Rube Goldberg's Space Shuttle

By mid-1971, this was one of the two leading Space Shuttle design configurations. The first stage, bearing the letters "USA" and a single stabilizing oversized tail fin, might have been derived from the Saturn V S-IC first stage. Image credit: NASA.

For Americans above a certain age, the phrase "Rube Goldberg Machine" elicits a chuckle or perhaps a sneer, depending on the context of its use. Rube Goldberg (1883-1970) was an award-winning cartoonist. His most famous drawings were of whimsical machines that accomplished a simple task in the most complex way possible.

It is not too unkind, given that most of the factors that led to its complexity were outside of NASA's control, to place the Space Shuttle in the category of a Rube Goldberg Machine. It began as a simple idea — economically deliver crews, supplies, and equipment to an Earth-orbiting Space Station — and, through conflicting, expanding demands placed on it, unwise cuts in funding for its development, and deferral of the Space Station it was meant to serve, grew into something large, complex, and costly.

Throughout the Space Shuttle design process, NASA fought a rearguard action to preserve reusability. In 1969, the U.S. civilian space agency sought a fully reusable Shuttle design with a piloted Booster and a piloted Orbiter, each carrying liquid propellants for placing the Orbiter into Earth orbit. Inadequate funding support from the Nixon White House and Congress coupled with a U.S. Air Force requirement that the Orbiter include a payload bay at least 60 feet long and 15 feet wide soon made that design untenable, however.

NASA and its contractor teams took a rapid series of cost-cutting steps during 1970-1972. The design process became messy and almost untrackable, with concepts proposed, abandoned, and proposed again in rapid succession or even simultaneously by different contractor and NASA teams.

The piloted Booster shrank after engineers tacked a pair of reusable solid-propellant rocket motors onto its tail. Then it ceased to be piloted, becoming part of what amounted to a three-stage rocket. Riding bolted to the top or side of the Booster's expendable second stage, the piloted Orbiter became in effect a reusable third stage that would complete its climb to Earth orbit by burning liquid hydrogen (LH2) fuel and liquid oxygen (LOX) oxidizer carried in tanks inside its streamlined fuselage.

In part to prevent the Orbiter from growing out of all proportion as its payload bay grew, NASA moved low-density LH2 out of the Orbiter fuselage into cheap expendable drop tanks. The move also ended worries about safe containment within the Orbiter of volatile LH2, which is prone to slow seepage even through solid metal.

The Orbiter carried LOX for its ascent to orbit inside its fuselage for a little while longer. By August 1971, however, the delta-winged Orbiter contained only enough propellants to maneuver in orbit and to slow itself so that it could deorbit and reenter Earth's atmosphere. At first, its orbital maneuvering engines were expected to burn LH2/LOX, but then NASA substituted hypergolic (ignite-on-contact) propellants.

During the same period, the preferred Shuttle stack design flip-flopped between two candidates. One (image at top of post) had two LH2/LOX stages stacked one atop the other. The first-stage engines were mounted directly beneath their stage, as on a conventional rocket. The engines for the second stage were built into the tail of the Orbiter mounted on its side. They would ignite at altitude after the first stage separated and, owing to their position on the side of the second stage, would thrust off center.

The first stage would be reusable; after depleting its propellants and separating from the second stage, it would deploy parachutes and lower to a gentle landing at sea, where it would bob with its engines pointed at the sky. A specially designed ship would then recover it and tow it to port for refurbishment. The second stage would reach orbit attached to the Orbiter, then would separate, reenter, and break up over the ocean.

The other candidate design (image below) featured a reusable Orbiter and a pair of reusable LH2/LOX boosters mounted on the sides of a single large expendable External Tank (ET). The lightweight ET's interior would be split between a small tank for LOX and a large one for LH2. Both the twin boosters and the tail-mounted Orbiter engines would ignite on the launch pad. The side-mounted boosters would expend their propellants and fall away about two minutes after liftoff. They would each deploy parachutes and descend to a gentle ocean landing to await recovery. Pipes leading from the ET tanks would feed propellants to the Orbiter's engine cluster throughout ascent to orbit.

That looks familiar: the other Space Shuttle stack design leading the pack by mid-1971. Note off-center thrust plumes from the delta-winged Orbiter's tail-mounted engines (lower left). Image credit: NASA.

In a final cost-cutting move, NASA replaced the reusable liquid-propellant boosters with reusable solid-propellant boosters. The liquid-propellant boosters could be turned off in the event of a major malfunction; the solid-propellant boosters could not.

Mounting engines on the reusable Orbiter meant that they would be returned to Earth for refurbishment and reuse. The resulting off-center thrust troubled many engineers, however, because it meant that thrust forces would be transmitted through the Orbiter to the second stage (in the case of the first Shuttle design alternative) or the ET (in the case of the second). This would place added stress on the Orbiter, its links to the second stage or ET, and the second stage or ET. Links between the second stage/ET and the Orbiter would include propellant pipe connections, which engineers expected would be prone to leaks even without the added stress of off-center thrust.

Off-center thrust also meant that the short LOX tank, when full the heaviest part of the second stage or ET, had to be situated atop the long LH2 tank, the lightest part of the second stage or ET. Putting the dense LOX on top helped the Shuttle stack to remain stable in flight as the Orbiter's engines rapidly emptied the second stage or ET and the stack's center of gravity shifted, but it also placed added stress on the second stage or ET structure. Because the LOX at the top of the second stage/ET needed a long pipe to reach the engines on the Orbiter's tail, the arrangement also increased the risk of propellant pipe rupture.

During the 1970-1972 Shuttle design evolution, several engineers proposed and re-proposed a novel alternative to off-center thrust: a cluster of reusable engines that would operate attached to the bottom of the expendable second stage or ET. After the Orbiter reached Earth orbit and its main engines shut down, the engine cluster would be detached from the second stage or ET and, using an armature system of booms or struts, be swung into a storage compartment inside the aft end of the Orbiter fuselage.

The second stage or ET would then be cast off. In the case of the ET, vented residual propellants would cause it to tumble, rapidly reenter the atmosphere, and break up. When the astronauts on board the Orbiter completed their mission in Earth orbit, the engine cluster would return to Earth with them, where it would be removed from the compartment, refurbished, and mounted on a new second stage or ET.

The NASA Manned Spacecraft Center — renamed the Lyndon B. Johnson Space Center (JSC) in February 1973 — managed Space Shuttle development. Shuttle engineers were quick to reject the swing-engine design. They did this mainly because its armature system seemed overly complex and thus prone to malfunctions.

The Rube Goldbergian swing-engine concept would not die, however. In March 1974, in fact, JSC chief of engineering Maxime Faget (co-designer of the Mercury capsule and a 1969 all-reusable Shuttle) and JSC engineers William Petynia and Willard Taub filed an application to patent the swing-engine design. By then, the decision to settle on the second stack configuration described above was two years old (NASA Administrator James Fletcher announced the choice on 16 March 1972).

The JSC engineers proposed three swing-engine design approaches. The U.S. Patent Office granted their patent on 30 December 1975.

All of their design approaches would, they argued, eliminate stress on the Shuttle stack caused by off-center thrust, enable transposition of the ET LOX and LH2 tanks, and improve stack flight characteristics during ascent through Earth's atmosphere. The results would, they explained, include a lighter Orbiter and ET, more payload, and greater safety.

As a bonus, the swing-engine system would enable the Orbiter to adjust its center of gravity after it released or took on an orbital payload, thus improving its reentry and atmospheric gliding flight characteristics. It would do this by shifting the engine cluster forward toward the back of the Orbiter payload bay using the same mechanical armature system that would swing the engines away from the bottom of the ET. The armature system would also serve to gimbal (swivel) the engines to steer the Orbiter/ET stack during ascent to orbit.

Other benefits would spring from the swing-engine design. The ET and engine cluster could be tested together without an Orbiter attached. All piping linking the Orbiter and the ET would be eliminated. Separable links between the ET and the engine cluster would be required, of course. The engine cluster would, however, be quite small and light compared to the Orbiter; this meant that it could be easily mounted on the ET, tested for leaks, and (if necessary) removed and repaired before flight.

First method for transferring engine cluster from aft end of the ET to storage in the Orbiter aft fuselage. 1 = ET; 2A = mounting ring for four engines (in thrust position on ET); 2B = mounting ring for four engines (in stored position in Orbiter aft fuselage); 3 = joint linking lower armature to engine ring (1 of 2); 4 = lower armature strut (1 of 2); 5 = upper armature strut (1 of 2); 6 = joint linking upper armature to Orbiter aft fuselage (1 of 2); 7 = trailing edge of wing (1 of 2); 8 = opening in aft fuselage for engine cluster storage; 9 = solid-propellant ascent abort rocket (1 of 2); 10 = vertical stabilizer. Image credit: NASA/U.S. Patent Office.

The JSC engineers' first swing-engine design, illustrated above, assumed a quartet of Shuttle engines, a single vertical stabilizer, and an aft-pointing fuselage opening. The armature system would swing the engines into the fuselage so that their engine bells pointed aft.

