The Design and Functionality Behind the Apollo Pressure Helmet

The Apollo pressure helmet, a key component of the astronauts' advanced spacesuit, was designed with an extra amount of headroom that might initially appear unnecessary. However, this extra space played a crucial role in ensuring the astronauts' safety, comfort, and operational effectiveness during their missions. In this article, we delve into the reasons behind the design of the Apollo pressure helmet and its critical functions.

Why the Apollo Pressure Helmet Required Extra Headroom

The Apollo pressure helmet was designed with extra headroom for several important reasons, as illustrated in the following sections.

Comfort and Fit

Astronauts wore various layers of clothing, communication gear, and other equipment underneath the helmet. The extra space allowed for a more comfortable fit, accommodating different head sizes and shapes. This design ensured a more secure and less painful seal, which is essential for maintaining internal pressure and preventing leaks.

Movement and Mobility

The additional headroom provided astronauts with better head movement, which was crucial for tasks that required them to look around or manipulate controls and instruments. This mobility allowed astronauts to perform delicate maneuvers and achieve precise control over various systems, enhancing their operational effectiveness.

Pressure Regulation

The helmet needed to maintain a stable internal pressure while allowing for some movement. The extra space helped to manage pressure changes, especially during launch and re-entry, where rapid changes in pressure could occur. This design feature was critical for maintaining the integrity of the helmet and ensuring the safety of the astronauts during these critical phases of the mission.

Safety and Functionality

In the event of an emergency, having more space in the helmet facilitated easier donning and doffing of the helmet or provided a buffer against impacts or other hazards. This design feature allowed astronauts to quickly adapt to dangerous situations and maintain their safety.

Thermal and Ventilation Considerations

The design of the Apollo pressure helmet allowed for better airflow and thermal regulation within the helmet, which was essential for keeping the astronauts comfortable during missions, particularly during extravehicular activities (EVAs). Effective thermal management ensured that the astronauts did not overheat or become too cold, further enhancing their comfort and safety.

Understanding Spacesuits and the Unique Challenges of Extravehicular Activities (EVAs)

To explore and work in space, human beings must take their environment with them because there is no atmospheric pressure and no oxygen to sustain life. Inside the spacecraft, the atmosphere can be controlled, so special clothing is not needed, but when outside, humans need the protection of a spacesuit.

The Earth's Atmosphere and Its Composition

The Earth's atmosphere is approximately 20 percent oxygen and 80 percent nitrogen from sea level to about 75 miles up. This composition provides the necessary oxygen and reduces the risk of hypoxia. As altitude increases, the density of the atmosphere decreases, and at 18,000 feet, the atmosphere is only half as dense as it is on the ground.

High Altitudes and the Need for Spacesuits

Above 40,000 feet, air is so thin and the amount of oxygen so small that pressure oxygen masks no longer do the job. The threshold at 63,000 feet is critical, where humans must wear spacesuits that supply oxygen for breathing and maintain a pressure around the body to keep body fluids in the liquid state. At this altitude, the total air pressure is no longer sufficient to keep body fluids from boiling.

Pressurized Spacesuits and Oxygen Supplies

The spacesuits designed for the space shuttle era are pressurized at 4.3 pounds per square inch (psi), but because the gas in the suit is 100 percent oxygen, instead of 20 percent, the person in a spacesuit actually has more oxygen to breathe than is available at an altitude of 10,000 feet or even at sea level without the spacesuit.

The Critical Pre-Breathing Period

Before leaving the space shuttle to perform tasks in space, an astronaut has to spend several hours breathing pure oxygen before proceeding into space. This procedure is necessary to remove dissolved nitrogen in the body fluids and prevent its release as gas bubbles when pressure is reduced, which is commonly called Decompression Sickness.

Spacesuits for the Space Station Era

The next generation of spacesuits, designed for the space station era, will be pressurized to 8.3 psi, resulting in a shorter or even non-existent pre-breathing period. This design will provide astronauts with greater comfort and improved operational efficiency.

Protection from Micrometeoroids and Temperature Extremes

The spacesuit also provides crucial protection. Besides shielding the astronaut from micrometeoroids, the spacesuit insulates the wearer from the extreme temperature variations of space. On the side of the suit facing the Sun, temperatures can reach up to 250 degrees Fahrenheit, while the other side can drop to -250 degrees Fahrenheit due to the absence of the Earth's atmosphere to filter the sunlight.

Conclusion

The design of the Apollo pressure helmet and the spacesuits in general reflect the ingenuity of space engineers, ensuring that astronauts can operate in an environment hostile to human life. The extra headroom in the helmet is just one of many thoughtful design elements that contribute to the overall safety and effectiveness of these critical life-support systems.