I’ve been trying to figure out how fast a person could move inside a space station when essentially they are “swimming” through an atmosphere. Swimmers can apparently go a max of about 1.6m per sec., but that’s a sprinting speed, and everyday movement would be a good deal slower. There’s the added complication that under conditions of weightlessness, one is also, in effect, friction free, thus, one could launch oneself and then only need to use energy to come to a halt, without crashing into a bulkhead too too heavily. To be honest, I’m not even sure there is a question here, but it’s been puzzling me for a while, and I’d be interested in the thoughts of others; by oneself, one tends to get stuck in ruts of thought, like a plough that never turns.
I did several searches on the boards for this question, but nothing popped, hence the fresh thread.
Moving through zero0gee won’;t be like swimming. Water offers more resistance, and you can push ahainst it more effectively. Moreover, water has a surface (on earth), and buoyancy (which is gravity in disguide) keeps pushing you to the surface.
In zero-gee, even in an atmosphere, flapping your arms won’t do much toward changing your velocity, unless maybe you attach big ‘flippers’ to your hands. Air just doesn’t give you much to push against. If you should find yourself in the center of a large open space, far from a wall and with no velocity relative to your container, good luck trying to get to the side.
If you read accounts of life aboard the space stations, or good hard science fiction about life in a weightless environment, you encounter much about handholds, footholds, and the like. Artthur C. Clarke has a character in one book that uses a suction cup arrow to shoot across large spaces. Fortunately, in existing space stations space is at a premium, so you’re never far from a wall or handhold. Some people suggest using an aerosol or other reactive device to move yourself along.
People wrote about using magnetic boots or Velcro (as in 2001) to keep yourself “stuck” to a wall. Skylab used a simpler dodge – special boots with “mushrooms” attached to the soles that could “lock” into a grid on the floor. Unlike magnets or Velcro, you don’t have to work to rip yourself loose – just slide the boots sideways to uncouple.
One unexpected result of living in zero-G was stronger abdominal muscles. People are used to sitting down by letting gtravity pull them down. In zero-G, you have to do the work yourself. It’s like doing sit-ups in zero-G.
Actually, you probably wouldn’t be marooned forever in the middle of a big open space in a well-designed space station. You have to maintain an air flow, to filter and refresh the air. If something got lost on Skylab, the place to look was on nthe air filters – anything lost eventually got swept there.
Experiments have shown that swimmers swim at the same speed in highly viscous liquids as in water-- They tire more quickly in the viscous liquid, but while they’re fresh, the top speed is the same. If this continues to scale all the way to gases, then the speed would be the same there, too… but that’s a pretty big if. You’d also get much lower accelerations, so unless you had a space station much larger than anything we’ve got now, you wouldn’t have a chance to reach top speed.
I wouldn’t be surprised if the most usual injuries to crewmembers of the ISS are wrist and jammed finger type injuries caused by the crew stopping themselves from floating by where they intended to go.
Swimmers also start usually by diving in or by pushing off against a wall - this gives them an initial velocity. They then start their swimming stroke to work against the fluid whcih resists against that initial velocity vector. In 0g, the push off a wall or other fixed object gives the initial velocity, and at such a low speed and with only air as resistance and with such short distances (in a spacecraft of some sort), there’s virtually no deceleration - you just float to your destination. And hopefully you’ve aimed your initial push accurately.
Swimming works as a function of Reynolds number Reynolds number - Wikipedia . A bug “feels” the air about as thick & resistance-ful as a human feels the water. The oft-quoted bit about bees’ flying not being explainable by conventional aerodynamics, to the degree it was ever true, is/was a garbled misstatement of scientific thinking before Reynolds came up with the math to explain how scale matters in fluid dynamics.
A human trying to swim in the air has the opposite problem; the air is too thin to push against effectively.
As explained by the others above, astronauts get from A to B by either a jumping motion then gliding across open air to the target or by hand-over-handing along a surface.
I don’t know about birds, but experiments have been done with flies and bees. The flies went out of control, but the bees managed to develop an entirely different wing motion that enabled them to move smoothly.
No, it was the eminent German aerodynamic Ludwig Prandtl who, in a drunken company, on the back of an envelope, calculated the Reynold’s number for an insect the size, mass and form of the bumble-bee, and (correctly!) concluded that it was far to heavy to glide-fly (which, in fact, it doesn’t!)
There’s not much room in the existing space station. The astronauts learn not to push off too hard from their location or they’ll end up crashing into something. The swimming motions you see in video are just for show, there’s no easy way to suspend themselves in the middle of the limited space, they’ll still be moving in some direction and eventually run into something.
Very well, they won’t have to fight gravity. Penguins in the water appear to be flying and they’re encountering something similar to the 0G sensation found in space, just as a diver in the water with the proper weights will seem to be. However, flying birds may have difficulty orienting themselves or landing in a 0G environment. I wonder if such experiments have been done, the Vomit Comet could be used to investigate that, just toss some birds out into the cabin. I assume that thing gets a thorough cleaning often so a few feathers and birdshit wouldn’t be a big problem.
