Steam Powered Flying Vehicle?

As far as the "space gun", yes using compressed gas to accellerate the capsule would make a smoother accelleration, but a staged series of explosions is also possible. Especially if, as was said, you line the cannon with explosives, so you have not a distinct series of blasts, but a continuing rolling explosion creating a smooth pressure wave.

To do this properly, evacuate the cannon (create a vacuum in it) with the muzzle sealed off with an airtight door. Otherwise the air building up in front of the capsule slows it down. The door is opened an instant before the capsule hits it.

How much accelleration can a person in top physical condition withstand without severe, long-term damage? About 40G. Evidence here:
http://makeashorterlink.com/?S1FB23CCC

Yes immersion in a liquid helps the body as a whole withstand accelleration better, but that doesn't stop things like the brain being mashed against the inside of the skull (which is what concussion is) and damage to eyeballs, which happened when they hit their test pilot with 46G. A good, individually form-fitted accelleration couch will do about as well as liquid immersion, altho the latter has the advantage of being usable by anyone without making a custom-fitted couch, and would result in a lot less bruising.

How long does the space gun need to be? *Very* long; Verne's Columbiad at a mere 900 feet was a pipsqueak by comparison. According to

http://en.wikipedia.org/wiki/Low_Earth_orbit

...minimum orbital speed is about 8 k/s (kilometers per second), with about 1.5 k/s additional initial velocity needed to compensate for loss due to atmospheric and gravity drag. If we accellerate at 40 G's we get 392 meters/second acceleration, reaching 9500 meters/second in about 24.23 seconds. In that time you'd travel about 9490 meters, or about 5.89 miles, which gives the needed length for the cannon's bore.

But actually this won't get you into orbit. The problem is, that calculation is based on the way rockets travel; mainly vertical to get above most of earth's atmosphere, then turning horizontal to gain speed. Firing a cannon at ground level means you need to fire almost straight sideways, with the result that most of your speed is dissipated via air resistance and is converted to heat; your capsule crashes to earth and your passengers roast. And putting it atop Mt. Everest doesn't help much; airplanes typically fly at 40,000 feet and have quite enuff air to hold them up.

What to do? Well you can fire at the moon, and loop around that to get into the right earth orbit.

I'm not sure what the velocity is for lunar orbital insertion, but it's a bit less than escape velocity, which is 11.2 k/s. Running those numbers again, we reach 12,700 m/s in about 32.4 seconds, requiring a distance of 12,700 meters, or about 7.89 miles. A bit less actually, since you'll lose less velocity from gravity by travelling so quickly, plus you only need to get over the gravitational "hump" into the moon's gravity well, instead of achieving escape velocity. Depending on your story requirements, of course... I'm assuming you don't plan on interplanetary travel?

Anyway, that's quite an engineering project! The most practical way to achieve it would be to bore down into solid rock. Trying to cast a gun that big would be impossible; I'm not sure they could even come up with enuff iron for a gun that big. Railroad tunnels were bored for miles thru solid rock so I don't think it's impossible even in the steam era. They'll have to organize water pumps and elevators in stages, but I can't think of anything completely beyond their technology. You'd need forced draft ventilation to push in fresh air and vent foul air, but that's standard for deep mines.

Note if you have to use the moon to slingshot your space capsules, you can only launch once per lunar cycle... you have 13 launch windows per year.

 

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Anyone ever read Jules Verne?

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Apollo 8 (which looped around the moon) travelled at 10.8 k/s, so as I said lunar orbital insertion velocity isn't much less than earth escape velocity.

In case it wasn't clear, when mentioning Verne's Columbiad I was referring to the space cannon from Jules Verne's novel From the Earth to the Moon, which AFAIK was the first literary appearance of a giant gun used to fire a capsule into space. But Verne's numbers were way off; it has been said that his gun would have killed the passengers without getting the capsule much higher than the surrounding trees.

 

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Sorry, I missed your Verne reference when I read your post. I think he got the idea for the novel from the then relatively new nitrocellulose (smokeless powder). It was more powerfull than black powder but Verne didn't realize you really want to go the other way, a weaker propellent and a longer barrel. I seem to recall hearing about natural gas/air suggested as a propellent.

