Analysis on the Sustainability of NASA’s SLS Program

The Space Launch System, or, SLS, created by the national space agency of the United States of America (NASA), is classified as a super-heavy-lift space launch vehicle primarily having a goal of returning the human race to the lunar surface, to establish a sustained presence there, as a part of NASA’s Artemis Program.

On November 16th, 2022, the SLS rocket embarked on its first journey to space, and not just space, but the moon. To start on a 25-day journey, the rocket lifted off from LC-39B from Kennedy Space Center in Florida. After the primary objective of circling the moon was completed, the Orion Space Capsule returned to Earth and splashed down in the ocean on December 11th.

SLS has proven that it is capable of reliably launching its crewed Orion capsule to lunar orbit and back. But the primary concern about this vehicle and rocket program is its long-term sustainability. The primary concerns with this launch vehicle developed by NASA are as follows:

  • Outdated Technologies & Systems
  • Excessive Cost
  • Unreasonably Long and Consistent Delays

Firstly, on the topic of SLS’ outdated technologies & systems, the Space Launch System rocket uses technologies that are so old and outdated that you’d think it’s a joke. Most crewed rockets feature something called a launch escape, or, launch abort system, but we’ll just refer to it as a LAS (launch abort system). The LAS is designed to quickly accelerate a crewed capsule away from the booster rocket launching it, in the event of a major system failure posing a threat to the safety and/or lives of the crew. Nowadays, crewed launch vehicles typically utilize hypergolic liquid propellant to power the LAS. Hypergolic propellants (specifically, Monomethylhydrazine and Dinitrogen Tetroxide, in this case) spontaneously combust upon contact and can be stored at room temperature, and allow for the avionics (flight computer) of the capsule to easily throttle the hypergolic-propellant-powered engines. This makes hypergolic propellants ideal for a launch abort system.

Many modern-day crewed space capsules do use hypergolic propellants. This includes the Crew Dragon capsule of SpaceX (an aerospace company known for insane amounts of innovating and achieving the impossible), as well as Boeing’s Starliner Capsule, which, though isn’t exactly up-to-date or anywhere near on par with SpaceX’s Crew Dragon Capsule, is using a modernized launch abort system.

Then, we have other space capsules using old and traditional solid propellant. Solid propellant is exactly what you’d think it is. It is rocket propellant that is solid, or in other words, not liquid. Once you ignite it, you cannot stop it. Though it can be indirectly throttled using various techniques, it wastes efficiency and is unnecessarily complicated. Unfortunately, SLS is a rocket that uses this kind of solid propellant for its launch abort system. It also uses a pull system rather than a push system for its launch abort system, which adds the necessity for a protective shell around the capsule to prevent the parachutes from quite literally melting and to prevent damage to the capsule’s overall structure, adding unnecessary mass, ultimately reducing overall efficiency and potentially increasing costs even more. To put it simply, there are two types of launch abort systems, a traditional one which uses older and usually more inefficient technologies and techniques, and a modern one which uses more up-to-date technologies and techniques. In almost every way, NASA picks the former.

Additionally, for the SLS rocket, NASA has opted to essentially create exact copies of the Space Shuttle Side Boosters, for SLS’ side boosters. Not only do these side boosters use traditional older solid propellant (atomized aluminum powder as fuel and ammonium perchlorate as oxidizer), but they are near-direct copies of the same boosters that powered the Space Shuttle, which first launched in 1981. That is about 42 years ago at the time of writing this. It has been 4 decades, and many things have progressed, but it seems that NASA’s solid rocket boosters have not done so, or at least, not nearly at the rate as they should have.

Solid Rocket Boosters are also, due to their nature, extremely difficult to rapidly re-use. They require intense refurbishment and deep manual inspection by NASA each time they are recovered from space, using parachutes, which is also an out-of-date method of spacecraft recovery. Rapid re-usability of crewed space vehicles and all of their components is absolutely vital for humanity’s future, but SLS has not taken a step in this direction. In fact, with the development of SLS, they’ve almost taken a step backwards.

One of the main engines (RS-25 Engine Number 2045) on the inaugural launch of the SLS rocket in November of 2022 had gone to space on 12 different Space Shuttle Missions. The first mission was STS-89 (25 years ago), and the last one was STS-135 (12 years ago). As you know, the Space Shuttle is now retired. This RS-25 engine flew on 12 different space shuttle missions across multiple decades and was used again on the inaugural launch of the SLS rocket. That’s a little ridiculous.

