Feeling Through Spacesuits:Application of Space-Resilient E-Textiles to EnableHaptic Feedback on Pressurized Extravehicular Suits

Syamantak Payra*Massachusetts Institute of Technology

spayra1@mit.edu

Irmandy Wicaksono*Massachusetts Institute of Technology

irmandy@mit.eduJuliana Cherston

Massachusetts Institute of Technologycherston@mit.edu

Cedric HonnetMassachusetts Institute of Technology

honnet@mit.eduValentina Sumini

Massachusetts Institute of Technologyvsumini@mit.edu

Joseph A. ParadisoMassachusetts Institute of Technology

joep@mit.edu

Abstract—Extravehicular activity (EVA) spacesuits frequentlyremain bulky and pressurized, which impedes astronauts’ abil-ity to engage with the proximate environment and with fellowastronauts. In this project, a concept prototype for a sensateskin intended for the exterior of an EVA suit is manufacturedusing commercially available electronic fabric sensors. This pro-totype is then shown to discriminate between surfaces relevant tospace explorers (metallic objects, rocky surfaces, and spacesuitgloves), implying that each surface can be translated into aunique sensory experience. Specifically, haptic actuators flushagainst the astronaut’s biological skin can transduce sensorydata from the external environment through the pressurizedsuit, allowing the astronaut to feel touch input right through thespacesuit. The key contribution of this work is to introduce aplausible application area for space-resilient electronic textilesusing commercial off-the-shelf fabric sensors for demonstration.

TABLE OF CONTENTS

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. PROJECT OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13. RELATED WORK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34. CONTRIBUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45. PROTOTYPE MANUFACTURING . . . . . . . . . . . . . . . . . . . . . 46. ROBOTIC TEST APPARATUS . . . . . . . . . . . . . . . . . . . . . . . . . 57. RESULTS & DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68. FUTURE WORK / VISION FOR TEXTILES . . . . . . . . . . . 99. CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10BIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1. INTRODUCTIONAs humanity seeks to establish a more significant presence inLow Earth Orbit and beyond, human explorers will bridgethe gap between quantitative scientific inquiry and keenlyexperiential discoveries. Indeed, NASA’s famous Visions ofthe Future [1] convey humanity’s hunger for rich, thrilling,

*These authors contributed equally978-1-7281-7436-5/21/$31.00 c©2021 IEEE

and immediate sensory experiences of a cosmos filled withworlds that can be known and explored.

The direct engagement of explorers with their proximateenvironment is crucial for promoting both maximum situa-tional awareness and vivid sensory feedback. However, theprotective pressurized spacesuit worn by astronauts createsa thick boundary between the wearer’s biological skin andthe suit’s space-exposed surface, isolating and impeding thewearer from engaging with the intuitive sensory and tactilefunctions of human biological skin.

SpaceTouch is a conceptual application area for fabric sens-ing on the spacesuit exterior. An implementation overviewand a set of broad potential use cases for this concept are sum-marized in Figure 1a. This spacesuit composition enhancesthe safety of pressurized suits while reinstating a biologicalsense of touch. To do so, touch input from the protective suit’sexterior layer is detected, identified, and mapped to a hapticfeedback system on the wearer’s biological skin, ‘conducting’sensory data from the exposed skin to within the spacesuit.

2. PROJECT OVERVIEWTo date, little has been done to augment the performanceof the exterior fabric on spacesuits, despite this materialoffering key real-estate for distributed sensing in the vicinityof the astronaut. Recently, our group has been developingspace-resilient smart textiles to one day enable a varietyof applications on habitat and spacesuit exteriors, rangingfrom scientific characterization of interstellar space dust, tosystems that inspire deeper connection between astronautsand their environments [2], [3].

In this work, we assess the technology requirements foreffective human-computer interaction within a spacesuit bycreating and evaluating a prototype of an external sensate skincapable of multimodal sensor measurements. Eventually, thisexternal layer can be used either as part of a closed-loophaptic feedback system for astronauts in order to boost sit-uational awareness in a variety of operational environments,or as an open-loop data source for remote monitoring ofextravehicular astronaut activities.

Electronic textiles incorporated into spacesuits can also en-able more descriptive remote-monitoring capabilities for mis-

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Figure 1. a) Representative environments encountered by astronauts informing the current study, and b,c) explodedview of multi-modal e-textile spacesuit skin.

sion control centers and other remote entities. In particular,it becomes possible to augment virtual renderings of astro-naut EVA with data derived from the astronaut’s proximateenvironment for real-time safety-monitoring and enhancedmission tracking purposes, as well as for astronaut training.

