28 March 2017

Things to Do During a Venus-Mars-Venus Piloted Flyby Mission (1968)

One of many contractor proposals for piloted flyby spacecraft put forward in the mid-1960s - this one by Douglas Aircraft Company, c. 1966. The small-diameter section is a modified Apollo Command and Service Module (CSM) spacecraft. Automated Mars probes depart the probe compartment in the large-diameter section. Image credit: Douglas Aircraft Company/San Diego Air & Space Museum (http://sandiegoairandspace.org/)
From 1962 to 1967, NASA and its contractors studied piloted Mars/Venus flybys as a possible interim step between Apollo lunar missions in the 1960s and piloted Mars landing missions in the 1980s. Many of the conceptual flyby spacecraft designs were based on planned or proposed Apollo and Apollo Applications Program technology.

Starting in February 1967, the flyby concept fell into disfavor following criticism by the President's Science Advisory Committee (PSAC). President Lyndon Johnson's PSAC, which had previously supported the piloted flyby concept, declared that piloted flybys made unwise use of astronauts, and that NASA should reassess its plans for using of humans and robots in space. NASA substituted the word "encounter" for "flyby" and continued to task Bellcomm, its Washington, DC-based Apollo planning contractor, with studies of various aspects of piloted flyby missions.

In August 1967, however, Congress eliminated all funds for piloted flyby studies and other advanced mission planning from the Fiscal Year 1968 NASA budget. The lethal AS-204/Apollo 1 fire (27 January 1967) was a key factor in the decision to cut funding designed to give NASA a post-Apollo future. Writing in the aftermath of these cuts, Bellcomm cautioned that its February 1968 report on experiments and observations to be conducted during a 1977 Venus-Mars-Venus encounter mission "should be considered as illustrative of feasibility rather than a plan for the future."

The four-man piloted flyby spacecraft would leave Earth orbit on 23 January 1977. During an Earth-to-Venus transfer spanning mission days one through 148, the spacecraft would pass asteroid 1566 Icarus at a distance of 4.46 million miles (11 May 1977). The astronauts would use the spacecraft's one-meter telescope to measure the asteroid's albedo (reflectivity). At opportune times throughout the mission, they would conduct other astronomical observations, including studies of fluctuations in the radiation from quasars (now known to be the active cores of galaxies), zodiacal light (sunlight reflected off interplanetary dust), faint stars, the planet Mercury, and galaxy redshifts (evidence for an expanding universe).

A piloted flyby spacecraft - this time a 1967 NASA Manned Spacecraft Center design - releases a probe as it flies past the sunlit side of Venus. Visible on the spacecraft are a rectangular radar antenna for probing through the planet's dense clouds; a one-meter optical telescope; a large dish antenna for transmissions to Earth; and a small dish antenna for receiving probe data. Image credit: NASA
On 16 June 1977, the piloted flyby spacecraft would release a 2.88-ton orbiter for relaying to Earth radio signals from the probes it would release during its first Venus flyby. The orbiter would fire rocket motors to slow down so that Venus's gravity could capture it into a 4000-kilometer-high circular orbit.

The piloted flyby spacecraft would zip past Venus for the first time on mission day 149 (21 June 1977), releasing 10 automated probes. These would include four "rough" landers, four bomb-shaped "photo sinker" probes, and two meteorological balloon probes, each containing six balloons with small instrument packages. The automated landers would be designed to survive the planet's heat and pressure for one hour after touchdown, while the sinkers would drop through the thick Venusian atmosphere for about 30 minutes and be destroyed on impact with the surface. The balloon probes would drift among the hot clouds of Venus for one month.

The flyby astronauts, meanwhile, would study Venus using their telescope and a cloud-penetrating radar. Closest approach would occur in sunlight 680 kilometers above the southern hemisphere, at which time the astronauts would fire the flyby spacecraft's rocket motors briefly to help to bend its course toward Mars.

Flight from Venus to Mars would span mission days 150 through 344. The astronauts would measure the albedo of Mars-crossing asteroid 132 Aethra from a distance of 35.9 million miles on 5 December 1977, and would study radio emissions from Jupiter in collaboration with radio astronomers on Earth. The crew would release three 2.36-ton Mars Surface Sample Return (MSSR) landers on 30 December 1977, five days before closest Mars approach.

On 3 January 1978 (mission day 345), the flyby spacecraft would pass 3960 kilometers above the martian night hemisphere at a speed of 5.6 kilometers per second. As they approached the planet, the astronauts would photograph the martian moons Deimos and Phobos.

