SLS vs Starship: Why Do Both Programs Exist?

Video by Tim Dodd, the Everyday Astronaut. Web version by Florian Kordina and Joey Schwartz

A video released by Everyday Astronaut this week looks at SLS and Starship. Both the video and this article explore how they relate to NASA’s plans to get back to the Moon by 2024.


NASA just announced the lunar landers for the Artemis program. To everyone’s surprise, SpaceX’s massive Starship is one of three landers NASA chose alongside Blue Origin and Dynetics.

Understandably, this is bringing up a lot of questions. Some of which we will answer in my next video/article: “Should NASA just cancel SLS and use Starship and/or other commercial launchers for Artemis?” But today I think we need to settle a lot of debates about these two rockets first. Now, more than ever, it is time we truly compare them head-to-head.

Why Two Mega-Rockets?

This might go down in the history books as some serious irony that these two rockets even exist at the same time. Despite these two vehicles having very similar capabilities, you could not come up with two more opposite vehicles. And two drastically unique engineering philosophies.

Boeing and NASA built it over the years with seasoned rocket engineers. In contrast, Starship is being built in a field in Texas by a patchwork team of space cowboys. Some of whom previously built water towers.

How To Compare These Beasts?

Today, let’s look at the history and progress of Starship and SLS. Furthermore, the Orion spacecraft and everything else necessary for the Artemis missions, including their design considerations and their capabilities.

Once we do that, I think we can answer the question. How is it possible that two rockets like SLS and Starship even exist at the same time? Should they exist at the same time? One is easily the most ambitious rocket ever conceived. The other one is living in the past. It is literally reusing old parts from retired Space Shuttles.

How on Earth did we even wind up here? Two of the most powerful rockets ever made, and they are going online at the same time. We have got a lot to cover, so let’s get started.

What is a Super Heavy Lift Launch Vehicle Anyway?

You guys know me. Once I got into SLS vs Starship, I got way too carried away answering my own questions. I was diving in deep and correcting a lot of assumptions I had wrong. I have boiled this thing down all the way and we will cover all the bases in great depth! This one is nuts!

NASA and SpaceX are not in competition!

Right off the bat, we have to make one thing clear. NASA and SpaceX are not competitors. If you love SpaceX, you can thank NASA for that. NASA is SpaceX’s biggest customer and their biggest supporter. Let’s keep that in mind.

It may be more obvious than ever, now that NASA is investing in Starship for the Artemis program. Seeing NASA plastered all over SpaceX’s Falcon 9 rocket for the Commercial Crew Program is proof for that too. The relationship between NASA and SpaceX goes back to near SpaceX’s founding.

Falcon 9 SpaceX NASA DM-2
SpaceX’ Falcon 9 with the retro NASA logo on its side. This particular rocket will support DM-2. (Source: NASA)

If it were not for NASA’s initial investment of nearly $400 million for the Falcon 9 and Dragon spacecraft, SpaceX would not be here. Plus, the multi-billion dollar CRS and Commercial crew contracts helped SpaceX get to where they are today.

NASA does incredible things. They do vital research and science that no private company would or could ever do. There’s lots they do behind-the-scenes, things that often go unnoticed. In my previous video that compared SLS and Starship, I explained why it was unfair to compare NASA the organization directly to SpaceX, the private company.

Let’s All Get Along!

As you folks know, I am mostly for team space. I like to encourage my audience to fight tribalism and not just think one thing is the best and everything else sucks. But with NASA building and operating a rocket, then we can properly compare the pros and cons of those two systems. I already know there is plenty of you out there that are orange rocket bad, shiny rocket good, and vice versa, so let’s come together, sing Kumbaya and celebrate the fact that we have multiple mega-rockets in existence!

Super Heavy-Lift Launch Vehicle Definition

Ok, now that the handholding is out of the way, let’s define the term Super Heavy Lift Launch Vehicle (SHLLV). Just wanted to explain why we are not including rockets like Blue Origin’s upcoming New Glenn or other heavy-lift launchers in this comparison. The aerospace industry considers a SHLLV as a rocket that can carry over 50 metric tonnes into low-Earth orbit (LEO).

Super heavy-lift launch vehicles can put bigger things into orbit, but what that means is having enough capability to send potentially enormous things to the Moon. Or, they can get probes on direct trajectories to our outer solar system without timely gravity assists. That could mean getting to those far out destinations almost three times faster!

Super Heavy Lift Launch Vehicle Capabilities Saturn V vs N1 vs Energia vs Falcon Heavy vs Space Shuttle

All The SHLLV Rockets, Past And Present

Historically, there have only been five super heavy lift launchers to fly, ever.  Only four launch systems were successful. They include the 1960s-era American built Saturn V which could lift 140 tonnes to LEO. Also from the 1960s and early 1970s was the Soviet Union’s unsuccessful N-1 rocket designed to lift 95 tonnes to LEO. In the 1980s there was also the Soviet Union’s twice flown Energia rocket which could fly 100 tonnes to LEO.

Today’s only flying SHLLV rocket is SpaceX’s Falcon Heavy.  Officially, it can loft about 64 tonnes to LEO in fully expendable mode. If it is in reusable mode, it can still launch over 50 tonnes to LEO. So far, Falcon Heavy has not needed to fly in expendable mode and that may never happen.

The Space Transportation System: The Shuttle Program

And lastly, we have the Space Shuttle–or as NASA officially named it–the Space Transportation System (STS). If we add the orbiter as part of the payload capability, STS could technically put 122.5 tonnes into orbit. Now we should point out real quick that by that same logic, if you included say the core stage of the SLS, which could get into orbit if they wanted it to, would add another 80 tonnes to its payload capacity.

