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4185 clicks; posted to Geek » on 23 Dec 2012 at 6:13 PM (4 years ago)   |   Favorite    |   share:    more»

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hubiestubert: I am shocked that this idea might not be exactly environmentally friendly...

Though, in fairness, it was good enough for Larry Niven and Jerry Pournelle...

Not to mention Jules Verne Durand.

taurusowner: Wow. 47 posts in and no one suggest a space elevator yet? I'm surprised.

\\What a terrible unrealistic idea

I agree for an Earth based elevator. It might be possible on the Moon or Mars with their lower gravity and atmospheric stress. With some materials advances of course...

Argonreality: I'd personally like to see what kind of logistics would be required for a rather low-tech solution to escaping Earth's gravity well: balloons. Ones filled with hydrogen to be specific, and engineered to use only that gas instead of being made for something else and using hydrogen as a last minute substitute. Anyone know some rough numbers?

For a rigid balloon:

Buoyancy = density of air - density of buoyant gas
At, say, 30,000 ft, the density of air is .35 kg/m^3.
The projected mass of the Orion interplanetary craft is about 2,000,000 kg.
For fun, let's say you have a balloon filled with vacuum.

So, 2,000,000 / (0.35) = 5.7 x 10^6 cubic meters of hydrogen, or a spherical balloon with a radius of over 110m. That's just for neutral buoyancy at a low altitude. At 100,000 feet, which is around where Kittinger jumped from, air density is around .01 kg.m^2. Now you're looking at a balloon with a radius of over 360m, made of a material that is light enough to add negligible mass, but strong enough to hold itself up, plus a 2 million kg load.

You can reach much higher altitude with an elastic balloon because the volume of the balloon will expand as the air pressure decreases, but the problem of strength is compounded by the necessity for elasticity. At 100,000ft, which is less than 1/2 the distance to "space", you're looking at an expansion ratio of about 100:1.

Argonreality:

By the way, all of that is ignoring the problem of considerable factors like wind, air turbulence, etc.

Argonreality: I'd personally like to see what kind of logistics would be required for a rather low-tech solution to escaping Earth's gravity well: balloons. Ones filled with hydrogen to be specific, and engineered to use only that gas instead of being made for something else and using hydrogen as a last minute substitute. Anyone know some rough numbers?

Excellent question!

http://en.wikipedia.org/wiki/Flight_altitude_record#Hot_air_balloons
"On November 26, 2005, Vijaypat Singhania set the world altitude record for highest hot air balloon flight, reaching 21,290 m (69,850 ft). He took off from downtown Bombay, India and landed 240 km (150 mi) south in Panchale. The previous record of 19,811 m (64,997 ft) had been set by Per Lindstrand on June 6, 1988 in Plano, Texas."

http://en.wikipedia.org/wiki/Low_Earth_orbit
"Low Earth orbit (LEO) is generally defined as an orbit below an altitude of approximately 2,000 kilometers (1,200 mi). Given the rapid orbital decay of objects below approximately 200 kilometers (120 mi), the commonly accepted definition for LEO is between 160 kilometers (99 mi) and 2,000 kilometers (1,200 mi) above the Earth's surface."

So a balloon can get you up to about 20km, but Low Earth Orbit requires at a minimum 160km -- and that's only vertical distance. If you have no lateral velocity, you'll just plunge back down toward the Earth.

So yes, a balloon could get you really far off the ground, but you still need a lot more "up" to escape Earth's gravity well. Sadly, Earth's atmosphere runs out too quickly!

rocky_howard: simplicimus: Most of these seem to require chemical rockets to escape the gravity well. As for using nukes near earth, some people might object.

Define "near".

If you detonate a bomb, the effects are barely felt a hundred kilometers down the road.

Even if you detonate a bomb midway to the Moon, that's 150,000 kilometers away, it's not going to affects us. Not to mention the bombs will likely start going off after they're past the Moon orbit, not right after they get out of the atmosphere.

Bombs detonated after that distance aren't even probably going to be seen from here.