The MSSR landers would touch down between two and four hours before flyby spacecraft closest approach. Each would deploy a drill to collect a subsurface sample and an aerosol filter to gather airborne dust. Mortars would launch other collection devices at least 100 feet to sample beyond the zone contaminated by the MSSR probe landing rockets. Each lander would then load its samples into a "rendezvous rocket" and launch it to the passing flyby spacecraft. Geophysics and exobiology experiments on the MSSR landers would then radio data to Earth for up to two years.

The Mars-to-Venus leg of the mission would span days 346 through 573. The astronauts would use the flyby spacecraft's biology laboratory to analyze the Mars samples the MSSR landers collected. They would also measure the albedo of three asteroids: 1192 Prisma, in the Main Belt between Mars and Jupiter, at a distance of 49.5 million miles (14 April 1978); 887 Alinda at 11.5 million miles (25 April 1978); and 1566 Icarus (again) at 62.3 million miles (5 August 1978). On 15 August 1978, the flyby spacecraft would release a second Venus radio-relay orbiter.

The flyby spacecraft would pass by Venus for the second time on mission day 574 (20 August 1978), releasing the same types and number of probes as during the first Venus flyby. They would be directed to targets identified using data obtained from the first flyby. Closest approach would occur in darkness over Venus's southern hemisphere at an altitude of 700 kilometers.

The Venus-to-Earth leg would span mission days 575 through 716. The astronauts would reenter Earth's atmosphere with their cargo of samples and data in a modified Apollo Command Module on 9 January 1979.

Sources

"Experiment Payloads for Manned Encounter Missions to Mars and Venus," W. Thompson, et al., Bellcomm, 21 February 1968

The Space Program in the Post-Apollo Period, President's Science Advisory Committee, The White House, February 1967, p. 18

"Science Advisors Urge Balanced Program," Aviation Week & Space Technology, 6 March 1967, p. 135

Humans to Mars: Fifty Years of Mission Planning, 1950-2000, Monographs in Aerospace History #21, NASA-SP-2001-4521, David S. F. Portree, NASA History Division, NASA Headquarters, February 2001, pp. 23-32 - https://history.nasa.gov/monograph21/Chapter%204.pdf (Accessed 28 March 2017)

More Information

EMPIRE Building: Ford Aeronutric's 1962 Plan for Piloted Mars/Venus Flybys

After EMPIRE: Using Apollo Technology to Explore Mars and Venus (1965)

Triple-Flyby: Venus-Mars-Venus Piloted Missions in the Late 1970s/Early 1980s (1967)

25 March 2017

NASA Johnson's Plan to PEP Up Shuttle/Spacelab (1981)

Early artist concept of a Space Shuttle Orbiter with a "Sortie Lab" at the front of its Payload Bay. The Sortie Lab pressurized module is shown as a cutaway illustration. At this point in its history, the Sortie Lab was expected to be manufactured by a U.S. aerospace contractor. The Sortie Lab depicted is dedicated at least partly to astronomy, as evidenced by the large telescope attached to the aft end of its pressurized module. Image credit: NASA
On 29 November 1972, NASA Administrator James Fletcher abolished the Space Station Task Force formed in early 1969 by his predecessor, Thomas Paine, and formed the Sortie Lab Task Force. The "Sortie Lab," a concept that emerged during Phase B Space Station planning in 1970, was envisioned as a pressurized laboratory module which would be carried in the Shuttle Orbiter's Payload Bay.

Fletcher's move acknowledged that the Space Shuttle, conceived originally as a vehicle for transporting crews and cargoes between Earth and an Earth-orbiting Space Station at low cost, would need to become a Space Station - or, at least, an interim space laboratory that could demonstrate that a Space Station would be a desirable new NASA goal after the Space Shuttle became operational.

Strapped for funds and encouraged by President Richard Nixon to use spaceflight as a vehicle for international cooperation, NASA asked the European Space Research Organization (ESRO), a predecessor of the European Space Agency (ESA), to provide the Sortie Lab in exchange for European astronaut flights on board the Shuttle. In August 1973, ESRO and European aerospace contractors agreed to build the Sortie Lab, which became known as Spacelab.