But STS was just a different beast, and you had to factor in the orbiter as payload that went orbital, but the actual deployable payload capacity was only 27 tonnes. Although there was a proposed Shuttle-C to make STS a super heavy lift launcher, we will ignore it and just keep going.

If humans are to return to the Moon as soon as possible, or especially if we are to get to Mars, we absolutely need to have some serious capabilities. I think we are long overdue for these kinds of missions. I want humans on the Moon again. In 4K! Or 8K for that matter! Send MKBHD!

The Artemis and Gateway Programs

Before we get started with SLS and Starship facts, we are working on getting back to the Moon with NASA’s Artemis program. NASA’s plans already have a substantial amount of work, funds and goals invested into making Artemis a real program.

In this article, you will hear Artemis thrown around a lot. Although, we could lump the upcoming lunar Gateway Space Station into Artemis. Instead, we are just going to focus on the SLS, Orion and the Human Lander Systems. Which to be clear, Artemis is to SLS like Apollo was to the Saturn V. It is the name of the program, not necessarily the rocket or spacecraft.

SLS to Artemis Saturn V Apollo

For now, the Gateway is being skipped for the first mission or two that will to carry astronauts on a lunar landing. Although planning for Gateway is in progress, we are just going to focus on the lunar landing and the hardware directly involved in that.

The History Of SLS And Orion

We will get some facts straight before we pit these two rockets head-to-head! First, I think many people have the wrong idea with the how and why NASA pursued SLS and Orion. Or how those programs fit into Artemis’ plans. Then second, we will move along to Starship’s history, which is rapidly progressing.

Post-Columbia Tragedy, Constellation Program Born

After the Space Shuttle Columbia tragedy, NASA reexamined its next steps. It began looking for low-Earth orbit replacements to the Space Transportation System. They began setting their sights on deep space exploration and needed to build a big rocket to do so.

NASA’s original vision for deep space and LEO was the Constellation program. It would be a crew transporting replacement for the Shuttle with the Ares I rocket used for LEO missions. NASA planned an even bigger rocket called Ares V for its Lunar and Mars exploration missions. After slow progress and massive cost overruns, all pointed out in the 2009 Augustine Commission report, the Constellation program wound up being cancelled.

NASA Ares 1x
An Ares-1X rocket lifting off on October 28, 2009. (Source: NASA)

SLS: the Space Launch System, AKA “The Senate Launch System”

The NASA Authorization Act of 2010 directed NASA to develop a “Space Launch System.” It had to lift 70 to 100 metric tonnes to LEO and maturing later to lift 130 tonnes or more. The vehicle must be able to lift the Orion Crew Vehicle since its development was so far along and Congress required NASA to work with existing partners when available.

Originally, NASA hoped to roll out a massive rocket quickly and efficiently as their directive from Congress required. They were to have it operational by December 31st, 2016! NASA performed figures of merit analysis” and narrowed it down to five different variations of a launch vehicle. Some of them looked exciting with ten-meter-wide core diameters and oxygen-rich staged combustion engines. The analysis weighed their options with affordability being 55 percent, schedule 25 percent, performance 10 percent and programmatic 10 percent.

Ares V vs SLS

Side by side comparison of what would have been an Ares V rocket and the SLS. (Source: NASA)

SLS With STS Heritage

NASA settled on what we now know as the SLS. Although SLS and Ares V look very similar, SLS was actually a fairly blank slate design. It definitely took cues from a rocket proposal called “Direct.” SLS would lean heavily on the literal leftover parts and facilities from the Space Shuttle. Their thought process was it should facilitate a quick way to prototype and test the most powerful rocket ever built.

NASA kept the rocket’s heritage close to the Space Transportation System’s. Thus making some of those contractors, its employees and members of Congress happy. This design decision ensured that funds would continue to flow to Shuttle contractors, or so the thought was.

Cost-Plus Contracting

Unlike commercial crew, NASA would continue to work with the contractors from the Shuttle-era using cost-plus contracting funding scheme. That means, “here is how much money we will give you to get it done, but we will also pick up the bill on anything that goes over budget.”

Funding for SLS development hovers around $1.5 billion per year since 2011. The Orion spacecraft receives a little over $1 billion a year, also since 2011. NASA assured contractors that they would have plenty of resources to make these projects happen. The contractors stayed within a realistic NASA budget, which matched the funding levels during the Shuttle era.

However, the problem with cost-plus contracting is it offers very little incentive to remain on budget or especially on schedule. In fact, timeline slips literally means more money for the contractors. The prime contractor for SLS, Boeing, receives the most money for the project. NASA conducts performance reviews of their contractors. Yet, government officials still blasted NASA for being too easy on some of these contractors: more on that later.

NASA management review

SLS Similarities To Shuttle Only Cosmetic

Although SLS does literally seem like a giant wingless Space Shuttle, NASA made many changes to the vehicle. For instance, they improved its performance and lowered its costs. Here is a quick rundown of the changes.

The SLS will have five-segment SRBs as opposed to the four-segment SRBs that STS had. Unlike the Space Shuttle, these boosters lack any recovery hardware. They also feature a redesigned plug that keeps squirrels and stuff out of it. The redesign ensures debris will not potentially damage the nearby RS-25 Nozzles.

A Solid Rocket Booster (SRB) for SLS during a test. The fragments flying around are the newly developed plug. (Source: NASA)

The core stage looks like a Space Shuttle external fuel tank. Other than that, there is virtually nothing in common with the external tank other than its color and its 8.4 meter diameter. It uses a new aluminum–AL 2219. Its construction is distinct from the External Tank. It even uses different welding techniques, and even a new spray foam. SLS will have structural loads going down through the top of the tank as opposed to dangling off the side.

Aerospace-Rocketdyne tweaked the RS-25 engines since they used them on STS. They increased their power output from 104.5 percent to 109 percent or 111 percent in an emergency. But again, just like the SRBs, the RS-25D and later the RS-25E variants are expendable on SLS.

