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NASA Antimatter Spaceship


trekkie_

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That was a pretty cool article. I had kinda wondered exactly how antimatter would be generated. It's still iffy as to how you'd store it.

While this certainly sound viable, it does raise questions.

1) 'within electric and mag fields' is pretty vague. I should think you'd need some pretty stiff power requirments to generate those and that means mass. Sure the 'fuel' only weighs 10mg, but the containment may well weight a whole lot more. From a mod perspective, I suppose what you'd have is a tank with a relativly high base mass to account for structure, permanent magnets and electrical generation equipment. One supposes you might use a generator module to consume miniscule amounts of the the AMFuel to power said containment. Otherwise any brown out or black out would doom the ship.

2) Minimum thrust. While I'm sure you could throttle it, I suspect even the most precise 'valves' for AM would produce quite a bit of thrust. ModuleEngine (sp?) has a min thrust variable but i've never seen it set to anything but 0. You'd likely have to action group the engine's toggle property to actually throttle down to 0.

3) Correct me if I'm wrong but isn't the size of the engine bell (not the shape) related to the amount of thrust it can support with coming apart. I know the shape relates to the ISP (short wide for atmo, long narrow for vac). But the bigger the bell, the more thrust it can take. I see those little bitty bells on the model and I'm thinking you may want to make em bigger. Just saying :) Of course I could be all wet if the whole ship doesn't weigh as much as it looks.

Actually, it occurs to me, since the AMFuel is beamed into (or focused on) the diffusion matrix would the engine have a single matrix that pipes the exhust to multiple bells or would it just be one larger bell?

Surely you wouldn't want to have multiple matrixes, focus emiters and whatnot? Does that make any sense?

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The antimatter is stored at low temperatures, in a vacuum with incredibly powerful magnetic fields preventing it from touching the walls of the containment unit. This is not the perfect system, but it's the best we have.

1) Yes, pretty much. But then again, most planned deep-space exploration craft have a small nuclear generator on them, so power is pretty much a non-issue. Not to mention, the energy stored in the antimatter could be harvested. While no, that does not make antimatter an energy source (but rather an energy transfer mechanism), it could potentially be used in such a manner.

2) The thrust is regulated by how much propellant is released into the reaction core, not by the antimatter fuel, so it could be easily throttleable by a regular (if incredibly heat-resistant) valve.

3)Yes. The rigidity of the bell is more or less dictated by the material, but the bell is constantly heated up by the incredibly hot propellant coming out of the exhaust, so the bigger the nozzle, the bigger the surface to heat up. The nozzle is, however, cooled by the liquid fuel pasing through the nozzle, so potentially, it could be done so small, but it'd be a safer bet to go with a bigger one.

Having multiple AM matrixes means more places where things can go wrong, which means more work for the flight engineers.

Having one AM matrix spread into three nozzles is inefficient, as some thrust is lost along the way (granted, it is a small amount, but thrust is thrust).

So, yes, having just one AM matrix with one nozzle would probably be best, but I don't know how much maintenance an AM engine would require, so it is entirely possible that having three and have some more thrust would be a good way. But only if the maintenance required is minimal.

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oh then please explain it for us all ;)

I see you need to learn sarcasm :P

The thing about teasers is that they often imply something through use of objects and symbolism already known to the people interested in such a creation. A good example is this:

It does not tell much about what game is all about, it mentions that it is an Elder Scrolls game, its location (Skyrim) and the dragons and the dragonborn are intoduced. You don't know much about them, but you see enough to know the next game will probably be set in the land Skyrim and will involve dragons and a dragonborn. It deals a few solid hints on the storyline, but does not reveal all of it, nor does it introduce the fine mechanics of ES V.

A bad way to tease at such a game would be an image with the dovahkiin helmet on a plain white background (without an indicative name) and a link to an article about the helmet (and ONLY about the helmet). You don't know what it is, you just know it's a helmet and that the site the link took you to does not tell you whether it is an add-on for the existing game (Horse armour, anyone?) or if it is a hint at a new game.

Now, a good way to hint at this addition to KSP would be to upload a 3D image of the model being worked on (using the in-built viewer) or the picture of it in Kerbin orbit (possibly in the shadows, so that the only thing one is able to make out is its shape and the fact that the planet it is orbiting is, in fact, Kerbin), or hell, even writing "Teaser:" above it in order to give the audience a hint as to what the purpose of said image. Now, for the image itself: the image you posted in your original post looks like it's been ripped from some presentation of the craft and stuck under the link to the article, and the lack of any additional detail explaining what the image is and what the purpose of this thread is just leaves the viewer baffled rather than excited at the prospect of such an addition to the game.

Tl;dr: The presentation is lacking the most basic things a teaser needs: giving the audience a clear clue about what the product is, but still leaving them in the dark about the fine details of it. The way it is now, it just looks like a fan of the article posted a link and an image of the craft shown from multiple angles.

