FLEX

NASA/James Blair. Public domain (NASA / US government work).

Overview

FLEX, Flexible Logistics and Exploration, is an unpressurized four-wheeled lunar rover built by Venturi Astrolab of Hawthorne, California. It carries two suited crew, accepts modular payloads at multiple quick-disconnect interfaces, and can be driven by an onboard crew, teleoperated from Earth, or run under supervised autonomy [7]. A full-scale terrestrial prototype was built and field tested before the flight design was frozen. The flight configuration selected by NASA in May 2026 is designated CLV-1 and is derived from the FLEX architecture [8].

Astrolab is the prime. Venturi Space supplies the wheels, batteries and battery management system; Axiom Space, Interlune and Odyssey Space Research are named team members [8]. NASA’s own 2025 survey of in-space servicing, assembly and manufacturing capability lists FLEX among the vehicles built to carry science and logistics payloads on the lunar surface, an independent confirmation of the payload-carrying architecture from outside the vendor’s own materials [6].

Almost every vehicle figure below comes from manufacturer documentation [7], [8], [9], [11] rather than a reviewed publication, and the source column says which. The NASA papers cited [1], [2], [3] describe the government reference LTV design or the LTV requirement set, not the Astrolab vehicle.

Specifications

Parameter	Value	Source
Crew	2 suited astronauts	manufacturer [7]
Maximum vehicle mass, CLV-1	950 kg	manufacturer [8]
Stowed envelope	2.0 x 2.3 x 2.2 m
Deployed envelope	4.0 x 2.3 x 2.6 m to antenna top
Top speed, level ground	10 km/h
Wheel diameter	930 mm	manufacturer [9]
Wheel life specification	at least 1000 km
Wheel temperature specification	-240 to +130 degrees C
Cargo delivery capacity	1600 kg, 3 cubic meters	manufacturer [7]
Solar array area	3 square meters	manufacturer [7]
Robotic arm	6 DOF	manufacturer [7]
Night survival	yes, by heated battery enclosure	manufacturer [11]

No reviewed publication gives a full mass, power or payload breakdown for FLEX. The manufacturer’s own product materials are themselves sparse: beyond the figures above, Astrolab states no payload mass limit, power budget or structural load figure for the vehicle’s payload interfaces [7].

Mission profile

The following describe the flight assignments, not the vehicle.

Parameter	Value	Source
Contract	Lunar Terrain Vehicle Services, Phase 1 High Achievability Mission task order	[8], [10]
Task order value	approximately $219 million
Parent IDIQ	up to $4.6 billion, awarded 2024, 13 years plus 2	[8]
Surface arrival	no earlier than 2028	[8], [10]
Landing site class	lunar south pole	[10]
Precursor flight	FLIP on Astrobotic Griffin-1, Nobile region	[11], [12]

NASA awarded LTVS Phase 1 task orders to Astrolab at approximately $219 million and to Lunar Outpost at approximately $220 million, with delivery to the surface anticipated by 2028 [10]. The stated near-term plan is that over 18 months the providers finalize rover designs, conduct crewed evaluations, and qualify flight units. The NASA release restates CLV-1 as having a mass of about 2000 pounds and the ability to exceed 6 mph on level terrain, consistent with the 950 kg and 10 km/h given by Astrolab [8].

FLIP, the FLEX Lunar Innovation Platform, is a smaller vehicle of approximately 450 kg carrying up to 30 kg of payload, manifested on Astrobotic’s Griffin-1 lander to the Nobile region of the south pole [12]. It flies full-size FLEX batteries, tires, avionics, sensors and software, so its purpose is subsystem qualification for FLEX rather than an independent program [11].

Requirements the vehicle is built against

The LTV requirement set is published in NASA papers even though the Astrolab design against it is not. The 2021 request for information asked for a vehicle that survives an extended lunar night of at least 85 hours and 125 hours if achievable, fits a CLPS-class lander, accommodates a driver and a passenger in EVA suits, carries a total payload mass of at least 800 kg for as much as 20 km without recharging, is available at least 8 hours per Earth day outside night periods, survives south polar and permanently shadowed region temperatures of 50 K, has an operational life of at least ten years, and can be operated remotely [3]. Two numbered system requirements appear in the teleoperation study: LTV-SYS-071 sets 6 km as threshold and 8 km as goal for distance covered in one 24 hour period under remote operation, and LTV-SYS-029 requires no less than 20 km without stopping to recharge [1]. A separate NASA thermal analysis states a required top speed of at least 15 km/h [2], which the manufacturer figure of 10 km/h for CLV-1 does not meet [8]; the two documents describe different design generations and no source reconciles them.

