On Halloween, NASA posted a document that provides some perspective on the agency's long-term plans for the Space Launch System rocket. This is the agency's titanic booster that has been under development since 2010, has an annual budget of more than $2 billion, and will not fly before at least 2021. The new document, known as a Justification for Other Than Full and Open Competition, explains why NASA rejected a lower-cost version of an upper stage for its rocket.

Early on, the space agency opted to build the large SLS rocket in phases. The initial version, Block 1, would have a placeholder upper stage. As a result, this initial variant of the rocket would be somewhat limited in its capabilities and only marginally more powerful than private rockets—most notably SpaceX's Falcon Heavy and Blue Origin's New Glenn boosters—developed without the deep pockets of US taxpayers.

The much more capable Block 1b of the SLS rocket will stand apart from these private rockets. With its more powerful second stage, known as the Exploration Upper Stage, it will more than double the lift capacity of these private rockets. Additionally, it will have the capability to launch both large amounts of cargo and the crewed Orion spacecraft at the same time.

At the outset of the program, NASA chose Boeing to build both the core stage of the SLS rocket, as well as the Exploration Upper Stage. In recent years, Congress has appropriated hundreds of millions of dollars for the agency and Boeing to design this new upper stage to fit on top of the SLS rocket. The agency has yet to move into development of the upper stage, however.

There are several reasons for this. NASA wants Boeing to finish the SLS rocket's core stage first, as it is already four years late. Moreover, because of Boeing's performance on the core stage and projected costs of the Exploration Upper Stage, the agency was curious if there were other aerospace companies interested in building a powerful upper stage for the SLS rocket.

Two years ago this frustration, in part, led NASA to issue a request for industry to provide a "low-cost replacement" for the RL-10 rocket engine that powered the Exploration Upper Stage, as well as perhaps an entirely new stage itself. An agency spokesperson said at the time the request sought to "open up the field of possible responses" and reduce costs of the SLS rocket's proposed upper stage.

Since that time, the issue of the Exploration Upper Stage has largely simmered behind the scenes. The new document released on Halloween, however, provides some clarity for what happened. And instead of opening upper stage bidding into a formal bidding process, NASA decided to stick with Boeing's version of the Exploration Upper Stage. Because this was a non-competitive process, NASA had to justify it with the new document.

The bidders

In the new paperwork, we learn that Boeing and its long-time competitor, Lockheed Martin, proposed to build the Exploration Upper Stage as designed, with four RL-10 rocket engines manufactured by Aerojet Rocketdyne. In addition, Blue Origin submitted an "alternate response" to the upper stage design.

This design was based upon Blue Origin's BE-3U rocket engine, a modified version of the motor that powers the New Shepard launch system, which will also fly in the upper stage of the company's New Glenn rocket. A single BE-3U engine has more thrust than four RL-10 engines combined. So Blue Origin likely proposed an upper stage powered by a single BE-3U engine.

The costs

Rocket engine costs are something of a black box, but it is likely that a single BE-3U engine will cost about the same, or less, than a single RL-10 engine. Therefore Blue Origin's upper stage would almost certainly cost significantly less than the Exploration Upper Stage proposed by Boeing. (NASA's justification document redacts the agency's investment to date in the Exploration Upper Stage.)

Various sources have suggested wildly different cost estimates for the Exploration Upper Stage. But one thing we know for sure from NASA's 2017 request of industry is that the agency sought to cut costs and must have believed Boeing's price was too high.

How high was it? We can make an educated guess. Using the Advanced Missions Cost Model, we can roughly estimate the development cost of an upper stage with a dry mass of 13.1 metric tons at $2.5 billion (we rated the development difficulty factor as "high" rather than "very high"). Based upon this model, the total cost for eight Exploration Upper Stages—which NASA announced in October it was beginning to order—came in at $8.6 billion. Subtracting development costs, then, this gives us a per-unit cost of each Boeing upper stage of $880 million.

It is not difficult to see the quandary here for NASA. Even if the agency succeeds in the herculean task of bringing the cost of a single core stage down to $1 billion, flying the Exploration Upper Stage will make each launch of its SLS rocket cost on the order of at least $2 billion. This is not the foundation of a sustainable space program. Indeed, NASA would find itself in the situation of the SLS rocket being too expensive to fly often, and unable to fly it often enough, to eventually make the SLS rocket affordable.

Despite this, in NASA's new justification document, the agency rejects Blue Origin's less-costly alternative.

Justification

NASA sets out three reasons for not opening the competition to Blue Origin. In the document, signed by various agency officials including the acting director for human spaceflight, Ken Bowersox, NASA says Blue Origin's "alternate" stage cannot fly 10 tons of cargo along with the Orion spacecraft.

Moreover, NASA says, the total height of the SLS rocket's core stage with Blue Origin's upper stage exceeds the height of the Vertical Assembly Building's door, resulting in "modifications to the VAB building height and substantial cost and schedule delays." Finally, the agency says the BE-3U engine's higher stage thrust would result in an increase to the end-of-life acceleration of the Orion spacecraft and a significant impact to the Orion solar array design.

Despite these reasons, perhaps the overriding rationale in the NASA document is that moving away from the Exploration Upper Stage's current design would require time the agency does not have in its rush to reach the lunar surface by 2024.

NASA would "incur additional costs and schedule risk due to changes in the design and analysis cycles," the document states. "The alternate solution is a heavier stage with a different length and diameter than EUS. New wind tunnel models, load cycles, and integrated dynamics models would need to be produced and verified."

A real competition?

The irony in this document is that NASA said it would consider opening up a competition for the SLS rocket's new upper stage in 2017. And then two years later it told a bidder that proposed a commercial, cheaper upper stage that its bid failed because NASA and Boeing had already designed their rocket around Boeing's proposal. This seems like less than a fair competition.

Moreover, NASA is already procuring an interim upper stage for the SLS rocket from United Launch Alliance, a company co-owned by Boeing and Lockheed Martin. United Launch Alliance has extensive experience with the RL-10 engine and building upper stages. It also has tooling and factory space for this purpose, and it likely would have been cheaper and faster for NASA to contract with ULA. However, this would have meant that Boeing had to share any profits from the upper stage with Lockheed.

As a result, NASA has gone with a contractor that significantly under-performed on the SLS core stage, which is years behind schedule, billions of dollars over budget, and yet to prove itself in flight. Now it has bet the future of its deep space exploration program for at least the next decade on the same company. NASA fans can only hope that Boeing builds rockets as well as it does lobbying coalitions.