THE SATELLITE

LELP-1: design of a free-flying life-science lab

LELP-1 is a free-flying, uncrewed laboratory for life science and microgravity research. It flies 32 sealed experiment bays in a 550 km dawn-dusk orbit for as long as the longest experiment on board needs, up to 14 days, runs them automatically on signed customer commands, and brings the whole lab home under an inflatable heat shield so samples reach the customer's courier within half an hour of splashdown.

Launch mass242.6 kgof the 250 kg RUPAK allocation

Comes home222.6 kgarm, wings, antenna stay with the stage

Bays32110.6 kg of modules on this manifest

Quasi-steady g~7.3 × 10⁻⁷ gat a bay, computed below

Return7.7 g peakentry model, 4 °C held in the bays

Mission

LELP-1 is the orbital laboratory of the RUPAK system. The reusable RUPAK booster and its upper stage put the lab into a 550 km dawn-dusk sun-synchronous orbit. The upper stage stays attached during the mission: it carries the solar wings, trims the orbit and later flies the deorbit burn. Lab operations last as long as the longest protocol on the manifest (2 to 14 days). Then the robotic arm parks itself on the stage, the lab separates, inflates its 2.6 m heat shield, enters, opens its parachute at 4 km and splashes down near the recovery ship. The arm, the solar wings and the relay antenna stay with the stage, so 222.6 kg comes home and the stage breaks up over open sea.

LELP-1 in CAD

Generated from the twin by cad/build_lelp1.py (CadQuery, OpenCascade): the 32-bay stack with each bay's payload mass, the central chamber, the packed heat shield, Dexter-L on its ring track, and the RUPAK upper stage with the 600 W wings, the relay boom and the arm's grapple post (the stage is simplified context). Switch to Entry for the Return Module with its 2.6 m heat shield inflated.

CAD generated by cad/build_cad.py (CadQuery, OpenCascade kernel) from the sizing numbers: concept geometry, not a released design.

Mass properties from the solids

Configuration	Mass kg	CoM z, m	Principal inertia, kg m²	Twin's estimate
In orbit: lab on the RUPAK upper stage	970	-1.34	1996 / 2019 / 191	420 / 420 / 110
Return Module, heat shield inflated	222.6	+0.65	65 / 68 / 44	-

Finding. The inertia computed from the CAD is about 4.8 times the twin's earlier estimate about the transverse axes, because the upper stage's mass sits metres from the stack's centre of mass. The twin now uses the CAD values; whole-mission runs of the attitude model:

Case	Peak wheel momentum	Margin at peak	Pointing error, arm moving	Peak disturbance	Dumping, share of time
twin estimate (before 4 Oct 2026)	91.3 %	9.5 %	7.2°	154 µN m	4.9 %
CAD, 3 x 3.5 N m s wheels	86.5 %	15.6 %	4.2°	712 µN m	7.6 %
CAD, 3 x 4.0 N m s wheels	74.0 %	35.1 %	4.2°	712 µN m	5.4 %

Gravity-gradient torque grows about five-fold and the magnetorquers dump more often, but Dexter-L's momentum still sizes the wheels. With 3 x 3.5 N m s wheels the margin at the peak is about 16 %, under a 25 % design target; 4.0 N m s wheels give about 35 %, at a wheel mass the vendor has to give. The larger inertia also cuts the pointing error while the arm moves from about 7° to about 4°.

What the 15 reference experiments ask, and how LELP-1 answers

The catalog's experiments are the design drivers. "Standard" is in every bay; "option" is a bay variant a customer books; "new" is a capability this design adds to LELP-1 because the experiments need it.

