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Acta Astronautica

Acta Astronautica 90 (2013) 378–390

0094-57

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journal homepage: www.elsevier.com/locate/actaastro

Dual rover human habitation field study

Harry L. Litaker Jr.a,n, Shelby G. Thompson a, Richard Szabo a, Evan S. Twyford b,Carl S. Conlee b, Robert L. Howard Jr.c

a Lockheed Martin, 1300 Hercules, Mail Code C46, Houston, Texas 77058, USAb MEI Technologies, 2525 Bay Area Blvd, Suite 3000, Houston, Texas 77058, USAc NASA Johnson Space Center, 2101 NASA Parkway, Mail Code SF3, Houston, Texas 77058, USA

a r t i c l e i n f o

Article history:

Received 17 June 2011

Received in revised form

8 December 2011

Accepted 29 March 2012Available online 7 July 2012

Keywords:

Habitation

Space Exploration Vehicle

DRATS

Volume

Human factors

65/$ - see front matter & 2012 IAA. Publishe

x.doi.org/10.1016/j.actaastro.2012.03.027

esponding author. Tel.: þ1 281 483 9870; fax

ail address: harry.l.litaker@nasa.gov (H.L. Lita

a b s t r a c t

For the last 3 years, the National Aeronautics and Space Administration (NASA) has

been testing a pressurized rover prototype in the deserts of Arizona to obtain human-

in-the-loop performance data. This year’s field trial consisted of operating two rovers

simultaneously while embarking on two 7-day flight-like exploration missions. During

the 2010 Desert Research and Technology Studies (DRATS) at Black Point Lava Flow and

SP Mountain in Arizona, NASA human factors investigators, in cooperation with other

engineers and scientists, collected data on both the daily living and working within and

around the Space Exploration Vehicle (SEV). Both objective and subjective data were

collected using standard human factors metrics. Over 305 h of crew habitability data

were recorded during the field trial with 65 elements of habitation examined.

Acceptability of the vehicles over the course of the missions was considered satisfactory

by the majority of the crews. As with previous testing, habitation was considered

acceptable by the crews, but some issues concerning stowage, Waste Containment

System (WCS) volume, and sleep curtains need to be considered for redesign for the

next generation vehicle.

& 2012 IAA. Published by Elsevier Ltd. All rights reserved.

1. Introduction

The purpose of this evaluation was to obtain human-in-the-loop performance data on the current SpaceExploration Vehicle (SEV) Cabin 1A and Cabin 1B config-urations in a simulated exploration environment and toapply this knowledge to further enhance the vehiclecapabilities for forward designs. The study was conductedfor a total of 14 days, divided into two 7-day missions.This evaluation was a critical next step in determining theproper internal and external vehicle configuration. Alimitation to the study of habitability within the vehiclewas the lack of crew isolation due to the design of the

d by Elsevier Ltd. All right

: þ1 281 483 1847.

ker Jr.).

analog test. With this in mind, the field study enhancedthe human performance data already collected during the3-day desert field trials, at Black Point Lava Flow inOctober 2008 [1,2] and a 14 day field trial in September2009 [3,4]. The value of such field testing was, first, toincrease the sample size for understanding habitabilitywithin the rover Generation (GEN) 1 cabins. Next, inves-tigators examined any developing trends that may needto be addressed and brought forward as improvements forthe rover GEN 2 vehicles. Finally, investigators wanted togain understanding of the slight differences in designbetween Cabin 1A and Cabin 1B. Cabin 1A was consideredthe minimal functional vehicle and Cabin 1B had beenmodified to improve certain areas of functionality withinthe vehicle. This was the first comparison of habitabilityof two simultaneously roving concept vehicles and gavedesigners early insights into system acceptability, usability,and functionality.

s reserved.

H.L. Litaker Jr. et al. / Acta Astronautica 90 (2013) 378–390 379

2. Materials and methods

2.1. Rover Cabin 1A and Cabin 1B vehicles

Both rovers are medium fidelity functional vehiclesthat are designed to provide the crew a safe haven fromthe hazardous environment of the lunar surface, a livingarea for multiple-day missions away from a lunar outpost,and a system that allows crew members to deploy rapidlyfor space suited scientific exploration of the surface(extravehicular activity). Using computer aided drawings(CAD) of Cabin 1A’s interior volume, the total pressurizedvolume is calculated at 10.8 cubic meters (m3) (381.4cubic feet (ft3)) with a net habitable volume (NHV) ofapproximately 8.6 m3 (303.7 ft3), resulting in about 79%functional volume. For Cabin 1B, the total pressurizedvolume is calculated at 11.9 m3 (420.2 ft3) with a NHV ofapproximately 9.7 m3 (342.6 ft3), resulting in about 85%functional volume. The difference between the two rovercabins is accounted for by the extra 1.06 m3 (37.4 ft3) ofvolume from a second side hatch, which was a designmodification for Cabin 1B after the 2008 field trials. NHVis defined as the total remaining volume available to crewafter accounting for the loss of volume due to equipment,stowage, and any other structural inefficiencies (nooksand crannies) that decrease functional volume [5]. Differ-ences between Cabin 1A (Fig. 1) and Cabin 1B are minor instructure but substantial with regard to suit port

Fig. 1. Rover Cabin 1A (foreground) and Cabin 1B (background) during

dual operations during DRATS.

Fig. 2. The left photo is a satellite image of SP Mountain and Black Point Lava Fl

the rovers.

operations, interior stowage, docking aspects, cockpit layout,sleep station assembly and stowage, and aft enclosureoperations.