Just a fun side note, I base those percentage numbers on the original rated thrust of 1.6 MN (375,000 pounds of force) at Sea Level. After some tweaks to these main engines, they wound up being able to throttle up beyond their original design parameters during the Shuttle program. For SLS, they are being pushed even further.

Interim Cryogenic Upper Stage

Another cost saving and timeline helping decision was to fly the SLS initially with the upper stage from ULA’s Delta IV and Delta IV Heavy. Known as the Delta Cryogenic Second Stage or DCSS, NASA changed it to fit on top of the 8.4-meter-wide core stage. This Interim Cryogenic Propulsion Stage (ICPS) has different hydrogen tanks and more reaction control fuel than the Delta IV version.

NASA Interim Cryogenic Propulsion Stage Everyday Astronaut SLS
ULA’s Interim Cryogenic Propulsion Stage for SLS.

NASA intends for SLS to have a much more powerful upper stage known as Exploration Upper Stage. The upgraded stage, which is part of the Block 1B upgrade, will make SLS much more capable. Although it will not see the light of day until 2025 at the earliest.

Side by Side comparison of the Interim Cryogenic Propulsion Stage (ICPS) and the Exploration Upper Stage (EUS). (Source: NASA)

Orion Spacecraft, Apollo on Steroids?

Next, we need to talk about the Orion spacecraft that sits on top of this entire vehicle for the Artemis missions. Orion is a fairly traditional conical crew spacecraft. In some ways, it is a newer and larger version of the Apollo command module.

Orion VS Apollo capacity volume width
Side by side comparison of Artemis’ Orion and Apollo’s command module & service module

Although Orion looks similar, it is bigger than it might appear. It is substantially a roomer vehicle, at five meters wide versus the Apollo command module’s 3.9 meter width. Orion also sports a whopping 9 cubic meters of pressurized volume compared to 6.2 cubic meters for Apollo. This allows Orion to carry up to six astronauts compared to a normal Apollo astronaut complement of three. For Skylab, they altered the Apollo command module so it could carry five astronauts in an emergency.

The original name for the Orion spacecraft was the Crew Exploration Vehicle. That’s when it was in development for the Constellation program. But it has transformed since then. It now features another cost savings measure: a service module based on ESA’s Automated Transfer Vehicle.

Lunar Lander, Bueller? Anyone?

There is still one thing we need to mention. Something new to the system that is still a work in progress. If the Artemis program is to land on the Moon, it will need a lander.

That brings us to today. So far everything we have talked about and discussed can only get humans into lunar orbit with SLS and Orion. There is not yet the capability to carry a lander with SLS Block 1 as part of the total package. Not even with the upgraded Block 1B.

NASA has officially selected three very different lunar landers for the Artemis program. Each one of them has until 2021 to show exactly how they will get to the Moon. Some proposals could eventually send modules along with Orion in the upgraded Block 1B SLS.

For Artemis III to get to the Moon in 2024, it will need to use the Block 1 SLS. The lander will need to fly on a separate commercial rocket or two. Maybe even three? This will depend on how big it ends up being. Artemis hardware is enormous by contemporary human spaceflight standards.

A Call For Commercial Landers

This portion of the Artemis program is closer to the Commercial Crew Program than it is the rest of the SLS and Orion programs.

NASA created a set of requirements so contractors can bid for the lander contract. In doing so, they hope it is a quick process to meet their ambitious timeline to get astronauts on the Moon by 2024. NASA will not own and operate the spacecraft like they do for SLS and Orion.

Artemis will require at least two rockets per crewed mission to the lunar surface. We will dive deeper into the options the Human Lander Systems proposals could use in the second part of this article. It will look at what other options NASA has if they would decide on cancelling SLS in favor of Starship and other commercial options. For that reason, let’s talk about Starship.

Starship History

If you are new to the scene of Starship, you might not realize how far back this thing goes. Basically, since SpaceX started, there has been talks of doing a “BFR” or “Big F*+#ing Rocket.” Unlike SLS, the actual engineering and development had mostly been behind closed doors since the early days.

Tom Mueller, The Rocket Engine Guy

Going back before SpaceX’s start, propulsion engineer and employee number one, Tom Mueller, had built a “BFR” rocket engine in his high-powered rocket club, Reaction Research Society. And yes, this naming scheme stems from Doom’s BFG.

Tom Mueller SpaceX Tom Mueller McGregor

Fun side note, Tom’s BFR engine was a pintle injector engine that was targeting 45 kilonewtons of thrust. He was facing off against David Crisalli who built a more traditional flat face injector. Tom’s design won out and eventually became the basis for today’s Merlin engine!

But the BFR vehicle did not really start gaining any public notice until around 2012, when Elon would mention a huge rocket dubbed Mars Colonial Transporter that SpaceX would add to their lineup.

SpaceX was still a relatively small company, only having launched three Falcon 9’s by the end of 2012. After that, rumors were swirling about a Falcon X, Falcon X Heavy and Falcon XX rocket that would be their next mega rockets.

IAC 2016, Elon And The ITS

It would not be until 2016–at the International Aeronautical Congress (IAC) in Guadalajara, Mexico–that Elon spilled the beans. The world would finally get a sense for what SpaceX was working on. And yes, that was the super weird press conference where everyone asked ridiculous questions. Well, not everyone…

The plans Elon showed were properly ludicrous, maybe even plaid. Something the world had never seen legitimately proposed. A fully reusable, 12-meter-wide, 122-meter-tall rocket with 42 full-flow staged-combustion methane-powered engines on its first stage. Six vacuum engines and three more sea-level engines on the upper stage. It used an advanced carbon composite construction and had a 300-tonne payload capacity. We knew it as the Interplanetary Transportation System or ITS.