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Breaks out the fire extinguisher :P Ehem! Back to the subject

The antimatter is stored at low temperatures, in a vacuum with incredibly powerful magnetic fields preventing it from touching the walls of the containment unit. This is not the perfect system, but it's the best we have.

1) Yes, pretty much. But then again, most planned deep-space exploration craft have a small nuclear generator on them, so power is pretty much a non-issue. Not to mention, the energy stored in the antimatter could be harvested. While no, that does not make antimatter an energy source (but rather an energy transfer mechanism), it could potentially be used in such a manner.

2) The thrust is regulated by how much propellant is released into the reaction core, not by the antimatter fuel, so it could be easily throttleable by a regular (if incredibly heat-resistant) valve.

3)Yes. The rigidity of the bell is more or less dictated by the material, but the bell is constantly heated up by the incredibly hot propellant coming out of the exhaust, so the bigger the nozzle, the bigger the surface to heat up. The nozzle is, however, cooled by the liquid fuel pasing through the nozzle, so potentially, it could be done so small, but it'd be a safer bet to go with a bigger one.

Having multiple AM matrixes means more places where things can go wrong, which means more work for the flight engineers.

Having one AM matrix spread into three nozzles is inefficient, as some thrust is lost along the way (granted, it is a small amount, but thrust is thrust).

So, yes, having just one AM matrix with one nozzle would probably be best, but I don't know how much maintenance an AM engine would require, so it is entirely possible that having three and have some more thrust would be a good way. But only if the maintenance required is minimal.

Actually, I was talking about the structural strength of the bell itself. To produce thrust downward, there has to be pressure. For a give size bell, how much pressure can the structure take before the risk of structural failure gets to high? How much thrust does that produce. Logically, the bigger the bell, the larger the max thrust rating should be, yes? Or... is the bell generally so over engineered that a bell failure is rarely a consideration as other components are more likely to fail first?

By throttle I meant how the AMFuel was released into the reaction core. This would be some sort of magnetic valve. How precise can such a valve be? Since a ludicrously small amount of AMFuel will generate a lot of heat a minimum thrust requirement may be needed to keep the reaction core pressure from causing a catastrophic failure.

And on that same thought, I imagine a setup like that will suffer the same problems a NERVA suffers from. You're overall thrust is limited by the materials you make the core from. NERVAs could get hotter but the cores would melt. I suspect an AM engine will likely be a low thrust, high ISP, low TWR engine much like NERVAs for many of the same reasons.

Advantages might be safety as outlined in the article as well as higher ISP and better TWR due to lighter materials. I think Fast Neutron radiation in a fission core needs the heavier materials which have lower heat tolerances. Low Gamma from a AM reaction core might be less arduous.

Another advantage would likely be it's instant on, instant off capability. NERVA's IRRC are pretty much always on. In fact, they probably should have there emisives reversed since fuel flow acts as a coolant. So the core should glow when it's not running and not glow while it is running. With AM, the fuel is either in storage or being beamed into the reaction core.

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Breaks out the fire extinguisher :P Ehem! Back to the subject

There is no need for it, I was only dealing criticism. :P

Actually, I was talking about the structural strength of the bell itself. To produce thrust downward, there has to be pressure. For a give size bell, how much pressure can the structure take before the risk of structural failure gets to high? How much thrust does that produce. Logically, the bigger the bell, the larger the max thrust rating should be, yes? Or... is the bell generally so over engineered that a bell failure is rarely a consideration as other components are more likely to fail first?
No, the thrust would always be the same. It is more relient on the reaction itself, rather than the size of the bell. The only thing a bigger bell would do would be that it'd decrease efficiency (so long as we're talking about a conventional bell). Consult this image:

strictnozzle.jpg

The reason why the bells are so big is so that the cooling is more efficient, not because the thrust is larger. The stronger the engine, the more heat the reaction produces, the bigger the bell has to be. Unless we have massive heat radiators to divert the heat, but most chemical engines don't need those as their in-built cooling is functional enough.

As far as the technical complications: the bell is relatively simple, it's a bell shape with liquid propellant running through the little tubes embedded in it, cooling it down. Bells rarely break down, but if they do, it's usually very bad, because the propellant flow to the reaction chamber is cut off.

By throttle I meant how the AMFuel was released into the reaction core. This would be some sort of magnetic valve. How precise can such a valve be? Since a ludicrously small amount of AMFuel will generate a lot of heat a minimum thrust requirement may be needed to keep the reaction core pressure from causing a catastrophic failure.