2.2. Participants

Eight participants, including three being flight-experi-enced astronauts, one astronaut representative, and fourprofessional geologists, operated and interfaced with allthe internal and external systems of both rovingvehicles—Cabin 1A and Cabin 1B—while on two 7 daysimulated exploration missions. Six men and two womenparticipated in the 2011 field trials. Crews 1A, 1B and 2Awere all-male crews whereas Crew 2B was the first roverall-female crew. All participants received familiarizationtraining on all internal and external systems of thevehicles. In preparation for the desert trials, they tookpart in three dry run tests at the Johnson Space Center’s(JSC) Rock Yard. Before the testing began, all participantssigned consent forms and were briefed as to the nature ofthe evaluation and tasks expected of them.

2.3. Test environment

The test environments for the 7 day dual rover fieldtrials were both the SP Mountain and the Black Point LavaFlow test sites, approximately 64.6 kilometers (40 miles)north of Flagstaff, Arizona (Fig. 2). This test site has a widevariety of geologically relevant surface features whichpresented many opportunities to evaluate human perfor-mance with both the intra vehicular activities (IVA) on therovers and extravehicular science and exploration activ-ities with the rovers. Surface characteristics includedslopes with an approximate range of 6–251 of verticalvariation from top to bottom, soil mechanics ranging fromlose grain to hard-packed, surface properties ranging fromflat/smooth to rocky, and some minimal vegetation. SPMountain is the youngest volcanic feature in the northernSan Francisco volcanic field with an age of 71,000 years.The volcanic cone is 1200 m (3900 ft) across at the baseand 250 m (820 ft) tall.

2.4. Evaluation methods

Desert Research and Technology Studies (DRATS)science team experts, working with the JSC Mission

ow test site. The right photo is a portion of the actual terrain traversed by

H.L. Litaker Jr. et al. / Acta Astronautica 90 (2013) 378–390380

Operations Directorate (MOD) developed a high-fidelityflight-like traverse mission timeline to ensure that theapplication and assumptions remained consistent withthe current exploration architecture models. The traverseplan included detailed timelines and traverse stationseach with specific tasks associated with the scienceobjectives at those stations. ‘‘Get-ahead’’ tasks were alsoincluded in the traverse plan with secondary tasks thatcould be accomplished if the nominal tasks were com-pleted and the crew members were ahead of the missiontimeline by a predefined amount of time.

Quantitative human performance evaluations of thevehicle accommodations, docking activities, vehicle hand-ling characteristics, and aft deck operations were con-ducted on an ongoing basis throughout the 14-daymission. These were conducted by the JSC UsabilityTesting and Analysis Facility (UTAF), which collectedhuman performance data while crew members performedthe predefined scientific tasks, maintenance and logisticstasks, operated the rover during traverse relocation, andlived in the rover during off-duty periods. Performance,functionality, and human–vehicle interfaces wereassessed using qualitative questionnaires with ratingsbased on a 10-point acceptability scale. The subjectivequestionnaires were electronic and incorporated into themission timeline software for both vehicles.

3. Calculations

The human factors data collected were measured on apseudo-continuous scale and analyzed using descriptivestatistics. The 15 customized questionnaires used toevaluate the SEVs and human performance used a 1–10Likert acceptability scale, where ‘‘1’’ was totally accepta-ble with no improvements necessary and ‘‘10’’ was totallyunacceptable with major improvements required. Thequestionnaires were recorded by the subjects on specificdays throughout the mission. Criteria for questionnaireratings of r4 indicate that the habitability of the vehiclewas acceptable. However, even where mean values arer4 were measured, the reasons for any specific datapoints 44 were recorded to help inform the redesign ofany system within the vehicle [1,3]. Each questionnairerepresented a different habitat aspect; thus, when takenin combination, the ratings could assist in developing acomplete human performance assessment for a particular

Fig. 3. The left photo illustrates the crew in Cabin 1A working in the vehicle’s

Cabin 1B after a few days of working/living in the vehicle.

habitable task or set of tasks. Detailed field notes of allplanned and unplanned habitat activities were collecteddaily as well. A post-mission interview was conductedwith each participant following each 7-day trial. Objectivedata were collected using operation time for mating,docking, and habitability when crew members were onand off duty, and cabin temperature sensors for recordingthe cabin environment. Though the field trial examinedthe vehicles 186 operational elements, this paper willonly discuss the habitation of eight crew members withinthe rovers over two 7-day missions.

4. Results and discussion

4.1. Crew daily habitation

For a space or volume to be habitable to a human,three elements must be considered—visual, kinesthetic,and social logic [6]. The space which determines theoperational environment and overall living environmentfor an individual, and affects the quality of productivity ofthe crew and daily life onboard a space vehicle is knownas the space of habitation. Of the 186 operational ele-ments tested in the field, 65 elements (35%) pertained tohuman habitation (Fig. 3).

Total habitation time recorded by the crews , whilethey were in the rovers, averaged approximately 305hours (Table 1). Each vehicle recorded an average of 152h and 30 min of habitation time per crew. The crewsrecorded an average time of 14 h and 23 min spentdriving the vehicles. This time consisted of general driv-ing, aft driving, and traverse driving. IVAs, such as science/navigation and communications, averaged 11 h and59 min per crew. Team workload usually consisted of theastronaut driving and the geologist doing the IVA items.The workload was equally divided between the two crewmembers per vehicle on a mission with the astronautsdriving vs. the geologist interfacing with the displays andcontrols. The four crews recorded an average of 35 h and59 min for EVA during the mission, which includes egress,ingress, boot-on-the-surface, EVA science, and EVA trans-lation. As for on-duty time, the crews averaged 48 h and6 min whereas they averaged 104 h and 23 min in off-dutytime. Thus, the crews worked 32% of the time and rested68% of the time.

habitat. The right photo illustrates a crew member’s personal station in

H.L. Litaker Jr. et al. / Acta Astronautica 90 (2013) 378–390 381

All four crews deemed the volume for meal prep andeating, water dispenser accessibility, volume for house-cleaning, and volume to limit station cross-contaminationas acceptable with only minor improvements desired(Table 2). Crews report they mostly ate their meals inthe front cockpit seats (Fig. 4). They noted that it would benice to have a bit more space. The crew also indicatedaccessing the water dispenser from the seats was goodbut noted that, once a person had left their seat, it was alittle awkward to reach the dispenser because it was so

Table 1Breakdown of mission time during field test.

