Real sci-fi space ships coming at last? NASA tests nuclear engine NASA has conducted tests of a nuclear reactor intended to generate electricity in space for the first time since 1965, offering hope that humanity may now belatedly get serious about building proper, powerful spaceships of the sort long envisaged in science fiction. The space agency has just announced the tests, conducted by …
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Oh, and violate the Law of Conservation of Energy? Where does the energy come from?
Anyway, the DUFF doesn't answer one very important question, and one which has likely stymied all non-chemical rockets for decades: What are you gonna use for reaction mass? To date, we've yet to develop anything resembling sci-fi's pure-energy propulsion, as there remains the infamous "underpants gnomes" step (IOW, ?????). How do you convert the electrical energy into kinetic energy? The only we know how is electromagnetic propulsion, and THAT requires a reaction mass. Furthermore, if Newton has anything to say about, it's gonna either a lot of mass OR a lot of energy (probably somewhere in between) to accelerate and decelerate a manned spacecraft to and from any reasonable fraction of c.
i said it all a million times,.
6mw from 20 rpm = 300,000 watts from every full rotation when a dynamo is at maximum output, a electric motor will not use 300,000 watts to power it as watts = electro magnetic calibration, the everyday common motor is either
high RPM and low torque or low RPM and high torque, to turn a dynamo is low RPM and low torque with a motor calibrated specific to the dynamo
you just use a solar battery cell to start them up or the national grid
im a looser and dont have £1000 for a 1+ kw wind turbine with full battery and transformer, and a good regulator to control the watts to the motor that is not made for its use you get from a industrial electricians shops made for a factor machine or power drill
the input watts to the dynamos battery is that of the RPM output, you just loop back in a primitive setup 90 watts, and have the rest being stored in the battery on every full rotation
if you have 300,000 watts from every full dynamo rotation, and the motor used 1kw for every of its RPM, you still have 299,000 watts to power the battery or full circuit grid
if you want to power a spaceship, you just need your everyday domestic wind turbine kit you will have in your loft, and a power drill motor to turn the direct drive dynamo instead of the wind, a power drill motor has plenty of extra RPM and torque then you actually need and can give you a constant 10kw with ease
if you put it all in a cylinder, the battery just becomes a battery cell, you can replace and charge up using solar power, and can power mars and every thing else
you can make find farms worth while, or just make massive turbines the size of houses, its all just math, AC and volts, once you know the torque the dynamo needs at its maximum output RPM
the space shuttle size craft would only need 10kw, if you want a settlement on mars you can happily start off with 1 or 2 MW, for lights of planets, and making oxygen if a good source of water is found like nuclear submarines
domestic kits include the wind turbine, that generates the electric, the electric gets stored in a battery, the electric stored in the battery goes through a transformer, before it reaches you house circuit for your green power use
you can put it all in a 2 litre trash can size cylinder, if you have a motor on top driving the direct drive dynamo
ZModem.
I think I see where you're coming from, but it's utterly wrong. You've seen a 2MW generator and thought "hey, if I spin that shaft I'll get 2MW!" then thought "Hey, you know what spins really well? An electric motor."
Unfortunately the electric motor will have to put more than 2MW of power into the dynamo to get 2MW of power from it. This is because as you spin the rotor of the dynamo the resistance to movement builds up more and more; spinning the dynamo shaft inside the coils of the dynamo creates a magnetic field which acts against the motor you're using to drive the dynamo shaft. You can't get rid of this field; it is this magnetic field growing and collapsing that pushes the electrons through the wire and so creates an electrical current.The faster you spin it the more resistance there is.
