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Question Bank: Space Medicine Self-Assessment

Also: quiz · self-assessment · multiple choice questions

RadiationIsolation & ConfinementDistance from EarthGravity FieldsHostile/Closed EnvironmentCardiovascularVestibular & SensorimotorMusculoskeletalNeuro-ophthalmicRenal & GUBehavioral Health & SleepClinicianStudentPublic

draft AI-assisted Last reviewed: Pending review · Reviewer: Pending review

Bottom line
  • 30 questions, grouped by hazard and body system. Open each answer to see the explanation and its source.
  • Every answer cites a NASA document or peer-reviewed article and links to the SMF page that covers it.
  • For self-study only. No continuing education credit is offered or implied.

How to use the question bank

Pick an answer in your head, then open Show answer. Each explanation gives the source and a link to the page where the topic is covered. There is no scoring and nothing is recorded.

Educational only

These questions are for self-study. They are not a certification exam, are not reviewed for continuing medical education (CME), and award no credit.

Questions · 30 · Gravity · Kidneys · Radiation · Isolation · Distance · Environment · Commercial spaceflight

Q1 · Gravity · cardiovascular

Within about 2 days of weightlessness, by roughly how much does circulating plasma volume fall?

  1. About 5%
  2. About 15%
  3. About 35%
  4. About 50%
Show answer

Answer: B. About 15%

NASA's orthostatic intolerance brief describes a reduction in intravascular fluid volume of around 15% as the body adapts to the headward fluid shift [1].

Learn more: Orthostatic intolerance (clinical) · References

Q2 · Gravity · cardiovascular

In 10-minute head-up tilt tests on landing day, how did long-duration ISS astronauts compare with Space Shuttle astronauts?

  1. ISS astronauts completed the test more often
  2. Completion rates were the same
  3. Fewer ISS astronauts completed it (2 of 6 vs 52 of 65)
  4. No ISS astronaut was tested
Show answer

Answer: C. Fewer ISS astronauts completed it (2 of 6 vs 52 of 65)

Only 2 of 6 ISS astronauts completed the landing-day tilt test, compared with 52 of 65 Shuttle astronauts. Recovery was also slower after ISS missions [2].

Learn more: Orthostatic intolerance (clinical) · References

Q3 · Gravity · cardiovascular

A crewmember who landed a few hours ago feels faint on standing. What is the best first step?

  1. Start oral midodrine
  2. Lie the patient down, then check orthostatic vitals and give fluids
  3. Order a head CT before anything else
  4. Encourage brisk walking to "reset" the baroreflex
Show answer

Answer: B. Lie the patient down, then check orthostatic vitals and give fluids

Treat it as low-volume orthostatic hypotension: lie the patient down, then assess and give fluids and compression. Drugs such as midodrine have limited supporting data [1]. Still look for other causes such as arrhythmia, bleeding or thrombosis.

Learn more: Orthostatic intolerance (clinical) · Clinician quick-start · References

Q4 · Gravity · recovery

NASA crew are usually advised against which activity during the first week after landing?

  1. Reading
  2. Driving
  3. Eating solid food
  4. Sleeping lying flat
Show answer

Answer: B. Driving

NASA's entry, descent and landing brief notes crew are usually advised against driving during the early recovery period [3].

Learn more: Postflight recovery (clinical) · References

Q5 · Gravity · vestibular

About what share of first-time space flyers develop space motion sickness?

  1. Under 10%
  2. About 25%
  3. About 70–90%
  4. Everyone
Show answer

Answer: C. About 70–90%

NASA's space adaptation sickness brief cites about 70–90% of flyers, usually in the first 2–3 days [4].

Learn more: Space motion sickness (clinical) · References

Q6 · Gravity · vestibular

Which history best predicts space motion sickness?

  1. Childhood car sickness
  2. Seasickness
  3. Space motion sickness on a previous flight
  4. Fear of heights
Show answer

Answer: C. Space motion sickness on a previous flight

Terrestrial motion-sickness history does not reliably predict space motion sickness; a previous episode in space does [4].

Learn more: Space motion sickness (clinical) · References

Q7 · Gravity · vestibular

What is NASA's treatment of choice for space motion sickness?

