With less than a month to go before the 40th anniversary of humanity’s last foray to the Moon, the indications are growing stronger that we may return there in the early part of the next decade. Already, NASA plans an uncrewed Exploration Mission-1 (EM-1) atop its first Space Launch System (SLS) booster – with launch currently targeted for December 2017 – to send an Orion Multi-Purpose Crew Vehicle (MPCV) on a seven-to-ten-day voyage around the far side of our closest celestial neighbor. This will be followed by EM-2, scheduled for 2021, but with some scope to move to the left, which NASA sources have revealed will carry as many as four astronauts to the Moon. The precise objectives of EM-2 remain unclear and have aroused criticism and praise in equal measure, but may suggest a shift in policy from the Obama Administration’s earlier desire to avoid human lunar exploration in favor of missions to an asteroid by 2025 and Mars by the mid-2030s.
It is no coincidence that the expected NASA announcement on Beyond Earth Orbit exploration will emerge within weeks or even days of President Obama’s re-election to a second term in office. Yet whichever candidate had succeeded in the contest for the White House – Obama or his Republican challenger, Mitt Romney – was not expected to drastically alter the space agency’s fortunes. Two years ago, Obama stubbornly refused to consider a human return to the Moon and his infamously short-sighted summary, “We’ve been there before”, spoken whilst standing with Buzz Aldrin, continues to echo in many ears and continues to cause more than a few toes to curl and teeth to grind.
Recently, in September, NASA Deputy Administrator Lori Garver told a press conference that the agency had submitted “a comprehensive report” to Congress, with clear outlines of future Beyond Earth Orbit destinations, featuring not only asteroids and Mars, but also a peculiar spot in space known as the ‘Earth-Moon Libration Point-2’ (EML-2’). Libration points – also known as ‘Lagrangian Points’, named in honor of the 18th-century French-Italian astronomer and mathematician Joseph-Louis Lagrange – are regions in space where the combined gravitational pull of two large masses roughly balance one another out. This enables spacecraft to effectively ‘park’ there. To reach EML-2, a spacecraft would need to travel to a position approximately 37,000 miles beyond the Moon and the potential benefits include the provision of a communications station covering the lunar far side or a unique location for an astronomical telescope…or, as Boeing proposed late last year, for the emplacement of a ‘propellant depot’ for future deep-space exploration.
“We’re going back to the Moon, attempting a first-ever mission to send humans to an asteroid and actively developing a plan to take Americans to Mars,” Garver concluded in her September remarks. At first sight, the use of what Obama previously regarded as a dirty word – Moon – would appear to be totally at odds with Garver’s comments.
However, it is becoming more likely that ‘going back’ to the Moon does not necessarily feature boots on the surface, but instead exploration of EML-2 as part of a stepping-stone process to reach an asteroid by 2025 and Mars orbit a decade or so thereafter. “NASA does not have plans to put human boots on the surface of the Moon,” Rachel Kraft of the agency’s Office of Communications recently told AmericaSpace. “Both EM-1 and EM-2 will help validate the spacecraft and Space Launch System before going into deep space on subsequent missions.” If a crew reaches EML-2, it will be the furthest any human voyage has even travelled from Earth.
In December 2011, Boeing authored a presentation for a so-called ‘Exploration Gateway Platform’, which would be establish an outpost either at EML-2 (beyond the Moon) or EML-1 (a point in cislunar space, about 200,000 from Earth and 40,000 miles from the Moon). This outpost would be assembled at the International Space Station and would potentially include already-extant hardware, such as NASA’s proposed Node 4, which currently takes the form of a structural test article at the Kennedy Space Center, together with an old Shuttle airlock, a Multi-Purpose Logistics Module (MPLM) for a habitat and an ‘international module’. The Gateway would then be transferred to either EML-1 or EML-2 by means of a ‘tug’.
