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."

Comments

Atmosphere

[FTL]

Docking of course is just the first step. One also needs agreement on the atmosphere. American spacecraft (Apollo, Skylab) used 100% oxygen at 5 psi. Soviet spacecraft (Soyuz, Salut, Mir) used 20% oxygen 80% nitrogen at 14.7 psi. Neither side could change this easilly. Thus even though Apollo and Soyuz were able to physically dock in 1975, they had to use an airlock between the two spacecraft. Otherwise the cosmonauts would have gotten the bends from decompression and Apollo could have ruptured from overpressure.

Fortunately this is no longer much of an issue. As a result of the Apollo 1 fire and the deaths of Grissom, White and Chaffee, American spacecraft (starting with the Space Shuttle) adopted the Soviet approach.

Re:Atmosphere

[Lord_of_the_nerf]

I also hear the Americans like Magic Carpet Ride by Steppenwolf playing when they open the doors, whereas the Soviets are more inclined to Tchaikovsky.

Re:Atmosphere

[DigiShaman]

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.

Re:Atmosphere

[Catmeat]

Not exactly.... Apollo 1 was about 8 years beforeApollo-Soyuz. They kept flying with 100% oxygen until the Shuttle era.

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.

Re:Atmosphere

[AdmiralXyz]

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.

Re:Atmosphere

[Anonymous Coward]

I'm always going to prefer the Blue Danube Waltz while docking..... if for no other reason than nostalgia. Who remembers the docking computers in the C64 version of Elite?

Re:Atmosphere

[MichaelSmith]

Besides the point though, as people have done Everest without oxygen anyways, right?

Only acclimatising for a long time. The natural atmosphere at that altitude is only marginally survivable. If you dump the atmosphere from a 747 at 30000 feet most people would die quickly.

Re:Atmosphere

[MichaelSmith]

Operating at 5psi makes eva much easier. Lunary surface EVAs would not really have been possible on the moon if the crew had to decompress for three hours every day. They were busy enough anyway.

Re:Atmosphere

[AJWM]

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.

Re:Atmosphere

[kent_eh]

I've been wondering why we don't use an oxy-helium combination, actually. Does anyone know?

Might have something to do with this

Re:Atmosphere

[Anonymous Coward]

N2 is rather inert, and (along with high-quality flue gas, the noble gasses, and various N2/noble gas mixtures) is often referred to as an "inert gas". Perhaps you're confusing "inert gas" with "noble gas", or perhaps you slept through high school chemistry.

Re:Atmosphere

[ceoyoyo]

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.

Re:Atmosphere

[ceoyoyo]

Why would you? Oxy-helium is used in high pressure environments where nitrogen becomes a narcotic. In a space ship the last thing you want is high pressure.

Helium is kind of a pain too. It tends to leak through seals a lot faster than other gasses.

Re:Atmosphere

[Anonymous Coward]

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.

Only true for US spacesuits. The russian suits use a higher pressure and need only a short prebreathing period (30 minutes).

Re:Atmosphere

[hcdejong]

Because Mission Control would have a hard time keeping a straight face due to the Chipmunk effect?

Re:Atmosphere

[Haeleth]

Who remembers the docking computers in the C64 version of Elite?

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.

Re:Atmosphere

[petermgreen]

Afaict the big issue with a pure O2 atmosphere in an earthed launch spacecraft is the launch and reentry.

If you launch and reenter on low pressure pure oxygen then you have to design your cabin to resist pressure in both directions.

If you launch and reenter on atmospheric pressure (afaict this is what apollo did) pure oxygen then you have an atmosphere during launch and reentry that is a massive fire risk.

If you launch and reenter on an oxygen/nitrogen mix then your gas handling just got a whole lot more complicated.

Imagine

[MrEricSir]

Imagine if *humans* didn't have standard docking ports.

"Hey babe, you in the mood?"
"Yes, but you have a TR-71 and I have a OML 3.0. We'll need to go to HumanShack and get a converter first."
"Eh... never mind, let's just watch TV instead."

Re:In Communist China...

[Anonymous Coward]

Open standards are a terrible way to go about this docking in space crap. What if someone finds an exploit to the docking procedure and is able to copy these docking procedures elsewhere?

What about the engineers that came up with these standards? Why don't they get to benefit from their work by patenting them?

Re:In Communist China...

[digitig]

More likely, somebody will produce a proprietary "enhanced" version of the docking standard and claim that it is now the de-facto standard, and start charging fees to anybody who tries to dock with it.

Not true

[DerekLyons]

"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.

Re:It's about time

[cmowire]

It was.

This is fairly similar to the APAS docking adapter they created for the Apollo-Soyuz test program in the 70s.

Now... why the ISS doesn't use APAS for all links and why the ISPRs (international standard payload racks) that everything in the US section is contained within won't fit inside an APAS docking tunnel... well... heh heh.

Watch the polarity guys

[Yvan256]

Better build diode bridges into every connection! You wouldn't want an astronaut from the opposite side of the sun to try and dock with the ISS to cause a polarity inversion!

Hurry...

[Snufu]

Microsoft is greasing palms to fastrack their open docking standard, dockx.

Re:In Communist China...

[cinderellamanson]

http://en.wikipedia.org/wiki/Space_law I think I will go to school to become a space lawyer.