A representative prototype for this external skin is manufac-tured using primarily commercial off-the-shelf (COTS) fabricsensors integrated into an external armband representative ofsuits used for EVA and exploration. The sensors integratedinto the suit’s outer skin layer include capacitive proximitydetection, piezoresistive pressure detection, and piezoelectricvibration detection (see Figures 1b-c). We assess this de-

sign by detecting and differentiating between textured end-effectors on a robotic manipulator, and show that it is possibleto differentiate between environmental stimuli encounteredby astronauts operating in different environments, allowingfor unique haptic mappings associated with each stimulus.

The system architecture introduced in this paper can also beapplied in hazardous aerospace or terrestrial environmentswhere humans must perform dangerous operations. In suchenvironments, electronic textiles and suits that sense environ-mental stimuli, protect occupants, and alert operators to anypresent dangers can provide intelligent protection and aware-ness, enabling greater degrees of operational efficiency and

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safety. Figure 2 shows a graphical interface that highlightsregions of the spacesuit experiencing events of interest, suchas tactile pressure on the spacesuit textiles, or the detection ofan air leak.

3. RELATED WORKConductive textiles date back to at least the 17th century -gold and silver yarn have been woven into ornate clothingand tapestries around the world [4], [5]. In recent decades,textile designers and engineers have started to take advantageof the conductive, resistive, and capacitive properties ofthese centuries-old fibers in order to create electronic textiles[6]. More sophisticated multi-material fibers are also nowbeing designed. To provide some examples, these multilayerfibers may achieve piezoelectric properties [7], or containmicrochips to confer sensory capabilities to digital platforms[8]. In general, advances in electronic textile technology haveyet to be leveraged for space exploration, particularly in thecase of space-exposed fabrics.

Multi-modal sensing for Human-Computer Interaction

In the field of Human-Computer Interaction (HCI), e-textilesensors for pressure, stretch, or touch detection are often fab-ricated by combining layers of conductive and piezo-resistivematerials [9]. Both knitted constructions and embroideredconstructions have been utilized in some of our researchgroup’s previous work exploring the use of e-textiles formusic creation [10], [11], clothing-based sensing [12], andhuman-computer interfaces [13], [14].

Multimodal sensing has been used in HCI systems to incor-porate sensory and emotional perception into devices throughhaptic feedback systems. For instance, inflatable actuatorshave been paired with force-sensitive resistors and air pres-sure sensors for haptic feedback on the torso similar to that ofa hug [15], [16]. We derive similar functional principles, butgear our implementation and evaluation towards fabric-basedsystems augmenting personal protective equipment (PPE)within aerospace environments. By adapting fabric sensorsin a way that they can be embedded within a pressurizedEVA suit, the physical protective functions of the textile con-struction can be supplemented by digital safety-monitoringfunctionalities and the heightened situational awareness fromsensory conduction.

E-textiles for Space Exploration

Despite exciting progress in electronic textile technology,today’s spacesuits are not so different from the one that AlanShepard wore inside Freedom 7 in 1961. The primary focusof NASA, SpaceX, and others in recent suit designs hasbeen on improving astronaut mobility; at best, touchscreen-compatible fingertips have been incorporated as a modest nodto opportunities available for fabric functionalization [17].

There has been growing interest in porting e-textile technol-ogy to the internal construction of spacesuits for measure-ment of astronauts’ health and wellness. MIT’s Human Sys-tems Laboratory and the University of Minnesota’s WearableTechnology lab have studied strain sensors and other internalbiological sensors to improve spacesuit fit and monitor humanhealth in microgravity [18], [19]. Both ESA and NASAhave also contracted with textile manufacturing companiesover the years to develop adaptive textile technologies forastronaut wellness, such as carbon nanotube fibers that con-duct heat to regulate astronaut temperature (NASA/NanoTex,

Figure 2. Illustration of SpaceTouch Graphical UserInterface (GUI) for real-time physical interaction

visualization and safety assessment.

2001) and fabric electrodes that keep track of muscle health(ESA/Aarhus, 2009) [20]. These public-private partnershipsdemonstrate interest in the potential aerospace applications ofE-Textiles.

