Earth Analogs for Spaceflight

At a glance

”Models well / misses” combines what the cited sources state with SMF editorial judgment (E). Gravity and space radiation can’t be reproduced by any isolation analog.

Head-down bed rest

The most common analog for weightlessness. The 6° head-down tilt reproduces the headward fluid shift better than lying flat. It is widely used for bone, muscle and cardiovascular research and to test countermeasures. It is less representative for fluid shifts, spinal problems and radiation [1]. Plasma volume drops 10–15% [2]. Details: Bed-rest studies.

Antarctica: Concordia station

ESA has sent a medical doctor to Concordia station for 13-month stays for two decades [3]. The station sits at 3,200 m on the Dome C plateau, equivalent to about 4,000 m at the equator, with air pressure of 645 hPa, causing chronic hypobaric hypoxia [4]. There is no access from mid-February to mid-November [4]. The winter crew is about 12 people, through four months without sunrise and temperatures down to −80 °C [3]. Across polar expeditions, about 5% of people meet psychiatric criteria. Many also report positive growth [5].

HI-SEAS (Hawaiʻi Space Exploration Analog and Simulation)

A habitat at about 8,200 ft on Mauna Loa, Hawaiʻi [6][7]. NASA funded a series of long-duration Mars-simulation missions, including HI-SEAS’s first one-year isolation mission, which ended on August 28, 2016 [6][7]. Research focused on crew composition and cohesion. Delayed communication and partial self-sufficiency were built in [7]. The HI-SEAS website describes six NASA-funded missions in 2013–2017 [8] (pending verification: the site blocks automated access).

NEEMO (NASA Extreme Environment Mission Operations)

Crews live in the Aquarius undersea habitat, 62 ft (19 m) below the surface off Florida, off Key Largo and operated by Florida International University, for missions of up to three weeks. They become saturation divers, and weighting simulates different gravity levels for spacewalk-like tasks [9].

Mars-500

A 520-day high-fidelity Mars mission simulation with a multinational crew of six men in a 550 m³ facility [10][11]. Crew activity fell over the mission, and sleep timing changed [10]. Psychological responses varied widely between individuals. Crew reported conflicts with mission control about five times more often than conflicts within the crew [11]. See also ESA’s Mars500 page [12].

HERA (Human Exploration Research Analog)

A 650 sq ft habitat for crews of four, on missions of up to 45 days, used for repeatable isolation and confinement campaigns [13].

CHAPEA (Crew Health and Performance Exploration Analog)

Four volunteers live in a 1,700 sq ft 3D-printed habitat at Johnson Space Center for year-long simulated Mars-surface missions, with simulated spacewalks and resource limits. Mission 1 ran June 25, 2023 to July 6, 2024. Mission 2, a 378-day mission, began October 19 and runs until October 31, 2026 [14].

Parabolic flight

An aircraft flies repeated arcs, giving about 20 seconds of reduced gravity per parabola, typically 15–30 parabolas per flight [15]. It is the only ground-based way to get true 0 g. It is especially useful for neurovestibular research, human factors, locomotion, medical procedures and partial-gravity work [16].

What analogs teach overall

Isolation and confinement on their own cause neurocognitive changes, fatigue, circadian misalignment, sleep problems, altered stress hormones and immune changes [17]. In team analogs, all teams report at least one conflict by 40% of the mission or 90 days [18].