31 December 2017

There's a Hell of a Good World Next Door

Image credit: U.S. Air Force













Image credit: NASA


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The Eighth Continent

Harold Urey and the Moon (1961)


Rocket Belts and Rocket Chairs: Lunar Flying Units


23 December 2017

What If a Shuttle Orbiter Struck a Bird? (1988)











The Shuttle Landing Facility. Image credit: NASA






























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What If a Shuttle Orbiter Had to Ditch? (1975)


29 November 2017

X-15: Lessons for Reusable Winged Spaceflight (1966)

























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McDonnell Douglas Phase B Space Station (1970)




25 November 2017




















18 November 2017

Pioneer Mars Orbiter with Penetrators (1974)

Pioneer Venus Orbiter (PVO) in Venus Orbit. The Pioneer Mars Orbiter (PMO) would have been based on this design. Image credit: NASA
The name "Pioneer" was applied to several different spacecraft designs, all of which were meant to spin to create gyroscopic stability. The first U.S. moon probe, launched by the Air Force in August 1958, bore the name. Though Pioneers 0 through 3 failed, Pioneer 4 flew by the moon at a distance of about 58,000 kilometers in March 1959. It became the first U.S. spacecraft to escape Earth's gravity and enter orbit around the Sun.

Pioneer 5 (March 1960), a unique design, was a pathfinder for future NASA interplanetary missions. Managed by NASA's Ames Research Center (ARC), it set a new record by transmitting until it was 36.2 million kilometers from Earth.

The Pioneer series seemed to draw to a close. In 1965, however, NASA ARC applied the name to its drum-shaped interplanetary "weather stations." The first, Pioneer 6, entered solar orbit between Earth and Venus in December 1965, where it monitored magnetic fields and radiation. Pioneers 7, 8, and 9 performed similarly prosaic (and generally little noticed) missions.

The first Pioneer design included a solid-propellant rocket motor on top; this was intended to slow the spacecraft so that the moon's gravity could capture it into lunar orbit. Pioneer 0, launched under U.S. Air Force auspices, was lost when its Thor-Able booster exploded 77 seconds after launch. Pioneers 1 and 2, launched under NASA auspices, also failed to reach lunar orbit, though the former attained a record altitude of 113,781 kilometers and returned useful data before falling back to Earth (October 1958). Image credit: NASA
NASA's Pioneer 3 and 4 lunar flyby spacecraft were launched on Redstone-derived Juno II rockets. Booster failure doomed Pioneer 3, but Pioneer 4, shown here attached to its small solid-propellant upper stage, performed a distant lunar flyby. Image credit: NASA
Pioneer 5, intended originally as a Venus probe set for launch in June 1959, was launched instead in March 1960 as a pathfinder for subsequent NASA planetary missions. Image credit: NASA
Pioneers 6 through 9 were drum-shaped spacecraft that measured "space weather" conditions in interplanetary space near Earth's orbit. Image credit: NASA
The name regained star status when Pioneer 10 left Earth in March 1972. It became the first spacecraft to brave the Asteroid Belt and fly past Jupiter. Pioneer 11 launched in April 1973, bound for Jupiter and Saturn. It went silent in 1995. Pioneer 10 sent its last signal from beyond Pluto in 2003.

The final Pioneer launches occurred in 1978. The Pioneer Venus Multiprobe spacecraft dropped four instrumented capsules on Venus, while Pioneer Venus Orbiter (PVO) surveyed the planet until 1992. The latter was informally designated Pioneer 12 and the former Pioneer 13.

Pioneer 10 and Pioneer 11, the only nuclear Pioneers, were Earth's first probes to traverse the Asteroid Belt and voyage through the outer Solar System. Image credit: NASA
Pioneer Venus Multiprobe deploys its one large and three small atmosphere probes. Against expectations, two probes survived landing and return data from the surface of Venus. No other U.S. spacecraft has landed intact on Venus. Image credit: NASA
If NASA ARC, the Planetary Programs Division of the NASA Office of Space Science, and Hughes Aircraft had had their way, the Pioneer name might also have been applied to a Mars spacecraft. In a 1974 report prepared on contract to NASA ARC, Hughes described a Pioneer Mars Orbiter (PMO) derived from the Hughes PVO spacecraft design. The PMO mission, set for launch in 1979, was intended as a follow-on to the twin Viking missions, which were scheduled to leave Earth in 1975 and seek life on Mars in 1976.

