WASHINGTON — House Science Committee Chairman Lamar Smith (R-Texas) wants to know when NASA’s Orion deep-space capsule will be ready to provide backup crew and cargo delivery services to the international space station and whether the Lockheed Martin-built vehicle should replace one of the two commercial crew taxis NASA is now funding.

Boeing and Space Exploration Technologies Corp. beat out Sierra Nevada Corp. in September for a pair of contracts worth a combined $6.8 billion to complete competing crew taxis that would ferry crews to and from station starting in 2017.

“If Orion could provide a redundant capability as a fallback for the commercial crew partners, why is it necessary to carry two partners to ensure competition in the constrained budget environment?” Smith asked NASA Administrator Charles Bolden in an Oct. 7 letter co-signed by Rep. Steven Palazzo (R-Miss.), chairman of the House Science space subcommittee.

The 2010 NASA authorization law that requires the agency to build Orion also requires that the capsule be capable of servicing ISS should other U.S. vehicles be unavailable. Bolden has said repeatedly that NASA is not planning to send Orion to ISS. Doing so, the NASA chief has said, would be expensive, inefficient and possibly viewed by the agency’s commercial crew partners as unfair government competition.

Smith and Palazzo gave Bolden until Oct. 21 to respond.