Trevor Mahleman
After three attempts to complete a critical test of fueling a Space Launch System rocket, NASA decided to take a break.
Saturday Night Space Agency Announce plans to roll off the large SLS rocket from the launch pad at the Kennedy Space Center to the Vehicle Assembly Building in the coming days. This represents a significant step back for the program, which since April 1 has attempted to complete a “rehearsal” test, during which the missile is refueled and operational within 10 seconds of launch.
The decision comes after three attempts over the past two weeks. Each attempt to refuel was thwarted by one or more technical problems with the missile, mobile launch tower, or ground systems providing the fuel and gases. During the last attempt, Thursday, April 14, NASA successfully loaded 49 percent of the primary stage liquid oxygen fuel tank and 5 percent of the liquid hydrogen tank.
While this is an advance, it did not include the more dynamic part of the test, during which the rocket is fully refueled and pressurized; Ground and computer systems are put into the final countdown when each variable is closely monitored. NASA had hoped to complete this rehearsal test to work out the kinks of the complex launch system so that when the rocket launches later this year for its actual launch, the countdown will continue fairly smoothly.
NASA said its contractors, as well as its agency, will use the next several weeks to address problems that arose during refueling tests when the SLS rocket returns to the large vehicle assembly building. For example, Air Liquide, a supplier of gaseous nitrogen system, will upgrade its capabilities. NASA will also replace a defective check valve on the rocket’s upper stage, as well as fix a leak in the mobile launch tower’s “secret tail service mast,” the 10-meter-high structure that provides the missile’s thruster and electrical lines to the pad.
The space agency’s announcement did not provide any information about the schedule’s effects. It seems likely that it will take a week or so to prepare the SLS rocket and return it to the Vehicle Assembly Building. Work on the rocket at that location will likely take at least most of May.
NASA will then have to make some tough decisions. You can choose to roll the rocket and the movable launch tower onto the platform a second time and try to complete the wet test exercise. Then, following normal procedure, NASA will roll the rocket into its assembly building to arm the Flight Safety System, before rolling for a third time to the launch pad for takeoff. It appears that the earliest possible launch of the SLS rocket in such a scenario would be in August, but its launch would most likely be in the fall.
Another option that NASA could pursue is to start testing the wet clothes and complete them on the platform, then go ahead and launch them in a few days if that works. Under such a scenario, NASA may be able to launch the SLS rocket in June or July. However, this can be risky due to the flight safety system.
During a conference call on Friday, Artemis launch director Charlie Blackwell-Thompson confirmed that there is a 20-day timeline once the flight safety system is armed. (This is a range safety mechanism used by all orbital missiles that destroy the booster if it veers off course.) After the system is activated, it will take about a week to make final preparations at the Vehicle Assembly Building and a week to roll over to the launch pad and make preparations there. That would leave just one week to test refuel, recycle goods, and possibly try one or two firings before the 20-day window closes.
In other words, this means that the wet dress test should be virtually flawless, and then the launch attempt should also be flawless. It could also mean that summer weather in Florida – when there are many thunderstorms and other extreme conditions – has to cooperate.
Finally, NASA engineers must balance a host of other factors, such as wear on the rocket, side-mounted reinforcements exposed outside, as well as seemingly infinite age considerations with the hardware. For example, agency officials closely follow the health of the fuel in solid rocket boosters, which have been stacking for about 16 months, among other things.
Nonetheless, NASA appears confident that it will get through this painful denting of the SLS rocket: a program that is now 11 years old and in which NASA has invested more than $30 billion in rockets and ground systems now being tested.
“I have no doubts that we will finish this test campaign, we will listen to the hardware, the data will lead us to the next step,” Blackwill Thompson said Friday. “And we’ll take the appropriate steps, and we’ll launch this car. I don’t know exactly what that date is, but there’s no doubt in my mind that we’ll finish the test drive, and we’ll be ready to go fly.”