The second design, illustrated below, assumed three Space Shuttle engines in a vertical row and an Orbiter with twin out-splayed vertical stabilizer fins. The armature system would swing the engines up and over the aft end of the Orbiter fuselage and lower them into a rectangular slot between the fins. After a horizontal landing on Earth, their engine bells would point skyward.

Second method for transferring the Space Shuttle engine cluster from the aft end of the ET to the storage space in the Orbiter aft fuselage. 1 = Orbiter payload bay; 2 = LOX tank in aft end of ET; 3 = ET; 4 = vertical stabilizer (1 of 2); 5A = engine cluster in thrust position on aft end of External Tank; 5B = engine cluster in stowed position in Orbiter aft fuselage; 6A = centerline of engine cluster in thrust position; 6B = centerline of engine cluster in stowed position; 7A = armature strut for transferring engine cluster (thrust position) (1 of 2); 7B = armature strut for transferring engine cluster (stowed position) (1 of 2); 8 = center armature joint (1 of 2); 9 = path of center armature joint (8) during engine cluster transfer to stowed position. Image credit: NASA/U.S. Patent Office.

The JSC engineers' third swing-engine design also assumed three engines arranged in a vertical row, but could be used with either single or double vertical stabilizer Orbiter configurations. The armature system would tilt the engine cluster 45° and slide it on rails into a rear-facing opening in the aft fuselage. As with their second design, the engine bells would point upward after the Orbiter glided to a landing.

Orbital Flight Test-1 (OFT-1), also known as Space Transportation System-1 (STS-1), the first flight of the Space Shuttle. Columbia lifted off from Launch Complex 39A at Kennedy Space Center, Florida, on 12 April 1981, and landed at Edwards Air Force Base, California, two days later. Veteran astronaut John Young was Commander and rookie Robert Crippen was Pilot. Image credit: NASA.

The swing-engine concept had, of course, become a mere curiosity well before the U.S. Patent Office granted Faget, Petynia, and Taub their December 1975 patent. Following the March 1972 selection of the Shuttle stack configuration, NASA awarded Rockwell International the contract to build Space Shuttle Orbiters on 26 July 1972. The company built a total of five space-worthy Orbiters, each with three Space Shuttle Main Engines mounted in a triangle on their aft fuselages, over a span of more than 20 years.

The Orbiters functioned admirably, though they needed far more costly refurbishment and maintenance than NASA envisioned when it proposed its all-reusable Space Shuttle design in 1968-1969. Booster system malfunctions claimed two Orbiters and their seven-person crews, however. Challenger was destroyed on 28 January 1986 when a solid-propellant booster field joint burned through, leading to ET structural failure and Orbiter break-up 73 seconds after launch. Columbia, the first Orbiter to orbit Earth (12-14 April 1981), was lost after foam insulation on the ET it rode broke loose during ascent and struck and damaged its wing leading edge. This led to wing structural failure and Orbiter breakup during reentry on 1 February 2003, at the end of a 16-day mission.

Sources

Patent No. 3,929,306. Space Vehicle System, Maxime A. Faget, William W. Petynia, and Willard M. Taub, NASA Johnson Space Center, 5 March 1974 (filed), 30 December 1975 (granted).

Space Shuttle: The History of the National Space Transportation System, the First 100 Missions, Dennis R. Jenkins, 3rd Edition, 2008.

Wikipedia: Rube Goldberg Machine (https://en.wikipedia.org/wiki/Rube_Goldberg_machine — accessed 28 November 2016)

More Information

George Landwehr von Pragenau's Quest for a Stronger, Safer, Better Space Shuttle

Series Development: A 1969 Plan to Merge Saturn V and Shuttle to Spread Out Space Program Cost

One Space Shuttle, Two Cargo Volumes: Martin Marietta's Aft Cargo Carrier (1982)

An Apollo Landing Near the Great Ray Crater Tycho (1969)

Splat! Tycho crater (lower center) is the the most prominent bright surface feature in this NASA image of the full Moon. Linear rays originating at the crater can be traced outward for hundreds of kilometers.

Of the seven automated Surveyor spacecraft NASA launched to the Moon between May 1966 and January 1968, only the last, Surveyor 7, aimed for a target selected specifically for its scientific value. Surveyors 2 and 4 failed, while Surveyors 1, 3, 5, and 6 soft-landed at flat mare (basalt plain) sites in the "Apollo Zone," the near-equatorial band readily accessible to piloted Apollo Lunar Module (LM) spacecraft. The successful Apollo Zone Surveyors performed valuable scientific investigations, but their main purpose was to image their landing sites and test surface bearing strength to help assure mission planners that the lunar terrain was smooth and stable enough to permit Apollo astronauts to land safely.

Surveyor 7, by contrast, aimed for the rugged northern flank of Tycho crater, one of the most prominent features on the Moon's Earth-facing nearside hemisphere. The 85-kilometer-wide asteroid impact scar, centered at 43° south latitude in heavily cratered highlands terrain, is surrounded by an extensive system of bright rays best viewed when the Moon is full. The rays are made up of ejecta blasted out when Tycho formed about 110 million years ago. As ejecta fell back onto the Moon, it stirred up more material, generating a ray cascade extending up to 1500 kilometers from Tycho.

Surveyor 3 (above) served as a pinpoint landing target for Apollo 12 astronauts Charles Conrad and Alan Bean in November 1969. During their second moonwalk, they stopped by the derelict lander to collect parts and take pictures for engineering analysis. Surveyor 7 resembled Surveyor 3, but included noticeable differences; most obvious was the addition of the deployable alpha-scattering instrument. Image Credit: NASA.

Hand-laid mosaic of images from Surveyor 7 illustrating the rocky, rolling nature of the terrain north of Tycho. Image credit: NASA/USGS.

Surveyor 7 lifted off from Cape Kennedy atop an Atlas-Centaur rocket on 7 January 1968. It landed on 10 January at 40.9° south latitude, 11.4° west longitude, just 2.5 kilometers from its intended target and 30 kilometers from Tycho's rim, on the ejecta blanket surrounding the crater.

Less than an hour after touchdown, the three-legged, solar-powered lander returned the first of more than 21,000 images it would beam to Earth. Some of these were stereo pairs, enabling scientists to precisely locate the many varied rocks and boulders visible in the field of view of Surveyor 7's scanning camera. Other images were assembled into panoramic mosaics that show lunar landscape features up to 13 kilometers away from the lander.

Among the features most intriguing to lunar scientists were so-called "lakes" of relatively dark material. They lay in depressions and had relatively flat surfaces. Curving, branching trenches etched many of these small dark plains. Some scientists interpreted the lakes as signs of recent volcanic activity, the "holy grail" of 1960s lunar exploration.

Tycho, its ejecta blanket, and the Surveyor 7 landing site as imaged by NASA's Lunar Reconnaissance Orbiter (LRO). The spacecraft entered lunar polar orbit in June 2009. The ejecta surrounding the crater partly covers and "blurs" lunar surface features that existed before Tycho was formed. Image credit: NASA.

In keeping with its science-focused mission, Surveyor 7 carried more scientific apparatus than any of its predecessors. Besides its camera, the lander carried an alpha-scattering device for determining the composition of rocks and dirt and an arm-mounted digger. The former had flown previously on Surveyor 5 and Surveyor 6; the latter on Surveyor 3.

At first, the alpha-scattering device failed to deploy, but flight controllers were able to direct the digger to push it down into contact with the lunar surface. They later used the arm/digger to position the alpha-scatterer on a rock and in a trench the digger had excavated. They found that the surface material at Surveyor 7's highlands landing site contained more aluminum than did that at the mare sites the other Surveyors explored.

Controllers were unable to place the alpha-scatterer in contact with boulders on a low ridge near Surveyor 7, some of which might have been blasted from kilometers below the lunar surface by the Tycho impact. They were far beyond the digger's 1.52-meter maximum reach. Nor were controllers able to move the instrument to the dark material of the lakes, the nearest of which lay about a kilometer from the lander. When the Surveyor 7 mission ended on 21 February 1968, much was known about its complex landing site, but much else remained mysterious.

Lunar Orbiter image of the Surveyor 7 landing area. The two dotted lines originating at the Surveyor 7 ("S.VII") touchdown point indicate the limits of the field of view of the lander's scanning camera. North is toward the top. Prominent in the right half of the image is a dark lake-like feature, the "shore" of which is located about a kilometer away from Surveyor 7. Image credit: NASA.

The lakes and the tantalizing variety of rocks near Surveyor 7 caused some lunar scientists to call for an Apollo mission to the site. It was far outside the Apollo Zone, but could be reached during certain times of year if conservative Apollo mission rules were relaxed.

In August 1969, less than a month after Apollo 11, the first piloted Moon landing mission, U.S. Geological Survey (USGS) scientists worked with Bellcomm, NASA's Apollo planning contractor, to rough out the surface portion of an Apollo Tycho mission. It would begin with a pinpoint LM landing a kilometer southeast of Surveyor 7.

The pinpoint landing would be required if the astronauts were to follow the geologic traverse routes the Bellcomm/USGS team planned. The LM descent stage would carry enough propellants to enable the Tycho mission crew to at least partly compensate if their LM missed its designated touchdown point. This was deemed an especially important capability because the Apollo 11 LM Eagle had landed off course at the edge of its landing ellipse.

