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EXP-02 · Interactive explorer · Explore

Mission Timeline Explorer: When Each Risk Matters

Also: spaceflight risk timeline · mission phase hazards

Radiation Isolation & Confinement Distance from Earth Gravity Fields Hostile/Closed Environment Launch & Ascent In-flight EVA & Surface Ops Entry, Descent & Landing Postflight Recovery Lifetime Surveillance LEO short-duration LEO long-duration Cislunar / Lunar orbit Lunar surface Mars transit & surface Public Student Clinician Researcher Operator / Spaceflight participant Astronaut & candidate

AI-assisted Last reviewed: 2026-10-15 · Reviewer: AI-assisted clinical review (AI medical research assistant; no named human clinician)

Bottom line

Some risks peak in the first days (fluid shift, space motion sickness), some build with time in flight (radiation, bone and muscle loss, eye changes), and some peak after landing (fainting on standing, unsteadiness) [8][9][15][20]. ◆◆◆◆ High · F E
Distance changes medical care: from lunar orbit a signal takes about 1.3 seconds, at Mars from a few minutes up to about 22 minutes (NASA: longest delays about 21–23 minutes), and there is no emergency evacuation during a Mars transit [2][6]. ◆◆◆◆ High · E
A Mars orbital mission is about 2 to 3 years; NASA’s concept lists 6–9 months each way and 2–17 months in Mars orbit [2]. ◆◆◆◆ High · E

Proposed certainty (◆ High → ◇ Very low) and evidence-type tags: F flight · A analog · M model/animal · C computational · E expert/operational/standards. AI-proposed, pending reviewer confirmation. How to read the grades.

Mission timeline · launch → landing → recovery

Educational only — not for clinical decisions

Mission profile

Short orbital Space station Moon Mars

Launch date (Eastern Time)

Mission day0Launch day

Date (ET)—

Signal delay—

Move through the mission

Left 70% of the chart: launch to landing. Right 30%: recovery on Earth. Darker = matters more (qualitative). The vertical line is the selected day.

Risks on the selected day

Launch and landing forces
- Launch and landing expose crews to acceleration, vibration and impact. Landing-day medical teams are on standby. [7]
Fluid shift (blood moves toward the head)
- In weightlessness, fluid shifts toward the head. Within about 2 days the body lowers circulating blood volume by around 15%. [8]
Space motion sickness
- Space motion sickness affects most first-time flyers (NASA: about 73% in the first days of a first flight, 70–90% overall; an older brief gives 50–70%) and usually resolves within about 72 hours. Spacewalks are not scheduled in the first 72 hours. [9][10]
Spacewalks: decompression sickness
- Spacewalks (on the space station or the lunar surface) carry a risk of decompression sickness, prevented by breathing pure oxygen first. [11]
- Spacewalk days are shown as possible across the stay; real schedules vary by mission.
Radiation exposure
- Radiation dose builds up for the whole flight. In low Earth orbit, Earth's magnetic field concentrates cosmic rays and solar-storm protons near the poles; beyond low Earth orbit, the vehicle is continually exposed to galactic cosmic rays. [12]
- A Mars round trip was estimated at about 660 millisieverts (mSv), above NASA's 600 mSv career limit. [13][14]
Bone and muscle loss
- On long missions, hip and spine bone loses about 1–1.5% of mineral density per month. [15]
- NASA treats about 30 days as the dividing line between short and long missions because of physiological changes. [4]
- Shin-bone density had not recovered in 9 of 17 astronauts a year after flight. [16]
Eye and optic nerve changes
- Eye and optic nerve changes (spaceflight-associated neuro-ocular syndrome, SANS) occur on long-duration missions: about 70% of crew show at least one sign. Eyes are monitored after return. [17]
Kidney stones
- Less urine and more urinary calcium raise stone risk in flight; in the year after flight, stone incidence may approach 2–7 times preflight. [18]
Isolation, sleep and mood
- Isolation and confinement can affect sleep, mood and teamwork; behavioral health support continues throughout a mission. [19]
Distance: signal delay and no quick return
- Far from Earth, messages are delayed and a fast trip home is not possible, so the crew must handle medical problems on their own. [2]
Fainting on standing, unsteadiness
- After landing, many crewmembers feel faint on standing; this is worse after long missions and most had recovered by about 3 days. [20][8]
- Walking and balance recover over about two weeks after long missions. [21]
Exams and reconditioning
- Example exam days after a long mission: landing day, then about 3, 7–14 and 60 days after return; reconditioning starts at exit from the vehicle. [4][14]
- Returning crew are monitored for life. [14]

Mission phases and where the durations come from

Short orbital flight (3 days)

In orbit: 3 days. Modeled on the 3-day Inspiration4 civilian orbital mission. [1]
Signal delay: Real time (low Earth orbit) [2]
Getting home: Return to Earth possible [3]

Space station mission (6 months)

Low Earth orbit (space station): 180 days. NASA uses a typical 180-day space station mission as its example schedule. [4]
Signal delay: Real time (low Earth orbit) [2]
Getting home: Evacuation to Earth feasible in a reasonable time [5]

Lunar mission (example: 30 days at the Moon)

Earth to lunar orbit: 4 days. About 3.5 days from launch to the lunar Gateway orbit in NASA's concept of operations (rounded up). [2]
At the Moon (example stay): 30 days. Example length you can change. NASA's older levels of care treat 30 days or less beyond low Earth orbit as a short mission. [3]
Return and landing: 5 days. About 5 days from lunar orbit to landing in NASA's concept of operations. [2]
Signal delay: About 1.3 seconds one way from lunar orbit [2]
Getting home: Return to definitive care takes days [2]