  1. Ondansetron
  2. Promethazine
  3. Scopolamine patch before launch
  4. Meclizine
Show answer

Answer: B. Promethazine

Promethazine is NASA's treatment of choice, given by injection or suppository when vomiting [4]. In Shuttle crews, 14 of 15 treated by injection had relief within 1–2 hours [5].

Learn more: Space motion sickness (clinical) · References

Q8 · Gravity · vestibular

Why does NASA schedule spacewalks after the first 72 hours of a flight?

  1. To let the cabin air settle
  2. To allow space motion sickness symptoms to resolve
  3. Because suits need 3 days to charge
  4. To meet radiation limits
Show answer

Answer: B. To allow space motion sickness symptoms to resolve

Spacewalks are scheduled after 72 hours to allow recovery from symptoms; vomiting inside a helmet is a serious hazard [4].

Learn more: Space motion sickness (clinical) · DCS & EVA (clinical) · References

Q9 · Gravity · bone

About how fast do weight-bearing hip and spine lose bone mineral density in space?

  1. 0.1% per year
  2. 1–1.5% per month
  3. 5% per week
  4. They do not change
Show answer

Answer: B. 1–1.5% per month

NASA's bone loss brief describes losses of about 1–1.5% per month in weight-bearing bone [6].

Learn more: Bone loss (clinical) · References

Q10 · Gravity · bone

In a study of 17 astronauts, how many had not fully recovered tibia total bone mineral density 12 months after flight?

  1. None
  2. 2
  3. 9
  4. All 17
Show answer

Answer: C. 9

Nine of 17 astronauts had not fully recovered tibia total bone density after 12 months; recovery was poorer after missions longer than 6 months [7].

Learn more: Bone loss (clinical) · References

Q11 · Gravity · muscle

In ISS astronauts, peak aerobic capacity (VO2peak) early in flight fell by about:

  1. 2%
  2. 17%
  3. 40%
  4. 60%
Show answer

Answer: B. 17%

VO2peak fell about 17% early in flight, rose gradually but stayed below preflight, and recovered by 30 days after landing [8].

Learn more: Exercise countermeasures (clinical) · References

Q12 · Gravity · spine

About how common is space adaptation back pain?

  1. About 5% of astronauts
  2. About 25%
  3. About half (52% of 728)
  4. Nearly all (99%)
Show answer

Answer: C. About half (52% of 728)

A retrospective study found space adaptation back pain in 52% of 728 astronauts, mostly mild; the fetal position was the most effective treatment [9].

Learn more: Case: postflight back pain · References

Q13 · Gravity · eyes

Which finding is NOT part of spaceflight-associated neuro-ocular syndrome (SANS)?

  1. Optic disc edema
  2. Posterior globe flattening
  3. Chorioretinal folds
  4. A myopic (nearsighted) shift
Show answer

Answer: D. A myopic (nearsighted) shift

SANS includes a hyperopic (farsighted) shift, not a myopic one, along with disc edema, globe flattening and chorioretinal folds [10].

Learn more: SANS management (clinical) · References

Q14 · Gravity · eyes

About what share of long-duration crew show at least one sign of SANS?

  1. About 5%
  2. About 30%
  3. About 70%
  4. 100%
Show answer

Answer: C. About 70%

NASA reports about 70% of long-duration crew have one or more signs and about 18% are diagnosed with clinically concerning SANS [10].

Learn more: SANS management (clinical) · References

Q15 · Gravity · eyes

Which Earth analog produced optic disc edema in healthy volunteers?

  1. A 7-day Antarctic traverse
  2. 30 days of strict 6° head-down tilt bed rest
  3. A single parabolic flight
  4. Scuba diving to 30 m
Show answer

Answer: B. 30 days of strict 6° head-down tilt bed rest

Thirty days of strict head-down tilt bed rest produced optic disc edema in volunteers [11].

Learn more: SANS management (clinical) · Earth analogs (research) · References

Q16 · Kidneys

What is the main countermeasure against kidney stones in spaceflight?

  1. Bed rest
  2. High fluid intake
  3. Daily antibiotics
  4. A high-protein diet
Show answer

Answer: B. High fluid intake

Hydration is the key countermeasure. A NASA model suggests water intake of about 3.2 L/day would bring calcium oxalate risk back toward preflight levels [12].