After 2016 we saw some tweaks year to year. With the biggest change being downsizing.  Suddenly the rocket shrunk to a nine-meter diameter, and the capability shrunk with it.

everyday astronaut merch store

Around 2018, SpaceX started calling it BFR again and announced plans to send Japanese Billionaire, Yusaku Maezawa, on a trip around the moon. Meanwhile, maybe the other big change was the decision to shift away from carbon composite construction and instead use stainless steel.

We Dub Yee Three, Starship!

Then the name Starship finally came into existence. To not be confusing, SpaceX calls the entire system Starship. But that is also the name used for the upper stage too! They call the booster stage Super Heavy. Therefore, we can loosely say “Starship,” meaning Starship and Super Heavy. However, we could also mean just the upper stage.

It is like how you can point to corn and say, hey look, that is corn! If it is off the cob and in a bowl, you will still call it corn. But when it is on the cob, you might say it is corn on the cob. God, you can tell I am from Iowa, can you not?

In 2019, SpaceX held a press event in front of a full-size Starship prototype in Boca Chica. Later, we learned its name was Mk 1, short for “Mark One.” By this point, the design was iterating less and now the upper stage was to have only two fins that act like giant air brakes. I already did a video explaining the reasons they likely went with two fins instead of three and it is fun to watch!

That pretty much gets us up to speed on Starship since most of the actual development had been behind closed doors and on SpaceX’s terms. I think now would be an excellent time to go through the progress of these two programs. Let’s add up exactly what they have built and see if we can get a better sense of their wildly unique design philosophies.

SLS Progress VS Starship Progress

This is a segment I wanted to do for a while. Skeptics of Starship will point to all the blown up test articles and say, “They cannot even build a tank.” While skeptics of SLS say, “It has been a decade and nothing has happened.”

Let’s lay out all the hardware they have built. This will be comprehensive, but not a full list of absolutely everything. At least we will spell out the major milestones. Starting with SLS and Orion, there is quite a lot more hardware that the contractors completed and/or tested than you might think.

Artemis SLS Orion Inventory SLS core stage tank Orion test flights inventory
SLS and Orion inventory consisting of test articles and flight hardware.

Artemis 1, Orion And SLS Tests

So far we have seen over a dozen Orions used between Ares 1-X, different abort tests, mockups and drop test units. There was a mostly feature-complete flight of a legit Orion in 2014 on top of a Delta IV Heavy for EFT-1. There even was a test of a full-size SLS hydrogen tank at Marshall Space Center in 2019. The test lasted over five hours at 260 percent of the core’s structural rating.

All the hardware for the first all-up test of SLS and Orion on the Artemis 1 mission is mostly ready for final assembly. The core stage is on the test stand preparing to do a full duration static fire. Stacking the five segments of each SRB will happen soon. The Launch abort system is ready. The actual Orion spacecraft has finished all of its testing. It is back at Kennedy Space Center awaiting its upcoming launch around the Moon!

The Interim Cryogenic Propulsion Stage has been ready to go for years. The Orion service module, supplied by EAS, is ready. Literally, Artemis 1’s equipment is complete! All that remains is to complete testing and then integrations.

There are 16 RS-25D engines. 14 out of the 16 engines previously flew on Shuttle missions. They already integrated four engines with the Artemis 1 core stage. There are enough solid rocket booster segments to make up 16 boosters or eight flights. Even 4 RL-10s are ready for use on upcoming upper stages.

Artemis 2 And 3 Hardware

Now that manufacturing lines and practices are in place, parts for Artemis 2 are coming together. This includes the LOX tank, hydrogen tank, intertank, forward skirt, engine section on the core stage. The pressure vessel for Orion, its service module, the heat shield, the launch abort tower and other bits of hardware are in place. And as mentioned, the RS-25s and booster segments are complete too.

That is not all, Artemis 3 hardware is also coming together already too! This includes parts of Orion, parts of the service module, the SLS hydrogen tank, the engines and solid rocket motors.

So, you can see that SLS and Orion did accomplish a lot throughout the past decade. Even when you factor in Orion’s longer timeline. So how is that compared to Starship’s progress?

Starship’s Progress

Starship’s progress differs significantly from SLS and Orion. Much of Starship’s early work was very secretive. They shrouded even the Raptor engine program in mystery until Elon showed videos of it IAC 2016.

The Raptor engine started its development around 2012. Since then, it has gone through a lot of testing. To date, there are 26 Raptor engines built, many of which are in pieces now. Most likely only a handful that are truly flight-capable at this point. But that number is transforming as SpaceX cranked out most of them in just 2019 alone.

SpaceX Starship inventory MK1 MK2 SN1 SN2 SN3 SN4 SN5 Starhopper raptors
SpaceX inventory consisting of test articles, prototypes and Starhopper.

Steel Is Real

If we ignore anything from the carbon composite and/or the 12-meter diameter Starship, they built almost everything we are about to list within the past year. Starting with Starhopper, it is the only Starship prototype to propulsively fly. Its 20-meter and then 150-meter hops are the only flights so far. Then we saw the Mk 1 full-scale prototype come together and subsequently blow its lid off.

SpaceX was building concurrently a similar prototype in Cocoa, Florida. It was a way for two teams to work on different methods of construction simultaneously, in a friendly competition. SpaceX abandoned the Mk 2 prototype in-place, and it is still just hanging out there in Florida.

2020: One Is Better Than Two

Then we saw the two teams come together at the end of 2019 and furiously start building the next prototype, Mk1. It failed spectacularly while in testing, as we expected. Elon Tweeted before the test that it would not perform hops. SpaceX was already working on the next prototype.