If you think you can do it, build a smaller model. Even a model that produces no excess power but spins itself forever would be worth approximately all of the money in the world. You would become an overnight billionaire, worth substantially more than the oil companies who'd really not like you (but to whom you would pose little immediate threat). Maplin or RS (or even eBay!) would be able to provide you with an appropriate motor, dynamo and other components to give it a go.
electric motors do not have shaft power and why they are the only kind of motor that can turn massive axles, and why aircraft carriers need to be nuclear, while all other ships use diesle generators
the input watt powers the electro magnets, the calibration while depend on what
the motors RPM and torque is
"you can generate a constant 10kw using a 12v powerdrill motor with RPM and torque spare if passed through and controlled with your regulator"*
Are you:
a) Eight years old.
b) On drugs.
c) From a differnet universe that doesn't have a "conservation of energy" law.
Please study some basic physics and then come back and apologise.
* If your 12V motor is running at 834 Amps and your generator is 99.99% efficient then you *can* generate 10KW but you use 10.0008 KW to do it; a net loss of 0.0008 KW. Ye canna' change the laws of physics!
there are no laws of physics, different dynamos generate different ac/dc and volts, if your a professional electrician or make nuclear reactors or have a general understanding of modern dynamos and know why they cost £5000 instead of £8 for bike lights and radios, you can probaly make a crude generator in a hour
when you put some extra money in and make motor specific to the dynamo, they can power ships and planes and national grids and spaceships
if you want absolute minimum loss of power looping back to the motor, there is different types of grease and gases to put in a vacuum container cylinder, the math is all the same and none of that matters much if you can generate 10kw with a 12v power drill motor
Thing is, that number gets CLOSE to zero, BUT--and this is the important part--it NEVER REACHES zero. Without that, you can't approach perfect efficiency, and without that, you're going to lose energy, full stop (as efficiency measures that loss--or rather, the preservation of that energy).
Here's another interesting thought: an overunity engine would also by default have NEGATIVE entropy: a physical impossibility.
a small amount of generated power looping back to power the motor and not needing any other fuel besides a start charge from the battery and already able to generate 6 megawatts in 20 turns with a dynamo out of a windfarm turbine is alot more effient then a nuclear reactor with heatpipes and waste that only generates 1kw
How about I puncture your thoughts on electric motors right now?
Electric motors DO produce torque. In fact, ALL rotating shafts have this feature. Torque is a FORCE and fundamental to physics.
Motors CAN be overloaded. Ask yourself why a cable elevator (which is run by an electric motor) has a weight limit? Because if it's too heavy, the elevator motor can't pull the load.
How about something a little more prosaic? Try removing an old rusted stuck screw with your electric screwdriver or drill with a driver bit (the drill is also an electric motor). Guaranteed it won't go easy (if at all--sometimes you overtorque and snap the head off).
"If you think you can do it, build a smaller model. Even a model that produces no excess power but spins itself forever would be worth approximately all of the money in the world. You would become an overnight billionaire, worth substantially more than the oil companies who'd really not like you (but to whom you would pose little immediate threat). Maplin or RS (or even eBay!) would be able to provide you with an appropriate motor, dynamo and other components to give it a go."
Here's a helpful hint. People have already tried this technique. Lookup "Bedini motor" or "overunity engine". I guarantee you will find nothing independently verifiable except failures (because a verifiable success would draw instant international attention).
But terribly inefficient. 2.5kW yields .72N of force at current rates. So the ability to accelerate in vacuum an object about the mass of a fifth of liquor 1 m per second per second. Plus I have to wonder about its usefulness in atmosphere. So, looks like it's back to waiting.
> But terribly inefficient. 2.5kW yields .72N of force at current rates.
Presumably though if you were already going 3km/s and it was still producing .72N, it would be near on 100% efficient?
It's not hard to reach those speeds either, if you're in a vacuum and prepared to wait. A probe en rourte to Pluto was said to be going 22km/s in 2006.
http://www.newscientist.com/article/dn8587-pluto-probe-set-to-break-speed-records.html
Which of course raises the question: How does the efficiency drop off with speed? If there's no mass ejection, it shouldn't?
But then past 3.5km/s it would be >100% efficient?
