And West, whereas Vandenberg has the Pacific to take care of most launches that fail to reach orbit. (Earth rotates East under the longitudinally launched object.)
If you’re putting something in “equatorial” orbit, the Earth’s rotation gives an extra boost to things launched Eastward, more so the closer to the equator the launch point is.
A polar orbit launch requires more energy for that lack of Eastward rotational boost.
Pre-Challenger disaster, Vandenberg was being forced to prepare for polar SST launches. As such, the SRBs were being re-designed to be fabricated out of carbon fiber to lighten the mass to help make up for the extra energy needed.
The failure of that Challenger SRB put an end to that mandate.
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