Inspired by Did any of the Apollo lunar modules land significantly off level? I'd like to know if there is an inclination limit for the Artemis Human Landing System?


1 Answer 1


Ugh, you made me look at NASA requirements documents.


HLS-R-0071 Landing Site Vertical Orientation

The HLS shall provide vertical orientation of 0 to 8° (threshold) and 0 to 5° (goal) from local vertical for surface operations.

Rationale: The HLS must support all post-landing crew activities. It is expected that the slope tolerance (landed stability) of the HLS will exceed the acceptable lander tilt angles for the safe and effective execution of critical crew functions during the lunar surface mission. As a result, some means of tilt mitigation may be required. Critical crew habitation operations impacted by lander attitude include EVA suit don/doff, EVA suit undock and re-dock to donning stand, IVA mobility, eating, sleeping, hygiene, as well as operation and maintenance of equipment. Critical EVA operations impacted by lander attitude include hatch ingress/egress, lander “deck” activities (e.g. dust mitigation), descent element platform translation between the hatch and the ladder, ladder descent/ascent, transition between the ladder and the lunar surface, transport of tools/equipment to the lunar surface, access to externally stowed tools/equipment, transport of lunar samples/sample containers to the ascent element, and assistance to impaired or recovery of an incapacitated crew member (e.g. rescue from the surface to the interior of the ascent element).

Emphasis mine.

It boils down to, if the surface tilt exceeds the stated limits, the vehicle will have to be able to level itself somewhat. The "slope tolerance" does not seem to be known yet. So for a non-self-leveling vehicle, those would be the slope limits.

Source is available here but you have to download and extract the zip file

  • 5
    $\begingroup$ re "Ugh", it's a tough job but somebody's got to do it :-) $\endgroup$
    – uhoh
    Commented Sep 15, 2020 at 0:29

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