On the basis of Surveyor 7 and Lunar Orbiter V images, the Bellcomm/USGS team judged that the Tycho site was too rocky for a jeep-like lunar rover to navigate. They suggested that the astronauts explore on foot within an operational radius of about 2.5 kilometers centered on their LM.

Proposed new "constant volume" hard suits tougher and more flexible than the mostly fabric Apollo suits would, they anticipated, make possible speedy hikes over rugged terrain. The new suits would also permit the astronauts to operate on the surface for up to seven hours at a stretch. They would spend 54 hours at the Tycho landing site, providing enough time for three seven-hour traverses.

LRO image of the Surveyor 7 landing area. Please refer to the previous image for a scale bar. The arrow points to the derelict lander, which is just visible because of the shadow it casts on the surface. Technology advancement means that the image is sharper than the previous Lunar Orbiter image: individual boulders about the size of the lander are clearly seen, as are details of the lake-like melt "pond" and small impact craters. Image credit: NASA.

The Bellcomm/USGS team planned that, during Traverse I, one astronaut would deploy an Apollo Lunar Scientific Experiment Package (ALSEP) about 1.1 kilometers east of the LM. The ALSEP would include a passive seismometer. In addition to establishing a "far southern" station in the Apollo seismic network, the instrument would exploit natural moonquakes and asteroid impacts to chart Tycho's subsurface structure. The ALSEP might also include a heat-flow experiment to help scientists determine whether volcanism had occurred recently at the site, a laser retroreflector, a magnetometer, and a gravimeter.

The other astronaut, meanwhile, would walk along the low ridge visible from Surveyor 7 and sample the boulders there. The two moonwalkers would then meet up and return to the vicinity of the LM. Traverse I would total about 3.5 kilometers.

During Traverse II, at about 6.25 kilometers the longest of the Tycho mission moonwalks, the astronauts would strike north together to the "shore" of a prominent kilometer-wide dark lake. They would photograph and sample the branching trenches, then walk to a point 2.6 kilometers from their LM to sample "dark flow dome material." On the way back to the LM, they would visit Surveyor 7 to collect samples of lunar materials it had examined and salvage parts of the robot lander for engineering analysis.

The final traverse of the Apollo Tycho mission would see the astronauts walk south about 1.3 kilometers to sample another dark lake, then travel a further 1.4 kilometers to sample subsurface material exposed by a small fresh impact crater. They would then hike half a kilometer to a raised "flow levee" surrounded by "late smooth flow materials." Traverse III would total 5.25 kilometers. In all, the astronauts would walk 15 kilometers and collect between 100 and 200 pounds of samples during their three moonwalks.

The Bellcomm/USGS team acknowledged that the Tycho site presented challenges beyond its position outside the Apollo Zone. It was rugged and undulating, so the astronauts were likely to lose line-of-sight contact with the radio antennas on their LM as they walked. The LM would relay signals from their space suit radios, so they might temporarily lose radio contact with Earth. In addition, the site had not been imaged from orbit at the same high resolution as other candidate Apollo sites.

The team suggested that, if no high-resolution orbital images of the site could be obtained and if this continued to be considered a major drawback, then the Apollo Tycho mission could land closer to Surveyor 7. Though doing so would enable a landing in a well-characterized area, it would create its own problems. The most serious of these would be to place much of the Traverse III loop beyond the planned 2.5-kilometer operational radius of the mission's moonwalks.

This map of the landing sites of all the successful Surveyors shows how far south Surveyor VII landed. No other spacecraft has soft-landed so far from the lunar equator. Image credit: NASA.

During 1970, in the aftermath of the near-disastrous Apollo 13 mission, NASA engineers, mission planners, managers, and astronauts, never enthusiastic about the Tycho site proposal, rejected the region as too rugged for a safe Apollo landing. Some scientists were, however, not easily deterred: they continued to sing the site's praises as late as 1972.

They pointed to the fact that Surveyor 7 had successfully landed without the precise terminal guidance an astronaut would provide. They hoped that Apollo 16 or 17 might be diverted to Tycho. In the end, however, no Apollo mission visited Surveyor 7, leaving to it the honor of the highest-latitude/farthest-south landing site of any spacecraft that has soft-landed on the Moon.

The dark lake-like features observed near Tycho are known today to be patches of melt material that flowed and was thrown outward from Tycho during its explosive formation, not signs of recent volcanic activity. Impact melt flows are found inside and around many large young impact craters. Melt flow features are rare close to older craters because the steady rain of micrometeoroids and small asteroids that strikes the Moon splinters them into dust and boulders and gradually renders them indistinct.

Sources

Surveyor VII: A Preliminary Report, NASA SP-173, NASA Surveyor Program Office, May 1968.

Surveyor Program Results, NASA SP-184, Surveyor Program, NASA, 1969.

"Tycho - north rim," H. Masursky, G. Swann, D. Elston, and J. Slaybaugh, 14 August 1969 (revised 15 August 1969).

Memorandum, J. Slaybaugh to J. Llewellyn, "Tycho Rim Engineering Evaluation - Case 320," Bellcomm, Inc., 28 August 1969.

To A Rocky Moon: A Geologists' History of Lunar Exploration, Don E. Wilhelms, The University of Arizona Press, 1993, pp. 242, 287, 312.

More Information

"Essential Data": A 1963 Pitch to Expand NASA's Robotic Exploration Programs

If an Apollo Lunar Module Crashed on the Moon, Could NASA Investigate the Cause? (1967)

"A Continuing Aspect of Human Endeavor": Bellcomm's January 1968 Lunar Exploration Program

"Essential Data": A 1963 Pitch to Expand NASA's Robotic Exploration Programs

The derelict Surveyor 3 lander (left) became a pin-point landing target for Apollo 12 in November 1969. Image credit: NASA.

The Apollo Program dominated NASA in the 1960s. Its chief aims were to place a man on the Moon ahead of the Soviet Union and before 1970. In December 1963, three of NASA's four approved robotic exploration programs — Ranger, Surveyor, and Lunar Orbiter — focused on the Moon. The fourth, Mariner, aimed at Mars and Venus. Apollo requirements — the need to find safe landing sites and to understand lunar conditions well enough to design the Apollo Lunar Excursion Module lander — dominated the Moon programs. Beating the Communists to Venus and Mars was a major motivator for Mariner. In short, Cold War geopolitics ruled, not scientific exploration.

On 2 December 1963, high-level NASA Lunar and Planetary Program staffers briefed NASA Administrator James Webb, Deputy Administrator Hugh Dryden, and Associate Administrator Robert Seamans. Their aim: to shift NASA's robotic program priorities toward science.

In his introductory presentation, Lunar and Planetary Program Director Oran Nicks solicited funding to enhance the four extant programs with new science-focused missions. He also sought funding to initiate the new Voyager Mars/Venus program.

Nicks reminded Webb, Dryden, and Seamans that Mariner II had scored an impressive first by flying past Venus in December 1962. He noted that, one year after achieving world's first successful planetary flyby, NASA's entire approved planetary program consisted of just two Mars flybys (Mariners III and IV, set for launch in November 1964). Mariner missions planned after 1964 were, he stressed, "not firm." He blamed funding cuts and persistent problems with the finicky cryogenic liquid hydrogen/liquid oxygen Centaur upper stage for this surprising failure to follow up on Mariner II's success. Nicks then turned the briefing over to his Lunar and Planetary Program managers.

By the time Ranger Program Manager N. William Cunningham stood before Webb, Dryden, and Seamans, Rangers I through V had failed. Ranger I (launched 23 August 1961) and Ranger II (launched 18 November 1961), "Block I" vehicles meant to gather data on micrometeoroids, radiation, solar plasma, and magnetic fields in high elliptical Earth orbit, had fallen victim to Atlas-Agena B rocket malfunctions, as had Ranger III (launched 26 January 1962), a Block II spacecraft meant to rough-land on the Moon a spherical balsa-wood capsule bearing a seismometer. Ranger IV (launched 23 April 1962) and Ranger V (launched 18 October 1962), also Block IIs, had suffered electrical failures.

The Block II Ranger spacecraft with spherical balsa-wood "lunar capsule." The solid-propellant retrorocket was intended to ignite during the final seconds of the spacecraft's flight, slowing the capsule so that it could make a survivable rough landing on the Moon. Image credit: NASA.

Cunningham began his presentation by telling Webb and his deputies that Ranger VI, a Block III spacecraft designed to snap photos of the Moon while plummeting toward destructive impact, would launch in January 1964. He assured them that his engineers had made "many changes in. . .the spacecraft. . .in an effort to improve its chances for success."

Four Block IIIs (Rangers VI through IX) were expected to photograph the moon by August 1964, then six Block Vs (Rangers X through XV) would fly in 1965-1967. Cunningham noted that NASA planned to spend $92.5 million on Block V Rangers. Much like the Block IIs, Block V Rangers would attempt to rough-land capsules containing instruments, including possibly a TV system for beaming to Earth images from the Moon's stark surface. Cunningham called the Block Vs "the only backup" the U.S. had in place for the Surveyor Program, then urged Webb and his lieutenants to add $50 million to the Block V Ranger development budget.

