I worked as a Flight Crew Systems engineer for Lockheed Space Ops and then United Space Alliance, supporting over a hundred missions. Because some of my group took turns being sent to Edwards in case of a landing there, while the rest stayed at KSC, I supported roughly about half that number of landings.

Like aboard a submarine, the crew is not acutely aware of the background “human odor” which accumulates over missions lasting up to two weeks. The strong or recent odors you are of course aware of, but eventually it gradually becomes olfactory white noise. And as mentioned elsewhere, odors from the WCS (waste containment system) and its trash locker are vented overboard. Same for the underfloor Volume F trash locker.

There was another large locker, Volume B, mounted on the aft starboard middeck wall used for dry (non-stinky) trash, like paper, clothing bags, or misc items.

Not to tell stories on my beloved astronauts, but many become motion-sick (space adaptation syndrome) early in their missions. Oddly enough, a pilot astronaut with 6000 hours of jet experience runs about the same prevalence of SAS as a university researcher Payload Specialist – go figure!

The used “emesis” bags are sealed and placed into the WCS and underfloor trash lockers, along with food waste, Maximum Absorption Garments, and other so-called “wet trash”. MAGs are double-stuffed adult diapers used for launch-and-entry, spacewalks or if the WCS (forgive me) “craps out” during the mission. All this trash is vented overboard through the ECLSS system, so most of the odor goes with it. Not so once the Orbiter returns to the atmosphere, however.

Compounding matters, biological activity continues throughout the duration of the mission inside the sealed emesis bags, MAGs, and discarded food bags, and the gas produced can cause them to rupture. Ever forget to take your trash out while on a two-week vacation?

But there’s more. The g-forces of reentry tend to pull fluids away from the head, which can induce nausea via a vestibular system adapted to microgravity. Some of us have experienced similar temporary sensations from standing-up too fast. Later-on, we used recumbent (lie flat) seating for ISS return crew, but the others sat upright. And although astronauts try to load-up prior to reentry with oral hydration electrolytes, it doesn’t always prevent this effect, resulting in more emesis bag usage. Hopefully the bag makes it up where it needs to be in the nick of time (‘nuff said on that), but if not, then there may be some “uncontained material” to deal with once on the runway.

Once the hatch is open post-landing, the ASPs (astronaut support personnel – who are themselves astronauts) enter the crew module to help the crew unstrap, remove O2/comm cables and hoses, and stow helmets and other gear. They will perform/assist with any clean-up required. An external purge (air conditioning) hose is brought through the hatch, and the crew module air is gradually exchanged with conditioned outside air.

Once ready, the four crewmembers on the flight deck are assisted down the ladder to the middeck, and then the entire crew is assisted with egress from the Orbiter. Early in the program, the crews descended the white room steps when they felt ready, but later on we used the Crew Transfer Vehicle (essentially a modified “people mover” like at Boston Logan airport) which allowed the crew to walk across from the whiteroom to the CTV without doffing their bulky orange launch-and-entry suits. Sometimes they required assistance, but often not.

Once in the CTV each crewmember received whatever assistance was required doffing their cumbersome LES, maybe underwent some quick medical tests, and after some time to get their “land legs”, donned their ubiquitous blue flight coveralls for the traditional walk-around.

Once the crew departed the Orbiter, then us FCS and payload/experiment folks were free to enter and begin work. I can best describe the smell as being similar to a four-day Greyhound bus trip that my high school band took across the country. Sort of a human/disinfectant odor – not terrible, but definitely noticeable.

But the cool purge air carried (most of) that odor away fortunately.

Besides time-critical destowage and removal of experiments, our team had 3–4 hours at most to get as much as we could out of the crew module prior to Orbiter tow. Months of planning and procedures went into that carefully choreographed ballet, because it all had to come off in a certain order.

Eventually, it was time to remove the wet trash locker contents from the WCS and underneath the middeck floor. The WCS bags were fairly easy, but the underfloor bag was like THE biggest lawn trash bag you ever saw, made of a thick heavy plastic, and encased in a liner. We had to disconnect the mouth of the bag from the receptacle opening in the floor and then tape it SECURELY shut with aerospace duct tape. I realized the hard way once why that last step was so important.

Although as the engineer I was supposed to let my techs do the work, still I felt I should pitch-in and help with the more unpleasant tasks; this one being about the worst. So I took hold of the neck of that wet-trash bag and heaved mightily upward, whereupon the duct tape pulled-off and my hands plunged deep into the wet, dank, smelly interior – full of split-open “barf bags” from flight day one, used diapers, and spoiled food waste! And I hadn’t thought to don gloves first, since this wasn’t supposed to be my job! I managed to make it out into the white room, grab a spare ziplock, and fill it with my breakfast. We had no wet-wipes, towels, or anything on hand, so I went down the stairs onto the runway and off where a flatbed trailer of port-o-lets was staged for the recovery team’s use. Lots of toilet paper and a bottle of water later, I was ready to continue. (From then on I made sure we had a good supply of gloves and clean-up materials in our truck.)

One good thing about that experience – the smell never bothered me nearly so much after that mission!