On Monday NASA issued a brief release stating that it will hold a briefing Tuesday afternoon “discuss an agency decision that will define the next transportation system to carry humans into deep space”. That’s led to some speculation that NASA has reached a decision on the architecture of the Space Launch System (SLS) heavy-lift vehicle. However, NASA officials speaking at a conference session last week gave no indication that a design decision was imminent.
“The agency is still working on what the integrated plan will be” for its exploration program, said Dan Dumbacher, deputy associate administrator for NASA’s Exploration Systems Mission Directorate, during a panel session at the National Space Society’s International Space Development Conference (ISDC) in Huntsville, Alabama, on Thursday. “We are working that internally. That will become more public in the late spring/early summer timeframe” with the delivery to Congress of a report on those plans. (He later said that report would be done in late June or early July,) “We are working very hard to get all of the analysis done that we need to document those plans.”
Much of the hour-long ISDC panel session, with the vague title “Flight System Development Forum”, dealt with the process of developing a design for the SLS, although with fewer details about the design itself. “Some might ask what’s the biggest challenge for the SLS going forward,” said Todd May, the SLS program manager at NASA Marshall Space Flight Center. “I really think at this point, based on the last year or so, it’s understanding and wading through the minefield of constituencies.” That includes, he said, “internal” constituencies that advocate various technical approaches as well as “external” constituencies, such as contractors, other government agencies, Congress, and the “commercial movement”. “That’s a pretty complex web, when you add all of that up, of constituencies.”
As teams evaluate a number of technical approaches, another area of emphasis has been how to efficiently manage such a program. While other agency teams looked at configurations based on liquid hydrogen or RP-1 propellants, said Garry Lyles, SLS chief engineer at NASA Marshall, another team has looked at the application of lean manufacturing concepts. “We are not going to operate the same way that we have been operating and come up with a new vehicle configuration and expect it to be affordable,” he said. “In other words, there is no perfect configuration.”
Panelists, though, offered fewer details about how that translates into a specific SLS design and how it will be procured. “We have not made a final selection on the procurement approach,” May said. “We certainly have the data we need to make that decision.” Dumbacher added that NASA will release those plans “as quickly as we can” after the delivery of the Congressional report. Lyles said a lot of major factors being weighed during the design process include tank diameter, engines (including engine costs, since the engines will not be reusable), and “complexity on the ground”, namely, the work required at the launch site to prepare the vehicles for launch. After the panel, May said their “end state” for the vehicle’s payload capacity is 130 tons, since that is what’s considered necessary for human Mars missions, but wouldn’t comment on any interim capacities.
“We want to get in to building hardware and get into the development as quickly as anyone does,” Dumbacher said. “I think that’s true of everyone involved in the process. We all want to be making progress as quickly as possible. We’re doing everything we can to get the right questions answered, do the right homework to make sure we’re doing the right things, and then get on with the development at hand and get moving on the next level of exploration.”