control thrusters, would draw hydrogen peroxide from a tank located at the capsule center of gravity. Upon contact with the catalyst, the hydrogen peroxide would turn to high-temperature steam and vent from the thruster nozzle. Each thruster could produce up to 10 pounds of thrust.
The astronaut, who would stand within the capsule, would open a pair of sliding doors with windows and lean out through the open doorway to perform tasks using tools gripped in gloved hands. Two pairs of telescoping arms with sticky pads at the ends, arranged one above the other, would extend through the 27-inch-by-78-inch door opening on either side of the astronaut's hips and thighs to hold the capsule in place at the work site.
|A pair of Chrysler Transportation and Work Station Capsules in action in lunar orbit. Image credit: Chrysler Corporation.|
Dutzmann and Dunford offered a timeline for pressure seal curtain activation. They assumed that the astronaut's fabric space suit would most likely become damaged while the capsule was attached to a work site since at all other times the astronaut would remain inside the capsule with the doors closed.
They expected that a "pressurization emergency" would be detected 10 seconds after suit damage occurred. Five seconds post-detection, the capsule would automatically detach from the four arms holding it at its work site. This would clear the way for its sliding doors to shut 10 seconds after detection. Fifteen seconds after detection, the seal curtain would rise up and attach itself to the capsule "ceiling." Simultaneously, a backup oxygen supply mounted behind the astronaut's shoulders would activate, increasing flow into the astronaut's damaged suit. Air leaking from the suit would begin to fill the seal curtain volume 30 seconds after leak detection.
Much like the fabric space suit, the seal curtain would vent oxygen overboard to prevent buildup of exhaled carbon dioxide. Dutzmann and Dunford assumed that, to avoid oxygen depletion and carbon dioxide buildup within his helmet, the astronaut would open his visor soon after pressure within the seal curtain exceeded 2.7 psi.
The astronaut would then pilot the capsule back to its docking structure on the home spacecraft. If the capsule remained within 1000 feet of the docking structure, as Dutzmann and Dunford recommended, the trip would last less than 10 minutes.
The three Saturn I-launched Pegasus satellites would reveal that the threat from meteoroids in space was less severe than expected, but other dangers lay in wait for 1960s spacewalkers. The Soviet Union would for years claim that Alexei Leonov's spacewalk was a complete success, when in fact he could not control his movements, overheated, and became stuck sideways in Voskhod 2's inflatable airlock.
Ed White's excursion outside the Gemini IV spacecraft, less than a month after the Chrysler engineers presented their capsule design, was nearly as successful as Leonov's was claimed to have been. More careful analysis would, however, have pointed to potential problems — White's suit expanded during his spacewalk, and he exceeded the cooling capacity of his air-cooled space suit while struggling to squeeze into his narrow seat and close his balky spacecraft hatch.
Not until humankind's perilous third spacewalk on 5 June 1966 would the inadequacies of air-cooled space suits become obvious. During an ambitious attempt to fly free of the Gemini IX spacecraft using a 168-pound hydrogen peroxide-fueled Astronaut Maneuvering Unit (AMU) backpack, pilot Eugene Cernan tore his suit's outer layers, overheated, and became blinded by perspiration as he struggled against his suit's internal pressure. Cernan's AMU free flight was called off and NASA was forced to descope its planned series of complex Gemini Program spacewalks (see "More Information" below).
"Design Considerations for a Free Space Transportation and Work Station Capsule," R. Dutzmann and E. Dunford, Proceedings of the 2nd Space Congress, April 1965, pp. 403-430.
Chrysler's Ballistic Missile and Space Activities: First 20 Years, Chrysler Corporation, 1972.
Walking to Olympus: An EVA Chronology, Monographs in Aerospace History #7, David S. F. Portree and Robert C. Trevino, NASA History Office, October 1997, pp. 1-5, 11 (https://history.nasa.gov/monograph7.pdf — accessed 12 November 2017).
The Spacewalks That Never Were: Gemini Extravehicular Planning Group (1965)
Rocket Belts and Rocket Chairs: Lunar Flying Units