Cutaway illustration of a drum-shaped, ESA-built Spacelab module (center) with a pair of U-shaped Spacelab pallets (left). A bent tunnel with an airlock on top for spacewalks (note space-suited astronaut atop pallet at left) links Spacelab with the Shuttle Orbiter's Mid-Deck, the main living space for the crew. Above that is the Flight Deck, the Orbiter's cockpit. Image credit: NASA
Spacelab would provide scientists with ample pressurized volume in which to conduct research, but it would rely on limited resources - for example, electricity - provided by the Shuttle Orbiter. Orbiter electricity came from a trio of liquid oxygen/liquid hydrogen fuel cells that in early 1981 were expected to generate 21 kilowatts continuously for just seven days. Of this, 14 kilowatts were required for Orbiter systems. The Orbiter could thus supply only seven kilowatts to Spacelab. Of those seven kilowatts, between two and five kilowatts would be needed for basic Spacelab systems, leaving a paltry two to five kilowatts for Spacelab experiments.

In 1978, NASA Johnson Space Center (JSC) in Houston, Texas, launched the Orbital Service Module Systems Analysis Study, which looked into ways that the Space Shuttle Orbiter could be augmented to enable it to better support Spacelab research. An early product of the study was the Power Extension Package (PEP) concept.

Stowed PEP components in the Space Shuttle Orbiter Payload Bay, between the front of a Spacelab module (right) and the rear of the Orbiter crew cabin. Image credit: NASA
The PEP deployed in orbit. PEP displays and controls were meant to be located on the Shuttle Orbiter Flight Deck. Image credit: NASA
The PEP concept was linked with NASA's extensive efforts in cooperation with the U.S. Department of Energy to justify the construction of enormous Earth-orbiting Solar Power Satellites (SPSs). It was portrayed as an experience-building experimental test-bed for SPS technology in the Von Karman Lecture JSC director Christopher Kraft presented to the 15th meeting of the American Institute of Aeronautics and Astronautics in July 1979. The PEP may also have been conceived as a rival for NASA Marshall Space Flight Center's Power Module (see "More Information" below).

The PEP Project Office (PEPPO) at JSC pitched the PEP in a brief report published one month before the first Space Shuttle flight (STS-1, 12-14 April 1981). The PEPPO envisioned the PEP as a "kit" that could be installed easily in the Shuttle Orbiter Payload Bay over the tunnel that would link the Orbiter Mid-Deck with the Spacelab pressurized module.

One hour after launch from Earth, an astronaut on the Orbiter Flight Deck would use the Canada-built Remote Manipulator System (RMS) robot arm to grapple the PEP's Array Deployment Assembly (ADA) and extend it out over the Orbiter's side. The ADA would then unroll a pair of lightweight solar array wings that together would measure more than 100 feet wide. PEP deployment would require about 30 minutes.

The PEP arrays would track the Sun automatically no matter how the Orbiter became oriented, so almost no astronaut intervention would be needed after they were deployed. The RMS and arrays would be sufficiently sturdy to remain deployed during Orbiter attitude-control maneuvers, but the crew would need to stow them before Orbital Maneuvering System burns lest the acceleration cause damage.

The twin arrays would generate a total of 26 kilowatts of electricity. A cable built into the RMS would carry the electricity from the ADA to the PEP's Power Regulation and Control Assembly (PRCA) in the Payload Bay. The PRCA would then distribute it to the Orbiter's electrical system.

The three Orbiter fuel cells would "idle" while the PEP arrays were in sunlight. Each would generate one kilowatt of electricity, bringing the total available on board to 29 kilowatts. Fifteen kilowatts would be available for Spacelab, of which between 10 and 13 kilowatts could be devoted to experiments.

Keeping the Spacelab electricity supply constant throughout each 90-minute orbit of the Earth would require that Orbiter fuel cell output ramp up rapidly from three to 29 kilowatts as the PEP arrays passed into darkness over Earth's night side. To achieve this output, each fuel cell would need to exceed its normal maximum by nearly three kilowatts. The fuel cells would then return to their idle state as the PEP arrays passed again into sunlight. Although it would almost certainly place unusual demands on the Orbiter fuel cells, the PEPPO judged this approach to be "feasible."

The PEPPO estimated that a PEP could extend Shuttle/Spacelab endurance in Earth orbit by four days (that is, to a total of 11 days). If other Orbiter resources (for example, life support consumables) could be augmented, then mission duration might be stretched to 45 days.

The PEPPO explained that it jointly managed PEP solar cell development with NASA's Lewis Research Center. Industry involvement in the PEP project was, it added, already "extensive," with several companies working on small NASA contracts or funding PEP-related work themselves. It estimated that the PEP could power a Spacelab module in Earth orbit as early as 1985 for a total development cost of only $150 million.

