NASA Artemis IV Starship Refueling Plan Explained: Depot, Tankers and the Final Tanking Orbit

Illustrative image: the Starship 6 launch plume seen from the International Space Station in November 2024 — not the Artemis IV lander, which has not flown yet. Image: NASA / Don Pettit, via Wikimedia Commons (public domain).

TL;DR — NASA Artemis IV starship refueling plan explained in one line: before any astronaut can land on the Moon in 2028, SpaceX must first build a floating petrol station in Earth orbit — a Starship depot filled by multiple tanker flights, topped up twice — because a Starship launched fully fuelled could never reach the Moon at all.

📌 KEY HIGHLIGHTS

• The mission: Artemis IV, targeted for 2028, is NASA's first crewed lunar landing since Apollo 17 in 1972 — four astronauts aboard Orion, two descending to the lunar south pole.
• The plan: a Starship depot is launched to low Earth orbit, filled by multiple tankers, then refills the lander twice — once in low Earth orbit and once in a higher "final tanking orbit" — before the lander meets Orion.
• The number nobody agrees on: NASA's safety panel puts the tanker campaign at around 22 flights; SpaceX chief Elon Musk says 6–8. NASA's own graphic just says "(multiple)".
• The catch: nothing here is settled. If SpaceX cannot prove orbital refuelling or fly an uncrewed Moon landing by the end of 2027, NASA can switch Artemis IV to Blue Origin's Blue Moon lander instead.
• Why it matters: this is the single hardest new technology in the whole Artemis programme — cryogenic fuel has never been transferred between spacecraft at this scale.

NASA Artemis IV starship refueling plan explained: the full sequence, step by step

NASA laid out the sequence in its Artemis update on 23 October 2026, and it was freshly explained on 3 November 2026 as Space.com and other outlets walked through the agency's mission graphic. Artemis IV is the programme's first crewed landing attempt, but the landing itself is almost the last step in a long orbital choreography. Here it is, in order:

Step	What happens	Why
1. Depot launch	A modified Starship — the depot, essentially a giant insulated tank with docking ports — launches into low Earth orbit (LEO).	Somewhere has to hold the fuel before the lander arrives.
2. First fill	Multiple tanker Starships launch, dock with the depot and transfer super-chilled liquid methane and liquid oxygen. NASA's graphic labels this "(multiple)" — no number given.	One tanker cannot carry a Moon mission's worth of propellant.
3. Lander's first pit stop	The Starship lunar lander launches with near-empty tanks, docks with the depot in LEO and takes its first fill.	The lander arrives light, then fuels up in orbit.
4. Climb to the final tanking orbit	The lander undocks and raises its altitude to what NASA calls the "final tanking orbit" (FTO).	Staging the last fill higher up saves propellant on the Moon leg.
5. Depot refilled — again	Back in LEO, another round of multiple tankers refills the depot, which then travels up to meet the lander in the FTO.	The depot needs a second load for the second fill.
6. Final fill	Depot and lander dock a second time, in the FTO, for the last fuel transfer.	Only now is the lander fully fuelled for the Moon.
7. Rendezvous with Orion	The lander climbs to high Earth orbit to meet Orion, launched aboard NASA's SLS rocket with four astronauts. The combined stack heads for the Moon and enters low lunar orbit.	Staggering the order this way gives NASA flexibility on when SLS launches.
8. Landing	Two astronauts transfer to the lander and descend to the lunar south pole; two remain aboard Orion. After surface work, the lander returns its crew to Orion for the trip home.	The Apollo pattern, with a vastly bigger lander.

Note the odd detail in step 7: NASA's outline shows SLS launching Orion before Starship gets its final fuel. The agency says that deliberately staggered order reduces the total propellant SpaceX needs, partly because it takes Orion directly into low lunar orbit rather than the higher orbit used in earlier mission concepts. None of this is set in stone — it is the baseline concept, not a flown procedure.

Why Starship cannot just fly to the Moon fully fuelled

This is the rocket equation at its most unforgiving. A Starship loaded with enough propellant to fly to the Moon, land and come back would be too heavy to launch: the fuel needed to lift that fuel needs yet more fuel. Apollo dodged the problem with a small lander and a single giant rocket. Starship is a far bigger vehicle, so SpaceX's answer is to launch it nearly empty and fill it in orbit — the same idea as air-to-air refuelling, except the fuel is cryogenic methane and oxygen at hundreds of degrees below zero, it boils off while it sits in orbit, and transferring it between two spacecraft in microgravity has never been done at this scale.

Illustrative image: a Super Heavy booster caught by the Mechzilla tower arms in October 2024. Rapid, reusable booster recovery is what makes a multi-launch tanker campaign even conceivable. Image: Wikimedia Commons, CC BY licence.

That is also why the tanker count matters so much. Every tanker flight is a full Starship launch — with its own rendezvous, docking, transfer and booster recovery — and a delay anywhere in the chain compounds across the whole campaign. SpaceX is targeting its first ship-to-ship cryogenic transfer demonstration in early 2027, with one Starship launching from Starbase in Texas and another from Kennedy Space Center in Florida, according to NASA officials cited in recent reporting. The uncrewed Starship lunar landing demonstration is targeted for the second half of 2027. Until those two demos fly, the whole Artemis IV plan is a diagram.

The number nobody can agree on: 6–8 or 22?