While astronaut health sensing will remain an essential appli-cation for e-textiles in spacesuit design, the construction andevaluation of these materials has been similar to that of Earthapplications; since the fabrics are buried within the spacesuit,they do not need to survive extreme conditions, nor can theytell us anything about the space environment.

Meanwhile, when it comes to fabric on the spacecraft orspacesuit exterior, emphasis to date has been on engineeringthe material’s intrinsic protective properties – UV and par-ticulate radiation, atomic oxygen erosion, extreme thermalcycling over 90-minute orbital periods, outgassing undervacuum, and penetrations from impact are all risks in LowEarth Orbit. Besides passive protection, there is an isolatedconcept prototype for a pressure-sensitive helmet lightingcontrol switch integrated into NASA/ILC Dover’s 2001 I-Suitprototype [21]. In sum, the space-exposed fabric material hasbeen largely untouched.

Haptics for Personal Protective Equipment

Haptic feedback systems are frequently considered as sub-systems on robotic structures for human-robot interactionor human-human interaction over significant distance. Forexample, [22] describes a pair of haptically connected leverslinking the International Space Station with Earth, enablinga virtual handshake to be performed at a round-trip distanceof 163,000 kilometers within <20ms delay. Remote tactilecontact for establishing shared presence at a distance hasbeen long explored in the HCI community, for example the1998 ‘In-Touch’ project which explored haptics as a mode ofinterpersonal communication at a distance [23].

Concurrently, there has been a growing appreciation for thebenefits of direct integration of feedback systems on extremeenvironment suits. The benefits of biological touch sensitivityduring EVA was first established in a user study conducted in2015 at the Mars Desert Research Station, in which a glove

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was equipped with an array of passive plastic pins embeddedin silicone, and an internal transduction layer with electricallycontrollable stiffness was used to tune the coupling betweeninterior and exterior layers [24]. In 2017, a multidisciplinaryteam of designers and aerospace engineers built the EnhancedSpace Navigation and Orientation Suit (ESNOS) as a demon-stration of the use of haptics for orienting astronauts in micro-gravity [25]. Then in 2019, the benefits of touch response inspace were further studied from a physiological perspective,suggesting that sensory feedback may support psychologicaland social well-being, in addition to heightening experiencesand promoting occupational safety [26].

4. CONTRIBUTIONWe note a few central benefits to an all-textile, electricallycoupled design approach for haptic feedback on spacesuits:

• Directly leverages the existing space robust textile substrateon the spacesuit

• Suitable for delivering haptic responses on pressurized re-gions of the suit, since layers are electrically rather thanmechanically coupled

• Possibility for an enhanced sensing experience driven bya multimodal sensor suite, including sensing of surfacesproximate to the suit, light touches, or wind conditions onplanetary bodies with atmosphere.

As illustrated in Figure 1b-c, the SpaceTouch multi-modaldesign consists of three main layers: an outer proximity andtouch sensing layer containing conductive patches integratedonto a base fiberglass fabric, vibration and impact-sensitivepiezoelectric fibers woven into channels in the fiberglass fab-ric, and multi-layer pressure-sensitive piezoresistive fabricsjust below the outer layer. Capacitive coupling between anobject as a virtual ground and charged conductive patchesreflects touch and near-proximity. An intermediary foamlayer separates the aforementioned layersfrom the inner lay-ers of the spacesuit. An actuation layer that is coupledto the skin can provide closed-loop haptic feedback basedon the sensor data. Our fully-textile-based sensor designand integration will enable future realization of single-layercapacitive, piezoresistive, and piezoelectric e-textiles that cansense and respond simultaneously to a variety of stimuli.

5. PROTOTYPE MANUFACTURINGFirst prototype

Two prototypes were constructed (see Figure 3). The firstis primarily intended for conceptual demonstration purposes.Piezoelectric fibers were weft-inserted into a Beta cloth fabricsimulant (a space-resilient material used on the exterior of thespace station and Apollo-era Spacesuits) to serve as an exte-rior layer of an arm band (Figure 3a-c). The specifications forthis representative Beta cloth material are detailed in [2], [3].Eccentric rotating mass (ERM) motors are mounted on theinner layer of the band, with a thick foam used to isolate thetwo layers. The piezoelectric signal response directly drivesthe ERM motor vibration profile. Commercially availablepiezoelectric copolymer coaxial cables were sourced fromTE Connectivity, with an internal construction consisting ofmulti-filament copper wire core with PVDF-TrFE dielectricand outer copper wire braid, sheathed in rubber cladding.The woven piezoelectric fiber (Figure 4) was fabricated by