Need	Experiments	Status	Design answer
Culture temperature per bay, held through re-entry	Stem-cell organoids, Protein crystallization for drug formulation, Antibiotic resistance of pathogenic bacteria, Seed germination and root growth, Bioreactor for tissue engineering and biomanufacturing, Microfluidic lab-on-a-chip and organ-chips, Cell mechanobiology: how cells sense gravity and load, Biofilm formation on spacecraft and medical materials, Microalgae and cyanobacteria for oxygen and food, Human heart muscle cells from stem cells, Immune T-cell activation, Bone cells: resorption and mineralization, C. elegans muscle and ageing, 3D tumour spheroids for drug testing	STANDARD	Every bay has a 25 W thermoelectric block with its own setpoint from 4 to 45 °C. Preserved samples ride home at 4 °C or at the culture temperature, through re-entry and splashdown.
Automated fluidics (media exchange, dosing, fixing, lysing)	Stem-cell organoids, Protein crystallization for drug formulation, Antibiotic resistance of pathogenic bacteria, Seed germination and root growth, Bioreactor for tissue engineering and biomanufacturing, Microfluidic lab-on-a-chip and organ-chips, Cell mechanobiology: how cells sense gravity and load, Biofilm formation on spacecraft and medical materials, Microalgae and cyanobacteria for oxygen and food, Human heart muscle cells from stem cells, Immune T-cell activation, Bone cells: resorption and mineralization, C. elegans muscle and ageing, 3D tumour spheroids for drug testing	STANDARD	Pumps, valves and reservoirs in each bay run the customer's timeline without a crew; waste stays in a bag inside the bay's triple containment.
Imaging in orbit	Stem-cell organoids, Protein crystallization for drug formulation, Antibiotic resistance of pathogenic bacteria, Seed germination and root growth, Alloy solidification, Microfluidic lab-on-a-chip and organ-chips, Cell mechanobiology: how cells sense gravity and load, Microalgae and cyanobacteria for oxygen and food, Human heart muscle cells from stem cells, Bone cells: resorption and mineralization, C. elegans muscle and ageing, 3D tumour spheroids for drug testing	STANDARD	A LumaScope-class microscope in the bay, or a trip on the robotic arm to the central lab's 40x fluorescence microscope. Raw frames stay on board and come home; per-well metrics are downlinked daily.
Video of moving samples (beating heart cells, swimming worms, live cytoskeleton)	Human heart muscle cells from stem cells, C. elegans muscle and ageing, Cell mechanobiology: how cells sense gravity and load, Microfluidic lab-on-a-chip and organ-chips	OPTION	The bay imager records short video clips at video rate; the analysis (beat rate, body bends, fibre movement) runs on board and only the numbers and selected clips are downlinked. No arm moves during recording.
Light for photosynthesis	Seed germination and root growth, Microalgae and cyanobacteria for oxygen and food	NEW	A lit bay variant with an LED growth panel and a light sensor on a day-night timer inside the large-bay power limit, plus a gas-permeable vent so oxygen from photosynthesis does not build up.
Live samples loaded late and kept powered through launch	Stem-cell organoids, Protein crystallization for drug formulation, Antibiotic resistance of pathogenic bacteria, Bioreactor for tissue engineering and biomanufacturing, Microfluidic lab-on-a-chip and organ-chips, Biofilm formation on spacecraft and medical materials, Microalgae and cyanobacteria for oxygen and food, Human heart muscle cells from stem cells, C. elegans muscle and ageing	NEW	Bays are loaded through an access panel up to 24 h before launch (48 h for mature bioreactor tissue). A pad umbilical powers the bay blocks until liftoff and the lab battery carries them through ascent until the solar wings deploy (orbit insertion is about 47 min after liftoff in the twin). Cryopreserved cells keep the passive -80 °C cassette.
A 1 g control in orbit	Cell mechanobiology: how cells sense gravity and load, Immune T-cell activation, Antibiotic resistance of pathogenic bacteria, Stem-cell organoids, Microalgae and cyanobacteria for oxygen and food, Bone cells: resorption and mineralization, C. elegans muscle and ageing, 3D tumour spheroids for drug testing	NEW	A centrifuge bay in a second large-bay slot spins a cassette at 1 g next to the microgravity samples (about 105 rpm at an 8 cm radius, our estimate), dynamically balanced and placed away from sensitive bays. It separates microgravity from radiation, launch and handling effects, which a ground control cannot do, and can also run 0.16 g (Moon) or 0.38 g (Mars). Any customer can book positions in it.
Heat above 45 °C (directional solidification)	Alloy solidification	NEW	Transparent model alloys fly in a large bay with their own insulated 70 °C hot zone (5.7 kg, 26 W, estimate). Metallic alloys need a furnace bay variant across two large-bay slots (700 to 800 °C, about 200 W during melt-back, about 1 to 1.5 kWh per run, estimates), with its own power line and heat path, scheduled against the 600 W array.
Frozen samples after the flight	Biofilm formation on spacecraft and medical materials, Bone cells: resorption and mineralization	OPTION	Bays stop at 4 °C, so protocols fix or stabilise samples to hold at 4 °C until the lab. A -80 °C freezer and dry ice on the recovery ship take samples that must be frozen from the courier handover onwards; an in-orbit freezer bay is not planned for the first flights.
Quiet microgravity during sensitive steps	Protein crystallization for drug formulation, Alloy solidification, Cell mechanobiology: how cells sense gravity and load	STANDARD	Quiet windows in the mission plan (no arm moves, steady wheel speeds) and an accelerometer log in every bay.
Fast return to the customer's lab	Stem-cell organoids, Protein crystallization for drug formulation, Antibiotic resistance of pathogenic bacteria, Seed germination and root growth, Bioreactor for tissue engineering and biomanufacturing, Microfluidic lab-on-a-chip and organ-chips, Cell mechanobiology: how cells sense gravity and load, Biofilm formation on spacecraft and medical materials, Microalgae and cyanobacteria for oxygen and food, Human heart muscle cells from stem cells, Immune T-cell activation, Bone cells: resorption and mineralization, C. elegans muscle and ageing, 3D tumour spheroids for drug testing	STANDARD	The whole lab splashes down next to the recovery ship; each bay goes to its customer's courier with a signed custody ledger about 20 minutes after splashdown.
Containment of microbes and human cells	Antibiotic resistance of pathogenic bacteria, Biofilm formation on spacecraft and medical materials, Stem-cell organoids, Human heart muscle cells from stem cells, Immune T-cell activation, 3D tumour spheroids for drug testing, Microfluidic lab-on-a-chip and organ-chips	STANDARD	BSL-2 triple containment in every bay, pressure and seal monitoring, automatic isolation of a leaking bay.