In most designs, the throttle is dictated by the amount of propellant released into the reaction chamber. That is because such a method is the easiest to control and throttle. However, the release of AM into the reaction chamber (in an "gas/plasma core" engine, which is propelled by liquid hydrogen/water (and a lot of it) made into superheated gas/plasma through contact with microscopic amount of antimatter in the reaction core) is quite a problematic feat, hard to control and it would be easy to introduce too big amount of AM, resulting in structural damage to the reaction chamber. A lot of engineering and testing would need to be done in this sort of engine.

Things are a bit easier with a solid core, which works the same way a NERVA does (the AM does not come into direct contact with the propellant, as its energy is released and the resulting heat is transferred to the tungsten surrounding the core, which then comes in contact with the propellant, heating it up), making antimatter dosage a much lesser problem.

If we're talking about a matter-antimatter engine, where the ship is propelled by the particles produced when antimatter collides with equal amount of matter, we have the same problem with introducing the antimatter to the reaction. However, the amount of gamma radiation produced by such a reaction is far higher than the previous two engines, not to mention the engineering feat of building a reaction core which could withstand constant detonations of antimatter within (although there are some very interesting proposals using magnetic nozzles). Also, this is the type of engine with little to no control over thrust unless the machinery used to introduce antimatter and matter into the reaction core is very complicated.

Consult this for more information.

And on that same thought, I imagine a setup like that will suffer the same problems a NERVA suffers from. You're overall thrust is limited by the materials you make the core from. NERVAs could get hotter but the cores would melt. I suspect an AM engine will likely be a low thrust, high ISP, low TWR engine much like NERVAs for many of the same reasons.

Very true, but TWR only matters on planetary take-off and landing, and most uses for an AM engine are in deep space. The part about overheating is also correct and will either take new materials, able to withstand incredible temperatures to build the core out of or constant vigil from the technicians.

Advantages might be safety as outlined in the article as well as higher ISP and better TWR due to lighter materials. I think Fast Neutron radiation in a fission core needs the heavier materials which have lower heat tolerances. Low Gamma from a AM reaction core might be less arduous.

Eh, a shadow shield or two should take care of the neutrons and the radiation. Also distance, you want your crew to be as far away from that thing as possible. :wink:
Another advantage would likely be it's instant on, instant off capability. NERVA's IRRC are pretty much always on. In fact, they probably should have there emisives reversed since fuel flow acts as a coolant. So the core should glow when it's not running and not glow while it is running. With AM, the fuel is either in storage or being beamed into the reaction core.

Also true and one of the main reasons why antimatter engines are such an interesting topic for aerospace engineers concerned with human spaceflight. :D

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I'd say that the limiting factor in thrust rating is more likely to be temperature and pressure resistance of the combustion chamber. A large bell can capture more enegy from the exhaust and produce more thrust, but that thrust comes from the expansion of extremely hot/high pressure gases from the chamber, which by the time they come in contact with the bell are at much lower temperatures and pressures. The bell transmits some of the thrust and so takes some of the rocket's weight, the combustion chamber is subject to far greater forces pushing outwards on all sides and is the highest temperature part of the engine. Its also what the bell is attached to and all the force coming from the bell goes through it anyway.

To increase the thrust of an engine you need a greater mass flow - this means you either want more propellant coming out of the nozzle, or you want it to come out of the nozzle faster - both of these entail bigger, hotter, higher pressure combustion chambers.

Given the types of engine that have been built, it seems that taking the actual force - at the nozzle or gimbal or wherever - is arbitrarily easy (just add moar struts), whereas engine power (or at least, power-to-weight) has been steadily increasing as new high-temperature materials are developed.

...IMO

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I'd say that the limiting factor in thrust rating is more likely to be temperature and pressure resistance of the combustion chamber. A large bell can capture more enegy from the exhaust and produce more thrust, but that thrust comes from the expansion of extremely hot/high pressure gases from the chamber, which by the time they come in contact with the bell are at much lower temperatures and pressures. The bell transmits some of the thrust and so takes some of the rocket's weight, the combustion chamber is subject to far greater forces pushing outwards on all sides and is the highest temperature part of the engine. Its also what the bell is attached to and all the force coming from the bell goes through it anyway.

To increase the thrust of an engine you need a greater mass flow - this means you either want more propellant coming out of the nozzle, or you want it to come out of the nozzle faster - both of these entail bigger, hotter, higher pressure combustion chambers.

Given the types of engine that have been built, it seems that taking the actual force - at the nozzle or gimbal or wherever - is arbitrarily easy (just add moar struts), whereas engine power (or at least, power-to-weight) has been steadily increasing as new high-temperature materials are developed.

...IMO

Exactly. Except for the "bigger nozzle = bigger thrust" correlation in the beginning. The proper correlation is "more powerful reaction = more thrust = more heat = bigger nozzle", as you rightly pointed out in the later parts of your post. :D

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Wow, Krev, that was a comprehensive response. Much appreciated!

Yeah, after I posted I went and started googling nozzle design and couldn't find any mention of a relation of thrust to size. All they seem to talk about is shape as it relates to efficiency.