Figure 3. Prototypes of the e-textile spacesuit skin: a-c)Woven piezoelectric Beta cloth. d-f) Knitted fiberglass

with conductive yarns and multi-modal embedded fabricsensors.

stripping the external rubber cladding and coating the PVDF-TrFE surface with conductive elastomeric ink (CI-1036, En-gineered Conductive Materials). The coated fiber (Figure4c) was then cured on a hotplate for 12 hours at 90 ◦C.The fiber sensors and Beta fabric used in this space-exposedmaterial are currently under study on-board the InternationalSpace Station for robustness to the space environment. Thisprototype acknowledges the eventual need to ensure thatmaterials used on the suit’s exterior are compatible withthe atomic oxygen erosion resilience, outgassing, thermalcycling, and abrasion resilience requirements for a space-exposed substrate. It also implements the full sensor-actuatorconcept.

Second prototype

For the purpose of increasing the channel count and multi-modal sensing capabilities of the prototype, as well as for thepurpose of conducting quantitative sensory detection testing,a second prototype was constructed (Figure 3d).

We knitted fiberglass yarns (ET9, Jiangxi Glass Fiber Co.,Ltd.) with a flat, two-bed digital knitting machine (Super-NJ

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Figure 4. Magnified images of piezoelectric fabric (top) and fibers (bottom). a-c) Piezoelectric fiber with silverelastomeric ink woven into a Beta-cloth, and d-f) multi-layer configuration of conductive and piezoresistive fabrics with

piezoelectric cable in-lay in a knitted fiberglass fabric.

212, Matsuya). Two yarn carriers were employed in orderto develop two layers of weft-knit fabric. An interlockingmechanism was programmed to fuse two fabric layers intoone. This was done by performing knitting sequences so thatthe front and back loop interchanged with each other. Hol-low textile channels for threading piezoelectric fibers (PiezoCopolymer Coaxial Cable, TE connectivity) were knitted byprogramming front-knit and back-knit to loop independentlyon each side of the channel. As demonstrated in Figure3e-f, we fed a combination of fiberglass and conductiveyarns (Weiwei Line Industry) into one of the yarn carriers todevelop a fiberglass fabric with seamless conductive patternsthat could form electrical connections with the conductivefabrics shown in Figure 3d.

We then sewed four knitted conductive fabric patches(Stretch, LessEMF) onto the fiberglass fabric using a sewingmachine (XL150, Singer) and wove three piezoelectric fibersinto the knitted channels. For pressure sensing layers, westacked two conductive fabric layers: one for groundingand the other layer for discretization into four patches. Inbetween these layers, we embedded a knitted piezoresistivefabric (LG-SLPA-20k, Eeonyx Corporation). These layerconfigurations can be observed in Figure 4d. Figure 4e showshow the piezoelectric fiber is woven into one of the knittedtextile channels.

6. ROBOTIC TEST APPARATUSSystem Implementation

To evaluate this design, textured end-effectors on a roboticmanipulator are brought in contact with the fabric sensor suitein order to qualitatively assess that actionable environmental

data can be collected and eventually transmitted throughhaptic interfaces to wearers.

In order to create sufficiently repeatable inputs simulating avariety of space-relevant stimuli, a robotic test apparatus wasdevised and implemented to evaluate sensor inputs from thee-textile. As seen in Figure 5, the test apparatus containsan actuating component, consisting of a 5-degree-of-freedomrobotic manipulator (AL5D, Lynxmotion) and various end-effectors representing multiple surface types, and a sensingcomponent, which is a representative sample of a sensate e-textile spacesuit skin.

In this test setup, the robotic arm is controlled by a computerissuing pre-programmed motion inputs. Three distinct end-effectors are mounted on the manipulator. During testing,the setup (Figure 5, and 6) was mounted on a table usingsticky rubber padding under the manipulator for improvedadhesion between the manipulator base and the underlyingtable. The fabric test sample (left, Figure 6) is also mountedon rubber padding to provide vibration isolation from therobotic manipulator.