That alone makes it seem to me like it's not going to work, sadly.
>Just waiting for the next flood of paranoid hippies decrying putting nuclear fuel in space.
Well, that put paid to Project Orion - the idea of launching a vehicle into space by releasing a chain of nuclear bombs behind it- the lid on the coffin was that each launch was estimated to lead to the premature deaths of around ten people due to fallout. Shame really, because one design constraint of Orion is that it had to be big. Really big.
Still hoping someone can crack the Space Elevator, but it seems pesky physical materials don't allow it.
The Stirling Engine needs a thermal gradient to work, like all heat engines, the bigger the gradient the better.
So what is cooling the cold side of the piston? any thermal engine in space is going to be limited by how fast you can radiate heat away since you can't use conduction or convection to move the heat away which would seem to put a fairly hard limit on how big of a power source relative to the surface area avalible for heat radition you can place on the craft.
Assuming power requirements goes up roughly in line with volume (otherwise what are you doing with all that extra space) but the ability to radiate heat goes up in line with surface area, it would seem that there is a limit to the size of craft you could build without cooking everyone/everything inside, especially once you are not actively moving and throwing propellent out the back which can be heated up first as a way to get rid of heat.
Same place it goes with a thermocouple RTG - Those black fin radiator cylinders
*****
But as mentioned in the article, those things are weedy.
According to http://solarsystem.nasa.gov/rps/rtg.cfm the current generation of RTG produce a nominal 110 Watts (it's more at the start of the mission but that is what it's expected for most of it's operating life).
If you try to scale this up you are going to run out of surface area to radiate the heat with. Maybe not with the 1kw battery being discussed in this article but you aren't going to be running the propulsion units of manned space craft like this in the future.
So you weant to take the heat from the cold end of s Stirling Cycle Engine and feed it into a hot exhaust?
Heat cannot of itself pass from one body to a hotter body
Heat won't pass from a cooler to a hotter
You can try it if you like but you'd far better not-a
'Cos the cold in the cooler will get hotter as a rule-a
'Cos the hotter body's heat will pass to the cooler
Got that?
Wait. Can you not use a power source to help transfer the heat to the hotter system? Like a cooling system or a heat exchanger?
While it sounds silly to put the heat into the engines, quite a few planes put heat into he fuel. Then the fuel is of cause burnt for power, and the heat sent out the exhaust. Still have to worry about the heat exchange and tolerance of the engines and fuel system mind, but that's higher than the heat limits of the cockpit. ;)
Simple explanation: yes the current thermal RTGs are weedy at 110W but they are also low efficiency, so say* a pellet gives of 1KW then the Radiators must emit 890W of heat.
If you use a more efficient Stirling Engine it can give out 300w of power from a pellet, but they will only give out 700w of heat, meaning the radiator can actually be smaller.
The pellet source is still outputting 1KW, by being more efficient in conversion you reduce the amount of heat you need to radiate.
Meaning the same size radiators as current thermocouples can cope with a larger heat source on stirling.
*numbers are example only for explanation purposes - not real figures!
They orbited the moon. They also orbited the earth but in the same way that when you orbit the earth you are still orbiting the sun. It we all go round and round.
"Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour
That's orbiting at nineteen miles a second, so it's reckoned
A sun that is the source of all our power"
Peltiers are thermocouples in reverse. Thermocouples are what's being used now for for RTGs.
Individually, they're not particularly powerful (you need LOTS of them - which is what makes a RTG so heavy.)
Stirling engines and thermocouples have a lot of untapped applications on the ground. Clawing back a chunk of the ~60% of thermal energy which is currently tossed overboard in a nuke plant springs to mind as a first thought.
As for space - until costs to orbit come down, anything which is lighter is worth looking at.
"Stirling engines and thermocouples have a lot of untapped applications on the ground. Clawing back a chunk of the ~60% of thermal energy which is currently tossed overboard in a nuke plant springs to mind as a first thought."
