TRIDENT

Source: [1], CC BY 4.0.

Overview

TRIDENT is a 1 m class rotary-percussive drill built by Honeybee Robotics to capture subsurface regolith and, if present, ice on two lunar south pole missions: the PRIME-1 payload on the Intuitive Machines IM-2 Athena lander, and the VIPER rover [1]. Two identical units were delivered, differing only in a set of calibration targets for VIPER’s near-infrared spectrometer. The drill does not analyze anything itself. Its product is a cuttings cone deposited on the surface for a mass spectrometer and, on VIPER, a spectrometer to read, plus the telemetry the act of drilling generates.

Rotation and percussion are driven by separate actuators, so the drill can be run in rotation alone, percussion alone, or both, and can save the percussor’s power when the material does not need it. The design descends from two decades of Honeybee drills funded through CRUX, Icebreaker, the Life in the Atacama drill and Resource Prospector, with mass falling from over 50 kg at Icebreaker to 15 kg at LITA before rising again for the flight configuration [1], [2].

TRIDENT flew on IM-2, launched 27 February 2025 and landed 6 March at Mons Mouton [1]. Athena came to rest on its side, so no hole was drilled; the drill was instead run through its full range of motion in a horizontal orientation while buried in regolith thrown up during landing. VIPER has not flown.

Specifications

Parameter	Value	Source
Total mass	26.5 kg	[1]
Drill hardware mass	19.5 kg
Avionics mass	7 kg
Height	approximately 1.75 m
Bit diameter	25.4 mm, percussive-grade carbide tip
Feed stroke	1 m
Deploy stage stroke	0.35 m
Percussive blow energy	2 J at up to 972 blows per minute
Percussor rated power	300 W	[2]
Nominal rotary power	50 W	[1]
Auger speed	100 rpm nominal, 10 to 120 rpm commandable
Feed speed	1.25 mm/s drilling, 2 mm/s otherwise, 0 to 4 mm/s commandable
Weight on bit	100 N nominal, 0 to 500 N commandable
Linear stage rating	500 N bidirectional	[2]
Percussion rate	729 blows per minute nominal, 0 to 1000 commandable	[1]
Bite length	10 cm nominal, 1 to 10 cm commandable
Cuttings per bite	about 12 cc per 10 cm	[2]
Actuators	four brushless DC, with planetary, spur and bevel gearing	[1]

Mission profile

Parameter	Value	Source
Launch	27 February 2025, 00:16:30 UTC	[1]
Landing	6 March 2025, about 17:30 UTC
Landing site	Mons Mouton, 84.7906 S, 29.1957 E
Lander attitude	on its side
Drill activation	about 20 minutes
Deploy stage extension achieved	35 cm
Feed stage extension achieved	100 cm
Regolith penetrated	none

With the lander horizontal there was still enough power to exercise the drill. Over about twenty minutes both rotation and percussion actuators were run, both launch locks released, both linear stages driven to their full extension, the auger heater cycled, and the two drill string temperature sensors read out, all while the mechanism and avionics box were under a thick layer of regolith deposited during landing [1]. The builders’ assessment is that the system operated within flight parameters and behaved as it had in preflight test.

VIPER’s assignment is different in kind: about three drilling deployments at each science station across a 100 Earth-day nominal mission in a 5 by 5 km area on Mons Mouton, with drill sites chosen tactically by the science team from the neutron spectrometer’s readings [1].

Approach

The drill removes material in bites rather than in one continuous hole. After about 10 cm of penetration the auger is withdrawn, a passive brush arranged as a worm gear against the auger scrapes the cuttings off, and a chute deposits them on the surface as a cone; the drill then re-enters the hole for the next 10 cm [1]. Three consequences follow [1]. The cuttings retain a 10 cm stratigraphy instead of being mixed over a meter. Drilling torque stays low, because cuttings are never conveyed the full height of the hole, and on re-entry to an empty hole the initial torque can be attributed to material strength alone rather than to strength plus chip transport. And the bit has time to cool between bites, which matters for retaining volatiles in the sample.

The auger is built in two sections to serve that scheme. The lower sampling section has deep flutes so that material jams in and stays there; the longer upper section has shallow flutes for conveyance [1]. The combination is deliberately efficient at sampling and inefficient at conveying, so drilling a full meter in one run raises torque and power and increases the chance of a cuttings jam.

Two nested linear stages carry the drill. The deploy stage presses a footpad against the surface for stability, and the feed stage advances the string. Both use a steel wire rope capstan on a rolling carriage rather than a ball screw, chosen because lunar regolith is more abrasive than Martian dust and a ball screw fails if dust enters it [1]. The capstan also lets the drill head float during percussion, which is the mechanical analogue of not pushing down on a jackhammer.

Mobility

None. TRIDENT is fixed to its host and reaches only along its own feed axis.

Power and energy

Nominal rotary drilling power is 50 W; the percussor is rated at 300 W [1], [2]. No battery is carried and no energy budget for a complete hole is published. On PRIME-1 the entire activation ran on power the toppled lander could still supply.

Thermal

Kapton film heaters warm the avionics and actuators to operating temperature, and a heater inside the auger with a colocated temperature sensor 35 cm above the bit serves three purposes: thermal conductivity measurement, freeing the string if ice adheres to it, and driving sublimation from the cuttings pile [1]. Flight units passed thermal vacuum, vibration, shock and electromagnetic compatibility testing. Bit temperature during drilling is itself a measurement rather than a constraint: in engineering unit tests the bit cooled at visibly different rates in dry and in icy simulant, because dry lunar soil is insulating and the stem retains more heat in it.

