S-IVB/IU Applications: The LASS Proposal (1966)

Douglas Aircraft Company built the S-IVB stage and IBM built the Instrument Unit (IU) that rode atop it. In the image above, the S-IVB/IU combination for the Apollo 4 mission is hoisted in the Vertical Assembly Building at NASA Kennedy Space Center (KSC), Florida. The black ring at the top is the IU; the red object mostly hidden by the tapered interstage adapter at the bottom is the S-IVB's J-2 rocket engine bell in a red protective wrapping. The study described in this post drew to its conclusion as this, the first S-IVB/IU intended for flight, began pre-launch preparations at KSC. Apollo 4, the first flight test of the Saturn V, flew without a crew on 9 November 1967. The Apollo 4 S-IVB/IU performed flawlessly. Image credit: NASA.

Finding new roles for space hardware that exists or is under development is a common objective of spaceflight advance planners. They aim to accomplish new tasks in space while reducing development time and cost; if they work for a contractor and propose new roles for hardware that their company is on contract to produce, they might also hope to generate new contracts and new revenue. Advance planners employed by NASA may also seek to find new ways to exploit existing hardware; their objectives in doing so can often be complex. 

Many examples of proposals to repurpose space hardware can be cited. The reader may explore some of them by clicking on links in the "More Information" section at the bottom of this post. 

In this post we zero in on a proposal for repurposing two important elements of Apollo-era space hardware: the S-IVB rocket stage, which formed the second stage of the two-stage Saturn IB launch vehicle and the third stage of the three-stage Saturn V launcher, and the Instrument Unit (IU), the "electronic brain" of the Saturn IB and Saturn V, which rode into space bolted atop the S-IVB. The authors of this proposal were engineers at Douglas Aircraft Company, the prime contractor of the S-IVB, and International Business Machines (IBM), the prime contractor of the IU. 

Image credit: NASA.
Image credit: NASA.

The Douglas/IBM team performed its "Lunar Applications of a Spent S-IVB/IU Stage (LASS)" study using company funds between November 1965 and July 1966, shortly after the official start within NASA of the Apollo Applications Program (AAP) in August 1965. During AAP, the U.S. civilian space agency encouraged and invited proposals for new uses of hardware under development for the Apollo lunar program.

The S-IVB and IU were designed to reach Earth orbit during Apollo Earth-orbital missions and to leave Earth orbit with enough energy to fly past the Moon during Apollo lunar missions. This meant that, even without modifications, they would reach places in space where they might serve new useful purposes. As AAP gained steam in the 1965-1966 period, the S-IVB and IU thus became prime candidates for application to new missions throughout cislunar space and beyond.

The LASS proposal grew out of a 1964 plan to make use of the Saturn IB S-IVB stage in low-Earth orbit. The S-IVB, which included (from top to bottom) a large tank for liquid hydrogen (LH2) fuel, a smaller tank for liquid oxygen (LOX) oxidizer, and a single J-2 engine capable of generating about 200,000 pounds (890,000 newtons) of thrust, would typically reach Earth orbit with an Apollo Command and Service Module (CSM) spacecraft on top during Apollo Earth-orbital missions. The CSM would weigh about 40,000 pounds (18,145 kilograms).

The large enclosed volume of its tanks and the payload it could place into orbit made the S-IVB a natural candidate for exploitation as the basis for an Earth-orbital laboratory. In 1965-1966, the favored scheme was to launch a two-stage Saturn IB with a modified S-IVB second stage carrying a Spent-Stage Experiment Support Module (SSESM) in place of a CSM with a crew. At the time the Douglas/IBM team performed the LASS study, the first S-IVB/SSESM combination was scheduled to reach Earth orbit early in 1968 as part of the SA-209 AAP mission.

An S-IVB-derived Earth-orbital laboratory with an attached Spent-Stage Experiment Support Module (SSESM) and, at right, a docked, separately launched Apollo Command and Service Module (CSM). Image credit: NASA.

After reaching orbit, commands transmitted from the ground — or perhaps generated automatically by its attached IU — would cause the S-IVB to vent leftover propellants from its tanks. A second Saturn IB rocket would then launch a CSM with a crew of three. 

The astronauts would dock their CSM with the SSESM, which might contain equipment, life support consumables, and furnishings they could use to make the S-IVB LH2 tank into a habitable living and working space with 10,400-cubic-feet (295.5 cubic meters) of volume. Other plans for using of the S-IVB in Earth orbit saw the SSESM as the only pressurized volume; the LH2 tank would in that case provide an enclosed space for experiments performed in vacuum. The SSESM would include an airlock which space-suited astronauts could use to enter the LH2 tank.

The Douglas/IBM team called their proposed LASS program a "sequel" to the use of spent S-IVB stages in Earth orbit. The team anticipated that, after a development program spanning 45 months, the first automated LASS vehicle might deliver a 27,300-pound (12,380-kilogram) payload to the lunar surface and provide a "sheltered volume" on the Moon as early as the 1970-1971 period.

A LASS mission would begin with a Saturn V liftoff from a Launch Complex 39 pad at Kennedy Space Center, Florida. The rocket would comprise an unmodified S-IC first stage, an unmodified S-II second stage, and a modified S-IVB third stage — the LASS vehicle — with a payload on top under an aerodynamic nose cone. The Douglas/IBM team suggested that the 3200-pound (1450-kilogram) nose cone planned for Voyager automated Mars/Venus spacecraft launches might be repurposed for LASS launches.

Until the S-II stage shut down, LASS Saturn V ascent would closely resemble Apollo Saturn V ascent. In both cases, the S-II would separate from the spent S-IC stage two minutes and 41 seconds after liftoff at an altitude of 42 miles (68 kilometers) and ignite its five J-2 engines. The S-IVB or LASS vehicle would then separate from the S-II stage eight minutes and 40 seconds after liftoff at an altitude of about 109 miles (175 kilometers).

During Apollo missions, four forward-facing small retro-rocket motors on the tapered adapter linking the bottom of the 21.7-foot-diameter (6.6-meter-diameter) S-IVB with the top of the 33-foot-diameter (10-meter-diameter) S-II would fire immediately after S-II shutdown. This would slow the S-II slightly to facilitate S-IVB separation. The adapter, though considered part of the S-IVB, would remain attached to the S-II when the S-IVB separated. 

Small rocket engines on twin side-mounted Auxiliary Propulsion System (APS) pods would then fire to accelerate the S-IVB slightly. This would cause the weightless LH2 and LOX propellants within it to settle to the bottom of their tanks so that they could enter intakes leading to the S-IVB J-2 engine. The J-2 would then ignite to boost the S-IVB and its payload to low-Earth parking orbit. 

LASS vehicle launch configuration. Image credit: Douglas Aircraft Company/IBM.
Procedure for LASS vehicle landing leg deployment and separation from the Saturn V S-II stage. Image credit: Douglas Aircraft Company/IBM.
LASS vehicle engine and plumbing arrangement. Image credit: Douglas Aircraft Company/IBM.

LASS vehicle separation from the adapter linking it to the S-II stage would be more complicated. Four landing legs folded against the outside of the adapter under covers protecting them from aerodynamic heating during ascent would deploy, then a dozen forward-facing "ordinance thrusters" spaced 30° apart around top of the adapter would ignite to slow the S-II slightly to facilitate LASS vehicle separation.  

Replacing the four small retro-rockets on the Apollo Saturn V S-IVB/S-II adapter with 12 thrusters was necessary because the LASS vehicle included two RL-10 engines mounted on either side of its J-2 engine. Even with the RL-10 engine bells fully gimballed (pivoted) toward the J-2, LASS vehicle separation from the adapter using only the four retro-rockets would have been a risky business. Four thrusters would have meant less precision even if all worked as planned; in addition, the Douglas/IBM team estimated that if just one retro-rocket motor failed, collision between an RL-10 and the adapter was guaranteed.

The versatile RL-10 engine had been developed for the Centaur, the world's first LH2/LOX rocket stage. Combining throttleable RL-10 engines with Saturn hardware was nothing new when the Douglas/IBM team performed the LASS study; the Saturn I rocket, the first flightworthy member of the Saturn family, had mounted at the bottom of its S-IV second stage six RL-10s, each capable of producing 15,000 pounds (66,720 newtons) of thrust. 

First Saturn I launch: SA-1, 27 October 1961. Image credit: NASA.
Image credit: NASA.
Image credit: NASA.

Saturn I had been intended to launch astronauts into low-Earth orbit, but it was relegated to Apollo development flights without crews after NASA decided in 1962 that Saturn IB and Saturn V should become the Apollo launch vehicles. The last Saturn I flight, SA-10, launched a non-functional mass simulator ("boilerplate") Apollo CSM and the Pegasus III micrometeoroid detection satellite on 30 July 1965, a little more than three months before the LASS study commenced.

Use of the RL-10 as a LASS rocket engine was deemed necessary because the standard J-2 engine could not be throttled or gimballed enough to permit the LASS vehicle to land on the Moon. The Douglas/IBM team noted, however, that, if the proposed advanced J-2X engine were developed outside the LASS program — that is, without cost to the LASS development effort — then a single J-2X might replace the baseline J-2 engine and twin RL-10s. 

