# Starship HLS

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 on the Moon.
The mission plan calls for a Starship launch vehicle 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 astronauts will transfer from Orion to HLS, which will then descend to the lunar surface for a stay of approximately 7 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 is planned for 2025 to demonstrate a successful landing on the Moon. Following that test, a crewed flight is expected to occur as part of the Artemis III mission, no earlier than mid-2027. NASA later contracted for an upgraded version of Starship HLS to be used on the Artemis IV mission.
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) nearer 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. 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.$^{:50:30}$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 (MMOD) 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.$^{:7:58–8:18}$

### 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 (HDL) 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

As of 2024, NASA expects that SpaceX will begin a propellant transfer test campaign in approximately March 2025, and complete it during summer 2025. This will require multiple starship launches, and will culminate with a ship-to-ship propellant transfer demonstration prior to the NASA-required Starship HLS Critical Design Review (CDR) in late-summer 2025. The test campaign will aim for a biweekly launch cadence from a single launch mount, with a stretch goal to obtain weekly launches using two pads.$^{:4:21–5:44}$

### 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 to 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 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 around the moon, an Orion spacecraft would be launched by a Space Launch System rocket and dock with the waiting Starship HLS lander$^{:4,5}$ or NASA lunar Gateway space station, in order to take on passengers before descending to the lunar surface and return them after ascent.After two to four of the crew had transferred into the HLS, it would depart and descend to the lunar surface.$^{:4,5}$ After lunar surface operations, Starship HLS will lift-off from the Moon and return to lunar orbit to rendezvous with Orion.$^{:4,5}$ The crew then transfers back to Orion and departs for Earth. Although not confirmed yet, Starship HLS could, in theory, be refueled in orbit to carry more crews and cargo to the surface.

## 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 near-rectilinear halo orbit (NRHO), an elliptical orbit that approaches the Moon. NASA's planned Lunar Gateway station is also slated to be loitered in that orbit in order to be serviceable by Orion. 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 in its plan 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.

#### Selection of the Starship lunar lander

In 2021, NASA entered into a firm fixed-price contract with SpaceX valued at US$2.89 billion, 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 flights – one uncrewed and one crewed – no earlier than 2024. The contract was valued at US$2.89 billion 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 proposals – Dynetics HLS and Blue Origin Integrated Lander Vehicle – as 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".
On 13 August 2021, Blue Origin filed a lawsuit in the US Court of Federal Claims challenging "NASA's unlawful and improper evaluation of proposals". Blue Origin asked the court for an injunction to halt further spending by NASA on the existing contract with SpaceX, and NASA stopped work on the contract on 19 August, after SpaceX had been allowed to work on the NASA-specific parts of Starship HLS for just three weeks since the work had been previously halted in April. Reactions to the lawsuit were negative, with many criticizing Blue Origin for causing unnecessary delays to the Artemis program.
On 4 November 2021, the court granted the federal government's motion to dismiss the case, and NASA announced that it would resume work with SpaceX as soon as possible.

#### Artemis IV contract ("Option B")

On 23 March 2022, NASA announced it would be exercising an option under the initial SpaceX HLS contract, known as Option B, that would allow a second-generation Starship HLS design to conduct a demonstration mission after Artemis III.
On 15 November 2022, NASA announced the Option B award of US$1.15 billion, and announced that this crewed landing is to occur as part of Artemis IV. The flight will include docking with the Lunar Gateway. The Option B HLS will meet NASA's requirements for a "sustainable" HLS. These include the ability to support four crew members and delivering more mass to the surface.

#### Subsequent related NASA contracts

After NASA awarded the Option A contract to SpaceX, Congress subsequently directed NASA to extend the HLS program for a second sustainable HLS design, with the requirement that it must be from a second company, and not SpaceX. NASA responded by creating "Appendix P", and specified a lander that would be used for Artemis V as its crewed demonstration flight. In May 2023, Blue Origin was awarded $3.4 billion by NASA to develop their Blue Moon lunar lander. NASA intends to allow Starship HLS option B and the Blue Moon lander to compete for Artemis missions after Artemis V.