 

Well it appears I'm wrong about the lack of difficulties with very deep mining. See:
http://www.madsci.org/posts/archives/mar2001/984708217.Es.r.html

This makes it rather more difficult. In addition to pumping in large quantities of cool air, they may have to line the lower part of the bore with metal plating to stabilize things. If I were writing the story I wouldn't let these difficulties stop me-- "Never let the facts stand in the way of a good story!"-- but it certainly would be a very expensive and very difficult engineering project, and in the real world quite possibly impractical for steam-era technology.

Pumping in cold water would be a much more efficient way to cool things, but would make the risk of flooding-- always a danger in mines-- much worse.

 

As a writer you may be interested in a very fine example by R.A. Heinlein, called Rocket Ship Galileo, originally published in 1947.

His "flying machine" was powered by an Atomic Pile. It used molten zinc as the reaction mass, but in later stories by Heinlein and others (notably the Martian Way by I Asimov used water as a reaction mass.

Using water, flashed into steam forcibly propelled out of a rocket nozzle could be classed as "steam power".

Turning to American History, there is another fine theoritecal example, in that in 1951 the US Air Force did an actual study for the building of an Atomic Airplane. A nuclear-powered airplane would have likely been a "steam powered craft" much as nuclear submarines are. The "fire" would come from the nuclear pile onboard.

Finally, I remember reading in Popular Science in the '70's or '80's about an external power-source flying machine. Lasers or masers would focus energy onto a reciever antenna on the vehicle, flashing water into steam for propulsion. The water/steam is reaction mass, just as in the Science Fiction stories, only this craft would have wings and remain atmospheric.

Hope this helps give you some ideas as a writer.

 

I seem to remember that the earliest prototype for the Galileo used mercury as reaction mass. I have no recall of the finalized fuel which took them to the Moon, and am disappointed that it was the more pedestrian zinc.

Of course, any reaction mass would have to be vaporized to make the rocket go. Wouldn't we have an uproar about every satelite launch spewing a Gillian tons of mercury vapor, technically a kind of steam, into the air!

Nuclear rocket engines have been built and tested throughout a 4 or 5 decade span. Google "Kiwi". And also nuclear jet engines.

 

The only reason I recall it was zinc, was that the scientist in charge of the rocket wanted to include some "safety fuel" (meaning extra reaction mass they could use in an emergency). Their silverware and plates were all made of zinc, which could have been fed into the atomic pile. As a kid, I thought this was a pretty cool idea at the time.

Using a metal and vaporizing as a reaction mass is pretty good notion, but you do not get quite the specific impulse of that of water/steam. This is because the "extra" energy required to convert water from liquid to steam is larger (per pound) than that of any metal. It seems it's much "easier" to melt metal than water, if both are at their melting temperatures.

I suppose this is because metal is essentially a matrix of atomic nuclei surrounded by a "sea" of electrons - a loose amalglam if you will. Water, even liquid water, still retains much of it's "crystal structure" in molecular bonding. It is this bonding that must be broken, to convert it to steam.

And, it is often this energy gain/release that is used in steam engines, too. The water vapor (invisible) will often condense into a "cloud" of "steam" we classically see as a mist. This condensing will, of course, release the energy back into the environment.

But, I digress ....

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There is a chance that my reading of that marvelous book as a youngster in the early 50's might have presaged a later edit to assuage us environmentalists; It could be that it was written as mercury in 195X but changed to lesser-evil zinc later on. Of course, it could also be that I have CRS. ( Can't Remember S**t ).


My slyly hinted point was that rockets work good when they expel a gaseous reaction mass, and work not so good if required to expel nongaseous exhaust, so, mercury or zinc, the exhaust had to be a gas, which in one technical sense would be a "steam" of whatever element or compound the reaction mass initially was.

 

Oooh! Oooh! (hand raised *heh*) Good Point!

I do seem to recall a rocket-story about a ship that was propelled by expelling solid iron "sand" by magnetic force. (and now that I proof-read this, any metallic [or conductive] sand would work, as a strong enough magnetic field density would cause minute current-flow in the conductive particles, causing them to develop magnetic properties. Even aluminum would work.)

I also recall stories with ships that expelled large-ish rocks using steam or other vapor to blast them away from the ship.

So, the requirement for gaseous reaction mass is not a complete requirement. It just makes the engineering simpler, not to mention the "fuel" delivery and storage.

...

