The descent module comprising propellant tanks, a main engine, landing gear and supporting structure and an Ascent Module with a pressurized crew cabin, life support systems, docking systems, avionics, propellant tanks and engine for lunar ascent.

[8] Altair would also be capable of flying uncrewed missions,[8] as had been proposed with LM Truck concept during the Apollo Applications Program.

[citation needed] Unlike the Apollo LM, in which the entire cabin was depressurized during extra-vehicular activity, the airlock would allow a crew member with a malfunctioning spacesuit to quickly return to the Altair spacecraft without having to terminate the entire EVA, and allowed the landing party to complete most of their tasks during their 7-day lunar stay.

The Apollo LM, as advanced in both computer and engineering technology in its day, used hypergolic fuels in both of its stages, chemicals that combust on contact with each other, requiring no ignition mechanism and allowing an indefinite storage period.

Both the cryogenic and hypergolic systems, like that of the Apollo LM, would be force-fed using high-pressure helium, eliminating the need for malfunction-prone pumps utilized in most rocket technology.

Originally, NASA wanted to power the ascent stage using LOX and liquid methane (LCH4) engines, RS-18, as future missions to Mars would require the astronauts to live on the planet.

The development of Altair was managed by the Constellation Lunar Lander Project Office at Johnson Space Center (JSC).

Northrop Grumman, which built the Apollo Lunar Module, was contracted to help the project office develop the system concept.