So long SLS -- we hardly knew ye?

It's beginning to look like this might be the epitaph etched onto NASA's $35 billion Space Launch System megarocket, a towering 322-foot beast of a rocket capable (if it's ever built) of lifting at least 70 metric tons of payload into orbit -- or visiting the moon, or even Mars.

Now, there's no certainty at this date that the Space Launch System, or SLS, will actually be canceled. In fact, responding to reports of delays and funding cuts in the program, NASA Administrator Jim Bridenstine recently reassured space fans that "NASA is [still] committed to building and flying the SLS."

Then again, the fact that Bridenstine felt compelled to say that at all suggests something is up -- and SLS's future may not be as secure as key contractors Boeing (BA 1.13%), prime contractor on SLS, Northrop Grumman (rocket boosters), Aerojet Rocketdyne (main engines), and Lockheed Martin (which builds the Orion capsule that sits atop all the above) might like.

So how big is the risk here?

Space Launch System

Here's an artist's impression of the Space Launch System...because it hasn't yet been built. Image source: Getty Images.

Follow the money

Consider the evidence.

The Trump Administration released its Fiscal 2020 Presidential Budget Request for NASA earlier this month, proposing that the National Aeronautics and Space Administration be funded with $21 billion in the fiscal year beginning Oct. 2019. That's nearly a 9% increase from the NASA budget proposed in President Trump's first year in office, but 2% (or about $500 million) less money than Congress awarded the agency last year, for example.

Many programs within NASA are being cut, including funds for earth science projects (down 8%) astrophysics (down 20%), and a "Wide-Field Infrared Survey Telescope" (phased out entirely). In terms of sheer dollar value, however, few programs got hit harder than the Space Launch System (SLS), which could see its funding cut by $375 million as NASA "defers" development of a planned "Block 1B" upgrade to the rocket's lift capacity .

Now, don't cry too hard for SLS. The project is still slated to receive nearly $1.8 billion in funding next year, with a further $1.3 billion tacked on to develop Lockheed's Orion Crew Vehicle, and more than $800 million for a "Lunar Gateway" for Orion to visit -- preparatory to a moon landing.

Still, it appears that NASA may be losing confidence in its pet project, as demonstrated by some of the other things NASA administrator Bridenstine revealed.

Check out the latest earnings call transcript for Boeing.

Move over SLS. SpaceX can handle this

A couple of weeks ago, while giving testimony before the US Senate Committee on Commerce, Science, and Transportation, Bridenstine warned senators that the Space Launch System (SLS) "is struggling to meet its schedule" for an initial unmanned launch around the moon by June 2020. After suffering innumerable delays and schedule misses throughout its development, Exploration Mission-1, which would use an SLS rocket to sling an unmanned Orion capsule past the Moon and then bring it home again, could potentially be postponed into 2021, say analysts .

Now, there are still options for using SLS to reach the moon in 2020. Just this week, for example, NASASpaceflight.com reported on a potential NASA move to curtail a planned six-month "Stage Green Run" program including an eight-minute test firing of SLS's RS-25 main engines (simulating the strain the engines would undergo when launching to space). Instead NASA would authorize a brief five-second static fire test firing on-site at Kennedy Space Center, shaving months off the timeline for launching EM-1.

Now, cutting corners on quality assurance may not be the best way to ensure a problem-free launch. But at least with the unmanned EM-1 mission, it would pose no risk to human life. If it accelerates the SLS program, and brings the rocket closer to completion, it's likely Boeing would be willing to sign off on the idea.

Especially when you consider the alternative.

In his Senate testimony, Bridenstine suggested that in the interests of not delaying EM-1 any further, NASA might consider using rockets other than SLS to launch the mission. For example, one heavy lift rocket (such as a ULA Delta IV or SpaceX's Falcon Heavy) could be used to put Orion into orbit. A second rocket could then lift a fully fueled third rocket into orbit to mate with Orion and serve as its propulsion to the moon and back.

It wouldn't be a one shot mission around the moon, as an SLS launch could provide. Then again, Delta and Falcon are both proven launch vehicles and ready to fly. SLS isn't.

The upshot for space-company shareholders

But here's the thing: If NASA launches EM-1 using commercial rockets other than SLS, it would undermine the whole idea of SLS being essential to deep spaceflight. Despite Bridenstine's protestations to the contrary, a successful EM-1 mission without SLS could weaken the case for building SLS at all, putting billions of development dollars at risk for companies such as Boeing, Northrop Grumman, and Aerojet Rocketdyne. It could also threaten the anticipated ongoing revenue stream from SLS, which is expected to cost upwards of $1 billion per launch.

Now, the news isn't all bad. Because Boeing and Lockheed co-own ULA, and share in revenues from ULA launches, an EM-1 mission using a Delta IV rocket would at least give them a chance at collecting some revenue from NASA's efforts to return to the moon. The bigger risk here (to Boeing investors -- Lockheed is assured of getting revenue from Orion no matter what rocket carries it) is that NASA might decide to launch EM-1 using SpaceX Falcon Heavy rockets.

Such a decision would pose a real risk to Boeing -- and the longer it takes them to get a working SLS built, the greater that risk becomes.