After successful LASS vehicle separation from the adapter and S-II, motors in its twin APS modules would fire to accelerate it slightly, causing the weightless propellants within it to settle to the bottom of their tanks. There they would enter intakes leading to the RL-10 and J-2 engines. 

The three engines would ignite to perform a single 8.5-minute Trans-Lunar Injection (TLI) burn that would expend 171,800 pounds (77,930 kilograms) of propellants to place the LASS vehicle on course for a 110-hour (4.5-day) voyage to the Moon. LASS vehicle mass would total 131,800 pounds (59,535 kilograms) at the end of the TLI burn. The LASS vehicle would then discard the aerodynamic nosecone covering its top-mounted payload.

The LASS TLI scheme was a significant departure from its Apollo counterpart. During Apollo lunar missions, the S-IVB J-2 would first burn for about 2.5 minutes, injecting it and the attached Apollo spacecraft into a 118-mile-high (190-kilometer-high) parking orbit about the Earth; then, about 2.5 hours after launch, it would burn again for about six minutes to depart parking orbit for the Moon. 

Loitering in parking orbit would permit a final checkout of Apollo spacecraft systems. Even more important, however, it would make available a daily launch window spanning several hours on each day of a monthly lunar launch window spanning several days. This flexibility would allow NASA to compensate for delays that might occur during the complex Saturn V pre-launch countdown.

The LASS vehicle's direct-ascent lunar mission profile would, by contrast, permit only a very brief launch window (in theory, it would be instantaneous). Direct-ascent, while worrisome from the standpoint of launching to any given lunar landing site during any given launch opportunity, would reduce the quantity of propellants expended to launch the LASS vehicle to the Moon. This would make available more propellants for two planned course corrections and for the all-important lunar landing burn.

Following the TLI burn, thrusters in the APS modules, governed by navigational electronics in the IU, would maneuver the LASS vehicle so that its three engines and the bottom of its LOX tank pointed at the Sun. This orientation would help to prevent the LASS vehicle's LH2 fuel from causing its LOX oxidizer to freeze. The RL-10 engines, meanwhile, would cyclically vent excess gaseous hydrogen that built up in the LH2 tank.

Technicians assemble an Instrument Unit (IU) at the IBM plant in Huntsville, Alabama. In their study, the Douglas/IBM team assumed that the interior walls and portions of the central area of the IU might be used to house new LASS vehicle systems. Image credit: NASA.
The LASS vehicle just before touchdown on the lunar surface. The illustration displays the position of the IU and, above it, the tapered LASS vehicle payload volume. Image credit: Douglas Aircraft Company/IBM.

The Douglas/IBM team considered the IU to be a candidate location for many new LASS vehicle systems. New navigation and communications systems, for example, would include long-range and short-range lunar landing radars, an altimeter, sensors for tracking the Sun, Earth, stars, and the lunar horizon, a data transmission system including a steerable high-gain dish antenna mounted on the outside of the IU, and a system for homing in on a pre-landed radio beacon at the target landing site on the Moon.  

Though the IU would include new navigational systems, it would still rely heavily on navigational data transmitted from Earth. The Douglas/IBM team expected that reliance on Earth-provided data — which would be generated using inputs from both Earth-based tracking and IU sensors — would ensure that the LASS vehicle could navigate successfully using 1966 state-of-the-art technology. Avoidance of new navigational systems would help to control LASS vehicle development cost.

The IU would also offer a candidate location for electricity-generating systems. These would include three Apollo CSM-type fuel cells, their thermal radiator, and tanks containing their LH2/LOX reactants, as well as rechargeable silver-zinc batteries for handling peak electrical demands during course corrections and the lunar landing burn. The fuel cells would provide three kilowatts of power continuously for the duration of the 110-hour LASS vehicle flight; the batteries would support peak loads of up to 6.76 kilowatts. 

Between 10 and 20 hours after launch, the LASS vehicle would perform its first course correction maneuver. The IU would orient the LASS vehicle for the burn using the APS thrusters, then would pressurize the LH2 tank and J-2 engine using helium drawn from spherical "bottles" mounted on the inner walls of the LH2 tank and on the thrust structure supporting the J-2 and RL-10 engines. 

The RL-10s, which could be ignited without propellant settling, would burn in "10% idle mode" to settle propellants so that they could reach the J-2 engine, then would throttle up as the J-2 ignited. After the three engines fired for a predetermined period of time, they would shut down and the IU would orient the LASS vehicle so that they would again point toward the Sun. If data supplied from Earth indicated that it was necessary, a second course correction would take place between 60 and 100 hours into the flight.

Unlike the Apollo CSM and LM spacecraft, the LASS vehicle would not inject into lunar orbit before descent to its target landing site. Instead, about 15,000 miles (24,140 kilometers) from the Moon and roughly 107 hours after liftoff, the Terminal Landing Phase (TLP) would commence. The IU would reorient the LASS vehicle so that its engines and four landing leg footpads pointed toward the Moon. At TLP start, LASS vehicle mass would total 117,500 pounds (53,300 kilograms).

About two hours later, at an altitude of about 450 miles above the Moon, the lunar horizon sensor would confirm LASS vehicle orientation. At an altitude of 350 miles, the IU would lock onto the signal from the pre-landed beacon at the landing site. The IU computer would begin performing TLP tracking calculations once per second. 

The RL-10 and J-2 engines would ignite to begin TLP Phase I braking at an altitude of 350,000 feet (160,680 meters). At 40,000 feet (12,190 meters), the altimeter would begin to supply data to the IU computer, supplementing beacon tracking data. 

TLP Phase II braking would begin with J-2 shutdown at 25,000 feet (7620 meters). At 10,000 feet (3050 meters), the IU would cease homing on the beacon. The IU computer would then very sensibly seek, as the Douglas/IBM team put it, to "drive all velocities relative to the surface to zero."

LASS vehicle landing legs and footpads. Image credit: Douglas Aircraft Company/IBM.

The IU would throttle the RL-10 engines to maintain a vertical descent velocity of 10 feet (three meters) per second and a lateral velocity of less than three feet (one meter) per second. When the IU-mounted short-range landing radar indicated an altitude of 70 feet (21.3 meters) above the Moon, the LASS vehicle's footpads would be about 10 feet (three meters) from the surface. The IU would then shut down the RL-10s and the LASS vehicle would drop the remaining distance. 

The Douglas/IBM team judged that their TLP system could enable a touchdown within 500 feet (150 meters) of the pre-landed beacon. LASS vehicle mass at touchdown would total 63,580 pounds (28,840 kilograms). Of this, payload above the IU would total up to 27,300 pounds (12,380 kilograms). 

Immediately after touchdown, the IU would command the LASS vehicle to "passivate" itself. The Douglas/IBM team did not describe the passivation process in any detail, though its aim would be to evacuate vessels containing liquids and gases that might freeze, leak, or over-pressurize and burst their containers. For example, about 2000 pounds (910 kilograms) of leftover LH2 and LOX propellants in the LASS vehicle tanks would be vented overboard. Gases and liquids in the payload would, of course, be immune from passivation.

After an unspecified period of time, astronauts would land near the LASS vehicle in an Apollo LM. The Douglas/IBM team provided few details about how the crew would interact with the LASS vehicle. They offered only a few vague suggestions concerning, for example, how astronauts in bulky space suits might ascend the approximately 60 feet (18.3 meters) to the top of the LASS vehicle to reach the payload. Neither did they describe how payload items would be moved from the top of the LASS vehicle to the surface, though they suggested that unspecified "cargo & handling equipment" with a mass of 3100 pounds (1400 kilograms) would be available. These and other mysteries would no doubt have been addressed if NASA had opted to fund additional LASS studies.

The Douglas/IBM engineers did, however, define five typical LASS payload configurations and mission durations. All would feature lunar exploration hardware under consideration in 1966 for AAP lunar missions and would see IU navigational and communications electronics serve double-duty as experiment data support equipment.

Configuration 1 was most in keeping with the role of the LASS vehicle as a sequel to an S-IVB-derived laboratory in low-Earth orbit. The LASS vehicle's LH2 tank would be lined with 3940 pounds (1785 kilograms) of micrometeoroid shielding and thermal insulation before launch from Earth; this weight would be subtracted from the weight available for payload above the IU. 

About 7700 pounds (3490 kilograms) of the payload above the IU would take the form of a two-man shelter similar to the SSESM proposed for the Earth-orbiting S-IVB laboratory. Life support gases and liquids and other expendables would account for 4500 pounds (2040 kilograms) of the payload. Experiment apparatus with a total weight of 500 pounds (227 kilograms), a 1000-pound (454-kilogram) unpressurized Lunar Scientific Survey Module (LSSM) rover, and a one-or-two-person Lunar Flying Unit (LFU) of unspecified weight would make up the balance of the payload.

LASS vehicle candidate lunar surface payload: Lunar Scientific Survey Module (LSSM) rover. Image credit: NASA.
LASS vehicle candidate lunar surface payload: Lunar Flying Unit. Image credit; Bell Aerospace.

Configuration 1 would see the two astronauts lower themselves into the LASS vehicle LH2 tank by unspecified means through an airlock in the shelter. The LH2 tank would then serve as either a laboratory or an emergency shelter. The crew would live in the LASS vehicle for up to 14 days before they reactivated their LM and returned to the Apollo CSM waiting in lunar orbit.

