Why they don't increase altitude of ISS to overcome drag

[abhaybakshi]

Experts -

Why they don't increase altitude of ISS to overcome slight atmospheric drag it faces. Due to this, they need to make altitude corrections frequently to ISS.

I want to know, why they can not put ISS in higher orbit where there is almost nil atmospheric drag (or may be altitude corrections are required once in 4-5 years...). Will it not be more fuel efficient approach ?

 

[davenn]

from this NASA page ...
http://www.nasa.gov/mission_pages/station/expeditions/expedition26/iss_altitude.html

Raising the space station’s altitude means that visiting vehicles will not be able to carry as much cargo as they could if they were launching to the station at a lower altitude, but it also means that not as much of that cargo needs to be propellant.

Other considerations include the amount of orbital debris, or space junk, at these different altitudes, and the amount of solar and cosmic radiation to which astronauts and cosmonauts are exposed.

Crew exposure to radiation can be a long-term health issue for crew members, a subject that doctors and researchers are learning more about as each crew member lives and works aboard the station and increases the pool of information on this important topic for future space exploration beyond low-Earth orbit, where it will be an even bigger concern since Earth is protected from much of this cosmic radiation by the Van Allen Belts, which are outside the station’s orbit.

“What we are balancing against this increase in altitude is vehicle capabilities to get to that altitude, how much cargo they can deliver, crew radiation exposure and orbital debris risk,” Spetch said. “Essentially, we want to fly as low as we can support from a propellant resupply standpoint and that altitude increases with solar cycle activity. Also key to us being so low now was taking full advantage of the cargo delivered by space shuttles. Otherwise we would be flying slightly higher now.”

Dave

 

[abhaybakshi]

Thanks Davenn. That answers everything.