NASA MSFC Lunar Regolith Terrain Field and Dirty Vacuum Chambers

NASA/Joe Kuner. Public domain (NASA / US government work).

Marshall’s lunar surface testing sits in two places: an outdoor Lunar Regolith Terrain field, and a set of dirty vacuum chambers run by the Space Environmental Effects laboratory. The chambers are presented by their operator as a deliberately staged sequence rather than one flagship facility: early materials work in the Lunar Environment Test System, payload and system level exposure in PLANET, and integrated qualification in the V20 chamber, so that a concept can raise its technology readiness level by moving between the three [1].

Laboratory data

Parameter	Value
Operator	NASA MSFC, Space Environmental Effects laboratory [1]
Location	Huntsville, Alabama, United States
Commissioned	LETS operational since 2008; PLANET customer access from mid-2024
Type	Outdoor analogue terrain field and three dirty vacuum chambers
Floor area	Not published for the field or for the laboratory
Capabilities	LRT field, LETS, PLANET, V20
Simulant or terrain	Not published as an inventory. JSC-1A has been run in the LETS tray
Instrumentation	Residual gas analysis, particle imaging velocimetry, electron gun
Ground truth	Not published
Fidelity limits	No chamber spans the problem; simulant must be baked before pumping
Access	Not published for the field. PLANET customer access planned from mid-2024
Cited by	Break the Ice Lunar Challenge excavation demonstrators, tested in V20 [2]

Capabilities

Lunar Regolith Terrain field

Parameter	Value
Temperature	Not controlled. Alabama outdoor conditions [1]
Slope	Not published
Gravity offload	Not applicable. Outdoors at 1 g

Marshall’s outdoor lunar analogue site. No area, simulant inventory, bed depth, terrain preparation, buried target set, instrumentation list or support arrangement is published for it.

LETS

Parameter	Value
Working volume	76.2 cm (30 in) diameter chamber housing a regolith box
Temperature	Cryogenic shroud; range not published
Illumination	A 100 keV electron gun provides the charged particle environment
Simulant or terrain	JSC-1A in the tray, under a non-airtight cover
Instrumentation	Particle imaging velocimeter; 100 keV electron gun

Source: [1].

The Lunar Environment Test System is the smallest and oldest of the three chambers, operational since 2008 [1]. Its simulant tray has been run with JSC-1A under a non-airtight cover designed to minimize turbulent flow across the surface material during initial pumpdown. It has been used for regolith charging and lofting studies and for exposing material coupons [1].

PLANET

Parameter	Value
Working volume	2 m diameter x 3 m cylinder, domed doors both ends; bed 1.22 x 2.44 m, 0.2 m deep
Test article limits	Floor designed for roughly 1200 kg including the bed structure
Vacuum	At least the 10^-7 Torr regime empty; scroll roughing, cryopump for high vacuum
Temperature	-180 C on liquid nitrogen to radiant heating by quartz lamps
Illumination	Near and vacuum ultraviolet sources
Simulant or terrain	About 800 kg of simulant in the bed; product not published
Instrumentation	Residual gas analyzer; quartz crystal microbalance under consideration

Source: [1].

PLANET, the Planetary, Lunar and Asteroid Natural Environments Testbed, sits between the other two and is the most explicitly combined-environment of the three. It is designed to combine high vacuum, charged particle radiation with electrons from 50 eV to 100 keV and protons from 200 eV to 30 keV, near and vacuum ultraviolet, and thermal extremes from -180 C on liquid nitrogen to radiant heating by quartz lamps [1]. For comparison the lunar exosphere ranges from 10^-9 Torr by day to 10^-12 Torr at night.

The chamber is split into two zones along its length, each fed by a group of four 10 in ConFlat overhead ports focused on the test article plane at a slightly different focus height, so that a hot bright zone and a cold dark zone can be run at once to emulate the terminator [1].

