EM-2: Orion crew to spend up to four days in Lunar Orbit
The first crewed mission of NASA’s Beyond Earth Orbit (BEO) exploration era will send a crew of four on a short vacation into Lunar orbit in 2021. Exploration Mission -2 (EM-2) will be a key test of Orion’s life support systems, following a baseline path laid out by EM-1, the uncrewed debut of the Space Launch System (SLS) and Orion duo.
With NASA’s exploration plan still being worked – and likely to remain as such due to the uncertainty relating to the Presidential election process – even these two opening missions of the new Heavy Lift Launch Vehicle (HLV) are subject to change.
However, that may be a blessing in disguise, with the current opening salvo of NASA’s return to BEO exploration providing an uninspiring, highly expensive and near-unworkable approach of launching an uncrewed Lunar mission in 2017, prior to employing the entire SLS/Orion ground support workforce to be removed from a launch processing stance for several years, ahead of repeating the initial mission, this time with a crew.
That unattractive approach is partly to do with budget-restrictions, but also because NASA’s leadership continues to be pushed and pulled between opposing political forces that both saved the HLV plan from being mothballed under the FY11 budget proposal, then heavily delayed the actual go-ahead for SLS via additional trade studies.
This leaves a scenario where NASA’s official line continues to lack any real expansion on the goals of a Near Earth Asteroid (NEA) mission in the 2025 time-frame, followed by a crewed mission to Mars in the 2030s.
However, behind the scenes, more interesting information is available, via what is known as the Design Reference Mission (DRM) work, showing a large amount of evaluation into missions that include a return to the surface of the Moon, in tandem with the continued rise in stock for constructing an Exploration Gateway at the ISS, ahead of its placement at EML-2.
EM-1 to EM-2:
Regardless of how the future exploration plan is constructed, SLS will require a validation flight, via what is known as Exploration Mission -1 (EM-1), currently targeting December, 2017.
This mission will feature the 318 feet, 70mt Block 1 SLS, utilizing two of ATK’s five segment Solid Rocket Boosters (SRBs), four RS-25Ds donated from the Space Shuttle Program (SSP), a core built by Boeing at the Michoud Assembly Facility (MAF), an avionics suite/instrument unit, a kick stage – or Interim Cryogenic Propulsion System (ICPS) mated to the Orion, with the Spacecraft and Payload Adapter and Fairing being topped off by a Launch Abort System (LAS).
The first EM-1 overview was overviewed in the SLS Master Presentation (E.5) – available on L2 (Link to Presentation) – provided a good insight into the basic mission plan – one that involves SLS lofting Orion en route to a high-apogee orbit of 975 nmi at the insertion point, followed by a Delta Cryogenic Second Stage (DCSS) conducting the Trans Lunar Injection (TLI) burn(s).
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According to the updated information in the recent Orion Concept Of Operations (CONOPS) presentation – available on L2 (Link to Presentation) – this flight of the Lunar Return Class Orion will “test critical mission elements as well as demonstrate performance in relevant environments prior to the first manned launch of the system.”
The ICPS will perform the burns to both raise the perigee to 100x975nmi and to depart towards the Moon. Orion will perform the Trajectory Correction Maneuvers (TCMs) on both the inbound and outbound legs.
The 6-10 day mission, utilizing a gross lift-off mass of 33.4 tons, will end when Orion re-enters Earth’s atmosphere at 36,750 feet per second.
“The flight test objectives are geared towards human rating of a BEO spacecraft. The mission will be designed to demonstrate integrated spacecraft systems performance prior to crewed flight. The trajectory is designed to achieve and demonstrate high speed atmospheric entry 36750 ft/s (~11.2 km/s) and to further demonstrate the MPCV prior to crewed flight,” added the CONOPS presentation.
“The objectives of EM-1 will validate ascent environments (aerodynamic, aerothermal, acoustics, shock, loads, thermal and radiation) on an SLS flight and BEO environments. Critical mission events (jettison, fairing separation, LV sep, CM/SM sep, FBC sep, chute deploy, CM uprighting and recovery) demonstrations will also be objectives of EM-1.
“The test objectives will also include deep space tracking and communications, attitude control and in-space maneuvering and integrated power and thermal.”
Technically a mirror image of the EM-1 mission – from the standpoint of the hardware used – EM-2 will not only add a human crew into the mix, it will also involve a longer stay in the vicinity of the Moon, via numerous orbits.
Classed a mission for “up to” four crewmembers, the Design Reference Mission (DRM) is classed as CLO (Crewed Lunar Orbit), given the astronauts will spend three to four days orbiting our nearest neighbor.
“A high lunar orbit 540-1620 nmi (1000-3000 km) is used because the Orion is performing both the Lunar Orbit Insertion (LOI) burn and the Trans-Earth Injection (TEI) burn and MPCV does not have sufficient propellant to enter into a low lunar orbit,” the presentation noted.
“The Orion will remain in lunar orbit for several days, after which the Orion will perform a TEI burn and begin the return to Earth.”
This mission’s main objectives include one of the more challenging aspects of BEO missions, the life support system. It will also validate crew operations on the Orion.
Currently, the launch is scheduled for 2021, although Orion managers have noted they are aiming to improve on that date.
SLS-3 in 2022 is also undefined, but could become the first Exploration Gateway related mission, with the HLV’s main role for the construction of the platform understood to be centered around the launch of the Solar Electric Propulsion (SEP) hardware that will send the constructed set of modules out to EML-2.
The construction of the Exploration Gateway – if approved – would become the main enabler not only for NEA missions, but also for a potential inclusion of Lunar surface missions. Its construction at the ISS could also include both existing and international launch vehicles and hardware.
Several other changes to the overall plan have also been touted, including using the Block 1 SLS in its cargo configuration for a launch inbetween EM-1 and EM-2 – although no reference to the potential payload has been made at this time.
The lack of defined payloads is one of the main criticisms opponents cite in reference to the SLS.
(Images: Via L2 content from L2’s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site. Other image via NASA)
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