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

The AS-204 Saturn IB launch vehicle — the rocket originally intended to launch Apollo 1, the first piloted Apollo mission in February 1967 — configured to launch Apollo 5, the first unmanned Lunar Module test flight, in January 1968. Image credit: NASA.

Usually in this blog I devote my attention to technical documents and their historical context. I do not normally focus on press conference transcripts. The 26 January 1967 NASA Headquarters press conference led by George Mueller, Associate Administrator for Manned Space Flight, and Charles Mathews, Apollo Applications Program (AAP) Director, is, however, significant enough to be given its own post.

AAP's main stated aim was to gather scientific knowledge in space for the benefit of people on Earth. The program mainly sought to modify Apollo spacecraft and Saturn rockets to do things other than reach for the Moon, but also aimed to enhance NASA's lunar exploration capability. The Command and Service Module (CSM) spacecraft and the two-stage Saturn IB rocket were envisioned as the AAP workhorse vehicles, though the Lunar Module (LM) and the giant Saturn V rocket would also play important roles.

Though Mueller did not say as much, AAP's conceptual roots went back nearly to the Apollo Program's birth. In April 1963, for example, less than two years after President John F. Kennedy made landing a man on the Moon a national priority, NASA's Manned Spacecraft Center (MSC) in Houston, Texas, contracted with CSM spacecraft prime contractor North American Aviation (NAA) to study how the spacecraft might be converted into a six-man transport for Earth-orbital space station crew rotation and logistics resupply.

The AAP press conference followed NASA's Fiscal Year (FY) 1968 budget briefing on 23 January, during which NASA Administrator James Webb and Deputy Administrator Robert Seamans told reporters that President Lyndon Baines Johnson had authorized NASA to seek a total of $454.7 million for AAP in FY 1968. Despite the fact that it had existed for 16 months as a formal program, most reporters present at the budget briefing knew little of AAP, so they prevailed upon the space agency to provide more information. The 26 January press conference was NASA's response.

Among the few space-savvy members of the press corps, the Johnson Administration's evident enthusiasm for AAP piqued interest. The White House had, after all, sought $270 million for AAP in FY 1967, only to see Congress appropriate just $80 million. Leaders in Congress had cited the escalating cost of war in Indochina when they slashed the President's FY 1967 AAP request. That President Johnson would expend political capital on the program for a second year in a row — and ask for almost double the sum he had been refused the previous year — indicated strong Executive Branch support for AAP.

When reporters arrived at NASA Headquarters for the press conference late in the afternoon on 26 January, they found on their seats a 10-page packet of detailed information on AAP. In this post, I have fleshed out some of Mueller's generalizations by referring to the AAP press packet.

Mueller told the assembled reporters that the time was ripe for starting AAP. "By the end of this year," he declared, "we will have flown men on at least two of the Saturn V launch vehicles, and we will have tested both the [LM] and the [CSM]." He did not need to tell the reporters that the first piloted flight of the Apollo Program, designated Apollo 1 or AS-204, was scheduled for launch on 21 February, a little more than three weeks after the AAP press conference. Apollo 1 was planned as a 14-day Earth-orbital test of the Apollo CSM launched on a Saturn IB rocket.

June 1966: Artist concept of Apollo Program launch vehicles and spacecraft. The Saturn V (left) included the S-IC first stage, the S-II second stage, the S-IVB third stage, and the Apollo spacecraft depicted in the center of the illustration. The "Uprated Saturn I" (right) was by January 1967 renamed the Saturn IB, which included the S-IB first stage, the S-IVB second stage, and the Apollo spacecraft. The Saturn V and Saturn IB S-IVB stages were essentially identical. The Command Module and Service Module together formed the Command and Service Module (CSM) spacecraft. The Lunar Module (LM) rode into space inside the tapered Spacecraft LM Adapter (SLA) shroud (not labeled), which could also fly empty or with payloads other than the LM inside. Image credit: NASA.

Mueller reminded his audience that NASA had ordered 12 Saturn IB rockets and 15 Saturn Vs for the Apollo lunar program. He expected that fewer than that would be needed to reach the goal of a man on the Moon before the end of the 1960s decade. It was from the surplus that the two-stage Saturn IB rockets needed for the first AAP missions would be drawn. As soon as the Apollo Program was finished with Earth-orbital test missions launched on Saturn IBs, AAP missions could begin. In fact, Mueller saw no reason why AAP Saturn IB-launched Earth-orbital missions and Apollo Saturn V-launched Moon missions could not occur simultaneously.

"Assuming that everything goes perfectly well in the Apollo Program," Mueller told the reporters, by late 1968 or early 1969 NASA could have in 275-nautical-mile-high Earth orbit "an embryonic space station or the first step toward a space station. . .with the capability of reuse and resupply." The station might operate for more than three years before Earth's thin upper atmosphere dragged it down from orbit.

NASA did not have firm plans for staffing the AAP station throughout its time in orbit, Mueller explained. He declared, however, that the four missions required to establish the planned initial AAP capability constituted "a program that is firm, and is proceeding."

The first of the four "firm" missions, designated AAP-1, would begin with the launch of a Saturn IB rocket with a piloted CSM on top. Upon attaining orbit, the three-man crew would turn their spacecraft end-for-end and dock with a prototype Mapping & Survey System (M & SS) module stored in the Spacecraft LM Adapter (SLA), the segmented, streamlined shroud that during ascent to orbit linked the bottom of the CSM with the top of the Saturn IB's S-IVB second stage. During an independent flight period lasting about a week, the AAP-1 crew would use the M & SS to record data on the oceans, landmasses, and atmosphere for the benefit of people on Earth.

Four or five days after the AAP-1 astronauts began their program of Earth observations, NASA would launch the AAP-2 Saturn IB. The rocket, which would carry no crew, would include an SLA with a conical aerodynamic shroud on top in place of a CSM, so would resemble the one in the image at the top of this post. The SLA and shroud would cover an airlock and a docking adapter with five ports. Charles Mathews, who had headed up MSC's Gemini Program Office before becoming NASA Headquarters AAP Director, added that the airlock would include a Gemini spacecraft hatch for exiting the station to perform spacewalks.

The AAP-2 S-IVB stage would inject itself, the SLA, the airlock, and the docking adapter into its 275-nautical-mile-high operational orbit using its single J-2 engine, then flight controllers would command the spent stage to "passivate" itself. Their command would open vents in the S-IVB stage tanks and engine to exhaust into space all liquid hydrogen fuel and liquid oxygen oxidizer remaining on board. In answer to a reporter's request for more detail, Mueller added that small spherical helium tanks bolted to the lining of the 21-foot-diameter, 10,000-cubic-foot liquid hydrogen tank would also be vented — the inert helium was on board to pressurize the liquid hydrogen tank, pushing propellants into the J-2 engine — and that the stage would automatically "disconnect the various electrical things that might cause a problem."

The S-IVB stage would also deploy electricity-generating solar arrays from two of its four folded-back SLA shroud segments and a meteoroid shield that would stand several inches off the skin of the two-thirds of the S-IVB stage that contained the liquid hydrogen tank. The shield, a thin layer of metal, would break up any micrometeoroids that might hit it, preventing them from penetrating the stage skin and liquid hydrogen tank within.

Artist concept of AAP-2 spent-stage station with AAP-1 Apollo CSM docked at axial port and AAP-1 Mapping & Survey System docked at radial port. Image credit: NASA.

The AAP-1 CSM would rendezvous with the AAP-2 spent-stage station and dock the M & SS with one of the docking adapter's four radial ("side") ports. It would then undock from the M & SS and dock with the docking adapter's axial ("front") docking port.

The AAP-1 astronauts would enter the 65-inch-diameter, 1000-cubic-foot docking module, where would be packed furnishings for outfitting the interior of the liquid hydrogen tank. Before they could deploy the furnishings (a process that would need three or four days), they would use controls in the airlock to close the vents in the liquid hydrogen tank and fill it with a mixture of three-fifths oxygen and two-fifths nitrogen at five pounds per square inch of pressure. Gaseous oxygen and nitrogen for pressurizing the liquid hydrogen tank would reach orbit in tanks bolted to the outside of the airlock module.

Mueller likened putting the furnishings packed in the docking adapter into the liquid hydrogen tank to "building a ship in a bottle." The astronauts would open a 43-inch-diameter hatch leading into the tank. The tank's interior would be modified during manufacture to include tie-downs and attachment points for installation of a galley and hygiene, exercise, sleep, and experiment equipment, as well as lights and ventilation ducts and fans.

Though illustrations he displayed during the press conference showed pre-installed walls and grillwork floors, Mueller told a reporter that "I don't know that we will want to put additional things [besides the tie-downs and attachment points] inside" the liquid hydrogen tank. If the decision were taken to minimize tank modifications, then the astronauts would string fabric floors and walls within the tank, he explained. A "rope" running the length of the tank would aid mobility. He added that he was "sure that we will use liberal amounts of velcro."

Mueller was quick to note that few experiments had been officially manifested for any AAP flight; some of the $454.7 million the White House had requested for AAP in FY 1968 would go toward new experiment development. There were, for example, no biology experiments yet approved, though seven medical experiments were on track for flight. NASA also expected to include Defense Department experiments that would focus on "how to work in space" and test "jet shoes." Mueller likened them to "roller skates with gas jets on them."

He explained that experiment packages scheduled specifically for the AAP-1/AAP-2 mission would, among other things, aim to "find out what happens to the flammability of materials, how they actually burn when you have a combination of oxygen and nitrogen and. . .zero gravity." In addition, the astronauts would continue to use the M & SS for Earth observations, and would test a combination sleep/space suit-donning station.

The AAP-1 crew's stay on board the AAP-2 spent-stage station was scheduled to last for about 28 days, or twice as long as Gemini 7 (4-18 December 1965), which at the time of the 26 January press conference was the world record-holder for piloted space mission duration. As the AAP-1/AAP-2 mission drew to a close, the crew would shut off experiments and station systems and undock in their CSM. They would then ignite the CSM's Service Propulsion System main engine to deorbit, cast off the Service Module (SM), reenter the atmosphere, deploy parachutes, and splash down at sea in the conical Command Module (CM).

Between three and six months later — no later than mid-1969 — NASA would launch the AAP-3 mission to the AAP-2 station. A piloted CSM loaded up with supplies would ride a Saturn IB to orbit. Mueller told his audience that he favored putting supplies in a special module that would ride to orbit in the SLA, much as had the M & SS; however, the illustrations he showed to the press did not depict such a module.

The LM-derived AAP-4 Apollo Telescope Mount maneuvers to a docking at the AAP-2 radial port opposite the AAP-1 Mapping & Survey System while the AAP-3 CSM stands by. Image credit: NASA/David S.F. Portree.

One day after the AAP-3 launch, NASA would launch the unmanned AAP-4 Saturn IB bearing beneath its SLA and conical shroud the Apollo Telescope Mount (ATM). The ATM was envisioned as a modified Apollo LM with solar arrays and solar observatory instruments in place of descent and ascent engines and landing legs.

