Orion vs. Apollo: NASA's new moonshot

[Inside KSC News Feeds]

When astronauts return to the moon by 2020, they will do so following a familiar path and flying in a cone-shaped capsule that echoes the "good old days" of Project Apollo.




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[J.McDonald]

I notice in the linked article the follows specifications:

Craft___ Dry Mass___ Crew___ Habitable Volume
Apollo___ 5800kg_____ 3 _____ 6.17m3
Orion ___14000kg ____ 4 _____ 11m3

So it can be seen that, despite 'improvements' in modern materials and design, plus the benefits of scaling up, the original Apollo was actually more mass-efficient! You could use two of them, providing space for more crew, at considerbale less than the mass of the Orion. What gives?

Also I'm a bit confused about the description of cabin pressure: according to the article, Apollo had high pressure pure O2, whereas Orion will have lwoer pressure mixed air. That seems a bit odd, to me, because I though the whole point of pure O2 was that it allowed lower pressure, and that's why it's used in EMUs. Anybody able to clarify?

[Me2]

1. So it can be seen that, despite 'improvements' in modern materials and design, plus the benefits of scaling up, the original Apollo was actually more mass-efficient! You could use two of them, providing space for more crew, at considerbale less than the mass of the Orion. What gives?

2. Also I'm a bit confused about the description of cabin pressure: according to the article, Apollo had high pressure pure O2, whereas Orion will have lwoer pressure mixed air. That seems a bit odd, to me, because I though the whole point of pure O2 was that it allowed lower pressure, and that's why it's used in EMUs. Anybody able to clarify?

1. Different mission requirements.

2. Apollo was low pressure. !00% O2 at 5 psia. It was high pressure O2 only for Apollo 1 on the pad. It was change to N2 O2 (40/60 IIRC) mixture at sea level pressure that bled down to 5 psia during ascent. Orion will be at around 10 psia with a N2/O2 mixture which is similar to what the shuttle does for EVA's (not station EVA, but like HST). EVA suit are around 4.3 to 3.5 psia at 100%. The 10 psia only requires a 1/2 hour prebreathe. But Orion will only be supporting contingency umbilical EVA's, Altair will supporting the lunar EVA's

[J.McDonald]

1. Different mission requirements.

Really? I thought they were almost exactly the same- supporting a crew over a few days as they travel to and from the moon or a space station in LEO.

2. Apollo was low pressure. !00% O2 at 5 psia. It was high pressure O2 only for Apollo 1 on the pad. It was change to N2 O2 (40/60 IIRC) mixture at sea level pressure that bled down to 5 psia during ascent. Orion will be at around 10 psia with a N2/O2 mixture which is similar to what the shuttle does for EVA's (not station EVA, but like HST). EVA suit are around 4.3 to 3.5 psia at 100%. The 10 psia only requires a 1/2 hour prebreathe. But Orion will only be supporting contingency umbilical EVA's, Altair will supporting the lunar EVA's

Thanks- makes more sense now

[Me2]

Really? I thought they were almost exactly the same- supporting a crew over a few days as they travel to and from the moon or a space station in LEO.

Orion has to last in lunar orbit for more than two weeks.

[dave996]

Plus the Orion has a bigger crew and more propellant for a higher Delta V requirement to allow a abort on the way to the Moon and to put the itself and the big Lunar lander into a highly inclined Lunar orbit.

The Apollo was not more "mass effecient" than the Orion.

[J.McDonald]

Well, yeah, I thought I'd covered the 'bigger crew' bit. Two Apollos would carry the same crew as one Orion yet weigh two tonnes less, dry.
But I'd not thought of the higher delta-v. Presumably that's a really big difference. Mind you, Apollo had to do LOI.
I guess what was in the back of my mind was if we were allowing a bit more mass per crew member these days- maybe to make things more civilised or safer etc. Is this a factor?

[Me2]

Plus the Orion has a bigger crew and more propellant for a higher Delta V requirement to allow a abort on the way to the Moon and to put the itself and the big Lunar lander into a highly inclined Lunar orbit.

No, the lander performs the LOI burn not Orion. Same for the abort on the way to the moon

[dave996]

True, thanks for the correction.

[J.McDonald]

Sorry to drag this thread up again, but I still don't get it
Apollo could support a crew of three, could remain dormant for many weeks (is there some reason that it could only do this in LEO, and not LLO though?), and had the bonus of enough propellant to do LOI.
Orion has to support one extra person, remain in LLO for six months, and doesn't have to do LOI. Yet it weighs more than double what Orion did.
The mods to suport Orion is LLO for six months can't be all that heavy, can they?

[Rick]

What a shame that Orion will just be a memory if the Presidents Budget proposal passes.

[spacefan]

Correct me if i'm wrong but isn't the LEO Orion a stripped down version of BEO orion so presumably Lockheed Martin could do a bargain basement version and offer it for commercial crew.

[Khadgars]

I guess we should be calling Orion MPCV now right? Any one have any information on Orions first test flight coming up?

[Rick]

Ammended!