Remind me again: Why exactly do we need the SLS?

Yesterday, I reported on the steaming pile of anti-science that is the Presidential Budget Request for NASA for Fiscal Year 2020. It cuts major NASA missions, education, climate science, and more. The good news here is that Congress is highly unlikely to let this stand; in previous years where Trump has cut important programs, Congress has reinstated the funding for them.

Now, I need you to bear with me here. The NASA Administrator dropped a major bombshell in a Congressional hearing yesterday, and to appreciate it fully you need a little background.

An important part of the 2020 budget dealt with Exploration — sending crewed vehicles to the Moon and beyond. This consists of several parts, including three big projects: the Space Launch System (SLS) rocket, the Orion Crew Capsule, and the Lunar Gateway.

The Gateway is a partnership between various space agencies (including ESA, NASA, JAXA, and others) to build a space station of sorts that will be in high orbit around the Moon. It would be used for crew to rendezvous with before descending to the lunar surface, and could be outfitted for much more ambitious long-range missions to Mars and beyond. Crew could be sent there via Orion, or commercial capsules (like the Boeing CST-100 or SpaceX Crew Dragon).

Orion itself is a big capsule, similar in shape to, but much larger than, the Apollo capsule, capable of transporting up to six astronauts. It's a major player in NASA's new Moon to Mars project.

Artwork depicting NASA's Orion capsule with an ESA service module attached orbiting the Moon. Credit: NASA/ESA/ATG Medialab

Photo: NASA/ESA/ATG Medialab

The SLS is the foundation of it all. Bigger and more powerful than a Saturn V, it would be capable of throwing huge amounts of payload into space, including the Orion capsule and the Gateway together in a single launch.

However, SLS has been plagued with huge cost overruns and long delays. In the new 2020 budget, funding for both Orion and SLS are cut back, and more money allocated to the Gateway. The reasoning in the budget outline is that the first stage of the SLS is so badly over budget and behind schedule that NASA needs to scale back working on the enhanced upper stage part of it and get the first stage done. As I mentioned in yesterday's article, Eric Berger at Ars Technica has lots of details to fill in the blanks here.

However, because the upper stage would be deferred, SLS would no longer have the capability in the near future to launch payloads to the Moon. But that's one of its biggest reasons SLS is being built in the first place! So that's stunning right away.

But there's more (lots more, but one at a time here): in the budget, they also say that NASA can save $700 million dollars by launching a planned mission to Jupiter's moon Europa on a Falcon Heavy. This was originally planned for the SLS, so in effect they're saying we don't need SLS for deep space science missions… another one of its big goals. Again, stunning.

That leaves one thing for SLS to do, and that's using the first stage to get Orion into Earth orbit at least. And here is where things get really wacky.

On Wednesday, NASA Administrator Jim Bridenstine appeared before the Senate Committee on Commerce, Science, and Transportation to talk about the future of human exploration of space. He discussed the goal of sending an uncrewed Orion capsule around the Moon by a June 2020 deadline. Called Exploration Mission 1 (or EM-1), it is to be the first real test of the Orion capsule on a lunar flight.

This is when Bridenstine dropped his bombshell. He admitted that SLS cannot possibly be ready by that date, and he also said that NASA should respect the 2020 deadline. So, in order to achieve this goal, he proposed a different scenario: NASA can use a commercial launcher to put Orion into Earth orbit with a service module (a lower half that has propulsion and so on, much like the Apollo Service Module on which the Command Module capsule sat). A second launch would then send an upper stage to rendezvous and attach to Orion, and that would then be used to loft the whole assembly around the Moon. Watch:

Do you see what he's saying here? By commercial launcher he means either a Delta IV Heavy or a Falcon Heavy; they are the only rockets capable of doing this. But if that's the case, we don't need SLS to launch the Orion crew capsule to the Moon.

But that's the last of its big raisons d'être. Without that, why build it at all?

Everything NASA wants to use SLS for can be done using smaller, reliable, and vastly (vastly) cheaper rockets. SLS will cost over a billion dollars per launch, and at best will launch once per year. There's only been a single Falcon Heavy launch, but it's not too much to extrapolate from Falcon 9 launches that it may be a very reliable system… and it's hugely less expensive than SLS. The Delta IV Heavy is more expensive than the Falcon Heavy, but has proven itself to be reliable. Either one would be a fine replacement for SLS; you’d need multiple launches for some missions, but that's just what Administrator Bridenstine is saying we need to do for this first EM-1 launch!

Mind you, he also said the nation needs SLS, and that EM-2, the second mission, would then use SLS. But I'm wondering about that now.

To be clear, it's not like you can just swap out rockets. Mating the Orion to a different rocket means building a whole different structure, and the idea of multiple launches means setting up a way to get everything together in orbit and assembling them, and it's unclear how that would work. Bridenstine as much as said that this idea needs a lot of setup.

But the fact that he said this at all is astonishing.

Let me be clear: I have not been a proponent of SLS since it was first announced. I said it was too big, too expensive, and too complicated, and will almost certainly suffer delays and cost overruns. I also think that it makes more sense to use smaller (but still powerful) rockets to send up multiple pieces for each mission. That's far less expensive, easier to have redundancies, and could be done on a faster timeline than anything SLS can match. We have these rockets now. We've already spent $12 billion for SLS and it has yet to fly, it costs $2 billion more per year to develop and build, and again each launch will cost over a billion.

So where does this leave us? Remember, this is all due to the Presidential Budget Request, and that has to be approved by Congress. Congress will absolutely make big changes to the PBR, and the Senate loves them some SLS, especially Senator Richard Shelby of Alabama, where the SLS project is managed. I can only imagine the scene in his office this morning when he saw Bridenstine’s testimony. Yikes.

Anyway, I fully expect they will reinstate funding for SLS when it comes time for them to work out their own budget. I don't expect SLS to get canceled outright, but Bridenstine's pushback on it makes me hopeful that perhaps we may not be entirely saddled with it in the future. It's a colossal drain on NASA resources — time, money, and expertise — and I'd far rather see us using multiple launches on commercial rockets to do its work.

Per ardua ad astra. This ain't over. Ardua indeed.