That was not the only change. Around this time SpaceX switched from using Mk to SN nomenclature too. There were three sub-scale pressure test articles that tested the welds and the tanks’ ability to hold pressure at cryogenic temperatures. Then there was another full scale tank test with SN-1 which exploded, imploded and then exploded again when its bottom fell off. Lastly, we have SN-3, which also failed because of improper testing procedures. Despite those failures, their next prototype, SN-4, is already complete and passed the cryogenic pressure tests.

SpaceX has built and blown up three times more tanks in the last six months than SLS has built in the last six years! This is where we see the massive differences in the building, testing, and overall philosophies! Time to dig into this for a second.

Starship Philosophy VS SLS Philosophy

By now you have probably already have a sense of the design differences and philosophies. Just by seeing how these two programs have developed, the differences are apparent. But there are a few things that really reinforce just how different they truly are.

SLS, Let’s Plan It Into The Ground

Let’s start by putting ourselves in NASA’s shoes. NASA, being government funded, has to do things differently than a private company with private funding. Perhaps the biggest thing they cannot really do is take big risks.

When building something as massive, complex and ambitious as SLS, you really need to account for everything before you send out the instructions to the contractors. If you tell contractors to build something and then something changes in the plan, all of that work is for naught. This compounds when you have dozens of contractors and government supporting employees, all relying on each other to have their parts done on time.

Imagine if a key part gets delayed a year, what are the government employees supporting that system supposed to do? You cannot lay them off for a year and then bring them back onto the project. They would go find new work. You cannot really reassign them to something else. It is not likely a propulsion engineer is just going to move over to the other rocket NASA is working on. There are a lot of inherent costs per year that are sunk-costs in running a program of this scale.

NASA, Spread The Money Around

Although it is inherently less risky and inefficient, spreading money and jobs around works politically. There is also a funding safety-net by having multiple contractors and space centers spread throughout the country. This decentralized approach massively helps make it more appealing to congressional budgets. Even if it is inefficient, it helps ensure that program funding continues.

This is especially true when you realize that the Europa Clipper, an upcoming probe to Jupiter’s moon Europa, must legally fly on SLS. Perhaps most nutty about that fact is that they have added $250 million to the program! There will not be an SLS rocket ready until at least 2025. Despite the probe being ready by 2023. Although this law will help in the long run, by keeping the program alive. It additionally will keep it funded during potentially uncertain times with changing administrations.

It is obviously far from being ideal. If you are worried about program survivability and not just having your entire vision shift 180 degrees every four to eight years, doing things like this is just part of the game.

Do not forget, NASA’s budget is only about half a percent of our national budget and the human spaceflight programs are not even half of that.

Failure is Not an Option, for SLS

Therefore, the primary philosophy for building SLS is to plan and take minor risks. There really is not much room to fail when you have to answer to the taxpayers why their money literally went up in smoke. Do not forget, NASA’s budget is only about half-a-percent of our national budget. Actual human spaceflight programs are only a fraction of that.

Starship, The Answer Is 42!

Now compare this to Starship. Starship development is literally as blank slate as it gets. SpaceX did not start with detailed blueprints. Literally, it started by just learning what questions to ask. Then, how to frame the constraints of what their vehicle should do.

Two prime objectives came out of this process. First, be fully reusable. Second, have a capability large enough to be useful in getting humans onto other planets. That is really about it. Then work backwards to find the answers for those objectives.

The next most important item helps to answer the question about developing an engine that is efficient and massively reusable. Like I talked about in my video about SpaceX’s Raptor engine, a methane-powered full-flow staged-combustion cycle engine fits the needs of these goals perfectly.

Raptor’s sootless fuel keeps the engine clean and easily reusable. Its high efficiency makes better work of the fuel onboard.  The engine’s high thrust and small footprint make for a rapidly scalable and multi-engine-out capable rocket.

From there on, the entire thing is basically a playground. Hence when we saw the sudden pivot from carbon fiber to stainless steel. You get a sense of just how important it is for SpaceX to just start flying so they have a starting point to iterate on when you hear Elon explain why it was so important to make the switch.

Starship’s Iteration Speed

Therefore, the iteration speed is why we are seeing so many random things happening at Boca Chica with the development. For that reason it is silly to even bother asking about future plans anymore. I am as guilty of as anyone, because everything depends on what will happen with their current step. Then they will base the step after that on the results of the previous step, etc.

It is a similar philosophy to something known as the waterfall model or perhaps the agile model standard in software development. That is Elon’s original background. Basically, you do not work on step two until you complete step one. Planning any further ahead and you will probably undo work.

This is literally the opposite of SLS, where everything needs to have an exact plan. If you end up building the rocket three meters shorter than the blueprints, suddenly your entire ground support system will need to change too! This exact thing happened with SLS and its mobile launch tower.

Flexibility and Speed

Everything for Starship is still on the table at this moment. I mean, we are literally seeing them build a factory around a rocket instead of vice versa. And frankly, this is massively risky, but it is also much easier to do. Since the company is so vertically integrated, it can move faster and flexibly. This means changes in decisions do not have nearly as big of a ripple effect as a more traditional method.

We will see more hardware fail. There will be setbacks. We will probably see explosions! But unlike SLS, not only is it ok to fail, it is halfway expected. This approach promotes learning through prototyping at lower cost and greater speed. Elon has said over and over approximately, “Failure is an option here, if things are not failing, you are not innovating enough.”

This is very similar to the Soviet Union’s design philosophy back in the heydays of Sergei Korolev. Building something as cheap as possible, test it, if it blows up, see what went wrong, make improvements, repeat! And it definitely gave them a leg up during early development. Say you blow up a rocket you built in two months. Learn from it. They will build another rocket in less time than it will take NASA to fuel up and test fire the SLS once. That is just a monumental difference in philosophies.

Starship VS SLS

I think it is time we really stack these rockets up side by side. This will help figure out just how they really compare when we look at their nuts and bolts. After an initial breakdown, we will go deep into some rabbit holes on these numbers and capabilities. Get ready!