Type of element Average time spent

during 14 d (hh:mm:ss)

Driving 14:23:30

IVA (other than driving) 11:59:15

EVA 35:59:45

On-duty 48:06:41

Off-duty 104:23:19

Habitation per vehicle 152:30:00

Total mission habitationa

(2 vehicles)

305:00:00

a Total mission habitation is for the SEVs only (12.7 days). The crews

worked in the HDU for 2 days. Day 7 was an 8-hour work day in the HDU

and Day 8 was only 4 hours because of rainy weather. The other 4 hours

for the HDU was made up on Day 14 after the rover mission officially

ended at 12:00:00.

Table 2Rating means for SEV internal daily food, hygiene, and waste containment sys

Elements

Access to food stowage

Volume for meal prep/eating

Accessibility to water dispenser

Volume to deploy/stow WCSb

Volume to use the WCS during sleeping hours without disrupting others

Adequacy of WCS privacy

Volume for waste/trash stowage

Odor of waste/trash

Effectiveness of the space bags for waste/trash compacting

Frequency of waste/trash removal using SPTM

Volume to limit cross-contamination

Volume for housecleaning

a n¼2 crew members per crew. Means were calculated across days for eacb SPTM, Suit Port Transfer Module; WCS, Waste Containment System.

Fig. 4. Cabin 1B crew member (left photo) and the Cabin 1A crew (right photo

meals in this area of the vehicle.

close to the floor. Volume for cleaning the vehicles wasgood; however, the crews stated more space would behelpful when accessing the floor panels.

Several elements were considered by some crews to beborderline whereas other crews deemed them acceptable.Of these elements, access to food stowage, volume forstowing and deploying the Waste Containment System(WCS), adequacy of WCS privacy, volume to use WCSduring sleeping hours, trash volume/stowage, odor oftrash, effectiveness of the Space Bags& and frequency oftrash removal with the Suit Port Transfer Module (SPTM)were the areas of concern among crews (Fig. 5). Crew 1A,indicated the Crew Transfer Bags (CTBs) were too full andit was difficult to put them back into the stowagecompartment under the bench seats. They also statedmore time was needed in the morning to get all the CTBssituated and the vehicle cabin ready for the day’s mission.Crew 2B in Cabin 1B reported that, even though foodaccess was mildly inconvenient, they would take out oneday’s worth of food and designated a compartment intheir soft locker so time was not spent on opening thebench seat. This crew also noted having all the foodplaced on one side of the cabin instead of two gave thembetter accessibility when a crew member comes back intothe cabin after an EVA.

All crews reported the volume was barely enough forusing the WCS during sleeping hours without wakingyour fellow crew member. They indicating that reducing

tem (WCS) operations.

SEV 1A crewa SEV 2A crew SEV 1B crew SEV 2B crew

5.83 1.25 2.67 4.50

3.17 1.50 2.17 4.00

2.67 4.00 3.00 3.00

4.50 2.25 2.67 4.33

6.00 5.00 4.50 5.33

6.00 5.00 3.83 4.83

2.33 5.75 2.33 4.67

4.00 5.25 4.00 5.83

3.00 1.00 3.00 4.80

2.33 1.25 4.25 7.20

2.33 3.00 3.20 4.20

3.17 1.25 2.33 3.20

h crew.

) eating lunch in the cockpit area. Crews reported they mostly eat their

Fig. 5. The left photo shows a crew member in Cabin 1A accessing the food. The food CTB is stored under the bench and it was difficult to get it out.

The right photo shows the Cabin 1B crew cleaning the WCS. Privacy and space were an issue with the WCS according to all the crews.

Fig. 6. The view of Cabin 1B’s deployed sleep stations and the WCS

limited access (currently at 0.55 m or 21.5 in.). Crews would like to add a

few more inches to the width of the aisle to prevent disturbing the

sleeping crew member when WCS operations are required at night.

H.L. Litaker Jr. et al. / Acta Astronautica 90 (2013) 378–390382

the bed section approximately 0.03–0.05 m (1–2 in.)would gain approximately 0.05–0.10 m (2–4 in.) more ofseat room (Fig. 6). Privacy using the WCS was consideredan issue with three out of the four crews with Cabin 1Acrew being the most annoyed. The crews reported that,when seated on the WCS, the large front windows madethem feel as if they were in a fish bowl and the time ittook to deploy the curtains could be improved. Odor wasalso a borderline factor with the WCS and trash. Crews inboth vehicles indicated that with the trash stowed underthe floor, the odor was not bad; however, even with threelayers of containment, with stowing human waste theodor became appalling (Fig. 7). Though use of suchproducts was not flight-like, crews reportedly used Feb-reeze& and air fresheners to combat the odor. They alsosuggested a fan duct system to be installed to vent odorout of the vehicles. As with previous missions, the crewsalso suggested increasing the frequency of Suit PortTransfer Module (SPTM) operations to every other day,as the odor started getting seriously noticeable arounddays 2 and 3. As for bagging the waste and trash, all crewsindicated the Space Bags& were too large and using thevacuum was too cumbersome due to power restrictions.They suggested using large Ziploc& bags instead.