The AAP-3 CSM would dock with the ATM, withdraw it from the top of the AAP-4 Saturn IB S-IVB stage, and transport it to the AAP-2 station. An astronaut would then board the ATM, undock from the CSM, and, using the ascent stage attitude control thruster quads for propulsion, pilot it to a docking at one of the station's docking module radial ports. The CSM would stand by until ATM docking was successfully completed, then would dock at the station's axial port. The ATM would then deploy solar arrays, which would provide it with electricity.

Mueller explained that the ATM was scheduled for launch in 1969 because the Sun's 11-year cycle of activity would peak in that year. The ATM would, he told the reporters, carry "the most comprehensive array of instruments that has ever been assembled for observing the Sun." An astronaut at the ATM control panels in the modified LM ascent stage would keep a constant vigil on the Sun, and would rapidly direct the instruments toward interesting phenomena as they appeared. The ATM might operate at the end of a tether attached to the docking adapter to minimize the effects on the quality of the data it collected of astronaut movements inside the spent-stage station.

Of course, the chief benefit of the ATM would be scientifically important but essentially abstract knowledge about the structure and behavior of the Sun. AAP was, however, meant to bring benefits of space to people on Earth, so Mueller opined that a better understanding of the Sun would "have marked benefits on our own understanding of how to generate and control energy here on Earth."

The AAP-3 crew would seek to double the AAP-1 crew's stay-time in space, setting a new record for space endurance of 56 days. In addition to operating the ATM, they would continue many of the experiments begun by the AAP-1 astronauts.

Mueller then described AAP payloads, missions, and capabilities that would begin to be developed if Congress voted to provide the funding for AAP that the White House had requested for FY 1968. In answer to a reporter's question, he explained that the AAP-2 spent-stage station would remain at the center of the program's Earth-orbital activity "until something fails," at which time NASA would launch a fresh spent-stage station.

Reusability would be a hallmark of AAP, Mueller explained. The term “reusability” had at least two meanings in the program. On the one hand, it meant that for as long as they could function, the AAP stations would host new crews and instrument payloads. On the other, it meant that certain hardware elements — in particular the Apollo CM — would be redesigned for refurbishment and multiple flights. Both approaches to reusability aimed to cut costs.

Mueller called the Apollo CM "one of the most expensive elements of the space vehicle." He described for reporters an uprated CM for later AAP flights that would touch down on land, not splash down at sea. "Since we don't dunk it in salt water at the end of the flight," he explained, "we don't then have quite the same corrosion problem. . .that we do with those [CM]s that are water landed."

Landing the CM on solid ground would, Mueller noted, also help NASA to double its normal three-person crew complement. Steerable parachutes and view screens would enable the crew to pilot their CM to a predetermined landing zone; then, five or 10 feet above the ground, retro rockets behind the heat shield would ignite, slowing the CM to a touchdown speed of three or four feet per second. Normal Apollo splashdown speed was, Mueller explained, 10 or 20 feet per second; reducing that velocity meant that shock-absorbing struts supporting the CM crew couches would not stroke very much to absorb landing shock, so would not need as much empty space behind them as in the baseline CM. This would enable NAA contractor engineers to install a new row of three couches behind the existing three Apollo CM couches.

Mueller then described three "payload packages" that might be added to AAP stations if funding allowed. AAP-A was a "Meteorology Payload Package" with 14 experiments which would, it was hoped, reach orbit on a Saturn IB in mid-1969. AAP-B, the "Earth Resources Payload Package" with 12 experiments on board, would follow in mid-1970. By then, Mueller told his audience, a three-man crew might live on board an AAP station for an entire year.

The "Manned Photographic Telescope," an ultraviolet telescope with a meter-wide aperture, might be docked to an AAP station in a high-Earth orbit, Mueller explained, in order to permit observation periods longer than were possible in the AAP-2 station's low orbit. A station high above Earth would need more time to complete an orbit, thus potentially permitting continuous observation of an astronomical target over the space of hours. The AAP-2 station, by contrast, would circle Earth in about 90 minutes, enabling less than 45 minutes of observation before the target dropped out of sight below Earth's horizon.

Placing an AAP station in high-Earth orbit would demand a more powerful launcher than the Saturn IB; specifically, the Saturn V. The S-IVB stage that formed the second stage of the Saturn IB served also as the Saturn V third stage, so could be put to use as an AAP spent-stage station in high-Earth orbit with only modest modifications.

1966 NASA artist concept of the baseline Apollo Lunar Module. 

The Manned Photographic Telescope was scheduled for launch in 1971-1972, so there was a good chance that other Saturn V-launched AAP missions might precede it. AAP planners expected that, after a series of Early Apollo lunar landing missions starting around the end of 1968, Saturn V-launched AAP lunar missions would take over. Early Apollo missions would spend up to 36 hours on the lunar surface and support 1000-foot moonwalks; AAP lunar missions might last 14 days and support traverses of up to 15 miles from base camp.

Mueller expected that each AAP lunar mission would need two Saturn Vs; one to launch a CSM/LM Shelter combination and one to launch a CSM/LM Taxi combination. The Shelter, which would land at the candidate landing site without a crew, would house the two astronauts who arrived later in the Taxi.

The LM Taxi would be designed to park on the lunar surface, its major systems shut down, for 14 days, then "wake up" so that the astronauts could lift off in its Ascent Stage to rejoin the CSM Pilot in lunar orbit. Outwardly the Taxi would resemble the Apollo LM.

The LM Shelter, on the other hand, would need many very obvious modifications. Some concepts had all descent systems in the Ascent Stage moved to the Descent Stage and the Ascent Stage replaced entirely with a purpose-built habitat module; others only stripped out ascent systems and propellants and left the Ascent Stage otherwise intact. Regardless of its design, the LM Shelter would require modifications to enable an automated or remote-controlled landing and a long quiescent stay on the Moon ahead of LM Taxi arrival.

The LM Shelter would also carry attached to its sides a heavy load of exploration equipment. This might include a "jeep" for surface mobility, a drill for boring 300-foot-deep holes, an instrumented "subsurface probe" for lowering down the bore hole, an astronaut-carried "survey system" for stereo imaging and precise post-flight location of sampling sites and traverse routes, and an elaborate suite of automated science instruments that would continue to operate long after the AAP lunar mission crew returned to Earth.

The AAP lunar landing missions, which would occur about a year apart, might be preceded by one or more AAP lunar-orbital mapping missions. These would see a CSM with an M & SS docked to its nose operate in lunar polar orbit for at least 14 days. The astronauts on board would map the entire Moon in much greater detail than could the automated Lunar Orbiter series, which was ongoing at the time of the AAP press conference. This would enable improved landing site selection and traverse planning for the AAP lunar missions. The advanced lunar missions would probably rely on Saturn V rockets built specifically for AAP; that is, not part of the original 15-rocket "buy" for the Apollo Moon program.

Both Mueller and the assembled reporters seemed to downplay AAP lunar missions, as if all realized that they were the part of AAP least likely to receive funding from Congress. Though they would yield fascinating data, they ran against the grain of AAP. The people on Earth who would benefit most from the AAP lunar missions were, it seemed, the people hired to build the lunar mission hardware. In general, the reporters assembled for the 26 January press conference looked with suspicion upon aspects of AAP that seemed to them mainly to mean continued pork for certain states and congressional districts.

Interestingly, it was Charles Mathews, former MSC Gemini director, who was most successful in explaining the potential of AAP in NASA's post-Apollo program. He told the reporters that "between Mercury and Apollo. . .we had a program called Gemini, where we learned to do many of the things. . .that we are going to [do] in [AAP] and in the Apollo Program." Mathews argued that AAP could serve the next big NASA program, whatever it might be, as Gemini had served Apollo. "[Before] we go on to planetary operations or space station operations," he said, "we need to develop experience in these long-duration operations. . .So [AAP] is a rather logical approach."

Left to right: Apollo 1 crew members Ed White, Gus Grissom, and Roger Chaffee pose with a model of the Apollo CM. Image credit: NASA.

The 26 January press conference drew to a close at 5:30 pm Eastern time. Twenty-four hours later, at Cape Kennedy, Florida, astronaut Gus Grissom, commander of the Apollo 1 mission, was growing frustrated. He had been strapped on his back inside CSM-012 on the pad at Launch Complex 34 for several hours with his shipmates Roger Chaffee, a spaceflight rookie, and Ed White, the first American to walk in space. Grissom had for at least a year worried that CSM-012 suffered from more than its share of technical faults. The pre-flight test on 27 January encountered one glitch after another.

One problem was "ratty" communications — crackly static and voice dropouts — between flight test control and the spacecraft. Controllers put the test countdown on hold while they tried to correct the problem. Grissom raised his voice above the static to ask, "How are we going to get to the Moon if we can't talk between two or three buildings?"

At 6:31 pm, flight controllers heard the word "fire" spoken over their crackling headsets. A spark, possibly the result of faulty wiring insulation, had set alight materials in the CM cabin that had not been adequately tested for fire resistance in its pure oxygen atmosphere. These included liberal quantities of velcro. Almost before they could react, Grissom and his crew were asphyxiated as flames burned up their air hoses and consumed the oxygen inside their capsule. Heat and pressure built up inside the CM until its pressure hull cracked, spewing acrid smoke into the enclosed service area surrounding the capsule.

The pad crew suffered smoke inhalation and burns as they fought to open the CM's balky, poorly designed inward-opening hatch. They gave no thought, however, to abandoning their efforts to save Grissom, Chaffee, and White.

Through the small hatch window they could see only dense smoke. When they finally succeeded in pushing back the hatch about five minutes after the fire began, the terrible truth was made plain. The United States had suffered the world's first spaceflight fatalities, and they had happened on the launch pad, during what was supposed to be a routine pre-flight practice run, not during flight through space or on the Moon.

NASA and the Congress quickly went to work to investigate the fire. The NASA-appointed AS-204 Review Board displayed commendable impartiality; it found many hardware and procedural faults throughout the Apollo Program and evidence of rocky relations between CSM contractor NAA and NASA's Office of Manned Space Flight spanning years. NASA's allies in Congress became angry because the space agency had not shared with them its concerns regarding NAA workmanship.

NASA officials testify before Congress in the aftermath of the Apollo 1 fire. Left to right: Deputy Administrator Robert Seamans; Administrator James Webb; Associate Administrator for Manned Space Flight George Mueller; and Apollo Program director Samuel Phillips. Image credit: NASA.

Congress could not "punish" NASA by cutting the Apollo budget; to do so would have imperiled achievement of the national goal of a man on the Moon by 1970. It could, however, express its disquiet by attacking AAP. For a time in the summer of 1967, it appeared that AAP's FY 1968 budget might be cut to $300 million, a figure which NASA officials stated would permit a reasonable amount of progress during the year that followed. In the end, however, Congress slashed the FY 1968 AAP budget to only $122 million.

