How many service module variants will Orion have?

[willpittenger]

I figure that Orion needs one to reach ISS and a larger version with more thrust, consumables, and propellant to reach the Moon. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[jimfromnsf]

There is only one version. Just different propellant loads

 

[willpittenger]

I just thought of something. Could the OMS engine from the shuttle serve as Orion's SM engine? I see it is hyperbolic. So if it has enough thrust... I suppose they could use the shuttle's RCS thrusters too. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[PistolPete]

Untill recentlly I was under the impression that the STS OMS engine <i>was</i> going to be used for the Orion SM main engine. Recently I found out that the engine for the Orion SM was going to be based on the AJ-10 engine, which powers the second stage of the Delta II. <div class="Discussion_UserSignature"> <p> </p><p><em>So, again we are defeated. This victory belongs to the farmers, not us.</em></p><p><strong>-Kambei Shimada from the movie Seven Samurai</strong></p> </div>

 

[jimfromnsf]

The shuttle thrusters are too big as thrusters for the CEV and too small as a main engine and too expensive. The CEV uses 25 lb thrusters

 

[chode]

As I understand it, the Shuttle OMS engine could have been used as the Orion SM main engine. It has about the right amount of thrust. (fuel is monomethyl hydrazine and the oxidizer is nitrogen tetroxide). Instead, they're going with the Aerojet AJ10, which is used in the Delta II (fuel is Aerozine-50 and the oxidizer is nitrogen tetroxide) and I assume this will also fuel the Orion RCS system (so they could transfer fuel between systems if needed). Interestingly (at least to me), this is the same fuel used in the Apollo lunar module RCS system. <br /><br />FYI: Aerozine-50 is a 50/50 mix of hydrazine and unsymmetrical dimethylhydrazine.<br /><br />Regards

 

[rfoshaug]

If I remember correctly (I could well be wrong), I believe that Aerozine-50 gives slightly better ISP than MMH. Although engine design probably has a greater effect on ISP than the differences between those fuels.<br /><br /><br />Is there anything that needs do be done to manrate the AJ10? When commanded to fire, that engine MUST fire... <div class="Discussion_UserSignature"> <p><font color="#ff9900">----------------------------------</font></p><p><font color="#ff9900">My minds have many opinions</font></p> </div>

 

[gunsandrockets]

<Recently I found out that the engine for the Orion SM was going to be based on the AJ-10 engine, which powers the second stage of the Delta II.><br /><br />Are you sure? That sounds like old news to me. The last time I heard that from a credible source was from an old nasawatch.com story from a time prior to Lockheed winning the Orion CEV contract.<br /><br />http://uplink.space.com/showthreaded.php?Cat=&Board=missions&Number=751622&page=5&view=collapsed&sb=5&o=0<br /><br />