Learn more: Kidney stone risk (clinical) · References

Q17 · Kidneys

For about a year after flight, how does estimated kidney-stone incidence compare with the preflight rate?

  1. It is lower
  2. It is unchanged
  3. About 2–7 times higher
  4. About 100 times higher
Show answer

Answer: C. About 2–7 times higher

NASA's 2024 evidence report estimates incidence approaching 2–7 times preflight levels one year after flight [12].

Learn more: Kidney stone risk (clinical) · References

Q18 · Kidneys

In a flight study of 30 crewmembers, what did potassium citrate (20 mEq/day) do?

  1. Increased stone formation
  2. Reduced calcium oxalate risk markers
  3. Prevented all bone loss
  4. Had no measurable effect
Show answer

Answer: B. Reduced calcium oxalate risk markers

Potassium citrate reduced urinary risk markers for calcium oxalate stones during flight [13].

Learn more: Kidney stone risk (clinical) · References

Q19 · Radiation

What is NASA's career spaceflight radiation limit?

  1. Less than 50 mSv
  2. Less than 600 mSv effective dose, for all ages and sexes
  3. 1,000 mSv for men and 400 mSv for women
  4. There is no limit
Show answer

Answer: B. Less than 600 mSv effective dose, for all ages and sexes

NASA-STD-3001 Volume 1 limits career effective dose to less than 600 mSv, the same for all ages and sexes [14].

Learn more: Radiation limits (clinical) · References

Q20 · Radiation

On average, how much does spacecraft shielding reduce galactic cosmic ray dose, according to NASA?

  1. About 7%
  2. About 50%
  3. About 90%
  4. 100%
Show answer

Answer: A. About 7%

NASA estimates only an average 7% reduction, which is why mission duration is the main lever for cosmic rays [15].

Learn more: Radiation limits (clinical) · References

Q21 · Radiation

Measurements from the Curiosity rover's cruise to Mars suggest a round trip with current propulsion would deliver about:

  1. 0.01 Sv
  2. 0.66 Sv
  3. 6 Sv
  4. 66 Sv
Show answer

Answer: B. 0.66 Sv

About 0.66 Sv (660 mSv), which is already above the career limit [16].

Learn more: Radiation limits (clinical) · Space Medicine 101 · References

Q22 · Isolation

Compared with adults on Earth, how did use of sleep medicines on the ISS compare in a review of crew medication records?

  1. About the same
  2. About 10 times higher
  3. Lower
  4. Sleep medicines are not flown
Show answer

Answer: B. About 10 times higher

Medication use on the ISS was similar to ambulatory medicine on Earth, except that sleep-aid use was about 10 times higher [17].

Learn more: Behavioral health (clinical) · References

Q23 · Isolation

What did the 520-day Mars-500 isolation study show about crew behavior?

  1. All crew reacted the same way
  2. Large differences between individuals
  3. No sleep changes at all
  4. Improved mood over time in everyone
Show answer

Answer: B. Large differences between individuals

Investigators observed substantial differences between individuals in behavioral and psychological responses to confinement [18].

Learn more: Behavioral health (clinical) · Earth analogs (research) · References

Q24 · Distance

On a crewed Mars mission, how long could a one-way radio message take?

  1. About 1 second
  2. About 1 minute
  3. Upward of 21–23 minutes
  4. About 6 hours
Show answer

Answer: C. Upward of 21–23 minutes

NASA's fact sheet says the one-way delay can be upward of 21–23 minutes, depending on trajectory, with blackout periods as well [19].

Learn more: In-flight emergencies (clinical) · References

Q25 · Environment · EVA

After a decompression, when do most cases of decompression sickness (DCS) present?

  1. Within 5 minutes
  2. 60–240 minutes
  3. 2–3 days
  4. 1–2 weeks
Show answer

Answer: B. 60–240 minutes

NASA's DCS brief states most cases present between 60 and 240 minutes after decompression [20].

Learn more: DCS & EVA (clinical) · References

Q26 · Environment · EVA

Which symptom after a spacewalk indicates Type II (serious) DCS?

  1. Itching
  2. Mild rash
  3. Joint ache
  4. Numbness or weakness
Show answer

Answer: D. Numbness or weakness

Type I DCS is itching, joint or muscle pain and mild rash. Neurological, inner-ear and cardiopulmonary symptoms are Type II [20].

