Engines to reach the orbit and - later - other planets

Could be you're right about the helium. I'm not sure.

But I believe helium is readily available on the moon. Now there's a chicken-and-the-egg puzzle. I guess we could use conventional rockets to get us to the moon to start mining the stuff, then start using the helium once we have plenty.

I would ask how everyone feels about mining the moon, but that's surely a conversation belonging elsewhere.

there is He-3 on the moon, and it's 'readily available', but it's hardly common. i don't know what the concentration is for sure, but it's very low. still, very low is infinitely higher than the *none* there is on earth. for truly good He-3 mining, you have to go to the gas giants. i'm not sure, but if you mined enough for a ship to go to saturn, say, from the moon, refuel and fill up its cargo area, and come back, you'd probably make alot of money. despite the fact that jupiter's closer than saturn, the lower gravity and smaller magnetic field would probably make saturn easier, especially if the ship is unmanned.

About those baloons - so use Hydrogen! If they explode, they're way high up - no big deal. The problem is they're stationary, while the satelites whiz by at 17,000 mph - 10 time the speed of a rifle bullet. That's going to be quite a jolt when they pick somebody up!

The basic problem is not one of height (for LEO) - it's speed!

Hydrogen. Hmm. You know, one of my problems is that I have nothing like a photographic memory. I have vague memories of having read something hear or there, but can never seem to remember the important details. Like, I have a vague recollection of reading something about someone either experimenting with or theorizing about the use of hydrogen baloons again. It seems like whatever I read was dealing with the fact that maybe hydrogen could be used safely in certain situations... anyone?

Actually I think that the real problem with using hydrogen isn't the flamability of it but rather it's rather annoying tendency to leak out of almost anything.

As far as velocity goes I'm pretty sure that the airship that JP Aerospace intends to fly from the high altitude station will use some form of ion engine to climb into orbit. The trip will take several weeks to get from the station to orbit I believe. I don't think we'll ever see much in the way of manned flights for such a system but the projected costs are being measured in a few dollars per ton to orbit. The write up I read about that was a bit on the vauge side and threw in a mileage cost as well but the bottom line was that it would be much cheaper than anything flying into orbit today and possibly cheaper than the projected costs for space elevators.

JustMeKevin,

there is an additional new solution at NIAC Homepage documented and I'm reporting it here because it seems to be a possible alternative to the nuclear drive.

The solution uses a battery of lasers to cause thrust. The solution requires propellant and hydrogen is taken in the study to be read at NIAC.

What about laser drive instead of nuclear drive?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Aren't there some great sources of helium out on Uranus or Neptune somewhere?

Welcome to the concept of planetary mining.

As for launch systems, I personally believe that the concept of making a surface-to-orbit elevator system that connects to a globe-encircling orbiting geostationary band is probably the best way to go (think along the lines of a spoked wheel: the hub is the Earth, the wheel is the band, and the spokes are the elevators). Guaranteed to reduce launch costs to almost nothing. However, I seriously doubt that it'll ever be done, as the surface area and construction costs involved are way too high.

Hmmm... Sounds like Halo

Seriously, though, I think space elevators are generations off. But someday....

Close, but not quite (I think). I never read the whole backstory to the game, but if I remember correctly, Halo is actually a Ringworld, done in classic Larry Niven style. A planetary band is similar in concept (a large structure orbiting an object), but the scale is way off. A planetary band is a ring placed at Geostationary altitude and physically connected to the surface. A Ringworld is a ring placed around an otherwise planetless star, with a radius of roughly 93 million miles (for a G1-class star; other radii as appropriate for other star types). The Ringworld, as you can see, is much, much, MUCH bigger.

Okay. It's a little off topic, but I can't resist a reply with these two points:

Halo is a little different from Ringworld.
Halo, while not actually encircling a planet, seems a just a tad larger than the nearby planet. So what you describe would be more like Halo (at least in size) than Ringworld.

I was just being silly, silly

Bradley C. Edwards who worked out the elevator concept for NIAC is estimating the costs up to 15 billion dollars - this amount is acceptable. He is estimating the technology to be available within ten or twelve years and he has worked out the way of construction. The elevator will be ready quickly the way Edwards worked out. Because of this NASA has given him a budget of 500.000 dollar and the congress is about to give him additional 2.5 million dollars.

If Edwards succeeds the elavator will be there soon I suppose.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

I would caution against accepting the Edwards article on face value. I mentioned this to a material scientist working on nanotech on another board and he said that Edwards is over optimistic (BS is his own exact words) and the article is just meant as a funding pitch for his own research.

Now and then we get alot of such article promising breakthroughs that are about to happen.... IF funds are provided. These should be taken with some salt.

See below
I have to call bullshit on this one. This guy is overstating the promise of carbon nanotube cable. While individual nanotubes have the materials properties necessary for an elevator cable, the cable itself needs to be woven from mm (or much smaller) sized nanotubes, each of which is only ~0.001 micron wide. In such a weave, the nanotubes will be held together by epoxy or van der waals forces which are much weaker than the bonds holding the nanotube itself together. This means that any nanotube cable will be much weaker than individual nanotubes, which themselves barely meet the tensile strength requirements of this guy's cable.

I'll be the first one to celebrate if they can make a cable like that, but to say that "The major obstacle is probably just politics or funding..." is utter bullshit at this point.

Sounds like this guy knows what he's talking about. Only time (and money) will tell, I suppose.

Oooh, sounds like an interesting take on the toroidal station....

Back on topic: nanotech's brand-new. For the most part, even the researchers are unsure of their products' capabilities. Although it's doubtful that we're capable of an elevator today, it's pretty likely that we will be well before the end of the century.

That's my take, too. Maybe our grandchildren will get to take the ride.