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International Effort Brings an Open Standard For Docking In Space
FTL writes "Engineers from the US, Russia, Japan, Canada and Europe have come together to publish an International Docking Standard for spaceships. Currently the space station has three different types of incompatible docking ports, and the Chinese are developing their own. Standardizing on one type would permit interoperability and facilitate emergency rescues."
The Soviet atmosphere mimicked that of Earths at sea level. 20/80 ratio at 14.7 psi. NASA on the other hand used a pure 100% O2 ratio, so 5psi was all that you needed. And in case you didn't know, your body doesn't need nitrogen as it's an inert gas anyways.
Life is not for the lazy.
"Currently the space station has three different types of incompatible docking ports"
No, it has two. APAS , which is used by Shuttle, and Probe and Cone used by Soyuz, Progress, and ATV.
The third system (CBM) is used by MPLM and HTV, and cannot be docked to. The difference is important - as the docking mechanism can take the full force of an approaching spacecraft, and berthing mechanisms cannot. To berth, one has to station keep with the station, and then be picked up and attached by the station's CANADARM-2 manipulator arm.
The other important difference is size, APAS and Probe and Cone are limited to essentially man sized tunnels. CBM is a full sized door.
The International Docking Standard actually already exists aboard the station - as APAS.
The US used pure oxygen because it meant the spacecraft presure could be less, while still delivering the same amount of O2 to the breather. Lower pressure meant a lighter spacecraft with thiner walls. Also, life support systems could be simpler - they just scrubed everything from the atmosphere that's wasn't oxygen.
Only, on the ground waiting for launch, such a spacecraft would be at atmospheric pressure (to avoid imploding). While 100% O2 at low pressure isn't much of a fire-risk, 100% O2 at atmospheric pressure is a fire-catastrophe waiting to happen, which it duly did with Apollo 1.
They solved the problem on Apollo by having a normal atmosphere on the ground. As the rocked ascended during launch, the concentration of oxygen slowly increaed, with the overall-pressure slowly reduced in step, so the partial pressure of oxygen remained constant. On the shuttle, they went to oxygen-nitrogen. A downside of this is the need to pre-breath oxygen for 24 hours before a spacewalk. Spacesuits operate at the lowest possible pressure and to go straight-outside in one would give you diver's bends. Bends were never a risk on Apollo as there was simply no nitrgen there to cause it.
At 100% O2, the partial pressure of oxygen at 5 psi is actually higher than it is on Earth, so it's quite easy.
Of course, there are other issues with an all-oxygen atmosphere, but breathing isn't one of them. The idea was to reduce the amount of pressure the cabins had to be designed to withstand.
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Unlikely but still factual. What's combustible at 14.7 PSI pure O2 isn't necessarily so at 3 PSI (not 5) pure O2. 3 PSI O2 is roughly the partial-pressure of O2 in air at sea level.
Even so, a lot of people said it was stupid at the time, and the post-Apollo 1 redesign of the vehicle, while not eliminating the pure O2 atmosphere for flight, did eliminate it during ground tests and also eliminated many potential ignition sources and potentially flammable components. (They also redesigned the cabin hatch to open outwards, quickly, rather than inwards -- increasing the risk of a possible blow-out but enabling for quick escape in the case of another fire.)
Redesigning Apollo to use a sea-level-like air mix would have made it too heavy to get to the Moon on the existing Saturn V.
Mind, as a resident of the Denver area and knowing that there are plenty of people living at even greater altitudes, I'm a little surprised they opted for 14.7 PSI for Shuttle when ~12 PSI works just fine. Commercial airliners pressurize the cabin to = 8000 feet, typically ~7000 feet or about 11.5 PSI, but you start running into issues with avionics cooling, comfort, and extreme exertion if you beyond that.
-- Alastair
Helium, neon, argon,krypton, xenon and radon are noble gasses. Nitrogen is an inert gas. http://en.wikipedia.org/wiki/Inert_gas
Nitric acid is not nitrogen gas. Neither are organic nitrates. I am very sorry for someone who confuses nitrogen gas and nitroglycerine.
Not those of us who played the original BBC version. :P
Waste of money anyway. Aim halfway between the planet and the station, then look out of the side window till you're lined up right, and then it's just a case of matching your rotation as you fly right in. Simple.