Of the eight elements concerning stowage volumewithin the vehicles, five were considered acceptable byall four crews (Table 3). Volume of the personal softlocker, accessibility to the upper and lower portions ofthe personal soft locker, clearance while seated andaccessing the personal soft lockers were the areas thecrews approved for this duration of mission. Crews in theCabin 1A vehicle had only one soft locker per crewmember. They stated for the 7-day mission duration,one soft locker was adequate to stow their personal items.As for the crews in Cabin 1B, who they were given twosoft lockers per crew member, they stated the volume wasmore than adequate for a one week mission. Some crewmembers noted that the extra volume of the soft lockersmade it perfect to stow others items, thus, keeping benchand floor stowage down to a minimum. All the crewsliked the copious number of small cubby holes and statedthis made organizing one’s gear easier. Accessibility to thesoft lockers in Cabin 1B was not an issue and these crewsnoted there was enough room to maneuver. However,Cabin 1A crews noted some difficulty in accessing thelockers when both crew members were seated. It shouldbe noted that with Cabin 1A had only one side hatch,unlike Cabin 1B; thus, sharing the space is mandatory(Fig. 8).

Considered borderline by the crews the overall designof the soft lockers, location of the vehicle stowage areas,and accessing stowed items on the other side of a privacycurtain. Crew 1A had the strongest opinions about theoverall soft locker design. They stated the lockers tendedto slide off the rails and into the aisle when the rover wassufficiently tilted in the proper direction (locker side high)on slopes 4101. Other crews noted this tendency as welland suggested some type of a locking tab on the rails toprevent the lockers from sliding out. Crews also notedthat the overall locker system worked great, the cubbyholes were of a good size and the clear covers made iteasier to keep track of all of one’s items. The 16 separatevolume compartments made organization of crew geareasy to manage and set up (Fig. 9). Crews also suggestedreplacing the Velcro& with quarter turn fasteners for aquieter entry at night or early morning. As with last year’strial, reconfiguration was an issue with no place to stowthe soft lockers out of the way when preparing for an EVA.Location of stowage areas within the vehicles was con-sidered borderline for three out of four crews. Crews 1A

Fig. 7. The crew in Cabin 1B working trash operations. The left photo shows the SPTM attached to the suit port while the crew member in the right photo

prepares the trash for the SPTM. Trash operations were every three days; however, all the crews suggested making this operation more frequent.

Table 3Rating means for SEV internal volume and stowage.

Elements SEV 1A crewa SEV 2A crew SEV 1B crew SEV 2B crew

Volume of personal soft locker hatch stowage 3.50 1.00 1.50 3.00

Access to lower personal soft locker 4.17 2.50 1.33 3.17

Access to upper personal soft locker 4.17 2.50 1.33 2.00

Clearance when seated at personal soft locker 3.67 2.00 1.67 3.00

Clearance when accessing personal soft locker 3.67 2.00 1.83 3.00

Overall design of personal soft locker 5.67 2.50 2.50 3.50

Location of vehicle stowage areas 5.17 6.00 3.67 4.83

Access to items stowed on other side of privacy curtains 2.00 2.00 6.50 4.00

Volume of SEV layout for 2 crews/14 days 2.50 2.00 2.75 5.00

Volume of SEV layout for 2 crews/30 days 2.50 2.25 4.33 6.50

Overall habitable living of the SEV 4.33 3.00 3.00 4.83

a n¼2 crew members per crew. Means were calculated across days for each crew.

Fig. 8. Crews in both rovers like the extra personal volume of the soft lockers. The left photo shows the Cabin 1B crew using the clear doors to identify

certain items. The right photo illustrates the volume taken up by reconfiguration in Cabin 1A. Note the soft lockers located in the aisle way.

H.L. Litaker Jr. et al. / Acta Astronautica 90 (2013) 378–390 383

and 2A stated the stowage in the cockpit was lacking.They reported spaces within the cockpit were not utilizedto prevent various items from being either stacked on thefloor or in the armrest area. They suggested adding softstowage pockets over the side windows to store smaller,light-weight items, such as snacks or a field notebook. Asfor Cabin 1B, crews noted the under bench stowage andsoft lockers conflicted with side hatch operations and thatreconfiguration of the cabin stowage was done numeroustimes throughout the day.

Three out of four crews indicated the internal volumeof the SEV layout for two people during a 14-day and 30-day mission and the overall habitable living of the SEV asacceptable (Fig. 10); only Crew 2B deemed them border-line. The crew stated the vehicle would be tolerable for a 2week mission, especially if the crew develops a routine for

stowing items. However, they also thought the longermission could be an ordeal if getting out for EVA was notpossible. Some crew members commented on living inAntarctica for 6 weeks in a Scott tent, which was abouthalf the volume of the rover. They indicated rarely neededitems were stowed outside, and crew members did nothave to eat and sleep within 0.91 m (3 ft) of the toilet andcould go outside easily, conveniences not available with aplanetary exploration rover. As for a 30-day mission,crews were less sure about doing this long mission andthought it would be tough given the current vehiclevolume.

In order for crew members to maintain muscle mass,strength, and endurance, and their ability to recover fromstrenuous tasks, confined postures, and minor muscleinjuries, the SEVs are required to provide equipment and

H.L. Litaker Jr. et al. / Acta Astronautica 90 (2013) 378–390384

space for the crews to perform both aerobic and resistiveexercise for a minimum of 30 min each day [7]. In thisyear’s field trial, Cabin 1A had a new exercise devicecalled the air spring rower which was originally devel-oped for the Crew Exploration Vehicle (CEV) spacecraft.Cabin 1B crews used the Glenn Research Center’s (GRC)

Fig. 9. One crew member’s soft locker in Cabin 1B. Crews like the 16

cubby holes with clear fronts.

Fig. 10. Crew members in Cabin 1A relaxing after a long duty day. Note

how the crew adjusted the seat backs for comfort.

Table 4Rating means for SEV general exercise elements.