Super Heavy Lift Launcher Capabilities Falcon Heavy vs Saturn V vs SLS vs Starship
Side by side comparison of super heavy lift launchers with the parameters: thrust [MN], LEO capability [t], TLI capability [t], price [$] and price per kg to TLI.
We have already touched on each vehicle’s dimensions, so here they are again. For now, we will just compare the initial builds of each rocket. The Block 1 and Block 1b of SLS, plus the rough version of Starship as it currently stands.

Definitely keep in mind that Starship will change a lot. Pretty much every time one gets built it will differ from the last one. Expect this pace of change well into the 20s or even past SN30. SLS could also change a bit too if Block 1B goes online.

Let’s Compare Engines

While we are at it, let’s show the Saturn V and the Falcon Heavy! It is just so we have some extra perspective on how these vehicles really compare. As they stand today, SLS is big, but Starship will be enormous. It will be bigger than the Saturn V in overall height and just slightly narrower than the Saturn V’s first two stages, but it does not taper almost at all like the Saturn V.

Now, let’s talk about engines and their fuels. Falcon Heavy has 27 sea-level Merlin engines and a single vacuum-optimized Merlin on the upper stage. They all run on RP-1 and liquid oxygen. Then there is the Saturn V, which had five F1 engines on the first stage that ran on RP-1. The five J2 engines on the second stage and one J-2 on the third stage ran on hydrogen.

As we know, SLS has mostly the same formula as the Space Shuttle. Its two SRBs, and four RS-25s running on hydrogen. On Block 1, it has only a single RL-10B2 on its upper stage, also running on hydrogen. In contrast to that, its next version, Block 1b, will have four RL-10s also running on hydrogen.

Lastly, Starship has 37 Raptor engines on the Super Heavy Booster and most likely six Raptors on Starship. This number is very subject to change and is relatively easy for SpaceX to do so, because of the small size of the Raptor engine.

Lift-Off Thrust

Next up, let’s look at their thrust at lift-off. As always, this is fun. The Falcon Heavy is the baby here at 22.8 MN. Now we are getting into the powerful rockets with the mighty Saturn V at 35.1 MN.  SLS is slightly more powerful at lift-off at 39.1 MN, but it is Starship that will be the king here at 72 MN in its present configuration.

TLI Payload Capability, The Real Test

We already went over some of these rocket’s LEO payload capability, so let’s add SLS and Starship back into this. But this time let’s show how much mass they can shoot off to the Moon. We call this translunar injection (TLI), since we are talking about lunar missions here, anyway. Notice, we will show performance for SLS Block 1 and Block 1b. Yet, their LEO capabilities are virtually the same since it is the core stage that mostly drops them off into orbit.

Quick note, this is not necessarily how much a vehicle can put in lunar orbit. It is just how much it could shoot off to the Moon. You still need to get into lunar orbit with your spacecraft. With Orion or Apollo, the service module takes care of that. This is technically a C3 of -0.99 to be exact. That is a measurement of the characteristic energy to get to a certain point in space.

Falcon Heavy, when in reusable mode, can send about nine tonnes to the Moon. That means all three cores land downrange on drone ships as opposed to the two boosters landing back LZ-1. Compare that performance with 15 tonnes to TLI in expendable mode.

Saturn V vs SLS

Next up, we have the Saturn V that could send 48.6 tonnes to the Moon. Then SLS Block 1, which can take 27 tonnes to TLI. The upgrade 1B version should put 43 tonnes into TLI. You might ask how can a more powerful rocket only get half the payload to the moon as the Saturn V? Well, that interim cryogenic propulsion stage is undersized for this size of a rocket. Oddly, even with Block 1B and its four RL-10 engines powering the Exploration upper stage, SLS can only send 43 tonnes into a TLI. Still shy of what the Saturn V was capable of. Which frankly is still baffling to me.

And Starship is a little more confusing for TLI. Starship on its own cannot do TLI. Its massive 120 tonne dry mass prevents it from leaving LEO. Lugging all of that dead weight to the Moon does not work out without it being refueled. Now refueling is 100% part of the plan for Starship. But we will talk more about that in an upcoming video. That video will discuss if Starship should use kick stages or refueling.

Reuse Or Expandable At What Price?

I will now show which of these vehicles is expendable, partially reusable and fully reusable. Here is where we are about to go into a deep rabbit hole, so hold on to your butts. We will talk about price, and this is not an easy thing to talk about. You will see why in a moment.  I adjusted all the numbers you will see into 2020 U.S. dollars.

Let’s start off with what I will call the sticker price. This is the price you could presumably buy a launch. For now, we are kind of ignoring development costs and just what the invoice would be for a launch of said rocket. But we will get into the development costs in an upcoming article. For now, just file these away. We are also only going to look at just the rockets, not the spacecraft like Apollo or Orion, for now.

everyday astronaut merch store

Sticker Price

Let’s start with Falcon Heavy at around $90 million. The Saturn V was around $1.2 billion per launch. SLS Block 1 and its later Block 1b version will be $875 million once production stabilizes. That leaves Starship.  Well, Elon claims they can launch for $2 million. Let’s assume they can do $2 million, but for a while they would be smart to charge $100 million until the market catches up. So let’s just throw $100 million in there as more of a worst-case scenario sticker price.

Now, with these numbers we can do a very baseline dollar to kilogram ratio. Since we are talking about the Moon, let’s only look at how much it costs to send 1 kg to TLI for each of these vehicles.

