At NASA's Aerospace Safety Advisory Panel (ASAP) meeting on October 22, 2026, panel member Charlie Precourt reportedly said the latest estimate of launches needed to refuel Starship for a Moon landing is "around 22." Elon Musk replied on X the same day: "That's way too high. Actual number will be more like 6 to 8." According to a 2026 NASA paper, the final number of tanker launches will be informed by SpaceX's upcoming large-scale propellant transfer test, which will measure thermal properties and boil-off rates.
3-line summary
- At NASA's Aerospace Safety Advisory Panel (ASAP) meeting on October 22, 2026, an estimate of "about 22" refueling launches for a Starship Moon landing was reportedly presented.
- Elon Musk replied on X to the reporter who shared it: "That's way too high. Actual number will be more like 6 to 8." (21:12 UTC, October 22)
- A NASA paper from October 2026 says the number of tanker launches will be set after a large-scale in-orbit propellant transfer test measures heat leak and boil-off. Both numbers are predictions made before that test.
Background: why add fuel in space?
A rocket spends most of its fuel carrying fuel. A rocket moves by throwing hot gas backward. But the fuel it carries at liftoff is itself heavy cargo, so in the first minutes it burns fuel to lift fuel it will use later. That is why adding more fuel does not raise the achievable speed in proportion. The rocket equation says the change in speed depends on the logarithm of "mass at start ÷ mass when empty." Because it is a logarithm, doubling that ratio does not double the speed.
Just reaching Earth orbit uses up most of the fuel. As a common rule of thumb, getting from the ground to low Earth orbit (a few hundred kilometers up) takes a speed change of a little over 9 km/s. Landing on the Moon and returning to lunar orbit takes several km/s more. Doing it all from the ground in one go is hard even for a huge rocket. So SpaceX's plan first puts the lander (Starship HLS) into Earth orbit, fills it up there, and only then heads to the Moon. Think of it as filling the tank at the gas station near home before a long road trip.
The propellants are extremely cold liquids. Starship burns liquid methane and liquid oxygen. Both are gases at normal temperatures; to stay liquid, methane must be kept below about −162 °C and oxygen below about −183 °C. In space, sunlight and the vehicle's own heat slowly leak into the tanks. Part of the liquid warms up and turns into gas ("boil-off"), so the usable propellant shrinks. The longer it waits, the more it loses.
The count comes from simple multiplication and division. Say the vehicle needs 100 units of propellant in orbit, and one tanker delivers 10. With no losses, that is 100 ÷ 10 = 10 flights. If each transfer loses 2 and boil-off takes a bit more while waiting, only about 8 arrives per flight, so 100 ÷ 8 ≈ 13 flights. If a tanker could carry 15 instead, 100 ÷ 15 ≈ 7 flights. (These numbers are illustrations, not real values.) The gap between "22" and "6 to 8" is a gap in the inputs to this formula.
What happened
NASA has an Aerospace Safety Advisory Panel (ASAP) of outside experts who review safety. According to the Federal Register, its fourth quarterly meeting of 2026 was held by phone on October 22 (1:30–3:00 p.m. Eastern), and the agenda included "Updates on Artemis Programs."
At the meeting, panel member and former NASA astronaut Charlie Precourt said, "I think the last estimate is around 22 flights," for refueling launches to support a Starship Moon landing, as reported by Eric Berger of Ars Technica. Precourt reportedly flagged the numerous required fuelings for the lander as something to keep an eye on.
When Berger posted this on X, Musk replied:
| Content | |
|---|---|
| Estimate cited at the panel (reported) | About 22 flights |
| Musk's reply (X, 21:12 UTC, October 22, 2026) | "That's way too high. Actual number will be more like 6 to 8." |
Why it matters
First, the number of launches drives the Moon-landing schedule. Tankers launch one at a time and transfer propellant in orbit in sequence. Triple the count and you lengthen the preparation period and the boil-off along with it. It is one of the biggest numbers in the whole mission timeline.
Second, the number has not been measured yet. A paper by NASA Human Landing System (HLS) program staff, presented at the International Astronautical Congress in October 2026, says SpaceX is working toward a long-duration orbital test of Starship that will end with a large-scale cryogenic propellant transfer between two Starships. That test will measure thermal properties and boil-off rates, among other things, "to inform the eventual number of tanker launches." In other words, both the panel's estimate and Musk's figure are pre-test predictions.
