I am Tom Marshburn, U.S. astronaut and the most recent spacewalker to return to Earth. AMA!

How do you use the bathroom in space?

I knew this question was coming. Answer: carefully. There is a cue card to remind us of the steps. A tube with a funnel is connected to a fan that creates suction to draw fluid (#1) into a system that separates the air from the urine, and then processes the urine to reclaim the water. Yes, that water becomes tomorrow's coffee. Solids (#2) are captured in a similar suction system and contained in a metal can, that is eventually deposited into a cargo vehicle that will deorbit from station and burn up in the atmosphere...to become a shooting star.

I've always wondered what zero gravity feels like. Does it feel like you're falling, but with no wind resistance? Does your blood circulate differently when you're just floating around? Was it difficult to adjust to moving around effectively in space? Thanks for the AMA!

Great insight in your question! Indeed one is in free fall in orbit, so arrival in space feels a lot like the initial second after you jump off a diving board for example. But then the body's fluids stay up around the base of your skull, and your stomach continues to float high up in your abdomen. There's more blood flow to your head the entire time you're in space, and you can feel that and see it in your crewmates (puffy face, bloodshot eyes, etc).
And yes, it can take days to get used to floating and working in space. I felt like a baby deer on ice my first few hours up there.

Who do you think will get to Mars first? NASA, another country, multiple countries together, or a private company like SpaceX?

Going to space is really difficult. The US and Russia are good at it, but humans can still barely pull it off. Going to Mars will be much more difficult, although we've answered the basic questions through space exploration to date. The President challenged us to reach Mars by the 2030s, I hope we stay committed to that goal. Who will get there first? We'll see!

OHHH It's your birthday on coming month, Advance Birthday Wishes from whole of Reddit.

Thanks! Birthday's coming up in about 6 weeks - appreciate that.

Did you get a "woah...I'm in space moment" the first time you went up or does it happen every time?

Also, how did you end up getting into space programs? I am a biomedical engineering student and not really sure how you make the bridge from one field to the other

Life as an astronaut is full of "woah" moments, including the first time you enter the gates at NASA. In space we're very busy, but my first realization was on the space shuttle, cleaning up the cabin in getting ready for our first day in space, when all the suits and seats and helmets were all floating around me. That was moments before my next big "woah" moment went I looked out the window for the first time and saw the electric neon blue arc of Earth's atmosphere.
I became an engineer, then a doctor, and then applied to be an astronaut. So, for now at least, following any STEM (science, technology, engineering, mathematics) field, falling in love with it, and doing your best, is the best path to space.

Was it scarier to go up, or come down?

Scary = fun!!! So, both. Going up in the Soyuz was a bit like the shuttle launch, so I expected the rattling, the enormous invisible hand that pushed us so fast we flattened in our seats and took our breath in sips.
But the ride home in the Soyuz is a wild, crazy ride. We tumble as we approach the atmosphere, we can see the plasma and chunks of flaming heat shield out the window as we incinerate during our reentry, and then feel the spinning and bucking as the chute opens once we're in the upper atmosphere. All capped off with the bang and "car crash" as the Earth rises up to smack into us on the Kazakhstan steppe.

Does it smell like anything in particular inside the airlock immediately following an EVA?

You've probably heard about the "smell of space", which is a strong odor we perceive every time spacewalkers return or a new vehicle has docked to ISS and we open the hatch. I've heard lots of different descriptions, but for me it's a sweet, bacon-y odor. Don't know what it is, but maybe it's the suit material still off-gassing from being out in vacuum.

What do you think the future of space travel is in the next 100 to 200 years.

I think we'll all be able, someday, to buy a ticket to fly into space. Maybe sooner than we expect! If we keep with the current plan, we'll be exploring our neighbors in the solar system, maybe setting up permanent human habitations, mining asteroids for fuel and building materials. We need a breakthrough, though, in propulsion technology and energy production to get humans outside our solar system.

Thank you for this AMA!! I've been waiting forever for an astronaut or employee of NASA to come here. I'm a young redditor who's still in high school. I love space, stars, astronomy, physics, and NASA in general. One day I want to go to space. It's been a dream of mine ever since I was 4. How did you become an astronaut and what tips would you give to aspiring astronomers and astronauts like me? Thank you for your time!

All astronauts will say this, but it's true. Do what you love. Every astro I know gets a gleam in their eye when they talk about what they did before becoming an astro. They loved it, and it showed: they were very good at it! So decide you will be an astronaut today, and start working today at becoming one. Do well in school (= learning how to learn), fall in love with a field and pursue it with a passion. Take care of yourself (we have to be healthy to fly in space). And finally, keep trying. I got into the astronaut corps on my third try!

Hi Tom, thank you for your AMA. You mentioned you are an M.D. . As a student who is studying medicine, I am very interested to know what are the main health concerns for astronauts at ISS, and how do they solve emergency medical cases at ISS, if such thing happens?

Main concerns: atrophy - of muscle, bones, and cardiovascular systems. Exercise takes care of these concerns, both aerobic and resistive exercises. We spend 2.5 hours a day working out up on the ISS. Radiation hits are big up there (solar flares and galactic cosmic rays). Astronauts are radiation workers. In my 5 months in space I received more radiation than most terrestrial radiation workers receive in a career.
We have medical kits and are trained for most any first aid problem - as an MD I could perhaps make more sophisticated diagnoses, but we have limited hardware up there (i.e. no surgery in space). We can stabilize a very ill or injured person for a day or so, and if all else fails we have our Soyuz vehicle as our "ambulance" to get back home for definitive care.

What is the most interesting experiment being conducted on the space station in your opinion and how will it help or change mankind?

