With the push for exploration Beyond Earth Orbit (BEO) increasing, a proposed habitat for human exploration outside the confines of Earth’s immediate space is taking shape as NASA presses forward with the development of its new Deep Space Habitat (DSH) – a module-based habitation facility that will be used as part of manned exploration missions to the moon, asteroids, and eventually Mars.
Deep Space Habitat – Building on the modular success of the ISS:
As presented by the AES Habitation Project, the Future In-Space Operations presentation outlines NASA’s progress-to-date, as well as future uses for, the Deep Space Habitat (DSH).
“Develop DSH concepts based on International Space Station Systems,” states the presentation – available for download on L2 (L2 Link).
With an initial size capable of accommodating four (4) crewmembers for a 60-day mission, the DSH will be comprised of a newly-constructed or refurbished HAB module along with a docked Orion space capsule.
Building from this 60-day configuration, the DSH will carry the capability of expanding to a 500-day configuration, which would see the incorporation of an MPLM (Multi-Purpose Logistics Module) to the HAB/Orion duo.
With initial studies completed in the fall of 2011, the HAB/MPLM structure emerged as the current project baseline, allowing for the subsequent and ongoing development of a “Deep Space Command Post concept for Earth-Moon L1 or L2 locations.”
The benefits of using already exiting modules – such as the MPLMs – provides for already on-orbit service verification through the modules’ usage in the construction, utilization, and continuation of the International Space Station.
As noted by the presentation, the potential benefits of using ISS MPLM- and HAB-sized (ISS Lab-sized) modules is that “ISS hardware is flight qualified; the mass may be higher but utilization could reduce overall project cost, schedule, and risk; Incorporates ISS utilization into the program; and it offers an approach to incorporating International participation.”
Ground rules and assumptions:
As with all elements of space travel, the DSH comes with certain ground rules and assumptions for its construction, outfitting, and utilization.
Specifically, the Future In-Space Operations presentation notes that the DSH’s design is “intended to meet HAT (Human spaceflight Architecture Team) missions with modifications as required to utilize current ISS and MPCV (Multi-Purpose Crew Vehicle, also known at Orion) systems and technologies.”
For 60-day missions, the DSH could be utilized by a crew of four astronauts for Earth-Moon Lagrangian Point 1 (EM L1) missions, EM L2 missions, GEO satellite servicing missions, ES (Earth-Sun) L2 missions, Lunar orbit missions, and microgravity free-flyer missions.
Likewise, and more importantly, the 500-day missions of the DSH would see a crew of four astronauts use the complex for Near Earth Asteroid missions and Mars transit and orbital missions.
The DSH itself will be “sized for Existing Launch Vehicle Systems. DSH can be broken down into smaller modular elements for EELV (Enhanced Expendable Launch Vehicle) launch and/or outfitted at ISS,” notes the presentation.
The presentation does specifically note, however, that DSH is not included for launch at this time on NASA’s upcoming successor to the Space Shuttle, the massive SLS (Space Launch System) rocket.
“SLS utilization not included but should be possible.”
The DSH can be assembled and serviced at the International Space Station, and the habitat’s propulsion and control will be provided by a docked MPCV/Orion capsule, CPS (Cryogenic Propulsion Stage), and/or SEP (Space Electric Propulsion).
Basic vehicle elements of the DSH will include the MPCV/Orion, a utility tunnel/Airlock with attached FlexCraft or MMSEV (Multi-Mission Science Exploration Vehicle), a HAB module, a CPS sized for the specific mission at hand, and an MPLM for 500-day missions.
Currently, the DHS teams are working four issues, which include the launch of existing modules on EELVs, Galactic Cosmic Radiation protection concepts, microgravity concerns, and mission integration.
DSH structures and protecting a crew in deep space:
The structures for the DSH will be ISS derived – utilizing known technologies to spur humankind’s exploration beyond Earth orbit.
This ISS derived decision is seen with DSH in the form of its STA (Static Test Assembly) configuration with a mock-up Lab/HAB module.
This STA has provided engineers with understood and known mass and fabrication materials/processes.
The same MPLM design used for Leonardo and Raffaello during the Shuttle era served as the base for the design of the MPLM to be used as part of the DSH. One notable exception to the traditional MPLM design is the addition of one more Common Berthing Mechanism (CBM), bringing the total number of CBMs for the DSH MPLM to three.
As noted by the presentation, “All ports will be CBM-sized and use ISS mass for these components. A NASA Docking System (NDS) adapter will be used for MPCV interface.”
Moreover, the connection between the MPLM and the HAB module for 500-day missions will be a special utility tunnel.
“The tunnel/contingency airlock structure mass is based on ISS airlock areal mass, is assumed to be fabricated in a similar manner. External secondary structure for radiators, meteor debris shielding and power systems are estimated at 20% of the mass to be supported.”
Should the decision be made to launch the DSH components on EELV rockets, a new launch adapter will need to be developed to connect the ISS elements.
Furthermore, just like the ISS, the DSH will need to have an ECLSS (Environmental Control and Life Support Systems).
According to the Future In-Space Operations presentation, “Mass of ISS subsystems, expendables, usage and failure rates are used in determining the mass allotments of ECLSS components and spares.”
A total of two water ISPR racks will be included in “ISS-packaged configuration” with the remaining ECLSS subsystems repackaged for the DSH. This is based on the assumption that a more light-weight arrangement for the secondary structure can be developed.
The ECLSS will provide 21 days of “open-loop contingency margin on consumables (food, water, O2) for the 60-day mission and 60 days contingency for the 500-day mission.”
This is all based on a well-characterized water balance on the ISS in both the open loop and closed loop configurations.
Moreover, thermal control within the DSH will be controlled/maintained through active waste heat collection via redundant internal and external pumped loops with cold plates and heat exchangers.
Active waste heat rejection will be accomplished through radiators – which will be “deployed, non-articulating in flight.”
On the other hand, passive thermal control will be maintained through Multi-Layer Insulation blankets on the MPLM, HAB, and tunnel pressure shells.
For crew safety and protection, external Micrometeoroid Debris Protection Shields (MDPS) will be installed on the MPLM, HAB, and tunnel adapter. These MDPSs will be derived from the shielding used on the Shuttle MPLMs.
Moreover, an interior radiation water wall will be incorporated in the DHS HAB design to protect crews from Solar Particle Events.
The water wall, in both the 60-day and 500-day configurations, will consist of a 0.55 cm thick polyethylene tank and a 9.9 cm thick water wall for a total protection rating of 11g/cm squared.
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