(CNN) An unmanned Russian rocket is scheduled to blast off from the Baikonur Cosmodrome in Kazakhstan at 12:55 a.m. ET Friday on a supply run to the International Space Station .

NASA says the Progress supply ship will ferry up more than 3 tons of food, fuel, water, oxygen and supplies. It is expected to dock with the space station on Sunday at 3:13 a.m. ET.

Missions like this can be fairly routine, but three spacecraft carrying tons of supplies to the space station have been lost since last October:

A SpaceX Falcon 9 rocket carrying a Dragon supply capsule exploded shortly after liftoff Sunday from Cape Canaveral Air Force Station in Florida. It was carrying a spacesuit , water filtration equipment, crew provisions, food, water, student experiments and the first International Docking Adapter . The 1,000 pound adapter was meant to be a portal where SpaceX and other commercial spaceships carrying astronauts would dock with the space station.

Another Russian rocket, Progress 59, went out of control after launch on April 28 and burned up on re-entry in May. It was carrying crew clothing, spacewalk hardware, propellant, oxygen, water, spare parts, supplies and experiments.

In October 2014 an Orbital Space Sciences Corporation Antares rocket had to be destroyed when a problem developed after launch. It was carrying crew provisions, experiments and equipment.

NASA says the three-person crew on the space station has enough supplies to last until October, even without the gear on the Progress.

"The space station crew is fine on orbit," Gerstenmaier said. "They've done a tremendous job of balancing all the consumables on orbit. We're in good shape from a food standpoint."

He said the crew is in no danger but will need to "watch the water levels." One of the most important items lost in the SpaceX explosion was a piece of equipment that filters water.

"Even without processed water, we have enough water supplies on orbit until late 2015," NASA spokeswoman Stephanie Schierholz told CNN in an email.

"We've always assumed we would lose a vehicle every so often," said Michael Suffredini , manager of the International Space Station Program for NASA. But he added "having three this close together is not what we'd hoped for."

The current crew on the space station is NASA astronaut Scott Kelly and Russians Gennady Padalka and Mikhail Kornienko.

Kelly and Kornienko are taking part in what NASA calls " The One-Year Crew ." They're living on the space station about a year to explore the effects of long-term space flight on the human body.

Three more crew members are scheduled to go to the space station on a Russian spacecraft later in July: Oleg Kononenko, Kjell Lindgren and Kimiya Yui.

More about the space station:

The station orbits about 248 miles (400 kilometers) above Earth. It circles the planet every 90 minutes

NASA says more than 200 people from 15 countries have visited the station since November 2000.

The space station measures 357 feet end-to-end and is larger than a six-bedroom house.

What do the astronauts do up there? Mostly, they conduct experiments . But they also exercise to offset the effects of near-zero gravity.