Some expected President Lyndon Baines Johnson to fight for AAP; however, he instead acquiesced to the cuts, declaring that "some hard choices must be made between the necessary and the desirable. . .We dare not eliminate the necessary. Our task is to pare the desirable." It appeared to some that NASA had lost its future.

Appearances could be deceiving, however. In a late November 1967 presentation to the American Astronautical Society's Astronautics International Symposium in New York City — following close on the heels of Apollo 4, the successful first unmanned test of the Saturn V rocket (11 November 1967) — Charles Mathews outlined an AAP program only a little different from the one he and Mueller described the day before the fire. In fact, it included two new missions: AAP-1A, a CSM/M & SS mission without a spent-stage workshop that would take over AAP-1's Earth observations and ease NASA into AAP-1/AAP-2, and AAP-5, which would deliver an unspecified payload package to the first spent-stage station and extend astronaut orbital stay-time past 56 days.

In the new plan, AAP-1 and AAP-2 traded places; that is, the spent-stage workshop would reach space first and be designated AAP-1. Mathews also gave brief mention to two undesignated missions: these would see launch of a piloted CSM plus an unspecified payload package and a second spent-stage AAP station.

It soon became clear that AAP retained high-level support, for in mid-January 1969, the Johnson White House requested $439 million for the program in FY 1969. This was about half the budget NASA had planned for AAP in FY 1969 before the fire, but was deemed sufficient to move forward with the program.

Events on the other side of the world intervened, however. The Tet Offensive, which saw Viet Cong and North Vietnamese forces simultaneously attack U.S. and South Vietnamese bases, was the largest campaign of the Vietnam War. It began on 30 January 1968, on the eve of Tet, the Lunar New Year, and continued through much of February. Tet put U.S. forces on the defensive and dramatically increased the human and financial cost of waging war in Indochina.

AAP had been on shaky ground with Congress even before the Tet escalation. By the time it completed its deliberations, the Legislative Branch cut Johnson's FY 1969 AAP request by nearly half to $277 million. Other cuts in NASA funding caused NASA Administrator James Webb to put Saturn rocket production on hold. AAP entered a kind of limbo: capable of moving forward with near-term development, but with little prospect of accomplishing the more ambitious missions that gave near-term development a purpose.

It is interesting to speculate how AAP might have unfolded had the Apollo 1 fire not occurred. It seems likely that, had NAA delivered a better-quality CSM-012 spacecraft, a successful Apollo 1 mission would have increased (or at least not decreased) support for AAP. The program might then have received adequate funding in FY 1968, permitting it to become better established.

The Tet Offensive would have occurred as it did in our timeline, so Congress would probably not have granted the Johnson Administration's full FY 1969 AAP funding request. Because the program would have become better established during FY 1968, however, the cuts might not have been so deep.

The LM probably would have been delayed, as it was in our timeline, leading perhaps to calls for NASA to focus its energies on Apollo, not AAP. Alternately, a successful Apollo 1 mission in February 1967 followed by a successful Saturn V test might have made the LM delay seem a little less important.

It appears possible that, had no Apollo 1 fire taken place, NASA might have launched an AAP spent-stage station by late 1968. When an astronaut — perhaps Apollo 1 commander Gus Grissom — became the first man to set foot on the Moon late in 1968 or early in 1969, three astronauts on board the AAP station in low-Earth orbit might have gathered around a flickering small monitor to watch the historic event.

Sources

Apollo Applications Briefing, NASA News, NASA Headquarters, 26 January 1967.

Apollo Applications — A Progress Report, Charles Mathews; presentation at the American Astronautical Society Astronautics International Symposium, 27-29 November 1969.

Living and Working in Space: A History of Skylab, NASA SP-4298, W. David Compton and Charles Benson, NASA, 1983.

“White House Stand Blocks NASA Budget Restoration,” Aviation Week & Space Technology, 28 August 1967, p. 32.

More Information

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

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

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

A Forgotten Rocket: The Saturn IB

What Shuttle Should Have Been: NASA's October 1977 Space Shuttle Flight Manifest

Fact and fiction blend at the rollout of the Space Shuttle Orbiter Enterprise. Space agency officials present include NASA Administrator James Fletcher (in gray suit at left speaking with DeForest Kelley) and STS Operations Director Chester Lee (in light brown suit at right between Gene Roddenberry and Walter Koenig). Image credit: NASA.

Soon after President Richard Nixon gave his blessing to the Space Shuttle Program on 5 January 1972, NASA scheduled its first orbital flight for 1977, then for March 1978. By early 1975, the date had slipped to March 1979. Funding shortfalls were to blame, as were the daunting engineering challenges of developing the world's first reusable orbital spaceship based on 1970s technology. The schedule slip was actually worse than NASA let on: as early as 31 January 1975, an internal NASA document (marked "sensitive") gave a "90% probability date" for the first Shuttle launch of December 1979.

In October 1977, Chester Lee, director of Space Transportation System (STS) Operations at NASA Headquarters, distributed the first edition of the STS Flight Assignment Baseline, a launch schedule and payload manifest for the first 16 operational Shuttle missions. The document was in keeping with NASA's stated philosophy that reusable Shuttle Orbiters would fly on-time and often, like a fleet of cargo airplanes. The STS Utilization and Operations Office at NASA's Johnson Space Center (JSC) in Houston had prepared the document, which was meant to be revised quarterly as new customers chose the Space Shuttle as their cheap and reliable ride to space.

The JSC planners assumed that six Orbital Flight Test (OFT) missions would precede the first operational Shuttle flight. The OFT flights would see two-man crews (Commander and Pilot) put Orbiter Vehicle (OV)-102 through its paces in low-Earth orbit. The planners did not include the OFT schedule in their document, but the 30 May 1980 launch date for their first operational Shuttle mission suggests that they based their flight schedule on the March 1979 first OFT launch date.

Image credit: NASA.

Image credit: NASA.

Thirteen of the 16 operational flights would use OV-102 and three would use OV-101. NASA would christen OV-102 Columbia in February 1979, shortly before it rolled out of the Rockwell International plant in Palmdale, California.

As for OV-101, its name was changed from Constitution to Enterprise in mid-1976 at the insistence of Star Trek fans. Enterprise flew in Approach and Landing Test (ALT) flights at Edwards Air Force Base in California beginning on 15 February 1977. ALT flights, which saw the Orbiter carried by and dropped from a modified 747, ended soon after the NASA JSC planners released their document.

The first operational Space Shuttle mission, Flight 7 (30 May-3 June 1980), would see Columbia climb to a 225-nautical-mile (n-mi) orbit inclined 28.5° relative to Earth's equator (unless otherwise stated, all orbits are inclined at 28.5°, the latitude of Kennedy Space Center in Florida). The delta-winged Orbiter would carry a three-person crew in its two-deck crew compartment and the bus-sized Long Duration Exposure Facility (LDEF) in its 15-foot-wide, 60-foot-long payload bay.

Columbia would also carry a "payload of opportunity" - that is, an unspecified payload. The presence of a payload of opportunity meant that the flight had available excess payload weight capacity. Payload mass up would total 27,925 pounds. Payload mass down after the Remote Manipulator System (RMS) arm hoisted LDEF out of Columbia's payload bay and released it into orbit would total 9080 pounds.

A page from the STS Flight Assignment Baseline document of October 1977 shows payloads and other features of the first five operational Space Shuttle missions plus Flight 12/Flight 12 Alternate.  Image: NASA. 

During Flight 8 (1-3 July 1980), Columbia would orbit 160 n mi above the Earth. Three astronauts would release two satellites and their solid-propellant rocket stages: Tracking and Data Relay Satellite-A (TDRS-A) with a two-stage Interim Upper Stage (IUS) and the Satellite Business Systems-A (SBS-A) commercial communications satellite on a Spinning Solid Upper Stage-Delta-class (SSUS-D).

Prior to release, the crew would spin the SBS-A satellite about its long axis on a turntable to create gyroscopic stability and raise TDRS-A on a tilt-table. After release, their respective solid-propellant stages would propel them to their assigned slots in geostationary orbit (GEO), 19,323 n mi above the equator. Payload mass up would total 51,243 pounds; mass down, 8912 pounds, most of which would comprise reusable restraint and deployment hardware for the satellites.

The TDRS system, which would include three operational satellites and an orbiting spare, was meant to trim costs and improve communications coverage by replacing most of the ground-based Manned Space Flight Network (MSFN). Previous U.S. piloted missions had relied on MSFN ground stations to relay communications to and from the Mission Control Center (MCC) in Houston. Because spacecraft in low-Earth orbit could remain in range of a given ground station for only a few minutes at a time, astronauts were frequently out of contact with the MCC.

On Flight 9 (1-6 August 1980), Columbia would climb to a 160-n-mi orbit. Three astronauts would deploy GOES-D, a National Oceanic and Atmospheric Administration (NOAA) weather satellite, and Anik-C/1, a Canadian communications satellite. Before release, the crew would raise the NOAA satellite and its SSUS-Atlas-class (SSUS-A) rocket stage on the tilt-table and spin up the Anik-C/1-SSUS-D combination on the turntable. In addition to the two named satellites, NASA JSC planners reckoned that Columbia could carry a 14,000-pound payload of opportunity. Payload mass up would total 36,017 pounds; mass down, 21,116 pounds.

Following Flight 9, NASA would withdraw Columbia from service for 12 weeks to permit conversion from OFT configuration to operational configuration. The JSC planners explained that the conversion would be deferred until after Flight 9 to ensure an on-time first operational flight and to save time by combining it with Columbia's preparations for the first Spacelab mission on Flight 11. The switch from OFT to operational configuration would entail removal of Development Flight Instrumentation (sensors for monitoring Orbiter systems and performance); replacement of Commander and Pilot ejection seats on the crew compartment upper deck (the flight deck) with fixed seats; power system upgrades; and installation of an airlock on the crew compartment lower deck (the mid-deck).

Flight 10 (14-16 November 1980) would be a near-copy of Flight 8. A three-person Columbia crew would deploy TDRS-B/IUS and SBS-B/SSUS-D into a 160-n-mi-high orbit. The rocket stages would then boost the satellites to GEO. Cargo mass up would total 53,744 pounds; mass down, 11,443 pounds.

Flight 11 (18-25 December 1980) would see the orbital debut of Spacelab. Columbia would orbit Earth 160 n mi high at 57° of inclination. NASA and the multinational European Space Research Organization (ESRO) agreed in August 1973 that Europe should develop and manufacture Spacelab pressurized modules and unpressurized pallets for use in the Space Shuttle Program. Initially dubbed the "sortie lab," Spacelab would operate only in the Orbiter payload bay; it was not intended as an independent space station, though many hoped that it would help to demonstrate that an Earth-orbiting station could be useful.

ESRO merged with the European Launcher Development Organization in 1975 to form the European Space Agency (ESA). Columbia's five-person crew for Flight 11 would probably include scientists and at least one astronaut from an ESA member country.

