<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