NASA Updates on Starship Refueling, as SpaceX Prepares Flight 4 of Starship

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In a recent update to the NASA Advisory Council Human Exploration and Operations Committee, the agency provided updates on several key aspects of the Artemis I through IV missions. This included updates on Starship timelines and efforts as SpaceX readies to conduct the final tests of the fourth Starship Flight Test.

NASA Advisory Briefing

Amit Kshatriya, Deputy Associate Administrator of NASA’s Moon to Mars program, elaborated on the agency’s observed progress of the Human Landing System (HLS) efforts undertaken by SpaceX.

A render of the Starship HLS, on the Moon. (Credit: SpaceX)

Starship is contracted to be the designated landing system for the Artemis III mission. The planned mission for September 2026 aims to return humans to the surface of the Moon and would be the first crewed lunar landing since Apollo 17 in December 1972.
In March 2024, the company conducted another test flight of the Starship system as part of its development program to move Starship to operational status. NASA noted they have been encouraged by the progress made on Flight 3.

“They (SpaceX) conducted their third integrated flight test and successfully completed a full-duration burn during ascent. So that was a significant milestone.

“In addition, SpaceX and NASA recently performed full-scale qualification testing of the docking system that will connect the Starship human landing system with Orion and, later in future missions, with Gateway on those missions.”

The docking system is a critical element that will be utilized to dock with the crewed Orion capsule after it is launched by an SLS rocket to bring the crew down to the surface of the Moon.

Regarding future flights of Starship, NASA indicated that SpaceX has already analyzed the data from the March test flight and implemented numerous corrective measures to Flight 4’s stack of Ship 29 and Booster 11.

This launch is planned for as early as May but no later than the end of May.

Kshatriya then expanded the discussion beyond the next few Starship flights and talked about the required technologies for a fuel depot in orbit and the in-orbit capabilities needed to transfer fuel.

“We need an instance of the ship that is essentially long, has the endurance to stay in orbit long enough for the sequence to work.

“So, we need a ship that has at least three to four weeks of endurance in orbit. That endurance is gained through augmented power system capability, augmented battery capacity, full insulation of the cryogenic systems, vacuum jacketing of all the lines, et cetera, to make sure that the cryogens that are being stored or are meant to be stored don’t boil off.”

The challenges of a cryogenic ship in orbit include the need to prevent boil-off from the stack. To facilitate the journey to the Moon’s surface, Starship will have to be refueled. For this, the company plans to refuel a depot in low-Earth orbit (LEO), which would be resupplied by several tanker Starships. The HLS Starship would then dock with this depot before departing for the Moon.

The Starship HLS Prop Transfer Demo is associated with this, a multi-phase operation involving SpaceX and NASA to develop all the needed technologies to conduct such an operation. NASA detailed the steps on a chart.

While the initial “Tipping Point Propellant Transfer Demo” was conducted during the last flight, and a flight system review was conducted afterward, a few more steps are still in progress before refueling can be conducted between Starships. NASA also stated here that the demo that SpaceX conducted on Flight 3, which involved the transfer of liquids between two tanks on the same Starship, was successful by all accounts.
SpaceX is developing docking mechanisms, navigation, disconnects, and hot gas thrusters, all of which are identified on this chart as crucial steps before conducting a Ship-to-Ship propellant transfer demo in 2025.

In this final demo mission, SpaceX would launch two Starship full stacks from Starbase. The target, a demo for the depot, would launch first and enter orbit. The chaser, the second Starship to launch in this demo, would then launch to catch up to the target, perform active navigation to the target, and demonstrate a propellant transfer to it. Both ships would then, after the mission, perform a deorbit burn.

Starbase has already begun the groundwork on a second tower, with the sections already waiting to be stacked.

A render of how Starbase will look with the two towers needed for this test. (Credit: Render: Jay DeShelter/NSF Photo: Sean Doherty/NSF)

A SpaceX mission overview was presented, which illustrates the mission flow for this mission. It is likely that such a mission would feature two Starship full stacks on both pads at Boca Chica, Starbase. While one of these pads is already operational, the other is still in early construction and not expected to be finished before the end of the year.

Currently, according to Kshatriya, SpaceX is optimistic that once both ships are docked in such a scenario, all that will be needed is the firing of some settling thrusters, as the pressure difference between the two will then initiate the propellant transfer. However, he also alludes to the possibility that pumps could be required should this not go according to plan.

Preparing for Flight 4

Meanwhile, SpaceX is preparing to conduct the fourth Starship Flight Test. The vehicle’s components, Ship 29 and Booster 11, are currently back at the Starbase Production Site to undergo final work before a potential rollout, integration, wet-dress rehearsal (WDR), and launch.

Ship 29 is currently undergoing ongoing work on its thermal protection system. The tiles are essential to withstand the extreme heat during reentry from LEO. While Starship 28 in the recent flight test reached this stage, the system could not be fully verified as the ship experienced a heavy roll in its flight trajectory, causing SpaceX to lose attitude control, resulting in the loss of the vehicle.

Booster 11 is currently stored in the Mega Bay facility, awaiting its hot staging ring. The hot staging ring allows exhaust to escape during the staging maneuver of Starship. The designated hot staging ring for Booster 11 is stored outside of the production facilities and was spotted by NSF’s Mary (@bocachicagal).

Cameron County also announced several road closures, which could be related to imminent testing activity at Starbase. A rollout and a test closure are scheduled for the upcoming week. On April 29, Highway 4 will be closed between 7 p.m. and 11 p.m. local time to allow for the roll of a vehicle to the launch site. The following day, a closure from 7 a.m. to 7 p.m. will allow for non-flight testing activities.

While this may, of course, pertain to the upcoming flight stack, given the duration parameters, SpaceX is more likely to want to move the testing of Ship 30 or Booster 12 ahead of the fourth Starship flight campaign.

Ship 29 in the High Bay, still missing tiles. (Credit: Mary/BocaChicaGal)

This is similar to the approach that SpaceX has already taken during the second flight campaign, where Ship 29 was attempted to be tested before the flight of the second stack. This approach resulted in the completion of a Spin Prime test ahead of the flight campaign.

NSF understands that the third Starship Flight Test remains on track for the first two weeks of May, with regulatory and technical readiness nearing completion. On the regulatory side, a SpaceX-led mishap investigation into the problems during Flight 3 needs to be concluded before SpaceX can apply for a modification to the launch license needed for Flight 4.

Lead Image: Starship Full Stack – via Mary (@bocachicagal).

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