The other four LASS payload configurations would not make use of the LH2 tank, so the weight of the shielding and insulation surrounding it in Configuration 1 could be applied to payload above the IU. Configuration 2, with a 30-day lunar surface stay time, would include a 13,000-pound (5900-kilogram) four-man shelter, a 3800-pound (1725-kilogram) small (though possibly pressurized) rover, 4500 pounds (2040 kilograms) of science equipment, and 5700 pounds (2585 kilograms) of expendables. The Douglas/IBM team did not explain how four astronauts could reach the LASS vehicle on the Moon using the three-man CSM and two-man LM. 

Configuration 3 would include a four-man shelter, an LSSM, science equipment, and 8500 pounds (3855 kilograms) of expendables. The four-person crew would remain on the Moon for 59 days. Configuration 4 would include a two-person shelter, a small rover, scientific equipment, and 11,000 pounds (4990 kilograms) of expendables. The crew would evenly divide their time during their 120-day lunar surface stay between the shelter and the small rover. Configuration 5 would include a two-person shelter, an LSSM, scientific equipment, and 13,800 pounds (6260 kilograms) of expendables. The crew would evenly divide their time during their 195-day stay between the shelter and the LSSM. 

The Douglas/IBM team suggested that the astronauts might tip the roughly 60,000-pound (27,215-kilogram) LASS vehicle on its side to place its payload above the IU — which in this case would not include a shelter — close to the lunar surface. They did not, however, explain how the astronauts might accomplish this feat. They suggested that the crew could live inside their LM while they unloaded equipment from the tipped LASS vehicle and converted its LH2 tank into a shelter. 

A LASS vehicle with more extensive modifications — for example, a large rectangular hole cut into its LH2 tank for mounting a telescope — might be tipped on its side and converted into a lunar surface astronomical observatory. Ultimately, multiple upright and tipped LASS vehicles might be dragged together to form a "LASS Modular Lunar Base." The Douglas/IBM engineers ended their report by declaring that "LASS is envisioned to be the vehicle to support all lunar surface programs." 

During the 1960s, Douglas, IBM, and other contractors studied other new roles for the S-IVB and IU. These included a lunar-orbital lab, a testbed for reusable single-stage-to-orbit vehicles, a communications relay supporting missions to the Moon's farside hemisphere, a delivery vehicle for multiple automated lunar landers based on the Apollo LM descent stage, a testbed for interplanetary heat shield tests, and an interplanetary booster for automated and piloted spacecraft. Some of these are described in the "More Information" section below. Others will be described in future posts.

Sources

"NASA Launch Vehicles," Aviation Week & Space Technology, 2 July 1962, p. 91.

"Rendezvous to Slash Apollo Target Time," Aviation Week & Space Technology, 2 July 1962, pp. 106-111.

"Marshall Supervises Booster Development," Aviation Week & Space Technology, 2 July 1962, pp. 113-125.

Lunar Orbit Rendezvous — News Conference on Apollo Plans at NASA Headquarters on July 11, 1962, News Release and Press Conference Transcript, NASA, 1962.

Lunar Applications of a Spent S-IVB/IU Stage (LASS), presentation by Douglas Aircraft Company Missile & Space Systems Division and International Business Machines Federal Systems Division, September 1966.

"NASA Adapting S-4B for Space Station," W. Normyle, Aviation Week & Space Technology, 5 September 1966, p. 34.

"Manned Lunar Program Options Mission Modes," TM-67-1012-5, C. Bendersky & D. R. Valley, Bellcomm, Inc., 5 May 1967, pp. 9-10.

"Lunar Applications of a Spent S-IVB/IU Stage (LASS)," Douglas Paper No. 4256, L. O. Schulte & D. E. Davin, Douglas Missile & Space Systems Division; paper presented at the American Institute of Aeronautics and Astronautics Fourth Annual Meeting and Technical Display in Anaheim, California, 23-27 October 1967.

Stages to Saturn: A Technological History of the Apollo/Saturn, NASA SP-4206, Roger Bilstein, 1980, pp. 58-85, 129-153, 157-190, 241-257, 323-329, 336-345, 414-415.

More Information

One-Man Space Station (1960)

Space Station Gemini (1962)

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

Re-Purposing Mercury: Recoverable Space Observatory (1964)

"Still Under Active Consideration": Five Proposed Earth-Orbital Apollo Missions for the 1970s (1971)

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

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

Relighting the FIRE: A 1966 Proposal for Piloted Interplanetary Mission Reentry Tests

NASA's Planetary Joint Action Group Piloted Mars Flyby Study (1966)

"Without Hiatus": The Apollo Applications Program in June 1966

The First Voyager (1967)

Reusable One-stage Orbital Space Truck (ROOST) (1962)

A recovered ROOST booster is towed back to its seaside home base for refurbishment and relaunch. The recovery fleet and cable arrangements in this painting differ from those described in the December 1962 primary source report for this post. Image credit: Don Charles/Douglas Aircraft Company via San Diego Air & Space Museum.

Douglas Aircraft Company's Reusable One-stage Orbital Space Truck (ROOST) study served multiple purposes. On the one hand, it sought to describe in considerable detail a novel single-stage reusable system for transporting cargo and crews to and from low-Earth orbit that was technically feasible within the bounds of projected mid-1960s technology. On the other, it explored through an attempt at rigorous cost analysis the difficult question of whether a relatively simple reusable spaceflight system could be operated economically. As the company's December 1962 study report phrased it: "Does it really pay to recover boosters?" 

The lead author of the ROOST study, which was performed using company funds (that is, not on contract to NASA or any other government entity), was Philip Bono. Born in 1921 in Brooklyn, New York, he earned a Bachelor's of Engineering degree from the University of Southern California in 1947. He lived in the Los Angeles area for most of his life.

In the 1940s and 1950s Bono worked in succession for North American Aviation, Douglas Aircraft Company, Northrop Corporation, and Boeing Airplane Company. While at Boeing in 1960 he proposed a novel plan for a piloted Mars mission spacecraft based on the company's X-20A Dyna-Soar orbital spaceplane design (see "More Information" below). Shortly thereafter, he transferred back to Douglas, where he became Chief Advanced Projects Engineer in the company's Missile & Space Systems Division. Beginning with ROOST, Bono became widely identified as the champion of wingless, reusable, single-stage-to-orbit launch vehicles. 

Bono and his co-authors, F. Bergonz and John Hayes, envisioned a ROOST booster standing more than 273 feet (83.2 meters) tall with a maximum diameter of 62 feet (18.9 meters). The single-stage rocket would weigh 9.6 million pounds (4.4 million kilograms) standing on the launch pad just before liftoff, or about 3.4 million pounds (1.5 million kilograms) more than the three-stage, 363-foot-tall (110.6-meter-tall), 33-foot-diameter (10-meter-diameter) Apollo Saturn V Moon rocket. It would be capable of delivering 320,000 pounds (145,150 kilograms) of payload to 300-nautical-mile (555.6-kilometer) circular Earth orbit.

The Bono-led Douglas team declared that "the size of the ROOST vehicle precludes all modes of transport except water." Surface ships would thus deliver ROOST booster subassemblies to a seaside assembly, launch, and refurbishment facility, the home base for ROOST research & development and planned operational flights in a program spanning 14 years.

The subassemblies would comprise the flared 41-foot-tall (12.5-meter-tall) skirt forming the booster's base, 10 cylindrical 50-foot-diameter (15.2-meter-diameter) tank sections, and a 35-foot-tall (10.7-meter-tall) tapering transition section forming its top. They would arrive at a large sheltered receiving dock opening on the ocean and linked via a main canal to an assembly building made up of two A-frame bays 400 feet (122 meters) tall. In the assembly building the subassemblies, along with a payload, would be stacked vertically and joined together atop a square specialized barge that would serve double duty as a launch pad. 

The main canal would lead past "parking areas" for barges hauling heavily insulated tanks containing cryogenic liquid hydrogen (LH2) and liquid oxygen (LOX) rocket propellants. It would then branch into three shorter canals, each ending at a launch complex. 

Following assembly, the new ROOST booster on its barge/launch pad would be moved by conventional tugboats to a launch complex. Each complex would include a pair of large swinging lock doors, a water pumping station, and a basin section containing sturdy concrete piers and two rocket engine exhaust deflectors.

Before the ROOST booster arrived, the launch complex basin would be flooded with water and the lock doors opened. After the barge/launch pad holding the ROOST booster was positioned floating above the piers, the lock doors would be closed and the water pumped out of the basin, allowing it to settle onto the piers to assume its role as launch pad. 

The ROOST booster would be positioned in the assembly building atop a hole at the center of the barge/launch pad. The hole would permit exhaust from the booster's 12 main engines, each capable of producing a million pounds (454,000 kilograms) of thrust at sea level, to reach the twin launch complex exhaust deflectors, which would connect with concrete-walled vent tunnels. 