Elements

Access to exercise equipment

Setup of the exercise equipment

Volume for 1 crew performing resistive exercise within rover

Accessibility of non-exercising crew to other stations within rover during res

exercising

Volume for 1 crew performing aerobic exercise within rover

Accessibility of non-exercising crew to other stations within rover during aero

Stowing of the exercise equipment

Stowage volume for exercise equipment

Overall ability to exercise in the rover

a n¼2 crew members per crew. Means were calculated across days for eac

ergometer, with some modifications based on data col-lected in 2009, as well as a new system for resistiveexercise. Investigators examined nine general elements ofexercise across the vehicles with two special elements forthe Cabin 1A device and five special elements for theCabin 1B device. Of the nine general exercise elements,the crews deemed access to the exercise equipment andthe overall ability to exercise in the rovers as acceptable(Table 4). Generally, all the crews agreed the location forstowing the exercise equipment under the floor was goodand that the interior volume of the vehicles offered a crewmember several possibilities for exercising without theequipment (i.e. push-ups, sit-ups, etc.;Fig. 11). However,all the crews indicated it was somewhat awkward toaccess the equipment from the floor stowage compart-ment and the weight of the equipment made lifting theequipment out of the floor a little difficult. As for theoverall ability to exercise in the vehicles, crews wereimpressed with how the vehicle, interior, and exerciseequipment designers were able to use such a small spacewith a tight fit to give the crews the ability to get a goodworkout.

General exercise elements that were considered bor-derline by some or all of the crews included the setup ofthe exercise equipment, the volume for one crew memberto perform resistive or aerobic exercise within the vehicle,accessibility of the non-exercising crew member to othervehicle stations during resistive or aerobic exercise, stow-ing of the equipment, and the amount of stowage volumefor the equipment. Crews 1A and 2A deemed the setup ofthe equipment as borderline. They were testing the newair spring rower. Both crews reported no technical manualwas provided to instruct them on how to set-up thedevice. Another issue the crews in Cabin 1A faced washow to charge the gas cylinder to achieve a desiredamount of resistance. As for the ergometer in Cabin 1B,the crews indicated the device could be set-up within aminute or so and they like this device much better thanthe ones on the Space Shuttle and the International SpaceStation (ISS; Fig. 12). The cue card, which accompaniedboth devices, aided the crews in stowing the equipmentback into the CTB; however, the crews did suggestanother cue card for assembling the equipment. Cabin1A crews also reported borderline ratings with stowingthe equipment and the volume of that stowage space.

SEV 1A crewa SEV 2A crew SEV 1B crew SEV 2B

crew

2.67 2.00 3.00 3.33

5.00 4.75 2.00 3.67

3.33 2.50 3.00 6.00

istive 3.33 4.25 4.67 5.00

3.67 6.50 3.00 3.33

bic exercising 3.33 4.50 5.25 4.67

5.00 3.00 3.00 4.00

2.67 4.75 3.25 3.67

3.33 2.00 3.75 4.00

h crew.

Fig. 11. The crews in Cabin 1B were able to accomplish all types of exercises without any devices using the volume within the vehicle.

Fig. 12. The left photo shows the ergometer setup in Cabin 1B. The center and right photos show the crews in Cabin 1B exercising with the rover

ergometer.

Table 5Rating means for specialty elements for the air spring rower.

Elements SEV 1A

crewa

SEV 2A

crew

Design of gas spring rower to perform

resistive exercise

3.33 6.25

Design of gas spring rower to perform

aerobic exercise

3.33 6.50

a n¼2 crew members per crew. Means were calculated across days

for each crew.

H.L. Litaker Jr. et al. / Acta Astronautica 90 (2013) 378–390 385

They stated the long length of handle for the rower madeit difficult to stow in the CTB. The handle usually stowedseparately under the floor, much like the ergometer seat.Stowing the ergometer in Cabin 1B posed no issuesaccording to the crews. Access of the non-exercising crewmember during aerobic and resistive exercise was con-sidered borderline by three out of four crews. Crews inboth vehicles reported the non-exercising crew memberwas limited to the cockpit area while the other exercisedin the aft section. Crews in Cabin 1A vehicle performedlimited aerobic exercise with the rower. Crews in Cabin1B noted the volume between the benches was adequatefor pedaling the ergometer but seat distance from thepedals was fairly long. All crews stated that as long as theexercising crew member remained in the aft sectionwhile the non-exercising crew member remained in thecockpit, both aerobic and resistive exercise could beaccomplished.

Of the specialty exercise elements for each exercisedevice located in the vehicle, Cabin 1A housed the airspring rower while Cabin 1B housed the ergometer.Design of the air spring rower to perform resistiveexercise and design of the device to perform aerobicexercise were scored by the crews. Crew 1A rated bothof these elements as acceptable. Crew 2A rated both ofthese elements as borderline (Table 5). They stated the

device was designed more for resistive exercise thanaerobic. Setting up the device and needing a clear proce-dure for charging the gas cylinder that changed theresistance to the user’s preference were the major issueswith the device. Both crews indicated that having a cuecard for setting up the device and configuring it was badlyneeded (Fig. 13).

The crews using the ergometer in Cabin 1B deemedfour of the five specialty elements as acceptability. Theseincluded elements such as stability of the seat, adjustableof seat, design of the ergometer to perform resistiveexercise and design of the ergometer to perform aerobicexercise (Table 6). Seat comfort was considered by Crew

Fig. 13. The left photo illustrates a crew member in Cabin 1A setting up the air spring rower. The right photo illustrates a crew member starting to

exercise with the air spring rower in Cabin 1A.

Table 6Rating means for specialty elements for the ergometer.

Elements SEV 1B crewa SEV 2B crew

Comfort of the exercise seat 5.50 3.33

Stability of the exercise seat 3.00 4.00

Adjustability of the exercise seat 3.75 3.33

Design of ergometer to perform

resistive exercise

3.00 3.00

Design of ergometer to perform

aerobic exercise

2.75 3.33

a n¼2 crew members per crew. Means were calculated across days

for each crew.