A Kilogram To The Moon Ratio

Falcon Heavy can get a kilogram to the Moon for around $10,000 whether in reusable or expendable mode. The Saturn V is about $25,600 per kg. SLS’ best-case scenario for Block 1 once they stabilize production is around $31,500 per kg. For Block 1B, it looks significantly better at about $20,000 per kg. Starship at a single $100 million launch cannot do a TLI burn. Therefore, it will take two extra Starship refueling launches to perform such a burn. That would make the total cost $300 million. Refueled, it can send a 156-tonne payload to TLI. So, Starship’s cost per kilogram would end up costing about $2,000.

Those are some very preliminary costs and they make a lot of assumptions. In case you could not tell, we are intentionally sandbagging Starship. This is just in case the per launch price is way too optimistic. It is still by far the most economical thing on the chart.

These preliminary costs are making a lot of assumptions. For example, they do not factor in development costs. We still have a lot to cover on budgets and cost. For now, just file this topic away. We will chase all the rabbit holes in an upcoming article dealing with costs.


How did we get here? How is it we have two different super-duper mega-rockets going online at the same time?

I think the history speaks for itself. When NASA started working on SLS, the thought of a rocket like Starship would have been utterly ludicrous. Even today, many people think it is insane and likely to fail. Starship is “impossible” – until it suddenly is not. And then, suddenly, literally *everything* changes.

Would You Believe, Chief?

NASA has been working on SLS and Orion for nearly a decade. If SpaceX had approached NASA with Starship in 2011, it would be analogous to trying to sell a farmer in 1870 a GPS-guided, 9.0 L turbo diesel-powered four-track 8RX 410 John Deere tractor.  However, all they were looking for was to purchase a plow for their horse. They just would have not believed you if you mentioned the tractor. Oh man, I showed my Iowa again, sorry.

NASA has had the rug pulled out from underneath them so many times. There were so many programs they started that dead-ended. Midway through these programs, they would suffer changes in mission priorities, personnel and leadership. They repeated this multiple times before a program even really got going.

They did what they had to for SLS. NASA took a prudent route by leaning on existing technologies, partners, and program funding schemes. All of that to create a deep space capable rocket that politicians wouldn’t cancel. All of this to regain a capability they lost nearly 50 years ago.

Because I think that is the biggest shocker. It is not Starship. Humanity had Starship coming. Starship is the logical offshoot if one wants to reduce spaceflight costs. Frankly, it makes sense to produce a fully reusable rocket. Everyone wants to do that! No one thinks this is a terrible idea. Few engineers or managers think it is never, ever going to happen.

50 Ways to Leave Your Lover

I think the biggest surprise is that it took 50 years to build another rocket with the Saturn V’s capabilities. Since 1972’s Apollo 17 mission, no humans have left LEO. If you told that to Gene Cernan, the last astronaut to walk on the Moon, he wouldn’t have believed it. On hearing this news, he might have pulled a “Buzz Aldrin” and punched you right in the face.

Since that time, rocket technology has grown. Now, it is achievable not by nations, but by a handful of brilliant and plucky corporations. These businesses could rethink everything related to rockets and space travel. They could open up commercial options and opportunities that just did not exist before.

Mars or Bust!

I know Elon’s life goal is to get to Mars. But in the meantime, he will have completely changed humanity’s access to space for the better. To get to Mars, you need a fully reusable, massively capable rocket. This insane proposition will lead to a shift in spaceflight economics by multiple orders of magnitude.

The reason we stopped going to the Moon in the first place was because it was too expensive. The United States measured their Cold War “genitalia” against the Soviet Union with Project Apollo. That was not a sustainable way to explore the Moon.

Speaking of sustainable ways to explore the Moon, that is exactly what we explore in the next article.  By happenstance, we already researched and wrote it. Stand by, and we will answer, “Should NASA just cancel SLS and use Starship and other commercial launchers?”  We will see if Artemis is a step in the right direction or not.

In my opinion, “orange rocket good enough for now. Shiny rocket will be incredible soon enough.” We as “team space” can celebrate the fact that we even live in a time where we will get to have two super mega-rockets go online at roughly the same time! YES!!!!


Garry Lyles talking about SLS in 2011

SLS C0-Manifest options by NASA

SLS Payload User’s Guide by NASA

FH TLI expendable performance calculation, 3 x drone-ship landing calculation 

OIG report on SLS / Orion

SLS Facts sheet with ICPS and EUS sources 

  1. Your conclusion is a bit off. NASA was approached by both SpaceX and ULA with heavy lift proposals before NASA even started SLS. Whilst neither was anything as advanced Starship, either would have been superior to SLS in capability and cost FAR less. A study commissioned by NASA at the time actually concluded that SLS would be subjected to continual delays and might not ever fly. The reason why SLS was chosen was pressure from politicians whose regions had a big stake in shuttle tech. If you want to now more details, read this article I wrote about it in 2014.

    1. I guess I’m going to disagree with your first sentence….and then mostly agree with the rest of supporting facts. Choosing either of the proposals was never really an option for NASA. Truly independent from Legislative brand and their own leadership higher in the Executive branch, all available information is they would have taken a commercial approach. But ultimately, just to get a reluctant Congress to agree to fund COTS and Commercial Crew, they had to move forward with SLS. And as Tim states, SLS does have some capabilities that Starship cannot match. But that all said, SLS is simply not sustainable in the long run. Starship (if they get refueling to work) will be a platform NASA can affordably use to achieve its long-term goals. And it won’t matter how many jobs will be lost across countless congressional districts.