The parking areas for the propellant barges would adjoin pumping stations beside the main canal. As the time approached for prelaunch checkout and launch, the pumping stations would begin filling the LH2 and LOX tanks inside the ROOST booster. The dome-shaped bottom of the tank for dense LOX would protrude into the booster's skirt section; the dome-shaped top of the longer cylindrical LH2 tank would protrude into its tapered transition section.

The pumping stations would transfer the contents of 14 500,000-gallon (1.89-million-liter) barge-mounted storage tanks, each 25 feet (7.6 meters) in diameter and 185 feet (56.4 meters) long, into the ROOST booster. Bono and his co-authors explained that this quantity — a total of about seven million gallons (26.5-million liters) — would be sufficient to fill the LH2 tank three times and the LOX tank twice during each "shot" attempt. The first load of LH2 would be used for chill-down, the second for flight, and the third to keep the LH2 tank topped off during a possible launch hold lasting up to 12 hours. 

Cutaway drawing of the twin A-frame bays of the ROOST assembly building. Two transport barge/launch pads are visible in the canals leading out of the assembly bays at lower center and lower right. In this illustration from the December 1962 ROOST report the barge/pads appear rectangular, not square, and do not include central holes. Image credit: Douglas Aircraft Company.
Canal section leading to ROOST booster launch complex. A = water-filled canal; B = barges — pushed by conventional towboats —  each containing a super-insulated tank containing liquid hydrogen or liquid oxygen; C = pumping station for liquid hydrogen; D = pumping station for liquid oxygen; E = booster rocket engine exhaust vents; F = transport barge/launch pad with ROOST booster in cargo launch configuration, hold-down fixtures, and servicing gantry; G = canal lock doors for closing off launch complex launch basin; H = launch complex launch basin. Image credit: Douglas Aircraft Company/DSFPortree.
ROOST launch complex cutaway drawing. A = water-filled canal leading to launch basin; B = canal lock doors for sealing off launch basin; C = pumping station for removing water from launch basin when lock doors are closed; D = launch basin; E = concrete launch basin wall; F = transport barge/launch pad with central hole, hold-down fixtures, and servicing gantry; G = concrete pier for supporting transport barge/launch pad (one of four); H = booster rocket engine exhaust vent (one of two); I = ROOST booster in cargo launch configuration. The cylindrical part of the ROOST booster base is not depicted. Image credit: Douglas Aircraft Company/DSFPortree. 

The ROOST booster would expend a total of 8,574,000 pounds (3,889,000 kilograms) of propellants during its 292-second (nearly five-minute) climb to orbit. As the countdown reached zero, the 12 engines would ignite simultaneously. There would follow a brief hold-down period during which engine performance would be checked. If any of the main engines did not function as expected during checkout, all would be turned off. If all 12 engines functioned as planned, however, the hold-down fixtures would be released and the ROOST booster would thunder off the pad.

After a vertical climb lasting 14 seconds, the ROOST booster would gimbal (pivot) its engines by up to 6° to pitch eastward toward the sea. It would encounter maximum dynamic pressure at an altitude of 40,500 feet. Acceleration would increase as the single-stage vehicle expended its propellants, reaching six times Earth's surface gravity (6 Gs) 216 seconds after liftoff. At that point, half of the main engines would shut down to maintain acceleration within tolerable limits for any astronauts atop the booster. 

During crew launches a launch escape tower akin to the one atop the Mercury capsule would stand by until after orbit injection to pull the ROOST crew capsule free in the event of ROOST booster malfunction. The presence of astronauts would shape the normal ROOST booster ascent trajectory; launch escape followed by ballistic reentry and ocean splashdown would remain possible until late in the climb to orbit. Bono and his colleagues were focused on the booster, however, so provided little information on the design of the escape system, crew spacecraft, or, indeed, any ROOST payload/crew system. 

Six main engines would continue to operate for a further 76 seconds, during which time acceleration would top out at 6.7 Gs. Shutdown would occur at an altitude of 256,000 feet (78,029 meters) with the ROOST booster traveling at 26,300 feet per second (8016 meters per second), a velocity sufficient to enable it to coast to apogee at its 300-nautical-mile (555.6-kilometer) operational altitude in about 30 minutes. During piloted ROOST flights the launch escape tower would separate from the crew spacecraft during coast.

At main engine shutdown the ROOST booster and payload would have a mass of 1,026,000 pounds (465,486 kilograms). The main engines would not operate again until the next time the ROOST booster lifted off from its seaside base. 

Bono and his co-authors believed that the main engines were a key factor in the ROOST booster's bid for economical reusability. They cited the opinion of an unnamed rocket engine manufacturer when they stated that replacing the nickel steel cooling tubes typical in rocket engine bells with stainless steel cooling tubes would by itself stretch ROOST booster main engine life to 4000 seconds. They cited the main engine burn times — six would operate for 216 seconds per flight and six for 292 seconds — when they estimated that each main engine could perform between 13 and 18 flights before a major overhaul would become necessary. A major overhaul would cost between 40% and 50% of the original cost of the engine.

The ROOST booster would include four secondary engine "quads" near the broad bottom end of the tapered transition section. Bono and his co-authors called these "cruciform engines." During ascent they would be shielded from aerodynamic heating by ejectable covers. 

As the terms "quad" and "cruciform" imply, the four 10,000-pound-thrust (4536-kilogram-thrust) engines making up each quad would be arranged to resemble a "+" sign. The engines would burn storable hypergolic (ignite-on-contact) hydrazine fuel and nitrogen tetroxide oxidizer drawn from eight pressurized tanks in the transition section. Half of the 16 secondary engines could fail without degrading performance during the seven sequential maneuvers they would need to carry out during each ROOST flight.

The secondary engines would first be used to provide attitude control during coast to apogee, then the four aft-facing secondary engines would ignite at apogee and burn for eight minutes to circularize the ROOST booster's orbit. At the end of the circularization burn the ROOST booster and payload would weigh 956,000 pounds (433,634 kilograms).

ROOST booster launch. The canal and launch complex depicted in this painting are somewhat different from those depicted in the December 1962 ROOST report. See next image for explanation. Image credit: Douglas Aircraft Company via San Diego Air & Space Museum. 
Key to ROOST booster launch painting. A = crew vehicle with launch escape tower; B = tapering transition section with secondary propulsion system quads under aerodynamic shields; C = flaring base section with cylindrical housing for main engines and upper part of drag cone; D = transport barge/launch pad with servicing gantry; E = launch basin; F = rocket engine exhaust vent (1 of 2); G = swinging canal lock doors for sealing off launch basin (2); H = water-filled canal leading to launch basin; I = pumping station for removing water from launch basin when canal lock doors are closed; J = pumping station for liquid oxygen; K = barge carrying super-insulated tank containing liquid oxygen; L = high-pressure gas (helium and oxygen) tanks with adjacent railroad tank cars; M = receiving dock. Image credit: Douglas Aircraft Company/DSFPortree via San Diego Air & Space Museum.
Cutaway of ROOST booster in Earth orbit prior to payload separation. See next image for explanation. Image credit: Robert S. Wallace/Douglas Aircraft Company via San Diego Air & Space Museum.
Key to cutaway painting of ROOST booster in Earth orbit prior to payload separation. A = crew vehicle with launch escape tower; B = secondary propulsion system engine quad (one of four); C = interior of tapering transition section with pressurized hypergolic propellant tanks and dome-shaped top of LH2 propellant tank; D = LH2 propellant tank; E = cluster of four helium tanks (one of two) within LH2 propellant tank; F = torus-shaped "recovery bag" LH2 tank within main LH2 tank; G = main LOX propellant tank; H = base section with cylindrical housing for main engines and upper part of drag cone; I = main engine (one of 12); J = canister containing lower part of drag cone. Image credit: Robert S. Wallace/Douglas Aircraft Company/DSFPortree via San Diego Air & Space Museum.

The four forward facing secondary engines would then ignite to brake the booster slightly to facilitate separation of the 360,000-pound (163,290-kilogram) payload and to settle 62,000 pounds (28,123 kilograms) of trapped LOX in the main propulsion system so that it could be vented overboard. The ROOST booster would then be permitted to tumble in orbit until time came to collect a free-flying 30,000-pound (13,608-kilogram) payload for return to Earth. 

The Earth-return payload might take the form of a 12-man capsule with an emergency escape system. As it approached, the secondary engines would stabilize the ROOST booster to permit it to safely link up with the transition section, replacing the payload delivered to orbit. 

From the beginning of its orbital tumble until after rendezvous and docking with the Earth-return payload, the ROOST booster would gradually deploy and inflate its 107,000-pound (48,534-kilogram) reentry and recovery system. This would take the form of a two-part "inflatable blunt body drag cone" measuring 226 feet (68.9 meters) tall by 325 feet across when fully inflated. 

The upper part of the drag cone would be made of relative fragile materials — dacron sheets bonded together with silicone sealant. A pair of load-bearing membranes would support the ROOST booster's weight during reentry, while a torus-shaped structure with an inflated volume of eight million cubic feet (226,535 cubic meters) surrounding the middle portion of the ROOST booster would enable the drag cone to maintain its overall shape. 

