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Smooth, 6.5 Hour Spacewalk To Fix ISS Ammonia Pump
The ISS crew can breathe a little easier now; the NY Times reports that the ammonia pump repair that the station has needed has now been partly completed, and in less time than expected. More work is scheduled, but, says The Times:
"The astronauts, Col. Michael S. Hopkins of the Air Force and Richard A. Mastracchio, were far ahead of schedule throughout the spacewalk as they detached tubing and electrical connectors from the pump. They were able to remove the 780-pound module and move it to a temporary storage location, a task that had been scheduled for a second spacewalk on Monday. ... Colonel Hopkins and Mr. Mastracchio stepped out of an airlock at 7:01 a.m. Eastern time, and even though they accomplished more than they had set out to do, they were able to return at 12:29 p.m., an hour earlier than had been scheduled. The two encountered few complications."
Ars Technica has video, too.
As everyone knows, all projects involve several trips to Home Depot for the odd tool or bolt that was overlooked in the initial planning stage.
Have gnu, will travel.
First, the pound is a unit of mass as well as a unit of force, thanks to our archaic English unit system. You can keep them apart by using pounds-force (lbf) and pounds-mass (lbm).
Second, the effect of gravity at the height of the ISS is about 88% of what it is at sea level. If it has a mass of 780 lbm, the gravitational force on it will be 689 lbf.
This is low earth orbit, not the moon.
If you're walking in space and its bumpy then you have a big problem
What counts as the start and end point of an EVA varies depending on what Agency is reporting it and who wrote the press release. The start can be anything from the start of decompression, reaching vacuum, opening the hatch or stepping outside, and the end stepping back in, closing the hatch, starting recompression or returning to atmospheric pressure in the airlock. In this case it's 5.5 hours outside, but there will have been more time spent inside but in vacuum at the start checking the suits are working properly (especially after the water leak last time) and at the end making sure there's no ammonia been brought back inside.
I know it's a nitpick, but isn't 7:01 a.m. - 12:29 p.m. more like 5.5 hours? I understand that they were an hour faster than planned (meaning they planned 6.5 hours) but the title seems a bit off nonetheless...
Considering the ISS orbits the earth about every 90 minutes, it was more like 3 days and an hour.
Nickpick +5
The space station travels at roughly 17,500 MPH. They're working in (this is per the folks that make the suits) anywhere from -100F to +235F. Good job guys. It really takes a lot of people to crunch numbers and possibilities of failure, what to do if failure occurs, and how to do all of this within certain time restrictions. If mankind can claim any sort of technical achievements (I know most here would like to boast their computer skillz), this, in my mind, is a fine example of folks working together at far distances, and through many challenges. Bravo guys and gals!
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Adespoton is spot on. No gravitational force can be detected when in "free fall" which is what space orbit is. Even as gravity may grab you and accelerate you towards a large mass, there is no bodily sensation whatsoever. Every molecule of the bodily is (almost) identically effected. There is nothing to cue the brain that gravity is pulling you, even as you may change direction as a result of it. Very difficult for most people to understand this who are used to feeling earth under there feet, air against their skin, and visual references all around.
The heat sink in your computer would be pretty miserable at dumping waste heat into space. Terrestrial heat sinks typically heat into a fluid, such as the air that your computer's fans blow across the heat sink.
Problem: there is no air (or anything else into which heat may be transferred) in space. Radiative cooling - that is to say, releasing infrared radiation - does occur, but it is *far* slower that conductive cooling. To do that effectively, though, you want a big, hot surface area that is shadowed from all other heat sources in the region (that big fusion reactor the Earth orbits counts as "in the region" here).
To cool an artificial satellite effectively, especially a big one like ISS, you use a heat transfer system (in this case, they apparently use ammonia) to concentrate the heat into radiative cooling surfaces on the shadowed side of the station. This system definitely adds complexity, not to mention generating a bit of heat itself(entropy always increases), but without it, the side of the station facing the sun would cook, and the shadowed side wouldn't get hot enough for effective radiative cooling.
There's no place I could be, since I've found Serenity...
....while in orbit, where they don't feel the effects of gravity?
They don't feel the effects of gravity, but they very much feel the effects of inertia.
In this context (i.e., earth orbit) the 780 lbs of the module refers to mass rather than weight. If the module were drifting and they had to stop it by grabbing it while they were connected to the ISS, you can bet they'd feel the effects of inertia. For the two-dimensional analogy, imagine a refrigerator, sliding on a perfectly slippery ice rink.
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