Just thinking about how sometimes an approaching deadline makes me piss my pants, I have the utmost respect for these people, who live and work under the highest pressure, out there, alone in the void helpless, if something goes really wrong. Only one small piece of their gear malfunctions and they are done.
And then I'm thinking about the complexity of all the systems they are supported and kept alive by. I couldn't probably help but constantly be thinking that with a huge human-designed system like that, something is always bound to go wrong and that I would probably die in a few minutes because of some obscure equipment failure.
And yet, there he is, floating around, keeping it cool, just doing his stuff in that floating cable jungle, swinging that razor sharp knife around like he isn't a knife cut away from eternity. I will try to keep this image in mind next time when my cables get tangled.
Actually if I were up there I'd be more worried about the lack of pressure, I saw the opportunity and couldn't resists on a more serious note though.
Agreed, I know a couple submariners who told me they'd tie a string from one side of the room to the other. As they dove the string would begin to droop and loose tension, a lot of tension.
Makes my head spin just thinking about the possibilities, which I'd be doing if I were down there...
> Actually if I were up there I'd be more worried about the lack of pressure
Interesting you should mention that. I learned a few days ago that while the ISS at large is kept at 1ATM, the spacesuits they use for spacewalks are only pressurized to a fraction of that (if you pressurize a suit too much, it becomes too balloon-like to easily move). Because of this astronauts/cosmonauts have to spend several hours before each space-walk breathing pure oxygen so that they don't get the bends.
That degree of preparation before every spacewalk would disturb me to some extra degree I think. If there was a problem, it's not like somebody else could just hop into another suit and come help you.
There are several different "pre-breathe protocols" used prior to US spacewalks to avoid the bends. Some involve taking the airlock down to 10.2 psi (as opposed to 14.7 psi for 1 ATM) and sleeping there overnight. Also the crew may hang out in the suit while still in the space station for several hours before the spacewalk. The suit is pressurized with pure oxygen and is at a 4.3 psi.
All of this does make for a long day. Even though the spacewalk may only be 6 or 7 hours, entire day with preparations and clean up afterwards is exhausting.
Are nighttime space-walks common? I'd imagine you'd want to schedule them when you have sunlight to avoid any unnecessary complications. I mean their schedule each day is jam packed, but I'd imagine it wouldn't be too much trouble to schedule around nighttime?
EDIT: Duh, orbit is much faster than a 24-hour day...
Depending upon the Beta Angle [1], the spacewalk could be in sunlight the entire time (though that's rare). It could be in darkness up to about 50% of the time.
They are in low-Earth orbit. Each orbit only takes about 90 minutes, and half of each is daytime and half is night. Since space walks are typically several hours long, they are typically half in night and half in daylight.
the oribital period of the ISS is 92 minutes 50 seconds. Therefore they do not experience a 24 hour day cycle as we do here on Earth. So the term "nighttime" doesn't have the same meaning. However there are orbits that are more heliosynchronous than others providing more solar time. At this moment it seems that the ISS is in an pass that is more than 50% solar time as can be seen on sites such as this one: http://iss.astroviewer.net/.
I never realized how time consuming it was to deal with all your cables. I'd love to know the purpose of the color coding scheme on their different cables, but couldn't find anything with a quick search. I'm assuming different weights?
Well they seem to be hooked to the ISS rails with a blue cable. The orange one seems to be hooked to one of their blue ones and also the the rail. This looks amazing!
The Russian Orlan suit [1] is pressurized higher than the US EMU [2], and gloves are not as dexterous. I don't know a lot about Russian spacewalks, but US gloves have caused fingernail delamination in many people, including myself (I'm not an astronaut, but I work with this hardware a lot).
Is it possible to receive a Russian transmission? I speak Russian and so the interpreter is only ruining it for me because I hear too many people talking.
I turned off the feed, but I kept hearing a lady with a distinctive Russian accent speaking English, so I suppose that it's the other way around. Although maybe that's just for the spectator feed.
Edit: I listened to it again. The Russian communications are between two cosmonauts. One is most likely inside the ISS and the other is walking. The interpreter is translating their Russian communication to English.
I just heard a voice-over mention: "...setting up all their hardware for the beginning of the installation of the Obstanovka experiment that will study plasma waves".
I can't speak for Russian EVAs [1], but in US EVAs we always have a long tether reel attaching us to station. If we need to get further than that tether reel allows, we attach another tether reel before releasing the first. Additionally, we have a sort of jetpack called a SAFER [2] in case a tether (or the user) fails.
I am shocked to see that NASA still uses analog video transmission systems! (I can tell because of the type of visible video artifacts: discoloration, etc).
Elon Musk is right when he says government-funded space research programs are stuck using decades old technologies due to inertia, conservatism, and lack of competition.
I'm shocked at how high quality the video is. It's being beamed from outer space, and I can watch in practically real time. Who cares if it's analog or digital? It works, and it's awesome.
I don't want NASA messing with the latest technology just for shits and giggles. Don't fix what ain't broken.
I can watch much higher quality videos streamed over the Internet, from servers thousands of miles away, around the world, through many routers, fiber optics, and complex technological stacks (DOCSIS, TCP/IP, fiber optics signal modulation, video codecs, etc).
Yet the ISS has a clear line of sight to ground receiving stations 230-1000 miles away (or to satellites which are perfectly able to transmit digital data), yet the video signal quality is that bad?
Don't get me wrong. As a space enthusiast I love being able to watch live spacewalks. But as an engineer I sigh at certain technical aspects...
Both you and the servers you're pulling the content from are stationary on the ground, and any satellites used are in geosynchronous orbit. ISS is travelling 17000 mph. So while it may have clear line of sight to a ground station in New Mexico one minute, the next minute that same line of sight is in Texas.
Also, for a spacewalk the video source is from a space suit, so the video signal is sent wirelessly from the spacesuit to ISS, then sent to a TDRS satellite, then to the ground. The spacesuit camera is admittedly not as good as I'd like it to be, but considering all the architecture supporting it started being put in orbit over 10 years ago, and was designed before that, it's pretty good.
That's cool did you directly work on any of the systems?
I have been poking around the NSTS 07700 Volume X Book 1 Flight and Ground Specification. The EVA, and Video subsystems are highlighted there.
As an engineer, you should know that engineering involves designing systems that will get the job done with the minimal amount of resources possible.
What would be the point of a higher quality video in this context? Is it necessary, or simply a nice-to-have?
One of the most popular axioms of engineering is "if it ain't broke, don't fix it." It could be revised for this scenario: "if it gets the job done, don't improve it."
Sure, if you want to spend the money to add (more) redundant links. You want to front a few thousand dollars?
Unless you mean that digital links aren't more vulnerable to radiation, in which case I recommend you read up on large-scale analog circuitry and get back to me.
Wait for SpaceX or somebody else to bring the per-kg cost down and we'll have all the digital video anyone could ever want.
You seem to be arguing rad-resistance is the factor that made them decide on analog instead of digital video.
I doubt it.
Like someone said, initially they chose analog because back in the day nobody did digital video streaming. It has worked okay since then. And there just hasn't been enough reasons to justify a change to digital.
