As NASA continues the early development phase of its Space Launch System (SLS) rocket, contract companies of the U.S. space agency continue their push for new and innovative technologies – including Radiation Storm Shelters, Deep Space Habitats, and Solar Electric Propulsion – to be used as humankind pushes beyond the confines of planet Earth toward Near Earth Asteroids.
The Notional Plan:
Presented at the Global Exploration Workshop under the guise of an “Asteroid Mission Concept with Solar Electric Propulsion,” Boeing’s Director of Advanced Space Exploration, Mike Elsperman, presented the concept under the Global Exploration Roadmap.
Focusing near-term capabilities on “Guiding capabilities, technologies, and levering [of the] ISS,” the concept for humankind’s push into the inner solar system would eventually build to a “long-term focus [of] discovery driven and enhanced emerging technologies.”
While Mars is the ultimate goal of the new exploration roadmap for NASA and its international partners, a proposed (or “notional” as it is referred to in the Boeing presentation) phased approach for obtaining that ultimate goal has been laid out in the Boeing presentation.
Starting with capitalizing from the continued and future success of the International Space Station in Low Earth Orbit, the next step would be “Gaining the High Ground:” Human access to cis-lunar space – a concept previously revealed by NASASpaceflight.com.
This phase, which includes GEO and HEO missions (as well as lunar fly-bys and lunar surface missions), would be followed by “Into the Solar System:” Human Exploration of interplanetary space.
This phase, coupled with the next – “Exploring Other Worlds:” Access to Low-Gravity Bodies – would be the focus of the proving ground efforts of Solar Electric Propulsion capabilities as well as new deep space technologies during both “Mininal” and “Full Capability” missions to Near Earth Asteroids (NEAs).
Moreover, this would all work in tandem with or independent from the other objectives in the “Flexible Path for Exploration” proposal which only included the exploration targets and no provisionally defined timetable.
To the Asteroids We Go:
As with any mission, architecture build-up and advancement in technologies will be crucial for missions conducted to NEAs.
Specifically, a Long Duration Habitat, Radiation Storm Shelter, and High Isp Propulsion (Solar Electric Propulsion technologies will all be needed under the Boeing proposal.
Beginning in two stages (called Block 1 and Block 1a), the Long Duration Habitat (LDH) Block 1 design would be used as an ISS-EP (ISS Exploration Platform – completely different from the ISS currently in Earth orbit) at the Earth-Moon L1 point and would be derived from one of the Multi-Purpose Logistics Modules (MPLMs) from the Space Shuttle Program.
This Block 1 design would be be capable, through an Environmental Control Life Support System (ECLSS), of supporting up to three (3) people for a three (3) month time period.
During this time, replenishment of supplies for the partially closed environment would be possible via servicing missions from Earth support craft such as the Space Launch System (SLS) – as listed in the presentation.
Interfaces would include a Common Berthing Mechanism and NDS with an Airlock for EVAs.
This design would then be transferred and modified into the Block 1a design for NEA transport and support.
This NEA TransHub would also be derived from the one remaining MPLM from the Space Shuttle Program and would be capable of supporting three crewmembers for 12 months with no replenishment.
The module would have NDSs on the both ends as well as an airlock for EVAs.
According to the Boeing presentation, a internal, habitable volume of “5 – 18.5 m3 per crewmember for long-duration transit and surface habitats” would be needed to satisfy mission requirements.
For comparison, Skylab had 100m3 per crewmember, Salyut had 30m3 per crewmember, MIR had 117m3 per crewmember, and ISS has 142m3 per crewmember.
Mercury, Gemini, Apollo (LM and CM), Shuttle, and Soyuz all had/have no more than 10m3 per crewmember.
According to the presentation, “Boeing and Hamilton Sundstrand performed an extensive habitat volume study to validate assumptions on habitat sizing. Concept missions (DRMs) were used to drive out hab requirements.”
These concept missions included “ISS Exploration Platform (ISS-EP) at EML1: Man-tended; crew of 3 with surge up to 6 crew for 14 days; periodic system replenishment and NEA, Mars Transit, Mars Surface: 3 crew; varying duration; no replenishment.”
According to the Boeing presentation, “ISS experience and the addition of regenerative ECLSS has significantly altered consumables requirements from previous baselines,” thus indicating that large habitable volumes are not needed for the early phases of inner solar system exploration.