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1B as borderline with improvements warranted whereasCrew 2B deemed it acceptable with minor improvementdesired. As for the stability of the exercise seat, bothcrews indicated it was fairly stable; however, Crew 1Bwas concerned that a shorter statue person could havesome trouble reaching the pedals even with the seat fullforward. One crew member stated that this distancewould be difficult for a person who was shorter than1.75 m (5 ft 10 in.). Crew 2B noted that when the erg-ometer was bolted to the vehicle’s floor panel, the paneltended to move up and down when they pedaled harder.They also stated the noise of the device was annoying andthe seat tended to move back and forth slightly duringexercise. Both crews reported the adjustability range ofthe seat was limited but workable. Crew 1B commentedthat it was somewhat difficult to reposition the seat dueto the Velcro&. Both crews also indicated they wantedstraps to ensure the back of the seat remains straight.Ergometer design for both resistive and aerobic exerciseswas considered by the crew as a ‘‘good solid workout.’’They thought the adjustability of the resistive levels wasgood and that combining aerobic and resistive exerciseswas a solid way to exercise most of the body. Crews likedthe fact that the device needed no power or tools forsetup, setup and takedown were quick, and using thebungee straps with the ceiling strap in the vehicle’sceiling made for an effective resistive workout. In fact,one crew member stated ‘‘the combination of the cycle and

the bungees made for a good workout in only about

20 minutes.’’ The crews also like the variety of the

accessory kit provided for the ergometer. Improvementsneeded for the ergometer consisted of relocating thedevice’s display so the crew can reach the controls with-out having to stop exercising, which meant the exercisesession had to be reset. They suggested adding a remote/cable controller to the device so that it could be placednext to the user.

Both environmental and architectural factors canaffect the quality of sleep a crew member receives duringtheir mission. During the two 7 day missions, crews fromboth vehicles considered the 13 elements of their sleepstation. The crews considered nine of these elements asacceptable (sleep station curtains easily deployable byone crew, volume of the sleep station, layout of the sleepstation, volume for personal privacy, accessing personalitems, ingress/egressing from a deployed sleep station,and overall design) (Table 7). The crews noted deployingthe sleep curtains was quick and easy; however, whenstowing them back it was a two person task. This is inconcurrence with the comments from the last two fieldtrials [4,2].

Volume of the sleep station was reported by mostcrews as acceptable with minor improvements desired.One crew member commented, ‘‘I was surprised at how

much room I have.’’ However, there was some concernfrom crews about taller crew members. Both crew mem-bers of Crew 1B were 1.83 m (6 ft) or taller and stated fora 1.83 m (6 ft) crew member the sleep station was justlong enough with the feet touching against the suit porthatch. A 1.86 m (6 ft 1 in.) crew member noted the sleepstation as barely adequate. Overall the volume from thesleep station provided privacy for the crew members butthey did not want the volume any smaller (Fig. 14). Crewsliked the layout of the sleep station, reporting having thesoft lockers within the station was a nice touch and easilyaccessible to all personal items. They did note pockets onthe walls would be nice to store earplugs, eye shades, andflashlights which would be within easy reach of thesleeper. Another suggestion was to add a small windowto the forward sleep curtain to enable access to the criticalcontrols. Ingressing and egressing the sleep station wasdeemed by all the crews as adequate. However, the crewssuggested composing the side curtain into two panels forease of egressing/ingressing the sleep station while goingto the WCS without disturbing the other crew member.

Table 7Rating means for SEV sleep elements.

Elements SEV 1A crewa SEV 2A crew SEV 1B crew SEV 2B crew

Sleep station curtains easily deployable by 1 crew 2.50 2.00 2.33 3.00

Ease of seat reconfig for sleep station setup 6.17 2.67 3.50 4.33

Volume for crew sleep station 2.00 1.67 2.33 2.67

Sleep station layout 3.00 1.33 3.00 2.67

Volume for personal privacy 2.00 1.67 2.17 2.67

Sleep quality while resting in rover 3.50 2.83 3.33 5.83

Lighting quality within deployed sleep station 3.33 1.67 3.00 5.33

Lighting control within deployed sleep station 3.33 2.00 5.33 6.83

Access to personal items from within deployed sleep station 2.00 3.17 3.17 3.00

Ease of ingress into deployed sleep station 2.00 1.67 3.67 3.50

Ease of egress from deployed sleep station 2.00 1.67 3.83 3.17

Sleep station curtains easily stowed by 1 crew 3.00 2.67 3.17 3.50

Overall design of sleep station 3.50 2.33 3.17 4.17

a n¼2 crew members per crew. Means were calculated across days for each crew.

Fig. 14. The left photo shows a Cabin 1A sleep station with sleep curtains stowed. Note on the far left of the photo the other crew member’s sleep station

is still closed. The right photo shows a Cabin 1B sleep station with curtain deployed.

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Four elements of the sleep station were considered bysome crews as borderline. These include ease of seatreconfiguration for sleep station setup, sleep quality,lighting quality within the sleep station, and lightingcontrol within the sleep station. Crew 1A deemed easeof seat reconfiguration as borderline with improvementwarranted, while the other three crews deemed thiselement as acceptable with minor improvements desired.After the DRATS 2009 field test, Cabin 1A’s cockpitreceived the modified seat design which was attached inCabin 1B so that both vehicles had the same seatingdesign. Crew 1A reported the seat needed simpler moreintuitive tabs for seat adjustment more akin to a car seat.This was also noted by all the crews as an issue. Theadjusting mechanism was difficult to understand and wasa two-handed operation when trying to adjust the seat orfold it down for sleeping. When sitting in the seat, thecontrol levers were hard to reach. Crews reported theadjustment controls were annoying, difficult, counter-intuitive, and sticky. Crew 1A also noted that closing thegaps and securing the cushions when the seat wasreclined needed some improvement as well. Quality ofsleep in the vehicles also receives some mixed reviewsfrom the crews. For Cabin 1A, crews indicated noise wasthe major issue especially with the air conditioner