How it works: the flow of propellant to the Moon
According to the NASA paper, SpaceX's Moon landing uses three Starship variants.
| Vehicle | Role (from the NASA paper) |
|---|---|
| Depot | Launches first and waits in low Earth orbit for tankers |
| Tanker | Launches repeatedly, docks with the depot, and transfers liquid methane and liquid oxygen into the depot's matching tanks |
| Starship HLS (lander) | Takes on propellant from the depot and heads to the Moon, where crew board it in lunar orbit and descend to the surface |
In order: (1) launch the depot, (2) launch tankers many times to fill it, (3) launch the lander and fill it from the depot, (4) the lander departs for the Moon. The "22" in the reports refers mainly to the launches in step (2).
This is where boil-off matters. The longer the gap between tanker launches, the more the stored propellant shrinks while waiting, and the more tankers are needed to make up the loss. So four levers cut the count: carry more per flight, lose less per transfer, insulate better to reduce boil-off, and launch more often.
In my view, it is easiest to read Musk's "6 to 8" as the number if these levers work well, and the panel's "about 22" as an estimate with margin built in.
NASA also requires an uncrewed landing demonstration first. According to the paper, the lander must autonomously touch down within 100 m of the target, send data back to Earth for at least two hours after landing, and relight its main engine on the Moon.
How we got here
- April 2021: NASA selected SpaceX's Starship HLS as the Artemis lunar lander.
- May 2023: NASA selected Blue Origin as a second lunar lander provider.
- 2026: NASA revised the plan. Artemis III (planned for 2027) became a test in Earth orbit in which Orion docks with test articles of both companies' landers. The first crewed landing is Artemis IV, planned for early 2028. The NASA paper says the agency is also working toward a second landing, Artemis V, in late 2028, and will assign providers to missions later.
- October 22, 2026: The "about 22" estimate was reportedly presented at the ASAP meeting, and Musk replied "6 to 8."
NASA's Artemis IV page says four astronauts will launch in Orion, and two will board a lander in lunar orbit and spend about a week near the Moon's South Pole.
Takeaways for reading the news
- Read any "number of flights" together with its inputs: The count swings with how much a tanker carries, transfer losses, boil-off, and launch spacing. Comparing counts alone does not tell you which is right.
- Separate pre-test estimates from test results: NASA says the count will be informed by the large-scale propellant transfer test. When that test flies, its numbers will be the real news.
- A common misunderstanding: "22 flights" does not mean 22 trips to the Moon. Almost all of them only carry propellant to low Earth orbit. Only the lander goes to the Moon.
A question to follow up
How do you "pour" a liquid colder than −160 °C from one vehicle to another in weightlessness? Without gravity, the liquid does not settle at the bottom of the tank; it floats around. How to solve that is one of the key things to watch in the propellant transfer test.
Read next
- What Is Starship? The Two-Stage Design with Super Heavy, Size, Engines and Reuse
- Starship Flight 15 aims for a "dual catch" of booster and ship (reuse is what shortens the time between launches)
- How Much Does a Rocket Launch Cost? The Cost Breakdown Starting From Materials
Sources
- Federal Register, "Aerospace Safety Advisory Panel; Meeting" (2026-19188, September 18, 2026; fourth quarterly meeting on October 22) → https://www.govinfo.gov/content/pkg/FR-2026-09-18/html/2026-19188.htm
- Eric Berger (Ars Technica) on X (October 22, 2026) → https://x.com/SciGuySpace
- Elon Musk on X (21:12 UTC, October 22, 2026) → https://x.com/elonmusk/status/2113377866478231647
- NASA, "NASA's Human Landing System: Demonstrating the Capability to Land Artemis Astronauts on the Moon by 2028" (IAC-26-B3.1, October 2026) → https://ntrs.nasa.gov/api/citations/20260008717/downloads/HLS%20IAC%202026%20FINAL.pdf
- NASA, "Artemis IV" → https://www.nasa.gov/mission/artemis-iv/
- Teslarati, "The Starship moon landing number NASA and Elon Musk can't agree on" (October 23, 2026) → https://www.teslarati.com/elon-musk-nasa-starship-moon-landing/
*The meeting date and agenda were confirmed in the Federal Register, Musk's reply on X, and the refueling architecture and schedule in NASA's paper and mission page (as of 2026-10-23). The "about 22" remark at the panel is based on press reports.*
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