Learn more: DCS & EVA (clinical) · Case: DCS after EVA · References

Q27 · Environment · EVA

What must NASA prebreathe protocols demonstrate in ground chamber tests?

  1. Zero bubbles in every subject
  2. Less than 4% DCS probability with 95% confidence
  3. Less than 50% DCS
  4. Only that suits stay pressurized
Show answer

Answer: B. Less than 4% DCS probability with 95% confidence

Protocols must show less than 4% DCS probability with 95% confidence, and no serious DCS [20][21].

Learn more: DCS & EVA (clinical) · References

Q28 · Environment · atmosphere

NASA-STD-3001 Volume 2 limits the 1-hour average cabin carbon dioxide partial pressure to no more than:

  1. 0.3 mmHg
  2. 3 mmHg
  3. 30 mmHg
  4. 300 mmHg
Show answer

Answer: B. 3 mmHg

Volume 2 limits the one-hour average ppCO₂ in the habitable volume to no more than 3 mmHg [21].

Learn more: SANS management (clinical) · Standards quick reference · References

Q29 · Commercial spaceflight

Under 14 CFR Part 460, what must U.S. operators provide to spaceflight participants?

  1. A NASA medical certification
  2. Written information about risks (informed consent) and emergency training
  3. A hospital bed on board
  4. Nothing; Part 460 does not apply
Show answer

Answer: B. Written information about risks (informed consent) and emergency training

Operators must inform participants in writing about known and unknown hazards and train them for emergencies. Part 460 does not set medical standards for participants [22].

Learn more: SFP screening (clinical) · References

Q30 · Commercial spaceflight

In the FAA's 2006 advisory screening guidance, which flights fall into the more thorough tier 2?

  1. Only flights to Mars
  2. Orbital flights, or any flight above +3 Gz
  3. Parabolic flights only
  4. Suborbital flights below +3 Gz
Show answer

Answer: B. Orbital flights, or any flight above +3 Gz

Tier 2 covers orbital flights of any duration and any flight above +3 Gz; it suggests a full questionnaire, exam and labs [23].

Learn more: SFP screening (clinical) · Case: SFP with hypertension · References

Evidence profile
Overall certainty
◆◆◆◇ Moderate (proposed)
Evidence types
F · Flight dataA · Terrestrial analogE · Expert / operational / standardsC · Computational
Literature through
2026-10-14
Credit
Educational only; no CME or other credit
Requirements referenced 0

No NASA-STD-3001 requirement maps directly to this page. See the standards quick reference.