Hughes described the PVO upon which the PMO would be based as drum 2.5 meters in diameter and 1.2 meters tall with a 3.3-meter antenna mast on top and a solid-propellant Venus orbit insertion motor on the bottom. The company then cited differences between the PMO and PVO designs: for example, PMO's orbit insertion motor would need to be larger since it would arrive at Mars traveling faster than PVO would at Venus. In addition, PMO would operate in Mars orbit, about twice as far from the Sun as Venus, so solar cells would entirely cover its sides so that they could make enough electricity to operate the spacecraft's systems. PVO would operate in Venus orbit, so it would need to be only partly covered with solar cells.

The most obvious difference between the PVO and PMO designs were the Mars spacecraft's six 2.3-meter-long, 0.3-meter-diameter penetrator launch tubes. These would replace PVO's science instruments; apart from unspecified instruments in the penetrators, PMO would carry no science payload.

PMO, like PVO, would leave Earth on an two-stage Atlas-Centaur rocket. Because PMO would weigh more than PVO (1091 kilograms versus 523 kilograms), however, it would need a solid-propellant third stage to complete Earth escape. To make room for the third stage and penetrators, PMO's conical launch shroud would be 0.8 meters longer than its PVO counterpart.

PMO would need to reach Mars on 7 September 1980 so that its Mars orbit insertion motor could place it in its planned Mars orbit. To reach the planet on that date, PMO would need to depart Earth during one of 10 consecutive daily launch opportunities starting on 28 October 1979. 2 November 1979 would be the nominal launch date. The launch opportunities would only last from 10 to 15 minutes each.

The Centaur second stage would place PMO into a low-Earth orbit, then would ignite again 30 minutes later to begin pushing the spacecraft out of Earth orbit. The third-stage motor would then ignite to place PMO on course for Mars. PMO would weigh 1069 kilograms after third-stage separation. Launch on 2 November 1979 would yield a 310-day Earth-Mars transfer.

Following third-stage separation, PMO would use hydrazine thrusters to set itself spinning at 15 revolutions per minute (RPM) for stabilization. The antenna mast bearing the high-gain, low-gain, and two penetrator data reception antennas  would revolve in the opposite direction at the same rate, so would appear to stand still. Controllers on Earth would use the thrusters to carefully target PMO so that it would not accidentally hit Mars and introduce terrestrial microbes. They would perform a final course correction 30 days before Mars arrival.

One day out from Mars, on 6 September 1980, PMO would orient itself for its Mars orbit insertion burn and increase its spin rate to 30 RPM. The spacecraft's high-gain antenna would not point at Earth during the insertion burn. Controllers on Earth could, however, send PMO commands through the low-gain antenna.

Candidate PMO orbits. Image credit: Hughes Aircraft Company
PMO would reach Mars late in northern hemisphere summer, when the planet's south polar cap would be near its maximum extent. Hughes Aircraft proposed two possible elliptical Mars orbits - south polar and north polar - each with a period of 24.6 hours (one martian day) and a periapsis (low point) of 1000 kilometers. South polar orbit periapsis would occur above a point on Mars's surface 72° south of the equator, while north polar orbit periapsis would occur above a point at 37° north latitude. The spacecraft's high periapsis altitude would serve to forestall orbital decay, helping to ensure that PMO would not drop living terrestrial microbes on Mars. PMO would have a mass of 741 kilograms after orbit insertion.

The PMO mission's Mars orbit phase would last one martian year (686 terrestrial days). During this mission phase, PMO would deploy its six 45-kilogram penetrators singly and in pairs using a penetrator deployment system based on the Hughes-built TOW missile launcher. Before Earth departure the penetrators would be sealed inside their launch tubes and heated to kill hitchhiking microbes.

