Who said to use Earth? Build a manufacturing concern in space, use it to build colonies with. The whole point is bootstrapping ourselves off this planet, anyhow.
Sending missions into space is pretty cheap. The expensive part is protecting these fragile bags of tissue and water that constitute our bodies.
And that fact is working its way down the ladder, so to speak. Look at what drone aircraft have been doing in the U.S.’ current military adventures. In 20 years, will the military have any human pilots of fighter or reconnaissance jets? I doubt it: drones will be able to do all those functions much more cheaply than human-piloted aircraft, and while doing maneuvers that would cause a human pilot to black out.
Absent an emerging need to do something that can only be done in space that only humans are capable of doing, space travel will be an increasingly obvious white elephant.
See post #119.
Second only to cheap payload to orbit, what would really help manned spaceflight is if there was some practical way to use electricity to convert carbon dioxide back onto carbon and oxygen. Being able to substitute solar energy for what’s now a required expendable would make longer and further away missions much easier.
Have just written a long post and its disappeared into cyber space,I am well displeasedI can tell you.
If nothing else send exploratory probes throughout the solar system the size of tanks, not the size of toasters. Orbit everything and land on it, not just whizzz on by with a tiny camera snapping shots for a very short period of time.
Even IFF manned space flight never “takes off” (heh), the ability to do much much more for the same price, about the same for much less, or something inbetween is a win win.
Look up what a rocket’s mass is fully loaded. Look at what it is empty.
Even if the ONLY thing you do is manage to mine an asteroid or comet for fuel, the ratio of those two numbers is about how much cheaper or more effective you’ve made your probe program.
If you can or eventually do manage some “simple” manufacturing like for a few of the more massive rocket parts like the tanks, radio dishes, bigger bolts and brackets and ??? you’ve increased the effectiveness even more. Thats a good bit down the line though IMO.
And yes I’ve realized the “space is expensive because we dont do it enough and we dont do it enough because its expensive” conundrum for decades now. Not that it will or perhaps ever be “cheap” and when push comes to shove the vast majority of it isnt neccessary, but most things humans do fall in one category or another or sometimes both.
Its bad, but its not THAT bad.
The required delta V for getting into orbit is much more than the delta V to drop you out of orbit.
On the way down, the atmosphere does virtually all the work.
Look at the space shuttle. MASSIVE tank and boosters to get it into orbit. How does it get back down? Uses some internal tanks that probably take less than 10 percent of its total mass / volume.
Oh, in the short run. I dunno, find an asteroid full of gold, get paid not to deorbit it and completely screw the economy? Nanotech construction in zero G? Solar power satellites, beamed to Arizona desert? (that last one would literally solve all power problems on earth, for pretty much forever.)
Can’t that already be done through simple electrolysis? (I know water can be broken down into pure oxygen and hydrogen that way, I’ve seen it done.)
Still, it is a lot of trouble to get something from orbit to Earth’s surface, if you want it to land substantially intact and not burned up from air resistance. And, for industrial purposes, you would also want it to land someplace completely predictable and readily accessible to motor vehicles, so water-splashdowns are right out.
Double Baloney in my opinion.
On both parts of your post.
I already covered the first part with my shuttle example, even though using the shuttle to bring stuff back into the atmosphere is basically as retarded as require passenger airplanes to land on railroad tracks. There are much simpler and cheaper ways to do it.
On your second part. I’ve got a payload (probably something like gold, platinum, xyz) worth 10s to 100s of millions. And it has to land in my parking lot on a winged vehicle to be worth the trouble?
Its not like we are trying to land Fabrege’ Eggs on peoples front door steps.
No, but it has to land very differently from, say, a meteor – you don’t want fragments spraying out all over the place – and it has to land somewhere a truck can reach it for pickup. And if the payload is space-manufactured goods rather than raw minerals, it needs to set down very, very gently.
What, you got Gilligan recovering a 100 million dollar payload?
I could wrap a bowling ball sized meteor in a couple hundred dollars worth of ceramic fiber cloth and it would land intact.
And I NEVER EVER SAID space manufactured stuff was a good idea for returning to earth’s surface. I even said fancy manufactured stuff wouldnt be practical for use IN ORBIT/SPACE in the near future.
The only thing I’ve said here that might be worth returning to earth’s surface (besides humans desiring to live, small samples, and data) near term ( and even THAT had caveats) were really rare materials like gold (which arent fragile in the least BTW).
I hate to be a naysayer because I’m about as big an advocate for space exploration as you’re likely to find, but I have to be honest and say that the commercial applications for space travel at this time are pretty limited once you get out of low-earth orbit.
Solar Power Satellites seem to me to be a boondoggle. The advantage of SPS is that you get 24 hour sunlight, and that you are outside the atmosphere so the energy of the sun isn’t attenuated. That’s all a big plus. However, the fact is that there is plenty of light energy hitting the earth, and there are already engineering solutions for dealing with intermittent power (molten salt storage is one).
The thing holding back solar power is simply cost. Price is everything. So let’s say your SPS satellite can beam power 24 hrs a day, and can collect twice as much energy. You have to beam it back to earth, which will cause you to lose a significant part of that power. In addition, you once again add atmospheric instability into the mix - cloudy, rainy days will kill your power output.
