April 2 (UPI) -- NASA officials want to send two private missions to the International Space Station over the next two years and are seeking proposals to make it happen.
"We are in an incredible time for human spaceflight with more opportunities to access space and grow a thriving commercial economy in low Earth orbit," NASA's ISS program managers Dana Weigel said Wednesday in an [online announcement](https://www.nasa.gov/humans-in-space/commercial-space/leo-economy/nasa-continues-support-for-private-astronaut-missions-to-space-station/).
"NASA remains committed to supporting this expansion by leveraging our decades of expertise to help industry gain the experience needed to train and manage crews, conduct research and develop future destinations," Weigel said.
"Private astronaut missions are a key part of this effort, providing companies with hands-on opportunities to refine their capabilities and build partnerships that will shape the future of low-Earth orbit."
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NASA officials eventually want to place a "continuous human presence" in low Earth orbit aboard the ISS, which orbits the Earth about 270 miles above its surface.
NASA previously supported three private missions to the orbiting ISS space lab over the past three years and has a fourth planned no sooner than May.
Axiom Space accomplished the prior three missions and will undertake this year's mission, according to NASA.
Each of the private missions including docking at the ISS for up to 14 days with mission timing dependent upon other missions scheduled at the ISS and the amount of space traffic going to and from it.
The ISS has been active for more than 20 years and is a "critical test bed for NASA to understand and overcome the challenges of long-duration spaceflight and to expand commercial opportunities in low Earth orbit," according to NASA.
NASA is accepting proposals by interested parties until 5 p.m. May 30.