Phasing out the SLS and Orion programs and embracing Starshipby Gerald Black
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| The simple solution for Artemis 4 and subsequent Artemis missions is to go back to the original SpaceX plan that uses only the Starship. |
But using two different transportation systems for Artemis missions adds complexity and increases the cost so much that the whole program would not be sustainable. This is because the SLS and Orion are not only less capable than the Starship, but they increase the cost of each Artemis mission by roughly a factor of ten. The capabilities and cost of the two different transportation systems are discussed below.
This paper proposes a plan for transitioning from using both transportation systems for Artemis missions to using only the Starship. All SLS and Orion work related to Artemis 4 and beyond would end immediately, including the SLS Block 1B upgrade, the SLS Block 2 upgrade, and the second mobile launch platform. The Artemis 2 and Artemis 3 missions would proceed as planned, but then the SLS and Orion programs would end with the Artemis 3 mission.
The SLS and Orion hardware components for the Artemis 2 and Artemis 3 missions have been completed or are nearing completion. The European Space Agency has already completed and delivered to NASA the European Service Modules for the Orion spacecraft for both the Artemis 2 and Artemis 3 missions. If we do not fly these missions, we would be seen as an unreliable international partner. Flying these two missions will help ensure that we return astronauts to the lunar surface quickly and before China does. It will also be easier to persuade Congress to phase out the SLS and Orion programs than to cancel them outright.
SpaceX already has a perfectly good plan for returning humans to the lunar surface using only Starship. This is the original SpaceX plan that Elon Musk revealed at the International Astronautical Congress in 2017. But instead, we ended up with the NASA plan that uses both space transportation systems. This essay covers both the original SpaceX plan and the NASA plan and explain how we ended up with the NASA plan. The simple solution for Artemis 4 and subsequent Artemis missions is to go back to the original SpaceX plan that uses only the Starship.
Getting to our goal of using only the Starship for missions after Artemis 3 will require adding capabilities to the Starship beyond what is required for the Artemis 3 mission. These additional capabilities will be discussed. Flying the Artemis 2 and Artemis 3 missions as planned will allow ample time for SpaceX to implement the additional capabilities needed for Artemis 4 and subsequent missions.
Comparing the capabilities and cost of the SLS and Orion with the Starship
Starship is more powerful and can launch significantly heavier payloads than the SLS. It is fully reusable, whereas the SLS is fully expendable. Yet another advantage is that Starship has a significantly higher launch frequency than the SLS. Unlike the SLS and Orion, Starship can land on the Moon and Mars.
The Orion spacecraft is a lot less capable than it should be. The spacecraft and its abort system are overweight compared to newer, more efficient designs. Orion’s service module propulsion system is underpowered. Also, Orion lands in the ocean, requiring additional expense for recovery operations.
There is a huge difference in the operational cost of SLS and Orion versus Starship. According to a report by the NASA Inspector General, the SLS cost is at least $4.2 billion per launch for the first four Artemis missions. Adding in $1 billion for the Orion spacecraft brings the cost of SLS and Orion to $5.2 billion per launch.
By contrast, Elon Musk has said a Starship launch will eventually cost $10 million or less, and in the very long term as little as $2 to $3 million per launch. Musk hasn’t stated what price SpaceX will charge for a Starship launch once they start making launches for customers, but a reasonable guess is $40 million. That means a staggering 130 Starship launches can be made for the same cost as one launch of the SLS and Orion!
| It seemed evident that NASA did not want a more capable HLS that could also return directly to the Earth, since that would threaten the SLS and Orion programs, and thus be unable to receive Congressional funding. |
Each Artemis lunar mission may require a dozen or more Starship launches due to the need for orbital refueling. If we assume that it will take 15 Starships at $40 million apiece for each Artemis mission, that brings the Starship cost to $600 million per Artemis mission. The cost ratio of using both transportation systems versus using only the Starship is (5200+600)/600 = 9.7. So, using both transportation systems instead of just the Starship increases the cost by roughly a factor of ten.
SpaceX’s original plan for returning humans to the Moon
Before the Artemis program was started, SpaceX had a plan for using the Starship to transport astronauts from Earth’s surface to the lunar surface and back. This plan was revealed by Elon Musk at the International Astronautical Congress in 2017. This original SpaceX plan did not use the SLS or Orion, only what is now known as Starship.
The original SpaceX plan was advertised as being able to land 100 people or 100 tons of cargo on the Moon. This far exceeds the NASA requirement for the Artemis missions. It is also a lot simpler than the NASA plan. Only one crewed vehicle is needed, and the need to rendezvous and dock in lunar orbit has been eliminated.
SpaceX’s original plan included refueling the crewed Starship in an elliptical Earth orbit, then travelling to the Moon and landing on the lunar surface. The astronauts would return from the Moon in the Starship, reenter Earth’s atmosphere, and land back on Earth. Starship was equipped with fins and a heat shield needed for the return to Earth.
The plan is illustrated in the following figures provided by SpaceX.
 Starship lunar mission architecture. (credit: SpaceX) |
 Starship, with a lunar base in the background. (credit: SpaceX) |
NASA’s plan for returning humans to the Moon
In March of 2019, the first Trump administration announced the goal of returning American astronauts to the Moon by 2024, touching off the Artemis program. NASA responded with the plan to use the SLS and Orion to transport astronauts from Earth to lunar orbit, and from lunar orbit back to Earth. To transport astronauts from lunar orbit to the lunar surface and back to lunar orbit, NASA held a competition for a “Human Landing System” (HLS). Several companies and teams of companies entered the competition.
