STS-73 is no class of a space Shuttle, but a space shuttle mission. It was flown by the Orbiter OV-102 Columbia, during October-November 1995.
The Shuttle carries a set of oxygen tanks inside, behind the walls of the payload bay, which are used for two purposes: Together with hydrogen in a second set of tanks, the oxygen is used for producing electricity and water. The oxygen, which does not get used for producing electricity gets used for breathing.
For allowing some flexibility, the Shuttles allow installing additional tanks, first in empty bays behind the payload bay walls, then some Orbiters can also install tanks into the payload bay. These Orbiters which allow the tank modules inside the payload bay are called Extended Duration Orbiters.
Columbia was one of the EDO capable Orbiters (The only remaining after STS-107 is OV-105 Endeavour).
It was able to install five pairs of tanks (one oxygen, one hydrogen) behind the payload bay wall and four pairs of tanks into the payload bay.
With three pairs of tanks, a Shuttle can spend up to 8 days in Orbit.
With five pairs of tanks, the Shuttle can spend up to 12 days.
With 8 pairs of tanks, the Shuttle can spend up to 18 days.
So, for flying the 16 day STS-73 mission, Columbia had 4 oxygen tanks behind the payload bay walls and 4 oxygen tanks inside the payload bay on the EDO pallet.
· 1 decade ago