An educational article with references listed below.
NASA, together with Blue Origin and SpaceX, is accelerating the development of lunar landers for a crewed mission in 2028. Their designs and operational concepts are being simplified to match the capabilities of each system. Before carrying humans, both companies must conduct uncrewed demonstrations and obtain NASA certification.
Spacecraft rendezvous in orbit
In the initial mission, four astronauts will launch from Kennedy Space Center in Florida aboard the Orion capsule atop the SLS, or Space Launch System, rocket. Orion will then rendezvous and dock with a commercial lander. Two astronauts will transfer to the lander for the journey to the lunar surface, while the other two remain aboard Orion.
The previous plan placed the rendezvous in a near-rectilinear halo orbit around the Moon. Under the new concept, the rendezvous location will be tailored to the characteristics of each company's system. Choosing the orbit is crucial because it determines propellant requirements, travel time, and the opportunities for the two spacecraft to meet safely. Artemis III has also been revised into a demonstration in which test versions of the Blue Origin and SpaceX landers will rendezvous and dock with Orion in low Earth orbit.
SpaceX's orbital strategy
SpaceX is continuing to develop cryogenic propellant aggregation in low Earth orbit. Cryogenic propellant is liquid fuel kept at extremely low temperatures. Several Starship tankers will transfer propellant to a Starship depot waiting in orbit, much like several delivery vehicles supplying a fuel station. The depot will then refuel the Starship Human Landing System for the journey to the Moon.
Under the updated operations plan, Starship HLS will wait for Orion in Earth orbit. After docking, Starship's engines will perform a trans-lunar burn to propel the combined spacecraft toward low lunar orbit. NASA is working on modifications to Orion to make this plan possible.
Low lunar orbit was chosen to reduce the amount of propellant that must be collected in space. This trajectory could also shorten Starship's journey from the lunar surface back to its rendezvous with Orion. SpaceX must demonstrate the propellant aggregation and transfer process during an uncrewed demonstration mission.
Blue Origin's three stages
Blue Origin is taking a different approach to the crewed landing in 2028. The company is postponing the use of in-space propellant transfer and has chosen three transfer stages to send the Blue Moon Mark 2 Alpha Lander to the Moon. The three stages operate like a multistage rocket and are released one by one as their propellant is depleted.
After being launched separately into low Earth orbit and assembled, the lander and its transfer stages will travel to an elliptical polar orbit around the Moon. Compared with the previously planned orbit, this trajectory could speed up the return journey from the surface to Orion, reduce Blue Moon's propellant requirements, and maximize the capabilities of SLS.
Orion can be launched during several available windows to rendezvous with Blue Moon in that orbit. Two astronauts will then descend toward the Moon's south pole and return to Orion after completing their surface activities. Blue Origin will also test the complete mission profile without a crew, drawing on lessons from the robotic Mark 1 mission.
Tests before carrying humans
NASA will select the company that receives the first landing opportunity based on the readiness of its lander. The selected system must be able to deliver astronauts to the surface and return them safely to lunar orbit in 2028. A second crewed landing opportunity will be awarded afterward.
For the initial surface mission, NASA is targeting two moonwalks lasting about two hours each. The astronauts will collect lunar samples while testing spacesuits made by Axiom Space. The series of uncrewed demonstrations and the certification process remain key stages before humans are permitted to board either lander.