Surveyor 1 Atlas-Centaur rocket liftoff, 30 May 1966. The lunar spacecraft soft-landed on 2 June 1966 within the Flamsteed Ring, an ancient crater inundated by lava flows that formed Oceanus Procellarum. The three-legged lander returned data during lunar daylight periods, when its single solar panel could make electricity to operate its instruments and radio. Surveyor 1 outlasted its expected lifespan; contact was not lost until 7 January 1967. Image credit: NASA.

Surveyor Program Manager Benjamin Milwitzky took the floor next. He told Webb, Dryden, and Seamans that his program's main purpose was to gather "essential data about the lunar surface. . .needed for manned landings." An Atlas-Centaur rocket would launch the first Surveyor soft-lander in 1965. Milwitzky reported that Surveyor had been intended to carry 300 pounds of science instruments, but that Centaur upper stage problems had forced a cut to between 70 and 100 pounds. He told them that, while the reduced payload would be adequate for scouting Apollo landing sites, many lunar science opportunities would have to be abandoned — unless NASA took action.

Milwitzky proposed that Surveyor's science payload be restored by adding the corrosive element fluorine to the Atlas rocket's liquid oxygen propellant. He urged Webb, Dryden, and Seamans to spend $40 million in 1964-1966 to develop this energetic oxidizer mix for the Atlas.

If they agreed to beef up the Atlas, then the first advanced science-focused Surveyor could fly in 1967. A typical advanced Surveyor lander might include a Radioisotope Thermoelectric Generator to provide its instruments with long-term electricity, a drill for subsurface sample collection, on board sample analysis gear, a geophysical probe that could be lowered down the drill bore hole, a seismometer, a mast-mounted TV system for imaging a large area around the lander in stereo, and a small rover for exploring the landing site and emplacing explosive seismic experiment packages a safe distance away from the lander.

Milwitzky ended his presentation by proposing that NASA increase the number of planned Surveyor missions from 17 to 29. He estimated that the 17-mission program would cost $425.5 million; adding 12 more missions would cost an additional $352 million.

Milwitzky then handed off to Lee Scherer, Lunar Orbiter Program Manager. Scherer began his presentation by reminding Webb and his deputies that Lunar Orbiter missions 1 through 5 had been approved for 1966-1967, and that Lunar Orbiters 6 through 10, while not yet formally approved, were planned for 1967-1968.

Lunar Orbiter spacecraft would, Scherer said, aim "to obtain, initially, scientific data about the [M]oon and its environment of special importance to the Apollo mission." The approved Lunar Orbiters were intended mainly to photograph areas of the lunar surface accessible to Apollo spacecraft (that is, close to the equator on the Nearside, the lunar hemisphere that forever faces Earth).

Scherer proposed that NASA fly five science-oriented Lunar Orbiters in 1968-1969. These might enter orbits inclined to the lunar equator, enabling them to pass over scientifically interesting surface features beyond the equatorial Apollo landing zone. They might also enter lunar polar orbit for whole-Moon mapping. Gamma-ray spectrometers and infrared sensors might be used to map lunar mineralogy. Scherer also proposed a mission dedicated to exploring Moon/Sun plasma interactions and any lunar magnetic field that might exist. Lunar Orbiters 1 through 10 would cost $198 million; Scherer estimated that adding Lunar Orbiters 11 through 15 would boost the program's cost by $95 million.

The Jet Propulsion Laboratory (JPL) in Pasadena, California, first proposed the ambitious Voyager Mars/Venus robotic spacecraft series in 1960. In December 1963, Voyager was not yet an approved NASA program, though studies continued at JPL and NASA Headquarters. According to Donald Hearth, the Lunar and Planetary Program Office staffer responsible for Voyager, NASA had allotted $7.1 million for Voyager studies in 1962-1963. Of this, all but $1.3 million had been shifted to cover funding shortfalls in other programs.

The Voyager spacecraft design as of mid-1967. The lander, bundled up in a conical black Mars atmosphere entry capsule and a back-shell, is visible on the spacecraft at upper right. Solar arrays form a flat ring around Voyager's protruding rocket motors and a skeletal high-gain radio antenna points toward Earth. Image credit: NASA.

Assuming that Congress approved its development, the Voyager spacecraft would comprise three parts: a 2000-pound orbiter with a 2000-pound retro stage and a 2500-pound lander. These would leave Earth together on a two-stage Apollo Saturn IB rocket augmented by a Centaur third stage. For Mars missions, the Voyager lander would separate from its orbiter during approach to the planet, enter the atmosphere directly from its interplanetary trajectory, and land within 500 kilometers of a target site. It would explore its landing site for six months. After lander separation, the Voyager orbiter would fire the retro stage to slow down so that the gravity of Mars could capture it into orbit.

Hearth told Webb, Dryden, and Seamans that the Voyager 1969 Mars lander would carry an impressive suite of 38 science instruments, including two TV cameras, a sample-collection drill, biology detectors, a microscope, a seismometer, a microphone, and meteorology sensors. Voyager 1969 Mars orbiter instruments would include multicolor stereo TV cameras, an infrared spectrometer for determining surface composition over wide areas, a magnetometer for charting the martian magnetic field, a cosmic dust detector, and a solar X-ray detector.

Though more capable than any other U.S. lunar or planetary spacecraft, the Saturn IB/Centaur-launched Voyagers would pale next to planned Saturn V-launched Advanced Voyagers. Hearth reported that the Saturn V rocket could launch to Mars a 3100-pound orbiter and one or more direct-entry landers weighing a total of 33,000 pounds.

These "large lander laboratories" might include rovers, balloons, and hovercraft to enable exploration beyond their landing sites. Alternately, the Advanced Voyager orbiter might carry a large retro stage that would enable it to retain its lander until after it achieved Mars orbit. Lander descent from Mars orbit would improve landing accuracy, Hearth explained.

Hearth estimated that the Voyager Program would cost $2.9 billion over 11 years. Assuming timely approval, NASA could launch Voyager test flights in 1967 and 1968, Voyager Mars missions in 1969, 1971, and 1973, Voyager Venus missions in 1970 and 1972, and Advanced Voyager Mars missions in 1973 and 1975.

Within a week of the 2 December 1963 briefing, James Webb informed Oran Nicks that NASA could not afford to expand its robotic lunar and planetary programs in support of science. In fact, by 13 December, when NASA Associate Administrator for Space Sciences and Applications Homer Newell announced that the Block V Ranger development was cancelled, it had become clear that NASA would cut back its robotic lunar programs, sharply limiting opportunities for science-focused missions. Ranger, Surveyor, and Lunar Orbiter became victims of their own success; almost as soon as they proved themselves to be capable scientific exploration machines by providing the data Apollo engineers and planners needed, NASA top brass opted to end them and move on.

In all, scientists were granted just four robotic missions specifically for scientific lunar exploration. Though Ranger VI was an embarrassing failure, Ranger VII and Ranger VIII succeeded, and the program concluded with the successful science-focused Ranger IX mission to Alphonsus crater in March 1965. All were Block III spacecraft.

Five Lunar Orbiters mapped the Moon between August 1966 and January 1968. Lunar Orbiters 4 and 5 were science-focused missions in a near-polar lunar orbits. Surveyor ended with its seventh flight, a science-focused mission to a site just north of the bright ray crater Tycho in January 1968.

After Apollo, NASA received data from instruments left behind on the Moon by the Apollo astronauts. These were turned off in September 1977. The U.S. civilian space agency then largely abandoned the Moon, scene of its greatest triumph, for more than 20 years.

Mariner 9 carried a large propellant supply (hidden beneath the white cover) so that it could slow down and capture into Mars orbit. It left Earth on an Atlas-Centaur rocket on 30 May 1971 and became the world's first planetary orbiter on 14 November 1971. Image credit: NASA.

Mariner 10 left Earth on 3 November 1973 and flew past Venus on 5 February 1974. Using Venusian gravity and orbital momentum, it performed the world's first gravity-assist planetary flyby. This placed it on course for a trio of Mercury flybys in 1974-1975. Image credit: NASA.

The 1960s and 1970s saw a total of seven successful Mariners and four successful Mariner-derived planetary spacecraft. In July 1965, Mariner IV became the first spacecraft to fly past Mars. No Mariner ever carried an atmosphere probe, but Mariner 9 (May 1971-October 1972) became the first Mars orbiter (and, indeed, the first planetary orbiter in history). Mariner 10, officially the last spacecraft of the Mariner series, became the first to fly past Mercury (in fact, it flew by the planet three times, in March 1974, September 1974, and March 1975).

Voyager became an official NASA program in 1965, just in time to see its design scrapped and its estimated cost nearly doubled. Mariner IV was the culprit: it revealed that the planet's atmosphere was 10 times thinner than expected. Because of this, Voyager would need heavy landing rockets in addition to parachutes.

The star-crossed program lingered on until August 1967, when Congress refused to fund its continued development. NASA then proposed a cut-price Mariner-derived Mars landing program, called Viking, which received approval in 1968 from a Congress increasingly aware of Soviet plans to explore the Solar System with automated rovers and sample-returners. Two Viking orbiter-lander pairs explored Mars beginning in 1976. The name Voyager was subsequently resurrected for twin Mariner-derived outer planets flyby spacecraft — originally named Mariner Jupiter-Saturn — which departed Earth in 1977.

