WASHINGTON — Moon Express announced Oct. 1 that it is buying three launches for its lunar lander spacecraft from Rocket Lab, a deal that should unlock a two-year extension of the Google Lunar X Prize competition.

Mountain View, California-based Moon Express plans to use the launches to send to the moon new, smaller versions of its MX-1 lunar lander. Two of the launches will take place in 2017, with a third to be scheduled. All three will use Rocket Lab’s Electron small launch vehicle, whose first flight is scheduled for no earlier than late 2015 from New Zealand.

In an Oct. 1 interview, Bob Richards, co-founder and chief executive of Moon Express, said that Electron will be able to send “something under” 10 kilograms to the surface of the moon. “That’s good for our purposes in our first missions,” he said. “Call it an entry-level lunar mission.”

Moon Express originally planned to build a much larger lunar lander, based on a common spacecraft bus developed for NASA’s Lunar Atmosphere and Dust Environment Explorer, and later developed a revised, smaller design. Richards said advancements in space technology, coupled with the growing availability of small, low-cost launch vehicles like Electron, enabled Moon Express to further shrink their lander and still meet the requirements of the prize competition.

Moon Express will use that first mission to try to win the Google Lunar X Prize, which offers a $20 million first prize for the first privately-developed spacecraft to land on the moon, travel at least 500 meters across its surface, and transmit photos and video. While many teams are developing rovers to traverse the lunar surface after landing, the MX-1 lander will take off again and “hop” to another landing site to fulfill the travel requirement.

Buying multiple launches provides a backup plan should the first mission fail. “If we fall short on the first, we’ll do it again on the second, and if we fall short on the second, we’ll do it again on the third,” Richards said. If Moon Express is successful on the first or second mission, he said Moon Express would sell capacity on later missions to scientists or space agencies.

The contract should enable an extension of the Google Lunar X Prize. In May, the X Prize Foundation announced that it would extend the competition’s deadline to the end of 2017, provided at least one team had a launch contract in place by the end of 2015. Moon Express is the first of the remaining 16 teams to announce a contract, although Richards said they had yet to confirm with the X Prize Foundation that their contract met the requirement to extend the competition’s deadline.

Richards said Moon Express is already planning for increased interest in lunar missions if their initial MX-1 missions are successful: The contract with Rocket Lab includes options for two additional Electron launches. “I look at the first landing on the moon as the space equivalent of the four-minute mile. It’s going to change the definition of what’s possible,” he said. “We may have a problem satisfying all the demand, not a lack of customers.”