Mobility

FLEX uses a wheel-on-limb architecture in which each of the four wheels is carried on an articulated limb. Astrolab describes the limbs as leveling the chassis, absorbing impacts at speed, changing ground clearance, and picking up and setting down payloads directly, without a separate lifting mechanism [7]. Astrolab’s own materials give no quantified figures for limb travel, load capacity or actuation, so the architecture is stated here only as description, not as specification.

The wheel is a Venturi Space design, 930 mm in diameter, built from 192 cables acting as spokes, an outer rim carrying springs, and a flexible tread of a material developed for the application [9]. It is specified for at least 1000 km of travel and for surface temperatures between -240 and +130 degrees C on a vehicle traveling at 15 km/h. The wheel was presented publicly in June 2023.

Wheel thermal behavior on a lunar rover is dominated by radiation rather than by contact with the regolith. In the NASA government reference LTV analysis, wheel temperatures over a full summer day at a highly illuminated Connecting Ridge site ranged from 240 K to 420 K against a maximum far-field regolith surface temperature near 114 K, and the temperature profile was insensitive to the assumed wheel-to-regolith conductance because the low conductivity of the regolith itself is the choke point [2]. Peak conducted heat loss was 12 W from a single wheel and 37 W from all four. Sinkage for that reference design was computed at 1.1 cm, against 1.3 cm measured in the Apollo 15 LRV tracks [2]. The exception is a traverse into a permanently shadowed region, where the rolling contact patch continually meets fresh 25 K regolith: over a 2 hour traverse at maximum speed the predicted mean wheel temperature ranged from 264 K at an assumed contact conductance of 0.1 W/K down to near 25 K at 100 W/K, with total energy transfer asymptotic to about 12,000 kJ above 10 W/K [2]. That paper states no test-verified method exists to derive the conductance analytically and that a thermal vacuum measurement against rotation speed, loading and temperature is required. Aluminum 7075 in the reference wheel carcass gains yield strength at cryogenic temperature and loses fracture toughness [2]. The Venturi cable-and-spring wheel is a compliant structure of the class that paper flags as hard to model, because conduction between contacting non-welded strands in vacuum depends on contact pressure and area, and radiating area must be reduced for the gaps. No published measurement of the Venturi wheel against these effects was located.

The only flown baseline for wheeled lunar mobility is the Apollo LRV, and it sits well below FLEX’s stated figures: 2 to 3 percent wheel slip, a cruise speed of 6 to 7 km/h against FLEX’s 10 km/h top speed, a maximum negotiable slope of 19 to 23 degrees, and an energy cost of 35 to 56 watt-hours per km, of which only about 15 percent went into the soil rather than the vehicle and its occupants [4]. The LRV numbers come from six equatorial Apollo sites on a wire-mesh wheel; nothing in that record bears on the higher speed, south polar terrain or cable-and-spring wheel FLEX is specified against.

The governing NASA cross-program environment specification sets lunar regolith ultimate bearing capacity at about 6000 kPa under a 1 m footing and equatorial surface temperature extremes of 391 K at local noon against 96 K before sunrise [5], figures that describe what a lunar surface vehicle is required to be designed against rather than anything measured on FLEX itself. No published source states the Venturi wheel’s contact pressure against that bearing capacity limit.

Power and energy

Generation is a deployable solar array of 3 square meters that tops up internal batteries [7]. Battery capacity in watt-hours is not published. Batteries and the battery management system come from Venturi Space [8]. The batteries sit in an enclosure built to hold them inside their operating range across the surface temperature swing, and it is that enclosure that the manufacturer identifies as the enabler of lunar night survival [11].

Battery minimum operating temperature is the sizing parameter for heater power on a vehicle of this class. The NASA thermal design study defines the critical component as the one with the highest minimum operating temperature, states that this is usually the battery, and takes 0 or -10 degrees C as the assumed limit from which worst-case cold heater power follows [3]. Cells qualified to operate colder reduce thermal management mass directly, because both battery size and heater count fall.

Thermal

Surviving the night is the dominant thermal case. Lunar surface temperature at the south pole reaches 300 K in daylight and 50 K at night, most nights at a given site last about 36 hours, and NASA analysis indicates a vehicle would see at least two extended nights of at least 85 hours per year, extending to 125 hours if stationary [3]. Radioisotope heater units were considered for the reference design and were constrained by Department of Energy material control, by units not being in production, and by CLPS launch licensing that has no precedent for radioisotope payloads.