But the big cost is in launching such a thing. ‘Best case’ estimates I’ve seen for the weight of an SPS satellite is about 1 kg per kilowatt. A 4 GW solar power satellite would weigh 4,000 metric tons. If the Ares V rocket is ever built, it will be the largest rocket ever made - and it will be able to lift 188 tons into LEO. So we’re talking about 20-30 Ares V launches for ONE solar power satellite.
I haven’t seen launch cost estimates for the Ares V, but the space shuttle costs about $10,000/kg for payload. The cheapest lifters around are about $3,000/kg. Let’s be amazingly generous and say that Ares V could lift payload into orbit for $1,000/kg. That’s a launch cost of 8 billion dollars. For one power station. Also, this is assuming LEO, which isn’t really feasible unless you can put up a whole constellation of the things. If you want to put one in geosynch orbit, the launch cost goes up dramatically.
Then there’s the cost of maintenance - this thing will be presenting huge panels to the solar wind, so I imagine it would need some kind of regular thrusters to maintain orbit. It will probably need servicing flights. There would be a HUGE receiving antenna and power conversion station on the ground which would have to be maintained and staffed. And the thing is going to be bombarded with micrometeorites and be exposed to radiation, and therefore will have a finite lifespan.
Forget it. The benefit you get from putting solar power in space is overshadowd by the additional costs of putting it there, and not just by a bit. There’s no way it would ever be cost effective unless there is an orders-of-magnitude shift in the cost of space launch, and maybe not even then.
So what other commercial opportunities are there? Sorry, asteroid mining is a no-go. We’re not short of metals. There’s no way you’re going to be able to recoup the costs of an industrial operation to mine metals from asteroids. There are plenty of mineral deposits we could go after on Earth to get the same materials, which we don’t bother with now because it’s too expensive. But going to the asteroids would be far more expensive yet.
One day, all of this stuff may be useful. If we ever live in space in a big way, we’ll have to mine the asteroids for material. Perhaps one day we’ll have mass drivers on the moon powered by moon-based solar power systems. But today, these are little more than pipe dreams. There’s no path to profitability on any time scale a corporation would be willing to work with. And they WILL plan long-term: If they could show a profit in 20-30 years, they’d take it on. Companies have invested in longer-term projects than that before.
So what’s left? Tourism, exploration, hobbies, and the like. And there is some cause for hope here. Bigelow Aerospace is working on large inflatable habitats that could be turned into ‘space hotels’ for rich tourists. Virgin Galactic has run the numbers and has decided there are enough wealthy people to justify trying to build a market for suborbital flights.
I remember when the Pathfinder landed on Mars, NASA’s web site was getting 40 million hits a day - in 1997, when the internet was much, much smaller. That entire mission cost about 100 million dollars, and could have been self-financing if NASA could have charged even 10 cents per hit.
I saw a proposal once for a commercial rocket launch to the moon, which would deploy dozens or hundreds of tiny rovers the size of R/C cars or maybe a little bigger. The idea was that they would sell ‘rover time’ to schools, individuals, movie makers, etc. For $50, you could get maybe ten minutes of driving a rover around yourself on the moon. Other monetization options included naming the rovers, selling imagery, model kits of the rovers, classroom study guides, T-shirts, you name it. You could also fund the project with donations from wealthy people, sell advertising on the web site, along with other creative ways to raise money.
There maybe an ‘out of the box’ type of idea like this just waiting to be discovered. There is a lot of pent-up demand for space flight and space information out there. We just have to figure out how to monetize it.
And of course, there already is a commercial space launch industry, and it makes money launching satellites into LEO. It’s a growing business.
The other hope for space is the wealthy billionaire crowd. These are actually the guys that are driving a lot of space development right now. John Carmack (Doom creator), Elon Musk (Paypal), Paul Allen, Richard Branson… These guys are pouring billions of their own money into private space development, in part simply because they have the money, they’re space fanatics, and that’s what they want to do.
If you wanna keep 10 folks alive on the ISS, assuming 10,000’s a pound for LEO, and about 25 pounds of water/oxygen a day to keep em alive, thats nearly a billion dollars a year, every year.
Could you get that from an asteroid/comet cheaper? Not at first probably but eventually maybe.
Note, energy wise there are literally about a THOUSAND asteroids that are easier to get to than the moon. And thats to get TO the moon to orbit it, not land on it, which adds yet ANOTHER factor of six or so to the energy/mass cost. Landing on an asteriod is in the noise in comparision.
Cite?
http://echo.jpl.nasa.gov/~lance/delta_v/delta_v.rendezvous.html
Damn, thats better than sex 
That could complicate First Contact . . . “This ‘Budweiser’ legend on your robot probe we encountered, has it some religious significance? In, perhaps, the same pantheon or belief-system as ‘NASCAR Nation’?”
Sweet Jesus, please don’t let em find the ads for Hebrew Nation hotdogs. I don’t wanna explain that one for sure 
Jews, Christians, Jesus, ham, and hotdogs to top it all off are just TOO much to explain !
If we’d given up on manned missions after John Glenn, and switched to just sending probes and telescopes, we would know a lot more about the universe and earth.