Of course, the simpletons will think we'll nuke the entire sky and it'll be Armageddon. farking religion putting ideas in people's head.

The people dealing with fallout from the Fukushima accident might not agree that (1) the wise engineers will take care of everything and there will be no problems with the nukes during the flight, or (2) concerns about nukes are ideas put there by "farking religion." Fool me once ...

Charles_Nelson_Reilly: The people dealing with fallout from the Fukushima accident might not agree that (1) the wise engineers will take care of everything and there will be no problems with the nukes during the flight, or (2) concerns about nukes are ideas put there by "farking religion." Fool me once ...

Yeah because what? 1 nuclear related tragedy in more than 50 years of nuclear power somehow makes the energy insecure. Get real...

And no, a) Chernoby doesn't count because the Soviets farked up and didn't follow procedures then tried to save face. b) 3 Mile Island was proof of the system actually working, not the opposite.

And again, a nuke going off at more than 350,000 kilometers from Earth is not going to affect us in the slightest. There's no "wind pushing the radiation to California" scenario.

You can take the largest nuke we have and it means jacksquat.

beam-based propulsion. All your energy stays on the ground, and the vehicle only has to carry reaction mass for fuel. Not only could it get you to space with less than a thousands bucks of electricity, but it could also be used for interstellar travel.

Space fountan: uses transfer of momentum to build a space-elevator type tower, except w/o the need for exotic materials, and does not need to be build on the equator.

Launch loop: similar to a space fountain, but sideways. Uses transfer of momentum to place a loop of track that "hovers" at near orbit height, and launches payload even higher.

I like the beam based propulsion. Need quiet an array of gyroklystrons but doable. I say gyroklystrons because you'd do well to be up at mm wave frequencies to keep your beam width down. As for the others, too much of a liability if the power went out.

On He3 it doesn't burn as well d-t assuming Maxwellian velocity distributions, so not much reason to worry about it until you either
A. Get d-t to reliably burn
Or
B. Get a stable plasma with a fat tail v dist.

Still, chopping off roughly 16-17% of the LEO travel would let you save on whatever fuel you're using. Worth looking at in more detail imo.

If the Higgs field is responsible for imparting mass, we may someday discover a way to manipulate that field and use it as a force to propel spaceships akin to tacking into the wind. Imagine a spaceship that has it's mass reduced to near zero. It wouldn't take much energy to accelerate it to light speed, or faster if the Higgs field is responsible for the light speed limit.

foxtail: One more thing to concider.
Even if they could solve the problem with FTL travel and radiation, how are they going to know what is in their path a few seconds ahead of them?
One chunk of rock floating in their path the size of a baseball....
Or the size of an elephant.....

This is why I tell all my friends, "Fark warp drives, the real money is going to be in wormholes and folding space technology."

/warp drives are Edison
//getting there without moving will be safer...that's Tesla

Why, Photoatomics is the answer! Photoatomics and SQuID (Solid-state Quartz Ion Drive) motors. Solid-state Photoatomic quartz engine cores within a long reactor vessel lined with photoelectric cells pouring out massive amounts of ultraviolet light when the elements of the core are brought close enough together for the embedded nuclear material to begin reacting. Their energy is used to excite and accelerate hydrogen in helical swirls up and down the interior until finally the inside of the engine is brighter than the sun. The light is used for electrical power generation, as a laser source for all the fun things you can do with lasers, and the liquid hydrogen works as both a coolant and propellant, turning directly into plasma and shooting at incredible speed toward ionized grids down-bore. The hydrogen isn't entirely wasted, though, as it is partially harvested for re-use after leaving the motor when it passes through trailing collectors on long, long filaments behind the ship. Without an oxidizer, it is much more efficient than chemical rockets, without the potential of leakage it is much safer than old-school nuclear rockets, it can provide enough laser power to be an on-board beam motor within an atmosphere, it can turn lots of different stuff into plasma if necessary so it's multi-fuel capable, and of course hydrogen can be obtained from lots of sources on planets or in space so it's ostensibly able to run indefinitely. It's an all-in-one solution! Too bad it's pretty much just bullshiat that came out of stress-related insomnia followed by too much coffee.