### 2021–2023

In 2021, the NASA Office of Inspector General (OIG) warned that the HLS development schedule was unrealistic when compared to other major NASA space flight programs.$^{:14–15}$ Stating that space flight programs in the prior 15 years had taken on average 8.5 years from contract award to first operational flight, while the HLS Program was attempting to do so in about half that time.$^{:14–15}$ By contrast, NASA OIG noted that the Apollo Lunar Lander took approximately 6 years from contract award to its launch on the Apollo 11 mission while receiving "substantially higher levels of funding" adjusted for inflation.$^{:14}$ Based on the HLS base period contract award date (May 2020) and the average delay for recent major NASA space flight programs, they estimated that the HLS Program could face up to 3.4 years of delays before operational flights.$^{:16}$
In June 2023, NASA's chief of exploration systems development in the HLS development office, Jim Free, said that the Starship HLS's critical design review, required before further funds from the contract could be released to SpaceX, had been delayed until SpaceX completes an in orbital refueling demonstration mission. The head of NASA's moon and Mars exploration strategy said that the delay of Artemis III from 2025 to 2026 was partly due to "development challenges" with their contractors (SpaceX and Lockheed Martin).
In November 2023 the United States Government Accountability Office, in their report to Congress, outlined several challenges that the Artemis program was facing in development. They noted that as of September 2023 the [NASA] HLS program had delayed 8 out of 13 key events by at least 6 months, with 2 events being delayed to the year of launch (2025 at the time). The GAO also identified the development of the Raptor engine as a "top risk" for the program and its 2025 timeline, although SpaceX considered the technology behind the Raptor engine to be relatively mature. The GAO noted that SpaceX had made limited progress maturing the technologies needed for in-orbit refueling and cryogenic propellant storage. The GAO concluded in their report to Congress that the Artemis III crewed lunar landing is unlikely to occur in 2025, and that a launch date in early 2027 is more likely.
NASA astronauts tested the elevator concept (crew transfer between the cabin of Starship HLS and the lunar surface) in December 2023.

### 2024–present

In January 2024, NASA and SpaceX said that the uncrewed Starship HLS lunar landing and ascent test, was expected to take place in 2025, with Artemis III being delayed to no earlier than September 2026. The delay was in part due to issues with Orion's heatshield during Artemis I.
In February 2024, SpaceX had fully tested the life support system, and NASA performed a full-scale test of the Starship HLS to Orion – and later Gateway – docking transfer system. The same month, NASA said SpaceX had accomplished over 30 HLS-specific milestones by defining and testing hardware needed for power generation, communications, guidance and navigation, propulsion, life support, and space environments protection.
On 14 March 2024, SpaceX successfully tested ship-internal cryogenic propellant transfer on Integrated Flight Test 3. In April 2024, NASA reported that work was underway on a cargo-specific variant of the lander. NASA expects this variant to be ready and in service by Artemis VII.
In a meeting of the United States House Science Subcommittee on Space and Aeronautics on 10 September 2024, Brian Babin and Haley Stevens expressed concerns that the pace of license processing under the FAA's Part 450 commercial launch and reentry regulations could impact the Artemis program since both Blue Origin and SpaceX HLS landers will launch using commercial licenses. Following a further two-month delay by the FAA of Starship flight test 5, SpaceX said government paperwork prevented it from flying Starship quickly to meet commitments to the Artemis program.
In October 2024, NASA stated that the flight test campaign for the ship-to-ship propellant transfer demonstration was slated to start around March 2025 with test completion over the summer when the design certification review by NASA is to take place.$^{:3:56–4:24}$

## Program architecture

NASA is utilizing a very different approach in contracting for Starship HLS from the legacy cost-plus program process NASA has used on most programs before, including on the Space Launch System also planned to be used with Artemis. Kent Chojnacki, the deputy program manager for NASA's human spaceflight office, said the contract structure is different and "two completely different approaches." On the SpaceX contract for the initial landing, there are just 27 system requirements. NASA has kept it "as loose as possible while going thru and dictating all the safety standards we'd want, we agreed to all the design and construction standards up front, we agreed to all of the things they would do to ensure the safety of the human element up front, and then we let them go and run." SpaceX is working to a firm fixed price contract and is only paid when the program criteria are met.$^{:0:55–3:51}$