The panel tasked by U.S. President Barack Obama to review NASA’s human spaceflight program got a hard dose of budgetary reality last month by one of its own — former NASA astronaut Sally Ride. Ms. Ride, in one of several public presentations to the panel July 28, said the group’s final report to the White House should incorporate two assumptions: that the space shuttle, now slated to conduct its final flight in September 2010, will continue to operate through March 2011; and that U.S. support to the international space station will be extended at least five years, from 2015 to 2020.

That some panel members initially seemed taken aback by this assessment is in itself surprising: Given the shuttle’s average flight rate of just over three per year since its return to operations following the 2004 Columbia accident, one cannot expect the fleet to fly out its remaining manifest of seven missions over the next 14 months. Meanwhile, though NASA’s formal obligations to the space station program expire in 2015, few expect that a $100 billion investment will simply be scrapped after just five years of full utilization.

Given that the space shuttle and space station each cost NASA somewhere in the neighborhood of $3 billion annually, the budgetary implications of Ms. Ride’s assessment are significant. Even if one assumes — however unrealistically — that NASA retires the shuttle at the end of the 2010 fiscal year and walks away from the space station in 2015, the agency was going to be very hard pressed to return astronauts to the Moon by 2020, a goal set by former U.S. President George W. Bush and later endorsed by Mr. Obama. This is why Mr. Obama ordered up the human spaceflight review in the first place.

Norm Augustine, the former Lockheed Martin chief who is leading the review, succinctly summed up the situation at the end of the July 28 meeting: “Unless additional money is added to the program, there’s a very tough tradeoff to be made.”

At the next public meeting Aug. 5, the panel effectively spelled out that tradeoff in presenting seven human spaceflight options for NASA: Of the three that fit within projected human spaceflight budgets over the next decade — as extrapolated from the administration’s current five-year spending profile — the one that assumes NASA supports the space station through 2020 defers exploration beyond low Earth orbit indefinitely.

This isn’t rocket science; it’s simple budgetary reality. What it means is that the White House and Congress must either find a way to boost NASA’s spending profile, which is hard to justify given the nation’s huge debt — then again, the government has a multibillion-dollar program that essentially bribes citizens to buy new cars — or, as former NASA Administrator Mike Griffin suggested in a letter to the panel, “we should stop talking about larger goals” in space exploration.