There is an old saying at NASA, “Failure is not an option”. Unfortunately due to once again having congress design a rocket instead of the engineers at NASA “Failure is an option”. Indeed it may be an inevitable outcome. NASA will be announcing a new launch date for the Artemis SLS rocket after failing twice to launch. Both launch scrubs were due to the use of super cold liquid hydrogen. This is the fuel that the new booster uses. As you might imagine managing a liquid this cold is very difficult to use and manage. So difficult in fact that when NASA was looking at the replacement for the Saturn V, engineers we dead set against using it. The issues in building engines that use it in addition to the difficulties in storing it make this fuel very costly and inefficient.
In contrast SpaceX looked at fuels and for the reasons I just stated they decided against liquid hydrogen. They choose to use kerosene for the Falcon and liquid methane for Starship. Kerosene has the advantages of being easy to manage at room temperature, no specialize storage, easier engine management etc. Methane (CH4) is cheap, it easy to store in liquid form, significantly denser than hydrogen, does not leak as easy, it does not require insulation on the fuel tank, and the over all design of the rocket is simpler.
NASA is not at fault for their fuel choice, our government is. NASA was given the mandate to use the Shuttle engines on SLS. Therefore they were stuck with no other option for fuel. Their protests were useless as the bureaucrats dictated the engineering decision. (Remember the Space Shuttle blew up for this exact same reason).
Decisions like these assure jobs in congressional districts but they also assure ridiculously high cost for the final rocket. At two billion per launch the SLS is the most expensive rocket in history. While it is an engineering marvel it is also a sort of Rube Goldberg machine in that so many overly complex and useless technologies had to be implemented in it. Ultimately it is the cost that will kill the SLS. At 2 billion per launch NASA simply cannot afford to spend 10 percent of it’s yearly budget per launch. This is a huge chunk of the budget to spend on launch vehicles. This is compounded further when you look at alternatives that are not far of such as SpaceX that will be much cheaper.
It is sad that so many people have chosen to bash NASA and the issues with the SLS. The engineers did the best they could with the poor choices that were mandated to them by congress and politicians. The end result is typical for a government project and not the fault of the hard working people at NASA that knew they were being forced to use bad technology. None the less they created this new rocket and while it exists we should enjoy the show…why not, we paid for it after all.