Odd shape of the evolving Service Module (SM) for Orion CEV

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bpfeifer

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Uh, I didn't see any "double cylinder" shape in those pictures. I saw a cone stuck on top of cylinder. This is very similar to Apollo era stuff.<br /><br />I agree those thrusters do look odd to my eyes.... <div class="Discussion_UserSignature"> Brian J. Pfeifer http://sabletower.wordpress.com<br /> The Dogsoldier Codex http://www.lulu.com/sabletower<br /> </div>
 
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jimfromnsf

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The whole "cone" is not all CM, the aft (5 m cylinder) is part of the SM
 
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gunsandrockets

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"Uh, I didn't see any "double cylinder" shape in those pictures. I saw a cone stuck on top of cylinder."<br /><br />Look again, in particular at the closeup image. The forward part of the SM is a relatively flat cylinder which completely covers the base of the Crew Module (CM).<br /><br />If you look at the smaller scale image, only the forward blue-colored cone is the CM, the rest of the structure (the double-cylinder) is the SM.
 
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bpfeifer

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OK, my bad. Now I see what you're refering to. It is a bit odd. <div class="Discussion_UserSignature"> Brian J. Pfeifer http://sabletower.wordpress.com<br /> The Dogsoldier Codex http://www.lulu.com/sabletower<br /> </div>
 
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gunsandrockets

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"OK, my bad. Now I see what you're refering to."<br /><br />No big deal. I was confused the first time I looked at it too.<br /><br />"It is a bit odd."<br /><br />No kidding. The only reason I can think of for using that odd SM shape is so Lockheed can easily re-use the same cylindrical propellant tanks for the SM engine that the Shuttle uses for it's OMS engines. Eh, the compromises one must make for the sake of expediency I suppose. Though it seems to me even those cylindrical tanks could still fit into a simpler cone shaped SM.<br /><br />I know NASA would probably never go for it, but instead of saving a few hundred pounds by shrinking the SM the way Lockheed is now doing I would do something completely different. I would keep the same SM length, but expand the SM diameter to the full 5m of the CM. I would move the SM tanks and equipment to the perimeter and use the extra interior volume in the center of the SM for a pressurized crew cabin mission module space. Access to the module would be via a hatch in the CM heatshield (which is why NASA would never go for it even though the same concept was successfully tested in the Gemini spacecraft!)<br /><br />Extra pressurized space in the SM would not only be useful to the crew (and provide a better radiation storm shelter because of the surrounding propellant tanks), it would also be usefull for ISS cargo missions. On an ISS cargo mission the SM could sacrifice some tonnes of propellant (unneeded for LEO mission or in excess of ISS reboost needs) and trade it off for tonnes of extra cargo carried in the pressurized mission module space!
 
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docm

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Now we know where the weight was shaved off; they put the SM in a lathe <img src="/images/icons/tongue.gif" /> <div class="Discussion_UserSignature"> </div>
 
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gunsandrockets

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"Now we know where the weight was shaved off; they put the SM in a lathe"<br /><br />Or it's the...<br /><br />Space Dradle!
 
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jimfromnsf

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<blockquote><font class="small">In reply to:</font><hr /><p><br /><br />1. The only reason I can think of for using that odd SM shape is so Lockheed can easily re-use the same cylindrical propellant tanks for the SM engine that the Shuttle uses for it's OMS engines. Eh, the compromises one must make for the sake of expediency I suppose. Though it seems to me even those cylindrical tanks could still fit into a simpler cone shaped SM.<br /><br />2. I know NASA would probably never go for it, but instead of saving a few hundred pounds by shrinking the SM the way Lockheed is now doing I would do something completely different. I would keep the same SM length, but expand the SM diameter to the full 5m of the CM. I would move the SM tanks and equipment to the perimeter and use the extra interior volume in the center of the SM for a pressurized crew cabin mission module space. Access to the module would be via a hatch in the CM heatshield (which is why NASA would never go for it even though the same concept was successfully tested in the Gemini spacecraft!)<br /><br />3. Extra pressurized space in the SM would not only be useful to the crew (and provide a better radiation storm shelter because of the surrounding propellant tanks), it would also be usefull for ISS cargo missions. On an ISS cargo mission the SM could sacrifice some tonnes of propellant (unneeded for LEO mission or in excess of ISS reboost needs) and trade it off for tonnes of extra cargo carried in the pressurized mission module space!<br /><br /><p><hr /></p></p></blockquote><br /><br />1. The OMS tanks are long out of production and they are not going to use the actual existing ones. The tanks will be a new design.<br /><br />2. Did you read the thread? It has nothing to do with saving weight. It is to allow for stowage of the solar arrays.<br /><br />3. The CEV is a crew transport vehicle (and maybe a unmanned cargo vehicle) nothing more. There is no need for a mission module, they will or already exist, ISS, LSAM, MTV et
 
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docm

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<font color="yellow">Also mixing crew and cargo is a no no.</font><br /><br />Many of us have been saying that since Challenger, and converts were easy after Columbia. <div class="Discussion_UserSignature"> </div>
 
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gunsandrockets

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"I believe those RCS thrusters are a part of the second stage not the SM."<br /><br />That is...very interesting. Could you please elaborate?<br /><br />
 
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jimfromnsf

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"Note the unusual RCS thrusters (in yellow) buried in the corner near the front of the SM..." <br /><br />No, those are the SM RCS. The upperstage RCS is going to be on its aft, near the J-2
 
