NASA teams evaluating ISS-built Exploration Platform roadmap
NASA’s Human Architecture Team (HAT) are coming to the conclusion of their support activity phase for what could be the major focal point for exploring deep space destinations. The Exploration Gateway/Platform – constructed from international modules at the ISS, before being deployed to EML2 – would see greater involvement from “existing launchers” in building the staging ground for missions to the Moon, Asteroids and Mars.
The Current Plan:
Several documented dates for the completion of an exploration roadmap have come and gone over the last several months, mainly due – it is claimed – to the uncertainty with NASA’s long term budget projections.
However, a baseline of sorts does exist, mainly via the opening options created by the Exploration Systems Development (ESD) Design Reference Missions (DRM) – as outlined in the Space Launch System (SLS) Concept Of Operations (Con Ops) document, available in L2 (L2 Link).
The most solid element of the plan is the 2017 launch of the Space Launch System (SLS), with an uncrewed Orion, for a system validation/certification of the vehicles during a full mission.
The mission itself is called Exploration Mission -1 (EM-1) – carefully worded as the “Notional Mission for Orion First Flight in 2017: Uncrewed Beyond-Earth Orbit (BEO) Demonstration” flight, resulting in the debut of the Heavy Lift Launch Vehicle (HLV) in its 70mt Block 1 configuration.
Launching Orion into an high-apogee orbit of 975 nmi at the insertion point, the kick stage/ICPS (Interim Cryogenic Propulsion Stage) – a Delta Cryogenic Second Stage (DCSS) – would then conduct the Trans Lunar Injection (TLI) burn(s) to send Orion towards a date with the Moon.
The seven to 10 day mission would come to a conclusion with Orion parachuting to a splashdown in the Pacific Ocean, for what would be its second such return, following the Exploration Flight Test (EFT-1) demo in 2014.
The current plan then sees a four year gap before the next flight of the SLS, in 2021, known as Exploration Mission -2 (EM-2). This is an almost carbon copy of EM-1, except this time the mission is crewed for the trip around the Moon.
While this four year gap is painfully uninspiring, the rest of the current plan is painfully undefined, with NASA leadership continuing to use an almost scripted line of “heading to an asteroid in the mid 2020s, followed by Mars in the mid 2030s“.
It is likely such leaders are unable to say any more, given the political direction they have to abide by, and the impossibility of setting specific targets and dates that range decades – and many administrations – into the future.
The Developing Plan:
While EM-1 remains solid on the forecast, not least due to the requirement of validating SLS and Orion in deep space, source notes (See L2 Exploration Roadmap Section – L2 LINK) over recent months have portrayed a continuing sea change towards a more exciting approach that marries existing capability with the future exploration aspirations.
Mainly referred to as the Exploration Gateway – but also known as the Exploration Platform or L2 Waypoint – the concept calls for the launch of several modules for construction at the International Space Station (ISS), prior to departing to Earth-Moon Lagrange (EML) point 2, located on the far side of the Moon, serving as a deep space outpost.
Several conceptual versions of the Gateway have been complied since it first started to gain mentions in the Exploration debate last 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 to the ISS.
“Using existing hardware and the ISS infrastructure provides a flexible and affordable way to demonstrate technologies and build a deep space Exploration Platform in the near term,” noted one presentation on the ISS construction element of the Gateway.
The existing hardware would involve an orbiter external airlock, an MPLM (Multi-Purpose Logistics Module) habitat module, and an international module, linked by the Node 4/DHS (Docking Hub System) at the orbital outpost.
The hardware would be launched on a flexible timeline, allowing for the initial assembly & checkout period and boost & initial crew periods to be phased to match resources.
With the modules ranging from only 11mt to 13mt in mass, most Exploration Platform concepts cite the use of existing launch vehicles for lofting the hardware to the ISS.
“Atlas V medium (5X1 series) performance suited to estimated module mass,” cited one presentation. “Augmentation for orbital operations (Launch Mission Kit) estimated mass is approximately 3mt. Centaur upper stage provides flexible accommodations for kit.”
It was also shown that the capability is based on a payload to 51.6 deg inclination, 407km circular orbit. However, given expendable vehicle systems normally have short mission durations, launching these elements will require augmentation with a Launch Mission Kit (LMK), as covered by one presentation to the Future In-Space Operations Colloquium (FISO) last year.
“Launch Mission Kit expands the functionality of the payload attach structure. Additional thrusters, propellant, and pressurization tanks to provide 6 DOF control. Computer systems for spacecraft control. Solar arrays and batteries for spacecraft power and keep alive power to element being flown.
“LMK shares functionality with the Centaur. Functions are separated to maintain existing launch vehicle qualification.”
A Russian Proton was also shown as a potential candidate to launch the international module. Plus, it is understood NASA managers have discussed the Exploration Platform with ISS partners, gaining positive responses.
With the ability to launch, assemble and checkout the Exploration Platform at the ISS, the next challenge would be to deploy it to its EML2 destination.
While FISO note a Space Tug could be used, the growing preference is to use a Solar Electric Propulsion (SEP) system, with big hitters such as Boeing and Aerojet openly supporting such an option for the Exploration Platform.
“We believe that Aerojet’s current Solar Electric Propulsion technology, such as that used to rescue the AEHF satellite, is immediately applicable to a key role in Human Space,” noted Julie Van Kleeck, Aerojet Vice President, Space & Launch System in an interview with NASASpaceflight.com earlier this year.
“For example, a 25-40 kW SEP vehicle using current technology can pre-position a human-tended habitat at L-2 to support initial Orion missions. This approach would provide an immediate deep space destination for astronauts, and L-2 is an excellent way-station to the rest of the solar system.”
Both SLS and Boeing documentation show SEP hardware being lofted uphill by the SLS, although the latter presentations mainly refer to mission specific SEP hardware, to be used to create a Near Earth Asteroid (NEA) vehicle, a vehicle that departs from the Exploration Platform itself, using a large SEP system for the journey.
Speculated as a potential realignment of SLS’ role by sources, a move towards a platform would re-manifest SLS’ missions past EM-1, potentially bringing a previously cited 2019 “Cargo” mission on line (SLS-2), one that could be used to aid the Platform by launching the SEP module via a Block 1 vehicle, prior to a crewed mission to the Gateway itself as the SLS-3 mission in the early 2020s.
Relevant to SLS’ use, the HLV is still handed a large role in the architecture, including the FISO “existing launcher” overview. Alternative concepts – citing the use of propellent depots – do exist, both with and without SLS’ involvement.
What is known about having an Exploration Gateway staged at EML2 is how it opens up numerous destinations, such as the Lunar surface – recently added to the ESD ConOps presentation as a “Lunar Surface Sortie” DRM, potentially expanding the overall plan into a more exciting “Moon, NEA, Mars” roadmap.
Should the international element of the Platform also provide additional framework for international exploration missions, the viability of committing to such missions may also receive a boost via costs sharing and a more stable political goal, as seen via the International Space Station model.
However, with the 2010 Authorization Act very much the law of the land – an Act that does not mention an Exploration Gateway – any changes may be sensitive at the political level.
As such, this current effort via the HAT – as cited on documentation acquired by L2 – LINK – will likely remain only as internal planning, as opposed to an official plan, for some time to come.
(Images: Via NASA, Boeing and L2 content from L2′s SLS specific L2 section, which includes, presentations, videos, graphics and internal updates on the SLS and HLV, available on no other site.)
(L2 is – as it has been for the past several years – providing full exclusive SLS and Exploration Planning coverage. To join L2, click here: http://www.nasaspaceflight.com/l2/)