from: http://www.nasaspaceflight.com/2011/12/asteroid-missions-proving-grounds-future-crewed-mars-missions/
December 6th, 2011 by Chris Gebhardt
As NASA continues to define and plan for the future of human
space exploration of the solar system beyond Low Earth Orbit, the Human
Space Exploration Community’s Workshop on the GER – in cooperation with
NASA – has outlined the potential path the U.S. space agency will follow
in the build up to eventual crewed missions to Near Earth Asteroids.
The Basics: Setting the stage and making sure we’re ready:
As has always been the case with NASA, getting humankind to an asteroid will involve a phased approach beginning with
utilization
of the premiere science laboratory NASA and its international partners
have spent the last 13 years constructing in Low Earth Orbit (LEO): the
International Space Station.
According to a NASA presentation at the Human Space Exploration
Community Workshop on the GER, “Targeted utilization of the ISS to
advance capabilities needed for human exploration” is the first step in
making the “Asteroid Next” path a reality.
An initial focus on the ISS is a logical step in the process to
moving humanity beyond LEO as the science lab provides an excellent
platform for continuous learning – in both a technological and human
experience sense – for the types of long-duration missions that will be
needed to execute a mission to a Near Earth Asteroid (NEA).
However, equally as important as using the ISS will be NASA’s ability
to adequately reach and utilize the Space Station – something that will
rely on the new commercial development contracts NASA has with certain
burgeoning commercial space companies
as well as the development of NASA’s new SLS (Space Launch System) rocket.
In fact,
Commercial Crew and Commercial Cargo
Servicing and Support Systems are listed as the two most immediate and
important/decisive factors in making the “Asteroid Next” plan a reality.
But it cannot be overlooked that while commercial contracts,
vehicles, and services are deemed significantly important to the
“Asteroid Next” philosophy, so too are numerous robotic precursor
missions prior to 2020 on the part of the NASA, JAXA (Japan Aerospace
Exploration Agency), ESA (European Space Agency), CSA (Canadian Space
Agency), and Roscosmos (the Russian Federal Space Agency) – some of
which are already in flight and some of which have yet to launch.
In fact, these five major space agencies are all on track to complete
NEA fly-bys and samplings before the end of the decade, missions that
would eventually lead to two robotic precursor missions to two NEAs in
2024 and 2027.
If the development side of the equation does in fact come to fruition
(from a vehicle, technology, and precursor standpoint), the “Asteroid
Next” presentation
demonstrates an ability to launch the first crewed NEA mission by 2028.
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Phase I: ISS utilization and initial capability development/demonstration:
Under this first phase of the plan, which would begin in 2012 and
continue through 2019, the development of the technology and knowledge
necessary for NEA missions would be created both in orbit on the ISS and
on the ground.
For
the ground side of development, significant resources would be devoted
to the development of the next generation of space vehicles,
including the SLS rocket, a new Russian rocket, an Exploration Test Module, and robotic servicing and support systems.
Specifically, the presentation outlines
NASA’s SLS rocket, the
Orion Multi-Purpose Crew Vehicle
(MPCV), Roscosmos’s Next Generation Space Launch Vehicle, Roscosmos’s
Next Generation Spacecraft (“Crew vehicle capable of delivering a crew
to exploration destination and back to Earth” – 500mb of Russian
documentation available in L2), and a new Cryogenic Propellant Stage
(CPS) – an “in-space stage that provides delta V to architecture
elements using traditional chemical rocket engines, cryogens, and
storables and may include the capability for propellant transfer.”
Moreover, the presentation also outlines the Servicing Support
Systems, defined here as “systems and tools to enable crew and robots to
service in-space systems and assemble larger capabilities, including
extravehicular activity suits.”
Under this plan, the “Mission Scenario: Asteroid Next” presentation
notes that “advancing in-space habitation capability for long duration”
missions, developing “Subsystem high reliability and commonality and
advanced extravehicular activity and robotics capabilities,” as well as
developing “long-term storage and management of cryogenic fluids”
technologies are all necessary in the coming decade to accomplish a 2028
crewed NEA mission.
Moreover,
in the arena of in-space technology development, the presentation
specifically notes the Deep Space Habitat, an “in-space habitat with
relevant subsystems for the purpose of advancing capabilities and
systems requiring access to a deep space environment.”
Also beginning the development process at this time would be the
Advanced In-Space Propulsion Stage – a “nontraditional propulsion
technology, such as high-power electric and nuclear propulsion” that
would eventually be used in place of traditional chemical propulsion to
deliver crew and In-Space Destination Systems (“systems [that] have the
capabilities that enable humans to effectively complete in-space
destination objectives by enabling access”) to NEAs.
This stage of the developmental process would also include
“technology demonstrations” on the ground and in orbit from 2012-2017
leading up to the launch of the Exploration Test Module in 2018.
This Exploration Test Module would then be the host of at least three
crewed mission in 2020 and 2021 via the SLS and MPCV. These three
missions would be designed to fundamentally increase our knowledge of
human living outside of Low Earth Orbit and develop our robotic
capabilities.
