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Suitports seem like a brilliant idea that saves lots of mass and complexity compared to an airlock, which traditionally is a dumb pressurizable gas wasting tube where the astronaut suits up. The first EVA was made using a bag as airlock. Orion is said to be able to depressurize and repressurize once. Dragon2 and CST-100 can't even do that.

Why not put four or more suitports on the outside of the upper part of the spacecraft, and launch it with fairings through the atmosphere? The Orion has a side door already anyway, why not turn it into a suitport? Could be discarded before re-entry.

suitport diagram

suitport separating

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Using EVA Suitports on spacefaring vessels has been thought of before. For example, Inflatable Mission Module (PDF) envisioned by Tony Sang and Gary Spexarth in 2010, discusses the use of an inflatable accommodation module that would include AR&D (Autonomous Rendezvous and Docking), ECLSS (Environmental Control and Life Support System), EVA suitport, and other interfaces. This proposal was never funded though, but it certainly appears achievable.

There are some limitations to using EVA Suitports though. Spacesuits themselves would still have to be shielded when not in use to protect them from radiation damage, thermal cycling, micrometeorites and so on, and you'd require the ability to retract them back into the pressurized vehicle for pre-EVA and post-EVA inspection, be able to change at least gloves that wear out and suffer punctures the most. Otherwise yes, you could be able to save breathable air and nitrogen used for purging by having a Suitport installed on the vehicle.

Orion isn't meant to be used on its own anyway, except for short-duration missions that don't include EVA at all. It will be used together with various service and habitation modules, so latter could, in theory, also include EVA Suitports. But they wouldn't be used on Orion crew module, or MPCV (Multi-Purpose Crew Vehicle). Since you'd require some manipulation space also inside the vehicle, MPCV is simply too small for that, and adding even more interfaces would further complicate its design.

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  • $\begingroup$ Retracting the suits into the habitat would negate most advantages! That cannot be the design goal. Inspecting the suit from the inside should be good enough. At least less dangerous than evacuating the entire Orion and hoping that it will be re-gassed as planned after the EVA astronauts have returned. And Orion is said to have 3 weeks of life support, and is suggested to visit a captured mini-asteroid with an EVA. Orion is called a "crew exploration vehicle" for as many as 7, and if EVA's aren't routinely available for them, then the whole idea is discounted. $\endgroup$ – LocalFluff May 2 '15 at 13:35
  • $\begingroup$ @LocalFluff No, it wouldn't. Think about how much space an empty EVA suit takes, and how much space it needs with an astronaut in it. We're talking about the difference in volume of free air between a filled cabinet and a mostly empty small room here. So somewhere in the order of 100 times less air needed to retrieve a Suitport installed EVA suit than if it comes in from a conventional airlock design. Orion MPCV will only fly on its own + ESA built service module uncrewed around the Moon. Crewed missions will include a habitation module, and/or dock with ISS that has the Quest airlock. $\endgroup$ – TildalWave May 2 '15 at 13:39
  • $\begingroup$ I didn't get your point there, TidalWave. If the suitport is outside of the spacecraft, and shielded from launch aerodynamics, its volume doesn't really matter. It would anyway be only about 0.1 mˆ3. Any farmer keeps his stinking dirty boots outdoors, doesn't drag them indoors. And retracting toxic dust from some explored object doesn't seem to be an advantage either. $\endgroup$ – LocalFluff May 2 '15 at 13:52
  • $\begingroup$ OK, let's see; Suitport, egress: Remove outer cover, fill the suit with air & test for leaks, remove inner cover, climb in, close suit's hatch, egress. Ingress: Attach to the port, open suit's hatch, climb out of the suit, close inner cover, let the suit "bake out" to remove any contaminants, deflate the suit, close outer cover. You only lost the air that fills the suit. Inspection: Open inner cover while the outer cover is shut close and pull deflated suit in. Reverse to place it back onto the suitport adapter. Now compare this with a conventional airlock. $\endgroup$ – TildalWave May 2 '15 at 13:58
  • $\begingroup$ The astronaut has to get dressed, open a hatch, somehow enter through it, and then close it. The difference is whether you do all of that first, and then enter an airlock. Or if, as the suitport does, by clever design eliminate some dangerous expensive steps in that process. What if the Orion, as specified today, fails to re-gas after the one and only EVA it is designed to handle? That's at least 7 times more dangerous than one suitport failing. And after launch there are no "covers" on the suitports, what are you talking about that I am missing? $\endgroup$ – LocalFluff May 2 '15 at 14:07

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