SpaceX's fully reusable Starship launch vehicle has been touted as the next big leap for rocket technology.
So much so that recent reports suggest NASA officials are "shitting the bed" over the fact that Starship could "obsolesce all [other] existing launch systems."
But is NASA's Space Launch System (SLS) really so far behind Starship's capabilities? Let's start with a side-by-side comparison.
Which will be more powerful and more cost-effective?
The key difference between NASA's SLS rocket and SpaceX's Starship is perhaps best epitomized by NASA's own plans for its upcoming Artemis Moon missions.
Artemis I and II will fly around the Moon using SLS, while the Artemis III Moon landing will be carried out using a reusable Starship rocket to land astronauts and then return them from the lunar surface.
At just under 100m in height, SLS is a massive launch vehicle, though it's smaller than SpaceX's full-stack Starship attached to a booster, which measures 120m.
SLS will produce 9.5 million lbs of thrust and carry a payload capacity of 190,000 lbs (86 tons) up to low-Earth orbit (LEO), while Starship will produce 17 million lbs of thrust and will be able to launch 300,000 lbs (150 tons). On top of that, Starship will do it at a fraction of the cost due to its reusability — more on that below.
Which will be the first to reach orbit?
Both SLS and Starship are seemingly on the verge of reaching orbit, though both projects have recently hit setbacks.
Only shortly after SpaceX CEO Elon Musk suggested Starship could make its orbital maiden flight as soon as this month, the FAA announced it was once again delaying its environmental review of Starship to May 31. This is the latest in a string of delays for the FAA's review, which is required for Starship to launch to orbit.
NASA's SLS launch has also suffered from a string of delays, and it was recently rolled to the launch pad and then slowly rolled back for analysis following a number of issues. It can only launch to orbit after a successful wet dress rehearsal. Three attempts to conduct this rehearsal have so far failed, and the latest update suggests SLS will launch no earlier than August this year.
However, As SpaceX is relying on the FAA’s environmental review, it wouldn’t be a complete surprise to see SLS reach orbit first, despite the recent string of delays.
What are the biggest problems with SLS?
NASA's SLS is the iconic space agency's most powerful rocket yet. Though it's slightly shorter in height (100 m) compared to the Saturn V (111 m) rocket that launched the Apollo 11 mission, it is able to carry more than Saturn V's 7.5 million lbs payload. So why has the project been widely criticized in recent months and years?
It's largely down to the massive cost of SLS, as well as the highly-publicized string of recent delays. Designed in collaboration with Boeing, SLS has so far cost nearly triple the $10-billion projected development costs when it was first announced in 2011. By contrast, NASA has granted SpaceX at least $3 billion in taxpayer money towards the launch of Starship, though SpaceX is also relying on profits from its satellite launches and Starlink internet services to develop the fully reusable rocket.
What's more, NASA estimates that an SLS launch will cost approximately $2 billion, while Musk announced in SpaceX's latest Starship presentation that a Starship mission could cost a comparatively low $1 million.
That is largely down to the great benefit of full reusability, which will be displayed by Starship, driving down launch costs by allowing its parts to be reused.
NASA feels its SLS program is on track
Still, despite the criticism, NASA officials have stated publicly that the SLS program is going to plan. Artemis launch director Charlie Blackwell-Thompson recently noted there were five or six tanking tests before the first launch of the Space Shuttle more than four decades ago.
"Putting it into context, I would say we're within family of our experience in the past for first-time ops," she said at a recent press briefing. Though Starship's full reusability could revolutionize spaceflight, when compared with previous NASA launch programs, SLS might not be the disaster many are painting it to be. And no one has a better track record for launching astronauts into space than NASA.
As a point of reference, NASA launched more than 800 astronauts into space with its Space Shuttle program. Granted, the U.S. space agency has been around a lot longer than SpaceX, but the private space firm — which has sent a total of 22 astronauts to space since May 2020 — still has more than a little catching up to do. Such high numbers may be a long way off, though SpaceX hopes Starship will allow it to greatly increase its cadence of crewed launches starting later this year.