Spacelab 1 in Columbia's Payload Bay during STS-9 as viewed from the Flight Deck windows. Cables linking the Orbiter to Spacelab 1 are visible at lower right. Image credit: NASA
The first Spacelab, appropriately designated Spacelab 1, reached orbit in the Payload Bay of the Orbiter Columbia on 28 November 1983, as part of the ninth Shuttle mission. Columbia's crew for mission STS-9 included ESA's Ulf Merbold, the first non-U.S. astronaut to reach space on board a U.S. spacecraft. Merbold was part of a six-man crew that also included Gemini, Apollo, and Shuttle veteran John Young, Skylab 3 veteran Owen Garriott, and spaceflight rookies Brewster Shaw, Robert Parker, and Byron Lichtenberg. Columbia landed at Edwards Air Force Base, California, on 8 December, ending a busy 10-day mission.

Columbia's fuel cells powered Spacelab 1, and all of the 27 Spacelab missions that followed relied on Orbiter fuel cells for their electricity. PEP work had ended in late 1981 as NASA Headquarters took charge of and terminated Shuttle augmentation and Space Station development efforts across the agency. It did this in part to clear the decks as it began formally to seek approval for a Space Station, which it billed as the "next logical step" after the Space Shuttle. President Ronald Reagan called on Congress to approve new-start funding for a Space Station during his annual State of the Union address in January 1984, less than two months after STS-9. 

Sources

Power Extension Package (PEP) Concept Summary, JSC-AT4-81-081, NASA Johnson Space Center, PEP Project Office, March 1981

The Solar Power Satellite Concept, NASA JSC 14898, Christopher C. Kraft; Von Karman Lecture, 15th Annual Meeting of the American Institute of Astronautics and Aeronautics, July 1979

"Spacelab joined diverse scientists and disciplines on 28 Shuttle missions," Science@NASA, 15 March 1999 - https://science.nasa.gov/science-news/science-at-nasa/1999/msad15mar99_1/ (accessed 25 March 2017)

More Information

Electricity from Space: The 1970s DOE/NASA Solar Power Satellite Studies

Evolution vs. Revolution: The 1970s Battle for NASA's Future

23 March 2017

Spring Cleaning

Trust no one. Image credit: unknown
Monday was the first day of spring here in the northern hemisphere. It's the custom in the U.S. - and maybe other places, too - to do a bit of tidying up around the house and yard in springtime.

I've been engaged in the blogging equivalent of spring cleaning since Monday. I hadn't planned on doing this. Over the weekend, however, I discovered I'd made an error in interpretation that propagated across several posts. I had, for reasons passing understanding, come to believe that the Phase B Extension Space Station studies McDonnell and North American Rockwell performed in 1971-1972 began in June 1970. Phase B studies were indeed extended at that time; however, the Phase B Extension studies were something different. They started officially on 1 February 1971 and continued into late 1972.

The Phase B studies looked at single-launch core Station designs and then shifted to include Shuttle-launched modular designs; the Phase B Extension studies studied Shuttle-launched modular designs and shifted to include the "sortie lab" concept, which led to the European-built module we called Spacelab. The transition from one proposed Station concept to the next was not, however, tidy: as John Logsdon notes in his report Space Stations: A Policy History, written for NASA Johnson Space Center, NASA was in September 1970 holding workshops to educate potential users about the potential of the 33-foot-diameter Saturn V-launched core station, preparing a Statement of Work and performing in-house studies in support of the Shuttle-launched modular Station study, and preparing budget recommendations that turned the Space Station Program into a mere advanced program study for the foreseeable future.

I have repaired the damage. Along the way I discovered some other errors. Most were mere typos, but one was a howler. Did I really type that? I think my brain must have wandered off while my fingers performed a modern interpretive dance on my keyboard.

I read through all 104 posts on this blog and made corrections when I found errors. I think my spring cleaning is done now. If, however, any of you notice anything that you suspect is an error, please let me know.

Source

Space Stations: A Policy History, John M. Logsdon, Graduate Program in Science, Technology, and Public Policy, NASA Johnson Space Center, no date (1980), p. II-32

18 March 2017

Lunar GAS (1987)

During the STS-91 (2-12 June 1998) mission to the Russian Mir space station, the Space Shuttle Orbiter Discovery carried four pairs of GAS canisters along its Payload Bay walls. The red arrow points to one pair. Image credit: NASA
NASA's Get Away Special (GAS) Program (officially the Small Self-Contained Payloads Program) was conceived in 1976 as a way of providing researchers with low-cost opportunities to fly experiments in the Space Shuttle Orbiter's 15-foot-by-60-foot payload bay. The first operational GAS canister, with a suite of 10 experiments developed by students at Utah State University, Weber State University, and the University of California at Davis, reached low-Earth orbit (LEO) during mission STS-4 (27 June-4 July 1982) on board the Orbiter Columbia. By 17 March 2005, when NASA terminated the GAS Program in the aftermath of the 1 February 2003 Columbia disaster, nearly 170 GAS canisters had flown in low-Earth orbit (LEO).

