The Space Reviewin association with SpaceNews

FLO launch vehicle
FLO would have required the development of a new launch vehicle larger than the Saturn 5 although using variants of the Saturn’s rocket engines. (credit: NASA)

The last lunar outpost

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FLO landers

One of the design guidelines for FLO was to reduce lunar surface operations required to activate the lunar outpost. This would reduce crew support requirements on the transportation system and also allow crew time to be devoted to science and resource studies. Another design guideline was to have the human and habitat module flights utilize the same trans-lunar injection and lander elements. Finally, the landers were to use as much existing equipment as possible to reduce development costs.

FLO involved the use of two kinds of lunar vehicles, an unmanned habitat module and a manned lander. Both vehicles would use essentially the same landing stage to minimize complexity and would have a gross mass at trans-lunar injection of 95,760 kilograms. The habitat lander would weigh 56,796 kilograms and the piloted lander 56,588 kilograms. They would carry their cryogenic propellants in eight main propellant tanks. Each would carry 43,954 kilograms of fuel. The landing stage would be 7.1 meters tall and have a span with its landing legs deployed of 18.8 meters wide. The piloted lander would stand 14.1 meters tall and the astronauts would descend by a vertical ladder to a platform on the lander stage before descending down a sloping stair ladder to the surface.

FLO involved the use of two kinds of lunar vehicles, an unmanned habitat module and a manned lander.

Each FLO flight would require a single launch. The landers would be powered by four engines derived from the highly-dependable RL-10 engine used on the Centaur upper stage. The habitat module would utilize a cylindrical module then under development for Space Station Freedom. It would be launched to the Moon and land automatically with two-kilometer accuracy. It would then autonomously deploy two large solar panels, radiators, and other antennas, and await the arrival of the crew—the goal was to allow the astronauts to land and instantly set up shop, rather than requiring them to build facilities as envisioned by the original Space Exploration Initiative plans. The overall width of the vehicle with its solar panels deployed on the lunar surface would be 41.1 meters. The habitat module would also be equipped with regenerative fuel cells to provide power during the 14-day lunar night. During the daytime, electricity from the solar cells would be used to separate water into hydrogen and oxygen, and during the night the fuel cells would combine them, producing electricity and water.

Once the habitat module was satisfactory, the manned spacecraft with its four-person crew could be launched to the Moon. The transit time would be slightly over four days. It too would land automatically, because the astronauts would have no view of the surface during touchdown.

The manned spacecraft would be designed for a 45-day stay on the Moon and would utilize storable propellants for its ascent stage. It would have to be able to carry five metric ton of supplies and would be capable of returning its 4-person crew and 200 kilograms of cargo to a land landing on Earth. The crew module itself would be an Apollo capsule shape, but increased by 5% for larger crew and EVA suits. The capsule would have a thermal protection system consisting of both tiles and ablatives, and would have a parachute and retrorocket deceleration system, like the Russian Soyuz.

Mission to Mare Smythii

The initial landing site that the FLO team selected was Mare Smythii, near the equator on the eastern limb. This was merely a baseline, “strawman” mission intended to outline the types of operations that a crew could perform on the Moon. The team also evaluated an alternate site at the Aristarchus Plateau at 23° north, 48° west to determine if it made any significant difference in the reference mission. They concluded that except for some specialized sites, such as the lunar poles, the bottoms of craters or other unusual terrain, the mission science payload and the EVA activities would not change much from site to site. The FLO team acknowledged that the actual landing site and scientific missions would be selected by appropriate committees, panels and representatives from the respective science disciplines.

After the crew touched down and settled into their habitat module, they would conduct nine loping traverses using an unpressurized four-person lunar rover. They would drive out a maximum of 25 kilometers from base, visiting all major features and gathering detailed geologic data from an area about 50 kilometers around the outpost. Each traverse was divided into segments suitable for one eight-hour EVA on the rover. The initial timelines indicated that about five or six of the traverses could be completed on one mission. The remainder would be left for future missions. One of the plans for FLO was to leave the habitat module unattended on the surface for up to six months.

The science and payloads team determined that there would be four major scientific disciplines conducted during the mission: astronomy, geophysics, life sciences, and space and solar systems physics. The astronauts would deploy a number of instruments on the surface, some of which required human tending and others that were “set and forget.” The payloads were:

  • Geophysical Monitoring Package
  • Solar System Physics Experiment Package
  • Traverse Geophysical Package
  • Lunar Geologic Tool Set
  • Lunar Transit Telescope
  • Small Solar Telescope
  • Robotic Package for Rover
  • Life Science Package

The heaviest payload would be an In-Situ Resources Utilization (ISRU) Demonstration Package. The ISRU package would consist of various experiments for the astronauts to demonstrate the use of resources on the Moon, such as heating lunar regolith to extract oxygen. NASA considered that successfully demonstrating this capability was vital to any future long-term presence on the Moon.

