The Aug. 24 failure of a Russian Soyuz-U rocket carrying a Progress capsule filled with international space station supplies illustrates, as much as anything else, the tendency of politicians to interpret events in ways that suit their pre-existing agendas. For U.S. lawmakers who spoke out about the failure, its meaning appears closely tied to where they stand on a pair of NASA human spaceflight initiatives that, while complementary in theory, are in reality competitors for near-term funding.

Within hours of the mishap, Sens. Kay Bailey Hutchison (R-Texas) and Richard Shelby (R-Ala.) issued a joint statement urging NASA to get moving on the Space Launch System (SLS), the space shuttle-derived heavy lifter mandated by Congress to serve as a backup to commercially operated space station crew taxis and to support astronaut missions to deep-space destinations. “This failure underscores the importance of successful development of our own National capabilities and at the same time demonstrates the risks with having limited options for [international space station] resupply and crew rotation,” they said.

Not surprisingly, Rep. Dana Rohrabacher (R-Calif.), a supporter of U.S. President Barack Obama’s plan to hand space station logistics and crew transport to commercial operators, saw a different imperative. “We need to get on with the task of building affordable launch systems to meet our nation’s needs for access to low Earth orbit, instead of promoting grandiose concepts which keep us vulnerable in the short and medium terms,” Rohrabacher said in a prepared statement. “The most responsible course of action for the United States is to dramatically accelerate the commercial crew systems already under development.”

Sens. Hutchison and Shelby didn’t specifically mention NASA’s Commercial Crew Development effort, designed to field an astronaut transport in the near term, but they did note that the companies under contract to deliver cargo to the space station on a commercial basis are behind schedule.

Never known for subtlety, Rep. Rohrabacher cast SLS and commercial crew as direct competitors; he urged NASA to transfer funds from other programs, specifically including the heavy lifter, to accelerate development of privately owned crew taxis.

Regardless of one’s priorities in U.S. human spaceflight, there is no denying the significance of the failure, attributed by Russian authorities to a malfunction of the Soyuz-U’s third stage. In addition to being the primary means of launching cargo to the station, the Soyuz-U is similar in design to the Soyuz-FG rocket — the vehicles’ third stages are a particularly close match — which currently is the only means of launching crews to the orbiting outpost. Both Soyuz variants are grounded pending the findings of a Russian-led failure investigation; a Soyuz crew mission scheduled for September has been delayed, and NASA says the station will have to operate with half its normal crew size between mid-September and mid-November. If the Soyuz-FG is not cleared by mid-November, NASA, Roscosmos and the other space station partners will have to temporarily abandon the outpost altogether, NASA officials say. Leaving the space station untended increases the risk of losing it should something go wrong, NASA officials say.

Sens. Hutchison and Shelby certainly were justified in saying the loss of the Progress and its 2.9 metric tons of cargo validated Congress’ addition of one more mission to the shuttle manifest. That recently completed flight, ordered up in the same bill that directed NASA to build the SLS and Multi-Purpose Crew Vehicle, ensured that space station crews remain well provisioned in the near term.

Far less credible is their suggestion that the SLS solves the problem of NASA’s dependence on Russia for space station crew transport. The SLS as designed — by lawmakers — is not something that will be available in the near term under any realistic funding scenario. Nor is it really suitable as a government-owned backup to commercial crew capabilities; it’s much too big and in all likelihood too costly. Ironically, funding it at the level sought by its supporters would draw funding away from the commercial crew initiative, as the House version of the 2012 NASA appropriations bill will attest. That proposed legislation would boost funding for SLS above the president’s request while leaving NASA with insufficient funding to make much headway on its nascent Commercial Crew Development program.

That the Soyuz-U failure underscores the vulnerability of the space station program to a single source of crew transport is difficult to dispute, even granting Russia’s proven ability to return its rockets to service relatively quickly. If the objective is to address that vulnerability, and do so in the near term, then Rep. Rohrabacher has it right: Absent a major change in U.S. human spaceflight policy, the Commercial Crew Development program represents the nation’s best near-term bet for fielding an astronaut-launching capability.

This is not to say that NASA should abandon the pursuit of a heavy-lift capability; whatever Congress’ primary motivation for directing NASA to build SLS — it represents thousands of jobs in the states of its most ardent supporters — the program does address the White House’s lack of a credible strategy for future human space exploration beyond low Earth orbit.

But the international space station, built at an estimated cost of some $100 billion, exists today. Capitalizing on that investment requires full-sized crews for maximum scientific utilization; protecting it requires that operations and maintenance personnel be onboard at all times. If these are priorities for NASA — and they should be — fully funding the president’s $850 million request for the Commercial Crew Development program is the most logical response to the recent failure.