Hell hath no fury like a NASA Administrator scorned. Since the Space Shuttle was retired in July 2011, the U.S. has had to rely on purchasing seats aboard Russia’s Soyuz spacecraft, at significant cost, to get its astronauts to the International Space Station (ISS). And the longer it goes on, the more NASA’s Administrator Charlie Bolden gets pissed off.

The goal was to use the Soyuz as a stopgap to a new generation of privately built American vehicles, but continued funding cuts and subsequent delays have seen the program slip and slip. And yet another cut has meant that NASA has had to stump up another $490 million (£320 million) of taxpayers' money to Russia to keep American astronauts flying to the ISS on the Soyuz through 2017 at least.

In a scathing letter to Congress, Bolden laid bare his disgust at the situation, deriding lawmakers for continuing to stunt one of the key goals of his tenure – the development of private spacecraft for transporting humans to the ISS in low Earth orbit.

“In 2010, I presented to Congress a plan to partner with American industry to return launches to the United States by 2015 if provided the requested level of funding,” he wrote. “Unfortunately, for five years now, the Congress, while incrementally increasing annual funding, has not adequately funded the Commercial Crew Program to return human spaceflight launches to American soil this year, as planned. This has resulted in continued sole reliance on the Russian Soyuz spacecraft as our crew transport vehicle for American and international partner crews to the ISS.”

^{A Soyuz spacecraft launches to the ISS from Kazakhstan. NASA.}

The two spacecraft being funded under the program are SpaceX’s Dragon capsule and Boeing’s imaginatively named CST-100. In September 2014, NASA awarded them $2.6 billion (£1.7 billion) and $4.2 billion (£2.7 billion) respectively to get their manned spacecraft up and running by 2017, but these funding awards relied on continued cash flowing from Congress for the program.

In NASA’s latest budget drawn up by Congress, $350 million (£225 million) was slashed from the Commercial Crew Program, which leaves NASA unable to meet the 2017 target. “If this occurs, the existing fixed-price CCtCap [Commercial Transportation Capability] contracts may need to be renegotiated, likely resulting in further schedule slippage and increased cost,” wrote Bolden.

Separately to this, NASA is developing its own spacecraft – Orion – and an accompanying heavy-lift rocket, the Space Launch System (SLS). While the private spacecraft will be tasked with going to low Earth orbit, NASA is focusing its own efforts on deep space exploration to an asteroid, and ultimately Mars.

But these continued cuts threaten these goals, said Bolden. Research on the ISS in low Earth orbit “is critical to the success of the exploration program,” he wrote. “While I understand that funding is extremely limited, it is critical that all of NASA’s human spaceflight efforts be support.”

^{SpaceX's manned Dragon capsule, illustrated, is one of two private spacecraft that will take astronauts to the ISS. SpaceX.}

For now, NASA will have to continue to rely on Russia to maintain its manned exploration efforts. It’s not known how much the Commercial Crew Program is expected to slip beyond 2017, but Congress could do worse than listen to Bolden’s demands. He does have a point, after all. Why continue to burn money on Russian spacecraft when it could be better spent on companies in the U.S. and feed money back into the American economy?

Of course, space travel is more an international effort now than ever before, and a future mission to Mars will likely involve several nations, not least the U.S. and Russia. But to be a true space-faring species, continued access to space is needed, and at the moment, private companies like SpaceX and Boeing are the best way of achieving that.

“It is my sincere hope that we all agree that the greatest nation on Earth should not be dependent on others to launch humans into space,” Bolden concluded. “I urge Congress to provide the funds requested for our Commercial Crew Program this year, so we can prevent this situation in the future.”