Astrolab publishes no thermal architecture for FLEX beyond the battery enclosure [7], [11].

Compute and avionics

No processor, flight software framework or avionics architecture has been published for FLEX. FLIP carries flight avionics, sensors and software ahead of FLEX for surface qualification, which is the only stated link between the two vehicles’ avionics [11].

Autonomy

The published autonomy level is supervised, driving to operator-selected waypoints with onboard hazard avoidance [7]. Sensors for hazard avoidance are stated to exist but are not enumerated [7].

Teleoperation performance under lunar communication latency has been measured by NASA on a government reference LTV in simulation. Average speed across all operators and terrain scenarios fell monotonically with delay [1]:

One-way communication delay	Average speed	Time to cover 20 km
0 s	3.24 km/h	6 h 10 min
4 s	2.56 km/h	7 h 49 min
6 s	2.03 km/h	9 h 51 min
8 s	1.76 km/h	11 h 22 min

Values from [1]. Operators braked more frequently under latency, and subjective workload rose against the zero-delay case with mental demand, frustration and performance as the contributing factors. Driving strategy was uniform across operators at zero delay and diverged into three distinct strategies at 4 s [1]. Operators received about 30 minutes of familiarization before each run, and the simulation provided an operator-selected rate limiter on the hand controller and a predictive circle. Teleoperated average speeds of 1.76 to 3.24 km/h are a fraction of the 10 km/h vehicle top speed [8], so the binding constraint on remote traverse rate is the operator and the link rather than the drivetrain.

Communications

A gimballing high-gain antenna provides direct-to-Earth communication [7]. Bands, data rates and relay arrangements are not published.

Payload interfaces

Astrolab states that FLEX takes modular payloads at quick-disconnect interfaces and that the vehicle can dock to a payload robotically, pick it up, carry it and set it down elsewhere, including relocating items too large for one vehicle by having multiple rovers cooperate [7]. No published, reviewed source gives payload mass limits, structural load figures, connector specifications or arm interface loads for these interfaces: the one manufacturer document that specified them in detail is held only as a corrupted file and cannot currently be read, so those figures are not reported here.

Modes of operation

Three driving modes are published: crew driving from the onboard crew station, remote teleoperation from Earth, and supervised autonomous navigation to operator-selected waypoints [7]. The crew station is itself a removable top-deck payload, so the crewed and uncrewed configurations differ by a payload exchange rather than by vehicle build [7]. Survive-the-night is a distinct state in which the vehicle is dormant with the battery enclosure held above its minimum operating temperature [11].

Ground operations

No operations concept, control center or planning cycle has been published for FLEX. The NASA teleoperation studies establish the operator-side envelope the ground system has to work within: single-operator remote driving is viable through 8 s of one-way delay with a rate limiter and a predictive circle in the display, at the cost of speed and workload [1]. Crewed evaluations of the vehicle have been run at NASA JSC with suited subjects working the crew station, stowage drawers and payload handling [10].

Technologies developed

One product of the program is separable from the vehicle: the Venturi hyper-deformable wheel, a cable-and-spring compliant wheel specified for 1000 km and for a 370 degree C temperature span, which is a component rather than a vehicle subsystem and is being flown on FLIP ahead of FLEX [9], [11]. Astrolab also markets a payload interface intended to let landers, rovers and payloads from different vendors interoperate, but no reviewed or independently readable source describes its specification, so it is not detailed here.

What is not established

Almost every quantitative figure for FLEX comes from the manufacturer rather than from a reviewed publication, and the manufacturer’s own materials are themselves sparse: no payload mass limit, structural load, power budget, flight software architecture, processor, or communications data rate has been published for the vehicle [7]. A manufacturer document that specified the payload interfaces, arm interface loads and cargo container envelopes in detail exists but is held only as a corrupted file that cannot currently be read, so none of those figures can be reported until it is refetched and read. The government LTV design and requirement figures cited above describe a NASA reference vehicle and a requirement set, not the Astrolab vehicle, and no source reconciles the two: the LTV wheel thermal paper’s top speed requirement of at least 15 km/h is not met by the 10 km/h CLV-1 figure Astrolab publishes [2], [8]. No test-verified method exists to derive the wheel-to-regolith contact conductance the thermal case depends on, and no published measurement of the Venturi wheel’s own thermal or bearing behavior was located [2].