This SpaceTouch prototype has a total of four piezoresistivepatches for pressure sensing, four capacitive patches fortouch and proximity sensing, and three piezoelectric fibersfor vibration and impact sensing (Figure 5b). Sensor datagenerated by the fabric sensors are collected by a microcon-troller (Teensy 4.0) using a set of mixed-mode analog/digitalreadout electronics: an MPR121 capacitive sensing boardfor capacitive proximity and touch detection, amplifiers toread out signals from the piezoelectric fibers for vibrationsensing, and voltage dividers and voltage-followers for thepiezoresistive fiber sensors. The MPR121 Proximity TouchController is utilized for capacitive sensing with thresholding

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Figure 5. a) Test setup: a robotic arm actuates on thesensor with various end-effectors. b) System interface

diagram of multi-modal e-textile.

to accurately detect discrete touch and an aggregate or multi-plexed capacitive sensing for near-proximity detection. It has12-channel input and measures capacitance by charging anddischarging each electrode and measuring the voltage simul-taneously to detect capacitive coupling from the approach ofa finger or conductive object. The microcontroller combinesthese sensor data inputs and relays a serial data stream to thecomputer, where incoming data is collected and analyzed.

To provide a set of representative interactions with stimuliin aerospace contexts, the following motion sets were imple-mented with the robotic testbed:

• Impact (vertical motion directly onto the fabric)• Stroke (side-to-side translational motion)

End-Effector Design

End-effectors were mounted onto the end of the robotic armin order to simulate different objects that might come intocontact with spacesuit fabrics. These end-effectors vary insurface texture as well as various material properties, includ-ing composition, weight/density, compliance, and conductiv-ity.

To decide on a set of end-effectors to use for testing thesensitivity and characteristic signals generated by the sen-sate spacesuit skin, characteristic scenarios were consideredthat astronauts might encounter in space exploration appli-cations. These scenarios were categorized into three keytypes: astronaut-astronaut interactions, astronaut-spacecraftinteractions, and astronaut-environment interactions.

The following end-effectors were subsequently chosen asanalogs to simulate these use cases due to their ubiquitousnature in space applications:

• Spacesuit glove• Metallic object (representing components on a spacecraft

structure)• Rocky aggregate (representing Lunar/Martian rocks, or

the surface of an asteroid)

Figure 6 shows the different end-effectors and depicts somecharacteristic motion profiles, such as increasing proximity,horizontal stroke, and perpendicular impact.

For the spacesuit glove, a leather work glove was used toreproduce the compliant yet form-fitting nature of spacesuitgloves. Support material was inserted within the glove toincorporate a degree of partial rigidity, similar to that of ahand with outstretched fingers. This allowed the “impact”motion to simulate an example case of an astronaut pressingbuttons on a spacecraft or spacesuit interface, or pokinganother spacesuit, such as to get the attention of anotherastronaut. The glove was mounted onto the robotic arm,anchored onto the “gripper” portion of the manipulator toallow for wrist mobility, and reinforced in place for testing.

To simulate a metallic object, a stainless steel cup wasmounted onto the robotic manipulator. When brought close tothe fabric, it mimics the capacitive signature of an astronautmoving near to a metallic object, such as a spacecraft struc-ture or metallic tools. While mounted on the manipulator, thecup is grounded to ensure an accurate representation of largespace structures that can be detected with a large capacitivesignal.

In addition, a rocky surface was imitated using assorted rocksmounted onto a polymer base using thermoplastic adhesive.These rocks, of various textures, sizes, and mineral com-position, represent a variegated mineral landscape, such asrocky artefacts on lunar and Martian surfaces, as well asrocky aggregates that form the surface of asteroids. This end-effector also provides an example of a high-abrasion materialthat astronauts may interact with, and can further be utilizedto evaluate the robustness of aerospace-grade e-textiles.

7. RESULTS & DISCUSSIONFindings / Impact

In Figures 7, 8, and 9, we visualize data from multipledatasets, highlighting the multimodal sensing capacity of theSpaceTouch sensate suit architecture. Piezoelectric fiberschange detected vibrations, piezoresistive fabrics providepressure readings, and conductive fabrics allow capacitivetouch detection.

In the stroke motion from a glove and rocky surface (Fig-ure 7), we observe that the end-effector creates oscillationsignatures as it passes over discrete piezoelectric vibrationsensors. In the case of the rocky surface, sequences ofmultiple oscillations are observed as multiple rocky piecesseparately stimulate piezoelectric vibration signatures as theypass over the piezoelectric fibers. This is consistent withphysical manipulation and the sensations that an astronautmay encounter as their suit rubs against a rocky surface oranother astronaut touches their suit. The piezoresistive pres-sure sensors also demonstrate sequentially peaking values,with pressure curves unique to the amount of time that themanipulator spends on each patch as it moves sideways acrosspatches on the fabric sample.