compressor and communications speakers. Lights fromthe cockpit area were also noted as affecting their sleep.Cabin 1B crews noted the better sound installation of thesleep curtains helped isolate the vehicle noise somewhat.As with Cabin 1A, the air conditioner, Velcro& (from sleepstation curtains and soft lockers), lights, and blower fanswere the major noise makers which kept the crewsawake. The quality and the control of lighting in the sleepstation were considered borderline with improvementwarranted by the B crews. They liked the personal head-lamps once in the deployed station; however, theywanted a way to control the vehicle’s general interiorlights as well from within the station. Both vehicle crewsnoted there were a lot of Light Emitting Diodes (LEDs)blinking around the vehicle at night and wanted a way tocontrol the intensity. The crews also suggested havingeach side of the vehicle on separate controls so the crewmember can control their lights of the port side withoutaffecting the lighting on the starboard side. Simple coverswere also suggested by crews.

Comparing habitability data from the last three fieldtrials, over the course of a 3-, 7-, and 14-day missions, thelinear trend indicates a slightly positive trend in theamount of habitable volume as the mission durationlengthens (y¼�0.1525þ3.8783; Fig. 15). Sleep station

Fig. 15. Overall acceptability of the vehicles habitability volume over three desert field trials.

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curtains, stowage, and trash/waste management are theissues crews cited most as habitation issues needing to beimproved. All field reports over the last 3 years concur withwhich habitability issues should be addressed and most areminor according to the crews. After the 2008 field trial,personal stowage was redesigned for the 2009 and 2010trials as a personal soft locker system. All crews reportednotable improvements in stowage volume; however, the2009 crew indicated the reconfiguration of the cabin forEVAs was too time consuming and the system neededimprovement. Improvement in stowage between the vehi-cles came with bench seat stowage in Cabin 1B which isaccessed from the top instead of the sides. During the 2009and 2010 field trials the crews noted the improvement indesign. Trash and waste management is still an issue withcrews regardless of vehicle or duration. Though procedureshave improved on this issue somewhat designers are stillseeking a better solution for the next generation prototypeof the rover. The improvement of habitability over theduration of a mission could be due to the crew becomingaccustomed to the internal systems for everyday living.

5. Conclusions

Over the past three desert field trials, a copious amountof design data has been collected on all the functionalelements of the GEN 1 cabins from the interior layout ofthe cockpit and habitation aspects to the exterior transla-tion paths and procedures. Physical testing, such as thedesert field trials with vehicle prototypes that are con-tinuously improved, allows for the evaluation and testingof human-in-the-loop (HITL) activities involving dynamictasks, translations, and coordination between crew. HITLtesting is crucial as it provides enhanced feedback datawhich can save time and project cost by catching potential

volumetric and functional issues early in the design cyclewhile validating and refining the Computer Aided Design(CAD) analysis design and management teams with anenhanced ability to make an informed decision on how tomature the vehicle design, reduce design costs, and createan environment of efficiency for crew mission success.

The purpose of this evaluation was to obtain prelimin-ary HITL performance data pertaining to crew perfor-mance, functionality, and human–machine interfaces onthe current Space Exploration Vehicle (SEV) Cabin 1A andCabin 1B configurations over a total of 14 days, dividedinto two 7 day missions, with two vehicles and fourcrews. In addition, a comparison of crew habitability ofthe rovers based on mission duration over the last threedesert trials was conducted. Several real time humanfactors metrics were employed, as well as both objectivesensor data and subjective performance data over the two7-day flight-like missions. The conclusions and recom-mendations in the next paragraph are valid design con-cerns that should be taken into consideration for futurevehicle designs.

All crews reported the volume was barely enough forusing the WCS during sleeping hours without waking theother crew member, and they suggested, that reducingthe size of the bed aft section by approximately 0.03–0.05 m (1–2 in.) would add approximately 0.05–0.1 m(2–4 in.) of seat room. Odor was a factor with the WCS andtrash. Crews reportedly used Febreeze& and air freshenersto combat the odor. They suggested adding a fan ductsystem to vent odor out of the vehicles. Crews in bothvehicles stated the soft lockers tended to slide off the railsand into the aisle when the rover was sufficiently tilted inthe proper direction (locker side high) on slopes 4101.They suggested some type of a locking tab on the railsto prevent the lockers from sliding out. As for stowage

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space within the vehicles’ cockpits, crews noted that somespaces that were not utilized and suggested adding softstowage pockets over the side windows to store smaller,light-weight items, such as snacks or a field notebook. Thecue card, which accompanied both of the exercise devices,aided the crews in stowing the equipment back into theCTB; however, the crews did suggest another cue card forassembling the equipment. Seat deployment was annoy-ing, difficult, counterintuitive, and sticky. The adjustingmechanism was difficult to understand and was a two-handed operation when trying to adjust the seat or fold itdown for sleeping. Crews suggested a simpler, moreintuitive means of seat deployment; tabs for seat adjust-ment more akin to a car seat could improve the situation.Quality of sleep in the vehicles received some mixedreviews from the crews due to noise from the air condi-tioner compressor, communications speakers, and Velcro&.Suggestions included better sound installation for sleepcurtains and employing zippers or draw strings as well toisolate and reduce noise. Crews stated for the 7-daymission duration, one soft locker was adequate to stowtheir personal items. For Cabin 1B, the crews noted that theextra volume of the soft lockers made it perfect to stowothers items; thus, keeping bench and floor stowage accessdown to a minimum. All the crews like the abundant smallcubby holes and said they made organizing one’s geareasier. The crew stated the vehicle habitable volume wouldbe tolerable for a 2 week mission, especially when a crewdevelops a routine for stowing items. However, they alsofelt the length could be an ordeal if getting out on EVA wasnot possible. As for a 30-day mission, crews were less sureabout doing this long mission and thought it would betough given the current vehicle volume.

