The next generation crewed spacecrafts is about to fly in the decade of 2020. Not only those in the headline here are trying to make it, but more are being developed privately and internationally.

Orion will be able to support its crew longer than the current commercial contenders, 4 astronauts during 21 days I've heard. First of all, is that basically true? And if so, is that a deep early design choice, or just a formality of the specifications because Orion is planned to fly around the Moon while the commercial contenders are contracted for LEO only?

What would it take to extend the crew support lifetime of a spacecraft of this next generation? Say, to make Starliner and Dragon also being able to support 4 crew during 21 days. Would it be enough to extend the size of the service module in order to increase storages of consumables? Or to replace a consumed service module with a fresh one, doubling the life support time?

Do they just need more luggage or a differently designed ship?


2 Answers 2


Orion as a capsule will have an actual Service Module attached. It is being provided by ESA, as a highly modified version of the ATV cargo transport. This is a pretty large add on, and provides both fuel for engines for maneuvering and supplies for the crew.

Dragon and Starliner do not have quite the same Service Module. Dragon has a trunk, which in the cargo and crew versions have solar panels on it. Like Orion it is discarded before reentry, but the SpaceX trunk is used for external unpressurized cargo carriage currently.

Thus the consumables (Oxygen, Nitrogen, maneuvering fuel) need to be held somewhere. Orion has space in the Service Module. Whereas Starliner and Dragon will need to carry it internally which limits them.

Additionally, you REALLY want a separate space for the potty. Soyuz when in orbit has two separate modules that can be used. Apollo did not but could use the LM vs the CM during most lunar flights. Orion is big enough they can probably carve out a corner for this sort of stuff.

  • $\begingroup$ I thought "the trunk" (of Dragon, Starliner) just was a part of a service module that was otherwise essential for life support, beyond the short time it takes to enter the atmosphere. Are you sure they only have "trunks" to carry cargo, and survive on what they have "indoors"? Well that makes a lot of a difference. I read that ESA is developing the service module for Orion based on their "trunk" for their uncrewed and canceled ATV cargo vehicle. Hmmm... $\endgroup$
    – LocalFluff
    Commented Mar 21, 2017 at 20:46
  • 1
    $\begingroup$ @LocalFluff Dragons trunk I am certain, less so on StarLiner. I am not sure exactly what they are doing. $\endgroup$
    – geoffc
    Commented Mar 21, 2017 at 21:04
  • $\begingroup$ That's a disappointment, I hoped that SpaceX had greater plans for their Dragons. I suppose they save their ambitions for bigger vehicles and simply ignored the potential for Moon capabilities for a Dragon without an extra habitation module. $\endgroup$
    – LocalFluff
    Commented Mar 21, 2017 at 21:10
  • 3
    $\begingroup$ @LocalFluff I think they designed for the mission at hand. ISS Servicing. You have seen how they develop. Design for the mission at hand and iterate. So Dragon Cargo to Dragon V2, both for ISS missions. So short trips. Now they want to do Red Dragon to Mars (unmanned) and Apollo 8 reprise (White Dragon, manned) which will require iterations. I expect they will use an external hab module (Bigelow perhaps?) and do an Apollo style manuever to get it out of the second stage? Or maybe modify the trunk? We shall see. External module sees MUCH simpler. $\endgroup$
    – geoffc
    Commented Mar 21, 2017 at 21:35
  • $\begingroup$ Why the importance of a separate space for the potty? I mean … yes it’s more comfortable, but humans have been forced to defecate in close proximity on expeditions (think alpine expeditions) for ages. $\endgroup$
    – Michael
    Commented Jan 13, 2020 at 13:25

There should be enough supply of everything needed for life support. Oxygen at first, but also the absorbers needed for the removal of carbon dioxide from the atmosphere in the spacecraft.

Water for drinking will be also important, sometimes also used for cooling of the spacecraft.

Spare filters for cleaning the atmosphere, removing dust and odors. Electrical power for the life support system and the space ship, fuel used for maneuvering and attitude control. If an atmosphere containing not only oxygen but also nitrogen is used also a supply of nitrogen to replace leakage loss. Food would be necessary too and some free space for storage of waste.

  • $\begingroup$ But could such "trunk" storages be connected to working systems inside the CST-100 and Dragon V2? They don't even have a toilette. I would never think that a Soyuz could be reasonably upgraded to support even a single crew for 21 days, it is a LEO creature. I wonder if Orion is alone with going beyond that. $\endgroup$
    – LocalFluff
    Commented Mar 21, 2017 at 20:54
  • $\begingroup$ Additional external "trunk" storages may be used for gases, water, fuel and electricity. But using them for additional food and replacement filters should be possible without an EVA. $\endgroup$
    – Uwe
    Commented Mar 22, 2017 at 9:18

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