Chicken and egg. Power generated < infrastructure cost over life of plant.
The Stirling engine that can handle the coolant flow from a GW sized power plant is not exactly COTS technology. Keep in mind the efficiency will be limited by the temperature difference the system works with. You'd want to stick the Stirling between the outlet coolant flow of the generators and the coolant flow from out side for biggest temperature difference. By then I think it's <100c for water so maybe an 80c temp difference.
Nasa Glenn have been researching free piston strirling engines for a few years now to replace thermocouple RTG's, they are using the same hot fuel pellet as the current thermocouple RTG's and are more efficient, curiosity nearly got the first but testing was not complete in time.
It's interesting to see that they have advanced from a waste pellet to a fissionable reactor.
It's also nice to see old ideas coming back with new methods. And why no one is considering farming all hot waste with many many stirling units is an interesting question.
Power output is constant and controllable. RTGs run down with half-life and are at full power at launch, they even need need to dump heat initially. Total energy is limited only by amount of fuel you can carry.
RTGs are about 5% efficient, a Stirling engine with an infinite cold sink near zero is pretty efficient! It depends on how well you can dump the heat (the design of the radiator) but it should be 10x as good.
NASA have been at work on a next generation RTG using Stirling engines and a Pu package they call the "General Purpose Heat Source."
It looks like they had a few Stirling spare, knocked up a few heat pipes compatible with the reactor and it was game on.
Another site claims this thing was putting out 24W, while the Stirling RTG (misnomer as it does not *have* thermoelectric elements) can push 500W(e), as did the only US reactor the SNAP20.
The SNAP20 used "Peltier" or TE elements with a 1.9% efficiency. Current ones hit about 6% and Stirlings about 24-26% (but with the risk of moving parts). The big benefits of a reactor a)throttling, as unlike an RTG, which starts at maximum and has to be designed to have enough power at the destination to get the job done they can be throttled down in cruise (or even left off till the destination before first switch on) b) A variety of nuclear fuels are possible for the reactor, whereas the GPHS is designed for only one kind of Pu fuel, and its in short supply in the US. Europe seems to be standardising on the stuff found in smoke detectors.
Down side is like all reactors it will need a minimum critical mass which is typically kept low by using highly enriched (70%+ IIRC) or bomb grade fuel.
Good work to get to a nuclear demonstration (not a simulator element) in 6 months and maybe the start of something quite impressive.
You are a smart man!! I work on this project and you for the most part nailed it. This is not a fantastic technical breakthrough, although there were people who thought the reactor-heat-pipe-Stirling combination would not work together a stable system, so yes proof-of-concept was needed. The big value was to show we could do a real nuclear reactor demonstration for short time and relative low cost, and then build from there. It's fun to talk about high performance nuclear rockets and high power for bases on Mars, but we'll never get there without starting small and stepping our way through.
For more info on our approach, go to spacenuke.blogspot.com. I also like how the Register presented the story as compared to many US sites -- Score one for the UK.
"You are a smart man!"
Not a universal view, but I have my moments.
"This is not a fantastic technical breakthrough, "
Perhaps not, but it breaks the "never been done/can't be done" loop. I'm not completely certain that a reactor driven Stirling engine has never been run before but if not then it is the start of the art, Like Whittles W1.
"The big value was to show we could do a real nuclear reactor demonstration for short time and relative low cost, and then build from there. "
The fact this is a live nuclear reactor is very impressive in the timescale, given the much stricter H&S regime that needs to be complied with. Watching some old film of a guy machining a bar of metal in a lath that turned out to be one of the SNAP20 nuclear fuel pins without being in a hot cell was err interesting.
The only additional information I found on another site was that the test was 24w(e). can you confirm this?. I could not find anything on the NASA NTRS server (lots on fission of course but nothing with "flattop" fission) about the programme..