Bono and his co-authors noted that the quantity of gas in the torus would be roughly equivalent to that in the twin helium-filled Akron-class dirigible airships operated as flying aircraft carriers by the U.S. Navy in the 1930s. The Akron and the Macon each measured about 785 feet (239 meters) long. The comparison was perhaps unfortunate because neither airship lasted long — the Akron, launched in 1931, crashed with the loss of most of its crew in 1933 off the coast of New Jersey, and the Macon, completed in 1931 and first flown in 1933, was damaged in a storm and lost off the California coast in 1935.

The lower part of the drag cone, which would become its forward-facing "nose" during reentry (and thus would be exposed to the greatest aerodynamic heating) would comprise Rene 41 or stainless steel wire cloth coated with silicone sealant. It would be made up of "airmat" cells, so would tend to hold its shape even when not filled with gas. 

Two arcuate sections of the lower skirt surrounding the main engines would detach, exposing the carefully packed upper part of the drag cone. Thermal radiation from the Sun and Earth would heat LH2 left over in the LH2 propellant tank after main engine operation, causing it to turn to gas. In a normal booster, if responsible practices were observed, gaseous hydrogen would be vented overboard to prevent the tank from overpressurizing and bursting explosively, but in the reusable ROOST booster the gas would be piped into the upper part of the drag cone to slowly inflate it ahead of reentry. Gradual inflation would, the Douglas engineers explained, help to prevent the upper drag cone from overinflating and bursting. 

The lower part of the drag cone, meanwhile, would deploy from a cylindrical canister surrounded by the 12 main engines. Helium gas drawn from eight spherical "bottles" mounted within the LH2 propellant tank would be used to inflate the lower drag cone. 

ROOST booster in Earth orbit at start of inflatable drag cone deployment. The lower and upper parts of the drag cone can be discerned (the upper part is torus-shaped and orange; the lower part, to the left of the upper part, appears silvery). Visible at left are the two arcuate sections of the cylindrical lower skirt which housed the main engines and, surrounding them, the stowed upper part of the inflatable drag cone. Also visible at left is the disc-shaped cover of the cylindrical canister that held the stowed lower part of the drag cone. At center right eight red hypergolic propellant tanks can be seen within the tapering transition section through the opening left by separation of the payload the ROOST booster delivered to orbit. Image credit: Douglas Aircraft Company via San Diego Air & Space Museum. 

Cutaway painting of ROOST booster with Earth-return payload and fully deployed inflatable drag cone at start of reentry. See next illustration for explanation. Image credit: Robert S. Wallace/Douglas Aircraft Company via San Diego Air & Space Museum.
Key to cutaway painting of ROOST booster with Earth-return payload and fully deployed inflatable drag cone at start of reentry. A = Earth-return payload; B = secondary propulsion system engine quad (one of four); C = tank section encapsulated by two-part drag cone; D = torus-shaped upper drag cone inflated section; E = lower drag cone showing airmat cells. Image credit: Robert S. Wallace/Douglas Aircraft Company/DSFPortree via San Diego Air & Space Museum.
Cross section of ROOST booster with fully deployed drag cone and selected dimensions. A = Earth-return payload; B = secondary propulsion system engine quad (1 of 4); C = LH2 propellant tank; D = LOX propellant tank; E = base section. During reentry the center of gravity is located in the upper third of the LOX tank. Image credit: Douglas Aircraft Company/DSFPortree.

Bono and his co-authors explained that the ROOST booster would overfly its seaside base about every 12 hours. They thus designed the booster for an orbital lifetime of 24 hours to provide two opportunities for acceptable weather conditions in the recovery area, a 46-nautical-mile-diameter (85.2-kilometer-diameter) circular ocean zone centered about 50 nautical miles (92.6 kilometers) from the ROOST base receiving dock. Among other factors determining orbital lifetime was the damage expected to be caused over time by micrometeoroid impacts.

Earth-return would begin with an "orbit rejection" maneuver, which would see the four forward-facing secondary engines burn for nearly four minutes to reduce the ROOST booster's orbital velocity by 500 feet (152 meters) per second. During ROOST crew-return missions, astronauts on board would start and end the precise maneuver; during cargo missions, when no crew was on board, transmitted commands from a ground station would fill in. 

The secondary engines would then perform attitude control maneuvers so that by the end of a 30-minute coast period, at the start of atmosphere reentry at an altitude of 400,000 feet (122,000 meters), the ROOST booster would be oriented at an entry angle of 1.5°. This angle would minimize aerodynamic heating of the drag cone while enabling control sufficient to ensure landing in the designated landing zone. 

At an altitude of 235,000 feet (71,630 meters), 250 seconds after the start of reentry, the ROOST booster would experience its peak deceleration of 3.4 Gs. By then the temperature experienced by the lower part of the drag cone would be decreasing from a peak of 1520° F (827° C). Maximum deceleration of 6.75 Gs would occur 300 seconds after the start of reentry at an altitude of 204,000 feet (91,200 meters), by which point the ROOST booster would have slowed to a speed of Mach 11.8.

Bono and his co-authors aimed to make the inflated drag cone aerostatically buoyant, like an airship, before it reached the surface of the ocean. To accomplish this, starting at an altitude of 100,000 feet (30,480 meters) LOX from a special small "heater tank" inside the booster's LOX propellant tank and LH2 from a torus-shaped "recovery bag" tank inside the LH2 propellant tank would be fed into a combustion chamber and ignited, yielding hydrogen and steam. The hot combustion products would then be fed into the drag cone to raise its internal temperature, thus increasing its buoyancy. 

At an altitude of 2000 feet (610 meters) above the ocean, with upper drag cone internal temperature at 400° F (204° C), the ROOST booster would slow to a stop and the heated gas flow would end. The gas in the upper drag cone would then cool and the ROOST booster would begin a descent to the ocean surface lasting about 16 minutes, with a final speed at "splash down" of just 2.5 feet (0.76 meters) per second. The relatively stiff lower part of the drag cone and slow landing speed would prevent salt water from contacting the ROOST booster's solid structure (and, especially, its main engines), helping to ensure fast and cheap refurbishment ahead of its next flight.

During its slow final descent the ROOST booster would automatically deploy several sea anchors and tow cables. These would on contact with the water dissipate static charge built up during reentry and create drag, helping to prevent surface winds from pushing the floating booster away from the landing area. As it floated in the ocean swell the returned ROOST booster and payload would weigh 568,580 pounds (258,000 kilograms).

Meanwhile, a recovery force would move to intercept the returning ROOST booster. It would comprise a modified destroyer or destroyer escort ship with engines capable of generating 12,000 horsepower at its propeller shaft, a C-47 cargo airplane, and three H-21 helicopters. During night-time landings radar tracking and a radio beacon on the ROOST booster would guide the recovery force; during daylight landings, the helicopters would also patrol the landing zone and seek to spot the returning booster visually.

Sailors on the surface ship would take on board the tow cables and attach them to a powered winch. If astronauts were on board the ROOST booster, a helicopter would hover over the crew capsule and lower a retrieval basket to collect them for transfer to the surface ship. The sea anchors would then be collected and the surface ship would set out for the ROOST base receiving dock at a speed of 10 knots (assuming a 20-knot headwind) (see image at top of post). Depending on the touchdown point and the modest rate of surface drift expected, the tow-back distance might range between 27 and 73 nautical miles (50 and 135 kilometers). 

Upon arrival at the receiving dock, the tow cables would be transferred to a winch on a waiting barge/launch pad. A hose on the barge/launch pad would then be used to pump hot steam and hydrogen gas from a combustion unit into the upper part of the drag cone to restored its buoyancy. 

With the ROOST booster floating above the water, technicians would remove the lower part of the drag cone, attach a hose, and pump out the helium inside it for reuse. Removal of the lower drag cone would expose the booster's flared base and 12 main engines. 

The technicians would then attach the base of the hovering ROOST booster to the hold-down fixtures on the barge/launch pad, taking care to move slowly so as not to cause damage. After the booster was firmly bolted down, they would detach the upper part of the drag cone from the booster and allow it to rise above the payload at the top of the tapering transition section. Bono and his co-authors called this "'skyhook' buoyancy feature" a "fringe benefit" of their inflatable drag cone recovery system. 

Once the upper part of the drag cone was free of the booster, technicians would pull it down onto the barge/launch pad and attach hoses to remove its hydrogen and flush it with nitrogen. The barge/launch pad would then transfer the ROOST booster and its recovery system components down the main canal to the assembly building for refurbishment ahead of their next launch.

Though Bono and his co-authors stated that the ROOST booster was too large to be moved except on water, near the end of their report they proposed that, after operational reliability was demonstrated, ROOST booster assembly, launch, landing, and refurbishment at a land (most likely desert) base might become possible. This would, they wrote, make ROOST especially attractive "after our coastal [launch and splashdown] ranges have eventually become saturated" with rocket traffic.

They suggested as a possible land site the wide-open spaces of Edwards Air Force Base, north of Los Angeles. Polar launches from Edwards would overfly communities located between Los Angeles and San Bernardino, while launches to near-equatorial orbits would overfly the central California community of Barstow.

Bono and his co-authors then provided details of the 14-year ROOST program schedule as part of their attempt to estimate system reliability and manufacturing, operations, and refurbishment costs. They explained that four years would be spent designing, developing, and testing the ROOST booster, with the first booster arriving at the seaside launch base midway through the third year. Following assembly and transfer to the launch complex, a static engine test would occur. The ROOST booster would be held down while its main engines fired for some period of time.