Viking Orbiter 1 releases Viking Lander 1 in Mars orbit, 20 July 1976. The Lander (below) is stowed inside an aeroshell; a bioshell for protecting the Lander from terrestrial contamination after it was sterilized remains attached to the Orbiter, which resembles Mariner 9. Image credit: NASA.

Of all the Mariner-derived spacecraft launched, only the most distant remain functional. Voyager 1 flew past Jupiter (1979) and Saturn (1980); Voyager 2 conducted a grand tour of Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989). At this writing, Voyager 1 is located 137.6 Astronomical Units (AU) from Earth, while Voyager 2 is 113.3 AU from Earth. (An AU, the distance from the Sun's center to the Earth's center, is approximately 149.6 million kilometers.) Image credit: NASA.

Sources

"Briefing for the Administrator on Possible Expansion of Lunar and Planetary Programs," NASA Headquarters, 2 December 1963.

Astronautics and Aeronautics, 1963, NASA SP-4004, 1964, p. 477.

Lunar Impact: A History of Project Ranger, NASA SP-4210, R. Cargill Hall, NASA, 1977.

The Voyage of Mariner 10: Mission to Venus and Mercury, NASA SP-424, James A Dunne & Eric Burgess, NASA, 1978.

On Mars: Exploration of the Red Planet, 1958-1978, NASA SP-4212, Edward Clinton Ezell & Linda Neuman Ezell, NASA, 1984.

Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, NASA SP-2002-4524, Monographs in Aerospace History Number 24, Asif A. Siddiqi, 2002, pp. 88-90, 105-106, 110-112.

Voyager: The Interstellar Mission (http://voyager.jpl.nasa.gov/ — accessed 19 November 2016).

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One-Man Space Station (1960)

Final Mercury: the black Mercury-Atlas 9 spacecraft and its gleaming Atlas booster rocket in October 1963. Image credit: NASA.

Probably the prize for "smallest space station design ever proposed" should go to McDonnell Aircraft's One-Man Space Station. On 24 August 1960, engineers with St. Louis-based McDonnell, the Mercury spacecraft prime contractor, described the mini-station to members of the Space Task Group (STG) at NASA's Langley Research Center in Hampton, Virginia.

A 10-foot-long, six-foot-wide pressurized cylinder with dome-shaped ends, the One-Man Space Station was meant to be launched stacked between a single-seat Mercury on top and an Agena-B upper stage below. The assemblage would be launched atop an Atlas-D rocket similar to that tapped to launch standard Mercury-only orbital missions.

The Atlas-Agena rocket was an early workhorse of lunar and planetary exploration. This image shows the launch of the Mariner 1 Venus probe on 22 July 1962. Less than five minutes later, the Atlas first stage veered off course. The range safety officer transmitted a self-destruct command and the Atlas, Agena upper stage, and Mariner 1 were destroyed. Image credit: NASA.

One might be excused for calling the One-Man Space Station a mission module that enhanced Mercury spacecraft capabilities rather than a bona fide space station. It was meant to be occupied for just 14 days by the single astronaut launched with it in the Mercury spacecraft, then permanently abandoned when the astronaut separated from it in the Mercury to return to Earth.

The group of NASA engineers that heard McDonnell's presentation shared some traits with the proposed One-Man Space Station: it was small and meant to be only temporary. The STG was founded on 5 November 1958, a little more than a month after NASA opened for business. Based at NASA's Langley Research Center in Hampton, Virginia, the STG's aim was to carry out Project Mercury, the U.S. effort to launch a man into space ahead of the Soviet Union.

Though President Dwight Eisenhower took a dim view of what he saw as "space stunts" — for example, launching men into space — he became, along with Senate Majority Leader Lyndon Baines Johnson, one of NASA's chief architects. Eisenhower made no commitment to piloted spaceflight after Mercury. He insisted that Mercury be conducted as a civilian program to keep it separate from the serious military business of developing battlefield and intercontinental missiles and launching reconnaissance and early-warning satellites.

Atlas-D - a modified intercontinental ballistic missile - was not by itself powerful enough to place the Mercury/One-Man Station/Agena-B combination into Earth orbit. McDonnell proposed that the General Dynamics-built Agena-B ignite after the Atlas-D exhausted its propellants and separated. The Agena-B would then insert itself, the Mercury, and the One-Man Space Station into a 150-nautical-mile-high orbit inclined 30° relative to Earth's equator. The Agena-B would remain attached after orbit insertion: it was restartable and would retain enough propellants to maneuver in Earth orbit.

It is probable that the One-Man Space Station was the civilian version of a proposed piloted spy satellite. With its integral Agena-B stage for Earth-orbit injection and orbital maneuvers and its separable Mercury spacecraft for Earth return, McDonnell's station outwardly resembled the Discoverer automated satellites, the first of which was launched in January 1959. "Discoverer" was a cover name for the Corona spy satellite series. Atlas-launched Discoverer/Corona satellites employed an integral Agena for Earth-orbit injection and orbital maneuvers and a reentry capsule for exposed film return. An aircraft would capture the capsule as it descended on a parachute.

A piloted spy satellite must have seemed attractive by the summer of 1960, for the Discoverer/Corona program had suffered failure after failure. Not until Discoverer 14 — launched on 18 August 1960, just six days before McDonnell's presentation to the STG — did the program succeed in returning to Earth a capsule containing exposed film showing Earth-surface targets.

The One-Man Space Station's hull would encompass a total of 282 cubic feet of pressurized volume, of which 182 cubic feet would constitute living and working space. The astronaut would work inside the station in shirt-sleeves, not a pressure suit. A "laboratory test payload" — a suite of experiments which could be changed from flight to flight — would take up 40 cubic feet of the interior volume, while support equipment — for example, fuel cells capable of producing up to 1500 watts of electricity — would take up 60 cubic feet at the domed bottom end of the station.

Schematic of the "Tunnel Access" One-Man Station design with a human figure for scale. A = Mercury spacecraft; B = adapters for linking (from top to bottom) the Mercury spacecraft and the One-Man Space Station, the One-Man Space Station and the Agena stage, and the Agena stage and the top of the Atlas booster; C = inflatable tunnel linking the Mercury hatch with a similar hatch on the One-Man Space Station; D = pressurized work area; E = life support and electricity-generating equipment; F = One-Man Space Station laboratory test payload; G = Agena-B stage; H = Tunnel Access cover in launch position; I = Tunnel Access cover in deployed position; J = top of the Atlas-D rocket. Image credit: McDonnell Aircraft/DSFPortree.

McDonnell proposed two possible designs for its One-Man Space Station. The method the astronaut would use to move between the attached Mercury spacecraft and the One-Man Space Station pressurized volume would distinguish the two designs. McDonnell dubbed them "Tunnel Access" and "Hinged Lab."

Tunnel Access would need fewer Mercury spacecraft modifications than Hinged Lab. An inflatable fabric tunnel would reach Earth orbit folded against the Mercury and One-Man Space Station under a streamlined metal cover. Upon reaching orbit, the astronaut would inflate the tunnel to create a passage between the standard-design 24-inch Mercury side hatch and a 24-inch hatch on the Station's side. The metal cover would remain attached to the tunnel to stiffen it and partly shield it from meteoroid punctures.

When time came to return to Earth, the astronaut on board the Tunnel Access Station would don his protective pressure suit, return to his cramped seat in the Mercury spacecraft, seal the Mercury hatch, and fire pyrotechnic bolts or cord to sever the inflatable tunnel. He would then separate his Mercury spacecraft from an adapter linking it to the Station, turn it so that its broad aft end faced in its direction of motion, and ignite a single solid-propellant retrograde motor to begin atmosphere reentry.

The Hinged Lab design would see the Mercury spacecraft swing on a hinge so that a modified Mercury side hatch could link up with a hatch on the side of the One-Man Space Station. When time came to return to Earth, the astronaut would seal the Mercury hatch, then swing his spacecraft back to its Earth launch position on top of the Station. He would fire explosive bolts to separate the Mercury from the hinged adapter, then would begin reentry.

"Hinged Lab" One-Man Space Station. A = hinge; B = ring-shaped adapter; C = transfer tunnel linking modified Mercury spacecraft hatch with One-Man Space Station hatch. Image credit: McDonnell Aircraft/DSFPortree.

The presence of the Agena-B stage permitted McDonnell to delete the standard Mercury 24-pound solid-propellant posigrade motor set, which in Mercury-only flights would ignite to propel the spacecraft away from its spent Redstone or Atlas booster. Other modifications would include the aforementioned revised hatch designs, which would add 16 pounds to both the Tunnel Access and Hinged Lab One-Man Space Station designs; deletion of the astronaut-monitoring camera from the standard Mercury telemetry & recording system (a savings of 28 pounds); storage space in the Mercury spacecraft cabin for returning to Earth 28 pounds of experiment results generated on board the Station; and addition of seven pounds of water to the Mercury environmental control system.

A new-design adapter would link the broad base of the Mercury spacecraft with the top of the One-Man Space Station. This would weigh 97 pounds for the Tunnel Access design, which could get by with a relatively simple adapter, and 129 pounds for the more complex Hinged Lab adapter.

