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Acta Astronautica

Acta Astronautica 106 (2015) 47–62

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Model of medical supply and astronaut healthfor long-duration human space flight

Albert Assad a,n, Olivier L. de Weck b

a Department of Aeronautics and Astronautics and Engineering Systems Division, 33-410, Massachusetts Institute of Technology,77 Massachusetts Avenue, Cambridge, MA 02139-430, USAb Department of Aeronautics and Astronautics and Engineering Systems Division, 33-410, Massachusetts Institute of Technology,77 Massachusetts Avenue, Cambridge, MA 02139-430, USA

a r t i c l e i n f o

Article history:Received 10 November 2013Received in revised form25 August 2014Accepted 5 October 2014Available online 12 October 2014

Keywords:Astronaut healthLong-duration space flightMedical supply demand modelSupply chain management

x.doi.org/10.1016/j.actaastro.2014.10.00965/& 2014 IAA. Published by Elsevier Ltd. A

esponding author.ail addresses: albert1619@gmail.com (A. Assa@mit.edu (O.L. de Weck).

a b s t r a c t

Planning a safe and productive human space exploration mission involves a dual approachaddressing both the health of the vehicle and the crew. The goal of this study was todevelop a quantitative model of astronaut health during long-duration space flight and amedical supply demand model in support of such missions. The model provides twooutputs, Alphah and Mass of Medical Consumables (MMC), for each set of inputparameters. Alphah is an estimate of total crew health and is displayed as a percentage.MMC is a measure of medical consumables expended during the mission and is displayedin units of kilograms. We have demonstrated that Alphah is a function of three scalingparameters, the type of mission, duration of mission, and gender mix of the crew. The typeof mission and gender of crew are linked to radiation fatality data published by NASA.Mission duration is incorporated into the model with predicted incidence of illness andinjury data published on US Navy submarine crews. MMC increases non-linearly with thenumber of crew, the duration of the mission and the distance of the mission away fromEarth. This article describes the relationships between these parameters and discussesimplications for future crewed space missions.

& 2014 IAA. Published by Elsevier Ltd. All rights reserved.

1. Introduction

1.1. Importance of crew health and medical supply in spaceexploration

Planning a safe and productive human space explora-tion mission involves a dual approach addressing both thevehicle and crew health. Although the engineering aspectsof delivering a vehicle to a predetermined destination inspace, propulsion, navigation, and communications, have

ll rights reserved.

d),

been demonstrated, adding humans on these missionsadds complexity and uncertainty. The medical care andwell-being of space crews is the primary limiting factor inthe achievement of long-duration space missions [1].

The space environment produces profound changes inthe physiology of humans. Medical contingencies willoccur and astronauts must be prepared to treat accidentsand illnesses while they are millions of miles awayfrom Earth. In 1997, teams from NASA and the NationalSpace Biomedical Research Institute (NSBRI) reviewed theexperiences of the two-hundred and seventy-nine menand women who had participated in space missionsbetween 1988 and 1995. They discovered that all but threeof them suffered some sort of illness during the trip [2]. Anad hoc committee of the Space Medical Association and

Nomenclature

Kmd scaling parameter mission durationKac scaling parameter age of crewKcs scaling parameter crew size

Kde scaling parameter distance from EarthKme scaling parameter medical expertiseMMC mass of medical consumables [kg]Alphah crew health and availability factor

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–6248

the Society of NASA Flight Surgeons reported that morbid-ity and mortality related to illness and injury haveaccounted for more failures and delays in the executionof missions than have defective transportation systems [3].

Although there are many unknowns, there are threeareas of special concern; 1. the effects of being exposed tolarge amounts of space radiation, 2. bone and muscle loss,and 3. the psychological aspects of confinement andisolation. In animal model experiments where rodentswere exposed to high energy particles similar to whatastronauts would be exposed to on a long durationinterplanetary space mission there were both behavioralchanges and the rodent's brains appeared to have micro-scopic lesions as if they had been hit with gunfire [2]. Thegeneral estimate of risk of bone fracture on a three-yearmission is estimated to be 20–30% and does not specifi-cally take into account fractures during surface extravehi-cular activity (EVA) [2]. On such isolated and long-durationmissions, there may be difficult choices for the crew tomake. Given the finite amounts of resources a commandermay have to decide when to offer continued support andwhen to limit support [2]. Although NASA does not have apolicy regarding a cessation of support the agency doesdiscuss this possibility if continued treatment causesundue risk or peril to the remaining crew [4].

Crew health will require operational planning andappropriate medical supply chain management. The devel-opment and execution of long duration human space flightmissions will stretch the capabilities of NASA operationalplanners [5]. Although there are a vast number of scientificprinciples and techniques that have been developed toimprove the effectiveness and efficiency of supply chainmanagement on Earth, the potential benefits of this bodyof knowledge are currently only poorly understood in thecontext of space exploration. Previous space explorationhas relied on a combination of carry-along and scheduledresupply. Unlike Gemini, Mercury, Apollo, and Shuttle eraexploration programs, future long-duration and long-distance exploration class missions will need to rely on acomplex supply network on the ground and in space. Thissupply chain management may even incorporate preposi-tioning and utilization of locally available resources.

The goal of this research was to develop a quantitativemodel of long duration human spaceflight astronauthealth and medical supply demand requirements takinginto account past experience.

1.2. Human experience and medical events in space

The human experience in space is the work and achieve-ment of many nations. The United States, Russia, and Chinahave flown humans in space and returned them to Earth. The

work of state sponsored programs is also increasingly beingaugmented with private organizations. Scaled Composites, acompany located in Mojave, California was the first privatecorporation to design, build, and fly humans into space andreturn them safely to Earth. Other companies are in theplanning stages for developing similar capabilities.

Human spaceflight is defined as spaceflight with a humancrew and possibly passengers. The first human spaceflightoccurred on April 12, 1961, when the former Soviet Unionlaunched cosmonaut Yuri Gagarin aboard the Vostok 1spacecraft and made one orbit around the Earth. AlexeiLeonov made the first spacewalk on March 18, 1965. TheUnited States became the second nation to achieve mannedspaceflight with the suborbital flight of astronaut AlanShepard aboard Freedom 7, as part of Project Mercury. Thefirst U.S. orbital flight was that of John Glenn aboard Friend-ship 7, which was launched February 20, 1962. The People'sRepublic of China became the third nation to achieve humanspaceflight when astronaut Yang Liwei launched into spaceon a Chinese-made vehicle, the Shenzhou 5, on October 15,2003. Previous European, Japanese, and Iraqi manned pro-grams were abandoned after years of development.

The furthest destination for a human spaceflight to datehas been the Moon (1969–1972). The only crewed missionsto the Moon have been those conducted by the UnitedStates as part of the Apollo program. The first human Moonlanding was Apollo 11, on July 20, 1969 during which NeilArmstrong and Buzz Aldrin became the first humans to setfoot on the Moon. Five additional missions landed in total,numbered Apollo 12, 14, 15, 16, and 17. Twelve men reachedthe Moon's surface and continue to be the only humans tohave been on an extraterrestrial body. The Soviet Uniondiscontinued its program for lunar orbiting and landing ofhuman spaceflight missions on June 24, 1974.