The experiment bay

	Medium bay	Large bay
Payload mass	3.3 kg	6.0 kg
Peak power	15 W	30 W
Culture cassette	12 wells	24 wells
Temperature	25 W thermoelectric block, any setpoint from 4 to 45 °C, held through re-entry
Services	automated fluidics (pumps, valves, reservoirs for media, drugs, fixative and lysis buffer, waste bag); an optional LumaScope-class inverted microscope (brightfield and two fluorescence channels); active silicon dosimeter and passive TLDs; temperature, pressure, humidity and acceleration sensors; a passive -80 °C cassette for cryopreserved launch, loaded 24 h before launch; transfer by the robotic arm to the central lab's 40x fluorescence microscope.
Containment	BSL-2 triple containment, pressure and seal monitoring, isolation on a leak
Control	your own signed commands (start, preserve, arm tasks), checked by Sentinel; operator can power or isolate a bay but not run your protocol

Environment in the bays

Microgravity, quasi-steady

Source	Level	Basis
Atmospheric drag	6.0 × 10⁻⁹ g	density 3e-13 kg/m³ (moderate solar activity), 3 m² side area, Cd 2.2, 962 kg lab and upper stage
Gravity gradient	7.3 × 10⁻⁷ g	3n²d for a bay 2 m from the stack's centre of mass (estimate), along the local vertical
Rotation with the orbit	2.4 × 10⁻⁷ g	n²d, only if the stack turns once per orbit to stay Earth-pointing