Mars orbital mission (about 2.5 years)

Earth to lunar Gateway: 4 days. About 3.5 days (rounded up). [2]
Transit to Mars: 228 days. NASA range 6–9 months; midpoint shown. [2]
Mars orbit: 289 days. NASA range 2–17 months; midpoint shown. [2]
Return to Gateway: 228 days. NASA range 6–9 months; midpoint shown. [2]
Gateway to landing: 5 days. About 5 days. [2]
Signal delay: A few minutes up to about 22 minutes one way at Mars (NASA: longest delays about 21–23 minutes), with possible blackouts of about 2 weeks [2][6]
Getting home: No emergency evacuation during transit or Mars orbit [2]

How to use it

Choose a mission profile.
Set a launch date (Eastern Time). Dates along the timeline update.
Drag the slider, or use the arrow keys, from launch to landing and through recovery. The chart highlights the risks that matter on that day, and the list below explains each one.

Mission lengths come from NASA documents (cited under each phase). The lunar surface stay is an example you can change.

Reading the bars

The shading is a qualitative teaching aid chosen by the editors: light means the risk is present, darker means it matters more. It is not a measured probability. Use the linked pages and the radiation dose estimator and recovery timeline tools for numbers.

Evidence profile

Overall certainty: ◆◆◆◇ Moderate (proposed)
Evidence types: F · Flight dataE · Expert / operational / standards
Literature through: 2026-10-14
Validation: Statements checked against the cited sources; the explorer is not clinically validated
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 21

Jones CW, Overbey EG, Lacombe J, et al. Molecular and physiological changes in the SpaceX Inspiration4 civilian crew. Nature. 2024;632:1155–1164. doi:10.1038/s41586-024-07648-x PMID:38862026 Peer-reviewed F
NASA Human Research Program, Exploration Medical Capability Element. Medical System Concept of Operations for Mars Exploration Mission-11. HRP-48021, Baseline (April 2019). ntrs.nasa.gov/api/citations/20200001715/downloads/2020000171… NASA E
NASA. NASA-STD-3001, Volume 1, Revision A (2014-07-30; historical). Section 4.1 Levels of Medical Care. standards.nasa.gov/sites/default/files/standards/NASA/B/Hist… Standard E
NASA OCHMO. NASA Spaceflight Medical Selection, Recertification and Mission Evaluation Standards. OCHMO-STD-100.1A, Revision A (2024). ntrs.nasa.gov/citations/20240006194 Standard E
NASA Human Research Program. Evidence Report: Risk of Adverse Health Outcomes and Decrements in Performance due to In-Flight Medical Conditions (2017). humanresearchroadmap.nasa.gov/evidence/reports/Medical.pdf NASA F
NASA. Mars Communications Disruption and Delay. 2023 Moon to Mars Architecture Concept Review fact sheet (2024). www.nasa.gov/wp-content/uploads/2024/01/mars-communications-… NASA E
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
NASA OCHMO. Orthostatic Intolerance. Technical Brief OCHMO-TB-019. www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-019-orthost… NASA E
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
NASA OCHMO. Spaceflight Experience and Medical Care. Technical Brief OCHMO-TB-033. www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-033-spacefl… NASA E
NASA OCHMO. Decompression Sickness (DCS) Risk Mitigation. Technical Brief OCHMO-TB-037, Revision D (2026). www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-037-decompr… NASA E
NASA Human Research Program. Evidence Report: Risk of Ionizing Radiation Carcinogenesis (2026). Table 3, Design Reference Mission categories. humanresearchroadmap.nasa.gov/evidence/reports/HRP-ER-CANCER… NASA C
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
NASA OCHMO. NASA-STD-3001, Volume 1: Crew Health, Revision C (2023). [V1 3004], [V1 3017], [V1 3018], [V1 4030]–[V1 4033] and Table 4.8-1. www.nasa.gov/wp-content/uploads/2023/11/nasa-std-3001-vol-1-… Standard E
NASA Human Research Program. Evidence Report: Risk of Bone Fracture due to Spaceflight-induced Changes to Bone (July 18, 2024). humanresearchroadmap.nasa.gov/evidence/reports/Bone%20Fractu… NASA F
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
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
NASA Human Research Program. Evidence Report: Risk of Renal Stone Formation (2024). humanresearchroadmap.nasa.gov/evidence/other/2024%20Renal%20… NASA F
NASA OCHMO. Behavioral Health and Performance. Technical Brief OCHMO-TB-016. www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-016-behavio… NASA E
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
Mulavara AP, Feiveson AH, Fiedler J, et al. Locomotor function after long-duration space flight: effects and motor learning during recovery. Exp Brain Res. 2010;202(3):649–659. doi:10.1007/s00221-010-2171-0 PMID:20135100 Peer-reviewed F

Machine-checked on 2026-10-14: each URL was fetched, each DOI's title and year matched via Crossref, PubMed IDs matched to DOIs, and every number shown was checked against the source text (abstract, NASA document, regulation or official web page). Human verification against full text is still required before review.

Article info

Authors: Pending (AI-assisted)
Reviewer: AI-assisted clinical review (AI medical research assistant; no named human clinician)
Last reviewed: 2026-10-15
Literature through: 2026-10-14
AI-assisted: Yes (disclosed)
COI: Pending
License: CC BY-SA 4.0 (text); code MIT
Privacy: Runs entirely in your browser; no inputs stored or sent
Use: Educational only · not for clinical decisions · Disclaimer
Cite this version: Pending first edition

Educational use only · not medical advice · not for clinical decisions · Disclaimer · CC BY-SA 4.0