And herein resides much of the interest. NASA is known to be seriously entertaining the notion of such a Gateway, whose role as a propellant depot should enable the launching of missions to the Moon and beyond at far less expense in terms of cost and propellant usage. Boeing’s plan involved a reusable lunar landing vehicle, which would be transferred ‘dry’ (unfuelled) to the Gateway, loaded with propellant and despatched for its mission to the surface of the Moon. Other plans for the Gateway include allowing NASA and possibly its international partners to learn more about supporting humans in deep space for long durations and could possibly involve the ‘teleoperation’ of rovers on the lunar far side. The agency hopes to accomplish such missions without breaking the boundaries of its tight budget, which currently stands at $17.7 billion in the proposed 2013 federal allocation.
Much of the criticism of the EM-2 mission – presently scheduled for 2021, some four years after EM-1, but with an option to move forward as much as two years to August 2019 – centers on the fact that a flight into lunar orbit with a crew of four offers little more than a repeat of what Apollo 8 accomplished in December 1968. Powerful Congressional voices, including many in support of NASA’s plan, have called for an explanation of what EM-2 seeks to achieve and what new ground it will break.
On the other hand, it must be kept in mind that any form of crewed exploration beyond Earth orbit has not even been attempted, let alone achieved, in almost five decades and even a repeat of Apollo 8 marks a dramatic step forward and a clear move toward re-establishing a human presence, far from the Home Planet. At present, the primary aim of EM-2 seems to be an all-out test of Orion’s life-support capabilities in the cislunar and lunar-orbital environments. It will remain in the vicinity of the Moon for several orbits, at a high altitude of between 540 and 1,620 miles, because the spacecraft itself is providing both lunar-orbit insertion and trans-Earth injection engine burns and will thus have insufficient propellant reserves to enter a lower lunar orbit on this mission.
Yet the nature of the mammoth launch vehicle for EM-1 and EM-2 is clear. Powered by three donated Space Shuttle Main Engines (SSME) and a pair of five-segment Solid Rocket Boosters, the first SLS booster will stand 318 feet tall. For EM-1 – presently entitled ‘Uncrewed Beyond Earth Orbit Demonstration’ and scheduled for launch in December 2017 – an Orion spacecraft will be inserted into a high-apogee orbit of 975 miles, more than four times higher than the International Space Station. An Interim Cryogenic Propulsion System (ICPS) will then execute the first ‘trans-lunar injection’ of a human-capable vehicle in almost five decades. Eventual plans are for these ICPS ‘kick stages’ to sport J-2X engines, of Saturn V heritage, although it appears likely that EM-1 will utilize a Delta Cryogenic Second Stage. This latter stage is also currently baselined for the inaugural Exploration Flight Test-1 (EFT-1) Orion mission to high Earth orbit in September 2014.
In the wake of the TLI ‘burn’, Orion will spend three to four days in the region between Earth and the Moon, called ‘cislunar space’, before swinging around the far side and coming home via a free-return trajectory to a parachute-assisted splashdown in the Pacific Ocean. Re-entry into Earth’s atmosphere will involve speeds of up to 25,000 mph – much faster than the 17,500 mph endured by the Shuttle or Soyuz – and will wring out an exotic heat shield, whose design is presently being finalized. NASA appears to favor an Avcoat and Phenolic Impregnated Carbon Ablator, which draws close parallels with the heat shield used on the Apollo Command Module, and several hundred Alumina Enhanced Thermal Barrier (AETB-8) protective tiles. Although the EFT-1 mission is scheduled to test this heat shield at an approximate lunar-return velocity in less than two years’ time, EM-1 will mark the first occasion on which it will be trialled on a ‘real’ Beyond Earth Orbit voyage.
The next manned SLS, tentatively scheduled for 2022, will feature an upgraded version of the heavy-lift booster – with a four-engine core and capable of carrying 105 metric tons into low-Earth orbit, as opposed to the 70 metric tons of its predecessors – and may support the Gateway by transporting solar electric propulsion hardware aloft to move the assembled modules to EML-2. Subsequent human missions would then have much of the hardware in place to enable Obama’s nebulous goal of a voyage to an asteroid in around 2025. Furthermore, the establishment of a Gateway would highlight the important legacy and role of the International Space Station in NASA’s 21st-century exploration architecture. “NASA is executing the President’s space exploration plan that includes these missions around the Moon, to an asteroid and eventually to Mars,” Rachel Kraft told this author. “There are a variety of routes and options being discussed to help us build the knowledge and capabilities to get there.”Missions » ISS »