Quasi-steady accelerations at a bay are below one millionth of Earth's gravity in the twin's numbers and are set by the gravity gradient, because the bays sit about 2 m from the centre of mass of the lab and upper-stage stack; drag at 550 km is about a hundred times smaller. That is the same order as the ISS's quasi-steady level, so a free-flyer's real gain is in vibration and transients: no crew, no dockings, no station machinery. LELP-1 has its own disturbances: in the twin the robotic arm shakes the lab to about 10⁻⁴ to 10⁻³ g while it moves (estimate), and reaction wheels and pumps add vibration. The mission plan therefore keeps quiet windows (no arm moves during crystallisation, solidification or mechanobiology steps), and every bay logs its own acceleration so customers see what their samples felt. These LELP-1 levels are model estimates until a bay accelerometer flies.

Radiation

The twin's dosimeter model gives about 0.6 mGy per day inside a bay at 550 km, with about six South Atlantic Anomaly passes a day, so a 7-day flight collects a few mGy. Measured doses inside the ISS Columbus module were about 0.2 to 0.36 mGy per day (table below), so the model is 1.7 to 3 times higher: plausible for a higher orbit with less shielding, but a model value until the dosimeter flies. Every bay logs its own dose from lab power-on to entry, and passive TLDs integrate the whole flight. A few mGy is far below the doses of most in-vitro radiation studies, so on LELP-1 microgravity dominates the space-versus-ground difference; a 1 g centrifuge bay on board separates the two.

The environment compared with earlier platforms

What	Value
ISS quasi-steady acceleration (below 0.01 Hz)	On the order of less than 1 micro-g; mainly from aerodynamic drag and vehicle rotation¹⁴
ISS vibratory acceleration without isolation	Spectrum runs from much less than 1 micro-g below 0.1 Hz to well over 10 milli-g at high frequency; payload isolation can cut it by up to a factor of 100¹⁴
ISS absorbed dose rate inside Columbus (DOSIS 2009-2011, DOSIS 3D from 2012)	195-270 microGy per day (2010 minimum) to 260-360 microGy per day (2012 maximum), i.e. about 0.2-0.36 mGy per day; varies with solar activity, ISS altitude and shielding¹⁵
Comparison with LELP-1 estimate	Our model value of about 0.6 mGy per day at 550 km is about 1.7 to 3 times the ISS Columbus values. Higher is the expected direction (higher altitude, lighter shielding), but no opened source gives a free-flyer number at 550 km. Treat 0.6 mGy per day as our estimate until checked.¹⁵
Free-flyer radiation measured on a biosatellite	Bion-M No.1 carried an RD3-B3 radiometer-dosimeter at 253-585 km in April-May 2013; dose-rate numbers not in the opened record¹⁸
Altitude of other recent platforms	POEM-4 at about 350 km; The Exploration Company Mission Possible at 550 km (same altitude as LELP-1)¹⁰¹⁶
Free-flyer microgravity level	No opened source gave a measured quasi-steady level for Bion-M, Foton-M or SJ-10. The LELP-1 figure (about 1e-6 g near the centre of mass) is our design estimate, not a sourced benchmark.

