So, in working on a story, I've seen the need to educate myself somewhat in Engineering. I am thinking of a super metal that I will call Xsteel and is roughly ten times stronger than high carbon steel, and about 1/10th the weight. There will also be repulsors that use electricity to produce thrust and using about 40Kw will generate around 60 hp in draw bar thrust.
I've flown several light planes that had around 100 Hp +or- but I have no idea what thrust they produce, and it is probably not linear when compared to speed.
Lastly is a light, cheap, non radioactive power unit that produces around 40Kw, or about what a 200 amp typical American electrical service delivers.
So, I am looking for an Engineering resource where I can get my naive questions answered. In the late 70's I was in a Mechanical Engineering program, but did not finish and that is now more than 40 years ago. Have you any idea how much I have forgotten?
Gwendolyn
Comments
Not an engineer
But, a google fanatic.
http://www.flight-resource.com/PTD/Cessna180-182.pdf This contains some thrust data for propellers.
http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/... MIT paper on the Performance of Propellers (lots of math)
http://www.pponk.com/HTML%20PAGES/propellers.html This is for a 250-275 HP engine roughly.
If you remember the type of airplane, you should try googling it to see if they have the thrust listed anywhere.
I'm no expert, but...
Does it have to be metal? Wouldn't some nano-technology based composite sound cooler? How real does it need to be? I remember reading somewhere that chains of buckminster-fullerene tubes would be 100th of the weight of aluminium cable and carry higher currents.
Do the repulsers work on an electromagnetic principle, pushing against a rail like a linear-induction motor? Or do they work on a jet/rocket propulsion basis? In which case, what are you using for reaction mass? Ionised air or metal ions? Ionised air has the benefit that you don't need to carry it but you need massive amounts of energy to ionise and accelerate the ions. Not too healthy to be around that kind of ionisng energy either. Metal ions have the benefit that the ions are heavier and easier to produce, but you have to carry the metal reaction mass.
I don't think chemical (non-radioactive) energy source would have the energy density you are looking for. All other high-tech esoteric energy sources probably involve subatomic particle physics in some way. Maybe it can be sheilded? Or shunted to another dimension somehow. Heinlein came up with a great Maguffin called a shipstone which would soak up energy without limit and release it as electricity under certain circumstances. He never got into the physics of it, but it got his stories moving. The Stargate tv series did a similar thing with 'zero-point energy modules'. I think (but I'm no expert) over-explaining tech can be the bane of a good story. Star Trek writers apparently wrote the stories and then handed the scripts to some tame scientists with 'insert technobabble here' in the places that needed it. What characteristics are you looking for that are vital to your story? Can you refuel with tap water, gold or the blood of virgin mice? Those choices can completely change the tone of the story.
Wikipedia always seemed to have the formulae I needed, once I figured out the questions I had to answer.
Not really helpful, I guess, I was really just trying to get the conversation going :-)
Thoughtful Comments
Thank you for the thoughtful comments so far. Actually I was attempting to lay the first foundation for a human society that is about to experience the apocalypse. That through some astonishing miracle humans had notched up another evolutionary step, and realized that they needed to do things differently to head off their sure and certain extinction. I do not have a high opinion of humanity in its present state.
Were I the supreme being, I would most certainly terminate you all. Or perhaps he could somehow help certain discoveries to occur to help humanity along?
So, I have felt that if several advances happened very close together, and humanity became aware of their astonishing vulnerability perhaps it could galvanize them to band together, world wide against terminal menace. The whole point of these advances and the insurmountable menace was to get humans to think of something other than war.
Along the way, I was also thinking of conditions like Aspergers as an evolutionary advance, one that would allow the complexities of Orbital Mechanics, and Gravitational calculations to be handled intuitively rather than requiring huge amounts of artificial computational capacity. Also, perhaps things like telepathy could begin to develop.
I have not decided if this bit I am working on will be a prologue, or simply the first chapter, of a larger space exploration opera. I am not sure yet, but I think I may call the entire story, "Captain Brown in Kolob".
Further thoughts
If you are looking at setting your story in the near future, then you might wish to consider the use of fuel cell technology for power generation, and superconductor technology for high efficiency motors (if your scientists have developed room temperature superconductors, even better).
probably not linear
no, the power requirements are a cube function of the speed. (doubling the speed takes 8 times the power) So the Wrights managed with a 15 hp engine, and WWII fighters had 1500 - 2000 HP engines. Propeller design is a true art, and converting all that power to thrust efficiently was a constant challenge for the designers. But with repulsors you can skip that step.
Of course, at the other end of the scale, gliders manage respectable speed with no power, other than during launching.
And with light, cheap, (and presumably small) electrical power units they can be connected in series to provide increased power with no increase in cabling size, so they should scale very well
Gliders ...
... are mostly powered by gravity after the initial launch either by winch or aero-tow and are always descending through the air. They rely on finding air that is rising faster then they are falling either through ridge, thermal or atmospheric wave. The last is the most effective and can result in flights that need the pilot to wear an oxygen mask.
Thrust from propellers is difficult to measure because static thrust measured on the ground isn't necessarily an indication of thrust in the air because the aeroplane is moving forward and unloading the propeller. Certainly propeller design is both art and science as the Wright brothers knew because even water screw design wasn't properly understood in the early 20th century and they built samll wind tunnels to test their airscrews. I suspect there's more science than art these days as I know from my own peripheral involvement with turbofan design.
Just bear in mind that when thrust is equal to or preferably greater than weight then the 'plane can climb vertically. As a pilot of RC model aeroplanes I can tell you that flying a model with an excess of power/thrust can be quite exciting and, occasionally bad for thr wallet :)
It's a rule of thumb that for aerobatic performance you need 100 watts/pound (200 watts/kilo). Never use HP as a unit personally because it's such a vague term and has been used wrongly in the past by motor and motor cycle manufacturers (ie a 1 litre engine was usually decribed as 10 hp in the 1930/40s) but bear in mind that there are 746 watts/hp.