According to Guerra and Joosten, FLO would cost $25 billion (1993 dollars) through 2005, the time of the first mission. Fifty percent of this cost—$12.6 billion—would be required to build the new heavy lift launch vehicle.

The second mission would have different science goals. The crew would complete the traverses not performed on the first mission and begin a detailed drilling program with a ten-meter drill using data from the traverses to determine optimum drilling locations within 20 kilometers of the outpost. They would also bring and deploy the initial elements of a radio telescope array and revisit the optical telescope site and switch detectors as an operational test.

The mission would require a new spacesuit that improved mobility and required less maintenance than the existing space shuttle suits. The suits would also not require the astronauts to pre-breathe oxygen in order to avoid the bends as a result of nitrogen bubbling in the bloodstream. This pre-breathing technique, common to American EVA procedures, would be too disruptive of the lunar exploration schedule and would make things like emergency EVAs impossible.


NASA apparently did not produce a cost estimate of the First Lunar Outpost at the time that it was announced because the agency had not performed enough engineering work. However, in 1993 Kent Joosten of NASA’s Johnson Space Center and Lisa Guerra of Science Applications International Corporation presented an alternative lunar exploration plan that included an independent estimate of FLO costs. According to Guerra and Joosten, FLO would cost $25 billion (1993 dollars) through 2005, the time of the first mission (as opposed to the original goal of 2000). Fifty percent of this cost—$12.6 billion—would be required to build the new heavy lift launch vehicle. The space transportation systems would cost $7.3 billion, habitation systems would cost $2.1 billion, surface systems would cost $1.9 billion and science payloads would cost $1.1 billion.

Joosten and Guerra proposed that by using lunar resources early in the exploration program, they could reduce the amount of payload that had to be lifted to the Moon. This would allow the use of a smaller launch vehicle that was less expensive to develop. They labeled their proposal LUNOX for its reliance upon lunar oxygen. But the LUNOX proposal received far less detailed attention than FLO.

FLO’s legacy

First Lunar Outpost was publicly unveiled in August 1992 and although it would have been far cheaper than the 1989 proposal, it had little chance of being funded considering the existing political climate. By November, President George H.W. Bush lost reelection and when President Bill Clinton was sworn into office in January 1993 nobody had any illusions that lunar exploration missions would continue.

Nevertheless, FLO established some important benchmarks. The 90-Day Study of 1989 had been so ambitious and expensive that it was simply not credible. It produced bafflement and incomprehension in those who tried to understand it. FLO was far less ambitious and established clearer goals—limited stays on the lunar surface to conduct specific science missions. It was small enough and reasonable enough that it provided a good foundation for discussion. After NASA unveiled FLO, industry and NASA groups proposed cheaper alternatives to try and achieve many of the same objectives. In 1993 the American Institute of Aeronautics and Astronautics held a “Low Cost Lunar Access” symposium to consider cheaper ways of returning Americans to the Moon. General Dynamics unveiled its “Early Lunar Access” proposal. Rather than two Saturn 5-plus class vehicles for each mission to the Moon, the General Dynamics proposal would have required four launches: two Titan 4s and two space shuttle launches. And as already noted, Guerra and Joosten also proposed a method of using lunar resources to reduce launch mass requirements. They calculated that this approach could save up to six billion dollars compared to FLO, but with greater technical risks, such as the requirement for a nuclear reactor and development of processing equipment for the lunar regolith.

The First Lunar Outpost was in many ways a very conservative approach to returning to the Moon. Although it would have required a massive new launch vehicle, key parts of that launch vehicle—the engines—represented no technical risk. Reusable spacecraft, although possibly cheaper in the long run, also posed significant development risk and so FLO avoided them. Most of the technology for the mission already existed. Certainly designing new systems based on this technology and integrating them would not be easy, but there is no reason to believe that this would be particularly troublesome.

FLO demonstrated many of the tradeoffs that NASA will have to revisit now—using proven, but expensive technology vs. developing potentially cheaper alternatives, and selecting a mission mode that minimizes launch cost and complexity versus one that allows maximum flexibility at the Moon. As NASA picks a new way of returning to the Moon, FLO will certainly play a part.