A thought occurs to me though. If we have EM containment on fuel storage, could we not have containment on the reactor core? I'm kindof envisioning a toroidal core envisioned by some fusion reactor designs. Or would that just get unworkably big?

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It depends on the design of your engine, there are certainly some hypothetical designs for EM nozzles. The toroid designs being used for fusion research at the moment are good for containing plasma, but there are issues with getting the plasma out of the torus without compromising containment, I'd imagine that this might place a choke on an engine designed this way - although that is pure conjecture on my part.

Your engine certainly doesn't have to be able to survive the temperatures reached by your propellant, there are all sorts of methods by which you can prevent hot propellant from contacting engine components, or actively cooling them. Even some current jet engine designs would have some components start to melt if they weren't actively cooled.

The "Nuclear Lightbulb" designs offer some inspiration here, since the nuclear core is already in a vapourised state.

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I think it's important to consider that an antimatter fueled vessel would still be very much lighter than a NERVA, while providing far more power. One of the options includes a material that either deflects gamma rays or is ablated by the gamma rays from the antimatter reaction and used as propulsion. This thing is designed to reach mars fairly quick, but given its potential reduction in weight, even a lower than conventional thrust would produce greater speeds, and with ISP's as high as 9000 predicted, you can reach even greater speeds from longer burns.

Even inefficiencies in bell design, can be negated by overall efficiency. Even simple cone shapes were inefficient -- but we used them for some time, and they worked.

When people think antimatter, they think tapping enormous amounts of power, when really all we need to tap is just a fraction of that power to create greater efficiency than previous rockets. Therefore, we can still use antimatter inefficiently and see gains. antimatter is not an 'extract all power or it's not worth it' proposition.

Just think, if we get to the point where we can create an entire mars mission's worth of antimatter fuel in just an hour, we could create abundant energy on earth. we could create vessels that can produce their own antimatter and replenish their own propellants, if external propellants are even needed at all. Positrons are especially of interest because they give off far less deadly radiation, making it more practical to use on earth as a fuel source.

Perhaps they realized that creating larger bells to cool, was simply impractical. If you look at the pictures in the article, the exhaust on this thing is showed to be a wide jet. There could be tons of factors why they've made certain design decisions. Then again, if NASA ever builds a vessel it could look entirely different, after all it's just a concept design.

Edited by trekkie_
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Just think, if we get to the point where we can create an entire mars mission's worth of antimatter fuel in just an hour, we could create abundant energy on earth. we could create vessels that can produce their own antimatter and replenish their own propellants, if external propellants are even needed at all. Positrons are especially of interest because they give off far less deadly radiation, making it more practical to use on earth as a fuel source.

Antimatter is a very bad energry source, since it requires an amount of energy to create antimatter, which is then released in the reaction. However, if we did have the capability to create enough AM to fuel an entire mission's worth in just an hour (which is very optimistic, if you ask me), we would've already had a massive enough infrastructure to supply that power, so I can see how it can be related to abundant energy.

A vessel will always require propellants, because spacecraft operate on Newton's 3rd Law. The fuel is what starts the reaction and the propellant is what propels the spacecraft forward, so even in a Matter-Antimatter engine, a certain amount of matter is required to propel the spacecraft. Also, an Matter-Antimatter engine would be very low thrust unless we can find a way to contain much larger explosions of antimatter and matter, and find a way to negate the gamma radiation released from such an explosion. Not to mention that the only way to replentish propellant mid-flight is either by having a Bussard Ramjet and travelling at relativistic velocities or by having a mining probe and using that to mine water/matter from the solar system.

I doubt that any vessel will trudge around with a Particle Collider, because those require massive amounts of electricity and weigh quite a lot. However, they could be placed in orbit around a planet near the sun where they could be powered only by photovoltaic panels, but that is very unlikely so for most part, the antimatter will be supplied from earth's surface for quite a while.

As far as positrons go: Sure, but since they do not produce so much radiation, they will most likely be used in either solid core or gas/plasma core engines, rather than Ablative/Matter-Antimatter engines.

Perhaps they realized that creating larger bells to cool, was simply impractical. If you look at the pictures in the article, the exhaust on this thing is showed to be a wide jet. There could be tons of factors why they've made certain design decisions. Then again, if NASA ever builds a vessel it could look entirely different, after all it's just a concept design.

Very true, but all that heat has to go somewhere, so I wouldn't dismiss the option of having heat radiators. However, this IS only a concept, as you rightly point out, so nobody really knows what the final product will look like.

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I think KSPI uses the premis of collecting AM particles that get trapped by a planets van-allen belts. Their science labs can produce small amounts but the bulk would be harvested.

Yeah, but that's silly and in reality, the only natural "deposit" of AM is guessed to be close to the center of our galaxy.

So this method is perfect for KSP! :D

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