The longest human spaceflight of 437 days is that ofValeriy Polyakov from January 8, 1994 until March 22,1995. Sergei Krikalyov spent the most cumulative totaltime of anyone in space, 803 days, 9 h, and 39 s. As of 2007,citizens from 33 nations (including space tourists) haveflown in space aboard Soviet, American, Russian, andChinese spacecraft [6].

There are sparse published accounts of medical eventsthat have occurred in spaceflight. This may be partiallyattributed to privacy concerns and to astronauts beingreluctant to talk about medical ailments and governmentagencies equally reluctant to publish them. Astronauts areconcerned about speaking about medical ailments for fear oflosing flight status. From the sparse information publishedwe can list a variety of medical events that have occurred inboth the recent US and Russian space programs as listed inFigs. 1 and 2 [7]. The majority of these medical events havebeen minor and well within the medical capability of the

Condition Frequency PercentFacial fullness 226 81.00%Headache 212 76.00%Sinus congestion 173 62.00%Dry skin, irritation, rash 110 39.40%Eye irritation, dryness, redness 64 22.90%Foreign body in eye 56 20.10%Sneezing/coughing 31 11.10%Sensory changes (e.g., tingly, numbness) 26 9.30%URI (common cold, sore throat, hay fever) 24 8.60%Back muscle pain 21 7.50%Leg/foot muscle pain 21 7.50%Cuts 19 6.80%Shoulder/trunk muscle pain 18 6.50%Hand/arm muscle pain 15 5.40%Anxiety/annoyance 10 3.60%Contusions 10 3.60%Ear problems (predominantly earaches) 8 2.90%Neck muscle pain 8 2.90%Stress/tension 8 2.90%Muscle cramp 7 2.50%Abrasions 6 2.20%Fever, chills 6 2.20%Nosebleed 6 2.20%Psoriasis, folliculitis, seborrhea 6 2.20%Low heart rate 5 1.80%Myoclonic jerks (associated with sleep) 5 1.80%General muscle pain, fatigue 4 1.40%Subconjunctival hemorrhage 4 1.40%Allergic reaction 3 1.10%Fungal infection 3 1.10%Hoarseness 3 1.10%Concentrated or "dark" urine 2 0.70%Decreased concentration 2 0.70%Dehydration 2 0.70%Inhalation of foreign body 2 0.70%Subcutaneous skin infection 2 0.70%Chemical in eye (buffer solution) 1 0.40%Mood elevation 1 0.40%Phlebitis 1 0.40%Viral gastrointestinal disease 1 0.40%

Fig. 1. Medical events of the Space Shuttle Program reported by frequency from post flight medical debriefings with crewmembers. 1988–1995 (adaptedfrom Fundamentals of Space Medicine, Clément 2005).

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–62 49

crew medical officers on board and within the level ofmedical capability of the supplies and equipment on boardand the skill levels of the flight surgeons on the groundproviding telemedicine support [8].

1.3. Human experience and medical events in analogenvironments

As an additional guide for predicting both frequency ofmedical events and medical supply needs for the isolatedand extreme environment of space we looked at medicalcare delivery in space analog environments, which includenuclear submarines, Antarctic research stations, and polarexpeditions. These analogs involve small groups living andworking in isolation. These analogs are helpful also tocharacterize and quantify the incidence and prevalence ofinjury and illness. From these environments, extrapolationcan be made and procedural guidelines for lunar andplanetary expeditions can be delineated [9].

1.3.1. AntarcticaMedical events have been extensively documented dur-

ing various studies of personnel in Antarctica. The incidenceof respiratory ailments, infectious disease, mental disordersshow an increased relative risk when compared to controls[10].

Dr. Jerri Nielsen, the sole physician of a 50 memberscientific team at an Antarctic research station, becameseriously ill while serving at the station. Total darknessand extreme cold made landings usually impossible thattime of the year. Medical supplies were airlifted andparachuted down to her so that she could perform herown biopsy and determine if a lump that she felt in herbreast was cancer. Dr. Nielsen successfully performed herown breast lumpectomy [11]. Dr. Leonid Rogozov, whilespending the winter at Novolazarevskaya research stationin Antarctica, on April 30, 1961 had to remove his ownappendix. Since the incident, that station is always staffedwith two doctors.

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–6250

1.3.2. SubmarinesSubmarine and spacecraft environments are analogous.

Both involve isolation, a closed environment with artificialatmosphere, crowded quarters for living and working,limited space for supplies and medical equipment, theoccasional use of non-physician health care providers,use of pre-mission health screenings, and the priorityof mission goals over individual needs [12]. Some potential

Medical Event

Superficial injuryArrhythmia/conduction disorderMusculoskeletalHeadacheSleeplessnessTirednessConjunctivitisContact dermatitisErythema of face, handsStool contents (preflight)Acute respiratory infectionAstheniaSurface burn, handsDry nasal mucousGlossitisHeartburn/gasForeign body in eyeConstipationContusion of eyeballDental cariesDry skinHematomaLaryngitisWax in ear

Fig. 2. In-flight medical events for cosmonauts in the Mir program (adapted fr

NASAPerception

of RiskDisease Category * Survey

Mental Disorders 2Sensory 6Circulatory 9Respiratory 4Gastrointestinal 8Genitourinary 7Skin 1Musculoskeletal 5Injury / poisoning 3

-------------------------------------------------------------

Fig. 3. Comparison of perception of medical risk ranking of

differences appear because of the lack of gravity inthe space environment and the often military nature ofoperations in submarines.

During the submarine missions, potential missionimpacting events were rare. One study detailed 1389officers and 11,952 enlisted crew members that servedaboard participating submarines for 215,086 and 1,955,521person–days at sea, respectively, during their study period.

Initial Events Recurrences(n=169) (n=135)34 230 9829 NR16 810 910 44 24 34 NR4 NR3 NR3 23 NR2 NR2 12 NR2 NR1 NR1 NR1 NR1 11 NR1 51 NR

om Fundamentals of Space Medicine, Clemént, 2005), NR¼ no recurrence.

U.S. NavyU.S. Navy Submarine Polaris

Submarine Enlisted SubmarineOfficers, Crew, Patrols,

1997-2000 1997-2000 1968-1973

9 7 75 5-6 67 91 2 26 5-6 38 8 54 3-4 43 3-42 1 1

---------------------------------------------------------

space flight for astronauts (adapted from Thomas 2003).

11. Medical

Fig. 4. Classes of supply.

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–62 51

Among a crew of seven officers, only one medical eventwould be expected to occur during a 6 month mission andresult in 0.75 days or less of limited or no duty. Among acrew of seven enlisted men, about 2 medical events wouldbe expected during a 6 month mission and result in about1 day of limited or no duty per medical event [12].