Sources

ISRO, CROPS: A Leap in Space Biological Experiments https://www.isro.gov.in/CROPS.html
NASA, A Researcher's Guide to: Acceleration Environment (NP-2015-11-040-JSC) https://www.nasa.gov/wp-content/uploads/2016/06/acceleration-environment-iss-mini-book_detail-508c.pdf
Berger T et al., 2016, DOSIS & DOSIS 3D: long-term dose monitoring onboard the Columbus Laboratory of the International Space Station (ISS), Journal of Space Weather and Space Climate, doi:10.1051/swsc/2016034 https://elib.dlr.de/107982
The Exploration Company, 2025, Mission Possible: re-entry milestone achieved for Europe's reusable spaceflight https://exploration.space/blog/mission-possible-re-entry-milestone-achieved-for-europes-reusable-spaceflight
Dachev TP et al., 2015, BION-M No. 1 spacecraft radiation environment as observed by the RD3-B3 radiometer-dosimeter in April-May 2013, Journal of Atmospheric and Solar-Terrestrial Physics 123:82-91, doi:10.1016/j.jastp.2014.12.011 https://cris.fau.de/publications/106622384?lang=de_DE

Lessons from earlier platforms

Get return approvals early (Varda W-1): the capsule launched in June 2023 but its FAA reentry license came only on 14 February 2024, and reporting cites license delays. LELP-1 should hold its reentry, range and splashdown permits before launch so the 2-14 day lab clock is real.
Drop-test the whole descent chain (The Exploration Company Mission Possible): the capsule reentered under control but was lost after communications cut at 26 km, before parachute opening; the chutes had not been drop-tested. LELP-1 should qualify the inflatable heat shield, parachute and flotation end to end before flying customer samples.
Plan the splash zone around the ships (ATMOS Phoenix 1): the inflatable heat shield flew, but the capsule splashed about 2,000 km offshore and recovery was not planned. LELP-1 must target a zone where the recovery ship already waits, to keep the 2 h courier handover.
Hand samples over fast (Bion-M No.1): mice were examined about 3 h after landing and showed some motor recovery by 6-8 h, so timing changed the readout. LELP-1 should log time from splashdown to fixation for every sample and offer in-flight fixation before reentry.
Monitor every bay so faults can be told apart from biology (Foton-M No.4 and Bion-M No.1): all Foton-M4 geckos died and the cause was still being assessed at landing; on Bion-M No.1, 15 mice died from a food-system failure. LELP-1 should log video, temperature, gas and fluidics state per bay, and consider a 1 g centrifuge control bay.
Run an identical ground twin (EcAMSat): flight results were compared with an identical payload run in the lab at NASA Ames. LELP-1 should run a synchronous ground bay with the same cassette, media and timeline for every customer.
Use proven autonomous well and card assays (PharmaSat, EcAMSat, BioSentinel): automated culture with dosing and in-flight readout worked without crew. LELP-1's 12- and 24-well cassettes with automated fluidics follow this path; downlink key data in flight so the mission still yields results if return fails.
Pair dose with biology (BioSentinel): a TimePix-based spectrometer flew next to the yeast to link dose and response. LELP-1 should keep an active dosimeter and passive TLDs in each bay and report dose per sample.
Hold temperature through the whole timeline (POEM-4 CROPS, Bion-M No.1): CROPS kept 20-30 C and Bion-M held about 21 C. LELP-1's 4-45 C bay control should stay powered through reentry, float and ship transfer, with a logged temperature trace handed to the customer.
Decide what must come back (SJ-10): only the return capsule with 11 loads came home while 8 loads kept running on the orbital module. LELP-1 returns the whole 243 kg lab, which simplifies sample handling but costs mass; this is a positioning point, not just a feature.
Offer data access like a station facility (ICE Cubes): customers log in remotely 24 hours a day and send commands. LELP-1's ground segment should give customers the same live view and signed command path.
Position against no-return platforms (POEM-4): stage platforms give orbit time at about 350 km but no sample return. LELP-1's value is return of live or fixed samples within days; say so plainly.

From the platform benchmark on the overview; sources there.

Subsystems

Chips show where each number comes from: TEAM a team document, TWIN the twin's own design, EST an engineering estimate, TBD open. Hover for the source.

