Q&A: Lunar Surface Aborts to NRHO

[sdsds]

With the emphasis placed recently on crew safety for Artemis 2, there has been remarkably little commentary on risks associated with the Artemis 3 (and following) missions to the lunar surface.

Background: for Apollo surface missions the CSM stayed in an LLO making regular passes near the spot where the LM had landed, with station-keeping costs low since the duration of the surface stay was short. For CxP, Orion was tasked with station-keeping in LLO over the surface location for the duration of a 7-day sortie mission. In each case the vehicle in LLO provided a near-anytime abort haven for the crew on the surface.

For Artemis no haven asset is circling in LLO. Orion (and maybe Gateway) provide the nearest haven, and they're in NRHO.

The minimum delta-v cost from the surface to the Artemis NRHO varies with time, depending on where within the NRHO cycle the rendezvous takes place. For a given delta-v budget there's also a correlation between time of ascent from the surface and time in flight to the haven.

The nominal plan calls for HLS to undock and depart NRHO ~0.5 days before perilune. HLS then lands on the surface just about when Orion reaches perilune. The return to NRHO begins ~6.5 days later when Orion is back near perilune. HLS takes ~0.5 days to make rendezvous as Orion is heading back up towards apolune.

The timing for shortened surface stays looks awkward. With constrained delta-v, rendezvous at apolune requires ~3.25 days in transit. That's less than ideal for some contingency situations.

Given Artemis 3 is nominally scheduled for 2026 surely someone at NASA has put some thought into the mission abort scenarios?

[whitelancer64]

Yes, lunar surface to NRHO abort scenarios are constrained by orbital dynamics.

Discussed in this presentation from 2022, starting on page 37

PDF attached.

source: https://ntrs.nasa.gov/api/citations/20230002566/downloads/HLS%20NRHO%20to%20Lunar%20Surface%20and%20Back%20Mission%20Design_STRIVES.pptx.pdf

[sdsds]

PDF attached.

Wow, that's an impressive slide deck; thank-you for bringing it to the discussion here! Clearly EG5 is doing their homework. FWIW:

Flight Mechanics and Trajectory Design Branch, Aeroscience and Flight Mechanics Division
Engineering Directorate, NASA / Johnson Space Center

"The Flight Mechanics and Trajectory Design Branch (EG5) is responsible for the design and evaluation of reference trajectories and flight vehicle performance capabilities for all missions assigned to JSC."

Lots more reading material out there:
  https://www.google.com/search?q=%22EG5%22+%22JSC%22

[sdsds]

Ooh! They're thinking about this stuff.

Abort Trajectory Design Strategies for the Artemis Missions
Brian McCarthy, Josh Geiser, et al.
August 11, 2024

https://ntrs.nasa.gov/citations/20240011644