WASHINGTON — There are more science experiments headed to the international space station than NASA astronauts have time to conduct, an agency official said here Oct. 7 at a meeting of the U.S. National Research Council’s committee on biological and life sciences in space.

“If you ask me, we’re at a crew-time max,” Rod Jones, manager of NASA’s ISS Research Integration Office at the Johnson Space Center in Houston, said at the meeting. “We are literally going into an increment coming up where we have allocated to us 875 hours [of research time], and I have about 1,400 hours of research.”

This increment, known internally as 43/44, is scheduled to begin in March with the arrival of veteran cosmonaut Gennady Padalka and fellow Expedition 43 crewmates Mikhail Kornienko and NASA’s Scott Kelly, and end in late September or early October when Padalka flies space tourist Sarah Brightman and Danish astronaut Andreas Mogensen back home after the first-time spacefliers’ brief visit (Kornienko and Kelly will remain behind for another six months, completing the first one-year stay at ISS).

NASA and its partners stagger Soyuz arrivals and departures to maintain a standing crew of six, including three for the U.S. side of the space station and three for the Russian side.

With an 875-hour allotment for 1,400 hours of research, crews active in the U.S. side of station for increment 43/44 will dedicate about a fifth of their time in orbit to science but leave more than 20 days’ worth of research undone by the time they return to Earth. The vast majority of the crew’s remaining waking hours are consumed by the routine maintenance tasks required to keep station habitable and flight-worthy.

NASA officials from Jones to William Gerstenmaier, the agency’s top human spaceflight official, have long said there are not enough hands on deck to support all the research NASA wants to do on station. Following the loss of the Space Shuttle Columbia in 2003, ISS was staffed by two-person crews until the space shuttle resumed regular space station visits in 2006. The ISS gradually returned to six-person operations, which is the current upper limit given that only two Soyuz capsules — the only spacecraft able to send crews to and from station since the shuttle flew its final mission in 2011 — are docked at the outpost at a time.

Competing crewed spacecraft in development at Boeing Co. and Space Exploration Technologies Corp. would seat as many as seven, the maximum number space station is designed to accommodate for long-duration stays.

The extra seats on the commercially operated systems will allow NASA to send four of its own astronauts at a time to station (Russia will continue to fly Soyuz, so NASA’s commercial partners will not need to launch every crew member headed to station), increasing weekly hours available for science operations on the U.S. side of ISS to nearly 70 from the current 35, Jones said. The fourth crew member would work almost exclusively on science, Jones told the National Research Council panel.

“We’re looking at what we think our max throughput is,” Jones said. “When we get the fourth crew, we think it’s going to be about 5.5 metric tons [of science payloads a year], sustained.”

How long NASA can sustain that pace will depend on when commercial transportation systems become available — the agency has said no sooner than late 2017 — and how long the station keeps flying. The White House said in January that it wants to continue operations through at least 2024. The U.S. agency’s 15 international partners, signatories of a 1998 intergovernmental agreement that formalized the station partnership, are still working to secure commitments to continue through 2020.

In the meantime, the agency is making do with what it has: the cargo version of SpaceX’s Dragon capsule, Orbital Sciences’ expendable Cygnus space freighter, and roughly 35 hours of crew time a week dedicated to research.

Of the two commercial cargo craft, each of which is on the hook to deliver 20 metric tons of cargo through 2017, only SpaceX’s can return experiments to researchers on the ground. Compared with the shuttle, which landed on a runway at NASA’s Kennedy Space Center in Florida, the sea-landing Dragon takes much longer to get specimens from the station back to scientists — two or three days, compared with about four hours for the shuttle, Jones said.

But at the other end of the pipeline, it takes less time these days to get an experiment to orbit than it once did. If an experimental payload is ready to fly, it can get on the manifest as soon as six months before a scheduled Orbital or SpaceX delivery, Jones said.

“When I started in the office seven years ago it was a two-year cycle to fly anything,” Jones told the NRC panel. “But now we’ve moved to a whole new paradigm where we’re trying to operate more like a laboratory.”

And NASA is the only entity with access to that laboratory.

By law, half of all resources in the U.S. segment of the space station — crew time, electrical power, volume and equipment, to name a few — must be available for non-NASA research. Non-NASA research, which includes projects led by other U.S. government agencies and the private sector, is managed by the Melbourne, Florida-based nonprofit Center for the Advancement of Science in Space, or CASIS. The group gets $15 million a year from NASA, including $3 million a year to directly fund research projects.

According to its website, the group has gotten 16 science payloads to station since January, when Orbital delivered the first CASIS-sponsored experiments to fly in space. Counting experiments that have yet to fly, and ground-based research, CASIS has so far funded about $10 million worth of science, spokesman Patrick O’Neil wrote in an Oct. 14 email. CASIS eventually hopes to get nongovernment sources of funding for the research it sponsors, but that has not happened yet.