In the stroke motion using a metal surface (Figure 8), this hor-izontal translation is also represented in the capacitive touchdata: while contact with a conductive surface is detected, thecapacitive touch channels report a binary “1”; when there isno surface conductivity, a binary “0” is returned. Capacitive

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Figure 6. The robotic test setup with glove arm motions (left) and end-effectors (right).

Figure 7. Comparison between piezoelectric and piezoresistive response for a glove stroke motion vs. rock strokemotion. While the piezoresistive data is qualitatively similar, the rocky surface induces longer duration piezoelectric

ringing.

touch contact with a metallic surface also corresponds acrossmultimodal channels, to the detected piezoresistive pressure.For example, capacitive touch is detected while force is alsodetected on the corresponding piezoresistive patch. As theend-effector moves across the fabric, different segments re-port detecting a touch. In this way, the motion of a conductiveor capacitive surface can be ”tracked” across the textile, andused in conjunction with piezoresistive pressure sensing toform a human-computer interface through the textiles integralto the suit.

In the impact motion from metallic and rocky surfaces (Fig-ures 8 and 9), we observe that short, high-amplitude impulsescreate uniform pressure signals, focused on one main pad

segment (red line) but also providing transient signal spikesin multiple channels. There are low levels of ambient piezo-electric vibration, with observed spikes consistent with briefimpacts. Uniquely, the ”bounce” from a falling object in agravitational environment creates a dual-spike signature forstrong impacts. Such signatures can be used to additionallycharacterize environmental properties as well as the physicalproperties of stimuli experienced by astronauts.

For the rocky surface, as expected, there is little variation inthe capacitive touch detection, in the absence of any largeferromagnetic occlusions. Such signatures can be utilizedto further detect and differentiate between different forms ofstimuli, and provide a basis with which to automate stimulus-

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Figure 8. Comparison between tapping and stroking gestures for metallic surface. A tapping gesture induces a higheramplitude piezoelectric response and more localized capacitive response across two channels, whereas the stroking

gesture results in a smaller amplitude piezoelectric response and time-delayed capacitive response.

detection algorithms in an intelligent SpaceTouch sensateskin.

To provide estimates of the sensitivity of the SpaceTouchtextile-based sensors to different forms of stimuli, referencedata for the lower bounds of successful proximity and pres-sure detection were collected from each of the end-effectors.This data, shown in Table 1, highlights the sensitivity of themultimodal sensing approach: capacitive and metallic objectscan be detected in proximity to the astronaut and contactdetected at zero nominal force; even light touches with lowforce can be detected from other stimuli such as rocky sur-faces and gloves. In the appendix, we additionally providereference data on manual stimulation using a bare humanhand. We show that the e-textile can detect hand approachfrom up to 10 cm away, as well as detect a hand slidingover the textile through the subsequent touch (capacitive) andpressure (resistive) change (see Figures 10 and 11).

Haptic Actuation Strategies

Continuing the integration of haptic actuation as offered inour first prototype, we have identified factors to optimize forimproved haptic sensory conduction, including:

• mapping of sensing modalities to unique haptic signatures• differentiation of haptic signatures for disparate stimuli• optimal distribution and localization of haptic actuators for

different locations on the skin

We propose a modality-to-actuation mapping scheme thatcontrols the intensity of vibration from an eccentric-rotating-mass (ERM) motor as a function of multimodal sensor inputs,

as follows:

I(v, r, p) =

taps where T ∝ 1

p, if not touched (r = 0 or p > 0)

C1 ∗ v + C2 ∗ r, when touched (r > 0 or p = 0)

whereI = intensity of vibration

v = piezoelectric vibration signal

r = piezoresistive pressure measurement

p = capacitive proximity measurement

C1, C2 are scaling constants

Using this scheme, gradually increasing proximity of a ca-pacitive or metallic object can be represented as a series of“tap” sensations (achieved with short-duration activation ofthe motor for brief impulses) where the frequency of thetaps increases as the object comes closer to the skin, similarto the auditory indicators of ultrasonic obstacle-proximitywarnings in automobiles. Once a stimulus is in contactwith the spacesuit, haptic actuation can be comprised ofvibration impulses/fluctuations based on piezoelectric vibra-tion impulses, combined with a consistent baseline vibrationintensity proportional to the pressure intensity detected by thepiezoresistive textile sensors.