Phase II: Cis-Lunar servicing and deployment:
Following the first stage of the plan, the second phase would see
crewed missions to the Exploration Test Module in the initial years of
the 2020 decade.
As related by the “Asteroid Next” presentation, these mission would
be “In-space habitation for long durations in the appropriate radiation
environment” to gain further knowledge and information on “radiation
protection and measurement techniques; demonstration of beyond Low Earth
Orbit re-entry speeds; subsystem high reliability and commonality [and]
repair at the lowest level [while] living without a supply chain” –
something which is extremely important for eventual multi-month/year
missions away from Earth.
Additional
milestones for this phase of “Asteroid Next” include development and
activation of “Automated delivery and deployment of systems, long-term
storage and management of cryogenic fluids, and simulations of
near-Earth asteroid mission operational concepts.”
Moreover, the Exploration Test Module would quickly be replaced by
the Deep Space Habitat (DSH) to be launched by the SLS rocket and
delivered to the Earth-Moon 1 Lagrange point – which gives the added
benefit of practicing operations in a gravitationally null point in the
Earth-Moon system.
For the DSH, a total of six crewed mission would be planned. While
the missions would be tailored in terms of duration to fit specific
mission requirements, opening assessments point to an initial 2023
flight to the DSH lasting 14 days with 4 crew members.
This would be followed by an un-crewed resupply mission to DSH by the
SLS rocket in preparation for a second crewed mission the following
year. This second crewed mission would also fly with 4 people and last
for 30 days. The third mission would be flown a year after the second
and consist of a 60-day mission with four crewmembers.
The next year would see a four-person crew staying for 90 days at the DSH before a 180-day mission the following year.
This would all lead up to a full year (365-day) mission to DSH in the sixth year.
Under this plan, six crewed SLS rockets would be needed, as would two
cargo SLS rockets and two resupply SLS rockets. The missions would
result in 739 days of crewed habitation on the DSH.
However, the option would also exist to execute a myriad of missions.
As noted by the “Asteroid Next” presentation, “Multiple options
available for crew duration depending on the type and number of cargo
launches committed to support resupply for increasing mission duration.”
In all, the option exists to conduct five 30-day missions followed by
a 365-day mission (resulting in 515 days of crewed habitation at DSH
and two SLS resupply rockets); a 30-day, 90-day, 180-day mission
followed by three 365-day missions for a total of 1,395 days of crewed
habitation with three SLS resupply rockets and a total of 11 SLS
launches; or six straight 365-day missions resulting in 2,190 days of
crewed habitation at DSH, four SLS resupply missions, and 12 total SLS
rocket launches over six years.
Simultaneous
to the crewed missions to DSH would be two robotic precursor missions
to the NEAs that would be targeted for the crewed NEA missions.
As noted by the “Asteroid Next” presentation, “Some NEAs are solid,
some are an aggregation of particles, and all rotate at various rates.
Precursor robotic missions to the eventual human mission targets will
allow us to refine destination systems performance that will be required
to explore the chosen NEA.”
Under this plan, the robotic precursor mission would arrive between
three to five years ahead of the crewed mission so that mission
planners, engineers, and scientists could discuss and examine any and
all options, system designs, and scientific experiments that would need
to be in place for the follow-on crewed mission.
In particular, these robotic precursor missions would be sent to
identify precise “orbital position, system type (e.g. binary or
ternary), spin rate, debris field, internal structure, near-surface
structure and regolith, gravitational field, mineralogical/chemical
composition, thermal properties, and radiation environment” – all
necessary items to have cataloged before the arrival of humans.
At this point, the stage would be set for a crewed mission to a NEA.
Phase III: Deep Space Exploration:
With Phase III comes fruition. During this phase of operation, humankind would make its first two crewed trips to NEAs.
Under
this part of the “Asteroid Next” philosophy, demonstrations of
“in-space habitation capability for long durations and advanced in-space
propulsion systems” would be tested – knowledge and technologies that
would eventually be used to take humans to Mars.
In addition, a continued focus on “long-term storage and management
of cryogenic fluids, automated delivery and deployment of systems,
subsystems high reliability and commonality [and] repair at the lowest
level [while] living without a supply chain, and demonstration of Mars
mission transportation operational concepts” would be had.
Under this plan, the first crewed mission to a NEA would begin in
2028 and conclude around 2030, with the second crewed NEA mission
beginning in 2033 and concluding in 2035.
During the missions, the crews would spend approximately seven, 14,
or 30 days at the NEA of choice, conducting surface EVA missions to
deploy “probes (radar, acoustics, seismometers, etc.), experiments, and
planetary defense devices.”
These surface missions would be accomplished with small utility craft
while the main “mothership stack” – consisting of the In-Space Enhanced
Propulsion unit, the DSH, and the MPCV – remained at a standoff
distance from the NEA of approximately 1-2 kilometers.
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