HTH
Robi
Well now that depends.
Well, I do not know what level of believability you're trying to achieve here, but I guess I'll offer what I know. Since you've mentioned that you have some background in Mech Eng, you should already be familiar with some of the things.
We have so many different types of alloys these days, some have truly amazing properties and their properties varies greatly but it is important to remember that "Strength" of materials are measured differently (remember young's modulus). Some steel alloys are extremely flexible but scratch easily, others are hard but brittle and as such Material Engineers tailor materials to suit the requirements of the task.
While your Xsteel probably doesn't exist yet, it's just a matter of more and more advanced fabrication methods until something similar to it is produced. Just like the concept of prestressed reinforcement was patented as early as 1888, we did not have the means of making reliable high tensile steel to employ such construction methods until the 1940s and 50s. So I doubt you'll find any tables or information on such a material in existence. Your best bet is possibly in looking up refinements of metallurgy techniques ie. cooling a cast metal uniformly produces different qualities and strength properties. Modern alloys have their own limitations, so the material you're looking it may likely well be some form of composite, assuming the society you envisioned have the drive and creativity (from what you've described, I thinking of a space race society), then it's likely that the advancements to achieve such feats would be by metalworking and fabrication techniques. Most of what layman calls "space-age" materials tends to be composites anyway.
And you are right in that Horse power doesn't really tell you anything about a vehicle's performance, though draw bar thrust gives you some vague idea and potential. There's always many other factors that needs to be taken into consideration. Dry weight, curb weight, drag coefficient etc. Just look at car engines today, we're getting more performance out of the same range of HP simply by improving the engine and gear designs, not sheer hp output. Don't let anyone tell you otherwise. People obsessed with high HP aren't usually interested in the performance.
I don't know much about how a repulsors might work, but for your "Light, cheap, non radioactive power unit" I think the best bet would be a battery or super capacitor of some sort or a fuel cell especially if you want electrical energy. Batteries and super capacitors makes more sense though, since you bypass the need to convert fuel into energy, it takes away unnecessary parts and weight.
With how far electric batteries and motors have come in recent years (hybrids and electric cars) I think it's possibly safe to assume that in that future, we have batteries or super capacitors capable of doing what you're thinking for extended amount of time and minimal recharge cycles. We're still way far behind in any form of cheap Non-radiactive power unit though. And radioactive power units tend to be heavy because you need shielding. Unless you have cockroach genes spliced. And don't even start on fusion. Shielding for radiation is one thing, shielding for neutrons is another.
Don't have access to Engineering Databases but some links a layperson may find useful
http://www-materials.eng.cam.ac.uk/mpsite/materialsdb/
http://en.wikipedia.org/wiki/Young's_modulus
Strong materials and power sources
Well something is wrong with my browser or with the website, as I can only reply to a post but not create a new one at "top level" :-(
So here goes:
Since the story will obviously be set in the future, some near-realistic SciFi seems OK. Maybe use some composite material with carbon nanotubes, those have a theoretical tensile strength that matches the bill (and gloss over the other kinds of strength ;-).
See http://en.wikipedia.org/wiki/Ultimate_tensile_strength.
For a power source, improved combustion engines are credible enough if only power vs. size and weight counts.
If the fuel consumption would clash with the plot, why not pretend that cold fusion works after all and the scientists finally figured it out?
Why use a metal?
You know I've researched this to from a layman's point of view. My limitations are just what is available on the infernal-net. I think we're conditioned to think of metals as strong. However, new discoveries over the last few years are altering the crystalline structure of metals that give them their strength into a new class called amorphous, or literally glass metal. The structure is more glass like and they are stronger and harder than steel.
http://news.markets247.com/a-new-metal-alloy-has-been-discov...
Another material is aerogels.
http://en.wikipedia.org/wiki/Aerogel and http://ceramics.org/ceramic-tech-today/nasas-new-flexible-an...
Traditional areogels are very light and strong, but also brittle. New research and discoveries are changing all of that. Think of a material that is a great insulator and be used in a jacket, but is strong enough to support the weight of a car.
The above article suggested that it could be used as a inflatable heat shield/reentry vehicle for crew on the ISS. Yes, it is possible for it to be that strong and that good of an insulator. Are we there yet? No, but the possibilities are very tantalizing!
Hopes this helps!
hugs
Grover
Like You, A Diamond of the Water
Diamonds are the hardest material known to humans & comparatively light. Also check out the rare earths elements. Perhaps adding the two will make it stronger.
If you can use si/fi or magic there is a gadget at the Little Kids Kamp universe that uses energy more efficiently. For example if a car does about 30 mpg normally, it would do 240-330 mpg (8-11x) with this device. Then you can easily use a jet engine. Note: it could be used for electricity and other energy situations. No, you can't drink it because it is electronic/magic. Just give LKK the credit.
shalimar
Go back and re-read (or read,
Go back and re-read (or read, if you've never touched it) E.E. "Doc" Smith's Lensman books, plus the DuQuesne/Skylark books.
There you'll have all the jargon you'd like to use, plus a lot of real information (he may have played havoc with the physics, but the _base_ science tended to be sound)
Want something to store energy that isn't a capacitor? An accumulator! :)
I'll get a life when it's proven and substantiated to be better than what I'm currently experiencing.
Carbon nano-tube reinforced polymer (CNRP)
Here you go, an example of the current state of the art in Advanced materials, as used in the F-35 joint strike fighter and several other cutting edge aircraft.