Following established two-point discrimination guidelinesthat outline spatial acuity of differentiating haptic stimuliacross the human body [27], we propose the placement of

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Figure 9. Repeatability study for 10x trials showing thesimilarity of multi-impact data from piezoelectric,

piezoresistive, and capacitive proximity channels. Minorvariability in the data can be attributed to widetolerances associated with robotic arm motion.

Stimulus Type Proximity Threshold Pressure ThresholdHand 10cm 0N*Glove 0.2cm 0.3NRocky 0.7cm 0.3N

Metallic 1.8cm 0N*

* capacitive touch detection at zero nominal force

Table 1. Sensor calibration: reference for proximity andpressure detection for different end-effectors.

haptic actuators with interstitial distances of 2-5cm in areasof tactile significance, such as the forearm and upper arm.Such placement can also facilitate the utilization of semi-rigid liquid cooling channels to aid in vibration conductionover a larger surface area, or the placement of wiring andelectrical connections in lines of non-extension throughoutthe suit [28].

8. FUTURE WORK / VISION FOR TEXTILESImplementation Steps

The current prototype is estimated to match a NASA Technol-ogy Readiness Level (TRL) of 3: an experimental proof-of-concept of characteristic technologies. In order to reach flightqualification (TRL 8), any fabric sensor mounted exterior tothe suit will require demonstrated robustness to the relevantenvironment. In Low Earth Orbit, any exposed electronicsshould fulfill the following suggested guidelines:

• Ensure sufficient shielding from noise induced by the highlycharged environment, such as by using shielded cabling.

• Ensure grounding of any exposed electrically conductivematerial, to prevent voltage-biasing of the suit or sensors.

• Ensure that materials used are characterized in a vacuum

chamber for their vacuum outgassing properties, both in orderto meet NASA standards and to ensure that outgassing doesnot substantially alter the functioning of the sensors overtime.

• Ensure that exposed materials are resilient to atomic oxygenerosion while remaining mechanically flexible. If necessary,surfaces can be coated or covered with resilient materials.

• Ensure that sensor function is characterized as a function oftemperature: maximum and minimum operating temperatureshould be specified and referenced relative to expected tem-perature exterior to the suit, where temperatures can reachextremes (-150 ◦C to 120 ◦C at worst) and fluctuate quicklyas the spacecraft enters and leaves sunlit regions.

Under such harsh environments, materials with superior tem-perature resilience are preferred; thermally absorptive oremissive coatings can help to regulate internal temperature.Active thermal control systems may be integrated, e.g. usingresistive heating elements and thermal radiators to regulatethe external suit’s temperature. For spacesuits operating onrocky surfaces, abrasion resilience is a critical additionalconsideration.

While the Beta cloth fabric used in prototype #1 is regu-larly used on persistent orbital spacecraft and on Apollo-era suits, Ortho-fabric (a Nomex, Gore-tex and Kevlar blendthat balances mechanical flexibility and resilience) is alsocurrently commonly used as a spacesuit outer layer. Furthercharacterizations can explore tightly-coupled integrations oftextile sensors with alternative base layers constructed ofmaterials such as Ortho-fabric, especially in conjunction withhaptic actuation.

Further work in haptic actuation can include the developmentof textile-based haptic actuators to complement our proto-type, as well as implementing and characterizing proposedhaptic actuation strategies. We also aim to further explorevarious sensor-actuator integration strategies, networked in-fabric communication, and flexible power distribution tech-niques and textile topology to realize a large-surface-areasensate skin that can cover an astronaut’s whole body [29],[30].

9. CONCLUSIONSpaceTouch is a conceptual prototype motivating the use ofelectronic textile technology for enhancing the situationalawareness, operational safety, and general wellbeing andconnectedness of astronauts. We have described some of thekey technical considerations and candidate sensing modalitiesin service of this vision, and have further demonstrated thisconcept by constructing an e-textile sensate skin prototypeand validating multimodal sensing capabilities as they corre-spond to human touch sensations. In this way, SpaceTouchreflects and seeks to advance the mission to augment humanspaceflight by enhancing human sensory capabilities andcounteracting the sensory insulation of conventional pressur-ized spacesuits.

ACKNOWLEDGMENTSThe authors thank the Responsive Environments Group at theMIT Media Lab. This work was supported by the MIT MediaLab Consortium.