Oh, but a modified version of this in nano-scale miniature, using magnetic fields to create counter-rotating rings of highly ionized plasma and some jiggery-pokery involving coherent reflection and the venturi effect could make a real Arc Reactor/Repulsor. Picture largely flat jet engines using lasers to make plasma out of air. Picture flying cars where the wheels fold down and become thrusters. Also picture giant super-robots with Archimedes-style laser arrays on their chests, rocket punches that don't require an entire day to make ready for re-use and more power than they know what to do with.

And don't even get me started on the steampunk version of it, the Brightfield Radiumite Energomatic Redoubler™.

Z-clipped: Argonreality:

By the way, all of that is ignoring the problem of considerable factors like wind, air turbulence, etc.

Actually the biggest problem is the velocity component. You can do a simple energy calculation and see that getting to orbital altitude takes only a fraction of the energy as getting to orbital velocity. That's the main reason things like spaceship1 are so much smaller than satteliete launching rockets. They are neat ways to get to space, but nothing like what is takes to stay in space.

Mutt Farkinov: foxtail: One more thing to concider.
Even if they could solve the problem with FTL travel and radiation, how are they going to know what is in their path a few seconds ahead of them?
One chunk of rock floating in their path the size of a baseball....
Or the size of an elephant.....

This is why I tell all my friends, "Fark warp drives, the real money is going to be in wormholes and folding space technology."

/warp drives are Edison
//getting there without moving will be safer...that's Tesla

The solution to all this is to make your warp metric collapse as you form it until the outer cross-section is just a bit larger than the Planck limit (the interior of the metric is unaffected) -- then you go through all the rocks/particles/planets with minimal disruption and the leading edge energy release is hardly noticeable when you re-expand the warp on arrival. It also cuts down the total energy required by orders of magnitude.

Bigger on the inside than the outside is the way to go.

carterjw: Z-clipped: Argonreality:

By the way, all of that is ignoring the problem of considerable factors like wind, air turbulence, etc.

Actually the biggest problem is the velocity component. You can do a simple energy calculation and see that getting to orbital altitude takes only a fraction of the energy as getting to orbital velocity. That's the main reason things like spaceship1 are so much smaller than satteliete launching rockets. They are neat ways to get to space, but nothing like what is takes to stay in space.

The point I was making is that balloons aren't a feasible way to lift large masses to high altitudes. No balloon can ever reach "orbital altitude" because the fluid that lifts the balloon is what defines the lower boundary of sustainable orbit.

"Orbital velocity" is also not a fixed speed. It's dependent upon the distance between the relevant bodies. The higher the altitude, the lower the speed necessary to maintain freefall.

Ultimately, escape velocity is escape velocity, no matter which direction you're pointing.

There's nothing wrong with chemical rockets for getting around inside the Solar System.

The limiting factor is acceleration force on the payload.

A rocket only pulling three G's to keep humans comfortable on the way to orbit burns a huge amount of fuel compared with one putting up the same mass in hardware at ten.

Quantum Apostrophe: All you need is a new Periodic Table of the Elements, some new forces and particles, some new magical materials, sure, why not. Other than that, you realize that we are collectively on our last gasp of easy-to-get hydrocarbon fuels? What energy source, pray tell, a real, practical one that can actually be built, will power these magical carpets to the stars?
And once you're in space, is it any less empty and deadly for all that?
Anyways, Happy Mud Ball Holidays right here on Earth, you'll never leave this place might as well enjoy it!

::tips hat::

warp drive

For some reason I read that as fart drive. Why not, if the people on board produce enough gas, and can keep alive and going for long enough to make it? Bean powered space ships, maybe?

/In space, no one can hear you fart
//or smell it

turbocucumber: warp drive

For some reason I read that as fart drive. Why not, if the people on board produce enough gas, and can keep alive and going for long enough to make it? Bean powered space ships, maybe?

/In space, no one can hear you fart
//or smell it

Finally a use for old farts

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