V20

NASA/Joe Kuner. Public domain (NASA / US government work).

Parameter	Value
Working volume	6 m (20 ft) diameter x 8.5 m (28 ft) long
Temperature	Cryogenic shroud with radiant heating; range not published
Illumination	None. No space environments other than vacuum and thermal
Simulant or terrain	A bed large enough for full-scale hardware; product and depth not published

Source: [1].

V20, outfitted as the Lunar Surface Simulator, is the large end of the sequence: a thermal vacuum chamber at the Marshall Environmental Test Facility, converted recently as of 2023 to handle regolith and dust, with a bed that can hold full-scale hardware, outfitted with a cryogenic shroud and radiant heating but no other space environments [1]. Containing the dust at that scale is a facility problem of its own, and V20’s answer was a large clean tent around the chamber entrance. The Lunar Surface Simulator outfitting of this chamber is described only in abstracts and presentations, so no shroud zone count, temperature range, pump configuration or cart and bed dimension is recorded above.

Instrumentation

PLANET is designed around two additions of its own. A regolith application and distribution system is to meter known quantities of simulant from above a test article, so that thin layers can be deposited for later exposures or introduced periodically from a hopper for wear or additive manufacturing work; the designers call the problem non-trivial, because the most damaging particles are 10 to 20 microns across and therefore invisible to the eye, making both precision and verification hard [1]. Mechanism and seal testing for wear, abrasion and leak resistance is the other, with motion stages, load cells and sample fixturing being designed for it. Real time chemical monitoring is by residual gas analyzer, with a temperature-controlled quartz crystal microbalance under consideration [1].

LETS carries a particle imaging velocimeter and a 100 keV electron gun alongside its cryogenic shroud, which is what makes it the charging and lofting chamber of the three [1].

What it does not reproduce

Simulant that has not been baked is not the same material as simulant that has. Accepted practice across the NASA dirty chambers, PLANET included, is a thorough bakeout of the simulant above 100 C before pumping to high vacuum, to drive off adsorbed water that would otherwise boil off as the pressure falls; hotter bakes reach structural water but can change other chemical properties as well [1]. Any mechanical result taken on unbaked simulant at ambient humidity describes a different material from the one that goes into vacuum.

Pumping a granular bed is a facility problem in itself. The measures the Marshall team records for keeping simulant out of the pumps are tortuous paths, filters, placement of the pump inlet high in the chamber, a non-sealed lid over the simulant box to damp viscous and turbulent flow during rough pumping, and a preference for cryopumps over turbomachinery in the high vacuum regime, since a particle reaching a turbopump is a catastrophic mechanical failure. Those same measures cut pumping speed in the molecular flow regime [1].

Scale against fidelity. No one chamber spans the problem, which is why there are three. LETS gives radiation and charging over a tray; PLANET gives the combined environment over a 1.22 x 2.44 m bed; V20 gives room for full-scale hardware but only vacuum and thermal control, with no other space environments [1]. The stated progression is materials in LETS, payloads and systems in PLANET, integrated qualification in V20 [1].

Gravity. None of the facilities offloads. The field is outdoors at 1 g and the chambers hold their beds under Earth weight [1].

Campaigns run there

Break the Ice Lunar Challenge follow-on testing, July 2025. A rover from a Centennial Challenges finalist, second overall at the June 2024 live demonstration and finale, was installed in the V20 chamber at the Environmental Test Facility over a concrete slab it would operate on, lifted in on the rail cart by the overhead crane [2]. The Break the Ice challenge asked competitors to design, build and demonstrate robotic technologies that could excavate and transport icy lunar regolith [2].

PLANET procurement and build, 2022 onward. The vacuum system was in procurement in late 2022, with the vessel, pumps and automated controls due for delivery in late 2023, outfitting with environments and instrumentation to follow over the months after, and customer access planned from mid-2024 [1]. No published full paper found here reports the commissioning results.