PMO deploys its first penetrator. The departing penetrator is at center right, while the exhaust plume from its small solid-propellant rocket motor gushes from the bottom end of the penetrator launch tube at lower left. On the bottom (left) side of the spacecraft, the Mars orbit-insertion engine bell is visible, as are the bottom ends of the six penetrator tubes. One tube is partly obscured by the exhaust plume, one by the orbit-insertion engine bell, and another by a neighboring penetrator tube. The top ends of three tubes are visible; one obscures the base of the counter-spun antenna mast mounted at the center of PMO's top (right) side. The high-gain dish antenna (center), two penetrator antennas, and the low-gain antenna are attached to the mast. Image credit: Hughes Aircraft Company
Penetrator deployment would occur near apoapsis (orbit high point), when the spacecraft's orbital velocity would be at its slowest. Hinged covers would open at both ends of the launch tube, then the penetrator's solid-propellant deployment rocket motor would ignite to launch it from the tube. Launching the penetrator in the direction opposite PMO's orbital motion would cancel out its orbital velocity and cause it to fall toward Mars. The dome-nosed penetrator, a Sandia Corporation design, would drop through Mars's atmosphere and implant itself in the surface up to 15 meters deep.

After impact, the penetrator would extend its antenna and begin transmitting data from its science instruments. PMO would record the penetrator data for relay to Earth through its high-gain dish. Chemical batteries in the penetrators would enable each to collect and transmit data from Mars for about eight days.

For their weak signals to be received, the penetrators would need to impact the surface not far from PMO's periapsis point. The orbiter could maintain radio contact with a given penetrator for at least eight minutes at a time. A PMO in south polar orbit would initially place its penetrators between 63° and 87° south; a north-polar-orbiting PMO would place them between 56° and 80° north. Periapsis would gradually shift north or south, however, permitting placement at other latitudes. With all six penetrators deployed, PMO would have a mass of 412 kilograms.

Viking 1 and Viking 2, each of which comprised a three-legged lander and an orbiter bearing cameras, were designed with certain assumptions in mind; for example, that microbial life on Mars would be ubiquitous, so that a scoop of surface dust and a jury of three biological experiments would readily reveal its presence. Unfortunately for the proposed 1979 PMO mission and NASA Mars exploration planning in general, the Viking biology experiments yielded equivocal results that were generally interpreted as indicative of a lifeless world. This, combined with the loss of the Mars Observer spacecraft as it attempted capture into Mars orbit in 1993, helped to create a two-decade gap during which no new U.S. spacecraft explored Mars.


Pioneer Mars Surface Penetrator Mission: Mission Analysis and Orbiter Design, Hughes Aircraft Company, August 1974

Pioneer Mars 1979 Mission Options, A. Friedlander, W. Hartmann, and J. Niehoff, Science Applications, Inc., 29 January 1974, pp. 61-99

Solar System Log, Andrew Wilson, Jane's, 1986, pp. 12-13, 16-17, 21

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12 November 2017


The Apollo 13 crew of Commander James Lovell (left), Command Module Pilot John "Jack" Swigert (center), and Lunar Module Pilot Fred Haise (right). Image credit: NASA
Launch of Apollo 13, the planned third Apollo moon landing, was just two months in the future when NASA Manned Spacecraft Center (MSC) engineer Rocky Duncan proposed an alternate plan for the mission. He noted that Apollo 13 would mark the first flight of the Hycon Lunar Topographic Camera (LTC), a modified U.S. Air Force KA-74 aerial reconnaissance camera, which would be mounted in the Command and Service Module (CSM) crew hatch window for high-resolution overlapping photography of candidate future Apollo landing sites.

In Apollo Program parlance, this was dubbed "bootstrap photography." It took advantage of the piloted CSM, which had to loiter in lunar orbit anyway to collect the lunar surface crew after they completed their mission, to collect data useful for planning future Apollo missions.

Duncan noted that previous Apollo lunar missions had followed a "free-return" path that would enable them to loop behind the moon and fall back to Earth if their CSM Service Propulsion System (SPS) main engine failed. The Apollo 13 CSM, on the other hand, would fire its engine during the voyage to the moon to leave the free-return trajectory. This was necessary so that the mission's Lunar Module (LM) could reach its target landing site at Fra Mauro.

