Fuel tank additions causing jump in crew size

Edit:
I'm not saying you can't have your future underage Space Navy crews grow up in weightlessness.
I'm saying it's stupid to do so.
And I'm not saying you can't leave adult Space Navy crews in weightlessness for 6 months, even for years.
I am saying it's stupid to do so.

Space Navy crews who grow up in 1 g or even better 1.5 or 2 g will be much,
much better at their jobs of killing the enemy than those who don't.
Adult Space Navy crews who are rotated back to 1 g or better spin Space Stations will be much
better at space combat than those who don't by orders of magnitudes.
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I had planned to share more links, but I see this will turn into a wall of text so I'll focus on this one.
The evidence is extensive. Adults who live long term in weightlessness come out
with from minor to major long term damage to vital areas of the body when it
comes to warfare from eyesight, to ability to handle high gees, to reaction time,
etc etc.
Kids who grow up in weightlessness would be by orders of magnitude even WORSE
off.

To conclude.
Anyone who allows their future Navymen to grow up in weightlessness would have a
Space Navy that is vastly outclassed in abilities regarding space combat.
For this reason, it is certain that any Space Navy would invest in Spin Space Stations
to ensure their underaged future Space Navymen have every possible advantage, and would be very unlikely
to leave their Adult Space Navymen in weightless any longer than 6 months at a time.
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Okay here's the links for you with select portions quoted.
www.universetoday.com/94155/space-travel-is-bad-for-your-eyes/
'A host of physical issues can result from the space environment, from bone loss and muscle atrophy...'
'Now, there’s another downside to long-term life in orbit: eye and brain damage.
'A team of radiologists led by Dr. Larry A. Kramer from The University of Texas Medical School at Houston
performed MRIs on 27 astronauts, measuring in each the shape and thickness of the rear of the eyes,
optic nerve, optic nerve sheath and pituitary gland.
In 7 of the 27 astronauts flattening of the backs of the eyes was noted, and enlargement of the optic nerve
was detected in nearly all of them — 26 out of 27.
In addition, four exhibited deformation of the pituitary gland.
The optic nerve. (NIH)
The changes to the eyes and optic nerves are similar to what are typically seen in those suffering from idiopathic
intracranial hypertension (IIH), a disorder characterized by increased pressure within the skull. Symptoms typically
include headache, dizziness and nausea, and if left untreated it can produce permanent vision loss through optic nerve damage.
“The MRI findings revealed various combinations of abnormalities following both short- and long-term cumulative exposure
to microgravity also seen with idiopathic intracranial hypertension,” said Dr. Kramer. “Microgravity-induced intracranial
hypertension represents a hypothetical risk factor and a potential limitation to long-duration space travel.”
Chief of flight medicine at NASA’s Johnson Space Center, Dr. William J. Tarver, noted that although no astronaut has
been kept from flight duties as a result of such risks, NASA will continue to “closely monitor the situation” and has placed
the potential danger “high on its list of human risks.”
The team’s paper was accepted into the journal Radiology on Feb. 1.
“Orbital and Intracranial Effects of Microgravity: Findings at 3-T MR Imaging.” Collaborating with Dr. Kramer were
Ashot Sargsyan, M.D., Khader M. Hasan, Ph.D., James D. Polk, D.O., and Douglas R. Hamilton, M.D., Ph.D.
Update Oct 24, 2013: Further investigation by researchers at Houston Methodist and Johnson Space Center have shown
more evidence of long-term eye damage after just two weeks in orbit. Read more.