The first research and development orbital test flight would take place midway through the fourth year. Assuming a successful first test flight, the flown booster would be refurbished and launched on a second test flight before the end of the year. If the first test flight ended in loss of the ROOST booster, a second booster would attempt a test flight by the end of the fourth year. Operational flights would then begin early in the fifth year and continue for a decade.

The overarching goal of the 10-year operational ROOST program would be to deliver 64 million pounds (29.03 million kilograms) of cargo to low-Earth orbit. Booster reliability would be an important factor in determining the number of flights required to achieve this and thus the flight rate and number of ROOST boosters required. Bono and his co-authors assumed an 80% reliability rate in the operational program's first year — that is, loss of one in five ROOST boosters launched — and a total of eight flights. 

This was an ambitious target; at the time the Douglas engineers prepared their report, U.S. boosters typically suffered much worse failure rates. The missile-derived Atlas, for example, had flown 12 times with seven failures, for a success rate of only 41.8%. The Douglas engineers noted that Atlas was basically a two-stage launch vehicle, and that five of its failures had been attributed to its second stage. They contended that their single-stage booster would be immune from many possible failure types, including (to cite the most obvious example) failure of the second stage to ignite. 

In the second year of the 10-year operational ROOST program, reliability would increase to 90%, where it would remain throughout the test of the program. Launch rate would climb to 12 flights per year. In its third year, the operational ROOST program would achieve its maximum launch rate of 24 flights per year. The ROOST program would need a total of 199 flights.

Taking into account these loss and launch rates and the total number of ROOST flights needed, Bono and his co-authors then calculated that the operational ROOST program would require a total of 27 ROOST boosters to achieve its 64-million-pound (29.03-million-kilogram) goal. Each booster would cost $39.1 million, for a total booster hardware cost of $1.056 billion. ROOST cost would total $2.989 billion over the course of the 14-year program.

The Douglas engineers then proposed "for comparison purposes" a hypothetical, conjectural expendable One-stage Orbital Space Truck (OOST) booster identical to the ROOST booster but without recovery systems. They assumed that recovery system weight saved could be applied to increase payload and that the OOST booster would be more reliable than the ROOST booster because it would not be subjected to the risks inherent in reentry, recovery, and refurbishment. 

They found that a total of 139 OOST flights — and thus 139 single-use OOST boosters — would be required. Each OOST booster would cost just $20.8 million and the reduced number of flights would mean that only two launch complexes would be necessary to carry out the OOST program, not three. 

A total of 139 expendable OOST boosters would, however, cost $2.895 billion — nearly three times as much as the 27 ROOST boosters. The savings generated by eliminating the third launch complex ($48 million) and all recovery and refurbishment operations ($64 million) would fall far short of justifying development of the OOST booster in place of the ROOST booster. Total OOST program cost over 14 years would reach $4.568 billion, or $1.673 billion more than the ROOST program. 

Bono and his co-authors asserted that their cost estimates fell within 10% of actual costs. How they could be certain of this was, however, not made clear. Their study was almost certainly too preliminary to support cost estimates of that degree of precision.

While novel and apparently promising, the ROOST proposal gained little traction. In part this was because Bono and his co-authors appear not to have spent much time promoting it. Bono would within a year move on to another type of wingless, reusable, single-stage launch vehicle — one without any inflatable parts. His Reusable Orbital Module (Booster and Utility Shuttle) (ROMBUS) system included many of the characteristics of systems he would promote throughout the remainder of his career. ROMBUS will be discussed in a future post.

Phillip Bono remained with Douglas (known as McDonnell Douglas after its 1967 merger from McDonnell Aircraft Corporation) until his retirement in 1988. He died in 1993, shortly before the company carried out an (ultimately abortive) series of non-orbital tests using subscale prototype Delta Clipper reusable single-stage-to-orbit vehicles.

Sources

An Integrated Systems Study for a Reusable One-Stage Orbital Space Truck (ROOST), P. Bono, F. Bergonz, and J. Hayes, Douglas Report SM-42597, Douglas Aircraft Company, Inc., Missile & Space Systems Division, December 1962.

"ROMBUS — An Integrated Systems Concept for a Reusable Orbital Module (Booster and Utility Shuttle)," Paper No. 63-271, P. Bono; paper presented at the American Institute of Aeronautics and Astronautics Summer Meeting in Los Angeles, California, 17-20 June 1963.

"Philip Bono, Reusable Rocket Booster's Designer, Dies at 72," G. Hernandez, Los Angeles Times, 27 May 1993 (https://www.latimes.com/archives/la-xpm-1993-05-27-me-40243-story.html — accessed 18 August 2022).

San Diego Air & Space Museum Image Collection (https://sandiegoairandspace.org/collection/image-collection — accessed 10 August 2022). 

More Information

Dyna-Soar's Martian Cousin (1960)

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

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

Integral Launch and Reentry Vehicle: Triamese (1968-1969)

A Robotic and Piloted Planetary Exploration Program for the 1970s and Early 1980s (1968)

Leaving home: Earth as viewed from Apollo 4 on 9 November 1967. Image credit: NASA.
It was the best of times. It was the worst of times. (With apologies to Charles Dickens.)

For NASA, the year 1967 began with the promise of a bold start for the Apollo Applications Program (AAP), the planned successor to the Apollo lunar program, which would see space station missions in low-Earth orbit and advanced lunar exploration missions. Top NASA officials briefed the press on their ambitious AAP plans on 26 January 1967 (see "More Information" below). 

Barely a day later, fire raged through the crew cabin of the Apollo 1 Command and Service Module (CSM) spacecraft during a test on the launch pad, killing astronauts Gus Grissom, Ed White, and Roger Chaffee. The resulting investigation angered Congress — NASA had failed to report persistent problems in its relations with North American Aviation (NAA), the CSM prime contractor. Affronted legislators, already eager to cut government expenditures because of the soaring cost of U.S. military involvement in Indochina, responded in August-September 1967 by slashing President Lyndon Baines Johnson's Fiscal Year (FY) 1968 NASA budget request by nearly half a billion dollars. 

The cuts mostly affected projects aimed at giving NASA a post-Apollo future; AAP, of course, but also the Voyager robotic Venus/Mars exploration program (see "More Information" below) and advance planning for piloted missions beyond the Moon, including piloted Mars/Venus flybys. Members of the NASA Office of Manned Space Flight (OMSF) Planetary Joint Action Group (JAG) had hoped that major funding for piloted flybys could begin in FY 1969, with the first in a series of piloted flybys — a Mars flyby with sample return — leaving Earth in late 1975 (see "More Information" below).

Even as OMSF had sought piloted flybys, the scientific community had continued its perennial quest for an expanded robotic program. In a February 1967 report to the Johnson White House, the President's Science Advisory Council (PSAC) disparaged piloted flybys and urged a 1970s program that would see robotic spacecraft begin a wide-ranging reconnaissance of the entire Solar System. Scientists were outraged when instead the FY 1968 budget cuts threatened to end U.S. robotic exploration entirely after the twin Mariner '69 Mars flybys.

In October and November 1967, NASA Administrator James Webb spoke out in favor of new robotic planetary missions in the 1970s. He urged members of Congress to take note of Soviet plans for robotic exploration beyond the Moon. Talks began with White House budget officials and Congressional leaders aimed at salvaging a 1970s planetary program from the wreckage of the FY 1968 budget process.

Meanwhile, in Florida, components of AS-501, the first flight-ready Saturn V rocket, came together with an Apollo CSM in the giant Vertical Assembly Building (VAB) at NASA Kennedy Space Center (KSC). Without the three-stage behemoth an Apollo Moon landing was impossible.  The testing and assembly process had begun months before the Apollo 1 fire with the aim of a launch in the first quarter of 1967, but preparation for the automated test mission — which NASA designated Apollo 4 — hit one snag after another. 

Following the fire, NASA subjected the CSM NAA had delivered to KSC for the Apollo 4 mission to enhanced scrutiny. The spacecraft, designated CSM-017, was found to contain more than 1400 wiring errors. Fixing them required months. Welding errors in the NAA-built Saturn V S-II second stage also needed correction. 

Troubled assembly: the Apollo 4 CSM and Saturn V rocket in the Vertical Assembly Building at NASA Kennedy Space Center, Florida. Image credit: NASA.
The giant rocket was at last rolled out to Launch Pad 39A on 26 August 1967, but its troubles were not over, for Apollo 4 was also a test of launch pad hardware and pre-launch procedures. As the launch team struggled to make pad and rocket function together, the press, the public, and the Congress became increasingly impatient.

Apollo 4 lifted off at last on 9 November 1967. Rocket, spacecraft, launch facilities, and world-wide tracking & communications network operated together almost flawlessly.

The Apollo 4 Saturn V and CSM climb toward orbit. Image credit: NASA.
About three hours after insertion into a 190-kilometer-high (118-mile-high) low-Earth orbit, the AS-501 Saturn V S-IVB third stage restarted to boost CSM-017 into an elliptical orbit. It was the first orbital restart of the stage, which would boost Apollo missions out of Earth orbit to the Moon. 