Orbit	550 km TEAM dawn-dusk sun-synchronous, inclination 97.6 deg EST, period 95.6 min
Power	solar wings 600 W TWIN at beginning of life, battery 1500 Wh TWIN, 28 V EST bus. The dawn-dusk orbit keeps the arrays in sunlight most of the year; it crosses the Earth's shadow only from 03 May to 09 August, at most 22 min per orbit (23 %).
Thermal	lab held near 21 C EST by a 0.85 m2 EST radiator and heaters; each bay's own thermoelectric block sets its culture temperature. Team bands: mammalian 36.5 to 37.5 C TEAM, microbial 22 to 37 C TEAM, plants 20 to 23 C TEAM, cryo -80 to -20 C TEAM
Attitude	3 reaction wheels of 3.5 N m s EST sized for the robotic arm's momentum, star tracker, magnetorquers of 20 A m2 EST for momentum dumping
Data	on-board computer ARM Cortex-A, cFS or F Prime TEAM, 256 GB EST storage for imaging archives that come home with the lab
Communications	S-band TT&C through ISTRAC at 32,000 bit/s TWIN down; X-band science through Leuk (Switzerland) 2,000,000 bit/s TWIN and ESOC (Germany) 1,500,000 bit/s TWIN; inter-satellite relay 600,000 bit/s TWIN
Propulsion	none on the lab: the RUPAK upper stage stays attached, trims the orbit and flies the 150 m/s TWIN deorbit burn (Isp 330 s TEAM)
Return	2.6 m inflatable heat shield (4 tori, packed 1.1 m), 223 kg at entry, peak 7.7 g and 434 kW/m² in the twin's entry model, 9 m main parachute at 4 km, splashdown at 7.9 m/s
Command security	Sentinel: every command signed with ML-DSA-87 (post-quantum), checked against ownership and lab rules, and screened by a mission guardian; customers can only command their own bays

Mass budget

Item	kg	Return
experiment modules (32: 6 kg large, 3 kg medium class)	110.6	comes home
lab structure, entry-rated module latches	34.0	comes home
central chamber, translation rig, sensors	10.0	comes home
avionics, radios, Sentinel crypto unit, harness, beacons	13.0	comes home
battery 1.5 kWh	10.0	comes home
ADCS: 3 x 3.5 N m s wheels sized for the arm, star tracker, magnetorquers	11.0	comes home
thermal control	6.0	comes home
HIAD: 4 tori and straps	6.0	comes home
HIAD: flexible TPS (ceramic fabric, insulator, gas barrier)	6.0	comes home
HIAD: rigid nose and centerbody TPS	6.0	comes home
HIAD: inflation system (2 kg N2, bottle, valves)	5.0	comes home
main parachute 9 m, mortar, riser	5.0	comes home
Dexter-L arm and controller (parks on the upper stage)	12.0	stays with the upper stage
solar wings 600 W (stay on the upper stage)	7.0	stays with the upper stage
ISL antenna boom (stays on the upper stage)	1.0	stays with the upper stage
Launch	242.6	7.4 kg margin to 250 kg

The modules line is the 32 payload sheets in the twin's manifest. 6 kg and 3.3 kg are bay limits, not module masses: a manifest with every bay at its limit would weigh about 281 kg, so every manifest is checked against the 250 kg allocation.

Open design items

Power for the new bay types (lit bay, centrifuge, furnace, freezer) has to fit the 600 W array with the platform loads; the twin has not yet budgeted them.
Reaction wheels are sized for the robotic arm (3 x 3.5 N m s); a slower arm would allow smaller wheels and less vibration.
A manifest with every bay at its limit would weigh about 281 kg, above the 250 kg allocation; every manifest is checked.
Bay accelerometers and the quiet-window plan need a vibration analysis of the arm, wheels and pumps.
Entry loads on samples (7.7 g peak in the entry model) and splashdown shock need qualification for each bay type.
The payload partner for bay hardware (fluidics, imagers) is not decided; the twin assumes Space Philic builds the standard bay.