The Apollo 13 Saturn V rocket clears the tower. Image credit: NASA
A day after launch from Earth, the Apollo 13 crew ignited the CSM Odyssey's Service Propulsion System (SPS) main engine to leave the free-return trajectory that would automatically return them to Earth in the event of an SPS failure. This was required to permit the mission to reach its destination, the scientifically significant Fra Mauro landing site. Image credit: NASA
The MSC engineer then described a scenario in which the Apollo 13 LM was judged to be "NO-GO" soon after Trans-Lunar Injection (TLI), the maneuver that would boost them from low-Earth orbit and place them on course for the moon. TLI would occur about two hours after launch; it would use the Saturn V S-IVB third stage with its single J-2 engine. Following TLI, the CSM would separate from the segmented shroud - the Spacecraft Launch Adapter - linking it to the S-IVB stage; the shroud would then peel back to reveal the LM. The crew would dock their CSM with the port on top of the LM and separate it from the S-IVB stage. Presumably soon after maneuvering away from the S-IVB they would discover the fault that would render their LM unable to land on the moon.

Apollo 13 would then become a "CSM-only lunar alternate photographic mission." The CSM would remain on a free-return path until it reached the moon, then its crew would perform a standard two-impulse lunar orbit insertion (LOI) maneuver; that is, they would fire the SPS to slow their CSM so that the moon's gravity could capture it into an elliptical lunar orbit, then would fire the engine again at perilune (the low point of its lunar orbit) to circularize its orbit.

Duncan noted that some "desirable photographic orbits with high inclinations. . .require a three-impulse LOI." He argued, however, that "since the crew has not been trained for this type of LOI. . .this type of profile [should] not be flown."

In Duncan's alternate mission, Apollo 13 would capture into a lunar orbit that would take it over the craters Censorinus and Mösting C. These were, respectively, ranked first and eleventh in priority on the Apollo 13 list of targets for lunar-orbital photography.
Censorinus was the leading landing site candidate for Apollo 15, which at the time Duncan wrote his memo was planned as an H-class mission similar to Apollo 13 (that is, its LM would not carry a Lunar Roving Vehicle and would remain on the moon for only about a day and a half). Apollo 12 in November 1969 had been the first H-class mission, so had been designated H-1; Apollo 13 was H-2, Apollo 14 would be H-3, and Apollo 15 would be H-4, the final H-class flight.

Duncan advocated delaying the crew's scheduled sleep period by two lunar revolutions to enable them to photograph Censorinus and Mösting C. The photographic program would begin during Revolution 3 with vertical stereo photography using window-mounted Hasselblad cameras. Revolution 4 would see the first high-resolution vertical Hycon LTC photography, then the astronauts would conduct high-resolution oblique (side-looking) LTC photography during Revolution 5. They would perform "landmark tracking" using the CSM's wide-field scanning telescope (a part of its navigation system) during Revolutions 6 and 7, then would begin their delayed sleep period.

The Apollo 13 crew would awaken during Revolution 12 and fire the SPS to change their spacecraft's orbital plane (that is, the angle at which its orbit crossed the moon's equator). They would do this so that, beginning with Revolution 14, they would pass over Descartes, a suspected volcanic site in the moon's light-colored central Highlands, and Davy Rille, a chain of small craters of suspected volcanic origin. The astronauts would repeat the five-revolution photography sequence they used to image Censorinus and Mösting C. Duncan noted that Descartes ranked second on the Apollo 13 list of photographic targets, while Davy was fourth.

Duncan briefly considered a scenario in which the Apollo 13 LM was incapable of landing yet had a working descent engine which the crew could use to perform plane-change maneuvers in lunar orbit. He noted that the LM would block some CSM windows while it was docked. The astronauts might undock the CSM from the LM for photography and dock again for additional plane changes, or they might discard the LM after only a single plane change. Duncan favored a simpler approach: jettison the LM as soon as it was judged to be incapable of landing whether its descent engine was functional or not and use only the CSM SPS.