Near orbital apogee CSM-017 separated from the S-IVB. The spacecraft fired its Service Propulsion System (SPS) main engine to increase its altitude to 18,092 kilometers (11,242 miles), then fired it again for 4 minutes and 30 seconds to hurl itself at Earth at a lunar-return speed of 24,911 miles (40,090 kilometers) per hour. 

CSM-017 split into its component modules — Command Module (CM) and Service Module (SM) — then the former reoriented itself with its bowl-shaped heat shield forward so that it could withstand fiery atmosphere reentry. The SM burned up as planned. The CM's heat shield, meanwhile, reached a temperature of nearly 2760 C (5000° F). Crew cabin temperature did not exceed 21 C (70° F). Just eight and a half hours after liftoff, the Apollo 4 CM deployed three parachutes and lowered to a splashdown in the Pacific. 

The unmanned Apollo 4 Command Module (right) bobs in the Pacific Ocean near Hawaii at the end of its eight-and-a-half-hour test flight. One of its three main parachutes remains attached; it would be retrieved for analysis along with the spacecraft. Image credit: NASA.
The trade magazine Aviation Week & Space Technology reported that, ironically, on the very day of NASA's Apollo 4 triumph, NASA Marshall Space Flight Center (MSFC) in Huntsville, Alabama, had laid off workers as a result of the FY 1968 budget cuts. NASA MSFC was the home of the Saturn family of rockets. 

On 12 December 1967, a little more than a month after Apollo 4, President Lyndon Baines Johnson toured NASA's Michoud Assembly Facility near New Orleans, Louisiana, where Saturn rockets were assembled and tested. His visit was meant to reassure local and state officials and to raise worker morale. Whether he succeeded is open to interpretation. Standing before a partially complete Saturn V S-IC first stage, Johnson told the workers

. . .that man will make space his domain is inevitable. Whether America will lead mankind to that destiny does not depend on your ability, but depends on our vision, our willingness, and our national will and determination. This great pilgrimage of man — like all his adventures — costs money. Christopher Columbus spent more years trying to find money for his voyage than he spent discovering the New World. In the modern world, we can no longer depend on Queen Isabella pawning her jewels. We have to depend on taxes. We must have revenues that only Congress can grant. . . So we will advance in space to the extent that our people and their representatives are prepared for us to advance and are prepared to pay the cost of that advance. We may not always proceed at the pace we desire. I regret — I deeply regret — that there have been reductions and there will be more. There have been interruptions. . . But I do have faith and confidence in the American people.

This background may help to explain why two engineers at Bellcomm, NASA's Washington, DC-based advance planning contractor, responded as they did when NASA invited them in late November-early December 1967, to state their opinions on the course U.S. planetary exploration should take in the 1970s and early 1980s. In a report completed and distributed to relevant NASA facilities on 26 February 1968, J. P. Downs and W. B. Thompson were cautiously optimistic. 

Downs and Thompson explained that their report reflected "the authors' thinking at. . . [a] particular time" and that it was "a reflection of a long term point of view." They assumed that the deep FY 1968 budget cuts were a short-term, temporary setback, not a sign of a long-term trend. In fact, they anticipated an annual NASA budget of between $5 billion and $6 billion by FY 1971 or FY 1972, when, they expected, NASA would start development of a piloted planetary program.

At the same time, the Bellcomm engineers cautioned that "[a]s more information becomes available on technical details and resources, the program may change." They added, however, that "the rationale expressed. . . is expected to remain much as it is now."

Downs and Thompson described a NASA planetary program containing 21 missions to 11 Solar System bodies between the years 1969 and 1984. Missions would occur in three "branches." The first branch would comprise missions to Venus and Mars that would serve as precursors to at least three piloted Mars and Venus missions. Missions in the second branch would explore Mercury, Jupiter, and the other "major planets" (Saturn, Uranus, and Neptune), a task they called "the major challenge to the unmanned program." The third branch would include missions to explore two comets and two asteroids. 

Their program would begin with the twin Mariner '69 Mars flybys already on NASA's schedule and continue in 1970 with a Mariner Venus/Mercury dual flyby mission launched on an Atlas/Centaur rocket. The Atlas/Centaur was already in early 1968 the workhorse of the NASA robotic lunar and planetary program. 

The Venus/Mercury mission, which would form part of both the first and second of Downs and Thompson's three branches, would seek gaps in Venus's cloud cover in the hope of glimpsing its mysterious surface. In addition, as the spacecraft flew past the planet, it would transmit radio signals to Earth through the Venusian atmosphere in an attempt to chart its structure.

Mariner Mars '69 engineering model. Note the large steerable camera "pod" mounted below the hexagonal bus body, the high-gain dish antenna on top, and the four solar arrays. Image credit: NASA.

Space workhorse: an Atlas-Centaur rocket launches the Surveyor 1 lunar lander on 30 May 1966. Image credit: NASA.
During the flyby, Venus would give the spacecraft a gravity assist that would reduce by between 50% and 75% the amount of propulsive energy it would need to reach Mercury. Downs and Thompson explained that the innermost planet is, by dint of its proximity to the Sun, often lost in glare when viewed from Earth and hence mysterious; orbiting close to the Sun also means that its orbital speed is high, making it difficult for spacecraft to reach.

In 1971, NASA would launch on a Titan III-C rocket its first new-design Mars orbiter and surface probe. Downs and Thompson suggested that the new orbiter might be based on the Boeing Lunar Orbiter design. The Titan III-C, a U.S. Air Force rocket, was meant to replace the Saturn IB-Centaur rocket formerly emphasized in NASA planetary mission plans. Use of the Titan III-C in the Downs and Thompson program was a response to a statement by NASA Administrator James Webb that the Saturn IB would be phased out to save money. 

18 June 1965: the first Titan III-C rocket stands on the pad at Launch Complex 40, Cape Canaveral Air Force Station, Florida. Image credit: U.S. Air Force.

Boeing-built Lunar Orbiter spacecraft. Image credit: NASA.
The 159-kilogram (350-pound) battery-powered survivable surface impactor probe would include an atmosphere entry shell, a parachute, a protective impact shell carved from soft, lightweight balsa wood, and 13 pounds of science instruments. These might include a life detection device. Instruments on the entry shell would  chart atmospheric structure as it plummeted toward the surface after separation from the impactor. These data would enable engineers to design heavier, more sophisticated Mars landers. 

NASA would launch in 1972 its first new-design Venus orbiter and atmospheric probe on a Titan III-C. In addition to "a concentrated search over the entire planet for visible access to the surface," the orbiter would employ an imaging radar to chart surface topography. The probe would measure the thermodynamic properties of the atmosphere to enable design of meteorological balloon probes suited to Venusian conditions.

In 1973, NASA would ramp up the pace by launching on three Titan III-Cs a pair of Mars orbiter/impactor probe missions and a second Mariner-derived Venus/Mercury flyby spacecraft. The latter would resemble that launched in 1970 but would add a Venus survivable surface impactor probe. The prime objective of the Mars impactor probes would be to search for life. 

The 600-pound Venus impactor probe would attempt to return data on the planet's harsh surface conditions for at least an hour. The dense Venusian atmosphere would, Downs and Thompson wrote, enable a survivable landing without a parachute.

The following year, NASA would launch its first flyby mission to Jupiter on a Titan III-C augmented with a Centaur upper stage. Dubbed a "galactic Jupiter probe," it would be the first NASA spacecraft designed for an operational lifetime of up to 10 years. It would survey interplanetary particles and fields and aid future spacecraft designers by surveying the interplanetary meteoroid environment with particular emphasis on the Asteroid Belt between Mars and Jupiter. A Jupiter gravity-assist would make it the first spacecraft to escape the gravitational grip of the Sun.

NASA would ramp up the planetary exploration pace in 1975 by launching four rockets — probably Titan III-Cs with Centaur upper stages. An orbiter and surface probe would leave Earth for Mars. Two orbiters with impact lander probes would launch to Venus. The space agency would also launch a clone of the 1974 galactic Jupiter probe mission.

The year 1976 would see NASA's first mission to a comet. After launch on an Atlas/Centaur, a Mariner-derived spacecraft would race past Comet d'Arrest. Downs and Thompson explained that the small size of the comet nucleus and the rapid speed of the flyby would require NASA to develop a sophisticated new tracking system for its comet spacecraft cameras.

In 1977, the first Mariner-derived "Grand Tour" spacecraft would depart Earth on a Titan III-C/Centaur. A series of gravity-assist flybys would speed it across the outer Solar System, enabling it to explore all four planets beyond the Asteroid Belt in the space of a decade. That same year, NASA would launch on two Titan III-C/Centaur rockets a Mars orbiter with an impactor and a Venus orbiter with a pair of impactors. The Venus impactors might be targeted to land on high-elevation surface features; these might, Downs and Thompson suggested, have cooler temperatures than lower elevations, and thus be more likely to support life.

The year 1978 would see launch of NASA's first asteroid mission (a flyby of asteroid Icarus using a Mariner-derived spacecraft launched on a Atlas/Centaur) and the second "Grand Tour" mission (a clone of the 1977 mission). It would also see an significant shift in the character of the U.S. planetary program as astronauts joined the action. 

