In what will likely be his most consequential act as NASA’s interim leader, Sean Duffy said last month that the space agency was “opening up” its competition to develop a lunar lander that will put humans on the surface of the Moon.
As part of this move, Duffy asked NASA’s current lunar lander contractors, SpaceX and Blue Origin, for more nimble plans. Neither has specified those plans publicly, but a recent update from SpaceX referenced a “simplified” version of the Starship system it’s building to help NASA return humans to the Moon.
“Since the contract was awarded, we have been consistently responsive to NASA as requirements for Artemis III have changed and have shared ideas on how to simplify the mission to align with national priorities,” the company said. “In response to the latest calls, we’ve shared and are formally assessing a simplified mission architecture and concept of operations that we believe will result in a faster return to the Moon while simultaneously improving crew safety.”
So what would a simplified architecture look like? It is difficult to say for sure, but there are some interesting ideas floating around.
First, let’s make a couple of assumptions. Any approach to shortening the Artemis III timeline should not involve major hardware changes. This rules out a “stubby” version of Starship, which would require a significant reworking of the vehicle’s internals. Essentially, any new plan should use hardware that exists largely in the structural shape and form it’s in. And for SpaceX, we’ll assume that “simplified” means not working directly with other contractors beyond those already involved in Artemis III.
With these ground rules, there are two changes that SpaceX, in conjunction with NASA, could make to simplify or potentially accelerate Artemis: “Expendable Starships” and “Enter the Dragon.”
Expendable Starships
One of the biggest challenges with the existing plan is refueling in low-Earth orbit. Essentially, SpaceX must launch a “depot” variant of Starship and then fuel it with “tanker” Starship upper stages. Once this depot is full, the “lunar lander” variant of Starship launches, is refueled, and then flies to the Moon. There, it awaits a crew of astronauts on board Orion to land them on the Moon and return them to lunar orbit.
Estimates vary widely for how many ‘”tanker” Starships will be required to fuel the depot for a lunar mission. In truth, no one will know the answer until there is a mature Starship design with real-world performance numbers and demonstrated efficiency of propellant transfer and storage.
Critics of the SpaceX plan, and there are many, say the mission architecture is clunky and untenable. One household name in the space industry recently told Ars he believes it would take up to 20 to 40 “tanker” launches to fill a depot. That seems high, but a number in the ballpark of 12 to 20 flights (probably with the next-generation V4 ships) is realistic.
That is a lot of launches, to be sure. But it’s not inconceivable that a company now regularly launching three Falcon 9 rockets a week could launch a dozen or more Starships per month in the not-too-distant future.
There is one relatively straightforward way to cut down the number of “tanker” launches. For early Artemis missions, SpaceX could use expendable “tanker” Starships rather than landing and reusing them. It is not clear how much this would boost the capacity of Starship, but it likely would be considerable. SpaceX probably could remove the grid fins (multiple tons), as well as a tiled heat shield that (according to rumors, it must be said) is running considerably more massive than what was budgeted for. There also would be propellant mass savings without the need for reentry and landing burns.
Using an optimized, expendable Starship might reduce the number of tanker missions required by up to 50 percent. The are downsides, including a significant increase in costs and an undermining of the whole point of Starship: full and rapid reuse.
There is a third downside, and this is perhaps the most important one. An “expendable” Starship plan would be anathema to the leadership of SpaceX, including founder Elon Musk. Officials there do not believe the space industry has fully digested how Starship will transform the launch industry.
“You don’t yet understand how many Starship launches will happen,” a senior SpaceX source told Ars.
The company is aiming to launch 1 million tons of payload to orbit per year, the majority of which will be propellant. SpaceX simply believes that once it locks in on Starship operations, launching a dozen or many more rockets per month won’t be a big deal. So why waste time on expendable rockets? That era is over.
Enter the Dragon
A second option would be to rely solely on SpaceX hardware.
I don’t expect NASA to be interested in this idea, but it’s worth discussing. Nearly a year ago, in the immediate aftermath of the presidential election, Republican space officials were considering canceling Artemis and substituting a “competition” similar to the Commercial Cargo program. It was thought that both SpaceX and Blue Origin would bid plans to land humans on the Moon and that NASA would fund both.
These plans have largely fallen by the wayside in the last 12 months, though. NASA (and perhaps most importantly, paymasters in Congress) prefer to stick with the Space Launch System rocket and Orion spacecraft for the initial Artemis missions.
But if pressed, SpaceX could come up with a simplified Moon landing architecture that requires fewer refuelings. There are multiple ways this could be done, so I’ll offer just one variant here:
- SpaceX launches the “lunar” variant of Starship into low-Earth orbit, uncrewed
- SpaceX launches two “depot” variants of Starship into orbit
- Both depots are fueled (perhaps requiring 3-5 “tanker” launches each)
- One of these depots flies out to low-lunar orbit, the other fuels the Lunar starship previously launched into low-Earth orbit
- A crew of four astronauts launches on Crew Dragon, which docks with the Lunar Starship
- Crew transfers to Starship, which undocks from Dragon, flies to the Moon, and lands
- After days on the surface, this Starship launches from the Moon and refuels from the second depot in lunar orbit
- Starship flies back to low-Earth orbit, docks with Dragon, and Dragon returns to Earth
Does that sound complicated? Sure. But it’s arguably not as complicated as an Orion-based mission, and it would likely necessitate fewer refuelings. This is because Starship does not need to rendezvous with Orion in a near-rectilinear halo orbit, and there is no 100-day loiter requirement for a fully fueled Starship at the Moon.
This solution, however, would likely be viewed as toxic by NASA’s safety community due to the need to refuel in lunar orbit with crew on board. A decade ago, when SpaceX proposed fueling the Falcon 9 vehicle on the ground with astronauts on board—a procedure known as load-and-go—engineers tasked with the crew’s safety went berserk.
“When SpaceX came to us and said we want to load the crew first, and then the propellant, mushroom clouds went off in our safety community,” Phil McAlister, NASA’s then-chief of commercial spaceflight, told me when I was writing the book Reentry. “I mean, hair-on-fire stuff. It was just conventional wisdom that you load the propellant first and get it thermally stable. Fueling is a very dynamic operation. The vehicle is popping and hissing. The safety community was adamantly against this.”
It’s probably safe to say that SpaceX would be unhappy with the first solution offered here, and NASA would be unhappy with the second one. For these reasons, SpaceX’s current architecture may well remain the default one for Artemis III.
George Lucas’ narrative art museum opens next year in LA