ESA Document - Emits - ESA

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HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 123 of 422
imply that either the propulsion is assembled first, and the habitable elements later, or that the
two parts, manned and unmanned, are integrated in parallel but at different orbital stations. The
means to mate the two parts would include an orbital manoeuvre that has not yet been studied.
The propulsion stages need 18 launches for in-orbit assembly. Assuming a launch rate of 2
months, and one month of in-orbit assembly and commissioning, about 36 months (3 years) are
necessary to complete the propulsion system build-up. All launches are with Energia.
2.12.5 Options
Besides the assembly option mentioned above, a further time saving would come from a powerup
of the Energia launch capability. If this launcher could be made ready for launch every
month, possibly using two separated launch processes and launchpads, and provided that the inorbit
commissioning can actually be accomplished in one month each propulsion module, it
would be possible to save between 1 and 1.5 years along the in-orbit assembly process. The
investment and the relevant benefits of doing this should be assessed with a dedicated analysis in
the next phase.