Table 2.

Updated design reference missions currently in use by the Human System Risk Board.

DRM Categories	Mission Type and Duration	Gravity Environment	Radiation Environment	Vehicle/Habitat Design	Distance from Earth		EVA Frequency
					Evacuation	Communication
Low Earth Orbit	Short ( < 30 days)	Microgravity	LEO – Van Allen ( < 5–15 mGy)	Mid-sized volume, resupply	1 day or less	Real-time	1–4 EVAs
	Long (30 days–1 year)	Microgravity	LEO – Van Allen (5–150 mGy)	Mid to large optimized volume, resupply	1 day or less	Real-time	1–10 EVAs
Lunar Orbital	Short ( < 30 days)	Microgravity	Deep Space – Van Allen (15–20 mGy)	Small volume, self-contained, resupply	3–11 days	Real-time	Contingency EVA only or very few EVAs
	Long (30 days–1 year)	Microgravity	Deep Space (175–220 mGy)	Mid-sized volume, self-contained, limited resupply	3–11 days	Real-time	Contingency EVA only or very few EVAs
Lunar Orbital + Surface	Short ( < 30 days)	Microgravity & 1/6 G	Deep Space – Van Allen (15–20 mGy)	Small volume, resupply	3–11 days	Real-time	5 EVAs, some back-to-back
	Long (30 days–1 year)	Microgravity & 1/6 G	Deep Space (100–120 mGy)	Mid-large sized optimized volume, limited resupply	3–11 days	Real-time	3-4 EVAs per week, 20–24 EVA hours per week
Mars	Preparatory ( < 1 year)	Microgravity	Deep Space (175–220 mGy)	Mid-sized optimal volume, limited resupply, closed loop environment	Days-weeks	Controlled - Delayed	Contingency EVA only or very few EVAs
	Mars Planetary (730–1224 days)	Microgravity & 3/8 G	Deep Space - Planetary (300–450 mGy)	Mid-sized optimal volume, no resupply, closed loop environment	Mission duration	No real-time	2 crew x 8 h EVA x 20 EVA days

EVA Extravehicular activity; LEO Low Earth orbit.