NASA’s goal of securing commercial astronaut taxi services to the international space station faces challenges related to contracting rules, oversight and crew safety requirements, NASA’s Office of the Inspector General (OIG) said June 30.

“In selecting the timing and appropriateness of potential procurement mechanisms, NASA must balance its role as a supporter of commercial partners with its responsibility to ensure that U.S. commercially developed vehicles are safe for NASA astronauts, meet the Agency’s needs, and provide for a viable domestic alternative to the [Russian] Soyuz vehicle,” OIG wrote in a June 30 report.

The agency’s internal watchdog did not make any formal recommendations. But the report said NASA should quickly communicate to its commercial partners its vehicle safety requirements as well as the process by which it will certify compliance with those requirements.

The OIG also urged NASA to carefully consider the contract vehicle it will use to procure commercial crew transportation services. Options include “an acquisition strategy that relies either on funded Space Act Agreements; competitive procurements guided by the Federal Acquisition Regulation (FAR), in particular fixed-price contracts; or some combination of both,” OIG wrote.

Each approach has associated risks, the report said.

Use of Space Act Agreements, for example, “limits government control compared to traditional procurement contracts based on the Federal Acquisition Regulation.” Conversely, with a fixed-price procurement “a company’s motivation to increase profit margins by cutting costs and creating efficiencies may conflict with the requirement to continually improve the safety of their system,” OIG said.

Also, because NASA has not set human-rating requirements for commercial drew vehicles, the fixed-price option might expose the agency to additional expenses that arise in a spacecraft’s design phase.

In a fixed-price procurement, if NASA changes its requirements during development, “contractors may assert the agency is going beyond the contract’s scope in which case NASA would be required to pay the contractor for necessary changes.”

OIG also said NASA must “make the decision to purchase additional Soyuz seats for flights in 2016 and beyond by spring 2013, at least 3 years before commercial partners are expected to be ready to provide transportation services.”

Companies that have already gotten NASA funding to develop commercial crew transportation systems include Blue Origin; Boeing; Sierra Nevada Space Systems; Space Exploration Technologies Corp.; and United Launch Alliance.