The Tunnel Access One-Man Space Station without Mercury and Agena-B would weigh 3344 pounds; for the Hinged Lab Station, the weight total was 3309 pounds. The Hinged Lab Station would include an additional 22 pounds of attitude-control propellant — necessary because of the difficulty of stabilizing the out-of-balance side-mounted Mercury configuration. The Tunnel Access Station, for its part, would add 50 pounds for the inflatable tunnel cover and 135 pounds for the tunnel itself.

McDonnell told the STG that the Atlas-D/Agena-B combination could inject 6076 pounds into the One-Man Space Station's planned orbit. Subtracting the combined weight of the modified Mercury, Agena-B, and Station left 1234 pounds for experiment equipment on the Tunnel Access Station and 1342 pounds on the Hinged Lab Station. The company listed as possible One-Man Space Station research projects the study of human adaptation to 14-day weightless missions; monitoring of "long-time equipment performance" on board spacecraft; "lunar probe navigation equipment" testing; radiation, geophysical, and astrophysical measurements; and, by using the Agena-B rocket motor, development of orbital rendezvous techniques.

McDonnell suggested that One-Man Space Stations might also be devoted to single-purpose missions: for example, one might be equipped to carry out communications research, the next might serve as an astronomical observatory, and yet another might enable detailed observations of Earth's weather. The company also suggested that a One-Man Space Station might revert to its likely original purpose: that is, high-resolution imaging of objects on Earth's surface.

Sources

One Man Space Station, McDonnell Aircraft, 24 August 1960.

NASA's Origins and the Dawn of the Space Age, Monographs in Aerospace History #10, David S. F. Portree, NASA History Office, September 1998.

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George Landwehr von Pragenau's Quest for a Stronger, Safer Space Shuttle

The Space Shuttle Challenger and its booster system moments before they were destroyed. The plume of flame emerging from the side of its malfunctioning SRB is clearly visible. Image credit: NASA.

The Space Shuttle Orbiter Challenger was minding its own business on 28 January 1986, working hard to get its seven-member crew and its large satellite payload to low-Earth orbit, when its booster stack betrayed it and everything began to go badly wrong. First, hot gas within its right Solid Rocket Booster (SRB) began to burn through a seal meant to contain it. Soon, a fiery plume gushed from the side of the SRB, robbing it of thrust, and reached out menacingly toward the side of the brown External Tank (ET) and the strut linking the lower end of the SRB to the ET (image at top of post). The plume broke though the ET's foam insulation and aluminum skin, then the strut pulled free of the weakened ET.

Challenger fought back as the ET began to leak liquid hydrogen fuel. It swiveled (the aerospace term is "gimballed") the three Space Shuttle Main Engines (SSMEs) in its tail as it struggled to stay on course. The plume from the SRB, meanwhile, glowed brighter as it began to burn hydrogen leaking from the ET. At the same time, the SRB began to rotate around the single strut left holding it to the ET. That strut was located not far from the Orbiter's gray nose, near the conical top of the errant SRB.

Throughout these events, Challenger's last crew remained oblivious to the technological drama taking place around them. This was just as well, since they had no way to escape what was about to happen to them.

When Challenger at last lost its struggle against its own booster stack, significant events were separated by tenths or hundredths of seconds. Immediately after the right SRB's lower strut came free, the entire Shuttle stack lurched right. Mike Smith, in Challenger's pilot seat, had time for a startled "Uh-oh" less than a second after the lurch. The ET's dome-shaped bottom then fell away, freeing all the hydrogen fuel it contained. The right SRB's pointed nose slammed into and crushed the top of the ET, freeing liquid oxygen oxidizer. The escaped hydrogen blossomed into a fireball that encompassed Orbiter, rapidly disintegrating ET, and SRBs.

Yet the Orbiter Challenger did not explode. Instead, it broke free of what was left of the ET and began a tumble. The aerodynamic pressures the Orbiter experienced as its nose pointed away from its direction of flight were more than sufficient to snap it into several large pieces: the crew cabin, the satellite payload, the wings, and the SSME cluster emerged from the fireball more or less intact. The SRBs, still firing, flew out of the fireball, tracing random trails across the blue Florida sky until a range safety officer commanded them to self-destruct. The Orbiter's wreckage, meanwhile, plummeted into the Atlantic within sight of the Florida coast.

NASA recovered the bodies of the crew and portions of the wreckage, including the section of the right SRB that had leaked hot gas. The wreckage was turned over to accident investigators.

This 1975 NASA illustration depicts the basic components of the Space Shuttle system. The Orbiter includes three Space Shuttle Main Engines (left). Two Solid Rocket Boosters, one of which is mostly hidden behind the External Tank, provide thrust during liftoff and the early part of ascent. The tank includes (from right to left) a small tank for dense liquid oxygen, a drum-shaped structural support ring/tank separator below the Orbiter's nose, and a large tank for low-density liquid hydrogen.

During a Shuttle launch, the three SSMEs ignited first. This caused the twin SRBs, the bases of which were mounted to the launch pad by explosive bolts, to flex along their entire length away from the SSMEs, then straighten out again just as they ignited. O-ring seals between the cylindrical segments making up the SRBs often became unseated during flexure, then had to reseat to contain hot gases after SRB ignition. Accident investigators concluded that failure of one of those seals doomed Challenger. Even more damning, they found that partial seal failures followed by hot exhaust leaks had occurred on pre-Challenger flights — and had been disregarded by NASA managers.

After Challenger, NASA and its contractors redesigned the SRB joints and seals, added crew pressure suits and a limited crew escape capability, and banned potentially unsafe practices and payloads from Shuttle missions. Yet the U.S. civilian space agency might have gone much farther when it sought to enhance Space Shuttle safety after Challenger.

Even before the accident, NASA had at its disposal redesign proposals that could have made the Shuttle stack stronger and safer. In 1982, for example, George Landwehr von Pragenau, a veteran engineer at NASA's Marshall Space Flight Center, filed a patent application — granted in 1984 — for a Shuttle stack design that would have made the Challenger accident impossible.

Born and educated in Austria, von Pragenau joined the von Braun rocket team in Huntsville, Alabama, in 1957. He became a U.S. citizen in 1963. He specialized in rocket stability and flight effects on rocket behavior. He had, for example, been part of the team that found the cause of the "pogo" oscillations that crippled Apollo 6, the second unmanned Saturn V-launched Apollo test mission (4 April 1968).

In the conventional Shuttle stack, von Pragenau explained, SRB thrust was transmitted through the forward SRB attachment points to a reinforced intertank ring between the ET's top-mounted liquid oxygen tank and its liquid hydrogen tank.  He considered this "indirect routing" of thrust loads to be perilously complex. SSME thrust loads, for their part, passed through the Orbiter to its twin aft ET attachment points on the large, fragile liquid hydrogen tank.

By the time he filed his 1982 patent application, von Pragenau had spent almost a decade thinking about how the Shuttle stack might be rearranged to reduce weight and aerodynamic drag, increase stability, simplify thrust paths, and provide greater structural strength. His 1984 patent was, in fact, not his first aimed at Shuttle improvement.

Von Pragenau's 1974 alternative Shuttle stack. Image credit: U.S. Patent Office.

In 1974, von Pragenau had filed a patent — granted the following year — in which he proposed a more slender, more vertically oriented Shuttle stack; that is, one that would mimic conventional rocket designs in which stages are stacked one atop the other. He linked the twin SRBs side by side. Moving the tank for dense liquid oxygen from the ET's nose to its tail placed its concentrated mass nearer the base of the stack, improving in-flight stability. He then mounted the SRBs to the Orbiter's belly and perched the ET atop the SRB/Orbiter combination. SRB and SSME thrust loads were conveyed through struts to meet at the ET's flat, reinforced base.

Von Pragenau's 1982 Shuttle stack design was in some ways a less radical departure from the existing Shuttle design than was his 1974 design. He left the SRBs, ET, and Orbiter in their normal positions relative to each other, but made other significant changes. As in his 1975 patent, he moved the liquid oxygen tank from the ET's nose to its tail and brought the SRBs closer together to improve stability. The liquid oxygen tank became skinny, cylindrical, and almost as long as the Orbiter and SRBs attached to it. The liquid hydrogen tank, fat with low-density fuel, von Pragenau mounted atop the oxygen tank, partially overhanging the Orbiter and SRBs.

Von Pragenau's 1982 Shuttle stack redesign. The numeral "15" points to the rigid thrust structure framework. "34," "35," "36" are Solid Rocket Booster attachment fixtures. These would link to slide rails ("31" and "32") that would run the length of the liquid oxygen tank ("20"). "19" is the liquid hydrogen tank. Image credit: U.S. Patent Office. 

Von Pragenau could not tolerate flexing SRBs. He proposed to mount a slide rail on either side of the liquid oxygen tank. Three attachment fixtures on each SRB would link to the slide rails, helping to ensure rigidity. When the SRBs depleted their propellant, pyrotechnic bolts would fire, freeing them to slide backwards down the rails and fall neatly away from the Orbiter/ET stack.

