NIAC 2021 SWIM - Sensing With Independent Micro-Swimmers

 Niethen Schaler et al.- SWIM - Sensing with independent micro-swimmers

Notes by Paul Fischer

NASA has been exploring use of swimming cryobots that are immobile upon entry to a frozen area such as Europa or Titan

The purpose is to provide distributed, highly redundant sensing

Open access missions are highly constrained by volume, shape and reliability requirements, tens of liters of payload and 10s-100s cm scale micro swimmers

Other models are either too large or have too limited payload

Begin by mapping science traceability matrices

Particular attention to four key subsystems

Instruments

Actuators

Communications 

Power

System architectures

Ranking of tech options and develop architectures at viable size scales

Overarching goal of any sub ocean mission is to evaluate the entirety of the ocean

SWIM builds on three science objectives of JPL’s PRIME concept

Other object exploration by : OPAG, NOW and NASA Roadmap to Ocean worlds

Search for and characterize life

Characterize chemical environments and processes by interrogating the ice shell and ocean, 

Characterize physical environments and processes within europa ice shell and ocean

Focus on those enabled by micro robot exploration

Swim enables the search by permitting investigation of region outside of the immediate crypto field of view

Swim enhances investigations of th physical and chem state of the interface providing spatial measurements

We need 9 pascals across a 84 hour day night cycle

Given the engineering constraints, the first case-study was an exercise in micro robotism

Resonance, frequencies must be used for thrust and steering

We also rely on passive ultra craft back-pattering to let mother craft passively read SWIM movements

12cm, 100 cm scale cubed

Low range communication, with intelligence for remote control

Initial mid-size swim design packaging design

Payload volume of five liters allows over 48 robots to be docked in an unpressurized chamber for cruise nd descent

These can be added to other craft and to ice probes

Build a 2d or 3d ocean ice interface and water column, relay of data to mother craft through ultrasound occurs

Actuation and communication ar the most challenging tradeoff

Top speeds are well below the relative ocean currents to operate reliably at these sizes

Higher frequencies have greater attenuation in water, smaller robots require transducers with lower effect there.

Q: Is the anatomy of fish considered in the design of microswimmming robots?

A: One of the big traits is to see how to make the robots swim, they don’t swim fast enough

Q: trade offs

A: there might be more sophisticated robots, but that means to send less. So a thought the team had was to develop one “lead” robot that can be deployed based on information delivered from the smaller 

Q: Mesh?

A: we thought about how the robots can communicate to each other, the smaller the transducer the lower the range, so a mesh communication array would be a way to dreduce the number of robots and size of transducers… however sending via relay means the mother crafts may spend more time relaying data through the mesh rather than reacting directly

Q: chemical propulsion?

A: find chemistry in the ocean, signs of extant life, including looking at unique organism chemistry rather than inorganic, use of chemical propulsion could disturb the water volume, for example hydrogen peroxide, but this would leave a lot of chemistry in the water

Q: anatomy of fish in the design? Entire shape of fish that informed the designs?

A: there is a lot of work on bioinformed robots, they all follow the idea of having a streamlined body, and we do have fins which is a little bioinspired. My experienecnec is that biomimicry might be wrong, a fish does not need to fit in a tube, but we do.

Q: Does the propulsion have any impact on communication?

A: could interfere with ultrasound communication

Q: Web of acoustics to increase complexity and range

A: everything has to be balanced with the battery life of the robots themselves

Q: could anchoring time be used to recharge battery life?

A: necessity to be close to the mothership, or to look at wireless charging systems

Q: why use 3d printing to make the robots?

A: unconventional shapes, small batch manufacturing can be cheaper and more difficult to iterate. We are also looking at a high pressure environment, not looking at water leak in and destroy robot electronics.