European or Asian manned spacecraft using a US Earth departure stage to reach lunar orbit is one possible concept to be discussed this year by the world's leading space agencies as they work towards an international lunar outpost reference architecture by mid-2011.
That architecture is likely to include multiple transport approaches using different vehicles to guarantee that a lunar outpost can be supplied and its crews returned to Earth when necessary. Another use of multiple transport systems is for crew rescue - for example stranded astronauts in Earth or lunar orbit - could be met by a rescue spacecraft.
"Rendezvous and docking standards are being looked at this year," says the European Space Agency's human spaceflight directorate's exploration architecture office head, Bernard Hufenbach, ESA's member of the International Space Exploration Coordination Group (ISECG). This team that consists of the world's major space agencies such as NASA, ESA, the Russian Federal Space Agency and the China National Space Administration, is leading the architecture work.
At the ISECG's 10-12 March meeting, hosted by the Japan Aerospace Exploration Agency in Yokohama, there was agreement to study three lunar scenarios for the architecture until August 2010.
The scenarios are a sortie mission that sees astronauts live on the lunar surface for up to seven days; an extended-stay version of the sortie mission; and a lunar outpost. But this scenario work is not going to add detail such as how the missions are executed or which agency does what.
"It is about standard interfaces, interoperablity, where it is needed, where do we benefit? We're trying to say, 'where is the potential value in having redundant systems?'," says NASA exploration systems mission directorate's international partnerships programme executive, Richard Leshner, another ISECG member.
The focus on redundancy is because having one transport system is seen as too risky. The ISECG 2008 annual report, published along with the Yokohama meeting's joint statement, says: "The NASA-provided transport elements cannot surmise the full suite of systems operating on the Moon if human lunar exploration is to have a sustainable future."
NASA's transport elements are its Constellation programme's Ares I crew launch vehicle, the Orion crew exploration spacecraft that is launched by the CLV, the Ares V cargo launch vehicle (CaLV) and the CaLV's Earth departure stage and Altair lunar lander.
|Lunar Sortie Mission Scenario
This is one or more short duration flights to any location on the Moon. The crew lives out of the NASA Altair lander or another human lunar lander and conducts up to seven days of scientific activities. Pre-deployment of yet to be defined resources could aid the astronauts.
Extended-Stay Mission Scenario
This uses pre-deployed resources, possibly a habitat with food, power systems and fuel to extend the stay beyond the envisaged lunar lander seven-day limit. The extended stay enables more scientific exploration and the demonstration of technologies needed for a lunar outpost or human missions to Mars.
Polar Lunar Outpost Scenario
A permanent human lunar outpost at one of the poles, crews stay for up to 180 days at the base that would be constructed with a relatively small number of missions. It would begin delivering science objectives during its construction and eventually allow the development of capabilities for an international human mission to Mars.
Today, while ESA's EADS Astrium Ariane 5 and JAXA's Mitsubishi Heavy Industries H-IIB rockets could put into low Earth orbit, an Earth departure stage could not launch the Altair, which has a mass of 45,000kg (99,000lb).
China is not expected to have an Ariane 5-like capability until at last 2015 and Russia's plans for a new rocket have a later in-service date and it is not on the scale of Ares V's 71,000kg (156,000lb) to trans-lunar injection capability.
The ISECG scenarios also refer to pre-deployed assets for the extended-stay mission and possibly for sorties. This could mean more Ares V launches. "It is true to say that pre-deployed could mean additional launches," Leshner acknowledges.
But those additional launches could also be Ariane 5s, as ESA has already expressed its interest in developing a lander with a 1,000kg cargo capability.
To complete the scenario work, two or three more workshops before August 2010 are expected and the next one is likely to be in June. The mid-2010 target date is a useful date for NASA.
It will have its lunar surface concept review then, while ESA will be working towards its next triennial ministerial meeting in 2011 that decides its budget and programmes until 2014.
The ISECG work is not only helpful for near-term policy decisions, it is also to inform planning for an international manned Mars mission.
Leshner says: "Can you do these things at the Moon? To learn, with extended stays or outpost missions, about power and thermal management for a Mars mission?"