Thompson was a veteran of the NASA OMSF Planetary JAG piloted flyby studies. The NASA budget seemed unlikely to stretch far enough to support development in time to carry out the Planetary JAG's 1975 piloted Mars flyby mission, so the Bellcomm engineers opted instead to take advantage of an opportunity to launch a piloted Venus/Mars/Venus flyby mission in late 1978. 

The piloted flyby spacecraft and its Earth-orbit departure booster stack would be assembled in Earth orbit using components launched on two-stage Saturn V rockets. After leaving Earth orbit and discarding its boosters, it would follow a free-return heliocentric path that would end at Earth. Only minor course corrections would be required after Earth-orbit departure.

In 1979, the crew of the piloted flyby spacecraft would deploy automated meteorological balloons and impactor probes as they passed Venus for the first time and automated sample returners as they passed Mars. The balloons would drift the Venusian atmosphere for a long period. They would seek evidence of life in cool atmosphere layers. 

Astronauts would examine in a sealed lab the Mars dirt and air the sample returners launched to the flyby spacecraft to determine whether they could be safely returned to laboratories on Earth. The following year (1980) would see the mission carry out its second Venus flyby — a clone of the first — followed a few months later by a direct Earth-atmosphere reentry.

The years 1979 and 1980 would also see the last two Mariner-derived comet/asteroid flyby missions on the Downs and Thompson schedule. The first, the last mission launched on an Atlas/Centaur, would visit asteroid Eros, while the second, launched on a Titan III-C/Centaur, would race past Comet Encke.

A second piloted flyby mission would depart Earth in 1981. During its Venus flybys in that year and in 1983 it would deploy a pair of balloon-borne "several thousand pound" Buoyant Venus Stations of a type proposed by the Martin Company in 1967, as well as an unspecified number of long-duration Venus landers. All would look for life. The Mars flyby in 1982 would see more surface sample collection and observations tailored toward selecting sites for eventual piloted Mars landings.

Downs and Thompson expected that their 1984 piloted planetary mission, the last on their schedule, would probably take the form of a Venus orbiter. A piloted Venus mission would, they wrote, "serve to pace the development of a high energy space storable propulsion system." After proving that it could slow the piloted Venus spacecraft so that Venus's gravity could capture it into orbit and accelerate it out of Venus orbit back toward Earth, the compact, powerful, long-lived rocket stage would propel piloted Mars orbiter and landing missions and boost out of Earth orbit large new-design robotic outer planet and "deep space" spacecraft.

The Bellcomm engineers' report landed on desks across NASA in late February. Their timing could have been better — barely a month ahead of its distribution North Vietnam attacked South Vietnam on the eve of Tet, the Chinese New Year, leading to greatly expanded U.S. involvement in the Vietnam War. The Tet Offensive created new pressure on the Federal purse, helping to ensure (among other things) that NASA's budget slide would continue in FY 1969 and beyond.  

Despite the war and other national challenges, in the period covered by the Downs and Thompson plan NASA managed to fly a dozen planetary missions, of which 11 reached their targets. In large part, these were justified in terms of heading off new Soviet space victories and providing an avenue for the development of new technology with defense implications. 

All the flown missions were directed toward major planets; none would visit asteroids or comets and (of course) none would include astronauts. Italicized initial dates given below are launch years.

  • 1969: The Mariner '69 Mars flyby spacecraft were designated Mariner 6 and Mariner 7 after launch; they left Earth atop Atlas/Centaur rockets.
  • 1971: The Mariner '71 Mars orbiter spacecraft were designated Mariner 8 and Mariner 9 after launch; Mariner 8's Atlas/Centaur rocket malfunctioned but Mariner 9, the first planetary orbiter, was a great success, mapping all of Mars until late 1972.
  • 1972: Pioneer 10, launched on an Atlas/Centaur rocket with a solid-propellant kick stage, became the first spacecraft to traverse the Asteroid Belt;  in 1973, it became the first spacecraft to fly past Jupiter. The gravity-assist kick it received made it the first spacecraft placed on a path to escape the Solar System.
  • 1973: Pioneer 11 followed Pioneer 10 through the Asteroid Belt to Jupiter; in 1979 it became the first spacecraft to fly past Saturn.
  • 1973: Mariner 10 left Earth on an Atlas/Centaur rocket and flew past Venus in early 1974; later that year it became the first spacecraft to fly past Mercury. It flew past Mercury twice more in 1974-1975.
  • 1975: Viking 1 and Viking 2, each of which comprised a lander and a Mariner-derived orbiter, launched atop Titan III-E rockets, arriving in Mars orbit in June 1976 and August 1976, respectively. Viking 1, which touched down on 20 July 1976, was the first successful Mars lander; Viking 2 landed successfully on 3 September 1976. Their life detection experiments yielded equivocal results.
  • 1977: The Mariner Jupiter-Saturn '77 spacecraft were renamed Voyager 1 and Voyager 2. They left Earth atop Titan III-E rockets. Voyager 1 flew past Jupiter in 1979 and Saturn in 1980; Voyager 2 flew past Jupiter in 1979, Saturn in 1981, Uranus in 1986, and Neptune in 1989.
  • 1978: Pioneer Venus Orbiter and Pioneer Venus Multiprobe (PVM) launched atop Atlas/Centaur rockets. Though not designed to survive landing, one PVM small probe continued to operate after striking the surface, becoming the first (so far only) successful U.S. Venus lander.

The Pioneer Venus Multiprobe bus (lower right) is shown deploying three small probes (center) and one large probe (upper left). In reality the large probe was deployed on 16 November 1978 and the small probes were deployed on 20 November 1978. The bus and probes entered the Venusian atmosphere on 9 December 1978. Image credit: NASA.
In their report, Downs and Thompson anticipated that NASA would be given the go-ahead to start a new piloted planetary program in FY 1971 or  FY 1972, and after a fashion they were correct. In January 1972, President Richard Nixon called on Congress to fund the winged Earth-orbital Space Shuttle. 

Originally proposed as a low-cost fully reusable Space Station crew rotation and resupply vehicle, the Shuttle became instead a multi-purpose spacecraft after Nixon refused to fund a Space Station. It would be only semi-reusable, which lowered its development cost but dramatically increased its operations cost. Among its goals was to launch all U.S. robotic planetary spacecraft.

Downs and Thompson's NASA budget prediction — $5-6 billion annually by about FY 1972 — entirely missed the mark. In terms of buying power in an inflationary time, NASA's budget remained at about half that amount throughout the 1970s and early-to-mid 1980s. Funding scarcity adversely impacted both Shuttle development and planetary exploration. 

Shuttle development problems traceable to funding shortfalls, lack of successful new Soviet planetary missions, tight planetary science budgets, and the Challenger accident (28 January 1986) came together to create an 11-year hiatus in new U.S. planetary launches following the 1978 Pioneer launches. The stoppage ended at last with the launch of the Magellan Venus radar mapper on board the Shuttle Orbiter Atlantis on 4 May 1989. 

By the time Magellan flew, NASA had announced that it would cease Shuttle planetary launches after it launched the Galileo Jupiter orbiter and probe and Europe's Ulysses solar polar orbiter in favor of resuming planetary launches on expendable rockets. Galileo launched on board the Orbiter Atlantis on 18 October 1989 and Ulysses launched on board the Orbiter Discovery on 6 October 1990. 

Sources

The first two sentences of this post are based on the first sentence of Charles Dickens' 1859 novel A Tale of Two Cities.

The Space Program in the Post-Apollo Period: A Report of the President's Science Advisory Committee, "Prepared by the Joint Space Panels," The White House, February 1967.

"Science Advisers Urge Balanced Program," Aviation Week & Space Technology, 6 March 1967, pp. 133-137.

"Orbiters Studied for Planetary Missions," W. J. Normyle, Aviation Week & Space Technology, 23 October 1967, pp. 30-32.

"Washington Roundup: NASA Thanks You," Aviation Week & Space Technology, 20 November 1967, p. 25.

"Apollo 4 Closes Gaps to Lunar Mission," W. J. Normyle, Aviation Week & Space Technology, 20 November 1967, p. 26-27.

"NASA Pushes Planetary Program," W. J. Normyle, Aviation Week & Space Technology, 27 November 1967, pp. 16-17.

"Remarks Following an Inspection of NASA's Michoud Assembly Facility Near New Orleans," President Lyndon Baines Johnson, 12 December 1967 (https://www.presidency.ucsb.edu/documents/remarks-following-inspection-nasas-michoud-assembly-facility-near-new-orleans — accessed 30 August 2022).

"A Feasible Planetary Exploration Program Through 1980 — Case 710," J. P. Downs and W. B. Thompson, Bellcomm, Inc., 26 February 1968.

Astronautics & Aeronautics 1967, NASA SP-4008, 1968, pp. 43-45, 246, 248, 255-256, 282-284, 295-296, 314, 320, 323-324, 333, 336-343, 352-353, 373-375.

Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles, NASA SP-4206, Roger E. Bilstein, NASA, 1980, pp. 351-360.

More Information

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

NASA's Planetary Joint Action Group Piloted Mars Flyby Study (1966)

Missions to Comet d'Arrest & Asteroid Eros in the 1970s (1966)

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

The First Voyager (1967)

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

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