It might not be that easy. Conceptually speaking you may be on the right track but birds need gravity to orient themselves. They may have difficulty adapting. I think they’re smart enough to eventually adapt, not like the flies that Chronos reported about. Chronos’ post about flies and bees in 0g was pretty cool.
I suspect gravity will be important to many flying birds, but not necessarily all. They have very good eyesight and depth perception, some birds are known for their ‘stunt flying’ ability. I wonder if a Hummingbird would care at all. Can they fly upside down? Maybe Colibri will stop in and tell us something.
The problem I would expect is that ordinarily, birds in flight are exerting a significant downward force. Take away the gravity that’s usually balancing that out, and I’d expect that it would end up flying mostly upwards, instead of forwards. Though most of them probably would eventually learn to compensate.
I think you’re confusing 0G/weightlessness(or microgravity as the case may be) with being in a frictionless environment, but the cases are fairly similar. In theory, an astronaut in the ISS or something else away from the pull of a gravitational body, could ‘swim’, but if they could do it with any real effect, you could do it as well on Earth. You could ‘swim’ and at least notice your body being pulled forward, even if you could easily resist it since gravity and your muscles would keep you firmly planted in one spot.
Try it. Try putting on swim flippers and laying on a rolling chair. You can kick all day and you’re not going anywhere. The coefficient of friction between pretty much anything and air at any speed you can generate by hand (or foot) with out any power just isn’t gonna move that much weight.
But that’s not quite what you asked, the astronauts don’t ‘swim’, they simply push off of one surface and head towards another, then push off of that one and aim for the next one. Watch any one of the ISS videos (there’s tons of them) and you can see them moving about it. All they do is use their legs to push from one place to another and you’ll nearly always notice that they have their arms outstretched as they aim to grab something. Once they’ve pushed off there’s no ‘swimming’ involved.
If they had airplane like wings, they could ‘glide’ and move the surfaces similar to how you could on Earth since there is air* (and thus air friction) in the ISS, but there isn’t a whole lotta space in there for maneuvering. Also, I don’t know how pressurized it is so air friction may be less than what it is down here.
*In space, outside of any kind of capsule, that wouldn’t work at all. You could push off with as hard as you want with a huge piece of flat wood attached to your back (or even a wide open parachute) and it would be the same as pushing off in a ‘diving’ position.
PS. I am willing to bet, given enough speed and a big enough space, if an astronaut had ‘wings’ and they were in a pressurized area they could steer themselves to some extent.
You could move through the air under your own power in weightless conditions. It would be tedious. You would have to be very careful in your form. It would take a long time to get going. You would have a low top speed.
Isaac Asimov described a flying area for people in low gravity. A large area with increased air pressure to make it denser. A set of wing like things attached to your arms. It would work.
Purely under your own power (as opposed to pushing off and ‘steering’) would be very, very difficult since you’d have to ‘swim’ forward, which I think we could probably agree would give you very, very little forward movement, but then you’d have to get your hands back in front of you without moving yourself backwards again. I can think of a few ideas, but most of them end up in a sort of 2 steps forward, 1 step backwards situation.
Keep in mind, the OP is asking about ‘swimming’ not using momentum. In water you move forward by pushing the water behind you/pulling yourself forward. If you want to move forward in a rolling chair without putting your feet in the floor you do all kinds of rocking and swinging, but that’s just using momentum to scoot forwards.
Really, really not very well, so not very well, that I’d worry that any forward movement you got would be negated when you moved your arms back to the front, regardless of you moved/cupped/shaped your hands, they’re just not big enough to impart enough force on something with as much mass as a full grown human. If you had some kind of giant flippers/wings etc, something on your arms to help to give you more surface area with little extra mass, maybe. I doubt even kicking, even with standard SCUBA/snorkeling flippers would get your anywhere.
Remember, the air density (so far as I know, and I could be wrong) in the ISS, is fairly similar to what it is on Earth (maybe less, like being on airplane). So think about what it would take to move you forward down here. It doesn’t take too much imagination to hypothesize whether or not it might work up there. Just flapping your arms and legs, probably not. Attaching some kind of wings that might get you some motion on a rolling chair, maybe.
And again, (because of the wording of the OP), this is in 0G but not in a frictionless environment. Once you’re without any kind of friction, you’re on your own. Someone could give you a little tap and you might as well wave goodbye.
ETA, but yes, ideal world, sure, but it’s not an ideal world. Oddly enough, this is the opposite. Normally when we talk about ‘well this is the real world’ we mean that there is friction, in this case, (IMO, well, in my hypothesis) there’s actually not enough friction to do what the OP wants.
Yup, it’s been done; the brief shot of pigeons in weightlessness starts around 1:10. As you predicted, the birds seem generally disoriented, though if they were up there for long enough they might learn to compensate.