Starship HLS (Human Landing System) is a lunar lander variant of the Starship spacecraft that is slated to transfer astronauts from a lunar orbit to the surface of the Moon and back. It is being designed and built by SpaceX under the Human Landing System contract to NASA as a critical element of NASA's Artemis program to land a crew of astronauts on the Moon.
The mission plan calls for a Super Heavy booster to launch a Starship HLS into Earth orbit, where it will be refueled by multiple Starship tanker spacecraft before boosting itself into a lunar near-rectilinear halo orbit (NRHO). There, it will rendezvous with a crewed Orion spacecraft that will be launched from Earth by a NASA Space Launch System (SLS) launcher. A crew of two (or more) astronauts will transfer from Orion to HLS, which will then descend to the lunar surface for a stay of approximately seven days, including at least five EVAs. It will then return the crew to Orion in NRHO.
In the third phase of its HLS procurement process, NASA awarded SpaceX a contract in April 2021 to develop, produce, and demonstrate Starship HLS. An uncrewed test flight planned for 2025 to demonstrate a successful landing on the Moon has since been delayed. Following that test, a crewed lunar landing with either Starship HLS or Blue Moon is expected as part of the Artemis IV mission, now scheduled for early 2028.
Starship itself has been in privately funded development by SpaceX since the mid-2010s, but development of the HLS variant is being funded under NASA's Human Landing System contracts.
Description
Starship Human Landing System The Starship Human Landing System program includes the development and operational use of several Starship spacecraft variants by SpaceX, including the Starship HLS ship—optimized to operate on and in the vicinity of the Moon—as well as a Starship depot that will store propellant in Earth orbit, and the Starship tanker designed to fly multiple trips to orbit from Earth's surface to transport the necessary fuel and oxygen to the on-orbit depot. The concept of operations for a single lunar human landing mission will involve all three ship variants, as well as docking with another NASA-supplied spacecraft in near-rectilinear halo orbit (NRHO) around the Moon.
Unlike the standard Starship spacecraft, both the Starship HLS and Starship depot ships do not re-enter Earth's atmosphere, which allows for the removal of the spacecraft's atmospheric heat shield and flight control surfaces (fins). This reduction in mass allows for a smaller number of Starship tanker launches required for refueling once the spacecraft is in orbit. Like other Starship variants, Starship HLS and Starship depot are equipped with six Raptor engines, which are used during launch and the majority of the landing and ascent phases.
When within 100 meters of the lunar surface, the HLS variant is planned to use high‑thrust landing engines located in the mid‑body section of the spacecraft to avoid plume impingement with the lunar regolith, though these engines may not be needed. The landing engines burn gaseous oxygen and methane instead of the liquid oxygen and methane used by the Raptors. Electrical power is supplied by a band of solar panels around the circumference of the vehicle. HLS has the capability to loiter in lunar orbit for 100 days.
According to NASA, minimizing changes in vehicle configuration and making the design and development of Starship HLS as common as possible will benefit future Starship HLS builds by eliminating the need for additional testing, evaluation, and verification of different vehicle designs. NASA added this will also allow SpaceX to accelerate vehicle builds to help ensure availability and on-time delivery for mission integration.
Both the Starship HLS ship and the Starship depot—propellant depot that will remain in Earth orbit and collect/store the requisite propellant to refill the HLS ship before departure on a trans-lunar trajectory—will use a special purpose insulating tile that will provide micrometeoroid and orbital debris protection as well as insulate the depot from solar and Earth-thermal radiation in order to retain the cryogenic liquid oxygen and liquid methane for long-duration orbital storage. These in-space insulation tiles are different from the ceramic tiles used on Starships that must reenter Earth's atmosphere, such as the tiles on the Starship propellant tankers that will transport fuel/oxidizer cargo to fill the Starship depot.
Cargo variant In April 2024, NASA reported that work was underway on the cargo specific variant of the lander. NASA expects this variant to be ready and in service by Artemis VII. The cargo variant will be referred to by NASA as Human-class Delivery Landers and represent, as of June 2024, the highest capacity landers available to NASA under the current lunar exploration push.
Mission profiles Propellant transfer test campaign A Starship Propellant Transfer Demonstration remains optimistically scheduled for 2026. On-orbit refueling and storage learnings from LOXSAT may play a major role.
Lunar missions Prior to the launch of the HLS vehicle from Earth, a Starship configured as a propellant depot would be launched into an Earth orbit and then be partially or fully filled by between four and fourteen Starship tanker flights carrying propellant. As such, this spacecraft will be used in conjunction with the Starship booster (called Super Heavy) and two additional Starship spacecraft variants, "tanker" and "propellant depot", that were already planned prior to the NASA HLS contract.