Fig. 3 shows NASA's view of mission risk in relation tothe data in the submarine environments [12]. This percep-tion of risk is from the differences in the environment.Respiratory risk and injury perception are consistently highacross environments. 82% of submariners had medicalcomplaints [13]. Most common of these were runny nose,difficulty sleeping, and backache. Despite the availability ofmedical care, self-medication and treatment was common.The authors state that planning for medical care in isolatedenvironments should include consideration of unreportedminor medical problems and self-treatment patterns. Thisunderreporting is a major factor among space crews.

1.4. Telemedicine and presence of medical expertise

Telemedicine is a tool for medical practice wherebytelecommunication is used to support health care deliveryto distant sites. Monitoring and telemedicine support hasproven beneficial in remote environments and has alsoproven its value in space medicine. The delivery of medicalcare in space at distances of potentially millions of mileswill require these tools and principles [14].

The application of telemedicine to space exploration wasdriven by necessity. This has often been the only way forspace crews to obtain medical care in space [6]. Time todefinitive treatment may vary from hours in orbital spaceflight, days for a remote exploratory camp, weeks for polarbases and months to years for interplanetary exploration.Communication with terrestrial support personnel duringinterplanetary flight is much more difficult than in orbitalflight. These communication challenges will necessitate thedevelopment of expert systems to increase independence.

The presence of local or remote medical expertise mayreduce the requirements to carry supplies and reduce thefrequency of resupply. NASA put together a blue print forspace medicine providers. The agency has looked at theskills and training requirements for medical officersonboard exploratory class space vehicles, with the longestexploration missions requiring the presence of a surgeon.The skills and training of the CMO (crew medical officer)will require breadth and depth, producing a highly quali-fied physician for space medical care delivery [15]. An on-board medical crew member will be essential for explora-tion class missions and two may be necessary in case onemedical officer is infirmed or incapacitated [16–18].

1.5. Available medical capability and facilities in space

As distance from Earth increases there is a need forincreased independence and increased capabilities andautonomy [19]. Since the time required to return an ill orinjured crew member to Earth to obtain definitive medicalcare is prohibitive, future exploration-class missions to themoon or Mars will require sophisticated and complete on-board medical care capabilities and facilities.

At the height of budgeting and planning, a fully equippedHealth Maintenance Facility (HMF) was planned for theInternational Space Station [20]. The facility was sophisti-cated and complete with x-ray equipment and enoughsupplies to perform surgery and address trauma [21]. Dueto space station freedom cost overruns, the plans for thisfacility were canceled. Plans for on-board medical equipmentand resources are currently in flux with changing nationaland international goals. However, some capability is neededto accomplish any planned exploration mission with success.

1.6. Logistics

Supply chain management as applied to terrestrial appli-cations is a set of approaches utilized to efficiently integratesuppliers, manufacturers, warehouses, and stores, so thatmerchandise is produced and distributed at the rightquantities, to the right locations, and at the right time, inorder to minimize systemwide costs while satisfying servicelevel requirements [22]. Optimization of supply chains andlogistics architectures have been the focus of global industryto increase efficiency and reduce operating costs. There are avast number of scientific principles and techniques that havebeen developed since to improve the effectiveness andefficiency of supply chain management (SCM) on Earth,however, the potential benefits of this body of knowledgeare currently not well understood in the context of spaceexploration.

Logistics and supply chain management is a key pieceof the exploration picture for NASA [23]. Sustainable long-duration space exploration is impossible without appro-priate supply chain management. Unlike Gemini, Mercury,Apollo, and Shuttle era exploration programs, futureexploration will have to rely on a complex supply networkon the ground and in space. This method of supply can bedone in three ways: 1. pre-deployment, 2. carry-along withthe crew, and 3. scheduled or on-demand resupply.

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–6252

Lessons can be learned from terrestrial supply logisticsand analog environment logistics such as submarines andsupplying remote and austere environments such as Ant-arctica. Submarines pose interesting logistics issues. Sub-marines are supplied when they are in port and can inextreme situations surface and be supplied by surfacevessels or initiate a medical evacuation. This resurfacing,although analogous to an abort to Earth, would not bepossible in a distant space mission. Antarctic environmentsalso teach lessons to logistics planners. There are limits towhat can be delivered and when because of operationalcapabilities and seasonal accessibility time windows.

Up until now, with the farthest mission being the Moonand the longest duration stay being on Mir, medical supplylogistics has been limited to what a crew carried with themand what has been pre-supplied to the shuttle or spacestation. In low Earth orbit there is a capability to intermit-tently replenish stores and consumables with supply shipsat a rate of about once per month currently on ISS.

ICD-9 Cod

001-139: Infectious and parasitic diseases

140-239: Neoplasms

240-279: Endocrine, nutritional and metabo

280-289: Diseases of the blood and blood-f

290-319: Mental disorders

320-359: Diseases of the nervous system

360-389: Diseases of the sense organs

390-459: Diseases of the circulatory system

460-519: Diseases of the respiratory system

520-579: Diseases of the digestive system

580-629: Diseases of the genitourinary syst

630-679: Complications of pregnancy, child

680-709: Diseases of the skin and subcutan

710-739: Diseases of the musculoskeletal s

740-759: Congenital anomalies

760-779: Certain conditions originating in th

780-799: Symptoms, signs, and ill-defined c

800-999: Injury and poisoning

Fig. 5. International Classifi

1.7. SpaceNet modeling framework

The SpaceNet software is a simulation and optimizationtool that captures the concepts and ideas related to inter-planetary supply chain management and logistics architec-tures. SpaceNet is useful to logisticians and missionarchitects. The software models interplanetary space logis-tics as a network, allowing the user to input scenarios,simulate them, and generate measures of effectiveness.Optimization can be used to find the best logistics networkfor a given set of surface missions, and trade studies can becarried out to evaluate various types of logistics architec-tures for comparison.

SpaceNet unitizes building blocks of Nodes, Supplies,Elements, and Network, Orbit Dynamics, processes (i.e. wait-ing, transporting, or transferring) and discrete event simula-tion at the individual mission level (i.e. sortie, resupply) andat the campaign level (i.e. for a set of missions). It providesvisualization of the flow of elements and supply items

es

lic diseases, and immunity disorders

orming organs

em

birth, and the puerperium

eous tissue

ystem and connective tissue

e perinatal period

onditions

cation of Diseases (ICD).

Rates of Medical

Events/100 Person-years

Category (ICD-9) Codes (likelihood)

Infectious/Parasitic Diseases (001-139) 0.0048Neoplasms (200-299) 0.0012Endocrine (240-279) 0.0004Blood (280-289) 0.0002Non-Psychotic Mental Disorders (300-316) 0.0091Nervous System/Sense Organ Disorders (320-389) 0.7813Circulatory System Disorders (390-459) 0.7813Respiratory System Disorders (460-519) 3.9061Digestive System Disorders (520-579) 1.9530Genitourinary System Disorders (580-629) 0.3906Skin & Subcutaneous Tissue Disorders (680-709) 8.2031Musculoskeletal System Disorders (710-739) 0.0076Signs, Symptoms, and Ill-Defined Conditions (780-799) 0.3906Injury (800-999, E800-E899) 11.3280

TOTAL EVENT RATE 27.7573

Fig. 7. Proposed combined Rates of Medical Events (Adapted fromBillica 1996).

