GAO Reports NASA’s Lunar Gateway May Have "Stack Controllability." Issue With Starship

Originally slated for launch in 2022, NASA's Lunar Gateway project has experienced significant delays; and according to a recent report from the US Government Accountability Office (GAO), The National Aeronautics and Space Administration (NASA) now anticipates the launch of the Gateway's initial elements no sooner than December 2027.

NASA currently plans to incorporate the Gateway into the Artemis IV mission, scheduled for September 2028. Unfortunately, the projected launch date for the Gateway is already three months behind the schedule needed to support Artemis IV, the second mission intended to land humans on the Moon.

NASA has committed to launching the first components of the Gateway—the Power and Propulsion Element (PPE) and the Habitation and Logistics Outpost (HALO) by December 2027 at a cost of $5.3 billion.

The Gateway Program plans to update the analysis it used to inform its cost and schedule commitments at a fall 2024 program-level review. This will help determine the feasibility of the Artemis IV mission date. To reach lunar orbit and ensure all systems work as planned, the PPE and HALO need to launch at least 12 months before the Artemis IV mission, or 3 months earlier than Gateway's current committed date.

NASA officials said the program plans to work to an accelerated, to-be-determined date that would provide more schedule flexibility.

The Gateway program's projects—including PPE and HALO—made varying degrees of progress over the last year. However, the PPE and HALO projects face several significant challenges.

A Mass Issue

The combined mass of the Lunar Gateway's PPE and HALO is greater than their mass target. Mass is one of many factors that the program considers in its overall design. If they cannot meet their mass target, it may affect their ability to reach the correct lunar orbit.

The program has not yet documented an overall mass management plan, which would describe the program's mass reduction approach and priorities for key trade-off decisions. Documenting and communicating this plan will help to ensure that the program and its projects agree on how to address the mass challenge.

NASA held two reviews in 2023 to break down high-level Artemis exploration objectives and goals into the programs, projects, or systems needed to achieve them. So far, NASA has used these reviews to assign roles to the Gateway that align to goals of the earlier Artemis missions, like returning humans to the moon.

NASA plans to use upcoming reviews to make key decisions related to Mars missions, which could inform how NASA might use the Gateway in the future.

Why GAO Did This Study

A House Report contains a provision for GAO to continue reviewing NASA's lunar-focused programs. This report focuses on the Gateway program and its NASA-led development projects.

It addresses (1) the Gateway program's plans to update the initial capability's cost and schedule analysis; (2) the extent to which the Gateway program made progress with its U.S.-led projects needed for the Artemis IV mission and is addressing project risks; and (3) NASA's process for determining how it will use the Gateway beyond Artemis IV, including for Mars missions.

GAO analyzed NASA documentation and interviewed officials on the Gateway program's cost, schedule, risks, and role in the Artemis architecture.

GAO Recommendations

GAO is making one recommendation, that NASA should ensure that the Gateway program documents and communicates an overall mass management plan before its next program-level review. NASA agreed with GAO's recommendation.

The GAO report includes a detailed sequence of events necessary for the Gateway to participate in the Artemis IV mission:

• Launch the initial segments of the Gateway, including a power and propulsion module and a habitation module, into a halo orbit around the Moon.

• Launch a SpaceX Dragon XL vehicle to deliver supplies to the Gateway.

• Launch multiple SpaceX Starships to refuel a Lunar Starship, which will then dock with the Gateway.

• Launch a NASA Space Launch System (SLS) rocket carrying four astronauts inside an Orion spacecraft, along with another Gateway module.

• After launch, Orion separates from the SLS rocket and docks with the International Habitat module.

• Orion tugs the International Habitat to the Gateway and docks, allowing the crew to enter the Gateway.

• Two crew members board the Lunar Starship and descend to the Moon for a six-day mission.

• The Lunar Starship returns to the Gateway, and the four astronauts return to Earth inside Orion.

The GAO report acknowledges the complexity of this plan, noting significant schedule risks.

"This mission will be complex because NASA will need to coordinate across seven NASA programs, multiple contractors that support those programs, and international partners to execute the mission. It will also be the first launch of an upgraded version of the Space Launch System rocket." - GAO

The Gateway program is grappling with several technical challenges.

Network Chip Issue Could Result In Loss Of Control Of Gateway

One major issue is a defective network chip that is crucial for communication throughout the lunar space station. The GAO report highlights the severity of this problem.

"For example, these defects could lead the flight computers to unexpectedly restart. If the network is not functioning properly, it could result in loss of control of the Gateway. Program officials are also concerned that they might identify more defects with the communication network, based on the number found already." - GAO

Gateway May Not Be Able To Maintain Orientation With Starship Docked

Another significant concern is "stack controllability." Given that SpaceX’s Lunar Starship is substantially more massive than the Gateway, maintaining the proper orientation of the space station when the Starship is docked could be problematic.

"Program officials estimate that the mass of the lunar lander Starship is approximately 18 times greater than the value NASA used to develop the PPE’s controllability parameters. According to NASA’s system engineering guidance, late requirements and design changes can lead to cost growth and schedule delays." - GAO Report

Mars Mission Support May Not Be Possible

The GAO report casts doubt on the utility of the Lunar Gateway for Mars missions.

Previously, NASA officials had suggested that the Gateway could serve as a staging area for spacecraft and propellant for human missions to Mars. However, the "stack controllability" issue could severely limit the Gateway’s ability to host large Mars transit vehicles.

Additionally, the Gateway's planned 15-year lifespan may not be sufficient for sustaining Mars missions.

"The Gateway could have exceeded its planned 15-year on-orbit life as early as 2042 when crewed missions to Mars are potentially just beginning." - GAO Report

Overall, the GAO report suggests that the Lunar Gateway is significantly behind schedule and may have limited utility for both lunar and Mars missions.

The complexity of the project and its developmental difficulties present substantial challenges as NASA simultaneously endeavors to establish a sustainable lunar surface program. Despite these issues, NASA continues to push forward, aiming for a launch within the next decade.