Fusion Ramjet

H

Hevene

Registered Senior Member
This could be the answer to interstellar travel - the hypothetical ramject fusion engine. Hypothetical, because the proton-proton fusion process is not yet mastered, but the ramjects do not violate any known law of physics.
The design was originally proposed in 1960 by Robert Bussard who estimated that starship weighing 1,000 tons could accelerate at one g. This creates artificial gravity comparable to the earth's. The fusion ramjet sucks in hudrogen from deep space in its tunnel as it travels through space as its fuel. The starship is light weight because it does not require stored fuel and it can approach the speed of light within a year. This allows the people to reach the Pleiades star cluster (M45) in eleven years, the Great Andromeda Galaxy in 25 years (though long time had been passed on Earth - according to Einstein's special theory of relativity).
If only we could solve the problems on fusion as it's much more difficult to attin thean standard deuterium-tritium fusion process in the prototype fusion machines on Earth. But with our increasing understanding, the ramjet may prove to be a very viable possiblility over the decades.
 
The question then would be, do we really want to spend unimaginable amounts of money to fund such a mission. As you have said, although only 25 years goes by for the astronaughts, much more time will pass here on Earth. I'm sure that with another century of research after fusion is perfected a way to travel FTL will be discovered. Do we really want to fund such an undertaking as travelling to another star now when we can simply wait another century until we can travel there in a fraction of the time?

Also, Andromeda could not be reached in 25 years at near light speed. It would take more than 2 million years to reach it if the starship was travelling at very close to light speed. Although Alpha Centauri may be a better target, as it will only take 3 years.
 
It might not be the best thing, but nontheless a possibility and within reach. Unlike wormholes, still hard to achieve. So if we are in a hurry to explore, it's not a bad idea.
 
Who cares how much time passes on earth. If the first expidetion goes smothly we will keep trying to devolp it back on earth.

If we make somthing that goes faster, we can just get ahead of the first ship and take them back or bring them along.

This would take care of the long trip time, IE 25yrs from here to there.

If you leave earth at NLS, by the time your gone a month 20yrs will have passed on earth and there bound to have made something that goes faster.

You chould leap frog across time and space in no time at all.

So in theroy just leave now and wait for the "tech" to get where you are.
 
One of the things that I have a hard time grasping is the strength and size of the collector field for the Brussard Ram Engine. This thing requires an immense field of considerable strength the funnel these hydrogren atoms into the collector. I am certain at present that we do not yet have the ability to build such a field. Large parts of the needed understanding is still under study at assorted particle accelators around the world. Some of what we have yet to grasp is in particle physics. Getting the ship up to collector speed is another problem. There is a basic minimum speed required for it to begin collecting. Before that speed is reached there is not enough collecting going on to sustain engine fuel collection to use balance. Prehaps they could use some type of pulse iginition during the initial start until the ship is up to operating speed.

Subjective time passed during the voyage is of concern to those who launched the mission and want to know if what they sent out was successful. It is hard for me to imagine that anyone would fund such a project as there would be no hope of finding out if they were successful and if they made it within our lifetimes for any reasonable trip with a hope of finding a habital planet. While I would love to see such a trip I just have these nagging doubts about it ever being done without there being some kind of calamity to give us the drive to do it.
 
I reckon Bussard collectors are a long way off, pretty much for the reasons wet1 outlined. The field would have to be on the order of kilometres wide, and hope that there's enough interstellar hydrogen to do the trick.
Subjective time passed during the voyage is of concern to those who launched the mission
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Especially as you approach c. I've a wee calculator on my web page ( http://robertelliott.org/science/planets ) that illustrates time dilation. Compare .9c to .99c to .999c... it's a remarkable difference.
 
One questionI have always had about the Bussard Ramjet is what happens to all of those freely floating particles in space, such as microscopic pieces of iron ore from asteroids, that are caught in the fields? They would be funneled to the combustion point, but would they function as fuel?

Also, what do you do about avoiding even microscopic pieces of matter when you are travelling even at 50% of the speed of light? Impact with even a microscopic asteroid or meteor fragment would potentially destroy the craft when it was traveling at 50% of the speed of light.
 
Good question. May be they can build a shield that is strong enough for smaller particals. Bigger fragments may be avoided with automatic nevagation system or something like that. We sure don't want to end up with a hole in the spaceships that costs millions to build.
 
One questionI have always had about the Bussard Ramjet is what happens to all of those freely floating particles in space, such as microscopic pieces of iron ore from asteroids, that are caught in the fields? They would be funneled to the combustion point, but would they function as fuel?
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A ramjet wouldn't be a big funnel; that'd be impractical given the fact that it would have to be on the order of kilometres in extent. It's more likely to take the form of a field that redirects sufficiently small particles into a collector. Chunkier particles would be too massive to be affected.
 
rde ...

Which still leaves, IMHO, two problems:

1) Particles too 'chunky' to be deflected and impact;

2) Particles just 'chunky' enough, and in line enough
with the 'collector', to be scooped up.

What say?
 