  2. Rick is correct in his comments and has written an excellent book regarding the opportunity cost of SLS…I do recall some proposals for a SpaceX heavy lift booster using the proposed Merlin 2 engine…presumably this design would have followed a development path similar to Falcon 9…there was every chance we could have had a SLS equivalent about 8 years sooner

  3. Wow. This is a really great article. I hope you are persuasive enough to bring everyone together on this. Our space program will have a great deal of flexibility with all of these options. I also become frustrated trying to emphasize the need for both of these programs to succeed.
    A few things to think about:
    NASA’s mission is to put our astronauts back on the moon, and as you say, the government is very risk-averse. Starship could do this on the cheap, and probably will, but not with our astronauts. There is no escape system, and it is not human-rated for deep space per government standards. That being said- the capability offered by this mix of vehicles does offer us workarounds. If SLS fails, we may still be able to lift our astronauts to LEO in a Dragon, and have the Starship transport them to the moon in a human rated cargo container, such as one of the descent vehicles or even an Orion, if it can be made to fit. The descent vehicles would not need to withstand the rigors of a launch, but I assume they will be required to be radiation-hardened.
    Both SLS and Starship would be super-heavy lifters, but SLS will never land on the moon. I imagine that the Starship could lift a full load to LEO, refuel, deliver the load directly to the Lunar surface and make the return trip without requiring fuel at Gateway.
    Another thing to consider is appropriations. If there is a very sensitive payload, our Congress may require the mission to be performed by SLS. I know people don’t like to hear this, but this is the system that we have. Imagine that we have a modular nuclear power reactor that needs to be delivered. This type of mission will make it through the appropriations commitee much easier than commercial. Everything is sausage, but some things are more sausage than others.
    Correct me if I have made any errors here, I am just a guy.
    This has me very excited.

  4. Dear EA, I think that price for SLS is not correct if only four engines costs are near 600M$.

  5. Tim,

    I’ve been a bit discombobulated by the spat you have been having in Twitter about bias and tribalism creeping into your content. I’d like to point out something you possibly haven’t noticed wrt this video. The title is “SLS vs Starship” but the splash screen on YouTube shows a graphic that shouts “NASA vs Starship”. This the first thing people see and will obviously set their expectation for the content of the video. It’s absolutely obviously not what you mean and you go to great lengths to state that but the damage has already been done. I really think you should consider changing the splash screen to align with the title, and content, if that is within your control.


  6. Dude, I love you videos. I’ve been a space enthusiast my entire life of 64 years. BUT, enough with the meganewtons for thrust! This unholy term started creeping in the last decade. This makes perfect sense for the .0001% who can make sense of this in their brain. For the rest of the .9999% of us, please use what the good lord intended, and that is sealevel LBS thrust. Newtons for thrust makes as much sense as the Cro-magnons who thought that .0000000000000001 % of the world’s population wanted to see Reseau crosses on the Apollo lunar surface photos. So please: Pounds or Kilos sea, level or vacuum thrust, so that we don’t have to pause and convert it for it to make sense. Thank you.

  7. I watched your video until you said star ship claims to launch for around one million. This is ludicrous because you cant even buy the hydrogen for that, especially considering a refueling mission. As A reporter YOU have the responsibility to call out your source when hearing nonsense. YOU have just lost credibility. Even the 100 million is not even close when considering a refueling mission.

    I’m taking you at your word not to publish my email address.


  8. I don’t mean to sound really negative or something, just frank. Capability-wise, Starship blows the SLS out of the water. Also, when comparing design philosophies, it is important to point out when there is a superior approach. So far, SpaceX’s way is working much better. Different does not mean equal.

  9. I’m skeptical of the cost numbers used. The Saturn’s and Shuttle’s costs are the only numbers I trust. The space shuttle was supposed to be a real money saver too, but actually wound up costing 40 times more per launch than advertised, and 25% more than the Saturn it replaced when all the costs were counted. So I have to take any claims that the new rockets will cost less with more than a few grains of salt.

    One thing we learned from the “reusable” space shuttle was that it actually cost a lot more to refurbish and reuse a rocket than to build a new one. We also learned that regardless of the rocket used, the ground costs associated with getting a rocket and its crew ready for flight, lauching it into space, tracking it, recovering it, etc, etc, etc. were pretty much the same from one rocket to the next. And like it or not, the laws of physics are constant from one rocket to the next. No matter which rocket you use, the energy required to put one ton of anything into orbit is the same.

    This leads me to conclude that when all is said and done, SLS and Starship will wind up having costs comparable to or greater than that of the shuttle and Saturn. Now it may be that we don’t have any choice in the matter, that we lack the men, material and expertise necessary to build a working Saturn V rocket, and we are having to relearn how to make rockets again with spacex and SLS. I suspect we will have to relearn other lessons from Apollo as well.

  10. I still don’t know how SpaceX is planning their rockets to land and launch back from the Moon. Since there is only water , not methane available there, their engines doesn’t really suits for Moon lander. Unless we could find some carbon on the Moon too.

  11. Ref .
    The Replace – All , Vehicle – System
    Diag. , W.orkable D.etail W.D.s , Expl.

    + Post Image ?

  12. Starship design is still changing dramatically. The recent changes to the engine count are very curious. Thirty Three Raptor engines in the Super Heavy Booster, with another 9 Raptor engines in Starship is a lot of engines. Deep Space missions will require multiple refueling flights for a total of three Super Heavy/Starship launches and a total of 126 Raptor engine ignitions. Compared to the 10 ignitions required for an SLS Block-01B launch to Lunar orbit (2 x SRB, 4 x RS-25, 4 x RL-10)

    Add to that the risky propulsive landings, orbital refuelings, and booster catching, and Starship might easily become a operational complexity nightmare. Too much needed to go right, just to get a payload to Lunar orbit. I would strongly caution my Senators NOT to cancel SLS at this time. We may well need it in a race to Mars against the Chinese. Super Heavy / Starship are not a given.. not by a long, long, long shot.

  13. “In contrast to NASA, Starship is being built in a field in Texas by a patchwork team of SPACE COWBOY”….. At least it has a Team willing to innovate and try new things…. NASA is stale Government enterprise that hasn’t done anything radical in 50 years. The Artemis project is a joke and a waste of tax payers money.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: