'Trampolines' to space? Where Ukraine crisis leaves a Russia-dependent US.

US-led sanctions against top Russian officials over Moscow’s annexation of Crimea and its efforts to undermine the government of Ukraine have been heightening concerns over American dependence on the Russian space program.

The critical Russian hardware ranges from the space taxis that deliver crews to the International Space Station to powerful engines used in rockets that launch sensitive national-security satellites.

The latest discomforting reminder came Tuesday, when Russian Deputy Prime Minister Dimitry Rogozin, who oversees Russia's defense and space industries, took to Twitter to offer a thinly veiled threat: “After analyzing the sanctions against our space industry, I suggest to the USA to bring their astronauts to the International Space Station using a trampoline.”

By Wednesday morning, in response, a US House Armed Services subcommittee had added money to the Pentagon's fiscal 2015 budget to develop a home-grown replacement for a Russian liquid-fuel motor that is used extensively for launching heavy military and civilian payloads.

The quick move highlights second thoughts the US is having about such a heavy dependence on Russia for flight hardware – if a bit late in the game, space-policy analysts suggest.

Twenty years ago, after the collapse of the Soviet Union, it made sense to many space-policy and national-security specialists to embrace former Soviet technology.

The tighter integration of Russian technology into Western spaceflight plans was seen as a way to keep Russia's rocket scientists from seeking work in North Korea or Iran while supplying the US with cheap, reliable components for some of its rockets, explains James Lewis, director of the strategic technology program at the Center for Strategic and International Studies in Washington.

"What you could be critical of is that we didn't have the foresight to realize that things were going to change," he says.

While crew transportation to and from the International Space Station (ISS) is the highest-profile example of the current US dependence on Russia for access to space, it's not the only activity that is potentially vulnerable to tit-for-tat sanctions involving space hardware, should they arise.

The US also relies on Russian rocket motors for one of two large rockets used to loft hefty military and civilian payloads. And one of two companies currently ferrying cargo to the space station relies heavily on components built in Ukraine for the first stage of the rocket it uses for the resupply missions.

Despite Mr. Rogozin's tweet, it remains unclear whether Russia would withhold space hardware bound for the US or for launching suppies to space-station crew members, says Dr. Lewis. Russia has been sending signals at various levels that it is discussing the possibility. But it doesn't count unless Russian President Vladimir Putin says it, he says.

Among the factors that weigh against such a move: Russia relies on US business for hard currency. Moreover, Russia's involvement in the space station is just as important to Russia as it is to the US, if for no other reason than it is one source of international respect for Russia, respect Mr. Putin reportedly is so desperate to build for his country.

Indeed, space-station activities are exempt from a more general ban on NASA contacts with Russia that the US government recently imposed.

"It is very important to both governments to keep the space station operating," says Marcia Smith, a former aerospace and telecommunications analyst for the Congressional Research Service and now president of Space and Technology Policy Group, a consulting firm based in Arlington, Va.

"It would be extremely difficult for either one of us to do it without the other," she says. But she also cautions that events transpiring on Earth could overshadow interdependence in space.

"It is certainly possible that either government could decide that because of whatever is happening down here on Earth, that cooperation could not continue," she says. "But I do think that they are going to try to keep that going, despite the tensions down here."

And if they don't? In the short term, the US civilian and military payloads lined up for launches are likely to leave Earth as scheduled.

United Launch Alliance (ULA), which recently inked a five-year deal with the Pentagon for 35 rocket cores, uses a Russian-made liquid-fuel motor for the boost stage of its Atlas V rocket, which along with the Delta IV has been a workhorse for launching large military, civilian, and NASA payloads into space. It was an Atlas V, for instance, that sent the Mars rover Curiosity on its way to the red planet.

ULA has a two- to-three-year supply of the motors on hand "to minimize potential supply disruptions," according to ULA spokeswoman Jessica Rye, who adds that the alliance – a partnership between Boeing Corp. and Lockheed Martin Corp. – has developed the capability to produce the motors in the US. In addition, if the Atlas Vs become unavailable, the Delta IVs could pick up the slack. All of the Delta's motors are home grown.

The Pentagon, which is studying options for home-grown motors for the Atlas V and future rockets, has estimated that it would take five years and $1 billion to develop a suitable liquid-fuel motor from scratch.

Orbital Sciences Corp., which along with Space Exploration Technologies Corp. (SpaceX) is providing cargo services to the space station, uses a pair of Russian-designed rocket motors in its Antares rocket. These have been refurbished in the US, and Orbital officials have said that the company has enough motors on hand to complete its cargo obligation to NASA through 2017 and to spare.

However, the first stage of the Antares is largely built in Ukraine. Orbital has "about three of those" on hand, according to Ms. Smith, the Space and Technology Policy Group president. Attempts to reach Orbital Sciences by phone and e-mail to confirm its inventory were unsuccessful, but the company reportedly is looking for Russian suppliers to meet its need in anticipation of bidding on ISS cargo launches beyond 2017.

Meanwhile, SpaceX, with its fully home-grown rockets and rocket motors, is suing the Pentagon for closing it out of any competition for the national-security launches currently slated for ULA through the block purchase of rocket cores. Elon Musk, the company's CEO and chief designer, says the company's Falcon 9 has proven itself and in essence is ready for business.

And later this month, SpaceX is set to unveil a full, flight-hardware version of its Dragon Mark 2, capsule designed to carry humans to and from the space station.

SpaceX is one of three companies receiving NASA funds to develop crew-transport systems. But, Smith adds, the other two companies – Boeing and Sierra Nevada Corp. – rely on the Atlas V. If the Atlas is sidelined for a prolonged period for lack of motors, that could leave SpaceX as NASA's only carrier.

Not one to take Rogozin's trampoline tweet lying down, Mr. Musk responded, "Sounds like this might be a good time to unveil the new Dragon Mk 2 spaceship that @SpaceX has been working on w @NASA. No trampoline needed."