The 100Kw design seems (potentially) to be quite a handy size package which could be dropped into a lot of systems for use pretty much anywhere in the solar system. I'll wish you luck with its development.
The power of this test was indeed only 24 Watts because a) the reactor temperature was limited by existing facility regulations to 300 C (which we can change later) so module efficiency/power was only a small fraction of the flight design and b) it represents one module of an 8 module design The flight concepts we are looking at range from 500 W to 1.5 kW. Frankly, the scientists at NASA don't know what to do with more power than this, it will require a paradigm shift for them. There is some interest in outer solar system nuclear electric propulsion systems from 20 kW to 200 kW (if we can get the mass low enough). The surface power guys are generally looking at 40 to 100 kWe systems, the nice thing here is they aren't as concerned with mass, so we can still go with simple technology. The end goal will be MW class systems to drive large EP systems, like VASIMR.
This experiment has rekindled a lot of interest at NASA, they had lost faith (and rightfully so) that we could do any real reactor testing anymore. This is probably not on NTRS because it was not officially a NASA project, we were able to convince LANL management to put up the cash on our end, and NASA GRC put in in-kind support from their end (providing the Stirling, which probably would have cost us more than our entire budget).
I have a site that steps through my views of nuclear power in space at spacenuke.blogspot.com
"Frankly, the scientists at NASA don't know what to do with more power than this, it will require a paradigm shift for them. "
Yes power is a scarce resource on probes and if this goes ahead the power budget could grow by at least an order of magnitude. It will take time to process that and consider options. I hope people fly sooner rather than later.
"The surface power guys are generally looking at 40 to 100 kWe systems, the nice thing here is they aren't as concerned with mass, so we can still go with simple technology. The end goal will be MW class systems to drive large EP systems, like VASIMR."
My sense is that if it were possible to design a module in the 40Kw range that could be clustered while operating in a range of gravity fields (down to orbital) one basic design could be produced, giving economies of scale. I'd guess the number (or type) of radiators would change depending on where they would be used. A 5 unit cluster could power a VASIMR test unit. If demonstrated that would change the yardstick for round trips to Mars from 18 months to 2 1/2, possibly with substantial effects on viable mission architectures, especially if the payload was big enough to accommodate a single power unit and its associated landing gear.
"This experiment has rekindled a lot of interest at NASA, they had lost faith (and rightfully so) that we could do any real reactor testing anymore. "
I don't think the fact this is a live reactor can be over emphasized. Given the upcoming funding situation I hope you'll be able to establish and maintain some momentum in the effort, both within LANL and NASA.
"I have a site that steps through my views of nuclear power in space at spacenuke.blogspot.com"
I've seen it. I'm not sure if it's my browser security or what but I found a lot of broken links.
BTW Apologies. The US reactor in space was the SNAP 10. I don't think they eve got to a SNAP20.
What about using an "energy amplifier" concept similar to the accelerator driven fission thorium reactor?
Start with a relatively safe isotope with a long half life such as thorium, and run the accelerator from solar energy to "charge up" the core once safely away from Earth to convert the safe stable isotope into the shorter half life fissionable one.
If needed, store energy in an MgB2 based SMES unit that is passively cooled, and charge it up remotely via laser.
Simplez.
Still doesn't solve two problems (BTW, neither does the system in the article). First, you need to be able to release excess heat, and although outer space can be extremely cold, it's also sparse in useable matter for convection or conduction, and there's a limit to the amount of energy you can release to space by radiation (the limits are physical, too, so really no way around them). Second, and more importantly, how do you convert the resultant electrical energy into the actual kinetic energy you need to get moving? Chemical rockets produce their own reaction mass, but electromagnetic propulsion still needs something to "throw" like a hydrogen supply. We're making inroads at pure-energy propulsion, but what's being produced so far is still far too inefficient for prime time.
