WASHINGTON — NASA is currently spending money on its key exploration programs at a rate that assumes Congress will approve a budget increase in the next month, a move that could delay some efforts should the additional funds not materialize.

Bill Hill, deputy associate administrator for exploration systems development, told a meeting of the NASA Advisory Council’s human exploration and operations committee here Nov. 4 that NASA was funding programs like the Space Launch System and Orion spacecraft at a higher rate than specified in the continuing resolution (CR) currently funding the agency.

“Today we’re running hot. We’re running based on what we saw in the draft House and Senate levels,” Hill said. “But if we don’t ultimately achieve those levels in an appropriations bill, then we’ll have to power back and replan.”

The CR that currently funds NASA and the rest of the federal government through Dec. 11 keeps agencies at their fiscal year 2015 levels. SLS, for example, received $1.695 billion, according to the agency’s final operating plan for 2015. However, an appropriations bill passed by the House in June would provide SLS with $1.85 billion in 2016, while a Senate version gives the program $1.9 billion. NASA had requested just $1.36 billion for SLS in its original 2016 budget proposal.

That difference could determine whether NASA moves ahead this year with plans to develop the Exploration Upper Stage, a more powerful upper stage for the SLS that the agency hopes to have ready for the second SLS mission. A decision whether to proceed with the stage hinges on the outcome of the 2016 budget.

“The difference in appropriations between where the continuing resolution is and what we saw in the draft appropriations in both the House and the Senate for SLS will determine whether we can continue the effort” on that upper stage, he said.

Hill said the program is ready to hold a preliminary design review for the new stage in 2016, assuming the program gets the increase offered in the draft bills. “If the appropriations levels don’t come in as we expect, we may have to turn that off for a year, and that’s not going to be a good thing to do,” he said.

A delay in development of the Exploration Upper Stage could force NASA to continue to use the Interim Cryogenic Propulsion Stage (ICPS), a modified Delta 4 upper stage that will be used on the first SLS mission in late 2018. The ICPS would require additional work to be human-rated should it be flown beyond that first, uncrewed SLS mission, an expense Hill said NASA wanted to avoid.

One issue about using the ICPS beyond that first mission is its vulnerability to damage from orbital debris and micrometeoroids. Hill said that concern led mission planners to decide to carry out a translunar injection burn on the first orbit after launch, rather than the second as originally planned, to minimize exposure to debris. That approach, he added, would not work on later crewed missions, when the spacecraft would likely spend several orbits around the Earth checking out systems before departing.

Hill didn’t identify any other elements of SLS or Orion that could be in danger of delays should funding fall short of the agency’s projections. Both SLS and its ground systems are on schedule to support a first launch in June 2018, he said, while Orion would be ready for that launch in September 2018. Hill also said NASA is also holding an August 2021 date for the first crewed Orion launch on SLS, although the agency announced in September that this mission could be delayed to as late as April 2023.

“We are hopeful that we will get some sort of omnibus appropriations before the end of the calendar year, and we’re going to need that,” Hill said. “If we have to maintain continuing resolution levels, we could be challenged in a couple of significant areas.”

A budget increase appeared more likely after Congress approved in late October a two-year budget deal that raised spending caps for both defense and other discretionary spending. Those increases, though, have yet to be incorporated into revised appropriations bills, and there is some concern that debate over policy provisions that could be tacked onto the spending bills might delay or even block their passage.

Greg Williams, deputy associate administrator for human exploration and operations, said at the committee meeting that the outcome of the appropriations discussion was still uncertain. “We don’t really know how we’re going to come out” in the 2016 budget, he acknowledged, although noting that the increased budget caps “is good news so far.”