OBJECTIVES
1. Identify and explain the primary factors of the space flight environment that affect human life and health
2. Outline the fundamental requirements of life support
1. Relevant parameters of the space flight environment
a. Vacuum
Where does space begin?
Standard Atmosphere at sea level = 14.7 psia, 760 mm HG or 760 Torr (~21%O2 / 79%N2)
~½ of Earth’s atmosphere is below 5 km MSL
atmosphere extends out only 2/1000 of the radius of the planet
total mass of the atmosphere is ~5.6 x 1014 tons
50 miles (264,000 ft or 80 km) – height recognized by the U.S. Air Force as being in space
62 miles (328,000 ft or 100 km) – internationally accepted boundary of space set by the Fédération Aéronautique Internationale
Astronaut wings awarded to the three civilian research pilots who flew the X-15 into space in the mid-1960s (article, 8/23/05)
Strughold (1951) defined the transition from terra firma to “space” as consisting of 9 regions.
Region 1 – 4 km (~13,000 ft) and up, O2 must be provided for sustained proper functioning
above ~15 km (~50,000 ft), P tot = 87 Torr, O2 must be provided under pressure
Region 2 – H2O vapor pressure of body at 37 C is 47 mm Hg, barometric pressure at 20 km (65,616 ft), Armstrong Limit
above ~20 km – pressurized environment needed for protection of human body
Region 3 ~25 km (82,020. ft), pressurized, sealed cabin needed since compressing air to necessary levels becomes technologically challenging
Region 4 – radiation hazard, high-energy particles, begins above 40 km (131,233 ft)
Region 5 – solar UV energy hazard if unprotected, ozone insufficient to protect above 45 km (147,637 ft)
above ~45 km (150,000 ft) - propulsion requires oxidizer
above ~60 km (200,000 ft) - curvature of Earth becomes noticeable and the sky starts to become black in daytime
Region 6 – blackness of space, 100 km (328,083 ft or 62 miles), light scattering no longer occurs
above ~100 km (328,083 ft) - von Karman line, aerodynamic control becomes ineffective, RCS needed
Region 7 – “silence” of space, density insufficient to propagate sound waves, no sonic boom, no speed of sound, above 120 km
Region 8 – meteor danger, above 140 km
Region 9 – above 150 km, air insufficient to provide resistance, heating or aerodynamic supporting force (“aerothermodynamic” border), “weightlessness”
above ~200 km (650,000 ft) – atmospheric resistance becomes insignificant (10-6 Torr)
~700 km – upper boundary of Earth’s atmosphere
~2000 km – pressure is around 10-12 – 10-16 Torr
Critical aspects of pressure - P total, ppO2, ppN2, ppCO2 and dP/dt
Atmospheric pressure vs. in vivo hydrostatic pressure
Good “Rule of Thumb” data point - 10k MSL ~10 psia
Boyle’s Law: P1V1 = P2V2 at constant T
Charles’ Law: V1T2 = V2T1 at constant P
Combining gives the General Gas Law: (P1V1)/T1 = (P2V2)/T2
More commonly written: PV = nRT
n – # moles
R – derived from PV at standard T and P
Henry’s Law: quantity of gas dissolved in liquid is proportional to pp of the gas in contact with the liquid
Relationship of P and dissolved gas becomes important when undergoing pressure changes
b. Weightlessness
“0-G and I feel fine.” John
Glenn, 1962
(no gravity, 0g, micro-G, reduced-G, hypo-G)
F = ma = 0?
True “0g” vs. weightless “freefall”
- An object will remain at rest or in motion unless acted on by an external force
- Change in momentum is proportional to force and direction
- For every action, there is an equal and opposite reaction
Force of gravity can only be felt by an "equal and opposite" reaction
Theoretically, a net ‘0g’ can only occur at CG of the spacecraft – g-gradients will exist elsewhere
Other forces due to onboard machinery, atmospheric drag, orbit perturbations related to shape of Earth, solar wind, thruster firings, etc.
DC vs. AC acceleration
Launch and landing loads must also be addressed
Parabolic Flight Characteristics
c. Micrometeoroids and
Orbital Debris
Relative velocity - impact force
Spacecraft attitude
EVA restrictions
MLI
d. Radiation
EM - characterized by wavelength
- High in flux, low in energy
Particulate - characterized by mass and velocity
- Low in fluz, high in energy
- Intergalactic (Hze) particles
Single Event Upsets (SEUs)
- Computers / Humans?
Shielding Issues
e. Temperature Extremes
Hot or Cold?
- exposure and distance to sun
- absorptivity : reflectivity ratio (external surface properties can be used for passive thermal control)
Spacecraft environment in LEO ranges from approximately -120 to +110°C
Temperature of Lunar surface varies from -173 to +127° C
2. Fundamental requirements of life support (or
overcoming the space environment)
Consumable provision
AIR / WATER / FOOD
3 min / 3 days / 3 weeks
Metabolic byproducts (waste collection)
Pressure and Atmosphere composition
– “normoxic conditions” = standard atmosphere equivalent pp of O2 (3.1 psia)
– relationship to human physiology and spacecraft structure requirements
Thermal control and Humidity control
– conduction, convection and radiation heat transfer
– air, water, freon, other convective media
– air heat exchanger / slurper and humidity seps (no natural convection)
Radiation and Debris Shielding
– MLI, issues of “starburst effect”, secondary radiation concerns
– Protect crew from exposure or mitigate effects with pharmaceuticals?
Artificial gravity
– What level is sufficient?
– What duration is needed?
– Centripetal vs. linear acceleration
Misc. Related Useful Links for the Semester…
Research on ISS http://spaceresearch.nasa.gov/research_projects/ros/ros.html
Nat’l Space Biomedical Research Institute http://www.nsbri.org/
Bioastronautics Roadmap http://bioastroroadmap.nasa.gov/index.jsp
NASA Human Space Flight http://spaceflight.nasa.gov/index.html
NASA JSC Advanced Life Support http://advlifesupport.jsc.nasa.gov/
ASGSB - American Soc for Grav and Space Biology http://asgsb.org/
COSPAR - Committee on Space Research http://www.cosparhq.org/
Society for Human Performance in Extreme Environs http://www.hpee.org
Aerospace Medical Association http://www.asma.org/
National Academies Space Study Board http://www.nas.edu/ssb/csbmmenu.htm
Copyright © 2008 The
Regents of the