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BIOGRAPHY[

Syamantak Payra is an MIT under-graduate studying Electrical Engineer-ing and Computer Science. His interestslie at the junction of science, engineer-ing, and human experiences, and he ispassionate about creating technologieswith human impact. His previous re-search has included developing roboticorthotic devices for gait rehabilitation,biomedical sensing for health monitor-

ing, and computational fibers for intelligent fabrics, withadditional interdisciplinary work across fields like materialsscience, microbiology, and public policy. He is a US Presi-dential Scholar, and the MIT Lincoln Laboratory has namedMinor Planet 33610 “PAYRA” in recognition of Syamantak’sinternational-level awards for scientific research.

Irmandy Wicaksono is a PhD studentin the Responsive Environments Group,MIT Media Lab. He earned his MS inElectrical Engineering and InformationTechnology at the ETH Zurich, workingclosely with the Wearable ComputingLab. He was involved in several compa-nies and institutions such as StudioXOfor Haus of Gaga, Atmel, and KAUST,in areas such as fashion technology and

consumer electronics, from mechatronic dress to stretchableelectronic patches and fabrics. His current interests includefabrication, manufacturing, and interaction techniques ofunconventional electronics for ubiquitous sensing, actuation,and energy harvesting. He has been working closely withtextile and flexible electronics factories, making a strongconnection between research and manufacturing.

Juliana Cherston is currently pursuinga PhD in the Responsive EnvironmentsGroup at the MIT Media Lab. The tech-nical emphasis of her doctoral degreestraddles aerospace engineering, dis-tributed sensing, and electronic textiledesign - she is bringing electronic textiletechnology to the exterior of spacecraftand spacesuits for the first time. She hasinterned at Made in Space developing

3D printing technology for Low Earth Orbit, and in MIT’sAerospace Engineering department developing electronicsfor a PCB-scale satellite. Previously, she earned a B.A. inphysics at Harvard.

Cedric Honnet is a Visiting Scientistin the Responsive Environment Group,MIT Media Lab. With a backgroundin Embedded Systems Engineering anda decade of industry experience, hehas been exploring the connections be-tween Physical Computing, Interactivityand the Arts by travelling the world ofresearch labs and hackerspaces. Heworked as a Firmware Engineer and

“InterHacktivist” in the Silicon Valley, co-founded a coupleof companies developing Tangible Interfaces, and createdinteractive systems/installations worldwide. He has workedon eTextile music controllers, augmented immersive systems,interactive art pieces, modular implants, 3D positioning sys-tems and many other Open Source projects.

Valentina Sumini is Visiting Profes-sor at Politecnico di Milano and Re-search Affiliate at MIT Media Lab inResponsive Environments and Space Ex-ploration Initiative. She develops designand architectures to sustain human lifein extreme environments on Earth andenable human space exploration in LowEarth Orbit, on the Moon and Mars.Her Space Architecture research focuses

on inventing new computational design methods for multi-performance habitats, soft-robotic prosthetics to enhancemobility and dexterity in microgravity, and construction tech-niques using in-situ resources. Her passion is in advancinghuman performance during deep space exploration.

Joseph Paradiso is the Alexander W.Dreyfoos (1954) Professor in Media Artsand Sciences, where he serves as theAssociate Academic Head and directsthe Media Lab’s Responsive Environ-ments group, which explores how sensornetworks augment and mediate humanexperience, interaction, and perception.Paradiso worked as a Tufts undergrad(where he received his BS in electrical

engineering and physics summa cum laude in 1977) onprecision inertial guidance systems at Draper Lab, thencompleted his PhD in physics at MIT in 1981, while workingwith Prof. S.C.C. Ting’s group at CERN in Geneva as aK.T. Compton Fellow. After two years developing preci-sion drift chambers at the Lab for High Energy Physicsat ETH in Zurich, he joined the NASA-affiliated group atDraper Laboratory, where his research encompassed space-craft control systems, image processing algorithms, under-water sonar, and precision alignment sensors for large high-energy physics detectors. He joined the Media Lab in1994, where his current research interests include wirelesssensing systems, wearable and body sensor networks, energyharvesting and power management for embedded sensors,ubiquitous/pervasive computing and the Internet of Things,human-computer interfaces, space-based systems, and inter-active music/media. He has written over 350 publicationsand frequently lectures in these areas. In his spare time,he enjoys designing/building electronic music synthesizers,composing electronic soundscapes, and seeking out edgy andunusual music while traveling the world.

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APPENDICES

Figure 10. Manual stimulation: horizontal strokemotion.

Figure 11. Manual stimulation: tapping.

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