I'd like to discuss cislunar space destinations like lunar orbit, Earth-Moon Lagrange points, and GEO in the context of the Flexible Path to the Moon. Before doing this, however, it's useful to set the stage by considering NASA's plans for these destinations. NASA's current plans are similar to those in the Flexible Path to the Moon in many respects: a focus on commercial and international participation, strong technology development efforts, many robotic precursors, synergy with NASA's science missions and ISS, an initial focusing phase in LEO, and more. However, although both plans include missions to cislunar space, NASA's plans there are quite different from those of the Flexible Path to the Moon.
The Augustine Committee Final Report (PDF) describes the Flexible Path to Mars. This sequence of missions starts with easier beyond-LEO missions like a lunar fly-by, a lunar orbit mission, and/or an Earth-Moon Lagrange point mission. The report gives the impression that these missions are simply stepping stones towards voyages to more distant destinations with a few productive activities thrown in while we're there. The report does not give a sense of the build-up of space infrastructure or repeated visits there.
Ed Crawley from the Augustine Committee and David Mindell recently released a white paper U.S. Human Spaceflight: The FY11 Budget and the Flexible Path (PDF). This white paper confirms the impression that the Flexible Path to Mars does not have a strong cislunar space emphasis. For example, it notes:
The Augustine report envisioned initial test flights within the Earth-Moon system and then operational flights that include visits to "near earth objects" (NEOs, asteroids and spent comets), Mars flybys, Mars orbital flights and eventually exploration of the lunar and Mars surface.
The cislunar space missions are merely test flights, not operational flights. It also states:
Destinations in the Flexible Path have a logical progression. The Augustine report suggested that astronauts might first test the new systems in Earth–Moon space by traveling to lunar orbit and to the Earth-Moon Lagrange points (where the Earth and Moon’s gravity balance each other). Astronauts will then visit Earth-Sun Lagrange points, NEOs, Mars orbit and that of its moons, demonstrating new capabilities for servicing, repair, and construction along the way. These destinations and their value propositions are outlined in Figure 3.5.2-1 of the Augustine report. Additional destinations possible on the Flexible Path are geosynchronous Earth orbit (another place to demonstrate servicing) and eventually asteroids in the belt or Venus orbit.
Clearly the cislunar space destinations not seen as first-class productive and interesting destinations in their own right.
In the Remarks by the President on Space Exploration in the 21st Century, President Obama said:
Early in the next decade, a set of crewed flights will test and prove the systems required for exploration beyond low Earth orbit. And by 2025, we expect new spacecraft designed for long journeys to allow us to begin the first-ever crewed missions beyond the Moon into deep space. So we’ll start -- we’ll start by sending astronauts to an asteroid for the first time in history. By the mid-2030s, I believe we can send humans to orbit Mars and return them safely to Earth. And a landing on Mars will follow. And I expect to be around to see it.
This statement gives the impression that even though we will be going to beyond-LEO destinations like lunar orbit and/or Earth-Moon Lagrange points, and in all likelihood (one or two of) the even more distant Earth-Sun Lagrange points, we won't really be starting until we send astronauts to an asteroid.
In his prepared statements to the Senate's Committee on Commerce, Science, and Technology, NASA Administrator Bolden described the planned series of steps:
Fundamentally, the exploration of space will be a sequence of deep-space destinations for human missions matched to growing capabilities, progressing step-by-step, beginning with crewed flight tests – perhaps a circumlunar mission -- early next decade of vehicles capable of supporting exploration beyond LEO, a human mission to an asteroid by 2025, and a human mission to orbit Mars and return safely to Earth by the 2030s.
NASA clearly considers the cislunar space destinations to be useful for testing deep space exploration capabilities, which of course they are. However, NASA's cislunar space plans don't go beyond these tests. NASA's focus will be on more distant deep space exploration.
Next we will take a very different look at cislunar space in the Flexible Path to the Moon.