The astronauts would perform "target of opportunity" photography during Revolutions 18 and 19, then would sleep. They would wake during Revolution 24 and perform a plane change during Revolution 25 so that they could fly over Alphonsus crater, Gassendi West, and Gassendi East beginning with Revolution 27 and again carry out the five-revolution photography sequence. Alphonsus, where surface color changes and luminescence have been reported, was ranked ninth on the Apollo 13 target list, while the two sites in dark-floored Gassendi crater were ranked thirteenth and fourteenth, respectively.

Duncan estimated that, by the time the astronauts finished photographing the Alphonsus and Gassendi crater candidate landing sites, Apollo 13's cameras would likely have run out of film. He recommended that the crew fire the SPS to leave lunar orbit and return to Earth during Revolution 32 or two revolutions after the film ran out, whichever came first.

Apollo 13 left Earth on 11 April 1970. The LM Aquarius checked out as "GO" for a landing on the moon, and on 12 April the crew performed the SPS burn to leave the free-return trajectory. The next day, CSM Odyssey suffered an oxygen tank explosion in its Service Module (SM).

Because the extent of the internal damage to the CSM was unknown, NASA wrote off Odyssey's SPS and looked to the LM for salvation. Astronauts James Lovell, Jack Swigert, and Fred Haise used Aquarius's descent engine to get back onto a free-return trajectory.

During their lunar flyby, the crew photographed the moon through Aquarius's windows using hand-held cameras. Odyssey blocked part of their field of view, but there was no thought of discarding it: the crew needed the conical Command Module (CM), with its bowl-shaped heat shield, to reenter Earth's atmosphere at the end of their voyage.

Inside the lifeboat: after the explosion in the Apollo 13 CSM Odyssey, the Apollo 13 crew shut down Odyssey's systems and relocated to the still-functional LM Aquarius. The LM was designed to support two men for 36 hours, not three for four days. This meant that exhaled carbon dioxide built up in the cabin air. With assistance from engineers on Earth, the crew built a system (image above) that allowed the CSM's carbon dioxide-absorbing lithium hydroxide canisters to be used in the LM. CSM Pilot Jack Swigert, who would have performed "bootstrap photography" in lunar orbit had the third lunar landing attempt gone ahead as planned, is visible at right. Image credit: NASA
As Apollo 13 swung around the moon and began its fall back to Earth, its crew used handheld cameras to photograph the moon through windows in the LM Aquarius. This image, captured through one of the ceiling-mounted rendezvous and docking windows, shows parts of the Nearside and Farside hemispheres. Dominating the top half of the image is the crippled CSM Odyssey. To conserve electricity, its internal lights are off, making its windows dark. The out-of-focus lines on the rendezvous window were meant to enable the LM crew to gauge distance during rendezvous and docking with the CSM. Image credit: NASA
The Hycon camera was not used for photography, though it did provide a hose for the improvised adapter the crew made so that Odyssey's carbon dioxide-absorbing canisters could be used inside Aquarius. With help from the hose and the world-wide Apollo mission team, the crew safely reentered Earth's atmosphere and splashed down in the Pacific Ocean in the Odyssey CM on 17 April.

Apollo 14 (31 January-9 February 1971) became the first (and last) lunar mission to use the Hycon LTC. By the time it flew, NASA had cancelled Apollo 15 and 19 as part of its efforts to preserve its proposed Space Station/Space Shuttle Program. It had renumbered the remaining Apollo flights so that they ended with Apollo 17. Apollo 14, H-3, became the last H-class mission. The camera's chief target was Descartes, which had moved to the top spot among Apollo 16 landing site candidates. Apollo 16, planned as a J-class mission, would include a two-seat Lunar Roving Vehicle, an LM capable of remaining on the moon for three days, and a CSM with an ejectable subsatellite and a pallet of sophisticated sensors and cameras in its SM.

The Hycon camera captured 192 images, but malfunctioned while imaging the lunar surface about 70 kilometers east of Descartes. Though Apollo 14 returned no images of the site, Apollo 16 (J-2) landed at Descartes in April 1972.