Musk said in 2021 that between "four and eight" tanker launches would be required. The same year, the US Government Accountability Office (GAO) said that SpaceX would "require 16 launches overall", and in 2023, a NASA official estimated the number of Starship launches required for one lunar landing to be "in the high teens". In 2024, SpaceX vice president of customer operations estimated that the number of tanker launches would be "10-ish", though this number is subject to change. The launches will need to be in rapid succession in order to maintain schedule constraints and limit the loss of liquid cryogenic propellants due to boiloff.The Starship HLS vehicle would then launch and rendezvous with the already-loaded propellant depot and refuel before transiting from Earth orbit to Lunar orbit.
Once HLS is in a near-rectilinear halo orbit (NRHO) around the Moon, an Orion spacecraft would be launched by a Space Launch System rocket and dock with the waiting Starship HLS lander in order to transfer passengers. After two to four of the crew had transferred into the HLS, it would depart and descend to the lunar surface. After lunar surface operations, Starship HLS will lift off from the Moon and return to lunar orbit to rendezvous with Orion. The crew would then transfer back to Orion and depart for Earth. Although not confirmed yet, Starship HLS could, in theory, be refueled in orbit to carry more crews and cargo to the surface of the Moon.
History Background In the early 2010s, NASA originally planned to use the Orion spacecraft and the Space Launch System (SLS) to land astronauts on the Moon. The design of the Orion capsule was inherited from the Constellation program, a defunct crewed lunar program of the 2000s. The SLS is a launch vehicle NASA developed as replacement for the Space Shuttle following its retirement in 2011, and to bolster Shuttle-related jobs that would otherwise have been lost. The SLS is unable to launch Orion into low lunar orbit like the Saturn V rocket did during the Apollo program.
The closest to the Moon SLS can launch Orion is into NRHO, an elliptical orbit that approaches the Moon. Descending to the Moon from NRHO requires considerably more energy than from a low lunar orbit and only allows a descent once every 6.5 days.
To address these challenges, NASA issued a request for proposals to commercial companies to develop a Human Landing System (HLS) in 2018. HLS lunar landing vehicles should be able to travel from Earth to NRHO, where they would meet with Orion, land on the Moon, and later return to NRHO to dock with Orion once again.
SpaceX had plans to develop a large interplanetary vehicle since the 2000s to fulfill their goal of colonizing Mars. In response to NASA's request for Human Landing System proposals, SpaceX adapted the design of their base Starship vehicle into a variant suited to carry NASA's mission of landing two astronauts on the Moon from NRHO: the Starship HLS.
Selection of the lander
The initial NASA-contracted design work for a NASA-specific Starship variant started in May 2020 when SpaceX was selected for an Artemis III program award called "Option A", with selection and funding for full-development occurring in April 2021, when Starship HLS was selected by NASA to land "the first woman and the next man" on the Moon for the Artemis III mission (subsequently delayed by NASA until Artemis IV).
Selection of the Starship lunar lander In 2021, NASA entered into a firm fixed-price contract with SpaceX valued at , spread over a number of years to develop and manufacture the Starship HLS lunar lander, as well as the execution of two operational flights: an uncrewed demonstration mission and a crewed lunar landing.
Starship HLS was first made public when it was initially selected by NASA in April 2020 for a design study as part of their Artemis program, which aims to land humans on the Moon. SpaceX was one of three teams selected to develop competing lunar lander designs for the Artemis program over a year-long period starting in May 2020.
The other landers in consideration were Dynetics HLS, proposed by aerospace manufacturer Dynetics, and the Integrated Lander Vehicle, proposed by a team led by Blue Origin. NASA intended to later select and fund at most two of these landers to continue to perform initial demonstration flights.
On 16 April 2021, NASA selected only Starship HLS for crewed lunar lander development plus two lunar demonstration flightsone uncrewed and one crewedno earlier than 2024. The contract was valued at over a number of years. Two NASA Artemis astronauts are to land on the first crewed Starship HLS landing. NASA had previously stated that it preferred to fund development of multiple Human Landing System proposals with dissimilar capabilities; however, "only one design was selected for an initial uncrewed demonstration and the first crewed landing, due to significant budget constraints" for the human landing system program imposed by the US Congress. NASA stated that the unselected proposalsDynetics HLS and Blue Origin Integrated Lander Vehicleas well as landers from other companies would be eligible for later lunar landing contracts.
Opposition by competing companies
On 26 April 2021, Blue Origin and Dynetics separately filed formal protests of the award to SpaceX at the US Government Accountability Office (GAO). On 30 July 2021, the GAO rejected both protests and found that "NASA did not violate procurement law" in awarding the contract to SpaceX, who bid a much lower cost and more capable human and cargo lunar landing capability for NASA Artemis. Soon after GAO rejected the appeal, NASA made the initial $300 million contract payment to SpaceX. The protest action delayed NASA from authorizing work on the contract, and thus delayed the start of work by SpaceX for 95 days. Blue Origin produced infographic posters that highlight the complexity of Starship HLS, for example the fact that on orbit refuelling with cryogenic fuels like that Starship HLS uses has never been demonstrated, while stating that its design uses "proven technology".