NASA has been taking an initiative for a long time regarding its lunar gateway. At present they have 5 designs which will be tested on earth before releasing in the space.
These are related to the system which will help NASA understand the requirements, interface and design which will be needed to build a habitat around moon. This is being built specifically for the US astronauts to serve as a gateway. From here they will be able to descend to surface of the moon or go deeper into the space. This will act as an orbiting base encircling the moon.
Marshall Smith, who is the lead of the lunar exploration initiative from NASA provided further details of the tests. He informed these tests will help them get a side by side comparison of the creative concepts which have been received from the American industries. He also informed when they will procure for this habitat they are not going to give the companies any dictation about the design. Still they will be aware about their requirements, safety and risks during the procurement process. The tests are done to know what will be the basic needs of the habitats.
This declaration came after NASA announced that astronauts will visit moon within 2024. This announcement is related to a directive passed by the US government regarding lunar missions. For this reason, NASA seems to be determined to build the habitat by 2020. Lockheed Martin, Boeing and NanoRacks are some of the companies which had submitted their ideas to NASA.
Lockheed has built a Multipurpose Logistics Module (MPLM). The system will assist the Orion Spacecraft (through which astronauts will travel to the gateway and come back). It also has a space which will change according to the mission. This concept was originally made for the International Space Station.