Some will argue that these engines have already reached maximum efficiency and cannot be upgraded any further, so NASA might as well re-use some that they have laying around. However, it is near-impossible that efficiency of the RS-25 engine has been maximized to the absolute limit, and it has been shown that the RS-25 is not suitable for modern space launch vehicles. This is because, for every time an RS-25 engine is fired, and then shut down, it has to undergo deep human inspection and (likely) refurbishments, which can take anywhere from days to weeks to even months, whereas with a modern rocket engine like SpaceX’s Raptor Engine, you can fire the (extremely powerful and high thrust) engine multiple times on and off within an hour.

On the topic of SLS’ excessive costs, this has been an issue with NASA and its rocket programs for some time now. NASA has existed for countless decades and possesses unbelievable amounts of data regarding rockets, propulsion, and all things related. This is a good thing. However, it seems that they are not fully putting this immense knowledge and data of rockets and all of their systems to use. The SLS program has cost over $23.8 billion thus far, and it will only continue to increase. This number is insanely high. Even just a 15% reduction in spending would probably be pretty easy, but NASA has not and likely will not do it. In addition to the total cost of the SLS program, each new physical launch cost about $2 billion. This is truly an excessive amount of money that has been spent on the SLS program by NASA. We are all for NASA having a large budget, or, even having its budget increased, but they must control and fix their spending problem, particularly on their space launch vehicles. The main concern that led to the Space Shuttle Program’s end was excessive cost.

The NASA Office of Inspector General (NASA OIG) reported on May 25th, 2023, that their auditors discovered that “long-standing issues related to NASA’s management of SLS contracts for the RS-25 Engines and Boosters—the two components that will power the mega rocket to space—have contributed to $6 billion in increased costs and delays of 6 years.”

Ultimately, though money is valuable (or, at least we’re told so), time is the most valuable thing, not money. Not only has NASA wasted well over $6 billion USD (which if you didn’t know, is really a lot of money!) on the SLS program, but they have wasted over 6 years (2190 days) in time, due to their poor choices leading to delays with the SLS program. You can find the relevant document by NASA below.

It is also likely that NASA simply employs way too many people, which may largely contribute to the overall spending program of NASA as a whole, wasting unimaginably large amounts of money. This is the case with most large corporations. You slash the workforce by 20% and there’s no noticeable difference. NASA could unknowingly have hundreds, if not, thousands of people sitting around doing nothing all day, while they are paid. If this is the case, then it shows NASA has a consistent spending problem in various departments, further solidifying the high likelihood that NASA is also wasting huge amounts of money in the SLS program.

NASA urgently needs to fix its spending problems on SLS.

Multiple long and consistent delays to the SLS program could have been avoided, but instead occurred due to the poor choices of NASA. NASA’s inspector general has also previously stated that the SLS program is “unsustainable” for its intended goals, due to excessive costs. You can also see analysis done by the US Government Accountability Office regarding NASA below:

The National Aeronautics and Space Administration’s (NASA) portfolio of major projects in the development stage of the acquisition process continues to experience cost increases and schedule delays. This marks the fifth year in a row that cumulative cost and schedule performance deteriorated (see figure). The cumulative cost growth is currently $9.6 billion, driven by nine projects; however, $7.1 billion of this cost growth stems from two projects—the James Webb Space Telescope and the Space Launch System. These two projects account for about half of the cumulative schedule delays. The portfolio also continues to grow, with more projects expected to reach development in the next year.

Many space news agencies such as Ars Technica, Planetary Society, SpaceNews, and more, have also reported on NASA’s spending problems and their problems with slow progression, specifically on the SLS program.

The conclusion is that unless NASA makes rapid and significant reforms to the Space Launch System program, it will not be sustainable long-term, and will inevitably be phased out. The 4 currently-scheduled SLS launches will likely continue and will be successful (given some delays), but in the long-term, the SLS program will, according to our research, likely not be a space program that significantly accelerates human progress in space, or leads to breakthroughs on a level never before thought of. It seems that entities in the private sector, primarily being SpaceX, are developing space launch vehicles and solutions much more ideal for modern humanity, as seen with the Starship launch vehicle (created by SpaceX). If the seen trends continue, the private sector will overtake NASA by far in terms of space launch vehicles, in the near future.