Camping, Camp-out, Sleepover
Life on the ISS:
Sunita Williams' Mission Log
Well, you probably know this last week was EVA week. Lots of last minute preps to get this ready - from charging suit, helmet light, PGT batteries, to scrubbing METOX for CO2
removal, to arranging tools, and reviewing last minute changes to our procedures. The airlock preparations are sort of cool since it involves lots of tools and hardware!
In order to “go out the door” safely we go through a pretty thorough process called pre-breathe. This is the process of flushing all the nitrogen out of our systems by breathing higher concentrations of oxygen. The reason this is important to EVA (spacewalks) is that we operate at a lower pressure than ambient
, in the space suit; about a 4 psi differential from essentially the vacuum of space. As we decrease our overall pressure from ambient, the air bubbles, specifically nitrogen bubbles in the blood, have the potential to expand. This can cause serious pain and other debilitating effects commonly referred to as decompression sickness (DCS) or “the bends.” The diving community knows all about this problem. But the difference with diving is that it would occur as the diver is coming to the surface. The diver can decrease their descent rate, descend to shrink the bubble, or in the worst case get medical attention once at the surface. For us, the problem would occur as we were depressurizing the airlock to open the hatch to go outside as our suit was regulating to maintain the 4 psi differential. That depress rate is set by a pump for the most part, and once we are at vacuum, we can’t get medical care to help us out. So, in this line of work, we need to try and eliminate the occurrence of “the bends” as best we can.
There are 3 methods we use to purge the nitrogen out of our blood to prevent “the bends.” The methods are pretty complicated in reality and a ton of research and data were needed to establish these “protocols.” But, in general they are:
- Pre-breathe - Get in the space suit 4 hours early and hang out breathing 100% O2 before opening the hatch and going outside.
- Exercise - Wearing a mask breathing 100% O2, exercise on the bike for about 15 minutes doing an interval workout using both arms and legs to accelerate that exchange of O2 for air in the blood.
- Camp-out - Sleep overnight in the airlock at a decreased pressure with an increased O2 concentration so that the O2 level in the blood increases as you sleep. Get up in the morning, get on a mask of 100% O2 to re-pressurize to ambient - to use the bathroom one last time before the EVA - and to let 3rd crewperson into the airlock to help us get in the suit.
Picture courtesy of LA - thanks LA!
Image to right: Flight Engineer Suni Williams uses a pistol grip tool as she participates in the first of three spacewalks in nine days. Image credit: NASA
Cool places we have flown over this week:
- “hints” - the cold north!
• The usual - canned fish with cabbage, canned chicken and rice
• Peanut butter and marshmallow cream sandwich on wheat flatbread!!! That was good and reminded me of home. I love marshmallow cream so it was so cool that Dina and Mom packed me an entire jar of it on the Progress. We finally got around to our own packages from the Progress and that is one of my goodies, along with some popcorn jelly beans, Boston Baked Beans (candy), and honey sticks.
- EVA is a bit of a workout…
• 1 x hour on the bike
• 3 x 35 minutes of interval training on the bike to get the heart rate up.
• Run only 2 x 3.5 miles. Surprising how my efficiency on TVIS decreased by missing 3 days in a row…
Things we did: same stuff - ...again...and again...:
• EMU (extravehicular mobility unit - space suit) battery charge
• EMU helmet light battery charge
• Pistol grip tool (EVA power tool) battery charge
• SAFER (Simplified Aid for Emergency Rescue - jet backpack) checkout
• SAFER training - using computer model
• Fluid quick disconnect training (we will be working with ammonia lines outside and this type of fitting is specially made for these lines)
• Ammonia contamination review (we could have a leak manipulating these lines)
• EVA procedures review