Critical hardware tests are the next step in NASA’s development of its Space Launch System rocket, a super heavy lift expendable launch vehicle that is part of the agency’s deep space exploration plans, including a crewed Mars mission. However, because of multiple constraints, it seems that NASA’s scheduled launch date, June 2020, may be postponed.
NASA is targeting late 2020 for the test launch of the SLS rocket and the Orion spacecraft – known as Exploration Mission-1 – but the flight is not likely to happen until 2021. Part of the reason is the unprecedented 35-day government shutdown, says Kathryn Hambleton, NASA’s exploration program spokesperson: "NASA is still assessing impacts as a result of the shutdown, but we are still working toward a launch in 2020.”
The first step of core stage testing is that of a hydrogen tank that is identical to the one used for the mission. The tank will undergo a number of stresses and loads that it will endure both during launching and flight. The core of the rocket will consist of a large liquid hydrogen fuel tank, a smaller liquid oxygen tank and four engines.
After the liquid hydrogen fuel tank is tested, a similar structural test of the liquid oxygen tank will undergo a so-called “green run” test, for which NASA will integrate the two tanks with the rocket’s RS-25 engines and fire them through the standard rocket launch. There’s no date for that test yet, but it will likely determine the actual SLS rocket launch date. If the green run test happens in 2019, the 2020 rocket launch will remain a possibility. Should technical problems occur – and usually they do during the integration and testing of large rocket programs – the launch will be postponed.
For the upper stage, NASA’s original plan was to use it for a single flight, but now it seems that the agency plans to use the Interim Cryogenic Propulsion Stages (ICPS) for three flights or more. The new issue, then, is the viability of the second stage, known as the Exploration Upper Stage. The work, contracted to Boeing, has slowed down as NASA is looking at alternative designs to bring down costs. It is considering the use of the Falcon Heavy Rocket for the Europa Clipper mission, which will involve an orbiter to study the Galilean mon Europa through flybys in orbit around Jupiter. In late 2018, NASA Administrator Jim Bridenstine said in an interview that the agency is focused on core stage development now rather than the Exploration Upper Stage. "We have closer alligators to the canoe right now, and that would include the core stage." He did add, however, that the Exploration Upper Stage remains a critical component.
With the original launch date in 2017, the SLS rocket is now at least three years behind schedule. And with the budget of $2 billion per year, delays are having an impact on the costs for NASA. If the agency is to succeed in launching the SLS in 2020, it will likely require at least an additional $1 billion in funding.