In fact, early estimates would seem to indicate, based on the preliminary Boeing presentation, that the Hab module sizes for both NEA missions and eventual Mars missions (both Mars transport Hab and Mars surface Hab) would be identical – 75m3 total.
This is due in no small part to the amazing enhancements and knowledge of the ECLSS systems needed to sustain a crew – knowledge that has been gained through the permanent habitation of the International Space Station.
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Technology enhancement via the ISS will allow current and future space exploration designers to reduce the risk associated with crew life support systems.
“ISS experience shows that increasing reliability and robustness of ECLSS systems is more important than further increasing life support loop closure,” notes the Boeing presentation.
However, all technologies under consideration for use in a NEA mission will have to be tested in a long-duration fashion in space before they can be incorporated into a vehicle design.
Thus, Boeing is looking at utilizing the International Space Station for what it can do best: be a test-bed for new technologies in a long-duration fashion.
In this case, Boeing would use the ISS as an ELCSS maturation facility, a place to “take full advantage of current ISS vehicle technology and develop competing technologies early to allow in-space maturation before exploration mission technology decisions.”
The ultimate goals of an ELCSS maturation program are defined by Boeing as: “Reducing consumables and mass/volume, decreasing crew time and increasing reliability, reducing power and waste heat, and aligning with the NASA mission framework and objectives.”
Click here for NEO/NEA Articles: http://www.nasaspaceflight.com/tag/neo/
All this work will have to be carried out in the coming years as NASA and humankind further define their research and exploration objectives with an eye on an eventual human mission to Mars.
Radiation Storm Shelter:
But protecting a crew of three from internal life support hazards in the LDH is not the only crew-protection service that will be needed on a mission to an NEA. Solar Radiation Storm protection will also be a vital aspect of any mission beyond (and to an extent, inside of) Earth’s protective magnetic field.
For the Boeing-proposed NEA mission, a Radiation Storm Shelter would consist of a “Storm shelter in hard inner core of the inflatable habitat.” This shelter would consist of “stored water and polyethylene … to line the walls of the shelter” for radiation protection for the crew.
The importance of protecting a crew from potentially dangerous solar radiation from the sun was evidenced just this week when the sun released a large solar storm that sent highly-charged particles toward the Earth.
While the particular storm this week was not cause for concern for the international crew of six onboard the International Space Station, it did highlight the need to protect future crews during missions to NEAs and Mars from these storms which can happen without much in the way of warning.
Solar Electric Propulsion:
Building from traditional chemical-based propulsion, future exploration initiatives in the inner solar system seek the creation of new and innovative approaches to solar propulsion, much the same way JAXA’s Hayabusa I and NASA’s Dawn spacecrafts have made use of ion propulsion technology to achieve their respective mission needs/goals.
Under the Boeing notional plan, Solar Electric Propulsion would be used by NASA for NEA missions – a technology also cited by Aerojet.
This new propulsion system would be gradually developed over the next 10 years, with a demonstration flight capable of readiness by 2014.
Building from prior technology and production programs, “gaseous Xe propellant management” would be the first step to the plan – a step that has been under development since the end of the previous decade and that will continue until at least the end of this year.
If all goes to plan, and funding is not an issue (which it is), a 30 kW Solar Electric Propulsion (SEP) demo spacecraft would be ready for testing and demonstrations in 2014.
This 30 kW spacecraft would be budded a Minotaur IV class Concept Bus.
If successful, a NASA docking system, Spacecraft boom, triple panel SEP module, Solar Array mast, and Alpha-joint (similar to the ISS’s Beta joint) would be developed between 2016 and 2020 – all leading to the creation of a 320 kW SEP operational spacecraft for NEA missions by 2022.
As noted by Boeing, “New large spacecraft bus supports heavy cargo and crewed missions to GEO, L-1, NEOs, and beyond. Modular system allows thrust/payload/trip time optimization of total acquisition cost.”
An intermediate 702 Class Bus is also a possibility according to Boeing. This intermediate craft would be capable of producing between 33 kW and 99 kW.
NEA mission parameters:
Under the Boeing notional plan, a 2024 NEA mission to NEA2008EV5 would depart not from Earth but from the ISS-EP at the Earth-Moon L2 (EML2) point.
Using the new SEP technology, transit from the EML2 point to the NEA of interest would take approximately 100 days with the SLS third stage used to “kick start” the stage and shorten the trip.
Investigations at the NEA would last for approximately 30 days before a ~235-day trip back to Earth for a total mission duration of roughly one year.
(Images: Via Boeing.)
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