Humans in Space

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

Artificial Atmospheres

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

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)

• a self-contained portable life support backpack mounted on the hard upper torso (HUT) section of the spacesuit
• contains everything necessary to maintain life and communication.

The Lithium Hydroxide Cartage

• removes contaminates and carbon dioxide from ventilation gases.

The Display and Control Module (DCM),

• mounted on the front of the HUT, it provides easy access to suit controls.

The Secondary Oxygen Pack (SOP)

• a thirty minute emergency oxygen supply

Battery

• powers the electrical systems stored in the PLSS; easily replaceable.

Helmet/Visor Assembly

• Made of polycarbonate material, it protects against radiation and controls the direction of ventilation.
• It connects to the HUT and has mounting brackets for lights and cameras.

Hard Upper Torso (HUT)

• Of fiberglass construction, it provides for mounting all components of the extravehicular mobility unit.

Lower Torso Assembly (LTA)

• Lower body seal closure pants and boots, with a polyurethane bladder for pressure maintenance
• permits joint movements and rotation

Gloves

• protects the astronaut's hands and is jointed

• gives crew member enough dexterity to work with tools

Arms

• connects to HUT and gloves; has elbow joint for flexibility

Comm Cap

• fabric cap fitted with a microphone and earphone to permit communication

Liquid Cooling Ventilation Garment (LCVG)

• A jump suit containing water cooling tubes to keep body temperatures level

Urine Collection Device/Disposable Absorption Containment Trunk

• absorbs urine to keep skin dry, single use and disposable
• available for both the male and female astronaut.

Thermal Meteoroid Garment (TMG)

• consisting of several layers, the innermost layer is made of neoprene-coated rip-stop nylon for puncture and tear protection

• the middle layers are thermal insulators made of aluminum mylar

• the outer layer, made of a woven blend of Kevlar and nomex synthetic fibers, is white to reflect sunlight and teflon-coated to say clean; especially resistant to tears, punctures, and abrasions.

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.

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?

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

Research

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?

Problems

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.