The most important feature of von Pragenau's redesign was a rigid framework – a thrust structure – that would link the bottom of the SRBs just above their rocket nozzles. In addition to holding the SRBs rigidly in place, the thrust structure would transmit SRB thrust loads to the bottom of the ET oxygen tank, which would rest atop the center of the thrust structure. When the spent SRBs slid away from the Orbiter/ET stack, they would take the thrust structure with them.

Side view of Von Pragenau's 1982 Shuttle stack concept. Image credit: U.S. Patent Office.

Von Pragenau's concepts apparently exerted little influence on NASA's post-Challenger recovery effort. A likely explanation is that neither of his proposals — if they were known to decision-makers at all — was deemed affordable. In addition to extensive changes in manufacturing tooling, both proposals would have required modifications to the Vehicle Assembly Building, the twin Complex 39 Shuttle pads at Kennedy Space Center (KSC), and even the barge that delivers ETs to KSC. Instead of beefing up the existing Shuttle, NASA studied designs for new shuttles which, for lack of funding, remained firmly in the low-cost realm of CAD drawings, conference papers, and conceptual artwork.

On 1 February 2003, the Space Shuttle claimed another crew. The oldest Orbiter, Columbia, was heavier than her sisters Atlantis, Discovery, and Endeavour, which limited the amount of cargo she could deliver to the International Space Station (ISS). For this reason, NASA largely relegated to Columbia the few remaining non-ISS missions — for example, Hubble Space Telescope servicing.

As they began Earth-atmosphere reentry at 8:44 a.m. Eastern Standard Time after a nearly 16-day life sciences mission, the seven STS-107 astronauts on board Columbia were unaware that, during ascent, a piece of ice-impregnated insulating foam nearly a meter wide had broken free from the ET and impacted their spacecraft's left wing. Ice and foam had broken free from ETs before, but the damage they caused was, after cursory examination, deemed acceptable by Shuttle Program managers. This time, however, the impact opened a hole up to 10 inches wide in the Orbiter's left wing leading edge.

Hot plasma generated during reentry entered the hole and began to destroy Columbia's left wing from the inside out. Observers along the Orbiter's flight path, which cut across the southern tier of U.S. states, reported unusual flashes. Meanwhile, members of the STS-107 crew on Columbia's Flight Deck observed and recorded on video flashes visible outside their windows. In the recovered video, the astronauts appear to realize that the flashes were unusual but show no signs of panic.

Much as Challenger had before it, Columbia fought bravely against the forces destroying it. Onboard computers took account of increased drag on the left side of the Orbiter and sought to compensate to keep it on the flight path. At 8:59 a.m. Eastern Standard Time, however, Columbia tumbled and disintegrated over northeast Texas.

Both of von Pragenau's design concepts placed all or part of the ET above the Orbiter, so one might argue that they would not have prevented a failure resembling that which killed the STS-107 crew. On the other hand, one can be forgiven for speculating that a U.S. civilian space agency provided with the means after Challenger to rebuild the Shuttle system to make it safer might also have evolved an organizational culture more prone to investigating and less prone to tolerating recurring flight anomalies.

Von Pragenau retired from NASA in 1991 after more than 30 years of service. He remained involved in engineering efforts at NASA Marshall Space Flight Center during his retirement. He died two years after the Space Shuttle's final flight (STS-135, 8-24 July 2011), on 11 July 2013, at the age of 86.

Sources

Patent No. 4,452,412, Space Shuttle with Rail System and Aft Thrust Structure Securing Solid Rocket Boosters to External Tank, George L. von Pragenau, NASA Marshall Space Flight Center, 15 September 1982 (filed), 5 June 1984 (granted).

Patent No. 3,866,863, Space Vehicle, George L. von Pragenau, NASA Marshall Space Flight Center, 21 March 1974 (filed), 18 February 1975 (granted).

Hampton Cove Funeral Home Obituaries: George Landwehr von Pragenau (http://www.hamptoncovefuneralhome.com/fh/obituaries/obituary.cfm?o_id=2150841&fh_id=13813 — accessed 27 October 2016).

NASA History: Columbia Accident Investigation Board (http://history.nasa.gov/columbia/CAIB.html — accessed 29 October 2016).

NASA History: Challenger STS 51-L Accident (https://www.hq.nasa.gov/office/pao/History/sts51l.html — accessed 29 October 2016).

More Information

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Talking to the Farside: A 1963 Proposal to Use the Apollo Saturn V S-IVB Stage as a Radio Relay

The Moon's Farside hemisphere. Image credit: NASA.

A Saturn S-IVB stage awaits shipment from the Douglas Aircraft plant in California. Various red protective covers would be removed before flight. Image credit: NASA.

The S-IVB rocket stage played several important roles in NASA's 1960s and 1970s piloted space programs. The 58.4-foot-long, 21.7-foot-wide stage, which comprised a single restartable J-2 rocket engine, a forward liquid hydrogen tank, and an aft liquid oxygen tank, served as the second stage of the two-stage Apollo Saturn IB rocket and the third stage of the three-stage Apollo Saturn V.

The Saturn IB S-IVB's J-2 engine would ignite at an altitude of about 42 miles and burn until it placed a roughly 23-ton payload into low-Earth orbit. After that, it would shut down and the spent stage would separate. The Saturn V S-IVB's J-2, on the other hand, would ignite twice to accelerate the stage and its payload: once for 2.5 minutes at an altitude of about 109 miles and again for six minutes about two and a half hours later.

The first burn would place the S-IVB and payload into a low parking orbit between 93 and 120 miles above the Earth; the second would place the S-IVB and payload onto a path that would intersect the Moon, about 238,000 miles away, about three days after Earth launch. Departure for the Moon was called Translunar Injection (TLI).

During Apollo lunar landing missions, the payload was a three-man Command and Service Module (CSM) and a Lunar Module (LM) Moon lander. The astronauts would separate the CSM from the four-segment shroud linking it to the S-IVB about 40 minutes after TLI. They would then maneuver clear of the S-IVB and turn their spacecraft end-for-end so that its nose pointed back at the top of the stage.

The shroud segments, meanwhile, would hinge back and separate to reveal the LM spacecraft mounted atop the S-IVB. The crew would guide the CSM to a docking with the LM; then, about 50 minutes after docking, the joined CSM and LM would move away from the S-IVB. The stage would then vent residual propellants and ignite auxiliary rocket motors to place itself on a course away from the CSM-LM combination.

Schematic representation of Apollo 8 mission events (not to scale). Apollo 8 was the first mission to inject the Saturn V S-IVB stage into orbit around the Sun. Image credit: NASA.

Roughly 60 hours after launch from Earth, the docked CSM and LM would enter the Moon's gravitational sphere of influence. About 12 hours later, they would pass behind the Moon over the Farside, the lunar hemisphere turned always away from Earth. There, out of visual, radar, and radio contact with Earth, the astronauts would ignite the CSM's Service Propulsion System (SPS) main engine to slow the CSM and LM so that the Moon's gravity could capture them into lunar orbit. This critical maneuver was called Lunar Orbit Insertion (LOI). Orbital mechanics dictated that LOI should occur more or less over the center of the Farside.

A few hours later, two astronauts would separate from the CSM in the LM. They would fire the Moon lander's throttleable descent stage engine — again over farside, as dictated by orbital mechanics — to begin their descent toward their pre-selected landing site on the Nearside, the lunar hemisphere that is turned always toward Earth. Following a safe landing and a surface stay (about one Earth day for the earliest Apollo landing missions), the LM ascent stage would lift off.

About two hours later — again over the Moon's hidden hemisphere — the CSM would rendezvous and dock with the LM. The lunar landing crew would rejoin the CSM pilot, the astronauts would cast off the LM ascent stage, and preparations would begin to ignite the SPS to depart lunar orbit for Earth. The critical lunar-orbit departure maneuver, also carried out over farside, was called Trans-Earth Injection (TEI).

The S-IVB stage would, meanwhile, swing past the Moon and enter orbit around the Sun. Although it would travel to the Moon and beyond, as of early 1963 no one had identified any further role for the S-IVB after the CSM and LM separated from it.

The silhouette at left shows the position of the S-IVB third stage in the Saturn V stack. The cutaway illustration (right) shows the interstage fairing that linked the S-IVB to the Saturn V S-II second stage and the relative sizes of the liquid oxygen and liquid hydrogen propellant tanks. Helium stored in spherical tanks push propellants into the J-2 engine. Image credit: NASA.

For six months in 1963, engineers at The Bissett-Berman Corporation in Santa Monica, California, working on contract to NASA Headquarters, studied another use for the Apollo-Saturn V S-IVB stage. In a series of "Apollo Notes" prepared beginning in March of that year, they identified a need for a relay satellite to enable Earth-based radar tracking of the Apollo CSM and LM while they carried out crucial maneuvers over the Farside. They then proposed that the spent S-IVB be outfitted to serve as a relay.

The first note, authored by H. Epstein and based on a concept suggested by L. Lustick, proposed a radar relay satellite for tracking the Apollo CSM during LOI and CSM rendezvous and docking with the LM ascent stage. Epstein and Lustick's satellite would include an omnidirectional antenna for near-lunar operations and, for "deeper phase operation," a steerable four-foot parabolic dish antenna.