References 23
  1. NASA OCHMO. Orthostatic Intolerance. Technical Brief OCHMO-TB-019. www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-019-orthost… NASA E
  2. Lee SMC, Feiveson AH, Stein S, Stenger MB, Platts SH. Orthostatic intolerance after ISS and Space Shuttle missions. Aerosp Med Hum Perform. 2015;86(12 Suppl):A54–A67. doi:10.3357/AMHP.EC08.2015 PMID:26630196 Peer-reviewed F
  3. NASA OCHMO. Crew Medical Support for Entry, Descent, and Landing. Technical Brief OCHMO-TB-051 (2026). www.nasa.gov/wp-content/uploads/2026/05/ochmo-tb-051-crew-me… NASA E
  4. NASA OCHMO. Space Adaptation Sickness (SAS). Medical Technical Brief OCHMO-MTB-004 (2025). www.nasa.gov/wp-content/uploads/2025/09/ochmo-mtb-004-space-… NASA E
  5. Davis JR, Jennings RT, Beck BG. Comparison of treatment strategies for space motion sickness. Acta Astronaut. 1993;29(8):587–591. doi:10.1016/0094-5765(93)90074-7 PMID:11541638 Peer-reviewed F
  6. NASA OCHMO. Bone Loss. Medical Technical Brief OCHMO-MTB-013, Rev D (2026). www.nasa.gov/wp-content/uploads/2026/02/ochmo-mtb-013-bone-l… NASA E
  7. Gabel L, Liphardt AM, Hulme PA, et al. Incomplete recovery of bone strength and trabecular microarchitecture at the distal tibia 1 year after return from long duration spaceflight. Sci Rep. 2022;12:9446. doi:10.1038/s41598-022-13461-1 PMID:35773442 Peer-reviewed F
  8. Moore AD Jr, Downs ME, Lee SMC, Feiveson AH, Knudsen P, Ploutz-Snyder L. Peak exercise oxygen uptake during and following long-duration spaceflight. J Appl Physiol. 2014;117(3):231–238. doi:10.1152/japplphysiol.01251.2013 PMID:24970852 Peer-reviewed F
  9. Kerstman EL, Scheuring RA, Barnes MG, DeKorse TB, Saile LG. Space adaptation back pain: a retrospective study. Aviat Space Environ Med. 2012;83(1):2–7. doi:10.3357/asem.2876.2012 PMID:22272509 Peer-reviewed F
  10. NASA OCHMO. Spaceflight Associated Neuro-ocular Syndrome (SANS). Medical Technical Brief OCHMO-MTB-001 (2024). www.nasa.gov/wp-content/uploads/2024/02/ochmo-mtb-001-sans.p… NASA E
  11. Laurie SS, Macias BR, Dunn JT, et al. Optic disc edema after 30 days of strict head-down tilt bed rest. Ophthalmology. 2019;126(3):467–468. doi:10.1016/j.ophtha.2018.09.042 Peer-reviewed A
  12. NASA Human Research Program. Evidence Report: Risk of Renal Stone Formation (2024). humanresearchroadmap.nasa.gov/evidence/other/2024%20Renal%20… NASA F
  13. Whitson PA, Pietrzyk RA, Jones JA, Nelman-Gonzalez M, Hudson EK, Sams CF. Effect of potassium citrate therapy on the risk of renal stone formation during spaceflight. J Urol. 2009;182(5):2490–2496. doi:10.1016/j.juro.2009.07.010 PMID:19765769 Peer-reviewed F
  14. NASA OCHMO. NASA-STD-3001, Volume 1: Crew Health, Revision C (2023). www.nasa.gov/wp-content/uploads/2023/11/nasa-std-3001-vol-1-… Standard E
  15. NASA OCHMO. Design for Ionizing Radiation Protection. Technical Brief OCHMO-TB-020. www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-020-radiati… NASA E
  16. Zeitlin C, Hassler DM, Cucinotta FA, et al. Measurements of energetic particle radiation in transit to Mars on the Mars Science Laboratory. Science. 2013;340(6136):1080–1084. doi:10.1126/science.1235989 PMID:23723233 Peer-reviewed F
  17. Wotring VE. Medication use by U.S. crewmembers on the International Space Station. FASEB J. 2015;29(11):4417–4423. doi:10.1096/fj.14-264838 PMID:26187345 Peer-reviewed F
  18. Basner M, Dinges DF, Mollicone DJ, et al. Psychological and behavioral changes during confinement in a 520-day simulated interplanetary mission to Mars. PLoS One. 2014;9(3):e93298. doi:10.1371/journal.pone.0093298 PMID:24675720 Peer-reviewed A
  19. NASA. Mars Communications Disruption and Delay (fact sheet, 2024). www.nasa.gov/wp-content/uploads/2024/01/mars-communications-… NASA E
  20. NASA OCHMO. Decompression Sickness (DCS) Risk Mitigation. Technical Brief OCHMO-TB-037. www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-037-decompr… NASA E
  21. NASA OCHMO. NASA-STD-3001, Volume 2: Human Factors, Habitability, and Environmental Health, Revision F (2026). standards.nasa.gov/standard/NASA/NASA-STD-3001_VOL_2 Standard E
  22. 14 CFR Part 460 — Human Space Flight Requirements. eCFR, current. www.ecfr.gov/current/title-14/chapter-III/subchapter-C/part-… FAA / regulation E
  23. Antuñano MJ, Baisden DL, Davis J, et al. Guidance for Medical Screening of Commercial Aerospace Passengers. FAA Office of Aerospace Medicine; DOT/FAA/AM-06/1. January 2006. www.faa.gov/media/72446 FAA / regulation E

Machine-checked on 2026-10-14: each URL was fetched, each DOI's title/journal/year matched via Crossref, PubMed IDs matched to DOIs, and claims were checked against the source text (abstract, NASA document or official web page). Human verification against full text is still required before review. NASA documents are U.S. Government works (public domain) and are summarized with attribution; journal articles are summarized, not reproduced.

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