During the 2008 presidential campaign, Barack Obama promised to "expedite the development" of the successor to the space shuttle, which ended its final mission on July 21, 2011.

First, some background on the shuttle, which first orbited the Earth in 1981. In 2004, the Bush administration decided to wind down the shuttle program so that the funding could be redirected to a program known as Constellation that would return humans to the moon by 2020 and eventually send them to Mars. That program included building a spacecraft and launch vehicle that could not only send astronauts to the moon but also take them to and from the International Space Station. Obama shelved the Constellation program in 2010, however, and instead proposed relying on private-sector companies to fill the shuttle's role in ferrying cargo and crew to the space station.

With the end of the shuttle program, the United States is now dependent on Russian Soyuz vehicles to carry astronauts to the International Space Station. This is the first time since a six-year gap between 1975 and 1981 that the U.S. has not been able to send astronauts into space on its own. That will remain the case until private companies step in.

One major achievement came in May 2012, when SpaceX's Dragon capsule completed a cargo test mission to the International Space Station, berthing with the station and then returning safely to earth, splashing down with a return load of cargo in the Pacific Ocean. That version of the Dragon spacecraft cannot carry people, but SpaceX plans to build a version that can. SpaceX founder and CEO Elon Musk told reporters earlier this year that human missions on Dragon might be feasible as soon as 2015.

Several other companies beyond SpaceX are competing for a chance to ferry astronauts into space. Under the Commercial Crew Integrated Capability program (CCiCap), NASA will soon choose up to three of these companies to proceed to the next stage of the competition. Two companies would receive full funding and one would get partial funding.

Regardless of the companies' projections, budgetary restraints have forced NASA to push back the expected shift to private-sector human transport from 2015 to 2017. Congress gave NASA $406 million for commercial spaceflght in fiscal year 2012, far less than the $850 million requested by the president. Further shortfalls below what NASA needs to accelerate the transition are expected as deficit reduction remains a top concern.

Any delay beyond 2017 would push up against the current deadline for the end of the International Space Station. Operations on the station are currently scheduled to phase out in 2020, although if the collaborating nations agree, the station could have its life extended beyond that.

The Obama administration has pushed forward with the commercial cargo portion of space shuttle replacement, even adding an additional $350 million. But while the human-flight aspect of shuttle replacement is proceeding with the private-sector companies, the timeline for human flight has slipped under the Obama administration. Under the Bush administration, the target date for U.S. astronauts to fly into space on U.S. rockets and spacecraft was 2014. That is now 2015 at the earliest or, more likely, 2017. The administration has achieved some success in expediting cargo transport but has presided over a delay in human transport. So we rate this promise a Compromise.

A preliminary report from a blue-ribbon space policy panel on Sept. 8, 2009, nudged forward several promises made by Barack Obama during the presidential campaign. One of those was to "expedite" a replacement for the space shuttle.

First, some background on the shuttle. The Bush administration in 2004 decided to wind down the program so that funding allocated to the shuttle could be redirected to building its successor. The shuttle, which first orbited the Earth in 1981, is now slated for retirement in 2010 (though that could slip until 2011). Its successor, known as Constellation, has been behind schedule. In 2005, officials had hoped the successor system would be online by 2012, two years after the shuttle's planned end, but the date has slipped, and now experts are eyeing 2017. That means a gap of perhaps seven years between the end of the shuttle and the launch of the next system.

During that time, the United States plans to contract with Russia to carry astronauts to the International Space Station. But to minimize that gap, space officials have been trying to determine whether it's possible to speed up development of the space shuttle's successor — either the contractor-built Ares I rocket and the Orion capsule, or by having entrepreneurial private space companies modify cargo vehicles currently planned for use in human space flight.

The question of reducing this gap — the longest in the history of U.S. space flight — was addressed at some length in the 12-page summary of findings released on Sept. 8, 2009, by the U.S. Human Space Flight Plans Committee. This panel is more commonly known as the Augustine Committee, after its chairman, Norman Augustine, the former CEO of Lockheed Martin.

While the panel said that the Constellation design would fit the human space program's needs, it expressed concerns about Orion's recurring costs. "The capsule is considerably larger and more massive than previous capsules ... and there is some indication that a smaller and lighter four-person Orion could reduce operational costs," the committee wrote. "However, a redesign of this magnitude would likely result in over a year of additional development time, and a significant increase in cost, so such a redesign should be considered carefully before being implemented."

Meanwhile, the panel said it was open to commercial alternatives.

"The United States needs a way to launch astronauts to low-Earth orbit, but it does not necessarily have to be provided by the government," the summary said. "As we move from the complex, reusable shuttle back to a simpler, smaller capsule, it is an appropriate time to consider turning this transport service over to the commercial sector. This approach is not without technical and programmatic risks, but it creates the possibility of lower operating costs for the system and potentially accelerates the availability of U.S. access to low-Earth orbit by about a year, to 2016. The committee suggests establishing a new competition for this service, in which both large and small companies could participate."

Officially, the Augustine committee's findings are only options to help guide the Obama administration — and as of this writing, the full report is not even out. In addition, Congress must approve of any major change, and that's far from a certainty. But the panel's deliberations are being taken seriously at NASA, the White House, among lawmakers and within the larger space community, so when it urges a quicker successor to the shuttle and suggests that commercializing human space transport could be a good idea, key players are listening. For this reason, we rate this promise as In the Works.