Compute and avionics

The avionics box holds four motor drivers, a thermal card, a power distribution unit and a command and data handling board [1]. Onboard software commutates the brushless motors and strings low-level actuator commands into named operations: release launch locks, calibrate actuators, deploy the footpad, drill, retract to deposit cuttings, stow. No processor part or radiation tolerance approach is published. A rotary slip ring carries power and data to the auger heater and its two platinum resistance thermometers, and flex harnesses carry power and data across the full travel of both stages.

Autonomy

The drill is operated in near real time rather than autonomously, a decision the builders justify as simplifying avionics development while letting operators catch slippage, clogging and unanticipated behavior as it happens [1]. One behavior is onboard: percussion is normally triggered automatically when feedback shows the drill is making insufficient progress. Everything else is commanded.

Communications

Through the host vehicle. No band, rate or latency figure is published for the drill itself.

Payload and instruments

TRIDENT carries two platinum resistance temperature detectors, one integrated in the drill bit and one in the auger beside the heater, and no other instrument [1]. Its scientific output is otherwise indirect: the cuttings cone it builds is what MSOLO and, on VIPER, NIRVSS measure, and its own telemetry is a geotechnical instrument.

Three derived measurements come out of that telemetry. Specific drilling energy relates to unconfined compressive strength through an empirical baseline fitted across rocks from 4 to 120 MPa, and rate of penetration varies inversely with the same quantity [1]. Cone index follows from weight on bit and penetration rate before drilling starts. A modified footpad deployment, driven under current limiting with position telemetry read back, yields a force-penetration curve and from it the modulus of subgrade reaction and ultimate bearing capacity, quantities used in the Apollo era to predict how far surface packages would sink [5]. On VIPER these point measurements were to be extended laterally along the traverse using wheel sinkage and mobility system telemetry [3].

A separate Antarctic field campaign with the engineering unit showed that drill telemetry alone identifies subsurface horizons: an ice-rock transition at about 62 cm, a frozen boundary at 20 cm, and a bubble-rich ice layer at about 50 cm that matched published bubble content peaks [2]. Ice, soft soil and hard rock each produce a distinct signature in torque, weight on bit and penetration rate. Those results come from Antarctic ice and till at Earth gravity, not lunar regolith.

The percussor has also been examined as a seismic source. A single 2 J blow produces an impulse above 50 Hz detectable 62 to 76 dB above the noise floor on accelerometers mounted on the drill chassis [1]. The flight inertial measurement units on both missions sample at 100 Hz against the 200 Hz used in the laboratory, so content above 50 Hz may not survive.

Ground testing

Source: [1], CC BY 4.0.

Flight units were environmentally tested but never used to drill simulant, and their drill strings were replaced after testing, so no flight-unit drilling data exists [1]. All drilling performance comes from a dedicated engineering unit, which cut nearly 30 m in roughly 1 m intervals across 337 bites and more than 30 hours.

Test condition	Result	Source
NU-LHT-2M and LSP-2 simulants, below -100 C and below 1e-4 Torr	no measurable dust ingress effect on actuator no-load currents	[1]
LSP-2 doped to 8.5 wt% water, vacuum	bit cooling rate distinguishes icy from dry soil
Rock coupons, 4 to 120 MPa unconfined compressive strength	specific drilling energy and penetration rate baselines
Percussive drilling to failure	cam-spring life 2 to 3 days of continual percussion	[2]
Antarctic field campaign, 15 boreholes	percussive head broke after two days, repaired from field spares

The icy simulants are not lunar ice. Qualitative volatile measurement was not a baselined requirement on either mission, so no complex ice-formation method was used and the samples are water-doped simulant rather than an analogue of the polar deposits the drill was built to sample [1].

Modes of operation

Rotation, percussion, and rotation with percussion, selected by the operator or triggered onboard when progress stalls [1]. Between these sit the named sequences the flight software carries: launch lock release, actuator calibration, footpad deployment, drilling, retraction with brushing, and stow.

Ground operations

Three console roles: a payload uplink lead who owns execution and sends every command, a payload downlink lead who watches telemetry and reports instrument health, and a TRIDENT Science role that represents the drill in the science center, recommends drill sites and advises when conditions warrant deviating from the procedure [1]. On VIPER the uplink and downlink leads sit in the payload operations control center and the science role in the mission science center; on PRIME-1, with fewer instruments and a slower pace, all three were colocated with MSOLO. The ground software is a graphical interface named Poseidon that sets command parameters, sends commands, and displays telemetry as indicators, plots and event records; procedures are organized in a separate tool named PRIDE so that drilling can be synchronized with the instruments watching the cuttings pile.

Technologies developed

The bite-sampling architecture, and the pairing of a deep-fluted sampling auger with a shallow-fluted conveying auger that makes it work, is the transferable result. So is the capstan and rolling carriage feed, adopted specifically because a ball screw is vulnerable to abrasive dust, and the decoupling of rotation from percussion so that percussive power is spent only when the material demands it.

The empirical relations between drill telemetry and material properties are the second result, and they are what makes a drill a geotechnical instrument rather than only a sample acquisition device: specific drilling energy against compressive strength, rate of penetration against the same, bit cooling rate as a qualitative indicator of ice, and footpad force-penetration as a bearing capacity measurement [1]. The Antarctic campaign extended these into automated horizon detection from telemetry alone [2].

What the program has not produced is a lunar drilling result. Every penetration number attributed to TRIDENT is from simulant or terrestrial rock.

References