One intangible that has long been missing from the U.S. human spaceflight program is audacity, a quality that can make the difference between mundane and breathtaking achievements. It’s what led, to cite the most obvious example, a U.S. president to declare, in 1961, that the nation would put a man on the Moon before the decade was out. In doing so, John F. Kennedy handed NASA a mandate to engineer what endures to this day as the crowning achievement of the Space Age.

Space Exploration Technologies Corp. (SpaceX) is nothing if not audacious, a trait drawn directly from its founder, Internet billionaire Elon Musk. The company burst on the scene a decade ago with plans to develop a small rocket, a lofty ambition given the track record of startups in that business. SpaceX took its lumps early, suffering failures in three of five launches of its now-shelved Falcon 1 small rocket, but on May 25, it made history by becoming the first private company to build, launch and dock its own capsule to the international space station. The Dragon capsule even delivered some nonessential cargo to the station; its subsequent atmospheric re-entry, splashdown and recovery less than a week later — no small set of accomplishments — was almost anticlimactic.

The fact that Dragon and its Falcon 9 launcher were developed commercially — albeit with considerable financial assistance and incentive from the government — made the docking an event of global proportions, in contrast to the several space station visits paid each year by government-owned and -operated capsules like Russia’s venerable Progress. On a purely practical level, NASA now has a demonstrated capability at its disposal to resupply the space station; SpaceX can now begin executing on its $1.6 billion NASA contract to deliver cargo to the orbital outpost on a regular basis.

But the mission arguably carried greater significance as a symbolic victory for U.S. President Barack Obama’s embattled plan to outsource astronaut crew transportation to and from low Earth orbit. Supporters of the president’s plan were quick to identify it as such, while some prominent congressional critics tiptoed around that elephant in congratulatory statements issued during and after the mission.

One lawmaker who stood out in refusing to acknowledge SpaceX’s accomplishment was Sen. Richard Shelby (R-Ala.), who clearly views commercial crew as a threat to the heavy-lift Space Launch System (SLS) being developed by NASA’s Marshall Space Flight Center in his home state. As quoted in the Huntsville Times while the mission was in progress, Sen. Shelby said SpaceX spent “hundreds of millions of taxpayer dollars to launch a rocket nearly three years later than planned” and that the commercial spaceflight industry was off to a “dilatory start at best.”

Sen. Shelby’s remark — confirmed by his office — was far less damning to SpaceX than it was an indication that he’s feeling the heat. It’s true that SpaceX was 32 months late in demonstrating its cargo delivery capability, and that NASA’s financial aid to the company increased by more than 40 percent. But to put it in perspective, NASA, for an investment of less than $400 million, now has a viable space station logistics system in place, with a crew taxi service — provided by SpaceX or some other company — now looking plausible in the next few years.

Since Sen. Shelby all but invited the comparison, consider that the SLS — a rocket for which NASA and the White House have yet to identify a firm exploration requirement, never mind the funding needed to carry out such a mission — consumes nearly $2 billion per year and isn’t scheduled to make its first unmanned test flight until 2017. As a means of crew access to the space station — it was justified by lawmakers as a NASA-owned backup to commercial crew taxis — the SLS is akin to keeping an 18-wheeler in the driveway for the occasional family outing.

SpaceX has drawn a chorus of criticism over the years, much of it brought on by Mr. Musk’s brash style: He has sounded almost dismissive at times about the challenges inherent in rocketry — the Falcon 1 failures attest to the difficulty — and has a tendency to foster unrealistic expectations. There also are legitimate concerns that SpaceX is taking on too much too soon, about its ability to fly out its existing manifest on the schedule it has promised, and about its long-term financial sustainability. Audacity has its pitfalls. But one can also see an orchestrated, Washington-style campaign to discredit a company that has become the poster child for President Obama’s controversial human spaceflight policy and a threat to the entrenched contractor establishment. This was to be expected.

Even Mr. Musk’s most ardent detractors, though, would be hard pressed to question his commitment to spaceflight or SpaceX’s technical chops: The company’s track record with Falcon 9, which has logged three successes in three flights, and Dragon, which is two for two, speaks with far more authority than any commentary. SpaceX also has made it more difficult to challenge, before the fact, the viability of NASA’s crew transportation outsourcing strategy. Flying cargo and flying human beings are two different things, but the evidence is mounting that NASA is correct in saying there are multiple credible contenders for the job, even if questions persist about the affordability of keeping more than one in the game.

Now more than ever, Congress must take this into consideration in deciding how best to apportion taxpayer funds between competing yet completely different human spaceflight programs: commercial crew, which is focused on near-term access to the space station; and SLS and the Orion crew capsule, which would support deep space missions further out in the future. With SpaceX’s latest flight demonstration, in no small part a product of Mr. Musk’s audacity, the argument has tilted in favor of investing more in the president’s plan.