The tanker estimate has drifted for years, and the spread tells you how uncertain the inputs still are — mainly how much propellant each tanker actually delivers to orbit, and how much boils off during storage and transfer:

Who said it	Estimate	Basis
US Government Accountability Office (2021)	Up to 16	Early audit of the Starship landing architecture.
NASA Human Landing System programme (2023)	High single digits to low double digits	Then-director Lisa Watson-Morgan's public characterisation — roughly a dozen.
Other NASA officials	"High teens"	Cited in subsequent reporting.
NASA Aerospace Safety Advisory Panel (22 Oct 2026)	Around 22 flights	Panel member Charlie Precourt, a former astronaut, at the panel's quarterly meeting.
Elon Musk (reply on X, Oct 2026)	6–8	Musk: the panel figure is "way too high"; assumes a more capable upgraded Starship.

The practical difference is stark. Analysts have estimated that even if SpaceX reaches two Starship launches a week by late 2027, filling a depot at the panel's number would take roughly three months. At Musk's number it takes a few weeks. NASA itself has declined to publish a firm figure — its Artemis IV graphic pointedly writes "(multiple)" where the tanker count would go. Our earlier NASA Artemis 2028 moon landing timeline explainer flagged this dispute in passing; this post walks through the full sequence behind it, including the second fill in the final tanking orbit that most summaries skip.

Why it matters for USA readers

Artemis IV is the mission the whole programme will be judged by: the first time Americans walk on the Moon in 56 years, and the first proof that the reusable-super-heavy-plus-orbital-refuelling model — the model every serious deep-space plan now assumes — actually works. If it does, the same depot-and-tanker technique opens the door to Mars missions and a permanent lunar base, which is NASA's stated goal for the 2030s. If it slips, the schedule slips with it: Artemis IV is targeted for 2028, and its lander slot is still officially unassigned. NASA's October contract update confirmed that neither SpaceX nor Blue Origin has been assigned to a specific lunar landing mission — both fly test versions on Artemis III, a crewed Earth-orbit docking rehearsal in mid-2027, and the winner of the Artemis IV slot will be decided by whose hardware proves itself first. Blue Origin's Blue Moon does not need orbital refuelling on its first mission design, which is exactly why it remains a live fallback. For readers following the other side of the same race, our SpaceX Starship booster catch Florida explainer covers the rapid-reuse side of the equation: none of this works without boosters that fly, land and fly again, week after week.

Should you care?

✅ Care if you follow the Moon race at all — the refuelling campaign, not the landing, is now the schedule risk for 2028, and the early-2027 transfer demo is the date that decides whether the plan is real. ⏳ Wait before judging the 22-vs-8 argument: both numbers rest on assumptions about a vehicle still being upgraded and a transfer technique never demonstrated at scale. Watch the demo, then believe a number.

What happens next

Three dates decide this story. First, the early-2027 cryogenic transfer demonstration — the first real data on boil-off and transfer efficiency. Second, the uncrewed Starship lunar landing, targeted for the second half of 2027. Third, Artemis III in mid-2027, when four astronauts aboard Orion practise docking with test versions of both companies' landers in Earth orbit. If SpaceX misses the first two, expect NASA's Blue Origin option to move from fallback to frontrunner — and expect the 2028 date to move with it.

FAQs

How many Starship launches will Artemis IV need?

Nobody knows for certain. NASA's safety panel cited around 22 flights in October 2026; Elon Musk says 6–8. Earlier estimates ranged from up to 16 (a 2021 government audit) to the "high teens". The gap comes down to how much propellant each tanker delivers and how much boils off in orbit — both unproven at this scale.

How does Starship refueling in orbit work?

A modified Starship called a depot launches into low Earth orbit, where tanker Starships dock with it and transfer super-chilled liquid methane and liquid oxygen. The lunar lander then launches with near-empty tanks, docks with the depot, fills up, and — in NASA's Artemis IV plan — gets a second fill in a higher "final tanking orbit" before heading to meet Orion.

What is the final tanking orbit?

It is the higher orbit NASA labels "FTO" in its Artemis IV outline. After its first fill in low Earth orbit, the lander climbs to the FTO, where the refilled depot meets it again for the final fuel transfer. Staging the last fill higher up reduces the total propellant the mission needs.

What happens if SpaceX cannot prove orbital refueling works?

NASA has kept a second path open. If SpaceX cannot validate its refuelling approach or complete an uncrewed lunar landing test by the end of 2027, NASA has left open turning to Blue Origin's Blue Moon lander for Artemis IV instead — and after its October 2026 contract update, neither provider is assigned to a specific landing mission yet.

Takeaway: Artemis IV's Moon landing will be won or lost in Earth orbit, months before any astronaut leaves for the Moon — in a depot, a string of tankers and a second fill nobody had explained until now.

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Sources

• NASA — "NASA, Partners Accelerate Lander Development for 2028 Moon Missions" (October 2026, primary): nasa.gov
• NASA — Human Landing Systems reference (primary): nasa.gov
• Everything Space — "NASA details complex, uncertain Starship refueling plan for Artemis IV moon mission" (3 Nov 2026): everythingspace.online
• Space.com — "Do we know how many Starship launches SpaceX will need to get NASA astronauts to the moon? No. Will its refuelling plan be simple? Also no." (3 Nov 2026, via republication): europesays.com
• NASASpaceFlight — "NASA Artemis Update: SLS Stacking, Sortie Suit, Dual 2028 Paths" (October 2026): nasaspaceflight.com
• Proxima Report — "'Accelerated' Plans for Artemis IV Moon Landing Detailed at Last" (27 Oct 2026): proximareport.com
• Ars Technica (via reporting of the 22 Oct 2026 Aerospace Safety Advisory Panel meeting) — 22-flight estimate and Musk's 6–8 reply, as carried by KeepTrack: keeptrack.space