The idea of a citizen's space program, as opposed to a government one, appeals to me. It is of course ridiculous, but one can do worse than play.
Rocketry-based space travel seems to need the economic scale of a government, a (fairly large) corporation or some collaboration between such. So that pretty much takes rockets out of this space program. But hey, once clear of the atmosphere one can do solar sailing, which sounds like it shouldn't require such huge bugetry. On its own, that would still involve buying passage on some large organisation's rocketry; which would expand the budget somewhat. Still, it'd be a fun half-way house to explore …
Alternatively, one can try to find some other way out of the Earth's gravity well. We need to get to the point where a solar sail is enough to take us the rest of the way; rocketry would put the sailing vessel into a low Earth orbit from which, by careful sailing, one should be able to escape; replacing the rockets would involve getting clear of the atmosphere and getting up a huge amount of sideways momentum (so as to stay in orbit, rather than falling back down again). It's a pretty safe bet that any replacement for rocketry is going to have trouble with both halves of that; though a space elevator would greatly reduce the orbital momentum problem by (somehow) delivering the energy to get all the way clear to geostationary orbit, out where one doesn't need much sideways velocity at all. Somewhere in there, there's a pay-off between brute lifting and building up sideways momentum; and a lower orbit has a lower total energy, making a strong case for low orbit.
As far as getting clear of the atmosphere goes, it begins with the troposphere – the bit at the bottom, with all the weather in it. Getting through the troposphere, into the low stratosphere, is easy: a big slack back of a helium balloon is reasonably affordable and can lift a fair old pay-load. After that, we come to the stratosphere: which is much thinner than the air we're used to – certainly not breathable, indeed thin enough one can see the stars against a black sky even when the sun is in sight. All the same, it'll be too dense for our solar sail, I suspect – at least at the altitutes one can reach by balloon.
Still, an energy source does suggest itself: the stratosphere is stratified, with different horizontal wind-velocities in different strata, so kites in different strata could pull in different horizontal directions, but all upwards, on a central pay-load. This might be ludicrously impractical, but warrants investigation: the idea isn't that much different from the solar sail Clarke has left us so confident will work even in the seemingly hard vacuum between the planets. [More on this.]
Once helium blimps are far enough up the stratosphere to stop rising by buoyancy, the stratosphere's so thin they don't have much air resistance, despite their size, so they can be accelerated gradually up to orbital speed.
The road to space becomes even more important to us now that we are within reach of an end to aging and endless fertility.
Update: mid-summer, 2004 (I think actually the day before the solstice), the first non-government astronaut made it to space and safely home again, aboard SpaceShipOne. Other exciting developments are afoot, as well.
Written by Eddy.