Originally Posted by

**gaetanomarano**
you can calculate the TEI+LOI propellant weight, but I think may be over 20 mT in total

The Apollo CSM had a delta-v of 2,800 m/s, which we can probably consider a worst-case scenario. If we assume the inert CEV mass is 12 mT, then we will need about 18 mT of propellant to achieve this. However, if we just need enough for LOI+TEI plus a few course corrections, then maybe we can get by with 2,200 m/s or so. In this case we would need about 12 mT of propellant.

**The total vehicle mass would then be 24 mT**, which is what I told you in an earlier post.

Originally Posted by

**gaetanomarano**
also, since the Orion must be a "standard vehicle", we must add the LOI propellant also for the missions that Orion will perform WITH the LSAM

Not necessarily.

**Orion can have the capacity to carry enough propellant for independent operations while still having the LSAM perform LOI for joint CEV/LSAM operations. Make Orion’s tanks large enough to carry 12 mT when operating alone but fill them to only 9-10 mT (as mission requirements dictate) when operating with the LSAM.** Using the LSAM’s higher efficiency engines for LOI will allow about 4 mT more payload each mission.