To prepare for a spacewalk, crewmembers must do the following:
- Reduce the pressure in the shuttle to 0.7 atm and increase the oxygen
- Pre-breathe 100 percent oxygen for 30 minutes to remove nitrogen from their blood and tissues
- Put on the MAG
- Enter the airlock
- Put on the LCVG
- Attach the EEH to the HUT
- Attach the DCM to the HUT (PLSS is pre-attached to the HUT)
- Attach the arms to the HUT
- Rub the helmet with anti-fog compound
- Place a wrist mirror and checklist on the sleeves
- Insert a food bar and water-filled IDB inside the HUT
- Check the lights and TV cameras on the EVA
- Place the EVA over the helmet
- Connect the CCA to the EEH
- Step into the LTA and pull it above their waist
- Plug the SCU into the DCM and into the shuttle
- Squirm into the upper torso portion of the suit
- Attach the cooling tubes of the LVCG to the PLSS
- Attach the EEH electrical connections to the PLSS
- Lock the LTA to the HUT
- Put on the CCA and eyeglasses (if the astronaut wears them)
- Put on comfort gloves
- Lock on the helmet and EVA
- Lock on the outer gloves
- Check the EMU for leaks by increasing the pressure to 0.20 atm above the airlock pressure
No leaks mean the airlock is depressurized. Once these steps are completed:
- The EMU automatically depressurizes to its operating pressure.
- The suits are tethered to the airlock.
- The outer airlock door is opened.
- The SCU is disconnected from the EMU.
- The astronauts step out of the airlock into the shuttle's cargo bay.
And the spacewalk begins. At this point, the EMU is a spacecraft in and of itself, independent of the shuttle/space station. This is why each EMU has a $12 million price tag. After the spacewalk, these steps are reversed to get out of the suit and back into the spacecraft.
When working on the moon, Apollo astronauts had difficulties moving around in their space suits. The Apollo suits were not nearly as flexible as the EMU used today; however, the EMU weighs almost twice as much as the Apollo suit (not a problem because the EMU was designed for work in microgravity, not on a planet's surface). For future space missions to Mars, NASA is developing "hard suits" that are more flexible, more durable, lighter-weight and easier to don than current space suits.
For more information on space suits and related topics, check out the links on the next page.