Flight 12 (30 January-1 February 1981), a near-copy of Flights 8 and 10, would see Columbia's three-person crew deploy TDRS-C/IUS and Anik-C/2/SSUS-D into 160-n-mi-high orbit. Payload mass up would total 53,744 pounds; mass down, 11,443 pounds.

JSC planners inserted an optional "Flight 12 Alternate" (30 January-4 February 1981) into their schedule which, if flown, would replace Flight 12. Columbia would orbit 160 n mi above the Earth. Its three-person crew would deploy Anik-C/2 on a SSUS-D stage. The mission's main purpose, however, would be to create a backup launch opportunity for an Intelsat V-class satellite already scheduled for launch on a U.S. Atlas-Centaur or European Ariane I rocket. An SSUS-A stage would boost the Intelsat V from Shuttle orbit to GEO.

NASA JSC assumed that, besides the satellites, stages, and their support hardware, Columbia would for Flight 12 Alternate tote an attached payload of opportunity that would need to operate in space for five days to provide useful data (hence the mission's planned duration). Payload mass up would total 37,067 pounds; mass down, 17,347 pounds.

Space Shuttle Flights 13 through 18 would include the first orbital mission of the OV-101 Enterprise (Flight 17), during which astronauts would retrieve the LDEF payload deployed during Flight 7. Image credit: NASA.

Flight 13 (3-8 March 1981) would see three astronauts on board Columbia release NOAA's GOES-E satellite attached to an SSUS-D stage into a 160-n-mi-high orbit. OV-102 would have room for two payloads of opportunity: one attached at the front of the payload bay and one deployed from a turntable aft of the GOES-E/SSUS-D combination. Payload mass up would total 38,549 pounds; mass down, 23,647 pounds.

Flight 14 would last 12 days, making it the longest described in the STS Flight Assignment Baseline document. Scheduled for launch on 7 April 1981, it would carry a "train" of four unpressurized Spacelab experiment pallets and an "Igloo," a small pressurized compartment for pallet support equipment. The Igloo, though pressurized, would not be accessible to the five-person crew. OV-102 would orbit 225 n mi high at an inclination of 57°. Mass up would total 31,833 pounds; mass down, 28,450 pounds.

Flight 15 (13-15 May 1981) would be a near-copy of Flights 8, 10, and 12. OV-102 would transport to orbit a payload totaling 53,744 pounds; payload mass down would total 11,443 pounds. The JSC planners noted the possibility that none of the potential payloads for Flight 15 — TDRS-D and SBS-C or Anik-C/3 — would need to be launched as early as May 1981. TDRS-D was meant as an orbiting spare; if the first three TDRS operated as planned, its launch could be postponed. Likewise, SBS-C and Anik-C/3 were each a backup for the previously launched satellites in their series.

Flight 16 (16-23 June 1981) would be a five-person Spacelab pressurized module flight aboard OV-102 in 160-n-mi-high orbit. Payloads of opportunity totaling about 18,000 pounds might accompany the Spacelab module; for planning purposes, a satellite and SSUS-D on a turntable behind the module was assumed. Payload mass up would total 35,676 pounds; mass down, 27,995 pounds.

Flight 17, scheduled for 16-20 July 1981, would see the space debut of Enterprise and the retrieval of the LDEF released during Flight 7. OV-101 would climb to a roughly 200-n-mi-high orbit (LDEF's altitude after 13.5 months of orbital decay would determine the mission's precise altitude).

Before rendezvous with LDEF, Flight 17's three-man crew would release an Intelsat V/SSUS-A and a satellite payload of opportunity. After the satellites were sent on their way, the astronauts would pilot Enterprise to a rendezvous with LDEF, snare it with the RMS, and secure it in the payload bay. Mass up would total 26,564 pounds; mass down, 26,369 pounds.

For Flight 18 (29 July-5 August 1981), Columbia would carry to a 160-n-mi-high orbit a Spacelab pallet dedicated to materials processing in the vacuum and microgravity of space. The three-person flight might also include the first acknowledged Department of Defense (DOD) payload of the Space Shuttle Program, a U.S. Air Force pallet designated STP-P80-1. JSC called the payload "Planned" rather than "Firm" and noted somewhat cryptically that it was the Teal Ruby experiment "accommodated from OFT [Orbital Flight Test]."

The presence of the Earth-directed Teal Ruby sensor payload would account for Flight 18's planned 57° orbital inclination, which would take it over most of Earth's densely populated areas. Payload mass up might total 32,548 pounds; mass down, 23,827 pounds.

Space Shuttle Flights 20 through 23 would include the first mission to make use of an OMS kit to increase its orbital altitude (Flight 21), the first European Space Agency-sponsored Spacelab mission (Flight 22), and the launch of the Jupiter Orbiter and Probe spacecraft (Flight 23). Image credit: NASA.

Flight 19 (2-9 September 1981) would see five Spacelab experiment pallets fill Columbia's payload bay. Five astronauts would operate the experiments, which would emphasize physics and astronomy. The Orbiter would circle Earth in a 216-n-mi-high orbit. Payload mass up would total 29,214 pounds; mass down, 27,522 pounds.

Flight 20 (30 September-6 October 1981), the second Enterprise mission, would see five astronauts conduct life science and astronomy experiments in a 216-n-mi-high orbit using a Spacelab pressurized module and an unpressurized pallet. JSC planners acknowledged that the mission's down payload mass (34,248 pounds) might be "excessive," but noted that their estimate was "based on preliminary payload data." Mass up would total 37,065 pounds.

On Flight 21, scheduled for launch on 14 October 1981, Columbia would carry the first Orbital Maneuvering System (OMS) Kit at the aft end of its payload bay. The OMS Kit would carry enough supplemental propellants for the Orbiter's twin rear-mounted OMS engines to perform a velocity change of 500 feet per second. This would enable OV-102 to rendezvous with and retrieve the Solar Maximum Mission (SMM) satellite in a 300-n-mi-high orbit.

Three astronauts would fly the five-day mission, which would attain the highest orbital altitude of any flight in the STS Flight Assignment Baseline document. JSC planners noted that the Multi-mission Modular Spacecraft (MMS) support hardware meant to carry SMM back to Earth could also transport an MMS-type satellite into orbit. Payload mass up would total 37,145 pounds; mass down, 23,433 pounds.

On Flight 22 (25 November-2 December 1981), Enterprise might carry an ESA-sponsored Spacelab mission with a five-person crew, a pressurized lab module, and a pallet to a 155-to-177-n-mi orbit inclined at 57°. Payload mass up might total 34,031 pounds; mass down, 32,339 pounds.

During Flight 23 (5-6 January 1982), the last described in the STS Flight Assignment Baseline document, three astronauts would deploy into a 150-to-160-n-mi-high orbit the Jupiter Orbiter and Probe (JOP) spacecraft on a stack of three IUSs. President Jimmy Carter had requested new-start funds for JOP in his Fiscal Year 1978 NASA budget, which had taken effect on 1 October 1977. Because JOP was so new when they prepared their document, JSC planners declined to estimate up/down payload masses.

Flight 23 formed an anchor point for the Shuttle schedule because JOP had a launch window dictated by the movements of the planets. If the automated explorer did not leave for Jupiter between 2 and 12 January 1982, it would mean a 13-month delay while Earth and Jupiter moved into position for another launch attempt.

Almost nothing in the October 1977 STS Flight Assignment Baseline document occurred as planned. It was not even updated quarterly; no update had been issued as of mid-November 1978, by which time the target launch dates for the first Space Shuttle orbital mission and the first operational Shuttle flight had slipped officially to 28 September 1979 and 27 February 1981, respectively.

The Space Shuttle Orbiter Columbia lifts off at the start of STS-1. Image credit: NASA.

The first Shuttle flight, designated STS-1, did not in fact lift off until 12 April 1981. As in the STS Flight Assignment Baseline document, OV-102 Columbia performed the OFT missions; OFT concluded, however, after only four flights. After the seven-day STS-4 mission (27 June-4 July 1982), President Ronald Reagan declared the Shuttle operational.

The first operational flight, also using Columbia, was STS-5 (11-16 November 1982). The mission launched SBS-3 and Anik-C/3; because of Shuttle delays, the other SBS and Anik-C satellites planned for Shuttle launch had already reached space atop expendable rockets.

To the chagrin of many Star Trek fans, Enterprise never reached space. NASA decided that it would be less costly to convert Structural Test Article-099 into a flight-worthy Orbiter than to refit Enterprise for spaceflight after the ALT series. OV-099, christened Challenger, first reached space on mission STS-6 (4-9 April 1983), which saw deployment of the first TDRS satellite.

NASA put OV-101 Enterprise to work in a variety of tests and rehearsals (such as the "fit check" shown in the image above), but did not convert it into a spaceflight-worthy Orbiter. Image credit: NASA.

The voluminous Spacelab pressurized module first reached orbit on board Columbia on mission STS-9 (28 November-8 December 1983). The 10-day Spacelab 1 mission included ESA researcher Ulf Merbold and NASA scientist-astronauts Owen Garriott and Robert Parker.  Garriott, selected to be an astronaut in 1965, had flown for 59 days on board the Skylab space station in 1973. Parker had been selected in 1967, but STS-9 was his first spaceflight.

The 21,500-pound LDEF reached Earth orbit on board Challenger on STS-41C, the 11th Space Shuttle mission (6-13 April 1984). During the same mission, astronauts captured, repaired, and released the SMM satellite, which had reached orbit on 14 February 1980 and malfunctioned in January 1981. Challenger reached SMM without an OMS kit; in fact, no OMS kit ever reached space.

STS Flight Assignment Baseline document assumed that 22 Shuttle flights (six OFT and 16 operational) would occur before January 1982. In fact, the 22nd Shuttle flight did not begin until October 1985, when Challenger carried eight astronauts and the West German Spacelab D1 into space (STS-61A, 30 October-6 November 1985). Three months later (28 January 1986), Challenger was destroyed at the start of STS-51L, the Shuttle Program's 25th mission.

In addition to seven astronauts — NASA's first in-flight fatalities — Challenger took with it TDRS-B, NASA's second TDRS satellite. The Shuttle would not fly again until September 1988 (STS-26, 29 September-3 October 1988). On that mission, OV-103 Discovery deployed TDRS-C. The TDRS system would not include the three satellites necessary for global coverage until TDRS-D reached orbit on board Discovery on mission STS-29 (13-18 March 1989).

Following the Challenger accident, NASA abandoned — though not without some resistance — the pretense that it operated a fleet of cargo planes. The space agency had at one time aimed for 60 Shuttle flights per year; between 1988 and 2003, the Shuttle Program managed about six per year. The most flights the Shuttle fleet accomplished in a year was nine in 1985.

Shuttle delays meant that JOP, renamed Galileo, missed its early January 1982 launch window. It was eventually rescheduled for May 1986, but the Challenger accident intervened. Galileo finally left Earth orbit on 18 October 1989 following deployment from OV-104 Atlantis during STS-34 (18-23 October 1989).