SpaceX proposed the Starship as their entry in the HLS competition, but with a twist. In a major change from SpaceX’s original plan, SpaceX dropped the fins and the heat shield from their proposal, thus removing Starship’s ability to reenter and land back on the Earth. It appears that this was nothing other than a ploy to help SpaceX win the contract. It seemed evident that NASA did not want a more capable HLS that could also return directly to the Earth, since that would threaten the SLS and Orion programs, and thus be unable to receive Congressional funding.
SpaceX won the HLS competition in April of 2021 and was awarded a fixed price contract for $2.89 billion dollars to develop the HLS version of the Starship. This was a significantly lower price than was offered by the other competitors. The following figure shows the HLS version of the Starship on the lunar surface.
 Human Landing System version of the Starship on the lunar surface. (credit: SpaceX) |
Transitioning to Starship-only Artemis missions
To eliminate the need for the SLS and Orion for Artemis missions, we simply need to transition from the NASA plan back to the original SpaceX plan. The primary change needed is to add the fins and the heat shield back onto the Starship that does the lunar landings, enabling the Starship to return the astronauts back to Earth.
Consideration should be given to adding the fins and the heat shield back on the Starship lunar lander as soon as the Artemis 3 mission. While the Artemis 3 astronauts would return to Earth in the Orion spacecraft, this would provide an opportunity to try returning the Starship uncrewed directly to Earth. It would also provide an extra measure of safety in case of a major failure of the Orion spacecraft, something like what happened on the Apollo 13 mission. Then the Starship could provide a backup means of getting the astronauts back alive.
Two of the most challenging and dangerous parts of an Artemis mission are the launch to Earth orbit and Earth reentry and landing following the return from the Moon. For the Artemis 3 mission, the SLS and Orion will perform these functions. These are important capabilities that must be added to the Starship for missions following the Artemis 3 missions. We’ll discuss each of these in turn.
Launching astronauts to Earth orbit on the Starship
The SLS and Orion have a proven launch abort system with its own motor to power the crew capsule away in case of a failure. Starship does not. Starship will have some launch abort capability, though not nearly as robust as for the SLS and Orion.
The Starship must demonstrate very high reliability to compensate for lack of launch abort robustness. NASA might require something like 100 consecutive successful launches before allowing NASA astronauts to launch on Starship.
Starship may or may not be sufficiently reliable to launch astronauts into Earth orbit by the time of the Artemis 4 flight, which is scheduled for September of 2028. But if not, the Falcon 9 could launch the astronauts into Earth orbit aboard a Crew Dragon spacecraft. Once in Earth orbit, the Crew Dragon would rendezvous and dock with the Starship that was launched separately without crew. The astronauts would then transfer to the Starship and the Crew Dragon would depart. The Starship would then continue with its mission just as if the astronauts had launched aboard Starship.
Returning the Starship from the Moon to Earth
Starship has already demonstrated the capability of returning from orbit to a pinpoint soft landing in the ocean. Returning from the Moon generates more heat than returning from Earth orbit. However, SpaceX has been designing the Starship heat shield with return from the Moon and Mars in mind. Laboratory testing has shown that the thermal protection system tiles that comprise Starship’s heat shield can withstand the higher temperatures generated by return from the Moon.
The Artemis 4 mission is currently scheduled for September of 2028, but realistically won’t occur until at least 2029. That will allow ample time for SpaceX to develop the capability to return from the Moon directly to Earth.
| We need to end expensive programs that have questionable value, such as the SLS and Orion. Instead, we need to substitute programs that will inspire the next generation, like building a lunar base and landing the first humans on Mars. |
An important benefit of returning the Starship directly to Earth from the Moon is that it aids in the maintainability and reuse of the Starship. Starship can easily be refurbished on Earth, then reflown on another lunar mission.
Contrast this with trying to maintain and reuse a Starship that only transits between lunar orbit and the lunar surface. Maintenance would be a nightmare. Detailed up-close visual inspections are necessary. Parts frequently need replacing, and it’s not unusual that an entire engine needs replacing. We just don’t have the facilities in lunar orbit or on the Moon for doing the needed maintenance and refurbishment, and we won’t for quite some time.
Summary and conclusions
Using both the SLS/Orion and the Starship space transportation systems increases the cost of each Artemis mission by roughly a factor of ten. This will not be sustainable. A better plan is to phase out the SLS and Orion programs, ending these programs completely with the Artemis 3 mission. Using only Starship also greatly reduces the complexity of the Artemis missions.
We need to end expensive programs that have questionable value, such as the SLS and Orion. Instead, we need to substitute programs that will inspire the next generation, like building a lunar base and landing the first humans on Mars. Starship will reduce the space transportation costs to the point that we can afford both building a lunar base and landing the first humans on Mars.
Starship is a game-changer. We need to embrace Starship, fully utilizing its capabilities. The space industry will flourish with Starship, and lots of new, high-paying jobs will be created. The advances in space technology will also benefit and enrich the lives of people on Earth.
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