When humans are added to the passenger list instead of robots, the expenditures rise exponentially. Scientists need to make sure they leave, arrive, and return safely. And if you're talking settlements on the moon or Mars, you're adding the expense of generating power, shipping gear, and designing spacesuits and tools that can withstand unfathomably harsh environments – moon dust alone poses a constant threat since it is essentially bits of broken glass. These items don't just come off the shelf at Home Depot. One longtime estimate for a simple lunar outpost has been pegged at $33 billion. Others estimate it at $100 billion over 10 years.
The Augustine committee was predictably sober about what the US can do about sending humans into space with the money currently allotted. Yes, it said, the US can go back to the moon, as President Obama has indicated might be good. It could probably build a rocket and a lunar capsule. But without additional funding – at least $3 billion by mid-decade (NASA's current budget is $17.8 billion) – the agency would have to stretch out the program. Ares, the next-generation rocket, wouldn't be ready until just before the agency turned out the lights on the space station. There would be no money to fabricate the things needed to live on the lunar surface. Astronauts would be suited up with no place to go.
Alternatively, the commission said, the US could forgo landing on the moon and instead begin a series of launches between 2020 and 2030 to send astronauts to orbit the moon, Mars, or an asteroid. Notably, it also said that the US could expand its footprint in the heavens by leading a "bold new international effort in the human exploration of space." In other worlds, cooperation – the Starfleet Command-like approach.