Between the time JOP/Galileo received its first funding and the Challenger explosion, NASA, the White House, and Congress had sparred over how the Jupiter spacecraft would depart Earth orbit. Eventually, they settled on the powerful liquid-propellant Centaur-G' rocket stage.

Citing new concern for safety following Challenger, NASA canceled Centaur G'. Galileo had to rely on the less-powerful IUS, which meant that it could not travel directly to Jupiter; it had instead to perform gravity-assist flybys of Venus and Earth to reach its exploration target. Galileo did not reach the Jupiter system until December 1995.

LDEF had been scheduled for retrieval in March 1985, less than a year after deployment, but flight delays and the Challenger accident postponed its return to Earth by nearly six years. On mission STS-32 (9-20 January 1990), astronauts on board Columbia retrieved LDEF, the orbit of which had decayed to 178 n mi. LDEF remains the largest object ever retrieved in space and returned to Earth.

During reentry at the end of mission STS-107 (16 January-1 February 2003), Columbia broke apart over northeast Texas, killing its international crew of seven astronauts. This precipitated cancellation of the Space Shuttle Program by President George W. Bush, who announced his decision on 14 January 2004.

The end of the Space Shuttle Program was originally scheduled for 2010, immediately following the planned completion of the International Space Station. In the event, STS-135, the final Space Shuttle mission, took place four years ago (July 2011), three months after the 30th anniversary of STS-1. The Orbiter Atlantis lifted off on 8 July with a four-person crew — the smallest since STS-6. It docked with the International Space Station to deliver supplies and spares and landed in Florida 13 days later.

Sources

STS Flight Assignment Baseline, JSC-13000-0, STS Utilization and Planning Office, NASA Johnson Space Center, 15 October 1977.

"MSF Schedule Assessment of Major Space Shuttle Milestones (SENSITIVE)," J. Yardley and M. Malkin, 31 January 1975.

More Information

Flying Brickyard Postponed: A 1972-1973 Study of an Interim Ablative Space Shuttle Heat Shield

Where to Launch and Land the Space Shuttle? (1971-72)

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

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

Wernher von Braun in his office at NASA Marshall Space Flight Center. Image credit: NASA.

At the 7th International Astronautical Congress, held in Rome in September 1956, Italian aviation and rocketry pioneer Gaetano Crocco described a piloted space mission in which a spacecraft would conduct a reconnaissance flyby of Mars, swing past Venus to bend its course toward Earth, and, one year to the day after departing Earth orbit, reenter Earth's atmosphere. After Earth-orbit departure, the spacecraft would need no additional propulsion. Crocco told the assembled delegates that an opportunity to commence such a mission would next occur in June 1971.

A little less than six years later, in May 1962, the Future Projects Office (FPO) at NASA's Marshall Space Flight Center (MSFC) in Huntsville, Alabama, awarded manned Mars mission study contracts worth $250,000 each to General Dynamics, Lockheed, and the Aeronutronic Division of Ford Motor Company. General Dynamics was instructed to study Mars orbital missions, Lockheed to look at Mars flyby and orbital missions, and Aeronutronic to study dual-planet (Mars-Venus) flybys. The combined study effort was known as EMPIRE, an evocative (if somewhat tortured) acronym that stood for Early Manned Planetary-Interplanetary Roundtrip Expeditions.

EMPIRE took place against the backdrop of the Apollo lunar program. One year before its start, in a speech before a special joint session of Congress, President John F. Kennedy had put NASA on course for the Moon. He had given the U.S. civilian space agency, which had been founded less three years earlier, until the end of the 1960s to achieve his goal. It was hoped, however, that an American could land on the Moon as early as 1967, during Kennedy's second term in office.

As EMPIRE began, NASA had nearly completed the contentious 14-month process of choosing the fastest, most reliable, and cheapest way of placing men on the Moon. The Lunar Orbit Rendezvous mode, which would rely on MSFC's Saturn C-5 rocket, was selected in July 1962, before EMPIRE reached its conclusion. C-5 was soon renamed Saturn V.

MSFC was fertile ground for NASA's first major manned planetary mission study. The Huntsville Center's director was Wernher von Braun, a famous advocate of piloted flight to the Moon and Mars. Von Braun's efforts in the 1950s to popularize spaceflight had helped to prime the American public for the 1960s Space Race with the Soviet Union.

EMPIRE was, however, not merely the whim of a long-time Moon and Mars fan; it was also part of a strategy to protect and promote MSFC. The Huntsville Center's specialty was rocket development. Its engineers hoped to develop rockets larger than the Saturn V, which they dubbed Nova and Supernova. Von Braun knew that, unless a post-Apollo program was in place as MSFC's Apollo responsibilities wound down in 1966 and 1967, his center would suffer deep staff and funding cuts, not develop new big rockets.

The Saturn family of rockets was expected to lead to larger Nova and Supernova rockets by the end of the 1960s. In the illustration above, dating from early 1962, the three-stage C-1 and four-stage C-5 are anemic predecessors to the Apollo Saturn IB and Saturn V designs. The Apollo-Saturn rockets later adopted features of the proposed (but never flown) Nova depicted; in particular, the Nova rocket's 22-foot-diameter third stage. Image credit: NASA.

Besides calling for a man on the Moon, President Kennedy's May 1961 speech had requested new funding for nuclear propulsion. MSFC was involved in joint NASA/Atomic Energy Commission (AEC) nuclear rocket development through the Reactor In Flight Test (RIFT) program. The precise form the RIFT mission would take changed rapidly; for a time, it aimed to launch a 33-foot-diameter rocket stage with a NERVA nuclear engine on a Saturn V in 1967. Another goal of EMPIRE was, thus, to create a justification for NERVA and RIFT.

In the introduction to their December 1962 EMPIRE final report, Aeronutronic's engineers praised NASA for its "forward thinking approach." They added that

[b]y attacking the areas of interest at this early date[,] it will be possible to obtain a clearer picture of the requirements for early manned planetary and interplanetary flight. Thus the nation's resources, and the NASA and other United States space programs[,] can be oriented toward long range goals at an early date. [EMPIRE] represents an unusually early attack on this type of analysis.

Aeronutronic looked at two interplanetary trajectories for its dual-planet piloted flyby mission. The first was dubbed the Crocco trajectory because it was based on the scenario in Crocco's 1956 paper. The second was the symmetric trajectory, which would see the flyby spacecraft swing around the Sun one-and-a-half times. It would fly past Mars halfway through its mission and would cross the orbit of Venus once before the Mars flyby and once after. It would swing past Venus during one of the orbit crossings.

Interplanetary trajectory types Ford Aeronutronic considered for its Mars/Venus flyby mission. Image credit: Ford Aeronutronic/NASA.

Aeronutronic engineers found that Crocco had been mistaken when he wrote that an opportunity to start an Earth-Mars-Venus-Earth voyage would occur in June 1971. They determined that a dual-planet Crocco mission could depart Earth in mid-to-late August 1971. A symmetric Earth-departure opportunity would occur sooner: between 16 July and 19 August 1970.

The Crocco trajectory would require more propulsive energy than the symmetric trajectory, Aeronutronic found. The amount of energy required would depend on the moment during the launch opportunity that the spacecraft left Earth orbit. Aeronutronic, however, selected single representative values for preliminary design purposes.

Assuming a departure from a 300-kilometer-high circular Earth orbit, a Crocco spacecraft launched in August 1971 would need to increase its speed by 11.95 kilometers per second to achieve the desired dual-planet flyby trajectory. A symmetric mission launched in the July-August 1970 window would, by contrast, need a velocity increase of only 5.3 kilometers per second.

Low departure velocity meant reduced propellant requirements. In short, a symmetric mission would have a much lower mass than a Crocco mission. A low-mass spacecraft would need fewer launches to place its components and propellants into Earth orbit. Fewer launches would mean lower mission cost and less chance that a launch vehicle would fail and destroy its payload, perhaps placing the assembly campaign in Earth orbit in jeopardy. It would also mean less complex orbital assembly (or perhaps no assembly at all, if a Nova rocket were used), further trimming mission risk.

Aeronutronic found that no dual-planet Crocco mission could last only 365 days; for design purposes, the study team assumed that a mission launched in the August 1971 opportunity would last 396 days. Though longer than Crocco had estimated, this was much less than the 611-day representative duration Aeronutronic selected for the July-August 1970 symmetric opportunity.

Aeronutronic's engineers determined that radiation and meteoroid shielding and life support masses, which would increase with trip time, would not approach the mass of the propellant required to launch the Crocco mission out of Earth orbit; they thus accepted the symmetric mission's greater duration.

The symmetric mission would have a low Earth-departure speed, but would pay for it by having a high Earth-atmosphere reentry speed. As a general rule, the faster a spacecraft is moving as it plummets into Earth's atmosphere, the more reentry heating it will undergo. Greater heating calls for more massive thermal control systems; basically, active cooling employing coolant loops and radiators and a thick heat shield that ablates (that is, chars and erodes away, carrying away heat). The re-entering spacecraft might also use a braking rocket to slow itself before reentry.

The Aeronutronic engineers did not consider the difference between the Crocco and symmetric Earth-atmosphere reentry speeds to be significant. For a symmetric mission launched between 16 July and 19 August 1970, reentry speed would top out at 15.8 kilometers per second; the corresponding figure for the August 1971 Crocco opportunity was 13.5 kilometers per second. The propellant mass and Earth-to-orbit launch vehicles saved as a result of the Crocco mission's somewhat slower Earth atmosphere-reentry speed were minimal compared with the mass and launchers saved by the symmetric mission's dramatically reduced Earth-departure velocity.

Dual-planet flyby spacecraft size comparisons. Note comparison with Mercury-Atlas rocket and spacecraft (lower right). Mercury was the only piloted U.S. spacecraft that had flown at the time Ford Aeronutronic completed its study. Image credit: Ford Aeronutronic/NASA.

Aeronutronic calculated that, based on the mission design values that it had selected, the nuclear Crocco dual-planet flyby spacecraft would have a fully assembled, fully fueled mass of 1121.5 tons, while an equivalent nuclear symmetric spacecraft would have a mass of only 188 tons. This would place the latter within the planned payload capacity of a single Nova rocket, eliminating Earth-orbit assembly entirely.

The Aeronutronic engineers did not bother to determine the mass of a chemical Crocco spacecraft because they knew that it would be even greater than that of the nuclear Crocco spacecraft. They calculated, however, that the chemical symmetric spacecraft would have a mass of 350.5 tons (nearly twice that of the nuclear symmetric spacecraft) or 929.5 tons (nearly as much as the nuclear Crocco spacecraft) depending on the thrust capability of its rocket motor. The company thus selected the nuclear symmetric mission for more detailed study.

Aeronutronic envisioned a 156-foot-long, 33-foot-wide symmetric dual-planet flyby spacecraft with a single 18,300-pound NERVA engine capable of generating 50,000 pounds of thrust. A tungsten shield at the front of the drum-shaped NERVA reactor would create a radiation shadow that would encompass the crew modules during Earth-orbit departure.