If four engineers at the Jet Propulsion Laboratory (JPL) in Pasadena, California, had had their way, a GAS payload might have traveled far beyond LEO. In May 1987, the team proposed that an advanced-design small spacecraft be launched on board a Space Shuttle inside an Extended GAS canister and ejected into Earth orbit. The spacecraft, called Lunar GAS (LGAS), would then use electric-propulsion thrusters to spiral outward to the moon.

Close-up of two of the STS-91 GAS canisters in Discovery's Payload Bay. Image credit: NASA
LGAS anticipated the small, relatively cheap spacecraft of NASA's 1990s Discovery Program, the first mission of which, Near Earth Asteroid Rendezvous (NEAR), departed Earth in 1995. The Discovery Program, a significant break from the large-spacecraft paradigm that characterized much U.S. planetary mission development in the 1970s and 1980s, got its start in 1991-1992 as Defense Department space technology developed for President Ronald Reagan's Strategic Defense Initiative "missile shield" trickled into the civilian space sector. The Discovery Program would become an intermediate evolutionary step leading toward the present-day Cubesat revolution.

The LGAS mission would begin up to three months before planned Space Shuttle launch with the insertion of the 149-kilogram spacecraft into its Extended GAS canister. The spacecraft would at that point enter the routine GAS payload processing flow and no one would see it again until it left its canister in LEO.

The Shuttle Orbiter bearing the LGAS spacecraft would lift off from Kennedy Space Center in Florida and enter an orbit inclined 28.5° relative to Earth's equator. The astronauts would then open its payload bay doors, exposing the closed Extended GAS canister bearing LGAS to space.

NASA required that GAS experiments place minimal demands on Shuttle expendables and astronaut time. The JPL team insisted that, despite its complexity, the LGAS mission could meet this requirement. A few hours after launch, one astronaut would flip a single switch on the Shuttle flight deck to open the motorized Extended GAS canister lid, then would flip two more to release a latch and activate a spring ejection mechanism.

Simplified schematic of the LGAS spacecraft following deployment from its GAS canister. Image credit: JPL/NASA
The barrel-shaped LGAS spacecraft would leave the Extended GAS canister moving at one meter per second; then, as it moved away from the Shuttle Orbiter, it would automatically extend its twin accordion-fold solar-array wings and its science boom. The slender advanced-design rectangular solar arrays would each have a mass of about 15 kilograms. Their combined 7.25 square meters of collecting area would generate 1.467 kilowatts of electricity at mission start.

Two small chemical-propellant thrusters would turn the spacecraft to point its solar arrays and spin axis toward the Sun, then would spin its barrel-shaped body end over end at up to five revolutions per minute to create gyroscopic stability. After it had moved a safe distance away from the Shuttle, the LGAS spacecraft would switch on one of its twin electric thrusters. Mounted on opposite sides of the spacecraft body, these would take turns thrusting parallel to its spin axis. Fueled from a round tank containing 36 kilograms of compressed xenon gas, the thrusters would each be designed to withstand 3500 start/stop cycles and to operate for a total of 4500 hours (187.5 days).

LGAS spacecraft electric-propulsion thrust and coast arcs during escape from Earth orbit. Image: JPL/NASA
The LGAS spacecraft's orbit about the Earth would for mission operations purposes be divided into four 90° arcs, the JPL engineers explained. In the first arc, one thruster would point opposite the LGAS spacecraft's direction of motion so that when it operated it would accelerate the spacecraft. In the second arc, which would occur in Earth's shadow, both thrusters would point perpendicular to the spacecraft's direction of motion; this would mean that they could not contribute to accelerating the spacecraft, so they would not operate.

In the third arc, the second thruster would point opposite the LGAS spacecraft's direction of motion, so it would switch on to take its turn accelerating the spacecraft. In the fourth arc, which would see the spacecraft pass between the Earth and the Sun, the thrusters would again point perpendicular to its direction of motion, so would not operate.