Any problems encountered with the ramjet would be problems encountered by the ship as a whole. Given the nature of any ramjet, it'd - theoretically - be possible to have a big shield on the front of the ship that'd shield against any particles too small to be avoided. A non-straight magnetic (or whatever) tunnel in this shield for herding collected particles could ensure that a gap in the shield wouldn't prove fatal.

Did that make any sense?
 
rde ...

Hadn't considered a 'non-straight' entrance to be honest.

Guess I'm hung up on the idea of a ramjet being linear ... including the 'scoop'.

Take care.
 
Antimatter would be a much more efficient way of propulsion. Just one half kilogram of matter, reacted with one half kilogram antimatter, yeilds 1x10^16 J of energy. This is equivalant to a 2.4 Megaton nuclear weapon exploding (or 2,400,000 times as powerful as TNT).

The key will be storing the antimatter and controlling the reaction. The reaction would have to be performed using only a few molecules at a time. However, even 50 kilograms each of matter and antimatter would yeild 4.5x10^18 J, or about 1100 Megatons of energy. The largest nuclear weapon ever developed was 100 megatons.

Matter/Antimatter reactions are 100% efficient. Nothing is more efficient (that we can grasp) because enegy cannot be created. More focus should be diverted to antimatter research because it can be considered to be the pinnacle of energy "creation" devices such as power plants. But, I wouldn't want to be around if countries decide to start building antimatter weapons...
 
Antimatter is only efficient if it's cheap to produce. In terms of energy output, yeah, it's great, but fifty kg of the stuff at the moment - and for the forseeable future - would be prohibitively expensive.

Not, you understand, that I'm suggesting that buzzard ramjets are whizzing of the production lines as we speak.
 
If the only thing keeping us from exploring the stars is money then our society needs to rethink it's goals. I'm sure if the 343 billion or so dollars the US spends on the military each year were thrown into antimatter research and production for just one year, we'd have enough of the stuff to power a starship and much more left for research purposes. But, I guess we'd rather squander that money on weapons of war and kill eachother off with them. It is a shame though...

Oh, and a correction on my previous post. The energy released from 50kg of matter and 50kg of antimatter would actually be equal to 9x10^18 J, or about 2150 megatons. That's enough energy to light a 100W lightbulb for 2,853,881,279 years.
 
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Originally posted by Xelios
If the only thing keeping us from exploring the stars is money then our society needs to rethink it's goals.
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You're only realising this now?
I'm sure if the 343 billion or so dollars the US spends on the military each year were thrown into antimatter research and production for just one year, we'd have enough of the stuff to power a starship and much more left for research purposes.
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Listening to Bill Hicks?
 
Antimatter would solve the energy problem but there is a problem with this at the present. World production of antimatter is on the order of micrograms. Far less than what would be required for any meaningful use as a propellant. The next thing is that the only way we have found to contain it is to use force and not material, such as a "magnetic bottle". For use as a propellant the "magnetic bottle" would need to be orders of magnitude larger, requiring a sizeable powerplant to supply containment force. A containment force that can never be turned off as long as it is needed to contain the antimatter. Should the power be cut off to the containment field then you have a recipe for disaster. Ideally, it would be better to make it as you need it and not store it for future use. The only problem with that is that you need to power an on-site particle accelerator requiring far more in the line of energy than would be practical to carry with you. If you have that kind of power to tote along then moving the mass is going to be another problem. So far there seems to be no answer to that. There has been some looking into the idea of mixing antimatter with nuclear to achieve a boost to the nuclear energy over what we now can do with straight nuclear energy. That seems promising on a small scale.
 
Hello all...

I am doing research on the brussard ramjet for a university physics class. I found a paper online called Self-Replicating probes for galactic exploration, and it lists at least 5 references on the topic -but google can't find any of them.

It seamed to me like you folks know a bit about it, and may have access to Brussard's original paper... Could you let me know where to find it?

I admit... i'm being very lazy... I could just go to the library and ask professionals :)
Perhaps I could post some of my findings here in the future ;)


As for antimater, you could not use it exclusively for power on earth. Anything that has to be produced can only be used as a storage device.
 
Well, I like the fusion ramjet vs. antimatter drive question, and I favor the fusion ramjet, because of simple problems of economics. Since the 1950s, CMIIW, Fermi Labs has been producing antimatter, and we only have a few micrograms of it to show for all the trouble. Unless we find a more efficiant way of producing antimatter, the only method is to make huge, orbital accellerators, or even simply earth-based ones, miles long. The fusion ramjet is more economic, but there is a problem. Exactly how many hydrogen molecules per every 1000 cube k. in space are there? If anybody knows, I would be very intrested. I am wondering if it would simply not be more economical to just carry more hydrogen?
I have an idea that may prove better, and more economical. What if we took the concept of a high-G simulator (an arm with a capsule on the end of it, rotating very fast), and made the capsule a fusion-ramjet equipped ship, that can detach when it reaches critical velocity? This whole mass accellerator would be space-based, of course. The main hub would be super-dense, so the ship would rotate around the hub, holding on to the end of the arm with electromagnets. The hub would be turningwith the aid of huge liquid-fuel engines, so the ship on the end of the arm would have massive kinetic energy behind it, along with its own fusion ramjet. What do you think?
 
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