The engine would need to operate for nearly 48 minutes to boost the spacecraft's speed by 5.3 kilometers per second and place it onto its symmetric trajectory. Aeronutronic identified the lengthy burn time as a possible show-stopper; available reactor materials, it explained, could not withstand such prolonged operation. Increasing thrust would reduce required burn time, but the company was not confident that a nuclear engine with more than 50,000 pounds of thrust could be developed in time for the July-August 1970 symmetric launch opportunity.

The nuclear symmetric spacecraft became Ford Aeronutronic's dual-planet flyby mission baseline design. Image credit: Ford Aeronutronic/NASA.

Two tank clusters would supply liquid hydrogen propellant to the NERVA engine. The first-stage cluster, which would contain 56.2 tons of propellant, would comprise a core propellant tank to which the NERVA engine would be mounted and six detachable "perimeter" tanks. After expending the first-stage propellant and discarding the perimeter tanks, the spacecraft would have a mass of 127.7 tons.

Eight second-stage tanks would then supply a total of 38.3 tons of liquid hydrogen to the NERVA engine. After it expended its second-stage propellant, the NERVA engine would detach along with the empty first-stage core tank.

The empty second-stage tanks, with a total mass of 5.2 tons, would be retained to shield the Aeronutronic flyby spacecraft's cylindrical central core from meteoroids. After NERVA engine/first-stage propellant separation, the spacecraft would have a mass of 76.7 tons and would measure about 78 feet long.

From aft to front, the core would comprise twin SNAP-8 nuclear reactors for generating electricity, the spacecraft's navigational stable platform, a small compartment for weightless experimentation, and a 20-ton command center/solar flare radiation shelter clad in 50 centimeters of polyethylene plastic. Four tanks containing a total of 10.9 tons of chemical trajectory-correction propellants would surround the command center/shelter, providing additional radiation shielding. A two-stage reentry braking propulsion module ("retro-pack") and the Earth-atmosphere reentry vehicle would be attached to the command center/shelter at the front of the spacecraft.

Earth-orbit departure completed, the six-man crew would reconfigure their spacecraft for the interplanetary voyage. The twin cylindrical living modules, each with an empty mass of 4.5 tons, would extend on hollow telescoping arms, and one SNAP-8 would deploy a radiator panel and begin generating electricity (the other would be held in reserve in case the first failed).

The crew would then spin their spacecraft about its long axis at a rate of three revolutions per minute to create acceleration in the living modules which they would feel as gravity. Sixteen-meter-diameter dish antennas would unfurl from the aft end of both living modules to ensure continuous radio communication with Earth. Aeronutronic noted that, when the spacecraft was farthest from Earth, one-way radio-signal trip time would reach 22 minutes.

The nuclear symmetric spacecraft would undergo configuration changes as it carried out its mission, casting off parts that were no longer useful and deploying power, communications, and artificial-gravity systems. The spacecraft would spend most of the flight in the configuration labeled "on-orbit spacecraft." Please click on image to enlarge. Image credit: Ford Aeronutronic/NASA.

Based on experience with nuclear submarine crews, Aeronutronic allocated 750 cubic feet of living space to each astronaut, except inside the command center/radiation shelter, where it judged that 50 cubic feet per man would suffice. The twin living modules and command center/shelter would each have an independent life support system designed to recycle all air and water. The company estimated that life support mass would total 10.9 tons, of which food would make up nearly five tons.

The six-man crew would follow a complex schedule designed to combat boredom while providing adequate rest and recreation. Except for sleep, crew activities would occur in two-hour blocks. The crew would include a Commanding Officer, an Executive Officer, a Flight Surgeon, and three astronauts identified simply as "crew members." All six would take it in turns to serve as duty officer in the command center/shelter, maintenance and repair crewmember, and scientific activity crewmember. The Commanding Officer and Flight Surgeon would not, however, take part in hazardous repairs (for example, those involving spacewalks).

Symmetric Mars-Venus piloted flyby trajectory: 1 = Earth launch; 2 = Venus orbit crossing (possible flyby); 2* = second Venus orbit crossing (possible flyby); 3 = Mars orbit crossing; 3* = second Mars orbit crossing; 4 = Mars flyby/Earth position during Mars flyby; 5 = Earth return. Image credit: Ford Aeronutronic/NASA.

A symmetric dual-planet flyby mission departing Earth in the 16 July-19 August 1970 opportunity would fly first past Venus between 97 and 102 days after launch from Earth orbit. Departure at the start of the launch opportunity would yield the shortest trip time on each leg of the interplanetary voyage (and shortest total trip time — 611 days); departure at the end of the opportunity would yield the longest trip time on each leg (and longest total — 631 days). Earth-departure near the start of the opportunity would yield a Venus flyby distance of about 4890 miles; the corresponding figure for the end of the opportunity would be 7520 miles.

As the spacecraft approached Venus, the crew would fire the trajectory-correction motors, changing their speed by about 650 feet per second to ensure an on-target flyby. The spacecraft would carry enough course-correction propellants to change its velocity by a total of 2000 feet per second.

Citing a November 1961 report planetary astronomer Gérard de Vaucouleurs had prepared for the U.S. Air Force, Aeronutronic allotted 1000 pounds for scientific equipment for studying Venus and Mars. The company declined, however, to define a scientific payload for its spacecraft, arguing that the EMPIRE mission's science objectives at Mars and Venus would be shaped by data from NASA robotic spacecraft launched between 1962 and 1968.

The Mars flyby would occur between 191 and 199 days after the Venus flyby, at the midpoint of the symmetric mission. During Mars approach, the crew would perform a second trajectory-correction burn, changing their spacecraft's speed by 330 feet per second. Mars flyby distance would range from about 2740 miles for an Earth departure at the beginning of the July-August 1970 opportunity to 4220 miles for a departure at its end.

An EMPIRE ground rule was that the contractors should use Apollo hardware and techniques wherever feasible, though this was not strictly enforced. The conical Apollo Command Module (CM) with its bowl-shaped ablative heat shield was considered a prime candidate for use as EMPIRE's Earth-reentry vehicle, but Aeronutronic rejected it.

The company opted instead for a 14.75-ton lifting-body with a pointed nose and a two-stage chemical-propellant retro-pack. Aeronutronic had determined that the lifting-body shape was more tolerant of reentry errors — that is, that it would be less likely to burn up or skip off the atmosphere — than the Apollo capsule. The lifting-body would, Aeronutronic noted, also offer a broader choice of land landing or sea splashdown sites because of its enhanced ability to maneuver in the atmosphere.

Ford Aeronutronic's preferred Earth-return reentry vehicle configuration. Image credit: Ford Aeronutronic/NASA.

Landing/splashdown site flexibility would become especially useful if an abort during Earth departure became necessary. Aeronutronic found that the retro-pack, intended to slow the reentry vehicle as it neared Earth at the end of the mission, could return the crew to Earth no later than 16.7 hours after Earth-orbital launch provided that an abort was initiated before the flyby spacecraft passed beyond about 12,000 miles from Earth.

If, however, the mission unfolded as planned, the astronauts would return to Earth between 312 and 343 days after passing Mars. Prior to reentry, they would perform the final trajectory-correction burn of the mission, changing their spacecraft's speed by about 360 feet per second. Shortly thereafter, the astronauts would strap into the Earth-reentry lifting-body and fire small solid-propellant rocket motors to separate it from the flyby spacecraft. The abandoned flyby spacecraft would subsequently swing past Earth and enter a disposal orbit around the Sun.

After properly orienting the Earth-reentry vehicle, the crew would ignite the two stages of its nose-mounted retro-pack in succession, steering the lifting-body toward its reentry corridor and reducing its reentry velocity by 2.8 kilometers per second to 13 kilometers per second. The stages would detach in turn as they expended their propellants.

During reentry, the hottest part of the vehicle would be its small pointed nose, which Aeronutronic expected would be actively cooled to prevent melting. A blowtorch-like plume of superheated plasma would trail from the nose beneath the lifting-body, but would not contact its concave underside.

The astronauts, who would recline facing away from the nose, would experience deceleration equal to 10 Earth gravities, which they would feel against their backs. After deceleration and descent into the lower atmosphere, the lifting-body would deploy parachutes and descend more or less vertically.

Aeronutronic provided a detailed development schedule and cost estimate for its nuclear symmetric dual-planet flyby mission. The company placed the mission's cost at $12.6 billion, or about half the projected Apollo Program cost. Cost savings would be due in large part to experience gained and hardware developed during Apollo. Peak funding year, with expenditures totaling about $3.5 billion, would be 1966.

Aeronutronic estimated that development of a 50,000-pound-thrust NERVA engine capable operating continuously for 60 minutes would need to begin on 1 January 1963 (that is, 10 days after the company completed its final report for MSFC FPO), as would development of the Earth-reentry lifting body. NERVA engines would be tested at the Nuclear Rocket Development Station (NRDS) at Jackass Flats, Nevada, beginning in mid 1965. Earth-reentry vehicles would be drop-tested over the dry lake bed at Edwards Air Force Base in California beginning in mid-1966 and would be flight-tested with and without a crew using Saturn C-1 boosters beginning a year after that.

Flyby spacecraft development would begin in early 1964, shortly before crew selection and the start of Nova development. Beginning in mid-1967, Saturn C-5 rockets would launch three symmetric dual-planet flyby spacecraft without Earth-reentry vehicles into Earth orbit for testing.

A total of 13 Nova rockets would be required for ground and flight testing between mid-1966 and late 1969. Of these, the first four would be Nova development flights and the last three would launch complete manned symmetric dual-planet flyby spacecraft into Earth orbit for testing and crew training. The fourteenth Nova, designated N9, would launch the mission spacecraft and crew into 300-kilometer-high Earth orbit on 15 July 1970, the day before the symmetric launch opportunity was set to begin.

In a paper presented 10 months after Ford Aeronutronic delivered its final report to MSFC FPO, Franklin Dixon declared that development of an improved NERVA engine should have begun no later than July 1963 if it was to become available in time for the 16 July-19 August 1970 symmetric dual-planet flyby launch opportunity. Dixon had not participated in EMPIRE; on 1 July 1963, Ford had placed Aeronutronic under its Philco division, and Dixon had become Philco Aeronutronic's Manager for Advanced Space Systems.

Cutaway illustration of NERVA nuclear-thermal rocket engine. Image credit: NASA.

NERVA development lagged behind the schedule Dixon said was necessary in part because of Kiwi-B nuclear rocket engine failures in December 1961, September 1962, and November 1962. As the name implies, the Kiwi series engines were not meant for flight. In fact, though they each included a nozzle and blasted super-hot hydrogen gas into the air, they were considered nuclear reactors, not nuclear rocket engines. 

The three failures were similar in nature: liquid hydrogen moving through the hot reactor core caused vibration which broke and eroded the reactor's uranium fuel rods. Hot gaseous hydrogen exhaust then blew uranium fragments out through the engine nozzle. The melting fragments sparkled as they sprayed into the open air.