The relay satellite, Epstein wrote, would separate from the S-IVB stage along with the Apollo LM and CSM after TEI, then separate from the CSM-LM combination before LOI. It would fly past the Moon on a path that would keep both Earth and most of the Farside in view during LOI and CSM-LM rendezvous and docking. The omni antenna would relay radar from Earth until the satellite was 40,000 kilometers beyond the Moon, then the dish would take over.

The second Bissett-Berman Apollo Note, dated 16 April 1963, suggested that a "special purpose relay package" be placed on the S-IVB stage. The package would either remain attached to the stage or would eject from it when activated. The Apollo Note's author, L. Lustick, attributed the S-IVB relay concept to one Dr. Yarymovych, whose organizational affiliation was not stated.

For his analysis, Lustick assumed that the S-IVB would retain enough propellants for its J-2 engine to restart a third time shortly after CSM-LM separation, raising its speed by 160 feet per second. He calculated that, at the time of CSM-LM LOI, the S-IVB or ejected relay package would have in view simultaneously both Earth and more than three-quarters of the Farside hemisphere.

At the time of CSM docking with the LM ascent stage, about 100 hours after Earth launch, the relay would have in view Earth and a little more than two-thirds of the Farside. Throughout the approximately 28-hour period between LOI and CSM rendezvous with the LM ascent stage, the S-IVB or ejected relay package would remain within 143,000 miles of the Moon.

The S-IVB would rely for attitude control guidance on the ring-shaped Instrument Unit (IU), the Saturn V's "electronic brain." The IU, located on top of the S-IVB during launch, encircled the LM descent stage and provided attachment points for the four separable shroud segments. It was not intended to operate for more than a few hours, so would need modifications to ensure that it could reliably stabilize the S-IVB throughout the relay period.

The ring-shaped Instrument Unit (IU) rode atop the S-IVB stage on both Saturn IB and Saturn V rockets. Image credit: NASA.

The Instrument Unit assembly line at the IBM plant in Huntsville, Alabama. Image credit: NASA.

In an 18 April addendum to Lustick's 16 April Apollo Note, engineer H. Epstein looked at simplifying the S-IVB Farside Relay concept by assuming that the stage would lack attitude control while it acted as a data relay. Replacing steerable dish antennas — one for Earth-S-IVB communication and one for S-IVB-Apollo CSM communication — with two passive omnidirectional antennas would permit data relay no matter how the S-IVB stage became oriented, he wrote.

The use of relatively low-power omni antennas would produce few problems as far as Earth-S-IVB communication was concerned, for NASA could call into play large antennas on Earth to ensure reception of the weak signal. Epstein proposed increasing from four feet to five feet the planned diameter of the dish antenna on the CSM to enable it to receive data from Earth relayed through the S-IVB-CSM omni antenna. He noted, however, that, even with a larger CSM dish antenna, radio interference from the Sun might stymie the omni antenna relay concept.

An undated Apollo Note by Lustick and C. Siska explored the S-IVB Farside Relay concept in yet greater detail, and included evidence of NASA interest in the scheme: for the first time, the authors cited NASA Headquarters-imposed study requirements. The space agency told Bissett-Berman to assume that the S-IVB could increase its speed by up to 1000 feet per second for up to seven hours after TLI, and that the maximum range between the S-IVB Farside Relay and the CSM should not exceed 40,000 nautical miles throughout the relay period.

NASA, Lustick and Ciska explained, sought to learn whether relay of voice (not only data or radar) would be possible using an S-IVB Farside Relay during the roughly 30-hour period between LOI (a "particularly important" time to have voice relay capability, NASA asserted) and CSM-LM ascent stage rendezvous and docking.

The authors found that boosting the S-IVB's speed by 1000 feet per second 7.6 hours after TLI would place it on a path to relay voice between Earth and farside from 72 hours after Earth launch until 102 hours after Earth launch, at which time the S-IVB would reach NASA's 40,000-nautical-mile operational limit. In fact, they found that the S-IVB would have Farside in view as early as 60 hours after Earth launch (this was of purely academic interest, however, because the Apollo spacecraft would not yet orbit over Farside at that time).

Lustick and Ciska noted also that the S-IVB would pass out of sight behind the Moon as viewed from Earth 102 hours after Earth launch. They added, however, that slight adjustments in S-IVB boost direction would postpone loss of Earth contact with the S-IVB Farside Relay for long enough to ensure that voice communication could continue during CSM rendezvous with the LM ascent stage.

In Bissett-Berman's penultimate examination of the S-IVB Farside Relay concept, author Ciska noted that a 1000-foot-per-second boost could be planned for as early as TLI. This would, however, leave no propellant margin for later correction of S-IVB boost aim errors.

On the other hand, S-IVB attitude control was expected to "drift" over time, making accurate boost pointing later than TLI increasingly unlikely. Furthermore, boil-off of liquid hydrogen from the S-IVB stage would rapidly reduce the amount available to fuel a later boost. Both of these factors favored an "all-or-nothing" early boost.

Ciska noted also that, regardless of the S-IVB boost aim point selected, the stage would pass out of sight behind the Moon as viewed from Earth for roughly half an hour at some point along its curved path during the voice relay period. For a 1000-foot-per-second boost applied 7.6 hours after TLI with an aimpoint slanted 100° relative to a line linking the Earth and Moon, for example, the half-hour occultation would occur about 99 hours after Earth launch.

The last Bissett-Berman Apollo Note devoted to the S-IVB Farside Relay concept, also by Ciska and dated 20 August 1963, was an extension of his earlier note. In it, he examined an S-IVB boost 4.15 hours after TLI and considered further the effects of boost direction.

Ciska did not attempt to plot S-IVB attitude drift or liquid hydrogen boil-off rates; nevertheless, he called realistic a 700-foot-per-second boost 4.15 hours after TLI with an aim point slanted 100° relative to the Earth-Moon line. Following the maneuver, the S-IVB Farside Relay would pass out of view of Earth for about 30 minutes a little more than 83 hours after Earth launch and would pass beyond NASA's 40,000-nautical-mile limit about 103 hours after launch.

The S-IVB stage converted into the Skylab Orbital Workshop retained its IU and liquid oxygen tank — the latter launched dry and used as a dumpster — but lost its J-2 engine and saw its liquid hydrogen tank converted into a large habitable volume (note astronaut on lower deck for scale). Image credit: NASA.

Though the Bissett-Berman S-IVB relay proposal was not taken up, S-IVB stages did play key non-propulsive roles in NASA's piloted space program. NASA converted Saturn IB S-IVB 212 into the Skylab 1 Orbital Workshop. Skylab was launched into low-Earth orbit on the last Saturn V to fly and staffed by three three-man crews in 1973-1974. Saturn V S-IVB 515, originally intended to boost the Apollo 20 mission to the Moon, was converted into the Skylab B workshop, but was not launched and became a walk-through display in the National Air and Space Museum in Washington, DC.

Of the 10 Apollo Saturn V S-IVBs that departed low-Earth orbit between 1968 and 1972, half reached orbit about the Sun and half were intentionally crashed into the Moon. The Apollo 8, Apollo 9, Apollo 10, Apollo 11, and Apollo 12 S-IVBs departed the Earth-Moon system, while those that boosted Apollo 13, 14, 15, 16, and 17 out of low-Earth orbit were intentionally impacted on the Moon's Nearside. The impacts were part of a science experiment: the seismic waves their impacts generated registered for hours on seismometers left behind on the lunar surface by earlier Apollo crews, helping to reveal to scientists the structure of the Moon's deep interior.

The irregular ray crater blasted out by the impact of the Apollo 13 S-IVB stage in April 1970. Image credit: NASA.

The Apollo 12 S-IVB, launched on 14 November 1969, flew past the Moon too fast to receive a gravity-assist boost into orbit about the Sun, so circled the Earth in a loosely bound distant orbit until 1971, when, through gravitational perturbations from Earth, Sun, and Moon, it escaped into solar orbit. It orbited the Earth again for about a year in 2002-2003, during which time it was observed and mistakenly identified as a near-Earth asteroid. Spectral analysis revealed the presence of titanium-based paint, however, confirming the object's identity as Apollo 12's errant S-IVB.

Sources

Apollo Note No. 35, Lunar Far Side Relay Technique – Some Basic Radar Considerations, H. Epstein, The Bissett-Berman Corporation, 21 March 1963.

Apollo Note No. 44, Back of Moon Relay Trajectories, L. Lustick, The Bissett-Berman Corporation, 16 April 1963.

Addendum to Apollo Note No. 44, Communications Capability of Unstabilized S-4-B Satellite Relay System, H. Epstein, The Bissett-Berman Corporation, 18 April 1963.

Apollo Note No. 87, Section 7, Far-Side Relay, L. Lustick and C. Ciska, The Bissett-Berman Corporation, no date.

Apollo Note No. 90, Further Examination of Far-Side Relay Trajectories, C. Ciska, The Bissett-Berman Corporation, 6 August 1963.

Apollo Note No. 97, Minimum Boost Velocity Requirement for Far-Side Relay, C. Ciska, The Bissett-Berman Corporation, 20 August 1963.

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