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–62 53

through the interplanetary supply chain and functions as atool to evaluate manually generated exploration scenarioswith respect to measures of effectiveness and feasibility. Themodel described in this paper will be integrated with thealready existing comprehensive space SCM framework,SpaceNet. Future work will incorporate this additional classof supply into SpaceNet. SpaceNet current classes of supply aswell as the addition of medical supply are listed graphically inFig. 4.

The goals and deliverables of this study are consistentwith the new mandate of NASA's Exploration MissionSystems Directorate (EMSD) which is to develop a capabilityand supporting research to enable sustained and affordablehuman space exploration and to ensure the health andsafety of crew during long-duration space flight.

2. Materials and methods

2.1. Classification of disease

An organ system approach was chosen to classify andcategorize medical disorders. This classification facilitatedthe link from all the published sources of medical events andrisk data in the creation of the model. The published eventdata includes US Navy submarine, US Navy pilot, Antarcticwinter-over, US astronauts, and Soviet in-flight data.

The International Classification of Diseases and RelatedHealth Problems (most commonly known by the abbrevia-tion ICD) was chosen as the tool to categorize diseasestates and bridge data between published studies. The ICDprovides codes to classify diseases and a wide variety ofsigns, symptoms, abnormal findings, complaints, socialcircumstances and external causes of injury or disease.Every health condition is assigned to a unique categoryand given a numeric code (Fig. 5).

The ICD is published by the World Health Organization(WHO). The ICD is used worldwide for morbidity and

< 36 yr ≥ 36 yr Submarine ShipN = 9154 3721 68448 7751

Person-Years 114425 46512.5 261248 27090Disease Category

Infectious and parasitic 0.0024 0.0013 0.0048 0.006Neoplasms 0.0010 0.0016 0.0012 0.001Endocrine, nutritional, metabolic and immunity 0.0002 0.0004 0.0004 0.000Blood / blood forming organs ---- ---- 0.0002 0.000Mental disorders 0.0007 0.0021 0.0072 0.012Nervous system / sense organs 0.0008 0.0016 0.0016 0.002Circulatory system 0.0011 0.0044 0.0024 0.002Respiratory system 0.0028 0.0017 0.0074 0.009Digestive system 0.0085 0.0064 0.0068 0.008Genitourinary system 0.0024 0.0028 0.0023 0.003Skin / subcutaneous tissue 0.0017 0.0005 0.0038 0.006Musculoskeletal system 0.0033 0.0040 0.0061 0.007Symptoms / signs / ill defined 0.0014 0.0018 0.0026 0.003Injury and poisoning 0.0078 0.0035 0.0120 0.018Total event rate 0.0341 0.0321 0.0588 0.081

-----------------------------------------------------------------------------------------------------------------

===============================================================

1967-79 1974-79U.S. Navy Pilots U.S. Navy

Fig. 6. Rates of medical events for US Navy pilots, submariners, sailors, Antarctare per person per Earth year.

mortality statistics, reimbursement systems and automateddecision support in medicine. This system is designed topromote international comparability in the collection, proces-sing, classification, and presentation of these statistics [24].

2.2. Model framework with assumptions and justifications

Two factors were modeled: Alphah, an aggregate esti-mate of crew health and availability, and MMC, a calcula-tion of the mass of medical consumables. To make themodel reliable and convincing, each assumption was basedon data and learnings obtained from peer reviewed and

Antarctic SovietWinter-Over Ground Inflight Inflight

1965-79 1959-87 1965-75 1961-929 327 188 45 926 2001 1418.8 2.57 11.1

4 0.0045 0.0021 0 0 4 0.0010 0.0021 0 0

5 0.0005 0.0007 0 0

3 0.0015 0.0014 0 0 6 0.0050 0 0 0.0901

7 0.0035 0.0007 0.7813 0 4 0.0085 0.0021 0.7813 0.18021 0.0070 0.0078 3.9061 0.09013 0.0120 0.0070 1.9530 0 4 0.0035 0.0049 0.3906 0.18027 0.0035 0.0007 8.2031 0 6 0.0050 0.0042 0 0

3 0.0035 0.0007 0.3906 0.27032 0.0125 0.0120 11.3280 0.54059 0.0715 0.0464 27.7340 1.3514

-----------------------------------------------------------------------------------------------------------

============================================================

U.S Astronauts---------------------------------------

ic personnel, astronauts and cosmonauts (adapted from Billica 1996). Rates

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–6254

published literature. The health and medical supply needsof crews performing missions to remote and austereenvironments were available for US Navy submarine, USNavy pilot, Antarctic winter-over, US astronauts, andSoviet in-flight data. When available, US astronaut in-flight data from NASA was incorporated over analogenvironment data. When only analog data was available(i.e. submarine and Antarctic data), submarine data wasselected over Antarctic data.

Submarine medical data was chosen to model the spaceenvironment since this is more analogous to the crewsperforming in-flight space duties and they are similarlymedically preselected. Both of these working environ-ments involve isolation, a closed environment with artifi-cial atmosphere, crowded quarters for living and working,limited space for supplies and medical equipment, theoccasional use of non-physician health care providers, useof pre-mission health screenings, and the emphasis ofmission goals over individual needs [12]. The submarinedata differs from the space environment in that the spaceenvironment is much more harsh on human physiologywith microgravity, the age and educational status of crews,the ability to communicate outside of the vessel, the size ofthe crew is much smaller, and the role of the medicalproviders. In the space environment medical care isprimarily provided by a ground based NASA flight surgeonthrough teleconference and consultation, while on a sub-marine medical care is dispensed on board the vessel [12].Data on officers was chosen over data on enlisted person-nel since the health profile of astronauts is more similar toNaval officer than Naval enlisted personnel.

To simplify the model, the assumption was made thatthere is no reduction in adverse events going from themicrogravity environment to a lunar gravity of 16% or aMartian gravity of 38% for time spent in those environ-ments during the execution of a mission. This assumptionwas made for a lack of data to base a reduction in adverseevents on the presence of partial gravity. Assuming thisworst case scenario that partial gravity would in no wayameliorate the adverse physiologic effects would in effectincrease our estimates for medical interventions and willin the long run result in a more conservative model.

kmd = 1.39x10 -3 * tt = time in Earth days

Fig. 9. Effect of mission duration on event rate.

2.2.1. Alpha – assumptions and governing equationsCrew health was investigated to determine if there was

a relationship between the duration of the expedition,exposure to space radiation and whether there was anyimpact from the performance of extravehicular activity(EVA) effect. After extensive research, there is no dataavailable at present to assess the health effects of theperformance of extravehicular activity on the crew. There

Absorbed Effectivedose (Gy)* dose (Sv)

Lunar mission (180 days) 0.06 0.17

Mars orbit (600 days) 0.37 1.03Mars exploration (1000 days) 0.42 1.07

-----------------------------------------------------------------------------------------------------------------

Fig. 8. Radiation risks for men and women on mi

did appear to be a positive correlation between theduration of the mission and number of illnesses and injury.This makes sense in that the longer a mission the morelikely an illness or injury would occur. This was modeledfrom published US submarine crew data [12].