The Kiwi-B failures set off a duel between the President's Science Advisory Council and the Bureau of the Budget on the one hand and NASA and the Atomic Energy Commission, championed by New Mexico Senator Clinton Anderson, on the other. Democrat Anderson's state contained Los Alamos National Laboratory, which led the AEC side of the nuclear rocket program.

President Kennedy visited the NRDS in early December 1962 to size up the situation. On 12 December 1962, two weeks before Ford Aeronutronic completed its EMPIRE study, he indefinitely postponed RIFT. Citing fiscal restraint, Kennedy's successor, Lyndon Johnson, cancelled RIFT altogether in December 1963, and made NERVA a wholly ground-based research and development effort.

In December 1967, the NRX-A6 NERVA ground-test engine operated for 60 minutes without a hitch; that is, for longer than would have been required to boost Aeronutronic's dual-planet flyby spacecraft out of Earth orbit and onto its symmetric trajectory. Nevertheless, President Richard Nixon cancelled NERVA in 1972 after program expenditures totaling $1.4 billion.

The Nova rocket experienced a less protracted and costly demise. By June 1964, von Braun called publicly for piloted planetary flyby missions using Saturn V rockets and Apollo-derived hardware, thus acknowledging that the Lunar Orbit Rendezvous decision of July 1962 had all but doomed large rockets like Nova.

Later in 1964, the Bureau of the Budget declared Nova rocket development to be of low priority, and called for NASA's post-Apollo program to be confined to Earth orbit and based on hardware developed for Apollo. The MSFC FPO would publish a feasibility study of an Apollo-derived piloted flyby mission in early 1965.

Sources

EMPIRE: A Study of Early Manned Interplanetary Expeditions, NASA Contractor Report 51709, Aeronutronic Division, Ford Motor Company, 21 December 1962.

"The EMPIRE Dual Planet Flyby Mission," Franklin P. Dixon, Aeronutronic Division, Philco Corporation; paper presented at the Engineering Problems of Manned Interplanetary Exploration conference, 30 September-1 October 1963.

"EMPIRE: Early Manned Planetary-Interplanetary Roundtrip Expeditions Part I: Aeronutronic and General Dynamics Studies," Frederick I. Ordway III, Mitchell R. Sharpe, and Ronald C. Wakeford, Journal of the British Interplanetary Society, May 1993, pp. 179-190.

More Information

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)

Flyby's Last Gasp: North American Rockwell's S-IIB Interplanetary Booster (1968)

MIT Saves the World: Project Icarus (1967)

Image credit: NASA.

Walter Baade used the 48-inch reflecting telescope at Palomar Observatory in southern California to capture humankind's first image of asteroid 1566 Icarus on 26 June 1949. Icarus showed up as a nondescript streak set against the myriad stars on a glass photographic plate. Icarus, it was soon found, is unusual because its elliptical orbit takes it from the inner edge of the Main Asteroid Belt between the orbits of Mars and Jupiter to well within Mercury's orbit. Icarus needs 1.12 years to circle the Sun once. 

Every nine, 19, or 28 years, always during the month of June, Icarus and Earth reach their point of closest approach, during which they typically pass each other at a relative velocity of about 29 kilometers (18 miles) per second. Baade detected Icarus during one of these close encounters.

MIT Professor Paul Sandorff taught the Interdepartmental Student Project in Systems Engineering in the Spring 1967 term at the Massachusetts Institute of Technology (MIT). At the beginning of the course, he told his students that, on 19 June 1968, Icarus and Earth would pass each other at a distance of 6.4 million kilometers (four million miles) — that is, about 15 times the Earth-Moon distance.

Sandorff then asked his students to suppose that, rather than miss Earth on that date, Icarus would instead strike the Atlantic Ocean east of Bermuda with the explosive force of 500,000 megatons of TNT. Debris flung into the atmosphere would cool the planet to some unknown degree and a 30-meter (100-foot) wave would inundate MIT. Sandorff gave his class until 27 May 1967 to develop a plan to avert the catastrophe.

In 1967, the physical characteristics of Icarus were poorly known. For purposes of their study, Sandorff's students assumed that it measured 1280 meters (4200 feet) in diameter and had an average density of 3.5 grams per centimeter, yielding a mass of 4.4 billion tons. For comparison, Earth has an average density of 5.5 grams per cubic centimeter.

They acknowledged, however, that, given its orbit, which resembles that of a short-period comet, Icarus might be a defunct comet nucleus. In that case, its density and mass would likely be considerably less. They also assumed that Icarus is a solid body; that is, that it is not made up of small pieces held together loosely by weak mutual gravitational attraction.

In March 1967, the MIT students visited Cape Kennedy, Florida, to size up U.S. space capabilities. At the time, the first piloted flight of the Apollo Command and Service Module (CSM) spacecraft had been postponed indefinitely following the Apollo 1 fire (27 January 1967) and the Saturn V Moon rocket had yet to fly. Apollo 4, the successful first Saturn V test flight, would not occur until 9 November 1967.

Nevertheless, the students wrote in their final report that "the awesome reality" of the giant structures NASA had built to launch astronauts to the Moon had "completely erased" any doubts they might have had about using Apollo/Saturn technology in their project. The structures included the Vertical Assembly Building (VAB), in which Apollo spacecraft and three-stage Saturn V Moon rockets were stacked together, and the twin Launch Complex 39 Saturn V launch pads (Pads 39A and 39B). One cannot help but wonder what their fall-back alternative might have been had they found the Apollo infrastructure wanting.

Apollo 11 liftoff on 16 July 1969. If Project Icarus had been necessary, the Apollo 11 Saturn V would have launched the automated Saturn-Icarus 3 Interceptor, not the first piloted Moon-landing mission. Image credit: NASA.

Professor Sandorff's students proposed to hijack Project Apollo, delaying NASA's first piloted lunar landing by about three years. They would have taken over the first nine Saturn V rockets earmarked for the Moon program, commenced construction in April 1967 of a third Launch Complex 39 launch pad (Pad 39C), and added a Saturn V assembly high bay to the VAB, bringing the total to four. NASA had planned to build Pad 39C, going so far as to build a road to the proposed pad site with appropriate signage (image at top of post), until funding cuts made an ambitious post-Apollo piloted space program increasingly unlikely.

Three of the nine Saturn V rockets would have been used for unmanned flight tests. The remainder would each have launched toward Icarus one heavily modified automated Apollo CSM bearing an 20,000-kilogram (44,000-pound) nuclear warhead with the destructive yield of 100 million tons of TNT.

Though the MIT students did not mention it, a 100-megaton warhead was never a component of the U.S. nuclear arsenal. Given the secrecy surrounding nuclear weapons during the Cold War, they probably could not have known that no 100-megaton warhead had ever been tested.

The most powerful nuclear bomb ever, the Soviet Union's 50-megaton "Tsar Bomba," exploded on 30 October 1961, triggering seismic sensors around the globe. Fifty megatons was about half its theoretical yield. The Soviet Union built only a single Tsar Bomba and the U.S. did not deign to match the Soviet feat.

Even had Tsar Bomba warheads been readily available, the Soviet super-bomb was likely so heavy that a Saturn V could not launch it to Icarus. It weighed as much as 27,000 kilograms (60,000 pounds).

The Apollo 14 Saturn V rocket rolls out of the immense VAB at Kennedy Space Center. Had Project Icarus been necessary, the rocket would have launched the automated Saturn-Icarus 6 Interceptor on 14 June 1968. Image credit: NASA.

The Icarus CSM — which the MIT students dubbed the Interceptor — would comprise three modules: a drum-shaped propulsion module corresponding to the Apollo Service Module (SM), with attitude-control thrusters and a Service Propulsion System (SPS) main engine; a drum-shaped payload module based on the SM's structural design but containing the 100-megaton nuclear device; and a stripped-down conical Command Module (CM) containing Icarus detection sensors and an MIT-designed Apollo Guidance Computer (AGC) modified for automated operation. Unlike the two-module Apollo CSM, the three modules of the Interceptor would have remained bolted together throughout its flight.

The first Project Icarus Saturn V (Saturn-Icarus 1) would have lifted off from Cape Kennedy on 7 April 1968, 73 days before the asteroid was due to collide with Earth. Its payload, Interceptor 1, would have reached Icarus 60 days later, when the asteroid was 13 days and 32.2 million kilometers (20 million miles) from Earth. At about the time Interceptor 1 was due to reach its target, the MIT Lincoln Laboratory's Haystack radar would have detected Icarus for the first time.

Saturn-Icarus 2 would have launched on 22 April 1968, 58 days before Icarus was due to strike. Interceptor 2 would have reached its target 25 million kilometers (15.5 million miles) and 10 days out from Earth.

Saturn-Icarus 3 would have lifted off on 6 May 1968, 44 days before Icarus was due to arrive, and its Interceptor would have reached Icarus one week and 17.7 million kilometers (11 million miles) from Earth. Saturn-Icarus 4 would have lifted off on 17 May 1968, 33 days before Icarus arrival, and Interceptor 4 would have reached the asteroid 28 days later, when Earth and Icarus were 12.4 million kilometers (7.7 million miles) apart.

Saturn-Icarus 5 would have left Earth near dawn on the U.S. East Coast on 14 June 1968, and Interceptor 5 would have reached Icarus 2.26 million kilometers (1.4 million miles) out from Earth, 22 hours before expected impact. By then, the asteroid would have appeared as a modest star in the predawn sky near the bright stars of the constellation Orion.

Saturn-Icarus 6 would have lifted off a few hours after Saturn-Icarus 5. When Interceptor 6 reached it, Icarus would have been about 20 hours and 2 million kilometers (1.25 million miles) from impact.

As each Interceptor closed to within 400,000 kilometers (250,000 miles) of Icarus, an optical sensor in its nose would have spotted the asteroid. The modified AGC would then have used the SPS and thrusters in the propulsion module to adjust the Interceptor's course to ensure a successful interception.

Apollo astronauts grew fond of the simple but capable MIT-developed Apollo Guidance Computer (AGC). For Project Icarus, MIT would have added an extra layer of automation so that the AGC could guide the unmanned Interceptor spacecraft to their target. Image credit: Wikipedia.

When an Interceptor closed to a distance of 170 meters (550 feet) from Icarus, a radar would have detected the asteroid and triggered the nuclear device, which would have exploded at a distance of from 15 to 30 meters (50 to 100 feet). If the students' assumptions about the asteroid's mass and density were correct, then each 100-megaton near-surface nuclear blast would have excavated on Icarus a bowl-shaped crater up to 300 meters (1000 feet) wide. The effect the explosions would have had on the asteroid's course was, of course, not known with precision; the students calculated that each blast would alter its velocity by between 8 and 290 meters (26 and 950 feet) per second.

The MIT students acknowledged that Icarus might shatter; in that event, subsequent Interceptors would have targeted the largest fragments. Data from each Interceptor as it approached Icarus and from Earth-based optical telescopes and radars would have been used to target subsequent Interceptors as required. Conversely, if fewer than six explosions were sufficient to deflect or pulverize the asteroid, then the remaining Saturn V rockets and Interceptors would have stood down.

