NASA Exploration Roadmap: The evaluation of crewed missions to Asteroids

by Chris Bergin

Classed as one of the defined destinations for NASA astronauts in the mid to late 2020s, missions to a Near Earth Asteroid (NEA) – utilizing the Space Launch System (SLS) – have received a level of technical evaluation via the Exploration Systems Development Division (ESD) Concept Of Operations (Con Ops) document, which overviewed the Initial, Advanced and Full mission capabilities.

Crewed Missions to NEAs:

The concept of sending NASA astronauts to an asteroid has been the subject of numerous meetings, powerpoints and CGI videos over recent years, especially since the end of the “Moon, Mars and Beyond” Vision for Space Exploration (VSE) roadmap for the defunct Constellation Program (CxP).

The most notable realignment to installing NEA missions into the forward plan came via the post-Augustine Commission “Flexible Path” approach – citing robotic precursor missions, prior to a long duration, deep space mission for a NASA crew.

In the Flexible Path presentation (acquired by L2 – Link), a mission to Near Earth Object 1999AO10 is outlined, requiring a launch date of January 2, 2026.

The NEO 1999AO10 deep space mission would last 155 days, around half of the mission length for the other candidate mentioned – 304 days – for NEO 2001 GP2.

Also see’s Flexible Path Review:
Part 1: Battle of the Heavy Lift Launchers – Monster 200mt vehicle noted
Part 2: Manned mission to construct huge GEO and deep space telescopes proposed
Part 3: NASA Flexible Path Evaluation of 2025 human mission to visit an asteriod
Part 4: Taking Aim on Phobos – NASA outline Flexible Path precursor to Man on Mars

A more recent NEA evaluation, named in 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 what would be a 2028 crewed NEA mission.

While a mission to a NEA is itself is a well-known primary target for NASA’s deep space aspirations, no actual NEA destination or timeline has yet been determined.

It is hoped an expansive roadmap is just a few weeks away, with March documentation showing April is the month when former Space Shuttle Program (SSP) manager John Shannon – who is leading the roadmap effort – conducts an Agency outbrief, to be followed by the “180 Day Exploration Destination Report”. (See L2’s Exploration Roadmap Update Section – L2 Link).

Such a timeline ties into the completion of ESD’s work on the Design Reference Missions (DRMs) relating to crewed missions to Mars – namely its two moons, the final stage of a Con Ops drive within the Exploration Systems Development Division.

As outlined in the previous ESD Con Ops article, the opening missions involving SLS and Orion are more or less set in stone (Exploration Mission -1 and -2), as much as the December, 2017 launch date for SLS-1 is the only firm target on the manifest.

With a potential return to the surface of the Moon – named as a Lunar Surface Sortie (LSS) – now acknowledged as a possibility by NASA administrator Charlie Bolden during this week’s hearing with lawmakers, a large gap of around 10 or more years requires mission content to be installed into the roadmap, based on the assumption of a potential lunar mission in the first half of the 2020s and the mid 2030s timeline of the opening Mars missions.

That period is highly likely to be filled with NEA content, with the ESD Con Ops outlining three versions of such missions, based on capability – namely Initial, Advanced and Full capabilities.

Cited under the Strategic Timeframe DRMs, the Initial Capability Near Earth Asteroid (NEA) involves a “Crewed mission to a NEA using a minimal set of elements to perform a limited set of destination objectives,” according to the ESD Con Ops presentation – (available on L2 – Link).

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“Expected drivers include: number of days for Orion MPCV quiescent operations, RPOD (Rendezvous, Proximity Operations and Docking), interfaces with another element (DSH) to support MPCV quiescent ops phase,  Orion MPCV delta V/ prop quantity due to pushing DSH (Deep Space Hab).”

The Deep Space Hab (DSH) is a major element of a NEA mission, providing a mobile base of operations for the astronauts to live and work in during their long duration deep space mission. (An article will be forthcoming on the latest evaluations into the DSH via an expansive March 14, 2012 presentation acquired by L2 – Link).

“Deep Space Habitat (DSH):  Pressurized environment for longer durations missions where crew live and work both while in transit and at exploration destinations,” outlined the Con Ops presentation. “Includes all crew support resources and carries additional supplies and spares for the rest of the stack. Can be divided into separable pressurized volumes, with each section having at least one docking port”

Even on this Initial Capability NEA mission, an additional element of hardware would be required, know as the Robotics and EVA Module (REM), as outlined in the Con Ops document.