Memorandum with attachment, FM5/Lunar Mission Analysis Branch to various, “Lunar alternate missions for Apollo 13 (Mission H-2),” Rocky Duncan, 13 February 1970

"Scientific Rationale Summaries for Apollo Candidate Lunar Exploration Landing Sites – case 340," J. Head, Bellcomm, Inc., 11 March 1970

"Significant Results from Apollo 14 Lunar Orbital Photography," F. El-Baz and S. Roosa, Proceedings of the 1972 Lunar Science Conference, Vol. 2, pp. 63-83, 1972

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29 October 2017

Chrysler's Transportation and Work Station Capsule (1965)

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 right. Image credit: NASA
In the 1960s, the Chrysler Corporation, an automobile company founded in 1925, manufactured the first stage of the Saturn IB, the first and last member of the Saturn rocket family to launch astronauts into space. After four successful unmanned test flights beginning in February 1966, Saturn IBs launched the Apollo 7 Command and Service Module (CSM), the first Apollo spacecraft to carry a crew (11-22 October 1968); the three CSMs that ferried crews to and from Skylab, the first U.S. space station (May 1973-February 1974); and the Apollo-Soyuz Test Project (ASTP) CSM and the Docking Module its crew used to link up with the Soviet Soyuz 19 spacecraft in Earth orbit (15-24 July 1975). The ASTP CSM was the last Apollo spacecraft to fly.

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 carried a dummy S-IV second stage. Image credit: NASA
Redstone and its derivatives prepared Chrysler for its contributions to the 162-foot-tall Saturn I, which can reasonably be described as NASA's rocket for learning how to fly big rockets. Saturn I flew 10 times between October 1961 and July 1965. Chrysler's Saturn I first stage included eight Redstone rocket bodies clustered around a central Jupiter rocket body. The Jupiter and four Redstones were filled with liquid oxygen; the remaining four Redstones held RP-1 aviation fuel. Chrysler's Saturn IB first stage followed an identical pattern.

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.

Side view of the interior of Chrysler's Transportation and Work Station Capsule with astronaut positions indicated. A = outline of astronaut position with capsule doors closed; B = outline of astronaut position at work site with capsule doors open. Work site attachment arms are shown in black outline in closed-door (retracted) position and in red in open-door (extended) position. Image credit: Chrysler Corporation/DSFPortree
Top view of the interior of Chrysler's Transportation and Work Station Capsule. A1 = left sliding door/window; A2 = right sliding door/window; B = hand controller for guiding capsule; C1 = left oxygen hose; C2 = right oxygen hose; D1 = left sticky pads at ends of arms for holding capsule at work site (arms shown retracted in closed-door position); D2 = right sticky pads at ends of arms for holding capsule at work site (arms retracted in closed-door position); E = tool storage; F = hydrogen peroxide propellant tank; G = pressure seal curtain deployment channel; H = Whipple Bumper hull. Image credit: Chrysler Corporation/DSFPortree
Dutzmann and Dunford thus proposed an intermediate developmental step in spacewalk technology: a three-foot-diameter, eight-foot-tall "Transportation and Work Station Capsule," normally kept unpressurized, that would provide the space-suited astronaut with an extra layer of protection from injury, a shelter in case of suit damage, improved mobility, worksite lighting, and places inside to store up to 30 pounds of tools. With a 230-pound space-suited astronaut inside and a full load of 30 pounds of hydrogen peroxide propellant, the cylindrical capsule would weigh just 550 pounds.

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 legs to hold the capsule in place at the work site.

A unique feature of Chrysler's capsule was its "pressure seal curtain" system. In the event of a suit puncture or tear, a transparent plastic sheet sleeve would rise up a deployment "channel" from a donut-shaped storage area in the capsule floor to surround and enclose the astronaut.

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 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)

More Information

The Spacewalks That Never Were: Gemini Extravehicular Planning Group (1965) (how Soviet deception concerning Leonov's spacewalk led NASA to plan complex Gemini spacewalks)

Rocket Belts and Rocket Chairs: Lunar Flying Units (1960s plans for rocket-powered lunar surface transportation)