Humans in Space

Copyright © 1997 by Dava J. Newman. All rights reserved.
No material from this web site may be reproduced, distributed, or transmitted, in any form or by any means, or stored in a database or retrieval system.
This section includes the following:

Dot History of Spacesuits
Dot Life Support Systems
Dot Extra Vehicular Activity
Dot Virtual Spacewalk (Stephen Maher, Goddard Space Flight Center)
Dot Special Classroom Projects

Life Support Systems

Life support is the maintenance of a life form's natural functions in a hostile environment where life simply cannot sustain itself. Mankind's journeys have taken people to the harsh environment of space and the upper atmosphere, where life support is crucial and complex. Here humans combat extreme temperatures, dangerous radiation, and the breathless vacuum of space.

Artificial Atmospheres

The most crucial element of life support in space is a breathable atmosphere. A human in space, whether in a craft, station, or suit, must have air. Choosing the composition of an artificial atmosphere, however, is difficult. The table below shows atmospheric mixes for various stages of the American space program.

Table of Atmospheric Concentrations
Atmosphere of Pressure Oxygen Nitrogen Comments Earth 14.7 psi 21% 78% Traces of other gases Early space capsules 5 psi 100% 0% Mercury, Gemini, Apollo Skylab 5 psi 70% 30% First space station, 1973 Space shuttles 14.7 psi 20% 80% Closest to Earth's U.S. spacesuit 4.3 psi 100% 0% Present-day; used for EVA's* * Extra Vehicular Activities

Physiological, engineering, cost, and safety factors must be considered when designing artificial atmospheres. Physiologically, an atmospheric mixture of nitrogen and very little oxygen can promote hypoxia. Excessive amounts of oxygen will prompt the opposite condition, hyperoxia. Incorrect concentrations can also cause hypercapnia, an abnormal increase of carbon dioxide in the blood, or even altitude decompression sickness (ADS). If sufficient forced ventilation is provided, such problems are alleviated or prevented.

The importance of the safety factor was tragically emphasized when during a test on the launch pad, Apollo 1 caught fire. An electrical short ignited the oxygen-rich air. All three crew members were killed.

Plans for the International Space Station demonstrate the engineering required for artificial atmospheres and related systems. Six systems under development include fire detection and suppression, atmosphere revitalization, temperature and humidity control, atmosphere control and supply, waste management, and water recovery systems. All systems, whether involving the air supply or not, must meet limited weight, power, and reliability requirements.


Spacesuits must meet stringent requirements for life support. The suit has to be of durable material to withstand the impact of space debris and protect against radiation. It must provide essential oxygen, pressure, heating, and cooling, while retaining mobility and dexterity. The design requirements for suits are indeed impressive and complex, yet both Russian and American space programs have succeeded in developing functional suits.

Today, American astronauts performing extra vehicular activities use a spacesuit containing 100% oxygen at a pressure of 4.3 psi. However, with such a high oxygen concentration, astronauts reentering the shuttle sometimes suffer from decompression sickness, simliar to what ocean divers experience after returning to the surface too quickly. To prevent such problems, the cabin pressure is reduced to 10.2 psi for a limited time. The Russian spacesuit, like the American, uses a liquid cooling garment to control body temperature. It uses, however, a suit pressure of 5.6 psi and requires the cosmonaut to take a 30 minute prebreath to adjust to the new pressure.

Life support via an American spacesuit relies on three main systems: the Life Support System (LSS), the space suit assembly, and additional supporting equipment. The LSS contains the following:

Primary Life Support Subsystem (PLSS)

The Lithium Hydroxide Cartage

The Display and Control Module (DCM),

The Secondary Oxygen Pack (SOP)


The space suit assembly uses bearings for movement and includes the units listed below:

Helmet/Visor Assembly
Hard Upper Torso (HUT)

Lower Torso Assembly (LTA)

Comm Cap
Liquid Cooling Ventilation Garment (LCVG)
Urine Collection Device/Disposable Absorption Containment Trunk
Thermal Meteoroid Garment (TMG)

The equipment that supports both the Life Support System and the suit assembly includes tools used to repair, maintain, and prepare the suit, astronaut, and manned maneuvering unit for an EVA.

A spacesuit in development is the Command/Control Pressure Suit (CCPS). This design combines the helmet and HUT into a rigid upper torso/helmet. Using a multifaceted structure, the design uses flat panes instead of the current bubble shape. A video/data liquid crystal display mounted in the helmet controls suit functions and runs on voice commands.

Class Discussion

  1. What other problems do people have in surviving the harsh and beautiful environment of space?

  2. Why do you need forced ventilation aboard a space vehicle?

  3. Discuss an overall design for a spacesuit. What are the problems? What kind of material would you use?

Activities and Research

Make a spacesuit designed and built by the class.

a. Discuss an overall design.

b. Decide what major components are important to a space suit

c. Divide the class into groups and assign a component or

components to a group. Have each group design their own version of the item(s) assigned.

d. Have the groups build their designs

e. Have the groups present their designs to the class as if marketing a product at a business meeting.

f. Have the groups attempt to integrate their designs into one whole spacesuit.

g. Discuss the problems with integration of various groups


  1. What are the similarities and differences between a scuba diver and an astronaut, especially concerning decompression sickness? For the values listed in the Table of Atmospheric Conditions, in which atmosphere or atmospheres could a person suffer decompression sickness?

  2. A Soviet cosmonaut was stranded aboard Mir, the Soviet, now Russian, space station during the collapse of the Soviet Union. What kind of spacesuit did he have available aboard Mir?

  3. Research and report to the class on the different spacesuits used by NASA through the years of the space program

  4. Research and report to the class on Russian spacesuits

  5. Compare the number of astronauts who have died in a space-related accident with the total number of astronauts and with the total number of manned launches. Compare the first number with researched calculated probabilities. Is the number of disasters high, or low?


  1. What is the composition of Earth's atmosphere, beyond oxygen and nitrogen gases? What gases are there traces of in the atmosphere? Has the composition of the atmosphere changed significantly over time, according available records? Are there available records?

  2. Convert all pressures listed in the Table of Atmospheric Conditions to atmospheric units. Earth should have a pressure of one atmosphere.

Man-Vehicle Laboratory
MIT Department of Aeronautics and Astronautics
17 March 1997