This document summarizes the key effects of the launch environment and microgravity (zero-G) on humans. It discusses how launch subjects astronauts to loads, noise and vibrations. In zero-G, fluids shift upwards causing puffy faces and reduced blood pressure, and bones and muscles weaken over time from inactivity. It also outlines some of the cardiovascular, vestibular and musculoskeletal issues astronauts experience such as bone and muscle loss, flat backs, and motion sickness. Countermeasures are needed to mitigate these environmental stressors.

1. Space Environment
Lecture 5 – Effects on humans
Launch and Zero ‘G’
Professor Hugh Lewis
SESA3038 Space Environment

2. Overview of lecture 5
• In this lecture we will take a high-level look at two key environments and
their effects on humans
– The launch environment
– Zero ‘G’ or microgravity
• We will look at countermeasures that can be employed to reduce or remove
these effects in a later lecture
Space Environment – Environmental effects

3. • Launch
• Zero ‘G’
• Radiation
• Thermal
• High vacuum
Environmental effects Space Environment – Environmental effects

4. • Transient
– Occurs only during the first few days of flight,
e.g. space sickness
• Whole flight
– Adaptation occurs during flight and returns to
normal rapidly on the ground, e.g. height
increase
• Cumulative reversible
– Effects which accumulate during flight but
return eventually to normal on ground, e.g.
calcium loss
• Cumulative non-reversible
– Effects which accumulate but are not reversible
once back on the ground, e.g. radiation damage
caused by high-energy particles
Responses Space Environment – Environmental effects

5. • Astronauts are subjected to loads, acoustic
noise, vibration and shocks
Launch Space Environment – Environmental effects

6. Redistribution of fluids:
Fluids shift towards the upper body as they don’t have to ‘fight’ against gravity
Zero ‘G’ Space Environment – Environmental effects
Blood pressure (BP):
Earth: Brain ~ 60 mmHg
Feet ~ 180 mmHg
Zero ‘G’: Uniform BP

7. Redistribution of blood volume:
• 0.6-2 litres of blood is transferred
from the feet to above the heart
• Puffy faces and ‘Chicken legs’
• Excess blood in the heart
• Complex hormonal reaction in
kidney (Antidiuretic Hormone –
ADH)
• Loss of body fluid (2-4 kg)
• Loss of Na
• Orthostatic intolerance – difficulty or
inability to stand as a result of light
headedness and/or fainting after
return to Earth
Zero ‘G’ Space Environment – Environmental effects

8. Other impacts on cardiovascular system
• Blood is not being pumped against gravity
• Heart changes shape from an oval to a
round ball Reduction in heart rate
• Reduction in heart muscle activity
• Atrophy of heart muscle and blood vessels
Other muscles in the body experience atrophy
• Impaired motor control
• Impaired balance
Zero ‘G’ Space Environment – Environmental effects
https://www.nasa.gov/mission_pages/station/research/station-science-101/cardiovascular-health-in-microgravity/

9. Vestibular problems:
• Vision and tactile sensors
• The increase in fluid within the skull is
thought to increase brain pressure,
which can cause hearing loss, brain
oedema and deformation of the eye
known as Spaceflight Associated
Neuro-ocular Syndrome (SANS).
Zero ‘G’ Space Environment – Environmental effects
https://www.nature.com/articles/s41526-020-0097-9
Post-flight imaging:

10. Vestibular problems:
• Inner ear
• Floating/falling sensations when
moving (vertigo and spatial
disorientation)
• Inversion illusions
• Clumsiness
• Motion sickness
– 9 out of 25 Apollo astronauts
experienced sickness
Zero ‘G’ Space Environment – Environmental effects
Rusty Schweickart – Apollo 9

11. Musculoskeletal/locomotor system
• Bone loss/decalcification
• Variable but cumulative: 1-2% per
month
• Increased mobility of Ca in body and
• Recalcification outside bones, e.g.
kidney stones
• Impaired fracture repair
• Reduced bone strength
Zero ‘G’ Space Environment – Environmental effects
Normal bone
Osteoporotic bone

12. Musculoskeletal/locomotor system
• Reduced activity in key lumbar and abdominal
muscles
• Loss of lordosis (flat back)
• Deconditioned intervertebral discs linked
with spinal lengthening
• 68% incidence of low back pain during missions
• 4.3 times higher risk of herniated discs post-
spaceflight
• No evidence-based countermeasures have been
shown to prevent all lumbopelvic changes –
reconditioning is needed
Zero ‘G’ Space Environment – Environmental effects
Microgravity posture
(Buckey, 2006,
“Space Physiology”)

13. Anaemia
• Reduction in red blood cell generation by
15% over three months
• Change in shape of cells from discs into
spheres
• Increase in white blood cells
• Possible causes:
• Loss of muscle mass
• Changes in blood flow
• Possible changes in bone marrow
Zero ‘G’ Space Environment – Environmental effects
http://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Eneide_-_Vittori_mission/Ground_experimental_programme

14. Activity
• You can find articles and reports covering the
contents of lectures 5 to 8 in the “Course
Content” folder on the Blackboard site:
• Reading these is not compulsory (especially because
some of the reports are long) but could provide
deeper insights into the topics we have covered
• Some of these articles are also linked to or cited in te
lecture slides
Space Environment – Environmental effects