S-IVB/IU Applications: The LASS Proposal (1966) (2)
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(...)
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