Although astronauts participating in spaceflight in lowEarth orbit (LEO) are partly protected by the earth'smagnetic fields and the solid shielding of the planet, thisprotective effect was not available for missions to the moonor to Mars. Galactic cosmic radiation (GCR) and/or solarflare event (SFE) effects would impart a morbidity andmortality effect that has been modeled [25]. In a Marsmission that would last 3 Earth years for the round trip anastronaut could absorb about 1 Sv [25]. Radiation is pre-dicted to lead to carcinogenesis and degenerative diseaseand in a certain portion of the spaceflight population, death[25]. The health effects of radiation can be divided into twoclasses: acute and delayed. Acute effects can include; GI(diarrhea), CNS (headache and irritability), blood formingorgans (decrease in white blood cells and platelets), ordeath and delayed effects include an increased rate ofneoplasms and sensory deficits such as cataracts [26].

In a recent article, the committee of the Space MedicalAssociation and the society of NASA flight surgeons calledspace radiation exposure “the greatest unknown in inter-planetary flight”[3]. Countermeasures such as aluminumshielding would only reduce effective GCR dose by 25%and even with more efficient polyethylene by only about35%. Solar proton events can be protected partially by solarshielding. With a mission to Mars, every cell in anastronaut's body would be hit with a proton or secondaryelectron every few days and by a high-energy heavy ionevery month [27]. Biological countermeasures could alsoinclude radio-protective drugs. No human data exists onspace radiation exposure so published estimates are basedon experimental model systems and biophysical calcula-tions. The model used for cancer mortality is based on

Men (age 40 years) Women (age 40 years)

0.68% (0.20 - 2.4) 0.82% (0.24 - 3.0)

4.0% (1.0 - 13.5) 4.9% (1.4 - 16.2)4.2 % (1.3 - 13.6) 5.1% (1.6 - 16.4)

Fatal risk, % (95% CI)----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------------------------

ssions to the Moon or Mars (Cucinotta 2006).

K factor for Crew Size

0

0.5

1

1.5

1 2 3 4 5 6 7 8 9 10

Number of Crew

K fa

ctor

Fig. 11. Graph of K factor values showing “economy of scale” relationshipto crew size.

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–62 55

studies of survivors from atom bombs. There appears to bea gender related effect on mortality when it comes tospace radiation risk. For each type of mission there is agreater number of modeled fatalities when it comes tofemale crew when compared to male crew [28].

Therefore, Alphah is a function of three scaling vari-ables, 1. duration of mission (injury and illness), 2. the typeof mission whether LEO, lunar, or Martian (fatalities), and3. gender (fatalities)

Fig. 6 lists the rates of medical events of US Navy pilots,US Navy submariners, US Navy sailors, Antarctic personnel,astronauts and cosmonauts [29]. For the model it waspreferable not to have zero entries for any category of ICDcodes. We further adapted the proposed rates of medicalevents by selecting the US inflight data and replacing thezero entries in this set of data with Soviet data whenavailable and the US submarine data when the Soviet datawas unavailable. The combined result is shown in Fig. 7.The entries coded in black were US spaceflight data, codedin green are the Russian spaceflight data, and coded in redthe US submarine data. A rate of 27.76 medical events per100 person-years was calculated based on this data.

Next was to determine a number of days of limited or noduty per medical event, which was obtained from the analogsubmarine data [12]. When submarine crew members cameinto the clinic for evaluation of an illness or injury they werelogged as having a recommendation of 1. Full duty – able toassume all regular duties, 2. Limited duty – able to assumesome but not all of regular duties, 3. No duty – unable toassume all regular duties, or 4. Other – referred for consulta-tion. For officers on submarine missions, 214 medical eventsresulted in 156 days of limited or no duty, which is 0.73 dayslost per event or 26 days per 100 person-years at sea.

Because the space environment is much more severeon human physiology we increased the severity of down-time for each event by a scaling factor for space missions.The scaling factor was incorporated to calibrate the sub-marine infirmed rate to the space infirmed rate. Thisscaling factor for the space environment was chosen tobe 100 based on best available information when com-pared to terrestrial environment [6].

Category (ICD-9) Codes

Infectious/Parasitic Diseases (001-139)Neoplasms (200-299)Non-Psychotic Mental Disorders (300-316)Nervous System/Sense Organ Disorders (320-389)Circulatory System Disorders (390-459)Respiratory System Disorders (460-519)Digestive System Disorders (520-579)Genitourinary System Disorders (580-629)Skin & Subcutaneous Tissue Disorders (680-709)Musculoskeletal System Disorders (710-739)Signs, Symptoms, and Ill-Defined Conditions (780-799)Injury (800-999, E800-E899)

# of

Fig. 10. Rates of medical events showing relationship to age

2.2.1.1. Alpha as a function of type of mission andgender. Space radiation may be less of a factor for LEOmissions but will be a significant factor for long-durationspace missions to the Moon and Mars. Fig. 8 demonstratesthe radiation risks for men and women on missions to theMoon and Mars. A gender difference is apparent in theseNASA generated calculations. These fatality risks wereincorporated as part of the calculation of Alphah.

2.2.2. MMCMMC was defined as a function of mission duration, age

of crew members, crew size, distance from the earth, levelof on-board medical expertise, gender of crew, and risk ofmission. After extensive research, there is no available dataat present to assess the effects of gender on the expendi-ture of medical consumables. The governing equationswere set as follows:

MMC ¼ ðnominal mass for DRMÞ � Kmd � Kac � Kcs

�Kde � Kme ð1Þ

2.2.2.1. Effect of mission duration. The rate of medicalevents was previously shown in Fig. 7. From this figure itcan be determined that the probability of a medical eventis related to the duration of the mission. The equation that

Rates of Medical Events

Age>30 Years

Rate/100 Person-Years

Rate/100 Person-Years

Rate/100 Person-Years

19 3.2 8 2.6 11 3.90 0.0 0 0.0 0 0.00 0.0 0 0.0 0 0.0

15 2.6 6 2.0 9 3.28 1.4 1 0.3 7 2.5

56 9.5 30 9.9 26 9.212 2.0 4 1.3 8 2.85 0.8 1 0.3 4 1.4

18 3.1 12 3.9 6 2.119 3.2 9 3.0 10 3.516 2.7 9 3.0 7 2.533 5.6 15 5.0 18 6.4

# of events

Total Age<30 Years

events # of events

and duration or mission (adapted From Thomas 2003).

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–6256

governs this parameter is:

kmd ¼ 1:39� 10�3 � t ð2Þwhere Kmd¼scaling factor related to mission duration, t istime in Earth days. See Fig. 9.

2.2.2.2. Effect of crew age. To determine the effect of crewage on the mass of medical consumables we turned againto the literature. Available and reliable data published forsubmarine crews and missions is listed in Fig. 10 [12].