“Robotics and EVA Module (REM): Infrastructure for extravehicular human and robotic operations, transportation element maintenance and repair, movement of equipment and payloads, anchoring or tethering of external bodies, extraction of cargo, and deployment of payloads in Earth orbit for independent entry. It is constructed to be an “add on” airlock to other destination elements.”

This mission would involve two SLS Block 1A 105mt capable Heavy Lift Launch Vehicles (HLVs), with the first launching the DSH and REM into orbit, where they would wait for a minimum of 121 days prior to the second SLS launching additional hardware and the Orion and Earth Departure Stage (EDS).

As cited by the Con Ops presentations, 120 days is currently the minimum launch spacing capability assumed for multi-launch DRMs.

The crew of four on the Orion would then conduct a mission of 369 crewed days, 14 of which would be at the NEA destination.

Under the Con Ops’ Architectural Timeframe DRMs, the Advanced Capability NEA: “Utilizes a larger suite of spacecraft elements compared to Initial NEA to achieve close proximity to NEA and perform surface objectives. Expected drivers include: number of launches, MPCV return delta V, RPOD, long MPCV quiescent duration, and potentially increases SLS capability to 130 mt (depending on NEA target).”

With reference to the 130mt Block II SLS, such a mission would not be before the late 2020s at the very earliest – based on the expected availability of the fully evolved SLS – likely explaining why this is one of two NEA mission capabilities listed under Architectural Timeframe.

This particular mission would involve a total of three SLS HLV launches, with the first Block IA 105mt SLS launching the DSH and REM, the second Block 1A launching no sooner than 121 days later with a Block 2 Cryogenic Propulsion System (CPS) – although no specific payload is listed – followed by the fully evolved SLS, including Orion and the crew, launching no sooner than 241 days after the first SLS.

A total of 604 mission days would be involved from the time the first SLS launches, through to the End Of Mission (EOM), with 364 crewed days including 14 days at the NEO destination.

The third capability option is understood to be the current favorite, not least because it does not require the Block II SLS, but also because it is the only option that cites the increasingly favored Solar Electric Power (SEP) and the use of the Space Exploration Vehicle (SEV).

“SEV Provides habitation during transit, serves as an excursion spacecraft at mission destinations, provides a robotic and robot-assisted exploration capability, and enables simultaneous EVA capability for two crew members,” outlined the Con Ops presentation.

“(This is a) modular vehicle that combines a pressurized cabin and crew support equipment, a propulsion/consumables unit, and robotic support packages.”

The use of SEP has been cited in numerous presentations of late, ranging from the L2 Gateway Exploration Platform, through to deep space exploration missions.

“SEP provides sustained low-thrust propulsion for long duration, deep space missions, using Hall Effect Xenon (Xe) thrusters. Large solar arrays provide power to the SEP  and other docked systems,” added the Con Ops overview.

“Also includes a Xe feed system, thermal management, power processing/ switching, gimbals and control, reaction and attitude control systems, communication and core bus components.”

This mission capability involves three SLS Block 1A 105mt HLVs to loft the hardware into orbit, opening with the first SLS launching with the DSH, the SEP hardware, and a kick stage – resulting in a SLS Payload Insertion Mass of 97 mt.

However, according to the Con Ops presentation, the second SLS Block 1A launch would have to wait an incredible 647 days before it launches with its Block 2 CPS and SEV, with the crew following on their Block IA SLS/Block 1 CPS and Orion a full 771 days after the first SLS launch.

This results in a mission campaign lasting 1199 days in total, with 364 days for the crew, for a mission at the NEA destination of 14 days.

“Full Capability NEA: Employs chemical and solar propulsion (SEP element) to reach a NEA, where a SEV is used as a free flying destination system to achieve more exploration objectives,” added the presentation. “Expected drivers include: number of launches, need for multiple SLS cargo configurations, RPOD, number of MPCV ‘quiescent docked’ days, MPCV return velocity.”

While evaluations into the obvious requirements of keeping a crew alive and healthy during such long duration deep space missions is an obvious challenge, NASA teams are already training for the actual mission at the NEA destination.

These efforts are being conducted by the NASA Extreme Environment Mission Operations (NEEMO) team, who are heading into their sixteenth mission this coming June, simulating NEA missions at the underwater habitat in Key Largo, Florida.

With submersibles acting in the role of the SEV, and former astronauts on the dives, teams are practising techniques and the use of tools – even the time delays between mission control and the crew in deep space – laying a set of initial procedures for the eventual missions to an actual asteroid.

(Images: Via 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. Other images via Boeing and NASA)

(L2 is – as it has been for the past several years – providing full exclusive SLS coverage.  To join L2, click here:

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