That is very difficult to answer. There are so many fields of research going on (130 experiments just while I was up there) on the ISS. Many would say the AMS (Alpha Magnetic Spectrometer), a particle detector attached to the ISS that is collecting data to find the source of dark matter, since that could change our understanding of the fabric of the universe. As an MD I'm partial to the slew of life sciences and medical experiments that push the envelope in how to provide med care to remote areas, and that is cranking out new proteins to generate new medicines and vaccines. I can keep going.....

What's something interesting that isn't very known about living in space?

Compared to living on Earth, easy things are hard, and hard things are easy. It's easy to push a 200-lb object with one finger and float it around, but really hard to tie your shoes or find a place to put your pen. You learn over time how to stabilize yourself to do simple tasks, and how to make use of duct tape and velcro!

How much did Star Trek or any other Sci-Fi Show encourage you to becume an astronaut? And if I may follow up, how is it to live every-ones dream ;)

Many many greetigns from all the way... Switzerland... and of course... live long and prosper

Matthew

The movie 2001: A Space Odyssey was my first introduction to seeing space as wondrous and infinite. I saw the movie when it came out, when I was 7, and I never forgot it. I didn't get serious with the math and science until I was about 13 though.
We pinch ourselves everyday to make sure we're not dreaming in this job. The experience of spaceflight is so unique though, that two days after I returned to Earth, when I was taking out the garbage at home, I looked up at the night sky and asked myself, "did that really just happen?"

What did you miss the most whilst in space?

Family, then a hot cup of coffee that stays in the cup. We have coffee on the ISS, but it's in a closed package (otherwise it would fly out), so you can't get the aroma. A hot shower is a close second. Fresh foods, like a sandwich, with crunchy crusts and crisp lettuce/tomatoes is up there too. But our nation is good at this space-flying endeavor, and life was really pretty good up there.

I have wanted to be an astronaut my whole life, even studying engineering at a major university. But I'm 6'5", any hope? Also why is that stupid rule in place?

One of the benefits of commercial spacecraft builders is that they can open access to space for more people. Also, currently, selection medical criteria are re-evaluated every few years. So definitely keep trying. The physical height limits are in place to protect crewmembers in case they have to use ejection seats (we all fly in high performance aircraft), which work best for a more restrictive height range, and so that crewmembers can fit in the spacecraft. The seats in the Soyuz, for example, actually actuate during landing and lift you up to cushion the impact during landing. Too long a leg length in that case could result in impacting the panel resulting in fractures. So there are pretty good reasons for the restrictions.

Did you see anything in space that was totally shocking or breathtaking you were not expecting when prepping to go to space?

Spaceflight training is very good at preparing us for arriving and living in space. Nevertheless, the experience of floating, trying to doff your spacesuit, and do useful work when you first arrive, while not shocking, is a completely unique experience. Also, no training can prepare one for the view outside the spacecraft during a spacewalk. It takes your breath away.

So, you've earned multiple degrees, became an Astronaut and a Doctor, Do you have any more goals to pursue?

I love my job and would like to stay in it. Still have to pass an annual physical exam though, so we'll see how long I can keep doing it. Would love to fly in space again. Regardless, I'd love to keep on supporting fellow astronauts for their missions - experienced astronauts can teach other astros, provide technical support, etc.
But getting the word out on how special we are as a spacefaring nation, and to encourage others to pursue careers that can help us maintain that expertise, is something I enjoy very much as well.

When conducting an EVA, can any space-borne micro meteorites damage the space suit (hopefully not), or are the spacesuits "bullet-proof"? If the meteorites were able to punch holes in the spacesuit, would it be a serious problem? Thanks Dr Marshburn!

Yes, a hole in a space suit would be a serious problem. It hasn't happened, but could theoretically. We have about 30 minutes of emergency oxygen in reserve in case of a leak in the suit. That would be survivable depending on the size of the leak. Micrometeroids pose a greater problem: they might have enough energy to pass through the suit and the person inside the suit. So we'd have a medical emergency on our hands as well if the victim could get back in.

That is fantastic your also a physician! I am a Registered Nurse, and an emergency room nurse for ten years.

In an emergency, would kind of medical procedures are possible in space? Have you had to do anything medical related in space?

We have the know-how and hardware to start an IV, stop bleeding, splint a fracture, drop an NG or Foley catheter, treat burns, stop nosebleeds (including posterior), treat foreign bodies in the eye, and sew up wounds. We can also perform several runs through ACLS. We have an AED and hardware to intubate and get IO access. Plus an army of medical specialists we can call upon for advice from the ground.
I've performed lots of medical experiments in space, have drawn blood, stopped a nosebleed (my own), and performed few other procedures.

Did you ever have an incident where you almost drifted off into space? How would you go about saving an astronaut that had done so? What do they teach you to do if that happens to you or another astronaut?

I didn't have a moment like that. We train very hard to keep our hands on the handrails, or have our "local tether" attached to the space station. If one were to forget and let go without that tether, we still have a "safety tether" attached back at the airlock that will keep us attached to the station, although we could float far enough away to hit a solar panel or radiator...not good. If that tether breaks, the last resort is a little jetpack we wear on our backpacks during every spacewalk, and we practice flying that jetpack just in case we need to fly ourselves back to the hatch. No other recourse available!

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Actually, i didn't listen to a lot of music up there - I watched movies while working out on the bike or treadmill. My wife kept me up to date with the latest music and had songs uplinked to the station periodically. That plus some classical mixes rounded out the experience.

What has been you favorite part of being an Astronaut? and what is the thing you have disliked the most?

Favorite: flying in space. Close second is the smart, funny, enthusiastic people I get to work with every day. Truly a dream team.
Least favorite: waiting for your assignment. Not a lot of spaceflights these days, until Orion and commercial providers are ready. And then it takes 2.5 years of training to be prepared.