Overcoming drag from Earth's atmosphere would require about one-third of the LGAS spacecraft's thrust early in the departure spiral, the team calculated, but drag would taper off quickly as the spacecraft raised its orbital altitude by up to 20 kilometers per day. Starting about three months after launch from the Shuttle, the LGAS spacecraft would spend between 100 and 150 days inside the Earth-girdling Van Allen Belts. High-energy particles in the Belts would gradually degrade the twin wing arrays, reducing their electricity output.

Image credit: JPL/NASA
About 600 days after launch, the LGAS spacecraft would reach a point about 130,000 kilometers away from the Earth. It would then turn off its thrusters and coast in a lazy 15-day "linking orbit" that would deposit it into a loosely bound 40,000-kilometer circular lunar polar orbit.

The xenon-fueled thrusters would then resume alternating operation with their 90° thrust arcs centered over the moon's polar regions; this time, however, the thrusters would point in the spacecraft’s direction of motion when they operated, gradually slowing the LGAS spacecraft so that it would spiral in toward the moon.

The spacecraft would achieve a 100-kilometer-high, two-hour lunar polar orbit about two years after it departed its Extended GAS canister. In its orbit over the moon's poles, the moon would rotate beneath it about once per month, enabling it to eventually overfly the entire lunar surface. Irregularities in the moon's gravity field would mean that the electric thrusters would need to adjust the spacecraft's orbit about every 60 days.

The LGAS spacecraft would have room for only one science instrument: a 15-kilogram gamma-ray spectrometer (GRS) for charting the composition of the moon's crust. The JPL engineers proposed that the unflown Apollo 18 GRS be mounted on the LGAS science boom. Lunar-orbital science operations would continue for about one year.

Sources

"Lunar Get Away Special (GAS) Spacecraft," AIAA-87-1051, K. T. Nock, G. Aston, R. P. Salazar, and P. M. Stella; paper presented at the 19th AIAA/DGLR/JSASS International Electric Propulsion Conference in Colorado Springs, Colorado, 11-13 May 1987

"Getaway Special," Wikipedia,
https://en.wikipedia.org/wiki/Getaway_Special (accessed 18 March 2017)

More Information

The Eighth Continent

On the Moons of Mighty Jupiter (1970)

Cometary Explorer (1973)

Catching Some Comet Dust: Giotto II (1985)

06 March 2017

A Chronological Presentation: Space Station 1.0

Japanese astronaut Aki Hoshide, a member the International Space Station (ISS) Expedition 32 crew, captures a self-portrait during a 5 September 2012 spacewalk. Reflected in his faceplate are U.S., Japanese, and European components of the ISS silhouetted against the Earth and, above his reflected right hand, NASA astronaut Sunita Williams. The brilliant Sun glaring past Hoshide's shoulder and the camera artifacts it creates make an already fascinating image particularly striking. Image credit: NASA
My blog is only accidentally chronological in arrangement; because of this, occasionally I feel the need to compile a chronological listing of posts on a given topic as an aid to reader understanding. This is one of those times, and the topic this time around is space stations. Enjoy!

One-Man Space Station (August 1960)

Space Station Gemini (December 1962)

Space Station Resupply: The 1963 Plan to Turn the Apollo Spacecraft Into a Space Freighter (November 1963)

"Assuming That Everything Goes Perfectly Well in the Apollo Program. . ." (January 1967)

"A True Gateway": Robert Gilruth's June 1968 Space Station Presentation

McDonnell Douglas Phase B Space Station (June 1970)

From Monolithic to Modular: NASA Establishes a Baseline Configuration for a Shuttle-Launched Space Station (July 1970)

An Alternate Station/Shuttle Evolution: Spirit of '76 (August 1970?)

A Bridge from Skylab to Station/Shuttle: Interim Space Station Program (April 1971)

Skylab-Salyut Space Laboratory (June 1972)

What If a Crew Became Stranded On Board the Skylab Space Station? (October 1972)

Reviving and Reusing Skylab in the Space Shuttle Era: NASA Marshall's November 1977 Pitch to NASA Headquarters

Evolution vs. Revolution: The 1970s Struggle for NASA's Future (1978)

Bridging the Gap Between Space Station and Mars: The IMUSE Strategy (July 1985)

Naming the Space Station (1988)

The 1991 Plan to Turn Space Shuttle Columbia Into a Low-Cost Space Station (July-September 1991)

NASA's 1992 Plan to Land Soyuz Lifeboats in Australia (November 1992)

More Information

A Chronological Presentation: The Apollo-to-Shuttle Transition 1.0