The space shuttle was never meant to take us to other planets. "Shuttle" implies something akin to a ferry, so it would take people from earth to orbiting structures and back again. The problem is that aside from putting Hubble into space and maintaining it, helping out Mir, and installing the ISS, the other structures in space never materialized.
Koray's concern of the cost of gasoline is not unwarranted. While the shuttle doesn't consume gasoline in its ascent into orbit, the external tank, solid rocket boosters, and shuttle itself if it lands anywhere other than Canaveral all require gasoline to get to the launch site. Not to mention the tremendous cost of the raw materials required to build the external tanks, which are not reusable unlike the SRB's since it falls off at such a height that it burns up.
It is unfortunate that so many jobs have been lost with the termination of the space shuttle program. But as cigarettes get more and more expensive, and the restrictions and fines to use them in public places increase, it seems that the government seeks to put the people in that industry out of work too, but nobody cries over that spilled milk. Curious.
What problems facing humanity will building orbital colonies solve? Overcrowding? The places with the highest concentrations of human life tend to be among the poor people in cities, especially in third world countries. Are these people good candidates to throw up into space? There are plenty of vast untamed wildernesses on this planet for the six billion of us to spread out and all have some room. The problem is that so many people are crammed into tiny countries with no opportunity to move into the empty places, and the people with room to spare don't want everyone else's refugees.
Food shortages? There is no food to be had in space, where every drop of water or seed must be placed there by rocket from the ground.
Jobs? Unless people will make their living collecting the last 60 years' worth of space debris from orbit, there are no raw materials in orbit to support an economy, other than space tourism.
Mars is a logical place to send people, if only to mine whatever raw materials might be there, study the water and rocks there, and to build larger spacecraft for deeper space missions in the low gravity and better access to the outer planets. The real action in our solar system -- aside from Earth -- is in the asteroid belt for its mineral wealth, and in the Jovian and Saturnian satellites that may support life. There's no reason to go inward, to Mercury or Venus.
But I'm also a big fan of not putting any concerted effort into space travel until we either find indisputable proof of extraterrestrial civilizations, fix this planet, or find a way to put people into stasis for the months and years it'll take to get anywhere.
Riker: Look at that.
Cochrane: What, you don't have a moon in the 24th century?
Riker: Sure we do, it just looks a lot different. There are 50 million people living on the moon in my time. You can see Tyco City, New Berlin, even Lake Armstrong on a day like this.
That's funny. I remember a particular DS9 episode where the Defiant returned to Earth, and the moon looked exactly like the moon of today: barren. The only time I recall seeing development on the moon in Star Trek was in the two next to last episodes of Enterprise, where Peter Weller was the bad guy. And even then, you didn't see a built up moon from a distance.
I suggest a full frontal assault with automated laser monkeys, scalpel mines, and acid.