Having four diverse crews working and living in theSEVs for 7 days enriched the field data for preliminarytrend comparisons and enhanced the understanding ofcurrent vehicle design and locations for design improve-ments for the next generation of rovers. For futureresearch, it would be beneficial to continue using suchanalog environments, such as DRATS, to evaluate thecrew’s performance and interaction with vehicle systemsduring multiple mission durations. The aim of continuinga human-centered design approach and collaboratingwith designers to capture information in their design, isto enhance human performance and comfort while lend-ing confidence to both future lunar habitation design, aswell as planetary vehicle design.

References

[1] A.F.J. Abercromby, M.L. Gernhardt, H.L. Litaker Jr., Desert research

and technology studies (DRATS) 2008: Evaluation of small pressurize

rover and unpressurized rover prototype vehicles in a lunar analog

environment, NASA/TP-2010-216136, NASA/Johnson Space Center,

Houston, TX, 2010.[2] H.L. Litaker, Jr., S Thompson., R. Howard, Jr., 2009. A comparison of

unpressurized rover and small pressurized rover during a desert

filed evaluation, in: Proceedings of the Human Factors and Ergo-

nomics Society 53rd Annual Meeting, 2009, pp. 1442–1446.[3] A.F.J. Abercromby, M.L. Gernhardt, H.L. Litaker, Jr. Desert research

and technology studies (DRATS) 2009: a 14-day evaluation of the

space exploration vehicle prototype in a lunar analog environment,

NASA/TP-2012-21736, NASA/Johnson Space Center, Houston, TX,2012.

[4] H.L. Litaker, Jr., S. Thompson, R. Howard, Jr., 2010. Human habitationin a lunar electric rover during a 14-day field trial, in: Proceeding ofthe Human Factors and Ergonomics Society 54th Annual Meeting,September 27–October 1, 2010, San Francisco, CA.

[5] JSC, Net habitable volume verification method. NASA, JSC, 2008.[6] J. Wise, The Quantitative Modeling of Human Spatial Habitability,

NASA Contractor Report 177501, NASA/Ames Research Center,Moffett Field, CA, 1988.

[7] NASA, Human-Rating Requirements and Guidelines for Space FlightSystems, NPG 8705.2, Office of Safety and Mission Assurance, 19June 2003.

Harry L. Litaker, Jr. is a Senior Human FactorsDesign Engineer for Lockheed Martin workingwith the Habitability and Human FactorsBranch of the Space Life Sciences Directorateat Johnson Space Center in Houston, Texas.He received his undergraduate degree inCommunications at Western Carolina Univer-sity and his graduate degree in HumanFactors Engineering and Safety Engineeringfrom Embry-Riddle Aeronautical University.Mr. Litaker has worked for the US militaryconducting human factors evaluations on pro-

totype vehicles. Currently, his responsibilities

are supporting several of NASA’s Exploration Analog Field Tests studyinghuman performance within the Space Exploration Vehicle and the HabitatDemonstration Unit.

Shelby Thompson is a Human FactorsDesign Engineer with Lockheed Martin atNASA Johnson Space Center in the UsabilityTesting and Analysis Facility (UTAF). He hasworked on various projects for the Constella-tion and Altair Programs. The focus of thework has included developing a cursorcontrol device for the Orion CEV, designingdisplay layouts for the Surface ExplorationVehicle, and numerous habitation studies oflunar vehicles and habitats. He received hisPh.D. in Human Factors Psychology from

Wichita State University in 2007.

Rich Szabo is contractor lead for NASA’sHabitability Design Center (HDC). He is cer-tified through the Board of Certification inProfessional Ergonomics (BCPE) and bringsover 10 years of experience as an ergonomistand human factors design engineer. Mostrecently, Rich has supported a number ofhigh visibility efforts including mockupdesign and habitability evaluations of Orion,Altair, Habitat Demonstration Unit (HDU),and the Space Exploration Vehicle(SEV)—and also supporting NASA’s effort to

develop a functional net habitable volume

(NHV) requirement. Rich received his MS in Industrial Engineering fromthe University of Wisconsin-Madison in 1998 and his BS in IndustrialEngineering from the University of Pittsburgh in 1996.

Evan Twyford is an accomplished aerospacedesigner in Johnson Space Center’s Habit-ability Design Center. He received his BFAin Industrial Design from the Rhode IslandSchool of Design in 2005, and currently alsoteaches industrial design courses at the Uni-versity of Houston’s Gerald D. Hines Collegeof Architecture.

H.L. Litaker Jr. et al. / Acta Astron390

Carl Conlee is a Senior Architect in theHabitability Design Center, which resides inthe Space and Life Sciences Directorate atJohnson Space Center. His role within theHDC is to develop future space vehicle andhabitat concepts, from the initial conceptdevelopment phase, through the design andfabrication of high fidelity, functional proto-types. He holds a Bachelor of Fine Artsdegree in Industrial Design from the RhodeIsland School of Design, where he graduatedin 2005. Carl has been teaching undergradu-

ate courses at the Gerald D. Hines School ofArchitecture, at the University of Houston,since 2008.

Robert Howard is the manager of NASA’s

Habitability Design Center within the Spaceand Life Sciences Directorate at Johnson SpaceCenter. He leads a team of architects, industrialdesigners, engineers, and usability experts todevelop and evaluate concepts for spacecraftcabin and cockpit configurations. His job is toensure that future spacecraft adequately sup-port the tasks and functions required for thecrew to safely and efficiently conduct theirmission. He holds bachelor degrees in GeneralScience and Aerospace Engineering, an M.S. in

autica 90 (2013) 378–390

Industrial Engineering, a Ph.D. in AerospaceEngineering, and is pursuing a certificate inHuman Systems Integration.