Exit Orbiter.

Use notepad to open the scenario that you plan to use for your Mars mission.  You can probably find it here:  
start/my computer/local Disc C/Program Files/Orbiter/Scenarios.  If not, do a search.

Scroll down to the ships section.  Use the graphics below to check and possibly change the name of your ship to
eliminate spaces in the ship's name.

If you do not do this, all your TransX work will be lost when you try to save.
REMOVE SPACES FROM SHIP NAME
If you altered the name of your ship be sure to
save in notepad.

Relaunch your scenario in Orbiter.