The data published in the literature for the rates ofmedical events are divided into incidences in crew that areaged less than 30 and greater than 30. There are somediseases and injuries which are higher in older crewmembers (i.e. cardiac) and some that are higher in youngercrew members (i.e. respiratory disorders). The overalldifference between the groups is not clinically significant.If we include this parameter in the model we will relyexclusively on submarine data and not space data. Giventhese reasons, it was decided to leave this parameter out ofthe equations (or set to 1.0) in this generation of the model.

mass (kg) volume (m3)

Apollo 16 7Shuttle 15 0.2Skylab 45 0.2Space Station 460 1.7Distant Mission (ie Mars) 2000 10.0

Fig. 12. Mass of medical equipment dedicated to various classes of missions(adapted from Larson 1999).

Distance from Earth K Factor

LEO 1.00Lunar 2.00Mars 4.00

Fig. 13. Scaling factor for medical supply based on distance from Earth(adapted/calculated from Larson 1999).

Ground Flig

Flight Surgeon Space S

Physician

Astronaut

Crew Medi

Fig. 14. Adapted from

2.2.2.3. Effect of crew size. For each mission there will be abaseline amount of medical consumables and equipmentthat will be assigned to the mission independent of crewsize. With each increase in crew there will be acorresponding increase in the amount of medicalconsumables and equipment that will be needed tosupport the mission to successful conclusion. It wasmodeled that the principle of economy of scale would beevident and that there would be some flattening of thecurve. See Fig. 11.

Kcs ¼ 1 for a crew size of 4 ð3Þ

2.2.2.4. Effect of distance from Earth. There are publishedreports that describe the mass of supply dedicated tomedical consumables and medical equipment is relatedto independence required during the mission andtelemedicine limitations. The farther away from theEarth, the more mass and volume will be needed.

Fig. 12, adapted from Larson, lists the mass of medicalequipment dedicated to previous missions and lists esti-mate for a future Mars mission. [30] Apollo 16 carried amedical kit with a mass of 7 kg. It contained a handful of

ht Missions

urgeon

Astronaut

Physician

cal Officer

Mars

Moon

ISS

Shuttle

McSwain 2004.

Level of Medical Expertise K

CMO 1.00

Astronaut Physician 0.98

Physician Astronaut 0.97

Space Surgeon 0.95

Flight Surgeon N/A

Fig. 15. Scaling factor for medical supply based on level of expertiseonboard.

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–62 57

drugs, a radiation dosimeter, tiny amplifiers for groundmonitoring of the electrocardiogram, and a few miscella-neous supplies. The Shuttle medical kits are more sophis-ticated and have a mass of 15 kg and a volume of about0.15 m3. Given the availability of a quick return to Earthand the relative short duration of this mission this amountof mass is all that is needed to successfully support suchmissions. Despite being a much earlier mission Skylab hada medical kit with a mass of 45 kg and a volume of0.22 m3. The Space Station has 460 kg and 1.7 m3 of which260 kg and 1.1 m3 were consumable supplies. The authorsestimate that a distant mission (such as Mars) may requirebetween 1000 kg equipment and 500 kg consumableswith a volume 6.5 m3 to 2000 kg with 1000 kg consum-ables and a volume of 10 m3.

Fig. 13 are our estimates for Kde (distance from the earthscaling factor). These were linked to similar masses ofmedical consumables taken in previous missions.

Kde ¼ 1 for LEO ð4Þ

2.2.2.5. Effect of on-board medical expertise. Prevention,mitigation, and reduction of medical events can beaccomplished with the on-board presence of medicalexpertise. An on-board medical crew member will beessential for exploration class missions and two may benecessary in case one medical officer is infirmed orincapacitated.

McSwain published a blueprint for space medicineproviders. This work was the result of multiple workinggroups composed of NASA internal and external reviewersand it recommended the knowledge and skill basesneeded to provide medical care for various classes ofmissions. They recommended that the levels of providersbe categorized in five levels 1. Crew Medical Officer, 2.Flight surgeon, 3 Astronaut–physician, 4 Physician–astro-naut, and 5. Space surgeon [15].

Currently, a NASA trained Crew Medical Officer (CMO)would have medical training of about 45 h. Their terres-trial analog for similar duties has about 300 h of training.The recommendations for training included skills sets ofassessment, ophthalmologic, bag–ventilator–mask (BVM)ventilation and endotracheal intubation, intravenousaccess, intramuscular and oral medication administration,and defibrillation. This crew member would need very

Disease Category Mean SD Rank Mean

Mental disorders 2.41 0.124 2 2.66Sensory 2.22 0.055 6 2.37Circulatory 1.83 0.152 9 3.58Respiratory 2.32 0.078 4 2.45Gastrointestinal 2.11 0.074 8 3.04Genitourinary 2.2 0.17 7 2.85Skin 2.46 0.196 1 1.99Musculoskeletal 2.26 0.128 5 2.41Injury/poisoning 2.34 0.132 3 3.09

Probability Mission E

Fig. 16. Results of flight sur

limited sustainment training and some medical simulatorsustainment training.

A flight surgeon would provide ground-based supportthrough telemedicine. The education would be a medicaldegree and sustainment of this education would be con-tinuing medical education (CME). There would be nomedical simulator training required and some mainte-nance of clinical patient care.

An astronaut–physician is described by the authors asastronauts who were once physicians who have given uptheir clinical practices and proficiency for flight profi-ciency. This describes the current astronauts in the corpswith medical degrees. The authors propose a new type ofastronaut, a physician–astronaut who would keep theirclinical skills proficient, like pilots who are astronauts withtheir pilot training.

Another new category of space based medical provideris described as a Space Surgeon. The knowledge and skillsrequired would be similar to a general surgeon of about 50years ago. This person would also be knowledgeable inbiomedical equipment maintenance and repair and inpsychological counseling.

Fig. 14 describes which level of medical provider wouldbe recommended to support which type of mission, withFlight surgeons being ground based only. The higher levelof medical expertise is recommended for exploration classmissions to the Moon and Mars. The figure is also in linewith current standards of a CMO or an astronaut physicianbeing assigned to shuttle class flights.

From these descriptions and from speaking with currentNASA physicians and the lead author, we developed a scalingfactor related to the on-board medical expertise and this isprovided in Fig. 15. With the current available publisheddata, expertise was estimated to have a small effect on themass of medical consumables. The higher the level ofmedical training less consumables that would potentiallybe needed. From the literature, however, it is clear that thelevel of medical expertise would have an effect on themedical outcome for the individual crew member. [29]

For the nominal case:

Kmp ¼ 1:0 for a CMO ð5Þ

2.2.3. RiskRisk was investigated as an additional independent

driver in the calculations. This parameter, defined as

RISK

SD Rank

0.105 5 6.4110.065 8 5.2610.229 1 6.5510.045 6 5.6840.049 3 6.4140.13 4 6.2700.187 9 4.8950.121 7 5.4470.079 2 7.231

ffect

geon survey (1–5 scale).

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–6258

likelihood of a medical event multiplied by impact tothe mission, is in line with current NASA planningprocesses [31]. With increased risk of medical eventsmore resources will be supplied and dedicated to pre-vent or mitigate that risk. A ranking scale of medicalevent risk during spaceflight was developed at NASA[29].