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gunsandrockets

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[1. The OMS tanks are long out of production and they are not going to use the actual existing ones. The tanks will be a new design.]<br /><br />Link please.<br /><br />Since the SM engine is the same as the Shuttle OMS engine (despite being long out of production!) it seems reasonable to assume the same tanks will be used for the same engine. Why reinvent the wheel.<br /><br />[2. Did you read the thread? It has nothing to do with saving weight. It is to allow for stowage of the solar arrays.]<br /><br />That's real funny. I did read the nasaspaceflight.com thread before I ever began this thread here. I'm right and you are wrong. The primary reason for the smaller SM is to save weight. Other advantages of the shrouded SM design are a happy by-product.<br /><br />[3. The CEV is a crew transport vehicle (and maybe a unmanned cargo vehicle) nothing more. There is no need for a mission module, they will or already exist, ISS, LSAM, MTV etc. It doesn't need addition features.] non sequitur<br /><br /><br />I never claimed the feature was needed to perform the Orion missions.<br /><br />I described the advantages of adding the pressurized volume feature to the SM. I think those advantages justify the change. If you want to ignore that, fine.<br /><br />[Also mixing crew and cargo is a no no.] non sequitur<br /><br />I never advocated mixing manned Orion ISS missions with Orion ISS cargo missions.<br />
 
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jimfromnsf

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The engine for the SM is the Delta II second stage engine. It is not reasonable to use the same tanks. Tanks are not associated with engines, otherwise the Delta IV and Atlas V would have the same second stage tanks. The tanks are sized for the mission at hand, and there is a world of difference between the sizing for the shuttle OMS does vs the SM.<br /><br />Wrong. It is not a "smaller" SM. It has the same capabilities and tank size as a few months before. It has been repackage. It will be 5 meters on the launch, but during ascent, panels will be jettison that protect the solar arrays adn other items. There is weight savings due to jettison of the panels. <br /><br />Bad justication for little added value. <br />Yes, you proposed adding cargo to a manned ISS mission.
 
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gunsandrockets

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[The engine for the SM is the Delta II second stage engine.]<br /><br />Wrong. It is one of the Shuttle OMS engines instead. Here is the link proving it...<br /><br />http://www.aviationnow.com/avnow/news/channel_awst_story.jsp?id=news/aw090406p2.xml<br /><br />[It is not reasonable to use the same tanks. Tanks are not associated with engines, otherwise the Delta IV and Atlas V would have the same second stage tanks. The tanks are sized for the mission at hand, and there is a world of difference between the sizing for the shuttle OMS does vs the SM.]<br /><br />Well gee golly. The imagery from nasaspaceflight.com shows 4 cylindrical tanks in the SM. And the four cylindrical tanks for the Shuttle OMS hold about 10 tonnes of propellant. And the propellant mass needed by the SM is about 10 tonnes. How 'bout that?<br /><br />[Wrong. It is not a "smaller" SM. It has the same capabilities and tank size as a few months before. It has been repackage.] non sequitur<br /><br />Sigh. From the entire damned thread it should be obvious the diameter of the SM was reduced from 5m, hence 'smaller' as in smaller in one physical dimension. Sheesh.<br /><br />[It will be 5 meters on the launch, but during ascent, panels will be jettison that protect the solar arrays adn other items. There is weight savings due to jettison of the panels.]<br /><br />Ah, so I see you admit the reason was weight reduction, just as I claimed and you contradicted. Nice to see you recognize the truth. <br /> <br />[Bad justication for little added value.]<br /><br />I bow to such powerful reasoning.<br /><br />[Yes, you proposed adding cargo to a manned ISS mission.]<br /><br />Might I suggest you consider remedial reading classes?<br /><br />
 
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rubicondsrv

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"Might I suggest you consider remedial reading classes?"<br /><br />Might I suggest that all in this thread tone down the snide remarks?<br /> <div class="Discussion_UserSignature"> </div>
 
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CalliArcale

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*mod hat on*<br /><br />Snide comments in general have been noted, and are really not appreciated. I mean c'mon guys, we all share the same geeky passion here. It doesn't have to be so personal. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>
 
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gunsandrockets

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I apologize for the snark. Heck I've been provoked worse in the past and I shouldn't have let it get under my skin.<br /><br />Aside from the tone though, I stand by all the content!
 
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jimfromnsf

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Still wrong, <br /><br />It is at 5m. Plain and simple. The forward adapter (with systems in it) and the interface with the CM is 5 m. The aeroshell is still part of the SM, at 5m. It is like the D-IV upper stages with the smaller hung LOX tanks. The diameter is of those upperstage are 4 and 5m, which is the larger LH2 tank diameter. <br /><br />Shuttle OMS is 24klb not 20klb, big difference when it comes to tanks. Also, there is a difference in attach fittings. And once again they are out of production are and over built.<br /><br />Delta II second stage engine is being used. My references are not a 6 month old article. The OMS engines are reusable and therefore overbuilt and too expensive. DII had a production line for its engines, with 170 produced<br /><br />edited.<br />
 
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gunsandrockets

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"Delta II second stage engine is being used. My references are not a 6 month old article."<br /><br />The only reference I ever saw refering to the Delta II engine was from a time BEFORE the Orion contract was awarded to Lockheed-Martin.<br /><br />So put your source up where all can see, why don't you?
 
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MeteorWayne

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OK, somebody has to ask. SBU?? <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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telfrow

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<font color="yellow">Sensitive But Unclassified (SBU)</font> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>
 
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jimfromnsf

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Not BS but SBU. <br />you switched around the letters and forgot one
 
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