Exploration Alternatives: From Propellant Depots to Commercial Lunar Base
As NASA managers continue to work modifications to an unreleased exploration plan, one that has a Heavy Lift Launch Vehicle (HLV) at its center, the highly popular concept of an exploration highway – enabled by propellant deports – continues to gain positive overviews. Such a technology may also be involved in a major new commercial effort that will soon be announced.
From the standpoint of the general public, NASA’s exploration goals appear to be no further along from when they were first announced by NASA administrator Charlie Bolden, despite what continues to be a large amount of interesting and positive work behind the scenes.
Officially, the Agency has ambitions to launch their new HLV, the SLS, in 2017 and 2021, both on missions that will conduct orbital visits of the Moon – the latter being crewed. NASA will then aim to conduct mission(s) to a Near Earth Asteroid (NEA) in the 2025s, followed by the ultimate goal of sending a crew to Mars in the 2030s.
To any space flight follower, the goals may be interesting, but the time-frame and costs are unattractive, not least because the very nature of such multi-billion dollar missions over a period of decades – and potentially several changes of government – risks downstream cuts and even cancellation.
Refinements to the plan are being evaluated, with the biggest potential change coming in the form of an Exploration Gateway, constructed from international modules at the ISS, before being deployed to Earth-Moon Lagrange (EML) point 2.
Mainly referred to as the Exploration Gateway – but also known as the Exploration Platform or L2 Waypoint – the concept calls for its construction prior to departing via Solar Electric Propulsion (SEP) to a location near the far side of the Moon, serving as a deep space outpost.
Several conceptual versions of the Gateway have been produced since it first started to gain mentions within the Exploration debate last year – as covered in several articles by NASASpaceFlight.com over the past year.
However, the concepts that involve the use of a large amount of existing hardware are understood to be the most viable, with costs further mitigated by the use of existing launchers to loft the hardware uphill to the ISS.
Such a Gateway would allow for missions to be staged to Lunar orbit, Lunar surface, NEAs and Mars and/or its moons.
Using Propellant Depots:
Based around a solution to one of the central problems for launch vehicles and spacecraft, propellant depots are a highly favored approach to removing the need to launch with all the fuel required to complete an entire mission – in turn allowing launch vehicles to lift more hardware into space.
Otherwise seen as gas stations in space for journeying vehicles, the ability to refuel one’s spacecraft in space continues to gain positive reviews in documentation, including NASA’s own evaluations. However, it has yet to become a major part of NASA’s official exploration plans.
While some see Propellant Depots as a way to remove the need for a HLV - instead using existing medium range launch vehicles to launch spacecraft on a path that stops off at a depot - even the authors of such proposals note the two paths are not mutually exclusive and could work together.
Numerous presentations have been published on the subject of Propellant Depots, ranging from NASA’s own Human Architecture Team (HAT) – who were actively working on a roadmap towards evolvable demonstrations of the hardware – through to the United Launch Alliance (ULA) “Master Plan” outline, based on the backbone of their ACES (Advanced Common Evolved Stage) depot.
Dr. George Sowers, ULA vice president of Human Launch Services, noted his company remains supportive of propellant depots, a technology he describes as an “enabler” of multi-architecture exploration.
“ULA is also very supportive of the development of technologies for long duration storage and transfer of cryogenic propellants, as represented by NASA’s CPST (Cryogenic Propellant Storage and Transfer) initiative,” Dr. Sowers told NASASpaceFlight.com.
“These technologies are, in my opinion, enabling of BEO (Beyond Earth Orbit) exploration regardless of the launch architecture. We are incorporating many of these technologies into ACES.”
The dream ticket would be for a full suite of technologies to allow for multiple exploration possibilities, one where SLS’ superior lift capability is put to specific use, Propellant Depots line the BEO path, while the Exploration Gateway – itself also potentially hosting a Prop Depot – provides the deep space “launch pad” for interplanetary destinations.
However, NASA’s funding is constantly restricted by the uncertain future at the political level.
One solution, according to Dr. Sowers, is to utilize the incremental approach, building a path than has deep foundations in viability, thus making it more resilient to cuts and cancellation.
“My approach to exploration would be incremental. Do what you can now with what you got,” he noted. “Build on that experience to take the next step. An incremental approach is more realistic and sustainable in today’s political and fiscal environment. Near term successes to bolster political and public support, tailorable to change, resilient to cuts.”
“In that vein, I think some of NASA’s ideas for near term Lagrange point missions are rational and I hope they get serious consideration.”
The Unannounced Commercial “Game-Changer”:
The official NASA plan does not include a return to the surface of the Moon, distancing itself from the cancelled Constellation Program (CxP) approach of Moon, Mars and Beyond, first cited in the Vision for Space Exploration (VSE).
NASA managers have since created an option for a return, listed as a Lunar Surface Sortie (LSS) mission via the Exploration Systems Development Division (ESD) Concept Of Operations (Con Ops) document (L2), allowing it to become a Design Reference Mission (DRM) alternative, potentially at the expense of a NEA mission in the early to mid 2020s.
While this option remains on the cards, source information acquired by L2 this week revealed plans for a “game-changing” announcement as early as December that a new commercial space company intends to send commercial astronauts to the moon by 2020.
According to the information, the effort is led by a group of high profile individuals from the aerospace industry and backed by some big money and foreign investors – the latter denied after conversations with the company. The company intends to use “existing or soon to be existing launch vehicles, spacecraft, upper stages, and technologies” to start their commercial manned lunar campaign.
The details point to the specific use of US vehicles, with a basic architecture to utilize multiple launches to assemble spacecraft in Low Earth Orbit (LEO). The details make direct reference to the potential use of propellant depots and fuel transfer technology.
Additional notes include a plan to park elements in lunar orbit, staging a small lunar lander that would transport two commercial astronauts to the surface for short stays.
The architecture would then grow into the company’s long-term ambitions to establish a man-tended outpost using inflatable modules. It is also understood that the company has already begun the design process for the Lunar Lander.
Additional: Rumors on the internet that followed this article, citing investor names and launch vehicle contracts are false, according to this site’s sources.
More details ahead of the announcement are expected in the coming days and weeks. L2 Members: Refer to the *rolling updates on this effort, here*
(Images: L2, NASA and ULA)
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