The results of the Shuttle era NASA flight surgeonsurvey is listed in Fig. 16 with the key being Fig. 17. Thisdetails mean scores, standard deviations, and rankings

Rating Scale for Medical Events; Perception of the Med

Probability:

1 = not likely to ever occur during a mission

2 = somewhat likely to occur at least once at some time ove

3 = likely to occur occasionally

4 = likely to occur on most missions, but not expected on ev

5 = expect to occur on each mission

Effect on health of crewmember:

1 = quick treatment and recovery, minimal health effect (e.g

2 = acute, self-limiting, with crewmember unable to perform

recovery expected during mission (e.g., cold, infectious dise

3 = incomplete recovery during the flight, but complete reco

(e.g., trauma, appendicitis, kidney stone, fracture)

4 = never complete recovery, permanent disability (e.g., hea

5 = death during mission

Effect on mission:

1 = no effect on the mission

2 = some effect on the procedures or time lines, but overall

3 = mission effect, loss of certain mission objectives

4 = severe effect on mission objectives

5 = catastrophic effect, mission aborted

Fig. 17. Rating Scale for Medical Events; Perception of th

for probability, health effect, and mission effect fordisease categories.

Because this survey did not assess all the ICD categories,this figure was expanded and adapted to make the modelmore broadly applicable to known missions. For the ICDcategories not surveyed, ICD codes were filled in with ones(the lowest probability). This adaptation is listed in Fig. 18.

The survey data was based on Shuttle era medicalproblems and is not representative of currently plannedexpedition class missions .Fig. 19 is an example of a risk

ical Risk of Space Flight Survey

r the course of the program, but will probably be rare

ery mission

., bandage, aspirin, decongestants)

certain tasks or carry-on normal activity, but full

ase process, ear block, sprained ankle)

very possible after return to Earth and care provided

ring loss, loss of limb)

mission objectives not adversely affected

e Medical Risk of Space Flight Survey (Billica 1996).

5

4

3

2

1

1 2 3 4 5

RISK MATRIX

CONSEQUENCES

LIKELIHOOD

Fig. 19. Risk Matrix Plot (For interpretation of the references to color inthis figure legend, the reader is referred to the web version of this article.)

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–62 59

matrix plot. It plots consequences of medical eventsoccurring against the likelihood of occurrence. The green,yellow, and red portions of the graph are indicative of thelevel of risk. When the results of the NASA flight surgeonsurvey are plotted, they all fall into the green zone so theyare not a large risk. It should be noted that these data areonly based on Shuttle era missions (2 weeks or shorter inlow Earth orbit that would allow a quick return to theEarth in the event of a medical or other contingency).

With an expedition class mission additional unknowns(i.e. solar and galactic radiation exposure) may shift ICDcodes to the yellow or red regions of the risk matrix. EVAactivity may also shift the risk into the red portions of thematrix.

NASA uses these matrices as a tool to make decisionsand to dedicate resources once decisions are made.Resources would fall into two categories; Preventive Control(p): A control, that if successful, will prevent the riskinitiator from impacting the mission and reduce the like-lihood of risk, and Mitigative Control (m): A control, that ifsuccessful, will reduce the consequences of the risk (bysome fraction, μ) or transfer the consequences to a differentdimension.

Although the proposed model equations do not cur-rently incorporate this parameter, implementation in sub-sequent versions of the model would allow for a moregranular description of medical supply mass (laboratoryand diagnostic, imaging, medications, surgical supplies,telemedicine and expert systems equipment) needed tosupport human operations in space. Fig. 20 describes aproposed breakdown of the types of medical supplies anddifferent amounts of supplies could be dedicated to themission based on risk of medical events to the mission.

Prevention and Mitigation (and treatment) will requireonboard Laboratory and Diagnostic, Imaging, Medications,Surgical Supplies, and Telemedicine supplies. Fig. 20 dia-grams a proposed breakdown of mass dedicated to thetreatment of each ICD code. Those marked in red in thefigure are zeroed out because these are not expected tooccur during a mission (i.e. pregnancy), even during a

Disease Category Mean SD Rank Mean

Infectious and Parasitic D 1.00 N/A N/A 1.00Neoplasms 1.00 N/A N/A 1.00Endocrine, nutritional and 1.00 N/A N/A 1.00Diseases of the blood 1.00 N/A N/A 1.00Mental disorders 2.41 0.124 2 2.66Nervous System 1.00 N/A N/A 1.00Sensory 2.22 0.055 6 2.37Circulatory 1.83 0.152 9 3.58Respiratory 2.32 0.078 4 2.45Gastrointestinal 2.11 0.074 8 3.04Genitourinary 2.20 0.17 7 2.85Complications of Pregnan 1.00 N/A N/A 1.00Skin 2.46 0.196 1 1.99Musculoskeletal 2.26 0.128 5 2.41Congential Anamalies 1.00 N/A N/A 1.00Symptoms, Signs, and Ill 1.00 N/A N/A 1.00Injury/poisoning 2.34 0.132 3 3.09

Probability Mission E

Fig. 18. Adaptation of NASA

mission that is 3 years long.One possibility for the incorporation of this figure into

the model is to multiply risk by the individual masses of theclasses of medical supplies for each ICD code. For example:

risk¼ probability of a medical event � impact to the mission ð6Þ

uncorrected mass¼ f ðf unction of riskÞ � Σmasses

ðK � supply categoryÞ ð7Þ

mass of ðICDÞ ¼ RiskðICDÞ � ΣmassesðK � supply categoryÞ ð8Þ

Adding all the component masses would also provideanother way of calculating overall mass. Another perspec-tive can be taken in terms of risk to the individual and notrisk to the mission. This could also be applied to thededication of the MMC that is needed to support a humancrew. Fig. 21 incorporated health effects on the individualcrew members.

RISK

SD Rank

N/A N/A 1.000N/A N/A 1.000N/A N/A 1.000N/A N/A 1.000

0.105 5 6.411N/A N/A 1.000

0.065 8 5.2610.229 1 6.5510.045 6 5.6840.049 3 6.4140.13 4 6.270N/A N/A 1.000

0.187 9 4.8950.121 7 5.447N/A N/A 1.000N/A N/A 1.000

0.079 2 7.231

ffect

Flight surgeon survey.