The Project Icarus Intercept Monitoring Satellite (IMS) would have resembled NASA's Mariner 2 Venus flyby spacecraft. Image credit: NASA.

All but one of the Interceptors would be joined at Icarus by a separately launched 245-kilogram (540-pound) Intercept Monitoring Satellite (IMS) based on the Mariner 2 design. Mariner 2, the first successful interplanetary probe, had flown past Venus on 14 December 1962. In addition to data immediately useful for Project Icarus, the IMS would have provide pure science data.

The first IMS would have left Earth atop an Atlas-Agena rocket on 27 February 1968. It would have passed between 115 and 220 kilometers (70 and 135 miles) from Icarus at the time of the first nuclear explosion. This would have placed it outside of the zone of large high-velocity debris from the explosion, but within the zone of plasma, dust, and small debris. IMS-1 would have analyzed the small fragments and hot gases to determine the asteroid's composition. A 23-kilogram (50-pound) foam-honeycomb "bumper" would have shielded IMS-1 during passage through the debris cloud.

No IMS would have monitored the fifth interception (if it were judged necessary) unless the sixth interception had already been called off. The IMS for monitoring the sixth (or fifth) interception would have lifted off on 6 June 1968, between the Saturn-Icarus 4 and 5 launches.

Professor Sandorff's class estimated that Project Icarus would cost $7.5 billion. It would, they calculated, stand a 1.5% chance of only fragmenting the asteroid. If this happened, then Icarus might cause more damage to Earth than if it were permitted to impact intact. The probability that Project Icarus would reduce the damage Icarus would cause was, however, 86%, and the probability that it would succeed in preventing any part of the asteroid from reaching Earth was 71%.

During the June 1968 close approach, Icarus became the first asteroid to be detected using Earth-based radar. By analyzing data gathered over the decades during subsequent close approaches, scientists have found that Icarus is roughly spherical, rotates rapidly (about once every 2.25 hours), is probably a light-colored S-type asteroid made mostly of stony materials, and measures about 1400 meters (4600 feet) across. Its density is probably only about 2.5 grams per cubic centimeter.

The closest approach of Icarus to Earth since 19 June 1968 is taking place as I write this. On 16 June 2015, the asteroid will pass by Earth at a distance of about eight million kilometers (five million miles). It will zip through the northern-hemisphere constellations Ursa Major and Canes Venatici over the course of the day, though it will be too faint to view with unaided eyes. Closest approach to Earth will take place at 1539 UTC (11:39 AM U.S. Eastern Daylight Time). Icarus will not pass so close to Earth again until June 2090.

Sources

Project Icarus, MIT Report No. 13, Louis A. Kleiman, editor, The MIT Press, 1968.

Tsar Bomba: King of Bombs (http://www.tsarbomba.org/ — accessed 15 July 2015).

International Astronomical Union — Near Earth Asteroids: A Chronology of Milestones 1800-2200 (http://www.iau.org/public/themes/neo/nea/ — accessed 15 July 2015).

More Information

Earth Approaching Asteroids as Targets for Exploration (1978)

Multiple Asteroid Flyby Missions (1971)

To Mars By Way of Eros (1966)

Centaurs, Soviets, and Seltzer Seas: Mariner 2's Venusian Adventure (1962)

Pluto, Doorway to the Stars (1962)

Pluto and its five moons as observed by the Hubble Space Telescope. Charon is roughly half as large as Pluto; the other moons are much smaller. Image credit: NASA.

In just about a month, on 14 July 2015, New Horizons will fly by Pluto at a nominal distance of only 10,000 kilometers moving at a velocity of about 14 kilometers per second. At that speed and distance, the piano-sized 478-kilogram probe will briefly return images of Pluto in which objects as small as 50 meters wide might be visible.

Pluto was discovered in 1930, during Lowell Observatory's hunt for a planet beyond Neptune. The observatory, founded in 1894 by wealthy Bostonian Percival Lowell to find proof of intelligent life on Mars, had begun its search for a trans-Neptunian planet in 1906.

The search for Planet X (as Lowell dubbed his hypothetical world) was at least partly motivated by the growing disdain with which Lowell's Mars theories were greeted by professional astronomers. Lowell was eager that his observatory should be seen to be credible; discovery of a new planet would, he felt, restore and cement its eroded credibility.

Lowell employed a bevy of young women as "computers" to attempt to determine the position of Planet X based on the motion of the planet Neptune, which did not orbit the Sun precisely as expected. By assuming that Pluto had a mass six times as great as Earth, Lowell and his assistants narrowed the region of the sky where they expected to find Planet X to a portion of the constellation Gemini.

Percival Lowell did not live to see a trans-Neptunian world found (he died in 1916). Following his death, the search for Planet X stalled while his observatory and his widow feuded over the money he had bequeathed to endow Lowell Observatory in perpetuity. The search did not resume in earnest until 1929. When it did, it was meant to survey the entire ecliptic, the invisible line in the sky along which the planets move. The ecliptic corresponds to the plane of the Earth's orbit about the Sun.

On 18 February 1930, 23-year-old Lowell Observatory astronomer Clyde Tombaugh discovered that a tiny dot of light on photographic plates he had made on 23 January and 29 January 1930 had changed position slightly against the background stars. The small movement signified that the object Tombaugh found was moving slowly and thus was far from the Sun. The tiny dot in Gemini, near Lowell's predicted position for Planet X, was subsequently found on plates dating back to before Lowell's death.

Lowell Observatory revealed Tombaugh's find to the world on 18 March 1930, on what would have been Percival Lowell's 75th birthday. It named the object Pluto, for the god of the cold, dark Roman underworld. The observatory staff selected the name in part because its first two letters matched Percival Lowell's initials. Newspapers around the world hailed the discovery of the Solar System's ninth planet.

Pluto was a puzzler, however. An object six times Earth's mass was expected to show a disk when observed using large telescopes, but Pluto did not. Furthermore, the planet had a bizarre tilted orbit that partly overlapped that of Neptune.

As astronomers continued their observations of Pluto, they revised estimates of its size downward. By 1960, some astronomers thought that it was about the size of Earth; others thought it might be as small as Mercury. This only deepened the mystery surrounding the planet, for if it was to account for the observed discrepancies in Neptune's orbit, then it had to be several times as massive as Earth. Some astronomers proposed the existence of another, larger planet beyond Pluto. One scientist proposed a much more novel explanation.

Dr. Robert Forward, a physicist at Hughes Aircraft Company, drew attention to Pluto's unusual characteristics in an article he published in Missiles & Rockets magazine on 2 April 1962. He did not speculate about what those characteristics might mean. That task he handed off to author George Peterson Field.

Field was in fact Forward's pen name. Safely hidden from professional ridicule behind the protective cloak of his nom de plume, the newly minted Ph.D. physicist could freely speculate in a "science fact" article in the December 1962 issue of Galaxy science fiction magazine that Pluto was a gift from a "Galactic Federation."

He began by calculating that a body about the size of Mercury but with six times the mass of Earth would be so dense that it would have to be made of the collapsed matter found only in certain dwarf stars. Such an object could not exist naturally; unrestrained by the massive gravity of a dwarf star, it should have exploded long ago. Therefore, he asserted, Pluto must be artificial.

He suggested that Pluto was in fact a "gravity catapult." He wrote that "it would have to be whirling in space like a gigantic, fat smoke ring, constantly turning from inside out." A spacecraft that approached the ring's center moving in the direction of its spin would be dragged through "under terrific acceleration" and ejected from the other side.

If the acceleration the ultradense smoke ring gave the spacecraft were about 1000 times the acceleration Earth's gravity imparts to objects (that is, 1000 gravities), then the ring would boost the spacecraft to nearly the speed of light in about one minute. The passengers and crew would, however, feel nothing as their spacecraft accelerated, for the gravitational force from the roiling ring would act on every atom of their bodies and their ship uniformly. The ring would slow by a small amount as it accelerated the spacecraft.

He wrote that a "network of these devices in orbit around interesting stars" would provide "an advanced race" with an "energetically economical" means of star travel. The rings in the network would "cartwheel slowly" so that over time they would point at many possible destination stars.

A spacecraft a ring accelerated could, upon arriving at another star in the network, enter that star's ring moving against the ring's roiling motion. This would decelerate the spacecraft very rapidly and increase the ring's rate of motion by a tiny amount. In effect, the spacecraft would pay back the network for the acceleration it borrowed when it began its journey.

He ended his article by noting that such a device could be shot through space by a larger gravity catapult and braked "by pushing against a massive planet," such as Neptune. This, he added, might account for Pluto's odd orbit with respect to the eighth planet. He speculated that, at some time in the past, the Galactic Federation had noted the rise of humans and had launched Pluto toward Sol as "a coming out present."

Artist's impression of New Horizons at Pluto, 14 July 2015. Charon is visible at upper right. Details on Pluto and Charon are speculative. Image: NASA.

Forward's concept is so imaginative and appealing that it ought to be true. New data on Pluto soon ruled it out, however. In 1977, James Christy of the U.S. Naval Observatory Western Station, located just a few kilometers from Lowell Observatory in Flagstaff, Arizona, found Pluto's moon Charon. The discovery of a body orbiting Pluto enabled astronomers to calculate its mass accurately for the first time.

Pluto, it turned out, has only about one-quarter of 1% of Earth's mass. Subsequently, it was found to have a diameter of only about 2350 kilometers, making it only two-thirds as large as Earth's moon. Shortly after the turn of the 21st century, Pluto was found to have four more moons, all much smaller than Charon.

Though Pluto did not turn out to be a link in a galactic transportation network, it did turn out to be a link to something big. Pluto was the first member body of the Kuiper Belt to be found. The Kuiper Belt, a part of the Solar System long theorized but only confirmed beginning in 1992, is the "third realm" of bodies orbiting the Sun after the Sun-hugging realm of the rocky planets and the realm of the giant planets. It is far bigger than the first two realms combined.

As New Horizons closes in on Pluto, we know of more than 1000 bodies in trans-Neptunian space. Astronomers estimate that more than 100 times that number might exist. Assuming that New Horizons continues to operate as planned, mission planners expect to direct it past at least one more Kuiper Belt Object after the Pluto flyby.

If Pluto is so small that it cannot account for the discrepancies in Neptune's orbit, then what does? In August 1989, the Voyager 2 spacecraft flew past Neptune. By carefully tracking the robot spacecraft, celestial dynamicists refined their estimate of Neptune's mass. When they did, the observed discrepancies in its orbital motion vanished. There was thus never a need to find a Planet X. Error had led to coincidence, and the result was early knowledge of mysterious Pluto.

Source

"Pluto — the Gateway to the Stars," Robert L. Forward. Missiles and Rockets, 2 April 1962, pp. 26-28.

"Pluto, Doorway to the Stars," George Peterson Field, Galaxy Magazine, December 1962, pp. 78-82.

More Information

Galileo-style Uranus Tour (2003)

Pluto: An Alternate History