Then, I remember a story by Robert L Forward, where the space ship was propelled by laser light bouncing off of a silvered "sail". The sail was miles in diameter, and held it's shape by the axial spin of both the sail and the ship: the outward forces would draw the sail into a relatively flat disc. As the energy of the laser was relatively low, for any given cubic centimeter of space, the ship itself was in the "path" of the beam, and harmlessly.

After 1/2 the journey (the laser was HUGE, and in orbit around the sun directly, to avoid any planet shadow) the ship would flip end-for-end. Now, the outer ring of the sail is detached (before the flip, natch), and it's shape was adjusted to become a frensel lens. It would now bounce/focus the laser-from-Earth back to the ship, with it's smaller sail facing the other way. The smaller sail was "out of focus" to the laser, now. The outer ring continued to accelerate away from the ship, towards the voyage's end, but the ship, with it's smaller ring, would be slowed by the "back-bounced" light. At this point, also, the color of the laser was changed from red (or infra-red, I forget) to green, upping it's energy "density". This compensated for the smaller sail the ship now had.

Sorry, I forget the name of Forward's very cool story. Starquake series maybe?

 

UM.... electrons... are pions..

-MT

 

I was having mental tunnel vision, considering only the context of the wonderful Heinlein book when making my rocket exhaust/gas comment. Of course, in an unlimited context, any mass that can be thrown through the tailpipe can make some rocket go.

Even allowing for my CRS, the Gallileo used an atomic pile to HEAT a reaction mass, and that could only work if the reaction mass going out the tailpipe was a gas.

If the pile flashed a portion of the reaction mass to gas which in turn expelled liquid or solid through the tailpipe, the over all reaction efficiency would be too dismal to get to the moon.

 

er, no.

http://en.wikipedia.org/wiki/Pions

 

I don't think "steam" is a synonym for "vapor". There has to be water vapor involved to be steam, at least by the dictionary definition.

And yeah, you can throw anything off the back of your spaceship, including old boots, to get forward velocity. The higher the velocity of the exhaust, the more efficient is the drive. Which is why a nuclear rocket (nuclear heating of the fuel) can be more efficient than normal chemical combustion.

The most efficient propulsion system would be one that boosted exhaust mass to relativistic velocities (near the speed of light). An ion drive achieves this, but an ion drive has extremely limited exhaust mass available-- only the ions coming off the charged plates. When the plates get too eroded, the drive stops. What we need is something that will accellerate particles like an ion drive but will be able to use larger masses. However even with an ion drive there's a problem with energy: How do you generate enuff electricity to power an ion engine? And if you're accellerating much more mass, then your energy requirement is similarly much larger.

Ultimately, barring "magical" technologies such as a "reactionless" drive, the best near-term solution seems to be high-temperature fusion. This would heat exhaust mass to millions of degrees and provide plenty of power doing so. Now if only we could figure out how to create fusion on a large, sustainable, controllable scale...

 

"September 20 1874, Du Temple builds a steam-powered monoplane which achieves a short hop after gaining speed by rolling down a ramp. It carries a human passenger whose identity is no longer known. "

http://en.wikipedia.org/wiki/Félix_du_Temple_de_la_Croix

 

Lensman:

Nor do I think that "high temperature fusion" is a synonym for "steam powered" propulsion. Many people would get the analogy between water vapor and metal vapor. Who would get an analogy between "steam" and "high temperature fusion"?

I am sorry to be the one to break the news to you, but your understanding of ion drive seems to based upon dictionary definitions as was your unwarranted criticism of my metal vapor/steam analogy. Ion drives are much more varied than what you seem to understand.

You really cannot be taken seriously as someone who would be able to factually and constructively discuss physics.

 

Thank you for your highly entertaining post, Cangas. I especially liked the unintentional irony of your last sentence.

 

Glad to help you out, L.

The way out is straight down the hall and through the door marked EXIT.

 

But to return to the subject of low-tech space drive, Jerry Pournelle's science fiction novel A Spaceship for the King (republished as King David's Spaceship) describes a method of achieving orbit using gunpowder for propulsion. I don't remember the details; I don't care much for Pournelle's fiction and have forgotten it.

 

The subject is, according to the thread start, for the benefit of the reading disadvantaged, "steam powered flight".

STEAM POWERED FLIGHT.