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–6260

3. Calculation and results

3.1. Case study model applied to Design ReferenceMissions (DRM)

ScenarioDuration: 180 daysMission: LunarCrew: 5Crew Ages: 25 M, 28 F, 35 M, 40 F, 45 MMedical Expertise on board: Crew Medical OfficerUsing the proposed model and applying to the follow-ing scenario we have:

Sample Calculation

Injury and illness (mission duration effect)(space scaling factor) � days /medical events � events/person-years � years �number of crew¼days

100 � (156/214) � (27.76/100) � (180/365) � (5)¼49.8449.84 days out of a possible 900 person-day mission (5 persons �180 days) indicates an astronaut availability decrease to 94.46%due to illness or injury

Fatalities (type of mission effect and gender effect)For a Lunar Mission of 180 days fatal risk for a male is 0.86% and fora female 0.82%

Taking an average for (3 males � (0.68)þ2 females (0.82))/5¼0.74%

Alpha¼94.46�0.74¼%Alpha¼93.72 %

Mass calculationKmd¼1.39 � 10�3 � (180 days)Kcs¼1.1Kde¼2.0Kme¼1.0MC¼nominal mass for DRM� Kde � Kme � Kcs � Kmd

MMC¼500 kg � 2.0 � 1.0 � 1.1 � (1.39 � 10�3 � 180)MMC¼275.2 kg

ICD Code001-139: Infectious and parasitic diseases 140-239: Neoplasms 240-279: Endocrine, nutritional and metabolic diseases, and immunity disorders 280-289: Diseases of the blood and blood-forming organs 290-319: Mental disorders 320-359: Diseases of the nervous system 360-389: Diseases of the sense organs 390-459: Diseases of the circulatory system 460-519: Diseases of the respiratory system 520-579: Diseases of the digestive system 580-629: Diseases of the genitourinary system 630-676: Complications of pregnancy, childbirth, and the puerperium 680-709: Diseases of the skin and subcutaneous tissue 710-739: Diseases of the musculoskeletal system and connective tissue 740-759: Congenital anomalies 760-779: Certain conditions originating in the perinatal period 780-799: Symptoms, signs, and ill-defined conditions 800-999: Injury and poisoning

Nominal Supply weight (Kg)

Fig. 20. Classes of medical supply by ICD code. (For interpretation of the referenthis article.)

4. Conclusions

The goal of this study was to develop a quantitativemodel of long-duration human space flight, astronauthealth, and a medical supply demand model in supportof such missions. The model provides two outputs, Alphahand MMC, for each set of input variables. Alphah is anaggregated estimate of crew health and is displayed as apercentage between 0 and 100% including crew availabilitylost to temporary illness and fatalities. Mass is a measureof medical consumables expended during the mission andis displayed in kilograms.

We have demonstrated that Alphah is a function ofthree scaling parameters: the type of mission, duration ofmission, and gender of crew. The type of mission andgender are linked to radiation fatality data publishedby NASA and mission duration correlates to predictedincidence of illness and injury and is linked to the modelthrough published US Navy submarine crew medicaldata.

The MMC expended increases with the number of crew,the duration of the mission, and the distance of themission away from the earth. The degree of medicalexpertise on-board is not necessarily related to a changein consumption of medical supplies but perhaps to a betteroutcome for the individual infirmed crew member. Wehave determined that there is no information to incorpo-rate gender into this aspect of the model and that the agesof the crew members would also have a negligible effect.

Risk was investigated as an additional independentdriver in the calculations. This parameter, defined as like-lihood of a medical event multiplied by impact to themission, is in-line with current NASA planning processes.Although the equations do not currently incorporate thisparameter, implementation in subsequent versions of themodel would allow for a more granular description of

Labo

rator

y and

Diag

nosti

csIm

aging

Med

icatio

n

Surg

ical S

uppli

esTe

lemed

icine

Risk0.0667 0.0667 0.0667 0.0667 0.0667 1.0000.0667 0.0667 0.0667 0.0667 0.0667 1.0000.0667 0.0667 0.0667 0.0667 0.0667 1.0000.0667 0.0667 0.0667 0.0667 0.0667 1.0000.0667 0.0667 0.0667 0.0667 0.0667 6.4110.0667 0.0667 0.0667 0.0667 0.0667 1.0000.0667 0.0667 0.0667 0.0667 0.0667 5.2610.0667 0.0667 0.0667 0.0667 0.0667 6.5510.0667 0.0667 0.0667 0.0667 0.0667 5.6840.0667 0.0667 0.0667 0.0667 0.0667 6.4140.0667 0.0667 0.0667 0.0667 0.0667 6.2700.0000 0.0000 0.0000 0.0000 0.0000 1.0000.0667 0.0667 0.0667 0.0667 0.0667 4.8950.0667 0.0667 0.0667 0.0667 0.0667 5.4470.0000 0.0000 0.0000 0.0000 0.0000 1.0000.0000 0.0000 0.0000 0.0000 0.0000 1.0000.0667 0.0667 0.0667 0.0667 0.0667 1.0000.0667 0.0667 0.0667 0.0667 0.0667 7.231

Total (Kg)50 100 150 150 50 500

ces to color in this figure legend, the reader is referred to the web version of

RISK

Disease Category Mean SD Rank Mean SD Rank Mean SD Rank

Infectious and Parasitic 1.00 N/A N/A N/A N/A N/A 1.00 N/A N/A 1.000Neoplasms 1.00 N/A N/A N/A N/A N/A 1.00 N/A N/A 1.000Endocrine, nutritional a 1.00 N/A N/A N/A N/A N/A 1.00 N/A N/A 1.000Diseases of the blood 1.00 N/A N/A N/A N/A N/A 1.00 N/A N/A 1.000Mental disorders 2.41 0.124 2 2.47 0.35 5 2.66 0.105 5 6.411Nervous System 1.00 N/A N/A N/A N/A N/A 1.00 N/A N/A 1.000Sensory 2.22 0.055 6 2.41 0.34 7 2.37 0.065 8 5.261Circulatory 1.83 0.152 9 3.12 0.982 1 3.58 0.229 1 6.551Respiratory 2.32 0.078 4 2.17 0.174 9 2.45 0.045 6 5.684Gastrointestinal 2.11 0.074 8 2.69 0.341 3 3.04 0.049 3 6.414Genitourinary 2.20 0.17 7 2.45 0.5 6 2.85 0.13 4 6.270Complications of Pregn 1.00 N/A N/A N/A N/A N/A 1.00 N/A N/A 1.000Skin 2.46 0.196 1 2.23 0.728 8 1.99 0.187 9 4.895Musculoskeletal 2.26 0.128 5 2.74 0.527 2 2.41 0.121 7 5.447Congential Anamalies 1.00 N/A N/A N/A N/A N/A 1.00 N/A N/A 1.000Symptoms, Signs, and 1.00 N/A N/A N/A N/A N/A 1.00 N/A N/A 1.000Injury/poisoning 2.34 0.132 3 2.56 0.368 4 3.09 0.079 2 7.231

Probability Health Effect Mission Effect

Fig. 21. NASA survey data with health effects included.

A. Assad, O.L. de Weck / Acta Astronautica 106 (2015) 47–62 61

medical supply mass (i.e. laboratory and diagnostic, ima-ging, medications, and surgical supplies, as well as tele-medicine and expert systems equipment) needed tosupport long-duration human operations in space. Withadditional data, medical expertise on board will probablyincrease the quantity of material needed but decrease therisk of the missions and increase amount of productivework time astronauts are healthy and are able to workeffectively. This aspect of the model could potentially beincorporated into NASA's Integrated Medical Model (IMM)to quantify the risks to crew health and probability ofmission success.

Acknowledgments

The authors would gratefully like to acknowledge NASAand the Exploration Systems Mission Directorate for fund-ing this research, (Grant number NNX06AH24H). Wewould like to thank Michael Barratt, MD, Conrad Wall, III,PhD, Bishoy, Pat Hale and Ed Crawley, PhD.

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