"Still doesn't solve two problems "
Nor was it meant to
"First, you need to be able to release excess heat,"
In point of fact that is an issue with all space systems. The word I think you're looking for is "coupling" as in coupling the heat being generated to the environment. It's why the Shuttle had 2 big radiators inside it's payload bay doors and the ISS has a big one as well. Without it the crew will literally cook themselves. This shot of the US's only space tested reactor is instructive.
http://en.wikipedia.org/wiki/File:SNAP_10A_Space_Nuclear_Power_Plant.jpg
The black thing at the top of the cone is the reactor. The rest is radiator. Radiator design is a key element of any space system, even communications satellites.
"but electromagnetic propulsion still needs something to "throw" like a hydrogen supply. "
You might like to look up "ion engine"or "Hall thruster" to see what is currently available. The standard propellant is Xenon in high pressure tanks.
"We're making inroads at pure-energy propulsion, but what's being produced so far is still far too inefficient for prime time."
That's a maybe we're making progress. While some results are promising no one is near a fielded system.
"you dont need to release excess heat, you can just circulate it around the hull and interior, and stop the -200c killing people when going further away from the sun"
The -270c temperature applies to object which are in shadow from only major bright objects (like the Sun, Earth etc). In full sunlight outside surfaces are exposed to roughly 1300W/m^2 and the outside surfaces hit +200c.
Any object in space is inside a vacuum flask called the universe. The only way to transfer heat is by radiation. What happens is heat buildup inside an object happens until a) The temperature rises enough for enough heat to be radiated away that it reaches an equilibrium temperature (Stefan Boltzman law) b)The heat producing mechanism can't release any more. In the case of humans that would be when they die of heat stroke, literally boiled in the bag.
A neat description of this can be found in "Have spacesuit will travel" and "The Forever War."
there is`nt much light in intersteller space, any alloy would just freeze and fracture and the craft would space into small peices when the temperatures go below -150c and a grain of dust hits into it
without good heating and my super strength, carbon, titanium mesh, and toughened graphite hull, there is no chance of using todays metals for a hull or chasis without alot of heating
"man thumbs down obviously dont watch the movies and the liquid nitrogen effect and the shock watch that make terminators and guns all explode, there no difference to a metal hull and chasis weilded together"
Oh darn. I only learned my physics and engineering in a classroom, not a cinema.
If you look at where this applies, mostly deep space probes they tend to consist of insulated boxes to keep the electronics around room temperature and the rest of the structure goes to ambient. It's not an issue.
Did you also learn your computer security watching "Swordfish"? I had a friend who was a big film fan and a CS grad. Her comment was "ROTFLMFAO."
insulation means nothing, if there is metal contact to the hull, most probes that dissappear and never make it to mars are usually the ones that hang a sling shot around the moon, the suns radiation wraps around the planets magnetic field so it does`nt matter that much to satalites in orbit
should use carbon fibre reinforced with titanium mesh to stop it flexing to much, then a layer of aerogel, and then toughened graphite for the outlayer you can fix with ease with polymer out the tube, and is padded with the aerogel, before an impact reaches the carbon layer, and all smaller then half a inch thick hull materal
there are 100s of different graphites each with there own properties and conductivity, you can smash your tennis racket onto the concrete floor as hard as you can and not make a scratch, your tennis racket is just cheap commercial toughened graphite, its not hard to shoot with iron balls for a few months in a lab
why, the shuttle heat shield was graphite, its man made and does what its made for, any metal of today would just be passed through with abit of iron debris without 4 inches of lead behind the hull, add a 100 tons of lead and 300 tons of fuel, and its impossible for any normal kind of space travel with todays technology
add a 6mw perpetual generator and a toughened graphite bass hull, and its possible to make a shuttle that can atleast goto the moon and back whenever you like, and only take a few months to get to mars
a rigid toughened graphite hull would`nt last too long without some reinforcement, and to stop more impact damage, the surface needs to flex a little
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